Segui questo link per vedere altri tipi di pubblicazioni sul tema: Fouling.
Tesi sul tema "Fouling"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Fouling".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Alharthi, Majed. "Fouling and cleaning studies of protein fouling at pasteurisation temperatures". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4892/.
Testo completoAbstract (sommario):
Fouling and cleaning processes impact industrial production, in terms of economics, product quality, product safety, and plant efficiency. Therefore, optimisation of fouling and cleaning processes is a significant issue, and needs a good understanding of fouling and cleaning kinetics. Ideal monitors should determine the right time when a process run should stop and when a plant will be clean in order to improve the process efficiency. This thesis investigated the fouling and cleaning behaviour of dairy fluids in a plate heat exchanger (PHE) and bench scale fouling rig, using whey protein concentrate (WPC) and WPC-/m (with added minerals) as fluid models. Fouling and cleaning monitoring methods were also investigated as new ways to operate and control the processes. Experiments displayed that fouling increased with increasing protein concentration up to a limit of approx. β-Lg 0.3 wt. %. Increasing the flow rate from 100 to 150 l/h decreased the Δ(ΔP) fouling rate for β-Lg concentrations of 0.1, 0.3 and 0.5wt.% by 34, 70 and 72.7%, respectively, due to the increasing of shear stresses at the heat transfer surface. Adding minerals to WPC has lowered the temperature at which β-Lg begins to denature. The differences in fouling behaviour of WPC and WPCm had an effect on cleaning behaviour. Increasing the mineral content in WPC deposits leads to cleaning behaviour which differs completely from that of proteinaceous deposit as no pressure peak is observed.
2
Fryer, P. J. "Modelling heat exchanger fouling". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377221.
Testo completo
3
Helalizadeh, Abbas. "Mixed salt crystallisation fouling". Thesis, University of Surrey, 2002. http://epubs.surrey.ac.uk/844179/.
Testo completoAbstract (sommario):
The main purpose of this investigation was to study the mechanisms of mixed salt crystallisation fouling on heat transfer surfaces during convective heat transfer and sub-cooled flow boiling conditions. To-date no investigations on the effects of operating parameters on the deposition of mixtures of calcium sulphate and calcium carbonate, which are the most common constituents of scales formed on heat transfer surfaces, have been reported. As part of this research project, a substantial number of experiments were performed to determine the mechanisms controlling deposition. Fluid velocity, heat flux, surface and bulk temperatures, concentration of the solution, ionic strength, pressure and heat transfer surface material were varied systematically. After clarification of the effect of these parameters on the deposition process, the results of these experiments were used to develop a mechanistic model for prediction of fouling resistances, caused by crystallisation of mixed salts, under convective heat transfer and subcooled flow boiling conditions. It was assumed that the deposition process of calcium sulphate and calcium carbonate takes place in two successive events. These events are the combined effects related to transport phenomena and chemical kinetics. The effect of the extra deposition created on the heat transfer surface due to sub-cooled flow boiling was considered by inclusion of an enhancement factor. The newly developed model takes into account the effects of all important parameters on scaling phenomena and also considers the simultaneous precipitation and competition of various minerals in the scale formation process. Model predictions were compared with the measured experimental data when calcium sulphate and calcium carbonate form and deposit on the heat transfer surface simultaneously. While deviations ranging from 6% to 25% between model predictions and measured experimental data can be considered good in the context of such a complex process, fouling morphology is clearly a factor to be considered in more detail. This is particularly problematic in the context of more complex fouling solutions encountered in industry. Furthermore, the crystalline samples were analysed using Scanning Electron Microscopy, X- Ray Diffraction and Ion Chromatography techniques. Fractal analysis performed on Scanning Electron Microscopy photographs of the deposits was used to quantify deposit characteristics by introducing a new quantity called the fractal dimension.
4
Lewis, William J. T. "Advanced studies of membrane fouling : investigation of cake fouling using fluid dynamic gauging". Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.646145.
Testo completoAbstract (sommario):
Membrane filtrations are widely used in process industries but are almost always limited by fouling, a highly studied and significant problem. This is defined as unwanted material deposited on a membrane surface or within its pores, which can significantly impair performance and/or reduce operating life. The strategies to mitigate fouling include cleaning in place, modified membranes, and optimisation of operating conditions. In order to correctly select or target improvements to any such measures a detailed mechanistic understanding of the fouling process is important, which requires more than just performance data from unit operations. One key mechanism is that of cake fouling, which describes the build-up of particle layers on the surface of the membrane. Its growth and physical properties are difficult to assess. In this project the technique of fluid dynamic gauging (FDG) has been explored as a means to study cake fouling. This simple, yet robust method allows for estimation of thickness and strength of cake fouling at high concentrations and opacity, without any prerequisite knowledge of feed properties. Studies described herein focused on microfiltrations through cellulosic membranes. FDG was used to track cake growth during filtrations of polydisperse yeast suspensions (which contained large agglomerates), demonstrating its capability to work with non-ideal, food-like substances. Later studies used more predictable suspensions of hollow glass spheres, which were used to assess various filtration models. The most effective was found to be an interpretation of the critical flux laws, which were used to successfully identify pore fouling during filtrations of Kraft lignin, an observation supported by FDG measurements. Another novel achievement of this project was the development of an automated apparatus for performing FDG in cross-flow membrane filtration. This allowed for much faster acquisition of results, and demonstrated the potential for its development into an autonomous system capable of making thickness measurements on the fly during filtrations. The most reliable protocol for determining cake growth rates was by repeated filtrations in which destructive thickness testing was performed at selected time points. This was because continuous or even repeated thickness measurements during a single filtration were found to cause too much disturbance to the fouling layer. Computational fluid dynamics was used to simulate shear stress profiles on the fouling layer, while also providing a more accurate means to calibrate the automated apparatus. Erosion caused by FDG readings, when viewed under a microscope, was found to conform to the shear stress profiles predicted by simulations.
5
Shi, Xinlong. "Membrane fouling of activated sludge". Click to view the E-thesis via HKUTO, 2004. http://sunzi.lib.hku.hk/hkuto/record/B30731884.
Testo completo
6
Sandberg, Jan. "Fouling in biomass fired boilers". Licentiate thesis, Västerås : Department of Public Technology, Mälardalen University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-219.
Testo completo
7
Sandberg, Jan. "Fouling in biomass fired boilers". Doctoral thesis, Mälardalens högskola, Akademin för hållbar samhälls- och teknikutveckling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-13204.
