Dissertations / Theses: 'Evaporation processes'

1

Lundberg, Angela. "Interception evaporation : processes and measurement techniques." Doctoral thesis, Luleå tekniska universitet, Geovetenskap och miljöteknik, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-25799.

Full text

Abstract:

In temperate regions, evaporation of water intercepted by the vegetation represents an important part of the evapotranspiration. A review of interception evaporation studies showed that knowledge about interception evaporation processes is limited and progress is hampered by technical difficulties. Existing snow and rain interception measurement methods were reviewed and evaluated with criteria that were established for the ideal method for interception evaporation process studies. No existing methods fulfil all criteria. Two new load-cell based devices for process studies are tested, one weighing-cut-tree technique for snow interception and a technique based on weighing of both net and gross precipitation (with new type of wind-shield) for rain interception. By comparing measured (weighed) and calculated (combination method with different ways to calculate the aerodynamic resistance) evaporation rates for wet intercepted snow it was shown that the most important factors for calculating the evaporation were the relative humidity, the aerodynamic resistance, the wind speed and the intercepted mass. Calculations of evaporation of intercepted snow with a water budget method showed an average evaporation of 0.24 mm/hour and a maximum evaporation of 3.9 mm/7 hours when snow canopy storage was measured with a gamma-ray attenuation system and throughfall with plastic-sheet net-rainfall gauges. Total snow interception evaporation was estimated to be of the order 200 mm/year in Scotland. Comparison with evaporation determined with a combination method (Penman) and two different aerodynamic resistances, the "standard" rain aerodynamic resistance ...
Godkänd; 1996; 20070428 (ysko)

APA, Harvard, Vancouver, ISO, and other styles

2

Vetrano, Maria. "Rainbow thermometry development and application to evaporation and diffusion processes." Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/216588.

Full text

Abstract:

Light scattering by small particles is the physical phenomenon that produces the natural rainbow in the sky. The same phenomenon can be reproduced in laboratory with monochromatic light giving rise to non-intrusive laser based techniques for the measurement of size and refractive index of particles suspended in a medium possessing lower refractive index. These techniques are commonly called "Rainbow Thermometry" techniques and appear at the beginning of the nineties. The measurement of size and refractive index of the particles is obtained through the analysis of the interference fringe image generated in the far field by means of the interaction between the laser light and the particles themselves. The work presented in this thesis has as objective the improvement of the Rainbow Techniques both on the theoretical aspects and the application.

In this thesis the Airy theory, which is used as theoretical model for the Standard Rainbow Thermometry, has been improved to minimize the discrepancies it was presenting respect to more complex and complete theories and it has been generalized to spherical particles presenting a spherically symmetric refractive index gradient. This generalized model has been used to evaluate the size and temperature of a n-octane burning droplet in standard atmosphere with good results. The generalization of the Standard Rainbow Thermometry to multiple particles, Global Rainbow Thermometry, is presented both theoretically and experimentally and the role of the particle asphericity in the light scattered intensity is evaluated.

Two experimental application of the Global Rainbow Thermometry are reported. The first one concerns the measurement of size and refractive index of silicon oil droplets suspended in an aqueous bulk. This experiment allows the Global Rainbow Thermometry validation through the comparison with measurements simultaneously obtained with well known experimental techniques as Back-Light scattering and thermocouple measurement with satisfactory results.

The second experiment concerns Global Rainbow Thermometry measurement performed on an evaporating flat-fan water spray. The results obtained, both for temperature and for size, are in satisfactory agreement with predictions already done by other authors and with numerical simulations performed by the engineering code CASIMIRE.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

3

Shukri, Ziad A. (Ziad Aziz). "Evaporation and sputtering processes for Se-CdO photovoltaic cell structures." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59607.

Full text

Abstract:

A study has been made of certain features of the fabrication of a Se-CdO photovoltaic cell having a layer structure usually of the form Al-Bi-Se-CdO-metal. It was found that increasing the substrate temperature during the selenium deposition between 80 and 140$ sp circ$C increased the illuminated short circuit current density in the cell. This clearly demonstrated the necessity of having well-crystallized selenium, as opposed to amorphous selenium, as the active absorber layer in this cell. The CdO layer was normally deposited by d.c. reactive sputtering from a cadmium target in an ambient of argon plus residual air and, as a result of optimizing experiments, conversion efficiency of about 2% was obtained under an illumination of 100 mWcm$ sp{-2}$. The CdO layer was also deposited by r.f. magnetron sputtering from a CdO target. This produced satisfactory cells but with lower shunt resistance values than in the d.c. sputtered devices. It was found that the electrical resistivity of the CdO layer was decreased with increase of r.f. power and with decrease of sputtering pressure. Exploratory Se-CdO cells were also fabricated on glass substrates using d.c. reactive sputtering. By connecting these electrically in series, a photovoltaic panel was constructed and incorporated as the power source in a small pocket calculator, which was found to function satisfactorily under indoor lighting. An inverted structure of the form CdO-Se-metal was also fabricated and shown to function as a photovoltaic device.

APA, Harvard, Vancouver, ISO, and other styles

4

Souche, Mireille, and Didier Long. "Ultra fast processes for solvent evaporation in thin polymer films below Tg." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195014.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Souche, Mireille, and Didier Long. "Ultra fast processes for solvent evaporation in thin polymer films below Tg." Diffusion fundamentals 3 (2005) 36, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14326.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Schmidt, Olaf. "Heat transfer and evaporation in spray cooling of hot gas flows, including the effect of nozzle design." Thesis, Middlesex University, 2001. http://eprints.mdx.ac.uk/13382/.

Full text

Abstract:

This study investigates the influence of spray nozzle internal geometry on heat transfer performance and the resultant power requirements. An experimental apparatus was designed and built, which allowed for close control of the heat transfer from air to water and the required energy for droplet production. The apparatus allowed for simultaneous measurements of heat transfer rate from the gas to the spray droplets and the pumping power requirements for the sprayed liquid. A spray chamber was constructed in the form of a Perspex cylinder, 372 mm internal diameter and 372 mm height, mounted on its vertical axis. Thermocouples, humidity sensors, and pressure sensors were used to measure the temperature difference of the air and water, the humidity difference of the air, and the pressure drop across the nozzle. The spray nozzles have been installed at the centre of the upper cover plate directed along the cylinder axis. The heat and mass transfer process was carried out in a counter current flow. Two different nozzle designs were the subject of this investigation. The pressure swirl nozzle works on liquid pressure alone. Droplet formation and size is influenced by changes of the internal geometry and liquid pressure. An effervescent two fluid atomiser with internal mixing was tested. The influence of changes in gas bubble and exit orifice geometry on droplet size and formation was investigated. Analysis of the heat transfer process is based on the energy balance for the whole cylinder. This analysis allows for the determination of the nozzle with the best performance characteristics. From the required energy to produce the droplets and the rate of heat transfer, a new equation for the index of energy performance, was defined. A Laser Doppler Analyser was used to determine the droplet size and velocity for the low pressure nozzles and this data was compared with the existing theory. The droplet distribution of the spray nozzles was determined for various configuration. The measured droplet size was below the calculated droplet size using the derived equations from the literature. Photographs of the spray angle at different liquid pressures were taken for digital analysis. The spray angle showed reasonable agreement with the literature. A three dimensional numerical model was designed to simulate the heat transfer process inside the spray chamber using PHOENICS, a Computational Fluid Dynamics (CFD) software. The software modelled the heat and mass transfer inside the spray chamber. This model then allowed for the testing of different droplet distributions, formations, and their influence on the heat transfer process. In order to validate the results, the necessary variables such as the gas mass flow, liquid mass flow rate, droplet size, spray angle and scatter, hot air inlet temperature, were obtained from the experimental data. The result of the simulation is the air outlet temperature and humidity of the spray chamber. The internal 3D flow field is solved with the Lagrangian and Eulerian equation including the disturbance, solved with the k-epsilon turbulence model, created by the spray droplets. Four different pressure swirl configurations were simulated. Every configuration had five different pressure points. Every pressure point was simulated individually in order to find out if the numerical simulation software was able to predict the correct result for different liquid mass flow rates without altering the boundary setting and parameters. The heat transfer process was found to depend on the droplet size and distribution produced by the spray nozzle. A comparison of the experimental data with the simulation results demonstrated the accuracy of the CFD model. The temperature accuracy was ±5.9% and for the humidity ±12% on average for all simulations. It was found that the heat transfer of the effervescent atomiser depends on the mass ALR and that the highest heat transfer was measured when it was operating with an ALR of 0.1. The tested effervescent atomiser was found to be strongly influenced by the atomising air, an effectiveness of 93% achieved. The change of the internal geometries had no significant influence on the heat transfer rates. The change of the internal geometry, especially the exit orifice diameter, had a strong influence on the pressure swirl nozzle performance, which started at 85% and reached a maximum of 95%. It was found that the pressure requirement for the 4.7 mm exit orifice was only 20% of the pressure requirement of the 2.5 mm exit orifice in order to achieve the same cooling performance. The pressure swirl needed for all flow rates approximately 20 times less energy to achieve the same cooling as the effervescent nozzle.

APA, Harvard, Vancouver, ISO, and other styles

7

Barella, Ortiz Anais. "Analysis and modelling of soil moisture and evaporation processes, implications for climate change." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066115/document.

Full text

Abstract:

Cette thèse étudie l'évaporation et l'humidité du sol, deux paramètres clefs du cycle hydrologique et du système climatique.L'évaporation potentielle (ETP) est un paramètre clef pour les modèles hydrologiques et agronomiques qui décrit les interactions entre la surface et l'atmosphère. Il constitue la base des estimations de l'évaporation réelle. Nous avons évalué, à l'échelle globale et pour le climat actuel ainsi que pour les changements attendus, des estimations de l'ETP basées sur des principes physiques ainsi que des approches empiriques. La méthode d'estimation du flux potentiel conseillée par la Food and Agriculture Organization (FAO) montre une sous évaluation par rapport au schéma de surface, ce qui a pu être relié à certaines hypothèses faites. Ceci implique aussi une sensibilité plus faible au changement climatique de la formulation proposée par la FAO. Nous avons aussi constaté que les méthodes empiriques ne représentent pas correctement l'impact du changement climatique sur l'ETP.L'humidité du sol est analysée du point de vue de la température de brillance en Bande-L (TB). Cette mesure du rayonnement émis par la surface dans une bande spectrale sensible à l'eau dans les premiers centimètres du sol, constitue une des pistes pour l'estimation de l'humidité de surface depuis l'espace. Des mesures de TB ont été comparées, au dessus de la Péninsule Ibérique, à des données simulées par deux schémas de surface. Un bon accord a été trouvé entre les observations et les simulations sur l'évolution temporelle des signaux. Par contre, les structures spatiales peuvent être très différentes au cours de l'automne et l'hiver à cause de cycles annuels très contrastés
This thesis deals with the study of evaporation and soil moisture, t wo main parameters of the hydrological cycle, and thus the climate system. First, potential evaporation (ET P ) is analysed. It is an important input to hydrological and agronomic models, key to describe the interactions between the surface e and the atmosphere, and the basis of most of the estimations of actual evapora tion. Physically-based and empirical methods to estimate ET P are evaluated, at a global scale, under current climate conditions and in a changing climate. The former methods correspond to those implemented in land surface models (LSM) and the Food and Agriculture Organization (F AO) reference evapotranspiration equation. The assumptions made in FAO's method underest imate ET P if compared to LSM methods. They also result in a lower sensitive ty of ET P to climate change. In addition, empirical equations are not able to reproduce the impact of climate change on ET P if compared to that from LSM methods. Soil moisture is the second aim of this thesis. It is treated t hrough the analysis of brightness temperatures (TB). These are a measure of the radiation emitted by the surface , and thus an optimum parameter to use in remote sensing techniques for soi l moisture retrieval. Measured TB from the Soil Moisture and Ocean Salinity (SMOS) mission are compared, over the Iberian Peninsula, to two sets of TB modelled estimates from two LSM. There is a good agreement in the temporal evolution between them. However, discrepancy es are found regarding the spatial structures, which become more evident during fall and winter and are mainly explained by differences in the annual cycle of measured and modelled TB

APA, Harvard, Vancouver, ISO, and other styles

8

Hassan, Aseel Kadhim. "Studies in electronic conduction processes in organic semiconducting thin films of copper phthalocyanine prepared by evaporation." Thesis, Keele University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306847.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Persson, Tony. "Evaporation and Heat-flux Aggregation in Heterogeneous Boreal Landscapes." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4326.

Full text

Abstract:

The boreal forests represent 8 % of all forested areas on the earth and have a significant role in the control of greenhouse gases and an impact on global climate change. The main objective of this thesis is to increase the understanding of how evaporation and heat-flux processes in the boreal forest zone are affecting the regional and global climate.

A meteorological mesoscale model with an advanced land-surface parameterization has been utilized to study aggregation of fluxes of water vapour and heat. The model has been compared against four other methods for flux estimation in a southern boreal landscape. The results show that the mesoscale model is successfully reproducing 24-hour averages of fractionally weighted mast measurements of sensible and latent heat flux.

The model was also evaluated against in-situ observations of surface fluxes and other meteorological variables. The results reveal that a correct initialization of soil moisture is crucial to simulate a realistic partitioning of the sensible and latent heat fluxes. Significant differences in surface fluxes and friction velocities between two apparently similar forest sites indicate the need for careful assessment of areal representativity when comparing mesoscale model results with in-situ observations.

A parameterization for the absorption of solar radiation of high-latitude sparse forests was implemented and tested in the model that significantly improved the simulation of high wintertime midday sensible heat fluxes. A scheme for heat storage in vegetation was also implemented which improved the results, but the scheme needs further evaluation for high latitude forests.

Two commonly used strategies for the description of land-surface heterogeneity, the effective parameter approach and the mosaic approach, were tested in the mesoscale model against airborne observations of sensible and latent heat fluxes. The results show that the mosaic approach produces better results especially when small lakes are present in model grid-squares.

Norra halvklotets barrskogsbälte representerar 8 % av all skogsbeklädd mark på jorden och har stor betydelse för kontrollen av växthusgaser och påverkan på globala klimatförändringar. Syftet med denna avhandling är att öka förståelsen av hur avdunstning och värmeflöden i den boreala skogszonen påverkar klimatet regionalt och globalt.

En meteorologisk mesoskalemodell med en avancerad landyteparameterisering har använts för att studera aggregering av avdunstning och värmeflöden. Modellen jämfördes med fyra andra metoder för uppskattning av värmeflöden i den boreala skogszonens södra delar. Resultaten visade att mesoskalemodellen reproducerar 24-timmarsmedelvärden av sensibelt och latent värmeflöde från areellt viktade mastmätningar med bra resultat.

Modellen utvärderades även mot markbaserade mätningar av sensibelt och latent värme och andra meteorologiska variabler. Resultaten visar att en korrekt initialisering av markvatteninnehållet är avgörande för att simulera en realistisk uppdelning av de sensibla och latenta värmeflödena. Markanta skillnader i markyteflöden och friktionshastigheter mellan två liknande skogsmätstationer påvisar nödvändigheten av en noggrann bedömning av den areella representativiteten när man jämför resultat från mesoskalemodellen med markbaserade mätningar.

En parameterisering för absorption av solstrålning i glesa skogsbestånd på höga breddgrader infördes och testades i modellen vilket markant förbättrade simuleringen av de höga sensibla värmeflöden som observerats vid middagstid på vintern. Ett uttryck för att beskriva värmelagring i vegetationen infördes också vilket förbättrade resultaten, men uttrycket behöver vidare utvärdering för skogsbestånd på höga breddgrader.

Två ofta använda strategier för att beskriva markytans heterogenitet, effektiva parametermetoden och mosaikmetoden, testades i mesoskalemodellen mot flygburna observationer av sensibla och latenta värmeflöden. Resultaten visar att mosaikmetoden ger bättre resultat särskilt när mindre sjöar förekommer i modellrutorna.

APA, Harvard, Vancouver, ISO, and other styles

10

Höfler, Matthias [Verfasser], Reinhold [Akademischer Betreuer] Kneer, and Manfred Christian [Akademischer Betreuer] Wirsum. "Theoretical evaluation of falling film evaporation for organic rankine cycle processes / Matthias Höfler ; Reinhold Kneer, Manfred Christian Wirsum." Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1211960048/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Xie, Jianfei. "Development of a new kinetic model for the analysis of heating and evaporation processes in complex hydrocarbon fuel droplets." Thesis, University of Brighton, 2013. https://research.brighton.ac.uk/en/studentTheses/866b0ab3-7dcc-44e4-8334-57d56b73cce3.

Full text

Abstract:

This work is concerned with the development of a new quantitative kinetic model for the analysis of hydrocarbon fuel droplet heating and evaporation, suitable for practical engineering applications. The work mainly focuses on the following two areas. Firstly, a new molecular dynamics (MD) algorithm for the simulation of complex hydrocarbon molecules, with emphasis on the evaporation/condensation process of liquid n-dodecane (C12H26), which is used as an approximation for Diesel fuel, has been developed. The analysis of n-dodecane molecules has been reduced to the analysis of simplified molecules, consisting of pseudoatoms, each representing the methyl (CH3) or methylene (CH2) groups. This analysis allows us to understand the underlying physics of the evaporation/condensation process of n-dodecane molecules and to estimate the values of its evaporation/condensation coefficients for a wide range of temperatures related to Diesel engines. Nobody, to the best of our knowledge, has considered MD simulation of molecules at this level of complexity. Secondly, a new numerical algorithm for the solution of the Boltzmann equation, taking into account inelastic collisions between complex molecules, has been developed. In this algorithm, additional dimensions referring to inelastic collisions have been taken into account alongside three dimensions describing the translational motion of molecules as a whole. The conservation of the total energy before and after collisions has been considered. A discrete number of combinations of the values of energy corresponding to translational and internal motions of molecules after collisions have been allowed and the probabilities of the realisation of these combinations have been assumed to be equal. This kinetic model, with the values of the evaporation coefficient estimated based on MD simulations, has been applied to the modelling of the heating and evaporation processes of n-dodecane droplets in Diesel engine-like conditions. In the previously developed kinetic models, applied to this modelling, all collisions were assumed to be elastic and the evaporation coefficient was assumed equal to 1. It is shown that the effects of inelastic collisions lead to stronger increase in the predicted droplet evaporation time relative to the hydrodynamic model, compared with the similar increase predicted by the kinetic model considering only elastic collisions. The effects of a non-unity evaporation coefficient are shown to be weak at gas temperatures around or less than 1,000 K but noticeable for gas temperatures 1,500 K. The application of the rigorous kinetic model, taking into account the effects of inelastic collisions and a non-unity evaporation coefficient, and the model considering the temperature gradient inside droplets is recommended when accurate predictions of the values of droplet surface temperature and evaporation time in Diesel engine-like conditions are essential.

APA, Harvard, Vancouver, ISO, and other styles

12

Mosthaf, Klaus [Verfasser], and Rainer [Akademischer Betreuer] Helmig. "Modeling and analysis of coupled porous-medium and free flow with application to evaporation processes / Klaus Mosthaf. Betreuer: Rainer Helmig." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2014. http://d-nb.info/1049438876/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Kumar, Abhijeet Verfasser], Tatiana [Akademischer Betreuer] [Gambaryan-Roisman, Peter [Akademischer Betreuer] Stephan, and Klitzing Regina [Akademischer Betreuer] von. "Wetting, evaporation and deposition processes in interaction of complex liquid formulations with porous substrates / Abhijeet Kumar ; Tatiana Gambaryan-Roisman, Peter Stephan, Regina von Klitzing." Darmstadt : Universitäts- und Landesbibliothek, 2020. http://nbn-resolving.de/urn:nbn:de:tuda-tuprints-142114.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Kumar, Abhijeet [Verfasser], Tatiana [Akademischer Betreuer] Gambaryan-Roisman, Peter [Akademischer Betreuer] Stephan, and Klitzing Regina [Akademischer Betreuer] von. "Wetting, evaporation and deposition processes in interaction of complex liquid formulations with porous substrates / Abhijeet Kumar ; Tatiana Gambaryan-Roisman, Peter Stephan, Regina von Klitzing." Darmstadt : Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1222163195/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Wallis, Kirsty. "Design of experiment studies for the fabrication processes involved in the micro-texturing of surfaces for fluid control." Thesis, Cranfield University, 2013. http://dspace.lib.cranfield.ac.uk/handle/1826/8456.

Full text

Abstract:

This thesis focuses on the use of a design of experiment approach to examine the significance of process factors and interactions on the fabrication of micro- textured surfaces. The micro-textured surfaces examined contain pillar and hole features ranging from 80 – 2 micrometers in diameter. The processes examined are the deep reactive ion etching of silicon wafers for the production of silicon mould inserts and the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicate samples of the silicon mould insert. During the deep reactive ion etching of the silicon wafers the design of experiment approach was used to determine the significant of platen power, C4F8 gas flow and switching times to the presence of pillar undercut of 10 x 10, 5 x 5 and 2 x 2 micrometer pillars. Undercuts occur when the pillar base has a smaller cross-section than the apex of the pillar. Switching times was found to be the only statistically significant parameter for both 10 x 10 and 5 x 5 micrometer pillars. The design of experiment approach is used in the micro-injection moulding of polypropylene, high density polyethylene and 316LS stainless steel replicates to examine the significance of mould temperature, cooling time, holding pressure and injection speed on the part and buffer mass of the produce samples, the height and width of pillar on the replicate surfaces and the variation of the replicated pillars height and width from the original silicon mould insert. Examination of the high density polyethylene replicates found that mould temperature was the most significant factor regarding pillar dimensions (and variation from the silicon mould insert) across the range of pillar sizes. Upon examination of the polypropylene replicates it was found that the factor of most significance on pillar dimensions varied across the different pillar sizes. Holding pressure was identified as the most significant factor with regards to the 53 x 29 and 19 x 80 micrometer pillars. Injection speed was found to be most significant for the 25 x 25 and 19 x 29 micrometer pillars. Cooling time was found to be most significant with regards to the 30 x 10, 25 x 10, 20 x 10 and 15 x 10 micrometer pillars. While ii mould temperature was found to be most significant for the 20 x 20, 15 x 15 and 10 x 30 micrometer pillars. The interaction between mould temperature and injection speed was also found to be the most significant factor with regards to the 43 x 29 and 25 x 30 micrometer pillars. Examination of the 316LS replicates found that mould temperature was the most significant factor regarding pillar dimensions for 80 x 80 and 19 x 80 micrometer pillars. While holding pressure was found to be most significant to the 29 x 29 micrometer pillars and injection speed was identified as most significant to the 53 x 80 micrometer pillars. The samples produced during the design of experiment investigations were then used to examine the effect of surface texturing on droplet behaviour. Droplet contact angles were examined on polypropylene, high density polyethylene and silicon samples structured with 10 – 2 micrometer pillar. Initial droplet contact angles were found to be higher on the polypropylene samples than the high density polyethylene or silicon samples. With the lowest initial contact angles being found for the silicon inserts. Droplet ‘channelling’ and evaporation were examined on silicon, polypropylene, high density polyethylene and 316LS samples structured with micro-channel surface pillars and holes ranging from 80 – 2 micrometer in diameter. Contact pinning of the droplet to the surface via the three- phase contact-line was noted during observations of droplet ‘channelling’. This pinning effect was observed at all sample tilt angles (30 - 90 o ). With regards to droplet evaporation, the droplets were noted to evaporate evenly (with no or limited contact pinning) on all unstructured surfaces and the surfaces structured with hole features. On the surfaces structured with pillar features, the droplets appeared too evaporated along the surface gradient from the smallest pillars to the largest.

APA, Harvard, Vancouver, ISO, and other styles

16

Vera-Tudela, Fajardo Walter Martin. "An experimental study of the effects of fuel properties on diesel spray processes using blends of single-component fuels." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/58865.

Full text

Abstract:

[EN] This last few years, the trend in diesel engines has been to use different kinds of fuels to identify their influence and behaviour on the emissions and performance. Among the wide variety of fuels employed are the so called Primary Reference Fuels (PRFs), which represent the behaviour of diesel and gasoline in terms of ignition properties, as they are located at both ends of the octane rating scale and also have very different cetane numbers. One of the disadvantages of using pure gasoline or diesel-gasoline blends in diesel engines is the time needed for the mixture to ignite and to completely burn the fuel. This generally requires working with partial loads or with premixed charges. In order to isolate the fuel effects on the spray processes and to be able to study the characteristic parameters of ignition delay time, lift-off length, vapour and liquid penetration, among others; different experiments under parametric variations of diesel like conditions have been performed. The tests were performed under inert and reactive conditions in a 2-stroke optical engine and a constant-pressure flow (CPF) high-pressure high-temperature vessel using single-hole nozzles, while diverse optical techniques were being employed. To study the influence of the fuel properties, different single-component fuels were employed as well as binary blends and a six-component diesel surrogate, which was also compared to conventional diesel. Additionally, the results have been contrasted with a one-dimensional model in order to further explain the values and trends found. The results presented a strong dependency on the fuel properties for the tests performed under inert and reactive conditions. The difference in physical properties of n-decane and n-hexadecane showed an almost linear reduction of the stabilized liquid penetration down to approximately 60% under some conditions. Additionally, due to the composition of the surrogate fuel, pure n-hexadecane was demonstrated to have almost identical evaporation characteristics, hence proving itself as a good candidate for a single-component surrogate of diesel fuel. In a similar way, the chemical properties of the PRFs n-heptane and iso-octane also proved to be influential on the spray development and radiation emitted. Ignition delay values up to one order of magnitude larger where obtained for both extremes of the blend range, as well as lift-off lengths up to three times longer. The radiation emitted by the soot incandescence presented the highest variations, as some conditions showed a reduction of almost four orders of magnitude among the blend range. Moreover, some cases did not present any radiation corresponding to the soot, and increasing the sensitivity of the camera only caused the chemiluminescence of the OH* radical to be captured. On a different way, the stabilized flame length determined also by the soot radiation did not present much variation as the fuel properties or the air temperature were changed; in fact, the only noticeable differences were caused by the changes in the oxygen composition of the ambient air. In conclusion, the fuel properties proved to have a significant effect on the spray processes. Lighter fuels favoured the evaporation of the spray under a range of conditions, while fuels with lower octane numbers ignited sooner and closer to the spray tip but with more soot luminosity measured.
[ES] Estos últimos años, la tendencia en motores diesel ha sido la de emplear distintos tipos de combustibles para identificar su influencia y comportamiento sobre las emisiones y rendimiento. Dentro de la amplia variedad de combustibles empleados están los llamados combustibles de referencia (PRFs ingl. Primary Reference Fuels), los cuales representan el comportamiento del diesel y la gasolina en lo que respecta a propiedades de encendido, ya que se encuentran en ambos extremos de la escala del número de octano y también poseen números de cetano muy distintos. Una de las desventajas de utilizar gasolina pura o mezclas de diesel-gasolina en motores diesel es el tiempo que toma la mezcla en encender y quemar completamente el combustible. Esto generalmente requiere trabajar con cargas parciales o cargas premezcladas. Para poder aislar los efectos del combustibles sobre los procesos de un chorro y que sea capaz estudiar los parámetros característicos de tiempo de retraso de encendido, longitud de despegue de llama, penetración de líquido y vapor, entre otros, se han realizado distintos experimentos bajo variaciones paramétricas de condiciones de motor diesel. Los ensayos han sido realizados bajo condiciones inertes y reactivas en un motor óptico de dos tiempos y una instalación de alta presión y alta temperatura de flujo continuo a presión constante (CPF ingl. Constant-Pressure Flow) empleando toberas mono-orificio, con aplicación de diversas técnicas ópticas. Para estudiar la influencia de las propiedades de los combustibles se utilizaron distintos mono-componentes, así como mezclas binarias y un sustituto de diesel conformado por seis componentes, el cual fuel comparado con diesel convencional. Adicionalmente, los resultados han sido contrastados con un modelo unidimensional para ayudar a explicar los valores y tendencias encontrados. Los resultados presentaron una fuerte dependencia de las propiedades de los combustibles en los ensayos realizados bajo condiciones inertes y reactivas. La diferencia entre las propiedades físicas del n-decano y n-hexadecano mostraron una reducción casi lineal sobre la longitud líquida estabilizada hasta aproximadamente un 60% bajo ciertas condiciones. Adicionalmente, debido a la composición del combustible de sustitución, el n-hexadecano puro demostró tener características de evaporación prácticamente idénticas, probándose a sí mismo como un buen candidato para ser un sustituto mono-componente del diesel convencional. De una manera similar, las propiedades químicas de los PRFs n-heptano e iso-octano también probaron tener influencia sobre el desarrollo del chorro y radiación emitida. Se obtuvieron valores de tiempo de retraso con diferencias de hasta un orden de magnitud entre ambos extremos del rango de las mezclas, así como longitudes de despegue de llama hasta tres veces más largas. La radiación emitida por la incandescencia del hollín presentó las variaciones más altas, ya que algunas condiciones mostraron reducciones de hasta cuatro órdenes de magnitud dentro del rango de mezclas. Es más, algunos casos no presentaron radiación correspondiente al hollín, e incrementar la sensibilidad de la cámara solo ocasionó que la quimioluminiscencia del radical OH* sea detectada. Por otro lado, la longitud estabilizada de llama calculada mediante la radiación del hollín no presentó mucha variación respecto a las propiedades del combustible o la temperatura del aire. De hecho, la única diferencia apreciable fue causada por los cambios en la composición del oxígeno del aire ambiente. En conclusión, las propiedades de los combustibles demostraron tener un efecto significativo en los procesos de un chorro diesel. Los combustibles más ligeros favorecieron la evaporación del chorro en un rango de condiciones, mientras que combustibles con números de octano más bajos encendieron más pronto y cerca de la tobera pero con mayor luminosidad del hollín medida.
[CAT] En aquests últims anys, la tendència en motors Diesel ha estat la d'emprar diferents tipus de combustibles per a identificar la seva influència i comportament sobre les emissions i rendiment. Dintre de l'àmplia varietat de combustibles emprats estan els anomenats combustibles de referència (PRFs angl. Primary Reference Fuels), els quals representen el comportament del dièsel i la gasolina pel que fa a propietats d'encesa, ja que es troben en ambdós extrems de l'escala del nombre d'octà i també posseeixen nombres de cetà molt diferents. Un dels desavantatges d'utilitzar benzina pura o barreges de Diesel-benzina en motors Diesel és el temps que pren la barreja a encendre i cremar completament el combustible. Això generalment requereix treballar amb càrregues parcials o càrregues premesclades. Per a poder aïllar els efectes del combustibles sobre els processos d'un doll i que sigui capaç estudiar els paràmetres característics de de temps de retard d'encesa, longitud d'enlairament de flama, penetració de líquid i vapor, entre altres, s'han estudiat diferents experiments sota variacions paramètriques de condicions de motor Diesel. Els assajos han estat realitzats sota condicions inertes i reactives en un motor de dos temps i una instal·lació d'alta pressió i alta temperatura de flux continu a pressió constant (CPF angl. Constant-Pressure Flow) emprant toberes mono-orifici, amb aplicació de diverses tècniques òptiques. Per a estudiar la influència de les propietats dels combustibles, van ser utilitzats distints mono-components, així com barreges binàries i un substitut de Diesel conformat per sis components, el qual fuel comparat amb Diesel convencional. Addicionalment, els resultats han estat contrastats amb un model unidimensional per a ajudar a explicar els valors i tendències trobats. Els resultats van presentar una forta dependència de les propietats dels combustibles en els assajos realitzats sota condicions inertes i reactives. La diferència entre les propietats físiques del n-decà i n-hexadecà van mostrar una reducció gairebé lineal sobre la longitud líquida estabilitzada fins a aproximadament un 60% sota certes condicions. Addicionalment, degut a la composició del combustible de substitució, el n-hexadecà pur va demostrar ser tindre característiques d'evaporació pràcticament idèntiques a aquell, demostrant ser un bon candidat per a ser un substitut mono-component del dièsel convencional. D'una manera similar, les propietats químiques dels PRFs n-heptà i iso-octà també provaren tindre influència sobre el desenvolupament del doll i la radiació emesa. Es van obtenir valors de temps de retard amb diferències de fins a un ordre de magnitud entre ambdós extrems del rang de les barreges, així com longituds d'enlairament de flama fins a tres vegades més llargues. La radiació emesa per la incandescència del sutge va presentar les variacions més grans, ja que algunes condicions van mostrar reduccions de fins a quatre ordres de magnitud dintre del rang de barreges. Encara més, alguns casos no van presentar radiació corresponent al sutge, i incrementar la sensibilitat de la càmera solament va ocasionar que la quimioluminiscència del radical OH* sigui detectada. D'altra banda, la longitud estabilitzada de flama calculada mitjançant la radiació del sutge no va presentar molta variació respecte a les propietats del combustible o la temperatura del aire. De fet, la única diferència apreciable va ser causada pels canvis en la composició del oxigen de l'aire ambient. En conclusió, les propietats dels combustibles van demostrar tenir un efecte significatiu en els processos d'un doll dièsel. Els combustibles més lleugers van afavorir l'evaporació del doll en un rang de condicions, mentres que els combustibles amb nombre d'octà més baixos van prendre més aviat i prop de la tovera però amb més lluminositat del sutge mesurat.
Vera-Tudela Fajardo, WM. (2015). An experimental study of the effects of fuel properties on diesel spray processes using blends of single-component fuels [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/58865
TESIS

APA, Harvard, Vancouver, ISO, and other styles

17

Öman, Cecilia. "Emissions of organic compounds from landfills /." Stockholm : Tekniska högsk, 1998. http://www.lib.kth.se/abs98/oman0604.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Baumann, Gunther [Verfasser], Wilhelm [Akademischer Betreuer] Dominik, Jan [Akademischer Betreuer] Henninges, Frank [Akademischer Betreuer] Börner, and Michael [Akademischer Betreuer] Kühn. "Determination of displacement and evaporation/precipitation processes via Pulsed Neutron-Gamma (PNG) monitoring for CO2 storage operations / Gunther Baumann. Gutachter: Wilhelm Dominik ; Frank Börner ; Michael Kühn ; Jan Henninges. Betreuer: Wilhelm Dominik ; Jan Henninges." Berlin : Technische Universität Berlin, 2013. http://d-nb.info/1065665113/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Danovič, Jakub. "Eliminace degradačních procesů kovových tenkých vrstev." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221002.

Full text

Abstract:

This work deals with issues of thin films, their behaviour in different enviroments and protection of theese films against unwanted degradation processes. Metal thin films are made by special physical or chemical methods in the presence of vacuum. Deposition is performed on properly cleaned substrate made of different materials, for example glass, ceramics or another metal. Theese films degrades under the influence of moisture, heat and other. There are several types of films on different bases made to prevent thin films against degradation.

APA, Harvard, Vancouver, ISO, and other styles

20

Cavallius, Matilda, and Oskar Rehnstedt. "Befuktning : Installationer, processer och hälsofördelar." Thesis, KTH, Byggteknik och design, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-215298.

Full text

Abstract:

Det finns tydliga hälsofördelar med en relativ fuktighet på 40–60% inomhus. Trots detta finns det idag inga direktiv på hur man ska styra den relativa fuktigheten inomhus. Många gånger diskuteras det kring avfuktning men i denna rapport tas befuktning upp ur ett hälsoperspektiv.I denna studie har det undersökts huruvida befuktningssystem skulle kunna användas i större utsträckning till fördel för människors hälsa.I rapporten redogörs för olika befuktningmetoder samt deras termofysiska processer - adiabatisk eller isotermisk. Dessutom undersöks vad som händer med energin i luften och vattenångan vid olika temperaturer samt vad olika relativ fuktighet har för hälsomässiga för- och nackdelar.Resultatet visar på att det finns både etablerade befuktningssystem samt ett behov av befuktning. Däremot är efterfrågan av befuktning inte speciellt stor i bostäder och branschen ställer sig negativ till befuktning i ventilationssystem.
There are clear health benefits of having a relative humidity between 40–60% indoors. Despite this, there are currently no directives on what level the relative humidity should be indoors. Today dehumidification is a common matter but this report is about humidification, from a health perspective.In this study, it has been investigated whether humidification could be used to a greater extent, to the benefit of humans’ health.This report describes various humidification methods and their thermophysical processes - adiabatic and isothermal. It is also explained what happens to the energy in the air and water vapor at different temperatures and how the relative humidity affects our health at different levels.The result shows that there is a need for humidification and that there are several technical solutions available today. However, the demand is low and the industry is not very positive to the idea of humidification in ventilation systems.

APA, Harvard, Vancouver, ISO, and other styles

21

Berthias, Francis. "Thermalisation dans une nanogoutte d’eau." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1164/document.

Full text

Abstract:

L'évaporation d'une molécule d'eau se traduit par la rupture d'une ou plusieurs liaisons hydrogène. Ces liaisons hydrogène sont à l'origine de nombreuses propriétés remarquables de l'eau. A l'échelle macroscopique, l'eau est connue pour son efficacité à thermaliser un système, tandis qu'au niveau microscopique, un transfert ultrarapide d'énergie vibrationnelle par l'intermédiaire des liaisons hydrogène a été observé. Qu'en est-il à l'échelle d'une nanogoutte lorsque qu'un nombre limité de molécules entre en jeu? Dans l'expérience réalisée auprès du dispositif DIAM de l'IPN Lyon, la relaxation d'une nanogoutte d'eau protonée est observée après excitation électronique d'une de ses molécules. La mise en œuvre d'une méthode d'imagerie de vecteur vitesse associée à la technique COINTOF (COrrelated Ion and Neutral Time-Of-Flight) a permis la mesure de la distribution de vitesse de molécules évaporées d'agrégats d'eau protonés, préalablement sélectionnés en masse et en énergie. La forme des distributions de vitesse mesurées montre que, même pour des nanogouttes composées de quelques molécules d'eau, l'énergie est redistribuée dans la goutte avant évaporation. Pour des nanogouttes contenant moins d'une dizaine de molécules d'eau, les distributions de vitesse mesurées sont proches de celles attendues pour des gouttes macroscopiques. La redistribution statistique de l'énergie apparaît comme un processus de relaxation dominant. Cependant, la mesure de la distribution des vitesses met aussi en évidence une contribution distincte à haute vitesse correspondant à l'éjection d'une molécule avant redistribution complète de l'énergie. Les distributions de vitesse mesurées pour des nanogouttes d'eau lourdes deutérées mettent en évidence une proportion d'événements non ergodiques plus importante que pour l'eau normale. Les mesures réalisées avec différents atomes cibles montrent que la proportion d'événements non ergodique diminue avec la diminution de l'énergie déposée dans la nanogoutte
The evaporation of a water molecule resulting in the rupture of one or more hydrogen bonds. These hydrogen bonds are responsible for many remarkable properties of water. At the macroscopic scale, water is well known for its ability to thermalize a system, while at the microscopic level, a high-speed transfer of vibrational energy through hydrogen bonding was observed. What scale of nanogoutte when a limited number of molecules come into play? In the experiment carried out with the device DIAM IPN Lyon, the relaxation of a nanogoutte of protonated water is observed after electronic excitation of one of its molecules. The implementation of a velocity vector imaging method associated with the technical COINTOF (Correlated Ion and Neutral Time-Of-Flight) allowed the measurement of the velocity distribution of molecules of evaporated protonated water clusters, mass and energy preselected. The shape of the measured velocity distributions shows that even for some nanodroplets composed of few water molecules, the energy is redistributed in the drop before evaporation. For nanodroplets containing less than ten water molecules, the measured velocity distributions are closed to those expected for macroscopic droplets. The statistical redistribution of energy appears as a dominant relaxation process. However, the measurement of the velocity distribution also highlights a distinct contribution at high velocity corresponding to the ejection of a molecule before complete redistribution of energy. The measured velocity distributions for heavy water nanodroplets deuterated show a proportion of non-ergodic most important events that for normal water. The measurements carried out with different target atoms show that the proportion of non-ergodic events decreases with decreasing the energy deposited in the nanogoutte

APA, Harvard, Vancouver, ISO, and other styles

22

Arora, Sachin. "Modeling and control of emulsion polymerization processes with evaporative cooling." Aachen Shaker, 2007. http://d-nb.info/988687267/04.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Arora, Sachin. "Modeling and control of emulsion polymerization processes with evaporative cooling /." Aachen : Shaker, 2008. http://d-nb.info/988687267/04.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Arora, Sachin [Verfasser]. "Modeling and Control of Emulsion Polymerization Processes with Evaporative Cooling / Sachin Arora." Aachen : Shaker, 2008. http://d-nb.info/1162791705/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Cabrera, Jamoule Juan. "Etude des processus de fusion-fission et de fusion-évaporation dans l'interaction 20 Ne + 159 Tb entre 8 et 16 MeV/nucléon." Université catholique de Louvain, 2002. http://edoc.bib.ucl.ac.be:81/ETD-db/collection/available/BelnUcetd-06022006-191457/.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

Kam, Kiew M. "Simulation and implementation of nonlinear control systems for mineral processes." Thesis, Curtin University, 2000. http://hdl.handle.net/20.500.11937/2383.