Testo completoAbstract (sommario):
This thesis describes a detailed investigation into fouling in biomass fired boilers according to fuel mixture, combustion conditions, transportation of particles by the flue gas and the probability of particles impinging and sticking onto heat transfer tubes. The effects of fouling on overall boiler performance and the efficacy of soot blowing are also investigated. Both theoretical simulations and practical experiments on a 157 MW circulating fluidized bed boiler are presented. The deposit thickness on and around a heat exchanger tube is shown to be mainly dependent on the ash particle size, as particles larger than 10 µm (Stokes number larger than 0.1) mainly impinge on the windward side of tubes. The study also shows that fuel containing small amounts of chlorine and zinc – common elements in recycled wood – may cause both higher deposit growth rates and rapid increases in corrosion rates. These elements (chlorine and zinc), together with alkali metals from the biomass have the potential to form sticky compounds that increase the deposit growth rate. Reducing deposits by soot blowing is very effective at removing loose deposits but the hard sintered part of the deposits is almost unaffected. The use of recycled wood has a larger impact on the deposit growth rate than the soot blowing interval. Numerical simulations show that deposits on the superheater tubes redistribute the heat transfer rate from the superheaters to reheater 1 and partially redistribute turbine power from the high pressure turbine to the intermediate pressure turbine
8
Bradley, Stuart Edward. "Fouling resistant heat exchanger design". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239799.
Testo completo
9
Shi, Xinlong, e 史昕龍. "Membrane fouling of activated sludge". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B30731884.
Testo completo
10
Howell, John Michael. "Whey permeate fouling of evaporators". Thesis, University of Canterbury. Chemical and Process Engineering, 1998. http://hdl.handle.net/10092/10686.
Testo completoAbstract (sommario):
Whey permeate fouling was studied to gain a better understanding of the processes involved and find methods of alleviation. An apparatus was built which allowed study of fouling under industrial conditions. It was found that pretreatment by heating at 80°C for two minutes and then centrifuging at 630 g reduced fouling in the apparatus by 94%. This was attributed to precipitation of calcium phosphate in the solution bulk during preheating, which reduced the level of supersaturation. Heat treatment with the same conditions but without centrifuging reduced fouling by only 39%. Precipitate which forms in the bulk of solution fouls in later heat treatment processes and separation of the precipitated mineral is needed to minimise fouling.
Storage time affected fouling. In the short term (about 2 weeks), fouling slightly increased with storage time. When held for longer times (about 1 month) whey permeate did not appreciably foul.
The use of additives was also found to be an effective alleviation method, reducing fouling by 66% with 0.1% addition (by dry weight) of tetrasodium pyrophosphate. This addition would increase the price of a ton of lactose by $16.32 /ton.
Nanoftltration, ion dialysis and electrodialysis were also examined, but rejected as being uneconomic.
By observing the effect of preheating and storage time it was proposed that calcium phosphate exists in whey in two forms. The majority of the minerals are associated with non-protein nitrogen (NPN) species, which tends to provide stability and prevent precipitation. In the other form the calcium phosphate is in solution as free ions. When the NPN species release minerals due to cleavage by enzymes or denaturation by heat, the concentration of ionic species increases past the solubility product and precipitation occurs.
11
Tow, Emily Winona. "Organic fouling of desalination membranes". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111695.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 211-224).
Energy-ecient desalination and water reuse are necessary to ensure universal access to clean water. Reverse osmosis (RO) is the most ecient desalination process for almost any water source, but it is susceptible to membrane fouling, which can reduce product water quality and raise energy consumption. Fouling can be reduced through (energy-intensive) pretreatment, delayed by membrane coatings, and partially reversed by cleaning. However, poor understanding of fouling physics hinders our ability to predict fouling or design for fouling resistance. Better models of fouling are needed to improve the RO process and provide sustainable sources of desalinated or recycled water to water-scarce communities. Through experiments and modeling, this thesis compares several desalination systems, quantifies the effect of pressure on fouling, and elucidates mechanisms of foulant removal. An experimental apparatus was created to simulate operating conditions in full-scale RO, forward osmosis (FO), and membrane distillation (MD) desalination systems and compare the fouling behavior of these processes under identical hydro-dynamic conditions. In the FO configuration, both uid streams could be pressurized to experimentally isolate the effects of pressure from other operating conditions that affect fouling. A window in the membrane module allowed in situ visualization of membrane fouling and cleaning at pressures as high as 69 bar. Experiments were complemented by the development of physics-based models that predict the eect of hydraulic pressure on foulant layer properties and ux decline and also enable the calculation of foulant layer thickness from measured flux. The findings provide new insight into the relative fouling propensity of membrane desalination systems, the factors influencing ux decline, and the mechanisms of foulant removal. Experiments and modeling show that, although flux decline is slower in FO than in RO, the FO membrane accumulates a thicker foulant layer. Furthermore, FO fouling trials at elevated pressure reveal that fouling behavior is not adversely affected by high hydraulic pressure. Despite this, low operating temperature and unfavorable surface chemistry cause RO to be more susceptible to organic fouling than MD and more susceptible to inorganic fouling than FO. However, neither FO nor MD is immune to fouling: FO flux declined as much as RO ux in the presence of alginate fouling, and MD exhibited rapid ux decline as a result of inorganic fouling. Finally, in situ visualization revealed that osmotic backwashing causes the foulant layer to swell, buckle, and detach in large pieces from both FO and RO membranes, regardless of operating pressure. These findings guide desalination process selection, membrane design, and cleaning protocol development to reduce the energy consumption associated with membrane fouling in desalination.
by Emily Winona Tow.
Ph. D.
12
Alkmim, Aline Ribeiro. "Membrane Bioreactor for treating petroleum refinery effluent: treatment performance, membrane fouling mechanism and fouling control". Universidade Federal de Minas Gerais, 2015. http://hdl.handle.net/1843/BUBD-9Y2HVT.
Testo completoAbstract (sommario):
The work developed discusses the potential use of MBR to treat refinery effluent and operational strategies that may mitigate fouling. At first, MBR performance was evaluated in terms of pollutants removal and fouling investigation in conditions of shock load. The results demonstrated that MBR was able to reduce effectively the pollutants, meeting guideline standards of disposal and reuse for non-potable ends. FTIR results showed that organic matter was removed by biological oxidation and/or retained by adsorption in the biological sludge or retention in the UF membrane. Furthermore, SMP was produced during treatment. In terms of membrane permeability, the results showed that the soluble fraction of mixed liquor contributed significantly to membrane fouling due to the presence of SMP fraction. Secondly, the sludge filterability was studied as an important parameter to evaluate sludge properties and the potentiality of membrane fouling in MBR. Three filterability assessment methods described in the literature were compared regarding their capability to sense sludge quality variation and reproducibility treating petroleum refinery effluents. This study showed that, among the methods evaluated, Time To Filter was the most effective to assess the filterability both in terms of its capability to detect sludge quality variation and reproducibility. The results have also shown that filterability is directly related to membrane fouling potential, and can be used as a tool to monitor and control fouling process in MBR. Significant filterability correlations among colloidal TOC, EPS and floc size were found. The third study assessed the long-term use of cationic polyelectrolyte to improve the sludge filterability, as well as membrane fouling control in bioreactor membrane while treating refinery effluents. Corrective and preventive cationic polyelectrolyte dosages have been added to the MBR in order to evaluate the membrane fouling mitigation in both strategies. The results have confirmed that the use of this product increased sludge filterability, and reduced membrane fouling. During monitoring time stress events occurred due to increase in oil and grease and phenol concentrations in the MBR feed. The preventive use of cationic polyelectrolyte allowed a more effective and stable sludge filterability with lower consumption without decreasing MBR pollutant removal overall performance.O trabalho desenvolvido aborda o uso do BRM tratando efluente de petróleo e estratégias operacionais que possam minimizar a incrustação. Primeiramente, avaliou-se o desempenho do BRM em termos de remoção de poluentes e investigou-se o comportamento da incrustação em ocorrências de cargas de choque. Os resultados demonstraram que o BRM foi capaz de reduzir efetivamente os poluentes, alcançando padrões de descarte e reuso. Os resultados de IV mostraram que a matéria orgânica é removida por oxidação biológica e/ou retenção por adsorção no lodo biológico ou retenção pela membrana. Além disso, verificou-se que o SMP é produzido durante o tratamento. Em relação à permeabilidade da membrana, verificou-se que a fração solúvel do lodo biológico contribui significativamente para a incrustação da membrana devido a presença de SMP. No segundo estudo a filtrabilidade do lodo foi estudada como um importante parâmetro para a avaliação das propriedades do lodo e o potencial de incrustação da membrana em BRM. Foram comparados três métodos de determinação da filtrabilidade relatados na literatura em termos de capacidade de detecção de variações da qualidade do lodo e da reprodutibilidade, avaliando a aplicação deste parâmetro como ferramenta para o monitoramento e controle de incrustação de BRM. O estudo mostrou que o método Time To Filter foi o mais eficiente para medição da filtrabilidade, tanto em termos de capacidade de detecção de variação da qualidade do lodo, como em reprodutibilidade. Verificou-se também que a filtrabilidade está diretamente relacionada ao potencial de incrustação na membrana. Encontraram-se correlações significativas da filtrabilidade com os parâmetros COT coloidal, EPS e tamanho de floco. No terceiro estudo, avaliou-se a utilização de um polieletrólito catiônico a fim de melhorar a filtrabilidade do lodo e consequentemente controlar a incrustação da membrana. Dosagens corretiva e preventiva do polieletrólito foram realizadas nos BRM a fim de avaliar o melhor controle da incrustação nas duas estratégias. Os resultados confirmaram que o uso do produto aumenta a filtrabilidade do lodo e reduz a incrustação da membrana. Durante o período de monitoramento ocorreram choques de carga com altas concentrações de óleos e graxas e fenol na alimentacão. O uso preventivo do polieletrólito catiônico permitiu uma filtrabilidade mais efetiva e estável sem prejudicar o desempenho do BRM quanto à remoção de poluentes.
13
Wheeldon, Paul Robert. "Modelling of fouling in crude oil heat exchangers : an experimental investigation of fouling in laminar flow". Thesis, Teesside University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415773.
Testo completo
14
Walker, Patrick Gareth Chemical Engineering & Industrial Chemistry UNSW. "CFD modeling of heat exchange fouling". Awarded by:University of New South Wales. Chemical Engineering & Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/22385.
Testo completoAbstract (sommario):
Heat exchanger fouling is the deposition of material onto the heat transfer surface causing a reduction in thermal efficiency. A study using Computational Fluid Dynamics (CFD) was conducted to increase understanding of key aspects of fouling in desalination processes. Fouling is a complex phenomenon and therefore this numerical model was developed in stages. Each stage required a critical assessment of each fouling process in order to design physical models to describe the process???s intricate kinetic and thermodynamic behaviour. The completed physical models were incorporated into the simulations through employing extra transport equations, and coding additional subroutines depicting the behaviour of the aqueous phase involved in the fouling phenomena prominent in crystalline streams. The research objectives of creating a CFD model to predict fouling behaviour and assess the influence of key operating parameters were achieved. The completed model of the key crystallisation fouling processes monitors the temporal variation of the fouling resistance. The fouling rates predicted from these results revealed that the numerical model satisfactorily reproduced the phenomenon observed experimentally. Inspection of the CFD results at a local level indicated that the interface temperature was the most influential operating parameter. The research also examined the likelihood that the crystallisation and particulate fouling mechanisms coexist. It was found that the distribution of velocity increased the likelihood of the particulate phase forming within the boundary layer, thus emphasizing the importance of differentiating between behaviour within the bulk and the boundary layer. These numerical results also implied that the probability of this composite fouling was greater in turbulent flow. Finally, supersaturation was confirmed as the key parameter when precipitation occurred within the bulk/boundary layer. This investigation demonstrated the advantages of using CFD to assess heat exchanger fouling. It produced additional physical models which when incorporated into the CFD code adequately modeled key aspects of the crystallisation and particulate fouling mechanisms. These innovative modelling ideas should encourage extensive use of CFD in future fouling investigations. It is recommended that further work include detailed experimental data to assist in defining the key kinetic and thermodynamic parameters to extend the scope of the required physical models.
15
Asomaning, Samuel. "Heat exchanger fouling by petroleum asphaltenes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25011.pdf.
Testo completo
16
Nylund, Göran M. "Chemical mediation of fouling in seaweeds /". Göteborg : Göteborg University, Department of Marine Ecology, 2005. http://www.loc.gov/catdir/toc/fy0701/2006388585.html.
Testo completo
17
Douch, Nicholas. "Air side fouling of heat exchangers". Thesis, University of Brighton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397850.
Testo completo
18
Li, Ning. "Monitoring and control of boiler fouling". Thesis, Queen's University Belfast, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241379.
Testo completo
19
Cohen, Ruben David. "Colloidal fouling of reverse osmosis membranes". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15308.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 128-133.
by Ruben David Cohen.
Ph.D.
20
Lodge, B. N. "Membrane fouling during domestic water recycling". Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/11067.