Full text

Abstract:

Differential geometric nonlinear control of a multiple stage evaporator system of the liquor burning facility associated with the Bayer process for alumina production at Alcoa Wagerup alumina refinery, Western Australia was investigated.Mathematical models for differential geometric analysis and nonlinear controller synthesis for the evaporator system were developed. Two models, that were structurally different from each other, were used in the thesis for simulation studies. Geometric nonlinear control structure, consisting of nonlinear state feedback control laws and multi-loop single-input single-output proportional-integral controllers, were designed for the industrial evaporator system. The superiority of the geometric nonlinear control structure for regulatory control of the evaporator system was successfully demonstrated through computer simulations and real-time simulator implementation. The implementation trial has verified the practicality and feasibility of these type of controllers. It also re-solved some practical issues of the geometric nonlinear control structure for industrial control applications. In addition, the implementation trial also established a closer link between the academic nonlinear control theory and the industrial control practices.Geometric nonlinear output feedback controller, consisting of the geometric nonlinear control structure and reduce-order observer was proposed for actual plant implementation on the evaporator system on-site. Its superior performance was verified through computer simulations, but its feasibility on the evaporator system on-site has yet to be investigated either through simulator implementation or actual plant implementation. This investigation was not performed due to the time constraint on the preparation of this thesis and the inavailability of the plant personnel required for this implementation.Robust nonlinear control structures that are simple and computationally efficient have been proposed for enhancing the performance of geometric nonlinear controllers in the presence of plant/model mismatch and/or external disturbances. The robust nonlinear control structures are based on model error compensation methods. Robustness properties of the proposed robust nonlinear control structures on the evaporator system were investigated through computer simulations and the results indicated improved performance over the implemented geometric nonlinear controller in terms of model uncertainty and disturbance reductions.A software package was developed in MAPLE computing environment for the analysis of nonlinear processes and the design of geometric nonlinear controllers. This developed symbolic package is useful for obtaining fast and exact solutions for the analysis and design of nonlinear control systems. Procedures were also developed to simulate the geometric nonlinear control systems. It was found that MAPLE, while it is superior for the analyses and designs, is not viable for simulations of nonlinear control systems. This was due to limitation of MAPLE on the physical, or virtual, memory management. The use of both symbolic and numeric computation for solutions of nonlinear control system analysis, design and simulation is recommended.To sum up, geometric nonlinear controllers have been designed for an industrial multiple stage evaporator system and their simplicity, practicality, feasibility and superiority for industrial control practices have been demonstrated either through computer simulations or real-time implementation. It is hoped that the insights provided in this thesis will encourage more industry-based projects in nonlinear control, and thereby assist in closing the widening gap between academic nonlinear control theory and industrial control practice.Keywords: geometric nonlinear control, input-output linearization, multiple stage evaporator, robust geometric nonlinear control, control performance enhancement.

APA, Harvard, Vancouver, ISO, and other styles

27

Zago, Gustavo Pereira. "Estudo da co-cristalização em sistema ternário NaCI-CaSO4-H2O para dessalinização de água." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-15012018-132007/.

Full text

Abstract:

O crescimento acelerado da população mundial e o consequente aumento da produção de bens de consumo tem impulsionado uma crise na disponibilidade de recursos naturais, principalmente os hídricos. Diante da escassez de recursos hídricos, processos de tratamento de efluentes industriais e domésticos que visam o descarte zero de líquido (ZLD - Zero Liquid Discharge) vêm sendo cada vez mais estudados. Atualmente, diversos processos têm sido empregados com este propósito. No entanto, ainda há a geração, juntamente com a água recuperada, de uma corrente composta por uma solução salina concentrada, cuja composição normalmente é constituída por diferentes tipos de sais inorgânicos. Uma das formas de alcançar o descarte zero de líquidos é por meio da implementação de um processo adicional de separação, sendo a cristalização evaporativa considerada viável para essa finalidade. O emprego deste processo é limitado ao controle das características morfológicas das partículas obtidas, visto que estas influenciam diretamente na efetividade de separação dos processos subsequentes à cristalização (filtração, centrifugação). Além disso, efluentes industriais são soluções complexas, e a utilização da cristalização envolve a presença de mais de um sal em solução (co-cristalização). Este processo é pouco investigado na literatura científica, logo, a determinação de condições de processos visando controlar a características destas partículas não é trivial. Neste trabalho, foram estudados o efeito da taxa de evaporação e da presença de sementes na morfologia, composição, tamanho e hábito de partículas de cloreto de sódio e sulfato de cálcio obtidas por co-cristalização evaporativa em bateladas. Os resultados serviram para a determinação de parâmetros de operação para a co-cristalização visando a obtenção de partículas com elevado tamanho médio e baixa dispersão de tamanhos. Taxas de evaporação elevadas favoreceram a obtenção de aglomerados de partículas. A presença de sulfato de cálcio em solução resultou em partículas maiores, menos polidispersas e com menor grau de aglomeração. Tal resultado foi considerado positivo, visto que, estas características são desejáveis para a separação dos cristais da solução mãe. Foi também observado que as sementes de hemihidrato atuam inibindo a aglomeração dos cristais de NaCl. O aumento da quantidade de sementes destes sais culminou na obtenção de partículas menos aglomeradas, porém houve um alargamento das distribuições de tamanho de partículas. Nos experimentos em que foram utilizadas sementes de ambos os sais, o mesmo efeito na aglomeração foi observado. Em todos os experimentos com semeadura de hemihidrato, foi observada a aglomeração deste sal com o NaCl, que foi intensificada com o aumento da taxa de evaporação e com o aumento da concentração de sementes. Foi identificada a possibilidade de recuperação de ambos os sais e obtenção - em determinadas condições - de mais de 90% do NaCl com até 99,50% de pureza.
The accelerated growth of the world population and the consequent increase in the production of consumer goods, has driven to a crisis in the availability of natural resources, especially water. Due to the scarcity of water resources, industrial and domestic wastewater treatment processes that aim the Zero Liquid Discharge (ZLD) have been increasingly studied. Nowadays, several processes have been used for this purpose. However, in all of them, there is still the generation of a brine composed of a concentrated salt solution, concomitantly with the recovered water, whose composition is normally constituted by different types of inorganic salts. One way to achieve the ZLD is through the implementation of an additional separation process, for which the evaporative crystallization is considered technically viable for this purpose. The use of this process is limited to the control of the morphological characteristics of the particles obtained, since this influences directly the separation effectiveness of the downstream processes to crystallization (filtration, centrifugation). Besides, industrial effluents are complex solutions and its crystallization involves the presence of more than one salt in solution (cocrystallization). This process is still not well investigated on scientific literature, thus, the determination of process conditions aiming to control the characteristics of these particles is not trivial. In this work, the effect of the evaporation rate and the presence of seeds on the morphology, composition, size and habit of sodium chloride and calcium sulfate particles obtained by batch evaporative co-crystallization were studied. The results were used to determine the operating parameters for the cocrystallization in order to obtain particles with high average size and narrow dispersion of sizes. High evaporation rates favored the obtaining of agglomerated particles. The presence of calcium sulfate in solution resulted in larger particles, less polydisperse and with less degree of agglomeration. Such result was considered positive, since, these characteristics are desirable for the separation of the crystals from the solution. Seeds of hemihydrate inhibited the agglomeration of the NaCl crystals. The increase in seed load of hemihydrate culminated in obtaining less agglomerated particles, but there was an increase in particle size distributions. In the experiments in which seeds of both salts were used, the same effect in the agglomeration was observed. In all experiments with seeds of hemihydrate, agglomeration of this salt with NaCl was observed, which was intensified with increasing evaporation rate and increasing seed amount. It was identified the possibility of recovery of both salts and, for certain conditions, obtaining more than 90% of NaCl with up to 99.50% purity.

APA, Harvard, Vancouver, ISO, and other styles

28

Kam, Kiew M. "Simulation and implementation of nonlinear control systems for mineral processes." Curtin University of Technology, School of Chemical Engineering, 2000. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=10063.

Full text

Abstract:

Differential geometric nonlinear control of a multiple stage evaporator system of the liquor burning facility associated with the Bayer process for alumina production at Alcoa Wagerup alumina refinery, Western Australia was investigated.Mathematical models for differential geometric analysis and nonlinear controller synthesis for the evaporator system were developed. Two models, that were structurally different from each other, were used in the thesis for simulation studies. Geometric nonlinear control structure, consisting of nonlinear state feedback control laws and multi-loop single-input single-output proportional-integral controllers, were designed for the industrial evaporator system. The superiority of the geometric nonlinear control structure for regulatory control of the evaporator system was successfully demonstrated through computer simulations and real-time simulator implementation. The implementation trial has verified the practicality and feasibility of these type of controllers. It also re-solved some practical issues of the geometric nonlinear control structure for industrial control applications. In addition, the implementation trial also established a closer link between the academic nonlinear control theory and the industrial control practices.Geometric nonlinear output feedback controller, consisting of the geometric nonlinear control structure and reduce-order observer was proposed for actual plant implementation on the evaporator system on-site. Its superior performance was verified through computer simulations, but its feasibility on the evaporator system on-site has yet to be investigated either through simulator implementation or actual plant implementation. This investigation was not performed due to the time constraint on the preparation of this thesis and the inavailability of the plant personnel required for this implementation.Robust ++
nonlinear control structures that are simple and computationally efficient have been proposed for enhancing the performance of geometric nonlinear controllers in the presence of plant/model mismatch and/or external disturbances. The robust nonlinear control structures are based on model error compensation methods. Robustness properties of the proposed robust nonlinear control structures on the evaporator system were investigated through computer simulations and the results indicated improved performance over the implemented geometric nonlinear controller in terms of model uncertainty and disturbance reductions.A software package was developed in MAPLE computing environment for the analysis of nonlinear processes and the design of geometric nonlinear controllers. This developed symbolic package is useful for obtaining fast and exact solutions for the analysis and design of nonlinear control systems. Procedures were also developed to simulate the geometric nonlinear control systems. It was found that MAPLE, while it is superior for the analyses and designs, is not viable for simulations of nonlinear control systems. This was due to limitation of MAPLE on the physical, or virtual, memory management. The use of both symbolic and numeric computation for solutions of nonlinear control system analysis, design and simulation is recommended.To sum up, geometric nonlinear controllers have been designed for an industrial multiple stage evaporator system and their simplicity, practicality, feasibility and superiority for industrial control practices have been demonstrated either through computer simulations or real-time implementation. It is hoped that the insights provided in this thesis will encourage more industry-based projects in nonlinear control, and thereby assist in closing the widening gap between academic nonlinear control theory and industrial control ++
practice.Keywords: geometric nonlinear control, input-output linearization, multiple stage evaporator, robust geometric nonlinear control, control performance enhancement.

APA, Harvard, Vancouver, ISO, and other styles

29

To, Lap C. "Nonlinear control techniques in alumina refineries." Thesis, Curtin University, 1996. http://hdl.handle.net/20.500.11937/130.

Full text

Abstract:

Nonlinearities exist in all process control systems. The use of linear control techniques is valid only in a narrow range of operation. Therefore, in this thesis, multivariable nonlinear control techniques are considered. The target process is the single effect evaporative process of the liquor burning unit in Alcoa's alumina refinery in Kwinana and the proposed triple effects unit in the Wagerup refinery. Two types of nonlinear control strategies using differential geometry were studied, namely, the input output linearization (Kravaris and Soroush, 1990) and the input state linearization (Hunt et al, 1983a). The research has successfully demonstrated the superiority and simplicity of the nonlinear controller through simulations and plant implementations. An integrated software package using MAPLE V.3 as the computing environment was developed to automate the solution algorithms and to graphically simulate the closed loop dynamics of different processes using the two nonlinear control strategies.The issue of robustness of the nonlinear controller was addressed by developing a procedure called uncertainty vector adjustment. The effectiveness of the new strategy was successfully demonstrated on the simulated liquor burning process. Furthermore, the stability of the adjustment technique was proved and its theoretical bounds were established using Lyapunov function analysis.A comparative study of geometric nonlinear filter and extended Kalman filter was conducted to reduce the requirement of full state feedback necessary for nonlinear control using either input output linearization or input state linearization. The simulation of the single effect evaporation unit of the liquor burning process showed that the geometric nonlinear filter is superior to the extended Kalman filter in terms of nonlinear tracking performances.The plant trials of the input output linearization in Alcoa's Kwinana alumina refinery demonstrated the practicability and feasibility of implementing nonlinear control in an industrial setting and also fostered a closer gap between academia and industry. The trials established guidelines for implementing a global linearizing controller on site, including conversion of the relevant constraints and the output of an industrial proportional and integral controller to the equivalent proportional and integral action required by the nonlinear controller. The results showed that the performance of the nonlinear controller was better than the current linear controller on site in terms of responsiveness and resistance to disturbances. Hence, the nonlinear control strategy enables the process to settle faster.All in all, efforts have been made in this thesis to minimise the use of abstract mathematical language and, in some cases, simplify the language so that nonlinear control theory can be understood by a wider range of audience, especially industrial practitioners. It is hoped that the insights provided in the dissertation will encourage more industrial implementations of nonlinear controllers and forge more interaction to close the widening gap between academic and industrial practice in process control.Keywords: nonlinear control, differential geometry, symbolic algebra, evaporator process, uncertainty vector adjustment, geometric nonlinear filter.

APA, Harvard, Vancouver, ISO, and other styles

30

Risse, Benedikt. "Continuous crystallization of ultra-fine energetic particles by the Flash-Evaporation Process." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0144/document.

Full text

Abstract:

Sous l'effet d'une forte impulsion mécanique, d'une chaleur très forte ou d'une décharge électrostatique, un explosif comme le TNT ou le RDX peut accidentellement être initié. L'énergie apportée à l'explosif est convertie en chaleur, appelée point-chaud, dans des endroits spécifiques, contenant des impuretés, bulles de gaz, pores ouverts ou autres hétérogénéités. La taille d'un point-chaud de quelques micromètres peut être déjà suffisante pour initier une déflagration ou même une détonation. En réduisant la taille des particules de l'explosif, la formation des points-chauds est empêchée conduisant à un matériau moins sensible. Au sein de ce travail, un procédé continu est développé, fondé sur le principe de la cristallisation-flash, et permettant la préparation de particules énergétiques submicroniques en quantité de plusieurs grammes. Le procédé repose sur une opération de séchage par atomisation, au cours de laquelle une solution surchauffée est atomisée d'une manière continue. Afin de diminuer la taille moyenne des particules et d'obtenir une distribution de taille des particules très étroite, une étude paramétrique est réalisée. Au moyen de la cristallisation-flash, la préparation de composites énergétiques de haute qualité en grandes quantités est un succès. La qualité et quantité de ce composite énergétique sont uniques. Grâce au potentiel de ce procédé, la cristallisation-flash peut permettre la préparation de nombreuses substances et compositions énergétiques ou inertes
High explosives, such as TNT or RDX, may be accidentally initiated under the influence of a strong mechanical impulse, great heat or an electrostatic discharge. Smallest impurities, open pores, entrapped gases or other inhomogeneities within the explosive matrix may convert the delivered energy into heat, causing the formation of a so called hot-spot. A hot-spot size of a few micrometers can already be sufficient to initiate a deflagration or even a detonation of the explosive. By decreasing the particle size of the explosive, the formation of hot-spots is inhibited, resulting in a less sensitive material. In this work, a continuous operating flash-crystallization process was developed, being able to produce energetic submicron particles in a multigram scale. The process bases on a spray drying process where superheated solutions are continuously atomized. A parametric study was performed on this process in order to decrease the particle size and obtaining a narrower particle size distribution. By means of this flash-crystallization process, highly homogeneous energetic composites were prepared in a large scale. The quality and amount of the energetic composite are unique. The versatility of the flash-crystallization process allows the preparation of a large number of energetic and inert substances and compositions

APA, Harvard, Vancouver, ISO, and other styles

31

Kane, Abdoulaye. "Conception et caractérisation d’un microcontacteur à film tombant : concept de distillation microstructurée." Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL086N/document.

Full text

Abstract:

Il est démontré que dans de nombreux procédés de transformation de la matière, les dégradations entropiques (et les consommations énergétiques qui en découlent) peuvent être minimisées en répartissant les flux d’énergies dans le volume plutôt qu’aux bornes du système (exemple de la distillation diabatique). Cependant la réalisation et la gestion de profils thermiques contrôlés (tels que des gradients thermiques et des étagements de température maîtrisés) dans les appareils compactes ne sont pas très souvent réalisées parce que souvent complexes et coûteuses (batterie d’échangeurs, gestion des fluides). Cette difficulté technologique affecte non seulement les performances énergétiques et les efficacités de transformation des appareils classiques de grandes tailles, mais aussi les réacteurs microstructurés dont les faibles dimensions internes associées à la grande conductivité thermique du matériau constituant les parois du contacteur entraînent souvent l’homogénéité thermique de l’appareil au détriment de la gestion des gradients thermiques. Par ailleurs, les garnissages utilisés dans les séparateurs sont de formes très complexes dans lesquels il est difficile de faire à la fois de la structuration thermique et hydrodynamique. Les systèmes microstructurés basés sur des géométries à plaques semblent offrir une possibilité intéressante de structuration thermique (contrôle et modulation de flux énergétiques pour l’obtention d’un profil thermique spécifique) et hydrodynamique (contrôle des transferts de matière, des temps de séjour, des pertes de charges etc.). Dans cette thèse, les réflexions menées sur ces verrous technologiques ont conduit à la conception d’un microcontacteur à film tombant. Ce microprocédé a été caractérisé d’un point de vue thermique et hydrodynamique. Une étude de faisabilité sur le potentiel de ce microcontacteur à séparer un mélange binaire d’alcools (ethanol/n-propanol) a été menée, ses performances ont été expérimentalement évaluées d’un point de vue qualitatif (pureté du distillat et du soutirat) et quantitatif (rapports des débits entrant et sortant), mais aussi en intégrant la notion d’exergie compositionnelle, également appelée puissance de séparation
In many processes of mass transformation, entropic degradations (and energy consumptions which results from) can be minimized by distributing heat flows in all process volume rather than boundaries (example: diabatic distillation). However it is difficult to control and impose thermal gradients on small scales because of their complexity and high costs (exchangers, fluids). This technological difficulty affects not only the performances and energy efficiencies of conventional devices (macro scales) but also small devices (e.g. microstructured reactors). Indeed, compact equipments with small dimensions generate some difficulties. First, the driving force inducing liquid flow by gravity is very small. Second, small size and high thermal conductivity of the material induce thermal homogeneity instead of managing temperature gradients in the system. In many separators, the used packing material has complex forms that make difficult thermal and hydrodynamic structurations. Microstructured devices, based on microchannel plate technologies, offer an interesting possibility of thermal structuration (control and modulation of energy fluxes) and hydrodynamics control (e.g. mass transfer, residence times, pressure drop etc). In this thesis, many discussions on these technological barriers led to the design of a new microstructured falling film contactor. The aim of the present work is to study heat transfer phenomena and liquid hydrodynamics in this device and, investigates the separation feasibility of a binary mixture of ethanol and n-propanol. Microcontactor performances were experimentally evaluated in terms of quality (bottom and top concentrations) and quantity (bottom and top flow rate ratios). To fully characterize contactor performances, the separation power concept (also called compositional exergy) was integrated

APA, Harvard, Vancouver, ISO, and other styles

32

Lounaci, Malika. "Systèmes microfluidiques pour la cristallisation des protéines : apports technologiques à la compréhension du processus et influence de la hauteur des canaux." Paris 6, 2009. http://www.theses.fr/2009PA066193.

Full text

Abstract:

L’objectif de cette thèse était de mettre au point des dispositifs microfluidiques pour la cristallisation de protéines, de proposer des solutions au criblage des conditions de cristallisation et enfin de contribuer à la compréhension du processus physico-chimique de cristallisation dans un système confiné. Nous avons décrit les techniques de microfabrication, la réalisation de microvannes ainsi que les dispositifs multicouches. Une mise au point d’une plateforme permettant l’observation du processus de cristallisation et le contrôle des microvannes ont été réalisés. Nous avons apporté des solutions aux problématiques rencontrées telles que le boitier à deux compartiments pour une meilleure conservation des cristaux, la méthode d’aspiration avec un minimum d’échantillon sans volume mort ainsi que les dispositifs à trois couches. Enfin, nous avons étudié l’influence de la hauteur du microcanal sur la cristallisation du lysozyme. Nous avons démontré que le nombre de centres de nucléation, la taille des cristaux ainsi que le processus cinétique de la cristallisation dépendent de la hauteur du canal. Nous avons, enfin, proposé une méthode de cristallisation autorisant le découplage de la nucléation et de la croissance cristalline
The objective of this thesis was to perfect Microfluidic devices for the crystallization of proteins, to offer solutions for the screening of the conditions of crystallization and finally to contribute to understanding the physicochemical process of crystallization in a Microfluidic device. We detailed the techniques of microfabrication, the realization of microvalves as well as the multi-layered chips. A platform allowing the observation of the process of crystallization and the control of microvalves were accomplished. We brought solutions in met problems such as the box divided in two compartments for a better conservation of crystals, the method of aspiration with a minimum of sample without dead volume as well as three-layered chips. Finally, we studied the influence of the height of the microchannel on the crystallization of the lysozyme. We showed that the number of centers of nucleation, the size of crystals as well as the kinetic process of crystallization depends on the height of the channel. We offered, finally, a method of crystallization allowing decoupling the nucleation and crystals growth

APA, Harvard, Vancouver, ISO, and other styles

33

Jasiulionis, Jaqueline Andréa Espósito. "Projeto e avaliação de desempenho de torres de resfriamento de água utilizando redes neurais artificiais = Design and analysis of cooling towers using neural netwoks." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266673.

Full text

Abstract:

Orientador: Roger Josef Zemp
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-21T01:23:18Z (GMT). No. of bitstreams: 1 Jasiulionis_JaquelineAndreaEsposito_M.pdf: 15957742 bytes, checksum: f23f7bfae46e12833b047fae94479804 (MD5) Previous issue date: 2012
Resumo: Em muitos processos há necessidade de remover a carga térmica de um dado sistema e utiliza-se, na maioria dos casos, a água como o fluido de resfriamento. Devido à sua crescente escassez e preocupação com o meio ambiente, além de motivos econômicos, a água "quente" que sai desses processos, deve ser aproveitada. Para tanto, ela passa por uma torre de resfriamento e retorna ao processo. Este trabalho descreve um procedimento para avaliar o desempenho térmico de torres de resfriamento, em duas configurações distintas (escoamento contracorrente e escoamento cruzado), utilizando redes neurais artificiais. A vantagem do procedimento proposto é a possibilidade da avaliação direta do desempenho de uma torre sem a complexidade do uso de procedimentos iterativos para convergência nem a necessidade de rotinas de propriedades físicas e psicrométricas. A avaliação do desempenho é feita pela determinação da temperatura de saída da água para um conjunto de parâmetros de entrada (propriedades de corrente da água e do ar na entrada da torre, dimensões e propriedades do recheio), ou determinação da característica do recheio para uma torre existente, em função das condições operacionais. Para a situação de projeto o procedimento permite estimar a vazão de ar ou altura necessária para a torre satisfazer uma condição operacional exigida. O procedimento proposto se mostrou particularmente eficiente para torres com escoamento cruzado, onde o método tradicional de simulação exige a decomposição da torre em um número elevado de células, cada um como um procedimento iterativo para cálculo do balanço de massa e energia. A rede rendeu ótimos resultados quando usada para predizer a temperatura de saída da água e o coeficiente de transferência de massa. Os resultados mostram que a RNA pode fornecer com precisão o desempenho térmico da torre de resfriamento
Abstract: In many industrial environments it is necessary to remove the heat load from a given system and in most cases water is used as the coolant. Due to its increasing scarcity and concerns for the environment, and economic reasons, the "hot" water coming out of these processes must be reused. To do so, it passes through a cooling tower and returns to the process. This paper describes a procedure for evaluating the thermal performance of cooling towers in two different configurations (counter flow and cross flow), using artificial neural networks. The advantage of the proposed procedure is the possibility of direct assessment of the performance of a tower without the complexity due to the required convergence of the iterative procedure or the need for physical properties and psychrometric routines. The performance evaluation is made by computing the temperature of the water outlet for a set of input parameters (flow properties of water and air near the tower, dimensions and properties of the filling), or computing the characteristic of the filling for a existing tower, depending on operating conditions. For the project situation, the procedure allows for the estimate of the air flow or the tower height needed to meet a required operating condition. The proposed procedure proved particularly effective in cross-flow towers, where the traditional method of simulation requires the decomposition of the tower in a large number of cells, each as an iterative procedure for calculating the mass balance and energy. The network yielded excellent results when used to predict the exit temperature of the water and the coefficient of mass transfer. The results show that the RNA can accurately provide the thermal performance of the cooling tower
Mestrado
Sistemas de Processos Quimicos e Informatica
Mestra em Engenharia Química

APA, Harvard, Vancouver, ISO, and other styles

34

Munier, Laurent. "Simulations expérimentale et numérique des effets retardés d'une explosion en milieu clos et en présence de produits liquides." Thesis, Aix-Marseille 1, 2011. http://www.theses.fr/2011AIX10091/document.