Testo completoAbstract (sommario):
The performance of a combined biological aerated filter (BAF) and an ultrafiltration
(UF) system for the treatment of real and synthetic greywater, settled sewage,
rainwater and borehole water has been assessed at both full-scale (at the Millennium
Dome Water Recycling plant) and bench-scale.
Irreversible membrane fouling was explained at bench-scale in terms of a simple but
novel model whereby a proportion of the membrane area is progressively blocked, in
proportion to the square root of the transmembrane pressure. This model provides a
link between irreversible fouling and reversible cake filtration theory, as the predicted
reduction in effective filtration area leads to increased solids loading on the unblocked
area. In addition, the bulk properties (specific cake resistance and compressibility) of
the filter cakes formed from biologically-treated real grey water and sewage were
found to be indistinguishable.
A statistical analysis of the results of longer term irreversible fouling trials at bench-
scale led to numerical relationships between fouling rate and process conditions.
These relationships facilitated the development of a process optimisation model, with
the dual-aim of maximising output and minimising chemical consumption.
At full-scale, a statistical technique was developed for calculating the relative fouling
propensity of three water sources (real grey water, rainwater and borehole water) that
were combined in the feed to a UP membrane. The technique was based on the
relative volumes of the three sources and the mean operating trans membrane pressure.
In addition, the impact of mechanical reliability on the financial viability of the full-
scale plant was investigated. A Net Present Value analysis revealed that the break-
even price (BEP) of the recycled water was reduced from £ 1.611m3 to £ 1.40/m
3
through increasing availability from 73.8% to 91.2%, and this can be achieved by
investing in a targeted critical spares facility.
21
Smith, Diane Elizabeth. "Adhesion of Mycobacteria: Capture, Fouling, Aggregation". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542537888485749.
Testo completo
22
Lodge, Benjamin Nicholas. "Membrane fouling during domestic water recycling". Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/11067.
Testo completoAbstract (sommario):
The performance of a combined biological aerated filter (BAF) and an ultrafiltration (UF) system for the treatment of real and synthetic greywater, settled sewage, rainwater and borehole water has been assessed at both full-scale (at the Millennium Dome Water Recycling plant) and bench-scale. Irreversible membrane fouling was explained at bench-scale in terms of a simple but novel model whereby a proportion of the membrane area is progressively blocked, in proportion to the square root of the transmembrane pressure. This model provides a link between irreversible fouling and reversible cake filtration theory, as the predicted reduction in effective filtration area leads to increased solids loading on the unblocked area. In addition, the bulk properties (specific cake resistance and compressibility) of the filter cakes formed from biologically-treated real grey water and sewage were found to be indistinguishable. A statistical analysis of the results of longer term irreversible fouling trials at bench- scale led to numerical relationships between fouling rate and process conditions. These relationships facilitated the development of a process optimisation model, with the dual-aim of maximising output and minimising chemical consumption. At full-scale, a statistical technique was developed for calculating the relative fouling propensity of three water sources (real grey water, rainwater and borehole water) that were combined in the feed to a UP membrane. The technique was based on the relative volumes of the three sources and the mean operating trans membrane pressure. In addition, the impact of mechanical reliability on the financial viability of the full- scale plant was investigated. A Net Present Value analysis revealed that the break- even price (BEP) of the recycled water was reduced from £ 1.611m3 to £ 1.40/m 3 through increasing availability from 73.8% to 91.2%, and this can be achieved by investing in a targeted critical spares facility.
23
Hu, Zhaokang DeSimone Joseph M. "Novel perfluoropolyethers as fouling-release coatings". Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2561.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Oct. 5, 2009). "... in partial fulfillment of the requirements for the degree of Doctorate of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
24
Choo, Wen Choo. "Biomimetic approach to anti-fouling surfaces". Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/1694/.
Testo completoAbstract (sommario):
Scale formation is recognized as one of the major problems affecting production in the oil and gas sector. There are many approaches to remove and prevent scaling with chemical inhibition, chemical scale removers and mechanical methods being the most prevalent ones. Recently the focus has shifted onto more environmentally friendly inhibitors that are less toxic to the environment, thus the development of green inhibitors. Another way forward is to turn to surface engineering - this is a very popular approach in the control of biofouling but only a few attempts have been made to use it for the purpose of scale inhibition. It is fair to say that there is a potential for more widespread study and exploitation of such systems. Biomimetics in surface engineering is receiving more attention as nature provides surfaces with a whole range of functionality. In the present work, microand nano-structured polymers surfaces with the self-cleaning Lotus and antireflective Moth-eye effects have been assessed as potential surfaces able to reduce mineral scale deposition. Calcium carbonate (CaCO3) was deposited onto them and their performance compared with reference stainless steel surfaces. In addition, the anti-scaling performance of three commercially available coatings – DLC, Tech 100 and Tech 23 was also investigated. The surfaces were tested in a rotating cylinder electrode (RCE) under different fluid hydrodynamic conditions i.e. both laminar to turbulent flow. Last but not least, micro-adhesion tests under water were conducted in an attempt to relate deposition tests to the adhesion properties of a single CaCO3 crystal against a surface as a measure of anti-scaling performance.
25
Tacey, Elisabeth Irene. "Laboratory testing of self polising anti fouling copolymers by capacitance measurement and atomic emission spectrometry". Thesis, King's College London (University of London), 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361415.
Testo completo
26
Piltonen, P. (Petteri). "Prevention of fouling on paper machine surfaces". Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202877.