Full text

Abstract:

Peut-on modéliser de manière fiable les effets collatéraux (en termes de quantité ou concentration de produits éjectés) et les conséquences d’une explosion en milieu clos, et en présence de produits chimiques liquides ? Pour répondre à cette vaste question, qui soulève spontanément de nombreux sous-problèmes, les travaux de thèse se sont déroulés en trois temps : 1/une étude qualitative et semi-quantitative du scénario général, afin de comprendre le déroulement chronologique des évènements, et d’émettre les hypothèses nécessaires à une modélisation, 2 /L’étude systématique des effets d’une explosion en milieu clos, en présence ou non de produits liquides. Avant de modéliser la dégradation du produit liquide soumis à une température et à une pression élevées, les expérimentations préliminaires ont en effet fait apparaître la nécessité de quantifier dans le temps et dans l’espace, les effets thermiques et mécaniques d’une explosion à volume constant, 3/L’élaboration de modèles 0D(t) à partir des conclusions précédentes afin, d’une part, d’estimer la durée de vie d’une phase liquide dans un environnement thermodynamique contraint et, d’autre part, de démontrer la possibilité de modéliser le problème global de manière réduite. En effet, le terme source d’un tel évènement ne peut être modélisé par une libération ponctuelle de produit : il s’agit d’une libération étendue dans le temps, par le biais d’un écoulement chaud a priori diphasique et de débit variable. Les couplages des phénomènes, observés expérimentalement, rendent nécessaires : 1 - Une modélisation instationnaire de l’évolution de la pression et une estimation du niveau de température atteint dans le volume d’étude, après détonation d’une charge explosive, 2 - Une modélisation de la libération de la phase liquide dans l’enceinte, sous forme de gouttes millimétriques ou de gouttelettes microniques 3 - Une modélisation instationnaire des transferts couplés de masse et d’énergie entre la phase liquide et la phase gazeuse en présence et prise en compte d’éventuelles réactions chimiques à haute pression et haute température 4 - Et enfin, une modélisation instationnaire des rejets à la brèche. L’étude d’une explosion à volume constant a montré qu’il est possible de modéliser de manière simple la montée continue en pression de l’enceinte par une fonction exponentielle croissante. Pour une configuration de référence donnée – explosion d’une sphère d’explosif dans un parallélépipède – la valeur maximale de pression est directement proportionnelle au taux de chargement en explosif, sur l’intervalle [0,01 – 0,6] kg/m3. Le passage à une géométrie différente ou plus complexe demande l’introduction d’un coefficient correctif pour traduire l’amplification (ou l’atténuation) de la combustion turbulente des produits de détonation avec l’air ambiant. En ce qui concerne le champ de température par contre, notre analyse a montré qu’il coexiste des zones chaudes et des zones dites « froides » et que la valeur de température homogène finale calculée à partir d’un code thermochimique ne peut constituer qu’une simple indication. Seule une estimation du volume respectif de ces zones a été proposée ici. Nous avons établi que les propriétés physico-chimiques des produits stockés sont un point clef du problème et on suppose ces données connues pour une gamme de produits chimiques liquides à pression ambiante, communément utilisés dans l’industrie. Seul le phénomène d’évaporation a été développé dans ce mémoire. L’introduction de réactions chimiques entre constituants se traduirait dans les modèles par des termes sources supplémentaires liés à l’apparition ou la disparition d’espèces
Is it possible to model collateral effects due to an explosion (on a chemical facility for instance) occuring in a closed volume containing liquid chemical products storage units ?This thesis deals with a zerodimensionnal modelisation of such a 3D complex problem to asses the final thermodynamic state of chemical products released in the atmosphere. Developped sub-models take into account:- the unsteady time histories of the internal overpressure and temperature,- the unsteady liquid ejection (droplets sizes)- the unsteady modelisation of the local heat and mass transfers between the gas phase and the liquid phase- the unsteady ejection process of the resulting multiphase mixture in the environment.Models and sub-models are validated thanks to many experimental results

APA, Harvard, Vancouver, ISO, and other styles

35

To, Lap C. "Nonlinear control techniques in alumina refineries." Curtin University of Technology, School of Chemical Engineering, 1996. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12276.

Full text

Abstract:

Nonlinearities exist in all process control systems. The use of linear control techniques is valid only in a narrow range of operation. Therefore, in this thesis, multivariable nonlinear control techniques are considered. The target process is the single effect evaporative process of the liquor burning unit in Alcoa's alumina refinery in Kwinana and the proposed triple effects unit in the Wagerup refinery. Two types of nonlinear control strategies using differential geometry were studied, namely, the input output linearization (Kravaris and Soroush, 1990) and the input state linearization (Hunt et al, 1983a). The research has successfully demonstrated the superiority and simplicity of the nonlinear controller through simulations and plant implementations. An integrated software package using MAPLE V.3 as the computing environment was developed to automate the solution algorithms and to graphically simulate the closed loop dynamics of different processes using the two nonlinear control strategies.The issue of robustness of the nonlinear controller was addressed by developing a procedure called uncertainty vector adjustment. The effectiveness of the new strategy was successfully demonstrated on the simulated liquor burning process. Furthermore, the stability of the adjustment technique was proved and its theoretical bounds were established using Lyapunov function analysis.A comparative study of geometric nonlinear filter and extended Kalman filter was conducted to reduce the requirement of full state feedback necessary for nonlinear control using either input output linearization or input state linearization. The simulation of the single effect evaporation unit of the liquor burning process showed that the geometric nonlinear filter is superior to the extended Kalman filter in terms of nonlinear tracking performances.The plant trials of the input output linearization ++
in Alcoa's Kwinana alumina refinery demonstrated the practicability and feasibility of implementing nonlinear control in an industrial setting and also fostered a closer gap between academia and industry. The trials established guidelines for implementing a global linearizing controller on site, including conversion of the relevant constraints and the output of an industrial proportional and integral controller to the equivalent proportional and integral action required by the nonlinear controller. The results showed that the performance of the nonlinear controller was better than the current linear controller on site in terms of responsiveness and resistance to disturbances. Hence, the nonlinear control strategy enables the process to settle faster.All in all, efforts have been made in this thesis to minimise the use of abstract mathematical language and, in some cases, simplify the language so that nonlinear control theory can be understood by a wider range of audience, especially industrial practitioners. It is hoped that the insights provided in the dissertation will encourage more industrial implementations of nonlinear controllers and forge more interaction to close the widening gap between academic and industrial practice in process control.Keywords: nonlinear control, differential geometry, symbolic algebra, evaporator process, uncertainty vector adjustment, geometric nonlinear filter.

APA, Harvard, Vancouver, ISO, and other styles

36

Tran, Thanh Danh. "Rôle de la microstructure des sols argileux dans les processus de retrait-gonflement : de l’échelle de l’éprouvette à l’échelle de la chambre environnementale." Thesis, Paris, ENMP, 2014. http://www.theses.fr/2014ENMP0002/document.

Full text

Abstract:

Le processus de retrait-gonflement des sols argileux est à l'origine des dommages au bâti durant les périodes de sécheresse. Dans cette thèse, les processus de retrait-gonflement de deux formations de sol argileux en France qui sont les Argiles Plastiques du Sparnacien et l'argile d'Héricourt du Lias sont étudiés à différentes échelles et différents états (intact, remanié, compacté et traité à la chaux) en considérant spécialement le rôle de la microstructure. Pour ce faire, une partie de la recherche est réalisée sur la caractérisation des sols étudiés pour analyser leurs propriétés minéralogiques, microstructurales, géotechniques et hydriques par rapport à leur propriété de retrait-gonflement. La deuxième partie de la recherche est consacrée à l'analyse des processus de gonflement, de retrait, de fissuration des sols au cours d'un cycle simple ou de cycles répétés d'humidification-séchage à l'échelle de l'éprouvette. Les processus de retrait-gonflement de sol à une échelle plus grande sont étudiés dans la troisième partie en réalisant les essais d'infiltration et d'évaporation dans une chambre environnementale. Les résultats obtenus mettent en évidence les différences de comportement au retrait-gonflement pour différents états des sols étudiés. Les minéraux argileux ainsi que le quartz, les carbonates et des hydrates, mais aussi la microstructure des sols contrôlent ces phénomènes de retrait-gonflement lors des échanges hydriques. Tous les changements de volume de sol argileux au cours de gonflement-retrait sont gouvernés principalement par la famille de pores inter-agrégats naturels. Ces résultats sont apportés par les analyses microstructurales porosimétriques et au MEB
The shrink-swell process of clayey soils is causing damage to the structures during periods of drought. In this thesis, the shrink-swell process of two clayey soils in France that are the Plastic Clays of Sparnacian age and Héricourt clay of Lias is studied at different scales and different conditions (intact, remoulded, compacted and lime treated) by insisting on the role of microstructure. To do this, a part of the study is carried out on the characterisation of soils studied to analyse their mineralogical, microstructural, geotechnical and hydraulic properties in relation with their shrink-swell property. The second part of the study focuses on the analysis of swelling, shrinkage, cracking processes of soil during a single cycle or repeated wetting-drying cycles at specimen scale. The shrink-swell process of soil at a larger scale is studied in the third part by performing infiltration and evaporation tests in the environmental chamber. The results highlight the difference in the shrink-swell behavior at different conditions of soils studied and emphasize the importance of the presence and nature of clay minerals also quartz, hydrates and microstructure of soil to the shrinkage and swelling during water exchange. All changes in the volume of clayey soil during shrinkage and swelling are mainly governed by natural inter-aggregate pores, which are showed by microstructural analyses of MIP and SEM tests

APA, Harvard, Vancouver, ISO, and other styles

37

Euhus, Daniel D. "Nucleation in bulk solutions and crystal growth on heat-transfer surfaces during evaporative crystallization of salts composed of NaCO and NaSO." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5401.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Euhus, Daniel D. "Nucleation in bulk solutions and crystal growth on heat-transfer surfaces during evaporative crystallization of salts composed of Na₂CO₃ and Na₂SO₄." Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04082004-180136/unrestricted/euhus%5Fdaniel%5Fd%5F200312%5Fphd.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Souza, Andr? Luis Rodrigues. "Estabiliza??o de mol?culas bioativas presentes em suco de camucamu (Myrciaria d?bia (H.B.K) Mc Vaugh) pela integra??o dos processos de osmose inversa, evapora??o osm?tica e atomiza??o." Universidade Federal Rural do Rio de Janeiro, 2012. https://tede.ufrrj.br/jspui/handle/jspui/1562.

Full text

Abstract:

Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-04-27T13:51:34Z No. of bitstreams: 1 2012 - Andr? Luis R. de Souza.pdf: 1971622 bytes, checksum: 5237bc23d365c59e774d9f8776efabf1 (MD5)
Made available in DSpace on 2017-04-27T13:51:34Z (GMT). No. of bitstreams: 1 2012 - Andr? Luis R. de Souza.pdf: 1971622 bytes, checksum: 5237bc23d365c59e774d9f8776efabf1 (MD5) Previous issue date: 2012-03-06
Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq
Camu-camu is a native fruit from the Amazonian region, cultivated in the margins of rivers, lakes and Amazonian creeks called igarap?s. It is known as one of the fruit with the highest content of vitamin C. Reverse osmosis is a membrane concentration process in which the applied pressure is higher than the juice osmotic pressure. Such process favors the solvent permeation from the region with the highest concentration to the one with the lowest. Osmotic evaporation is another membrane concentration process in which a porous hydrophobic membrane separates the solution that is going to be concentrated from a concentrate brine solution. Microencapsulation is the process in which an active agent is entrapped by means of a polymer cover. Such process promotes the release of these active agents under specific conditions. The aim of this work is to evaluate the use of membrane separation processes and microencapsulation for the processing of camu-camu fruits. The camu-camu pulp, which has been obtained through the depulping of camu-camu fruits, was first centrifuged, in order to decrease its suspended solids content, and clarified by microfiltration with polysulfone membranes. Six clarification processes have carried out at 2.5 bar transmembrane pressure and 45?C. The clarified juice was concentrated by reverse osmosis at 60 bar and 20 ?C. The avarage permeate flux has been of 11.3 L/hm2. The preconcentrated juice had 28.8?Brix and the concentration degree of the process was 3.8. The pre-concentrated juice has been concentrated by osmotic evaporation in a laboratorial system with polytetrafluoroethylene membrane. The process presented an average pemeate flux of 2.4 Kg/hm2. The soluble solids content of the concentrated juice was of 56.6 ?Brix, presenting a concentration degree of 1.98. The retentate fraction of the microfiltration process was microencapsulated in a spray dryer. Three encapsulation agents were evaluated: starch, maltodextrin and the mixture of both. The values presented for the physicochemical caracterization of the pre-concentrated and concentrated camu-camu juices indicate that there has been an increase both in the physical characteristics of the juice, such as soluble solids, total solids and acidity, and in the concentration of camu-camu bioactive compounds. The dehydrated camu-camu juice presented a high concentration of bioactive substances. Nevertheless, there has been no stability of such compounds during storage. Through the results obtained in the present work, it is possible to observe that the integration of membrane processes proved efficient in the concentration of camu-camu juice, with a final product of high nutritional value
O camu-camu ? um fruto nativo da regi?o amaz?nica, cultivado as margens de rios, lagos e igarap?s. ? reconhecido como um dos frutos com um dos maiores teores de vitamina C. Osmose inversa ? o processo de concentra??o por membranas onde a press?o aplicada ? maior que a press?o osm?tica do suco, favorecendo a permea??o do solvente da regi?o de maior concentra??o para regi?o de menor concentra??o. Evapora??o osm?tica ? um outro processo de concentra??o, onde uma membrana hidrof?bica porosa separa a solu??o que ser? concentrada e uma salmoura concentrada. A microencapsula??o ? o processo onde um agente ativo ? protegido por meio de uma cobertura de pol?meros, ocorrendo a libera??o desses agentes ativos em condi??es espec?ficas. O objetivo desta disserta??o foi avaliar o uso dos processos de separa??o com membranas e microencapsulamento para o processamento de suco de camu-camu. Os frutos de camu-camu foram despolpados, sendo o suco submetido a centrifuga??o, com o objetivo de reduzir os s?lidos em suspens?o, e posteriormente clarificado por microfiltra??o em um sistema de membranas de polissulfona. Foram realizados seis processos de clarifica??o a 2,5 bar e 45?C. O suco clarificado foi pr?-concentrado por osmose inversa a 60 bar e 20 ?C. O fluxo permeado m?dio foi de 11,3 L/hm2. O suco pr?-concentrado apresentou teor de s?lidos sol?veis de 28,8?Brix e grau de concentra??o de 3,8. O suco pr?-concentrado foi processado por evapora??o osm?tica em um sistema laboratorial constitu?do por membranas de politetrafluoretileno. O processo apresentou fluxo m?dio permeado de 2,4 kg/hm2. O teor de s?lidos sol?veis do suco concentrado foi de 56,6 ?Brix, apresentando um grau de concentra??o de 1,98. O processo de microencapsula??o da fra??o retida do suco de camucamu foi realizado em um spray dryer Buchi Modelo B-190. Foram realizados tr?s ensaios com tr?s formula??es diferentes: mistura entre amido e maltodextrina, somente amido e somente maltodextrina. Os valores apresentados para a caracteriza??o f?sico-qu?mica do suco de camu-camu pr?-concentrado e concentrado indicam que houve um aumento nos s?lidos sol?veis e totais e da acidez, bem como no teor das subst?ncias bioativas do camucamu. O suco de camu-camu desidratado apresentou alto teor de subst?ncias bioativas, onde a estabilidade desses compostos durante o per?odo de armazenamento n?o foi alcan?ada. Observa-se que a integra??o dos processos com membranas se mostrou eficaz na concentra??o do suco de camu-camu, obtendo um produto com alta qualidade nutricional.