Testo completoAbstract (sommario):
Abstract Fouling in papermaking causes major economic drawbacks due to downtime of process and paper quality defects. The surface fouling is a complex phenomenon in a paper making process, which is affected by several interconnected factors such as process environment changes from wet to dry with increasing temperature along with the variety of sticky materials present in paper raw materials. These impurities, such as waxes, coating binders, hot melts and pressure-sensitive adhesives have a tendency to attach to the surfaces of machinery during paper production and cause surface fouling. The focus of this thesis was on the mechanisms of sticking and surface fouling on a paper machine surfaces caused by problematic sticky organic materials. The sticking potential of six styrene–butadiene latices varying in carboxylation degree, crosslinking density and viscoelasticity and one polyacrylate pressure sensitive adhesive were studied using a cylindrical probe tack method under dry and aqueous conditions. Sticking potential was measured using low and high energy surfaces as an adherent. Also a new practical method for the on-site evaluation of nonstick properties of cylinder coating materials was developed. This method enables monitoring the condition of the coating during its life cycle and also provides the opportunity to compare the performance of different drying cylinder coating materials. The research performed clearly showed that low viscoelastic modulus of latex increases sticking tendency. The results also showed that presence of water can either increase or decrease adhesion depending on the moisture content ant the physic-chemical properties of sticky materials. A low surface energy coating strongly decreases sticking compared to a high energy surface and have a lower susceptibility to fouling in the dry environment. In aqueous conditions, the use of high-energy surfaces decreases adhesion of latices due to their strong interaction with water. Also, the results indicated that carboxylation decreases sticking potential of latex in both dry and aqueous environmentsTiivistelmä Paperikoneiden likaantuminen aiheuttaa suuria tuotannollisia menetyksiä johtuen tuotantoprosessin katkoksista ja paperin laadun ongelmista. Paperikoneen pintojen likaantuminen on monimutkainen prosessi, johon vaikuttavat monet toisistaan riippuvat tekijät ja siten likaantumisilmiötä on vaikea hallita. Paperin raaka-aineet voivat sisältää epäpuhtauksia, kuten vahoja, kuumasulate- ja tarraliimoja, jotka tarttuvat paperikoneen pintoihin aiheuttaen niiden likaantumista. Lisäksi paperin prosessiympäristö muuttuu märästä kuivaan valmistusprosessin edetessä ja lämpötilan kasvaa samanaikaisesti. Tässä väitöskirjassa on kuvattu paperikoneen pintojen likaantumisen mekanismeja ja erityisesti orgaanisten lika-aineiden tarttumista. Tutkimuksessa selvitettiin probe tack -menetelmää käyttäen kuuden erilaisen styreeni-butadieenilateksin ja polyakrylaattitarraliiman tarttuvuutta matalan ja korkean pintaenergian pinnoilla sekä kuivissa että märissä olosuhteissa. Työhön oli valittu latekseja, joiden karboksylointiaste, ristisilloitustiheys ja viskoelastiset ominaisuuden olivat erilaisia. Lisäksi väitöskirjatyössä kehitettiin paikan päällä suoritettava mittausmenetelmä paperikoneen kuivaussylinterien pinnoitteen puhtaana pysyvyyden määrittämiseksi. Tällä menetelmällä voidaan mitata pinnoitteiden kuntoa niiden elinkaaren aikana ja myös vertailla erilaisia pinnoitteita keskenään. Tutkimuksen tulokset osoittivat, että styreeni-butadieenilateksien matala kimmokerroin lisää niiden tarttumista paperikoneen pinnoille. Veden läsnäolo voi joko lisätä tai vähentää tarttumista riippuen veden määrästä ja lika-aineiden fysiokemiallisista ominaisuuksista. Myös paperikoneen pinnoitteen pintaenergia vaikuttaa tarttuvuuteen. Paperikoneen pinnoitteiden pieni pinta-energia vähentää tarttumista kuivissa olosuhteissa, kun taas korkean pintaenergian pinnoitteet vähentävät lateksien tarttuvuutta vesiolosuhteissa. Lisäksi lateksien karboksylointi vähentää niiden tarttumista sekä kuivissa että märissä olosuhteissa
27
Kyriacou, George. "Preventing biosensor fouling by using laminar flow". Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417005.
Testo completo
28
Marouf, Tawga. "Beräkningsalgoritm för fouling i pelletervärmeväxlare inom plasttillverkning". Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-28627.
Testo completoAbstract (sommario):
Sweden’s energy consumption is divided into three major sectors. One of them is the industry sector. One third of Sweden’s energy consumption is converted in the industries. The chemical industry is one of those industries with great energy needs. This thesis looks into energy efficiency in industry, in particular the plastics manufacturing industry. Efficiency concerning heat exchangers, their fouling resistance and also pumps. This thesis also relates to the industry in the big picture as heat exchangers and pumps are widely used and these has a great energy and environmental efficiency. This thesis presents an algorithm especially developed for this issue. The thesis has been written by dividing the work into measurements and data, implementation and analysis. The result of this thesis is an Excel-sheet that may be used to calculate the fouling resistance in a plate heat exchanger.Sveriges energianvändning är uppdelad i tre stora sektorer. Ett av dem är industrin. En tredjedel av Sveriges energiförbrukning omvandlas inom industrierna. Kemiindustrin är av dem industrier som har stort energibehov. Detta examensarbete tar upp effektivisering inom industrin, närmre sett plasttillverkningsindustrin. Effektiviseringen berör värmeväxlare och dess foulingresistans och även pumpar. Examensarbetet kan spegla industrin i den stora bilden då värmeväxlare och pumpar finns väldigt utspritt och effektiviseras dessa har en stor energi och miljöeffektivisering gjorts. För att energieffektivisera inom detta examensarbete har en beräkningsalgoritm tagits fram. Arbetet har delats upp i mätvärden, beräkningar genomförande och analys. Resultatet blev en Excel-ark som kan användas för att beräkna foulingresistansen i en plattvärmeväxlare.
29
Schreier, Paul Jakob Robert. "Monitoring and modelling of heat exchanger fouling". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319355.
Testo completo
30
Gotham, Simon Martyn. "Mechanisms of protein fouling of heat exchangers". Thesis, University of Cambridge, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357741.
Testo completo
31
Downey, Imelda Louise. "Fouling of crude oil refinery preheat exchangers". Thesis, University of Bath, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760645.
Testo completo
32
Lister, Vincent Yves. "Particulate fouling in an industrial cooling system". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708736.
Testo completo
33
Yeap, Boon Lin. "Designing heat exchanger networks to mitigate fouling". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615934.
Testo completo
34
Huang, Jen-Yi. "Fundamental features of food fat freezing fouling". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607795.
Testo completo
35
Jones, Gregory Mark. "Quantifying petroleum fouling of refining heat exchangers". Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690904.
Testo completo
36
Odolczyk, Katarzyna. "Coatings for the prevention of marine fouling". Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/11583.
Testo completoAbstract (sommario):
Microorganisms attachment to the surfaces located in the marine water has become a significant problem. Historically, the antifouling properties of the coatings were achieved by using biocides, which had a negative consequence to the marine environment. Currently, alternative environmental friendly methods are required. This thesis aimed to investigate and produce the antifouling coatings that can be used as potential candidates in the marine industry. In this study, a range of novel polymer nanocomposite coatings was fabricated via the method of solvent and tested based on the strategy of microbial adhesion. The composition of the coatings mainly contains polidimethylsiloxane (PDMS) and different nanomaterials. The coatings applied on glass substrate were characterised using X-ray spectroscopy (XRD), scanning electron microscopy (SEM), contact angle measurements, inductively coupled plasma mass spectroscopy (ICP-MS) and atomic force microscopy (AFM). In biofouling assays, attachment of bacteria B. Subtilis and three marine microalgae (Skeletonema sp., Amphora sp., D. Salina) was investigated in laboratory scale. The obtained results suggested that small amount of nanoparticles in the polymer matrix can improve the antifouling settlement behaviour of the coatings. All microalgae attached more on PDMS/SiO2 and control surfaces (glass and PDMS) compared to the coatings containing multiwall carbon nanotubes (MWCNT) and sodium bismuth titanate (NBT). The influence of contact time, surface roughness and surface wettability was also studied. The microbial attachment varied significantly with respect to contact time and surface properties. There was no obvious evidence showing that the wetting properties and the roughness of the coatings have an effect on growth ... [cont.].
37
Le, Clech Pierre. "Process configurations and fouling in membrane bioreactors". Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/11336.
Testo completoAbstract (sommario):
MBR process consists of a suspended growth biological reactor combined with a membrane unit. The widespread of this system for waste water treatment is contained by membrane fouling, which is strongly influenced by three factors: biomass characteristics, operating conditions and membrane characteristics. Fouling control techniques mainly include low-flux operation (sub-critical flux operation) and/or high-shear slug flow aeration in submerged. configuration. Based on the concept of the critical flux (Jo), the flux-step method has been developed to more fully characterise transmembrane pressure (TMP) behaviour during constant-fluxoperation. A zero rate of TMP increase was never attained during the trial, such that no critical flux, in its strictest definition, could be defined in this study for a submerged MBRs challenged with real and simulant sewage. Under similar operating conditions, Jc was obtained around 18 and 10 L.m-2.h-1 for a submerged MBR fed by real and synthetic sewage respectively. Three TMP-based parameters have been defined, all indicating the same flux value at which fouling starts to be more significant (the weak form of Jo). Results from factorial experimental designs revealed the relative effect of MLSS levels, aeration rate and membrane pore size on J, The MLSS effect on Jc was generally around double that of the aeration effect. The calculation of mean sub-critical values for the different TMP-based parameters suggest lower short-term fouling resistance for large pore sized membranes. A direct comparison between the two MBR configurations revealed a greater J, for the submerged compared to the SS MBR (22 and 11 L.m-2.h-1 respectively) under similar hydraulic conditions. The fluid hydrodynamics has been studied for both configurations, leading to an accurate calculation of shear at the membrane surface in SS MBR and to the determination of the minimum gas velocity required for Taylor bubble formation in submerged MBR (around 0.1 m.s-1). Finally, the effect of operating conditions such as process configuration, feed nature, and aeration type on biomass characteristics has been assessed and link to membrane fouling. Key words: Fouling, MBR, critical flux, process configuration, biomass characterisation.
38
Heinemann, Petra Regina. "The problem of fouling in crossflow microfiltration". Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377962.
Testo completo
39
Cohen, Nathan M. "DC Dielectrophoretic Assisted Anti-Fouling Filtration System". DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/694.
Testo completoAbstract (sommario):
Filtration processes, whether on the microfluidic, clinical treatment systems, or industrial scale (e.g., point-of-care diagnostics, dialysis, and biopharmaceutical manufacturing, respectively), are often inseparable from membrane clogging (fouling). As a consequence, most, if not all, filtration systems require frequent maintenance to maintain functionality and efficiency. The thesis of this project hypothesizes that Dielectrophoresis can be combined with standard filtration to reduce filter fouling, extending membrane life, and enabling continuous operation. This project investigates a method to reduce fouling, add specificity and efficiency, and decrease the cost and challenge of filtration based biofluid separations.
To substantiate this thesis, we designed, fabricated, and tested a filtration system to filter micron diameter particles in suspension using Millipore™ membranes together with fabricated electrodes in a cross-flow filtration system. This prototype device elicits a repulsive dielectrophoretic (DEP) force via the application of a direct current (5-20 volts) sourced from a computer controlled voltage sequencer, designed to levitate and remove larger particles (> 6 µm) before particulate-membrane interaction. Analysis of the results shows a sufficient decrease in particles adhered to the filtration membrane, as compared to control, suggesting DC DEP may be a valid effector in this device. We are convinced that further research will augment the results validating the proof-of-concept thesis presented herein.
40
Borea, Laura. "Advanced MBR processes for wastewater treatment and energy production". Doctoral thesis, Universita degli studi di Salerno, 2016. http://hdl.handle.net/10556/2491.
Testo completoAbstract (sommario):
2014 - 2015More stringent standards on water quality along with the shortage of vater resources have led to the development of advanced wastewater treatment processes, in order to ensure the respect of discharge limits and the reuse of trated water... [edited by author]
XIV n.s.
41
Matune, Nicholas J. "Fouling of Air Cooled Condensers On the Air Side". Youngstown State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1338509830.
Testo completo
42
Zator, Maria Malgorzata. "Membrane fouling characterization by confocal scanning laser microscopy". Doctoral thesis, Universitat Rovira i Virgili, 2009. http://hdl.handle.net/10803/8580.
Testo completoAbstract (sommario):
En sectores tan diversos como la industria alimentaria, la biotecnología y el tratamiento de aguas residuales, la filtración tangencial con membranas se viene utilizando de forma creciente en la separación, purificación y clarificación de distintas corrientes de proceso que contienen gran variedad de compuestos orgánicos. La limitación principal para el empleo industrial de las técnicas de separación por membranas es el ensuciamiento de éstas. El ensuciamiento se atribuye, de forma general, a la reducción en el diámetro de los poros, a su bloqueo y/o a la formación de un depósito en la superficie de la membrana. El avance en el desarrollo de técnicas para la caracterización, el control y la prevención del ensuciamiento de las membranas ha estado limitado por la falta de técnicas adecuadas y no invasivas para la medición del ensuciamiento. El objetivo principal del presente proyecto es desarrollar estrategias apropiadas para aplicar microscopía láser confocal de barrido (CSLM) al estudio del ensuciamiento de membranas de filtración, centrándose en el ensuciamiento causado por macromoléculas biológicas. En la tesis se han llevado a cabo experimentos de microfiltración (MF) de soluciones modelo puras y de mezclas de proteínas, polisacáridos y polifenoles. Las imágenes captadas mediante CSLM de las membranas al final de diferentes experimentos de filtración, han servido para obtener información cualitativa, sobre localización de las distintas moléculas, y cuantitativa, sobre la presencia individual de cada compuesto en el interior y la superficie de la membrana. Se han realizado también intentos de aplicación de visualización en línea mediante CSLM del proceso de microfiltración.In fields such as the food and dairy industries, biotechnology, and the treatment of industrial effluents, pressure-driven membrane processes such as microfiltration are increasingly being used for the separation, purification and clarification of protein-containing solutions. A major limitation to the widespread use of membrane filtration, however, is fouling. Fouling is usually attributed to pore constriction, pore blocking or the deposition of cells and cell debris on the membrane surface and can lead to a reduction in the filtrate flux of more than an order of magnitude. Progress in developing a means for characterizing, controlling and preventing membrane fouling has been impeded by lack of suitable non-invasive fouling-measurement techniques. The main aim of this study is to develop suitable strategies for applying Confocal Scanning Laser Microscopy (CSLM) to characterise membrane fouling caused by biological macromolecules. Microfiltration experiments of single, binary and ternary model solutions of proteins, polysaccharides and polyphenols were carried out and CSLM images of the membranes at the end of the different filtration runs were obtained, in order to obtain quantitative and qualitative information about fouling patterns. Some trials of on-line monitoring of cross-flow microfiltration processes were also carried out.
43
Giannantonio, David John. "Molecular Characterization of Microbial Communities Fouling Concrete Infrastructures". Thesis, Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24797.
Testo completoAbstract (sommario):
The objective of this study was to identify and characterize naturally-occurring communities of Bacteria and Fungi fouling the surfaces of concrete structures in Georgia, USA, through the use of culture-independent and culture-dependent approaches. Genomic DNA was extracted and ribosomal RNA genes were PCR amplified from 4 biofouled sites located in or around the cities of Atlanta, Gainesville, LaGrange, and Savannah. Bacterial and fungal community composition was determined by phylogenetic analysis. Molecular analysis revealed five bacterial phyla, and representatives of the phylum Cyanobacteria and the classes Betaproteobacteria and Gammaproteobacteria dominated the bacterial clone libraries. Fungal clone libraries showed the dominant phylotypes to be most closely related to Alternaria, Cladosporium, Epicoccum and Udeniomyces. Phylogenetically distinct microbial populations were present at each of the biofouled sites. In addition, cultured isolates were obtained from sites and tested for their ability to foul concrete of varied compositions under laboratory-controlled conditions. Biofouling tests revealed that fungal isolates obtained from the field were able to colonize concrete surfaces when supplied with moisture (95-100% relative humidity) and a nutrient source, and that fouling was affected by concrete water/cement ratio, surface roughness, and the presence of photocatalytically-activated cement added to inhibit microbial growth.
44
Ye, Yun School of Chemical Engineering & Industrial Chemistry UNSW. "Macromolecular fouling during membrane filtration of complex fluids". Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/33245.
Testo completoAbstract (sommario):
Macromolecular components, including protein and polysaccharides, are viewed as one type of major foulants in the complex feed membrane filtration systems such as membrane bioreactor (MBR). In this thesis, the mechanisms of macromolecular fouling including protein and polysaccharide in the complex feed solution are explored by using Bovine serum albumin (BSA) and alginate as model solution. During the filtration of BSA and washed yeast with 0.22 ????m PVDF membrane, it was found that the critical flux of mixture solution was controlled by washed yeast concentration while the existence of BSA significantly changed the cake reversibility of much larger particles. The fouling mechanisms of alginate, as a model polysaccharide solution, were investigated both in dead end and crossflow membrane filtration. In the dead end experiments, it was found that the cake model appears to fit the entire range of the ultrafiltration data while the consecutive standard pore blocking model and cake model are more applicable to microfiltration membranes. The alginate was featured with high specific cake resistance and low compressibility despite some variations between different membranes. The specific cake resistance ( c ) is similar to c of BSA and actual extracellular polymer substance (EPS) in MBR systems reported in the literature, and higher than that of many colloidal particles. In a system contained alginate-particles mixture, it was found that the existence of alginate dramatically increased the cake specific resistance and decreased the cake compressibility. The fouling mechanism of alginate was also studied using long term cross flow filtration under subcritical flux. A two-stage TMP profile similar to that typically observed in MBR was obtained, confirming the important role of EPS during membrane fouling in MBR. In addition to adsorption, trace deposition of alginate also contributed to the initial slow TMP increase during the subcritical filtration. TMP increase during the long-term filtration was found not only due to the increase of the amount of deposition, but also the increase of specific cake resistance. A combined standard pore blocking and cake filtration model, using a critical pore size for the transition time determination, was developed and fit the experimental results well.
45
Gironès, i. Nogué Míriam. "Inorganic and polymeric microsieves strategies to reduce fouling /". Enschede : University of Twente [Host], 2005. http://doc.utwente.nl/57485.
Testo completo
46
Srinivasan, Murugan. "Heat exchanger fouling of some Canadian crude oils". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5469.
Testo completoAbstract (sommario):
Fouling refers to deposition of any kind of extraneous material that appears on the surface
of process equipment, such as heat exchangers and reactors. This is a major economic
penalty to oil refineries and heavy residuum upgrading units, thus creating incentives for
a better understanding of fouling mechanisms which underlie methods to mitigate or
control fouling.
This research was focussed on a comparative study of the fouling tendencies of three sour
crude oils supplied by Shell Canada Limited: Light Sour Blend (LSB), Midale (MDL),
and Cold Lake (CLK). The experiments were carried out using a re-circulation fouling
loop equipped with an HTRI-type annular electrical probe. Fluids were re-circulated for a
48 hour period from a feed tank, through the annular fouling probe, and back to the tank.
The unit was operated at a constant heat flux with time, so that fouling could be tracked
by the increase in surface temperature of the probe. Velocity was held constant at
0.75 m/s in most experiments. The unit was pressurized to 860-1240 kPa, depending on
the oil used. Bulk temperatures were varied over the range 200-280°C, and surface
temperatures covered the range 330-380°C. The decrease in overall heat transfer
coefficient varied from 3% to 60%, with most results being in the range 10-32%,
depending on conditions. Fouling resistances up to 0.3 m²K/kW were recorded.
The effects of various parameters, namely surface temperature, bulk temperature, film
temperatures, and annular velocities, on fouling rates were studied for Light Sour blend
in detail.
When correlating temperature effects on fouling rates, some authors use the surface
temperature, while others use the average film temperature, Tf = 0.5 (Ts + T b). In this
study both were examined. A slightly modified film temperature, which gave more
weight to the surface temperature, was found to be the best.
Deposits carefully recovered from the HTRJ probe, after each experiment, were analyzed
using energy dispersive x-ray, giving point analyses on the deposit surface, and by micro
elemental analysis for bulk content of C, H, S and N. Thermogravimetry was used to
determine bulk ash content.
47
Wright, Stephen James. "Heat exchanger fouling in aircraft air-conditioner systems". Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.634789.
Testo completoAbstract (sommario):
The air conditioning heat exchangers of the Airbus A320 are plate wavy fin type. Operational aircraft such as the A320 suffer from failure in commercial service owing to operational fouling and the aim of the research was to investigate the causes of large commercial aircraft air conditioning system failures, attributed to overheating. The aim of the thesis is to research the problems relating to the failure of the Environmental Control System (ECS), and to publish data and findings. The ECS plate fin heat exchangers (PFHE) of live aircraft were examined during hanger maintenance, and later the fouling was analysed and the sources were identified. A series of experiments were designed to replicate an aircraft ECS PFHE operation, similar to that fitted to the A320 using two types of wavy fins (fine and coarse). The novelty of the research was to design a series of experiments that reproduce the aircraft PFHE operations, which included the fouling of the wavy fins. Compressed air was used to replicate the outside 'ram' air cooling flow, · and hot bleed engine air flow was replicated by two electrical heating mats. A new method was used to produce the experimental fouling material which replicated the real world situation. The effects of fouling on fins were observed in terms of heat transfer, pressure drop and fouling analysis. Pressure drop experimental results appeared to be generally consistent yet lower than literature correlations of Hesselgreaves (2001) and Kays and London (1984). The additional fouling supply introduced to the compressed air flow was less than 2% of the total mass flow. Analysis of fouling materials deposited on the fins using scanning mobility particle sizing (SMPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques indicated that fouling samples from live aircraft were very similar to those used in the experiments. The experimental film heat transfer coefficients for the empty channel and the two types of fins were calculated using the analytical solution, initially clean and later fouled. It was expected that the higher number of fins would result in a higher heat transfer performance, yet the experimental results and some predictions indicated this was not the case. The predictions of the film heat transfer coefficients based on the correlations demonstrated that some of the results vary significantly when compared to the experimental coefficients. It was noted that at times, the temperature distribution of the apparatus walls were not symmetrical, resulting in transverse heat conduction.
48
Coward, Rebecca L. "Preventing marine biofouling : the fouling-release-coating approach". Thesis, University of Portsmouth, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419043.
Testo completoAbstract (sommario):
The unwanted build up of fouling organisms on immersed structures has been a problem that has been addressed over the years in many different ways, from tar and pitch on the hulls of vessels to various toxin based ablative coatings and most recently, foul-release coatings that present a non stick surface to which organisms can not adhere strongly. These foul-release coatings have been relatively successful and further investigation into the formulation of siloxane based coatings is a environmentally acceptable and commercially viable concept. The significance of the hydrophilicity of a range of cured siloxane polymers upon the attachment of marine fouling species is presented. The polymers were synthesised from polymethylhydrosiloxane (PDHS) with the grafting of hydrophilic ethoxy based, linear chains of various lengths. Following cross linking, films of these materials were characterised by Nuclear magnetic resonance (NMR), Infrared (lR) spectroscopy, X-ray photoelectron spectroscopy (XPS), contact angle goniometry, topography, thermal analysis, sorption of water, force of adhesion and nano-indentation. The films were tested by bacterial growth and attachment studies, the growth and attachment of various algal propagules and also by static raft trials. Results suggest that there is a maximum hydrophilic content possible when investigating these coatings, due to the intake of water molecules, which causes swelling and subsequent degradation of the stability of the coating. The optimum hydrophilic content for achieving minimum adhesion of fouling organisms was unclear, however, trends in experimental data were identified. The bacterial attachment and growth studies conducted upon Fucus propagules indicated an increase in growth upon the PMHS polymers with the addition of3-{2-[2-(2-methoxy-ethoxy)-ethoxy]ethoxy}- propene groups, while the Sargassum propagules illustrated a reduction in growth during the same conditions. Ulva and Enteromorpha propagules showed no visible trends in growth upon the coatings tested. The surface energy and adhesion results illustrate that the PDMS with 3-{2-[2- (2-methoxy-ethoxy)-ethoxy]-ethoxy}-propene groups were the most adhesive of the coatings teste4 (14.9 oN in comparison to 3-9 oN) but possessed the lowest surface energy (22.46 mJ m2 ). In exposure trials over a 10 month period, the peroxide cured coatings out performed the other curing systems tested, however the colonisation of the range of polymers was inconclusive.
49
Moitsheki, Lesego Johannes. "Nanofiltration : fouling and chemical cleaning / Lesego Johannes Moitsheki". Thesis, North-West University, 2003. http://hdl.handle.net/10394/391.
Testo completoAbstract (sommario):
The challenge of providing developing rural areas in South Africa with
sufficient potable water is substantial. North West Province, among others, is
water-stressed, semi-arid, and largely rural with a high dependence on
groundwater as a strategic resource. Some parts of the province are having
poor water quality which ends up affecting households, farming and livestock.
The aim of this study is to evaluate the performance of nanofiltration (NF)
membranes in detrimental ion (fluoride, nitrate and sulphate) rejection and to
monitor fouling on membranes with their subsequent chemical cleaning.
Five commercial membranes (D12, D11, CTC1, NF90 and NF70) were
characterized using scanning electron microscopy (SEM), single salt
retentions and clean water permeation studies. The three-layered structure of
the membranes was observed using SEM, viz.: smooth dense layer, loosely
networked sublayer and the support. 012, D11 and CTC1 showed higher
water flux than NF90 and NF70. Membranes showed more retention of
divalent ions than of monovalent ions. All tested membranes showed a
negative surface charge density.
During treatment of sampled rural water, all the membranes tested (D12, D11,
CTC1, NF90 and NF70) gave different ion retention results and were mostly
influenced by water composition. All tested membranes satisfactorily rejected
sulphate. NF70 effectively rejected all the ions of interest (fluoride, nitrate and
sulphate) from rural water, indicating that NF70 behaves more like a reverse
osmosis (RO) than an NF-membrane.
During fouling experiments, it was found that salts crystallize on the
membrane surface, thus decreasing the membrane performance. Cake
formation was observed on the membranes fouled with rural water. During
chemical cleaning, acid was not an effective cleaning agent. Alkali and
surfactant solutions separately proved to be moderate cleaning agents (flux
recovery ranged from 50% to 75%) while their combination (alkali and
surfactant) gave the best results (100% flux recovery)Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2004.
50
Lindsay, Hazel M. "Testing community assembly theories in epifaunal fouling communities". Thesis, Edinburgh Napier University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270651.
Testo completo