APA, Harvard, Vancouver, ISO, and other styles

40

Li, Hailong. "Thermodynamic Properties of CO2 Mixtures and Their Applications in Advanced Power Cycles with CO2 Capture Processes." Doctoral thesis, KTH, Energiprocesser, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9109.

Full text

Abstract:

The thermodynamic properties of CO2-mixtures are essential for the design and operation of CO2 Capture and Storage (CCS) systems. A better understanding of the thermodynamic properties of CO2 mixtures could provide a scientific basis to define a proper guideline of CO2 purity and impure components for the CCS processes according to technical, safety and environmental requirements. However the available accurate experimental data cannot cover the whole operation conditions of CCS processes. In order to overcome the shortage of experimental data, theoretical estimation and modelling are used as a supplemental approach. In this thesis, the available experimental data on the thermodynamic properties of CO2 mixtures were first collected, and their applicability and gaps for theoretical model verification and calibration were also determined according to the required thermodynamic properties and operation conditions of CCS. Then in order to provide recommendations concerning calculation methods for engineering design of CCS, totally eight equations of state (EOS) were evaluated for the calculations about vapour liquid equilibrium (VLE) and density of CO2-mixtures, including N2, O2, SO2, Ar, H2S and CH4. With the identified equations of state, the preliminary assessment of impurity impacts was further conducted regarding the thermodynamic properties of CO2-mixtures and different processes involved in CCS system. Results show that the increment of the mole fraction of non-condensable gases would make purification, compression and condensation more difficult. Comparatively N2 can be separated more easily from the CO2-mixtures than O2 and Ar. And a lower CO2 recovery rate is expected for the physical separation of CO2/N2 under the same separation conditions. In addition, the evaluations about the acceptable concentration of non-condensable impurities show that the transport conditions in vessels are more sensitive to the non-condensable impurities and it requires very low concentration of non-condensable impurities in order to avoid two-phase problems. Meanwhile, the performances of evaporative gas turbine integrated with different CO2 capture technologies were investigated from both technical and economical aspects. It is concluded that the evaporative gas turbine (EvGT) cycle with chemical absorption capture has a smaller penalty on electrical efficiency, while a lower CO2 capture ratio than the EvGT cycle with O2/CO2 recycle combustion capture. Therefore, although EvGT + chemical absorption has a higher annual cost, it has a lower cost of electricity because of its higher efficiency. However considering its lower CO2 capture ratio, EvGT + chemical absorption has a higher cost to avoid 1 ton CO2. In addition the efficiency of EvGT + chemical absorption can be increased by optimizing Water/Air ratio, increasing the operating pressure of stripper and adding a flue gas condenser condensing out the excessive water.
QC 20100819

APA, Harvard, Vancouver, ISO, and other styles

41

Mykhailenko, V., and A. Vartansan. "Calculatoin of economic losses of unintentionally produced persistent organic pollutants (POPs) from centralized heating in Odessa." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/45338.

Full text

Abstract:

Persistent Organic Pollutants (POPs) are a set of toxic chemicals that are persistent in the environment and able to last for several years before breaking down. POPs circulate globally and chemicals released in one part of the world can be deposited at far distances from their original source through a repeated process of evaporation and deposition. This makes it very hard to trace the original source of the chemical [1].

APA, Harvard, Vancouver, ISO, and other styles

42

Тертишник, О. І. "Удосконалення технологічного процесу виготовлення камери випаровування 516.08.001 шляхом застосування високопродуктивної технологічної оснастки." Master's thesis, Сумський державний університет, 2018. http://essuir.sumdu.edu.ua/handle/123456789/72019.

Full text

Abstract:

Робота присвячена питанням проектування технологічного процесу виготовлення камери випаровування. Проаналізовано технічні вимоги на виготовлення деталі. Визначено тип виробництва, обгрунтований спосіб отримання заготовки. Спроектовано верстатний пристрій.
Работа посвящена вопросам проектирования технологического процесса изготовления камеры испарения. Проанализированы технические требования на изготовление детали. Определен тип производства, обоснован способ получения заготовки. Спроектировано станочное приспособление.
The work is devoted to the designing of the technological manufacturing process of evaporation chamber. Technical requirements for the manufacture of part was analyzed. The type of production was determined, the method for producing the blank was justified. The fixture was designed.

APA, Harvard, Vancouver, ISO, and other styles

43

Kuchi, Venkateswarlu. "Development of an innovative ISOL system for the production of short-lived neutron-deficient ions." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMC233/document.

Full text

Abstract:

Dans le cadre de l'installation GANIL / SPIRAL-1, un système innovant de source d'ions cible (TISS) a été conçu pour produire des nouveaux faisceaux d'ions radioactifs compétitifs et déterminer dans quelle mesure il est possible d'améliorer les performances de production par l’optimisation de l’ensemble cible-source (ECS) d’ions dédié à la production d'un faisceau d'ions radioactifs spécifique.L'isotope d'alcalin de courte durée de 74Rb ( demi-vie = 64.8 ms) a été choisi comme cas d’école.En étudiant et en améliorant les processus impliqués dans le fonctionnement de l’ECS, i.e. production dans la cible par réaction fusion-évaporation, implantation dans- et sortie du graphite, effusion et ionisation, une efficacité de transformation atome-ion de 75% est attendue, menant à un taux d'ions de l'ordre de 104 pps à la sortie de l’ECS.Les performances estimées permettraient à l'installation GANIL / SPIRAL-1 de délivrer des faisceaux de 74Rb et 114Cs avec des intensités compétitives, jamais atteintes dans d'autres installations.Le dispositif de production a été développé sur la base de mon travail, pour répondre aux objectifs de physique et aux conditions d'opération de SPIRAL-1. L'efficacité, la fiabilité et donc la simplicité étaient essentielles. Le système répond à ces exigences
In the frame of GANIL/SPIRAL-1 facility, an innovative target ion source system (TISS) has been designed in order to produce new competitive radioactive ion beams, and to determine to which extent it is possible to improve the production performances by optimizing a target ion source system dedicated to the production of a specific radioactive ion beam.The short-lived alkali isotope of 74Rb (half-life = 64.8 ms) has been chosen as a challenging case study.By studying and improving the processes involved in the TISS designed, i.e. in-target production by fusion-evaporation, implantation in and release out of graphite, effusion, and ionization, an atom-to-ion transformation efficiency of 75% was predicted, leading to an ion rate of the order of 104 pps at the exit of the TISS.The estimated performances would allow the GANIL / SPIRAL-1 installation to deliver beams of 74Rb and 114Cs with competitive intensities never reached in other installations.The production device was developed based on my work, to cope with physics objectives and with the conditions of the SPIRAL-1 operation. Efficiency, reliability and thus simplicity were essential. The system meets these requirements.The instrumentation needed for tests existed or have been specifically designed. The TISS has been built, assembled and partly tested.In parallel, issues have been addressed to answer related questions about sticking times, resistivity, and emissivity, to get inputs for the design of the TISS.Expected results with alkali allow thinking that the transposition of the principle to the production of neutron-deficient short-lived isotopes of noble gases and eventually metals could be performing

APA, Harvard, Vancouver, ISO, and other styles

44

Diel, Cristiano Luiz. "Modelagem matemática do processo de evaporação do licor negro proveniente do sistema de lavagem da polpa celulósica." Universidade Estadual do Oeste do Parana, 2013. http://tede.unioeste.br:8080/tede/handle/tede/1851.

Full text

Abstract:

Made available in DSpace on 2017-07-10T18:08:03Z (GMT). No. of bitstreams: 1 Cristiano Luiz Diel.pdf: 3361169 bytes, checksum: 272490d70ac95c5008fc77d50f4431d0 (MD5) Previous issue date: 2013-02-22
Klabin Fabricadora de Papel e Celulose S/A
The pulp and paper industries are major consumers of energy. The plant of black liquor evaporation consumes significant portion of this energy. Any effort to improve their energy efficiency is beneficial to the industry. The computer simulation is a powerful tool to aid the understanding of industrial processes and may help identify mechanisms involved in the prediction of responses to changes in operating conditions and optimization of process control. The objective of this work is the development of a mathematical model phenomenological representing the evaporation plant of Klabin Papéis Monte Alegre (KPMA) and the use of it to study and improve operational conditions of the plant. To achieve this goal, firstly it was developed a simplified model based on the work of other authors. The model was built in Maple ® platform. The model was built from mass and energy balances and phase equilibrium equations. Correlations were used to estimate properties, e. g. boiling point raise, enthalpies of the liquor, steam and condensate. The model reproduced well the results of the authors, with the largest percentual error equal to 5.5% and most of the parameters with percentual errors less than 1%. The model was adapted to represent the first effect of evaporation plant of KPMA. Historical operating data were used to compare the model results. Good results were found for temperature and solid content of the liquor. Good results were found for mass flows in some effects, but the model could not effectively predict the mass flow of all effects and the variables related to the flash tanks. The differences are attributed mainly to considerations of steady state and saturated vapor with no entrainment of particles in the liquor and the use of literature correlations to predict the properties of the liquor that do not correspond to the liquor used.
As indústrias de papel e celulose são grandes consumidoras de energia. A planta de evaporação de licor negro consome parte significativa dessa energia. Qualquer esforço no sentido de melhorar sua eficiência energética é benéfico para a indústria. A simulação computacional é uma ferramenta poderosa no auxílio da compreensão de processos industriais, podendo auxiliar na identificação de mecanismos envolvidos no processo, na predição de respostas a mudanças de condições de operação e na otimização do controle de processos. Assim, o objetivo do presente trabalho é o desenvolvimento de um modelo matemático fenomenológico representando a planta de evaporação da Klabin Papéis Monte Alegre (KPMA) e a utilização do mesmo para estudo e melhoria das condições operacionais da planta. Para atingir a este objetivo, primeiramente foi desenvolvido um modelo simplificado baseado no trabalho de outros autores. O modelo foi construído em plataforma Maple®. O modelo foi construído a partir de balanços de massa e energia e equações de equilíbrio de fases. Foram utilizadas correlações para estimar propriedades, e.g. elevação do ponto de ebulição, entalpias do licor, vapor e condensado. O modelo reproduziu bem os resultados dos autores, sendo o maior desvio percentual igual a 5,5% e a grande maioria dos parâmetros com desvio percentuais inferiores a 1%. O modelo foi adaptado para representar o primeiro efeito da planta de evaporação da KPMA. Dados históricos de operação foram utilizados para comparação dos resultados do modelo. Foram encontrados bons resultados para os teores de sólidos e temperaturas do licor, bem como para as vazões para alguns dos evaporadores. O modelo não pôde predizer com eficácia as vazões de todos os evaporadores e das variáveis referentes aos tanques de expansão de licor. As diferenças encontradas são atribuídas principalmente às considerações de regime estacionário e de vapor saturado com ausência de arraste de partículas no licor, bem como da utilização de correlações da literatura para predizer as propriedades do licor que não correspondem ao licor utilizado na evaporação.

APA, Harvard, Vancouver, ISO, and other styles

45

Buckley-Smith, Marion. "The Use of Solubility Parameters to Select Membrane Materials for Pervaporation of Organic Mixtures." The University of Waikato, 2006. http://hdl.handle.net/10289/2625.

Full text

Abstract:

Pevaporation is a method for separating volatile components from liquid mixtures at ambient temperatures. The paint processing industry uses Hansen solubility parameters (HSP) to indicate polymer solubility. The potential of this method to predict solvent-polymer affinity was investigated for screening potential membrane materials for the pervaporation of a model solution containing linalool and linalyl acetate (major components of lavender essential oil), in ethanol. Published HSP values were collated for various polymers, and statistically analysed to determine variations in HSP values for polymer species. An investigation of published research into pervaporation of organic/organic binary solutions separated by homogeneous membranes indicated that the solvent whose HSP value was closest to that of the polymer would preferentially permeate. This relationship did not always hold for halogenated solvents or aqueous/organic solutions. Conflicting literature regarding the relationship between solvent uptake by polymers and HSP relative energy differences was resolved using a logarithmic relationship between these two parameters. The following membranes were selected, using their HSP to indicate their potential to interact with lavender oil components: Polyamide (PA: 26.9 micro;m), Polycarbonate (PC: 20.5 micro;m), Poly(ether imide) (PEI: 29.2 micro;m), Poly(ether sulphone) (PES: 27.6 micro;m), Polyethylene (HDPE: 10 micro;m, LDPE: 13-30 micro;m), Polyimide (PI: 30.0 micro;m), Poly(methyl methacrylate) (PMMA: 50 micro;m), Polypropylene (PP: 15.9 micro;m), and Poly(tetrafluoro ethylene) (PTFE: 26.7 micro;m). The HSP (dispersive, polar hydrogen bonding components) for each membrane were calculated using the mean value obtained from swelling experiments, group contribution (calculated using Hoftyzer-Van Krevelen, Hoy and Beerbower methods), refractive indices (dispersive component), dielectric constants (polar component), and published HSP values. Pervaporation experiments investigated the effect of membrane thickness, process temperature, permeate pressure, impinging jet heights, feed flow rates and concentrations, and pre-soaking the membrane; on flow rate and selectivity in a polyethylene membrane. Membrane thickness was the dominant factor in membrane selectivity; the thinnest membranes (11.3-14.8 micro;m) had much poorer selectivity than membranes gt;24.7 micro;m. Temperatures between 22-34ordm;C, permeate pressure lt;10 kPa, impinging jet heights between 0.36-3.36 mm, feed flow rates between 541-1328 mL/min and concentrations between 1.78-6.01 % v/v of linalool and linalyl acetate in ethanol did not significantly affect selectivity. Flow rates increased with operating temperature, permeate pressure, and impinging jet heights. However, feed flow rate and concentration had no effect on membrane flux rate. Pre-soaking the membrane reduced the time to reach steady-state. Selected membranes were further investigated under standard operating conditions (permeate temperature 30ordm;C, permeate pressure lt;10 kPa, impinging jet height 1.36 mm, feed flow rate 804 mL/min and feed concentration of 5% v/v of linalool and linalyl acetate in ethanol). PMMA completely disintegrated in feed solution, and PC was too brittle to make an effective homogeneous membrane. PA, PC, PEI and PTFE had the highest efficiency (selectivity x flow rate) in their homogeneous form. However, PEI, PI and PTFE had the greatest selectivity, thus further trials should be done to improve stability and flow rates through these membranes. Pervaporation selectivity did not always follow trends predicted by HSP. Although polymers such as PA, PEI, PES, and PI preferentially permeated linalool as predicted, PC, PP and PTFE did not preferentially permeate linalyl acetate. This may have been due to the difference in size and diffusivity of these molecules (linalyl acetate, the larger molecule, did not follow the sorption selectivity predictions), or reliability of literature HSP values and those calculated by group contribution. This research shows that HSP is a good screening method for pervaporation membranes, especially where the molecules being separated are of comparable size. Polymers that have HSP close to the desired component and not to other components tend to have the best selectivity and flux characteristics. However, diffusion is an important factor, and is not completely accounted for by HSP. Recommendations for further research include: carrying out pervaporation analyses of selected polymers using pure lavender essential oil; modifying polymers to form asymmetric or composite membranes with improved permeation characteristics; and potential use of thin channel inverse gas chromatography to determine a more accurate HSP which includes diffusivity.

APA, Harvard, Vancouver, ISO, and other styles

46

Ausmeel, Erik, and Botvid Gannholm. "Dataanalys av en ny avfrostningsrutin på en kyl- och frysanläggning : En studie gjord hos Freezing Food Småland Öland AB." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-105008.

Full text

Abstract:

Den här rapporten handlar om en ändring i livsmedelsföretaget Freezing Food Småland Öland AB:s avfrostningsrutin för deras förångare i frysrummet. Ändringen gick ut på att avfrostningstiden och maxtemperaturen sänktes samt att tiden mellan avfrostningarna nu sker varannan i stället för varje natt. Syftet var att undersöka om ändringen av rutinen hade bidragit till en minskad energiförbrukning i förhållande till innan ändringen gjordes genom att också granska andra faktorer än själva avfrostningen som kunde tänkas påverka energiförbrukningen. Metoden gick ut på att insamla och analysera stora datamängder tillhandahållna av företaget för att sedan reducera dem till hanterbara siffror. Även data för lokala utomhustemperaturer samlades in. Med hjälp av detta beräknades medelvärden för en given tidsperiod för energiförbrukning, lagerhållning och utomhustemperatur. Resultatet visade en sänkning av energiförbrukningen, hur stor andel som berodde på avfrostningens ändrade rutiner lämnade undersökningen obesvarat. Utomhustemperaturen bör ha minskat effektbehovet, samtidigt bör lagerhållningen ökat den. Slutsatsen blev att mer tid behövde passera och en ny undersökning behöver framställas efter att avfrostningsrutinen ändrades för att möjliggöra en säkrare bedömning.
This report is about a change in the food company Freezing Food Småland Öland AB’s defrosting routine for their evaporators in the freezer warehouse. The change was that the defrosting time and maximum temperature were reduced and that the time between defrostings now takes place every other night instead of every night. The aim was to examine whether the change in the routine had contributed to a reduction in energy consumption compared to before the change was made by also examining factors other than defrosting itself that might affect energy consumption. The method was to collect and analyze large amounts of data provided by the company and then reduce them to manageable figures. Data for local outdoor temperatures were also collected. This calculated averages for a given time period for energy consumption, warehousing and outdoor temperature. The results showed a decrease in energy consumption, the proportion due to the change in defrosting procedures left the investigation unanswered. The outdoor temperature should have reduced the power requirement, at the same time the storage should have increased it. It was concluded that more time needed to pass,and a new study needed to be produced after the defrosting routine was changed to allow for a safer assessment.

APA, Harvard, Vancouver, ISO, and other styles

47

Lahondère, Chloé. "Stress thermique et thermorégulation chez lez insectes hématophages." Thesis, Tours, 2012. http://www.theses.fr/2012TOUR4029.

Full text

Abstract:

Les insectes sont soumis aux fluctuations thermiques de leur environnement mais disposent d’un panel varié de réponses comportementales, physiologiques et biochimiques pour en minimiser les effets délétères et maintenir leur intégrité physiologique. Ainsi certaines espèces régulent activement leur température interne indépendamment de la température de l’environnement. Si ces insectes peuvent s’affranchir des contraintes thermiques imposées par leur environnement, ceux qui se nourrissent du sang chaud d’hôtes vertébrés endothermes n’ont pas d’autres choix que de se confronter à une situation de stress thermique à chaque prise alimentaire. Le principal objectif de ce travail de thèse est de comprendre comment des insectes hématophages, employant des stratégies alimentaires différentes, gèrent le stress thermique associé au flux massif de chaleur engendré par l’ingestion du repas de sang. Nos résultats montrent que ces insectes ont su s’adapter en développant différentes stratégies de thermorégulation
Insects are submitted to thermal fluctuations of their environment and have developed a wide ranged panel of behavioral, physiological and biochemical responses, to minimize the subsequent deleterious effects and maintain their physiological integrity. Some species actively regulate their internal temperature independently of the temperature of the environment. If these insects can overcome the constraints imposed by their thermal environment, those that feed on warm-blooded vertebrate hosts have no choice but to confront a situation of thermal stress at each feeding event. The main objective of this work is to understand how bloodsucking insects manage heat stress associated with the massive flow of heat generated by the ingestion of the blood meal. Our results show these insects have developed different strategies of thermoregulation to protect themselves from overheating

APA, Harvard, Vancouver, ISO, and other styles

48

Apicella, Fernandez Sergio. "Surface energy modification of metal oxide to enhance electron injection in light-emitting devices : charge balance in hybrid OLEDs and OLETs." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-25097.

Full text

Abstract:

Organic semiconductors (OSCs) present an electron mobility lower by several orders of magnitude than the hole mobility, giving rise to an electron-hole charge imbalance in organic devices such as organic light-emitting diodes (OLEDs) and organic light-emitting transistors (OLETs). In this thesis project, I tried to achieve an efficient electron transport and injection properties in opto-electronic devices, using inorganic n-type metal oxides (MOs) instead of organic n-type materials and a polyethyleneimine ethoxylated (PEIE) thin layer as electron transport (ETLs) and injection layers (EILs), respectively. In the first part of this thesis, inverted OLEDs were fabricated in order to study the effect of the PEIE layer in-between ZnO and two different emissive layers (EMLs): poly(9,9-dioctylfluorene-alt-benzothiadiazole) polymer (F8BT) and tris(8-hydroxyquinolinato) aluminum small molecule (Alq3), based on a solution and thermal evaporation processes, respectively. Different concentrations (0.80 %, 0.40 %) of PEIE layers were used to further study electron injection capability in OLEDs. After a series of optimizations in the fabrication process, the opto-electrical characterization showed high-performance of devices. The inverted OLEDs reported a maximum luminance over 104 cd m-2 and a maximum external quantum efficiency (EQE) around 1.11 %. The results were attributed to the additional PEIE layer which provided a good electron injection from MOs into EMLs. In the last part of the thesis, OLETs were fabricated and discussed by directly transferring the energy modification layer from OLEDs to OLETs. As metal oxide layer, ZnO:N was employed for OLETs since ZnO:N-based thin film transistors (TFTs) showed better performance than ZnO-based TFTs. Finally, due to their short life-time, OLETs were characterized electrically but not optically.

APA, Harvard, Vancouver, ISO, and other styles

49

Westin, Elin M. "Microstructure and properties of welds in the lean duplex stainless steel LDX 2101." Doctoral thesis, KTH, Metallografi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-27387.

Full text

Abstract:

Duplex stainless steels can be very attractive alternatives to austenitic grades due to their almost double strength at equal pitting corrosion resistance. When welding, the duplex alloys normally require addition of filler metal, while the commodity austenitic grades can often be welded autogenously. Over-alloyed consumables are used to counteract segregation of important alloying elements and to balance the two phases, ferrite and austenite, in the duplex weld metal. This work focuses on the weldability of the recently-developed lean duplex stainless steel LDX 2101® (EN 1.4162, UNS S32101). The pitting corrosion resistance of this grade is better than that of austenitic AISI 304 (EN 1.4307) and can reach the level of AISI 316L (EN 1.4404). The austenite formation is rapid in LDX 2101 compared to older duplex grades. Pitting resistance tests performed show that 1-2.5 mm thick laser and gas tungsten arc (GTA) welded LDX 2101 can have good corrosion properties even when welding autogenously. Additions of filler metal, nitrogen in the shielding gas, nitrogen-based backing gas and use of laser hybrid welding methods, however, increase the austenite formation. The pitting resistance may also be increased by suppressing formation of chromium nitrides in the weld metal and heat affected zone (HAZ). After thorough post-weld cleaning (pickling), pitting primarily occurred 1-3 mm from the fusion line, in the parent metal rather than in the HAZ. Neither the chromium nitride precipitates found in the HAZ, nor the element depletion along the fusion line that was revealed by electron probe microanalysis (EPMA) were found to locally decrease the pitting resistance. The preferential pitting location is suggested to be controlled by the residual weld oxide composition that varies over the surface. The composition and thickness of weld oxide formed on LDX 2101 and 2304 (EN 1.4362, UNS S32304) were determined using X-ray photoelectron spectroscopy (XPS). The heat tint on these lean duplex grades proved to contain significantly more manganese than what has been reported for standard austenitic stainless steels in the AISI 300 series. A new approach to heat tint formation is presented; whereby evaporation of material from the weld metal and subsequent deposition on the already-formed weld oxide are suggested to contribute to weld oxide formation. This is consistent with manganese loss from the weld metal, and nitrogen additions to the GTA shielding gas enhance the evaporation. The segregation of all elements apart from nitrogen is low in autogenously welded LDX 2101. This means that filler wire additions may not be required as for other duplex grades assuming that there is no large nitrogen loss that could cause excessive ferrite contents. As the nitrogen appears to be controlling the austenite formation, it becomes essential to avoid losing nitrogen during welding by choosing nitrogen-containing shielding and backing gas.
QC 20101213

APA, Harvard, Vancouver, ISO, and other styles

50

Martínez, Galván Israel Octavio. "Estudio experimental de optimización de una bomba de calor agua-agua empleando propano como fluido de trabajo." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/3344.

Full text

Abstract:

La tesis que a continuación se presenta surge como una respuesta práctica al problema medioambiental relacionado con el empleo de sustancias sintéticas como fluidos de trabajo en muchos de los equipos de climatización comercializados en la actualidad. Con su desarrollo se busca dar alternativas a la creciente demanda de sistemas de climatización eficientes que contribuyan a la optimización de los recursos energéticos. Uno de los objetivos planteados en el desarrollo de la tesis ha sido el diseñar y evaluar experimentalmente el comportamiento de diferentes prototipos experimentales de bombas de calor, particularmente de tipo agua-agua con el uso del propano como refrigerante. La caracterización de los prototipos se llevó a cabo realizando diferentes estudios de carga con la finalidad de determinar la mínima cantidad de propano en cada sistema para obtener las máximas prestaciones en cuanto a COP y capacidad. Los estudios han mostrado que los elementos principales, como el compresor o los intercambiadores de calor presentan mayores rendimientos con el uso del propano en comparación a algunos refrigerantes sintéticos como el R407C. Esto se debe en gran medida a las excelentes propiedades termodinámicas y de transporte del propano, así como a la evolución que este refrigerante tiene a través de los componentes del sistema. En cuanto a la carga óptima de propano, se han obtenido cargas de refrigerante próximas a los 500 gramos, que han permitido obtener coeficientes de operación elevados bajo condiciones de trabajo típicas de calefacción y refrigeración, así como capacidades específicas de refrigeración entre 25 y 33 Wattios por gramo de propano.
Martínez Galván, IO. (2008). Estudio experimental de optimización de una bomba de calor agua-agua empleando propano como fluido de trabajo [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3344
Palancia

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Evaporation processes'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles