Дисертації: "Mass transfer"

1

Springer, Pieter Ariaan Martijn. "Mass transfer effects in distillation." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/88084.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

McAleavey, Gervase. "Mass transfer studies in fermentation." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356899.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Erasmus, Andre Brink. "Mass transfer in structured packing." Thesis, Stellenbosch : University of Stellenbosch, 2004. http://hdl.handle.net/10019.1/16045.

Повний текст джерела

Анотація:

Thesis (PhD)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Structured packing is a popular column internal for both distillation and absorption unit operations. This is due to the excellent mass transfer characteristics and low pressure drop that it offers compared to random packing or trays. The main disadvantage is the lack in reliable models to describe the mass transfer characteristics of this type of packing. The recent development of the non-equilibrium model or rate based modelling approach has also emphasized the need for accurate hydraulic and efficiency models for sheet metal structured packing. The main focus of this study was to develop an accurate model for the mass transfer efficiency of Flexipac 350Y using a number of experimental and modelling techniques. Efficiency is however closely related to hydraulic capacity. Before attempting to measure and model the efficiency of Flexipac 350Y, the ability of existing published models to accurately describe the hydraulic capacity of this packing was tested. Holdup and pressure drop were measured using air/water and air/heavy paraffin as test systems. All experiments were performed on pilot plant scale 200mm ID glass columns. Satisfactory results were obtained with most of the models for determining the loading point and pressure drop for the air/water test system. All of the models tested predicted a conservative dependency of capacity on liquid viscosity for the air/paraffin test system. Efficiency and pressure drop were measured using the chlorobenzene/ethylbenzene test systems under conditions of total reflux in a 200mm ID glass column. Widely differing results were however obtained with the different models for the efficiency of Flexipac 350Y. Experiments were subsequently designed and performed to measure and correlate the vapour phase mass transfer coefficient and the effective surface area of Flexipac 350Y independently. The vapour phase mass transfer coefficient was measured and correlated by subliming naphthalene into air from coatings applied to specially fabricated 350Y gauze structured packing. The use of computational fluid dynamics (CFD) to model the vapour phase mass transfer coefficient is also demonstrated. The effective surface area for vapour phase mass transfer was measured with the chemical technique. The specific absorption rate of CO2 into monoethanolamine (MEA) using n-propanol as solvent was determined in a wetted-wall column and used to determine the effective surface area of Flexipac 350Y on pilot plant scale (200mm ID glass column). The efficiency of Flexipac 350Y could be modelled within an accuracy of 9% when using the correlations developed in this study and ignoringliquid phase resistance to mass transfer for the chlorobenzene/ethylbenzene test system under conditions of total reflux. The capacity and efficiency of the new generation high capacity packing Flexipac 350Y HC was also measured and compared with that of the normal capacity packing Flexipac 350Y. An increase in capacity of 20% was observed for the HC packing for the air/water system and 4% for the air/heavy paraffin system compared with the normal packing. For the binary total reflux distillation the increase in capacity varied between 8% and 15% depending on the column pressure. The gain in capacity was at the expense of a loss in efficiency of around 3% in the preloading region.
AFRIKAANSE OPSOMMING: Gestruktureerde pakking is 'n populêre pakkingsmateriaal en word algemeen gebruik in distillasie en absorpsie kolomme. Dit is hoofsaaklik as gevolg van die goeie massa-oordragseienskappe en lae drukval wat dit bied in vergelyking met 'random' pakking en plate. The hoof nadeel is egter die tekort aan akkurate modelle om die massa-oordrags eienskappe te bepaal. Om modelle te kan gebruik waar die massaoordragstempo direk gebruik word om gepakte hoogte te bepaal, word akkurate kapasiteits- en effektiwiteitsmodelle vir gestruktureerde plaatmetaalpakking benodig. Die hoof doelwit van hierdie studie was om 'n akkurate model te ontwikkel vir die massa-oordragseffektiwiteit van die plaat metaal pakking Flexipac 350Y deur gebruik te maak van verskillende eksperimentele- en modelleringstegnieke. Effektiwiteit is egter direk gekoppel aan hidroliese kapasiteit. Bestaande modelle in die literatuur is eers getoets om te bepaal of hulle die hidroliese kapasitiet van Flexipac 350Y akkuraat kan voorspel. Vir die doel is vloeistofterughou en drukval gemeet deur gebruik te maak van die sisteme lug/water en lug/swaar parafien. Alle eksperimente is in loodsaanlegskaal 200mm ID glaskolomme uitgevoer. Meeste van die modelle was relatief akkuraat in hulle berekening van die ladingspunt en die drukval vir die lug/water toets sisteem, maar was konsertief in voorspellings van die groothede vir die lug/swaar parafien sisteem. Effektiwiteit en drukval was gemeet deur gebruik te maak van die binêre toetssisteem chlorobenseen/etielbenseen onder totale terugvloei kondisies in 'n 200mm ID glaskolom. Daar is 'n groot verskil in die effektiwiteitsvoorspelling deur die verskillende modelle. Vervolgens is eksperimente ontwerp en uitgevoer om die dampfase massaoordragskoeffisiënt en die effektiewe oppervlakarea vir Flexipac 350Y onafhanklik te meet en te korreleer. Die dampfase massaoordragskoeffisient is gemeet en gekorreleer deur naftaleen te sublimeer vanaf spesiaal vervaardigde 350Y gestruktureerde pakking van metaalgaas. Die gebruik van numeriese vloeimeganika (CFD) om die dampfase massaoordragskoeffisient te bereken word gedemonstreer. Die effektiewe oppervlakarea vir dampfase massaoordrag is bepaal deur van 'n chemiese metode gebruik te maak. Die spesifieke absorpsietempo van CO2 in monoetanolamien (MEA) met n-propanol as oplosmiddel is gemeet in a benatte wand kolom en gebruik om die effektiewe oppervlakarea van Flexipac 350Y te bepaal op loodsaanlegskaal (200mm ID). Die effektiwiteit van Flexipac 350Y kon met 'n akkuraatheid van binne 9%gemodelleer word deur vloeistoffaseweerstand te ignoreer en van die korrelasies gebruik te maak wat in hierdie studie ontwikkel is. Die effektiwiteit en kapasiteit van die nuwe generasie hoë kapasiteit pakking Flexipac 350Y HC is ook gemeet en vergelyk met die normale kapasiteit pakking Flexipac 350Y. 'n Verhoging in kapsiteit van 20% is gemeet vir die HC pakking in vergelyking met die normale kapasiteit pakking vir die lug/water sisteem en 'n 4% verhoging in kapasiteit vir die lug/swaar parafien sisteem. Die verhoging in kapasiteit het gevarieër tussen 8% en 14% in die binêre totale terugvloei distillasie toetse en was afhanklik van die kolom druk. Die verhoging in kapasiteit was ten koste van 'n verlaging in effektiwiteit van ongeveer 3% onderkant die ladingspunt.

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Zhao, Xiaomin. "Formaldehyde mass-transfer properties study." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51597.

Повний текст джерела

Анотація:

Formaldehyde, an important feedstock in industrial processes and manufacture, is widely present in numerous consumer products. Emitted by many types of consumer products and indoor materials, indoor air can contain high concentrations of formaldehyde. Exposure to formaldehyde is hazardous to human health. Thus knowledge of formaldehyde mass-transfer properties is critical to efforts to reduce formaldehyde emissions and establish related standards and regulations. The primary objectives of this project include: 1) documenting and validating procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics; 2) evaluating and comparing formaldehyde mass-transfer properties in different materials using micro-balance sorption/desorption tests; 3) investigating observed formaldehyde mass-transfer irreversibility and the recently developed formaldehyde polymerization theory. The procedures and methods for analyzing and measuring formaldehyde mass-transfer characteristics were developed in an effort to minimize experimental variability and were strictly followed during the research. The formaldehyde mass-transfer properties of five polymer materials (polycarbonate, polystyrene, poly(methyl methacrylate), polyethylene and polypropylene) were measured through sorption/desorption testing. Results indicated that formaldehyde solubility was highest in polyethylene while the rate of diffusion was the highest in polypropylene. Results also showed that the diffusion process in the selected polymer materials was irreversible in all cases. Furthermore, additional testing showed no detectable polyformaldehyde formation on polymer surfaces after exposure to formaldehyde. The causes of observed mass-transfer irreversibility need further study.
Master of Science

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Xu, Feishi. "Bubble hydrodynamics and mass transfer in complex media." Thesis, Toulouse, INSA, 2019. http://www.theses.fr/2019ISAT0003.

Повний текст джерела

Анотація:

La connaissance du comportement hydrodynamique et du transfert de matière de la bulle est importante car elle fournira des indications pour la sélection des conditions de fonctionnement et la conception du réacteur dans de tels processus. Cette thèse a réalisé une étude expérimentale pour les bulles d’air isolées en ascension dans diverses solutions de polymères (Breox, Polyacrylamide (PAAm) and Xanthan gum) qui peuvent simuler les propriétés des eaux usées. Les travaux sont divisés en trois parties: Tout d’abord, en dressant l’état de l'art sur les techniques de visualisation pour le transfert de matière, trois techniques ont été testées pour les bulles d’air (diamètre équivalent ≈ 1 mm) en ascension dans l'eau, notamment la fluorescence induite par plan laser (PLIF, fluorophore: résorufine fluorescente), la PLIF avec inhibition (fluorophore: complexe de ruthénium) et techniques colorimétriques (colorant: résorufine rose), respectivement. Par la suite, sur la base des images capturées par une caméra haute vitesse, le comportement hydrodynamique des bulles d'air (diamètres équivalents: 0,7 à 7 mm) s'élevant dans les solutions de polymères (PAAm et Xanthan) a été étudiée, notamment la vitesse, la trajectoire et la forme de la bulle. Enfin, appliquant la technique PLIF-I, les phénomènes de transfert de matière et de diffusion dans le sillage de bulles d'air (diamètre équivalent 1 ≈ mm) dans différentes solutions aqueuses de polymères (PAAm et Breox) ont été étudiés
The knowledge on the hydrodynamic property and mass transfer of bubbles is important since it will give guidelines for selecting the operation condition and for reactor design in such processes. For this purpose, this PhD manuscript has implemented an experimental investigation of single air bubbles rising in various polymer solutions (Breox, Polyacrylamide (PAAm) and Xanthan gum) which can simulate the property of the sewage. The works can divided into three parts: Firstly, with a review of the current visualization techniques for mass transfer, three techniques have been tested for air bubble (equivalent diameter ≈ 1 mm) rising in water including traditional Planar Laser Induced Fluorescent (PLIF, dye: fluorescent resorufin), Fluorescent quenching technique (PLIF with Inhibition, dye: ruthenium complex) and colorimetric techniques (dye: pink resorufin), respectively. Secondly, based on images captured by a high speed camera, the hydrodynamics of the bubble single air bubbles (equivalent diameters: 0.7-7 mm) rising in the polymer solutions (PAAm and Xanthan) have been investigated including the bubble velocity, trajectory and bubble shape. Finally, based on PLIF-I technique, the mass transfer and diffusion phenomena in the wake of single air bubbles (equivalent diameter ≈ 1 mm) rising in various aqueous polymer solutions (PAAm and Breox) are investigated

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Raison, Christian E. "Mass transfer in aerated vibrated beds." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03032009-040719/.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Vasan, S. S. "Analysis of mass transfer in ultrafiltration." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424738.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Hanif, Mohammed. "Mass transfer studies in solvent extraction." Thesis, Teesside University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328022.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

9

DUARTE, LUIZ GUSTAVO DA CRUZ. "MASS TRANSFER TO SWIRL IMPINGING JETS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1994. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24868@1.

Повний текст джерела

Анотація:

O presente trabalho é um estudo experimental das características de troca de calor e massa de um jato de ar incidindo ortogonalmente sobre uma placa. o estudo tem por objetivo avaliar a influência nos coeficientes de troca da presença de um componente circunferencial na velocidade do jato. Durante os experimentos foram investigadas a influência do número de Reynolds do jato, da distância jato/placa e da intensidade do escoamento espiralado (número de swirl). Os coeficientes de troca foram determinados utilizando-se a técnica de sublimação de naftaleno em conjunto com a analogia entre os provessos de transferência de calor e massa. Coeficientes de troca de massa locais foram determinados utilizando-se uma mesa de coordenadas computadorizada especialmente construída, que permitiu a obtenção de medidas detalhadas tanto na região de estagnação do jato quanto na região mais externa. Coeficientes globais de troca de massa foram obtidos independentemente dos locais através de pesagem. Os resultados demonstraram uma diminuição nos coeficientes de troca de massa do jato com o aumento da intensidade do escoamento espiralado. Visualizações do escoamento junto à placa foram realizadas, utilizando-se a técnica de óleo com o negro de fumo. Os resultados das visualizações demonstraram a existência de regiões de separação junto à fronteira da zona de estagnação. Para altos valores do número de swirl foram verificadas fortes reversões do escoamento na região de estagnação.
The present work is an experimental study of the mass transfer characteristics of a swirling jet impinging on a flat plate. The main objective of the investigation was to determine the influence of a circumferential velocity component (the swirl component) on the local and average mass transfer coefficients at the plate surface. The dimensionless parameters investigated were the jet Reynolds number, the jet-to-plate distance, and the strength of the swirl flow given by the swirl number. Mass transfer coefficients were obtained utilizing the naphthalene sublimation technique. The local coefficients were determined employing a computerized coodinate table which allowed a detailed study of the effects of the presence of the swirl component. Average coefficients were determined independently through precision weighing, and displayed excellent agreement with the integrated local coefficients. The results demonstrated that the presence of the swirl component decreases the mass transfer coefficients, when compared with the non-swirl case. Flow visualization experiments were conducted utilizing the oil-lamp black technique. The results revealed regions of reverse flow at the stagnation zone for high values of the swirl number.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Kumar, Anil. "Hydrodynamics and mass transfer in Kühni extractor /." [S.l.] : [s.n.], 1985. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7806.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Gurniki, Francois. "turbulent convective mass transfer in electrochemical systems." Doctoral thesis, KTH, Mechanics, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3046.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Dogan, Ismail. "Mass Transfer And Kinetics In Oxygen Delignification." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605562/index.pdf.

Повний текст джерела

Анотація:

In this study, the kinetic analysis of oxygen delignification of Turkish southern hardwood Kraft pulp was carried out. Kraft pulp was obtained from Mopak Dalaman pulp and paper mill. The kinetic rate data were collected in a 1 L high pressure batch reactor. The delignification experiments were carried out under a wide range of industrially significant conditions of temperature (90, 100 and 110 oC), alkali charge (1, 3, 5% on oven dry pulp), and oxygen partial pressure (0.5, 3.5, 6.5 bar). In order to achieve this objective, the study is separated into different stages. In the first stage of the work, the mass transfer effects were examined for different pulp consistencies. It was seen that the inter-fiber mass transfer resistances become negligible at the consistencies below 1%. Therefore, the experiments were performed at 0.5% consistency. In the following stage, the kinetics of oxygen delignification was studied and the governing rate equations were derived. Then, the kinetics of the carbohydrate degradation was analyzed in order to determine the extent of delignification without the reduction in the pulp strength. The delignification and the carbohydrate degredation rate during oxygen delignification increase with increasing in alkali concentration, oxygen partial pressure and temperature. However, the most effective parameters are the alkali concentration and temperature. The dimensionless terms for Kappa number, intrinsic viscosity and reaction time were used in order to generalize the results and to make them independent of the initial Kappa number, the intrinsic viscosity, experimental conditions and pulping conditions prior to oxygen delignification. These dimensionless parameters were fitted to nonlinear equations from which the control of the oxygen delignification towers can be done with a simple equation. The same approach was also used for the reported studies in the literature which allowed the comparison with the results of this study. In the final stage of the study, the simulation of the oxygen delignification unit preceding the CEHDED bleach plant is performed, in order to see the effect of oxygen delignification on the amount of total wastes coming out from the bleach plant. When an oxygen delignification unit is added to the existing CEHDED bleach plant, the amount of pollutants are decreased by 17.96% with output brightness of 92.95. When the overall process parameter optimization of the CEHDED bleach plant is done with oxygen delignification unit, the total amount of dissolved solids coming out from the six washers are decreased by 25.97% with output brightness of 89.5. In order to reduce the pollution load and chemical consumption in Mopak Dalaman pulp and paper mill, management has decided to install an oxygen delignification unit to the plant. Therefore, the rate equations obtained from this study can form a basis for the design and optimization of oxygen reactor in the mill.

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Nadim, Pedram. "Irreversibility of combustion, heat and mass transfer." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13651.

Повний текст джерела

Анотація:

Combustion is by far the most commonly used technology for energy conversion. The analysis of entropy generation and exergy loss is normally used to optimize thermal energy technologies such as gas turbines. The loss of exergy in the combustor is the largest of all component losses in gas turbine systems. The exergy efficiency of gas turbine combustors is typically 20-30%. In recent years the focus on reduction of climate gas and pollutant emissions from combustion has been a driving factor for research on combustion efficiency. The emphasis on fuel economy and pollution reduction from combustion motivates a study of the exergy efficiency of a combustion process. A bulk exergy analysis of the combustor does not take into account the complexity of the combustion process. The spatial dimensions of the flame must be accounted for in order gain detailed information about the entropy generation. This motivates a study of the local entropy production in a flame and quantifying the mechanisms that reduce the exergetic efficiency. The entropy production in combustion is also believed to have an effect on the stability of the flame. As most combustors operate with turbulent flow the emphasis of this report is on turbulent combustion.The source of exergy destruction or irreversibility in combustion is generally attributed to four different mechanisms: chemical reaction, internal heat transfer, mass diffusion of species, and viscous dissipation. The irreversibilities from the first three sources have been computed for a turbulent hydrogen H2 jet diffusion flame using prescribed probability density functions and data from experiments. The contribution of each source of exergy destruction is locally quantifed in the flame. Two different modeling assumptions are made, one based on a fast chemistry assumption and the other based on curve fitted relations from experimental data. The second law efficiency of the flame was found to be 98.7% when assuming fast chemistry, and 76.0% when curve fits from experimental data where used.The contribution from viscous dissipation has in previous studies been found to be negligible, and in order to simplify the modeling of the turbulent flow its contribution to the total entropy production has not been studied in this report.

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Agble, Dugald Komla. "Interfacial mass transfer in binary-liquid systems." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8949.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Keyhani, Alireza. "Heat and mass transfer in layered seedbed." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23997.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Gurniki, François. "Turbulent convective mass transfer in electrochemical systems /." Stockholm, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3046.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Wee, H. K. "Heat and mass transfer in confined spaces." Thesis, University of Canterbury. Chemical and Process Engineering, 1986. http://hdl.handle.net/10092/5879.

Повний текст джерела

Анотація:

A novel experimental technique had been used to investigate the simultaneous transfer of heat and moisture in a simulated building cavity by natural convection. This technique employed two porous plastic plates as the two cavity walls and this arrangement allowed the imposition of a simultaneous moisture gradient on top of a temperature gradient and vice-versa. Both aiding and opposing-flow conditions were investigated for the vertical and horizontal cavity configuration. The aspect-ratio of the experimental cavity used was 7.0 and the fluid investigated was air. The experimental results were correlated in the form of Nusselt and/or Sherwood number versus an appropriately defined Rayleigh number which depended on the type of gradient causing the flow. The Nusselt and Sherwood numbers were found to agree well with the theoretical values of this work obtained from numerical calculation using a finite-difference technique. The temperature, concentration, stream-function and velocity fields from the numerical calculation also augmented the experimental results. As no previous results on the rate of moisture-transfer and s interaction with the rate of heat-transfer in an actual building cavity were available, the results of this work addresses this gap in the literature. Under the conditions investigated, which corresponded to the actual temperature and moisture gradients in a typical building cavity in New Zealand, the simultaneous temperature gradient had increased significantly the rate of moisture transfer while the presence of the simultaneous moisture gradient had not increased significantly the rate of heat transfer.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

O'Hare, Kieran D. "Mass transfer at a two-phase interface." Thesis, Queen's University Belfast, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317126.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Sun, Hong. "Hydrodynamics and mass transfer in Venturi scrubbers." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404054.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Zhang, Guodong. "Heat and mass transfer in porous media." Thesis, University of Leeds, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392321.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Reichrath, Sven. "Convective heat and mass transfer in glasshouses." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391213.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Yapici, Sinan. "Electrochemical mass transfer in annular swirl flow." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303777.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Hayati, Burhan. "Mass transfer characteristics of adiponitrile multiphase electrosynthesis." Thesis, Teesside University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385888.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Karabelchtchikova, Olga. "Fundamentals of Mass Transfer in Gas Carburizing." Digital WPI, 2007. https://digitalcommons.wpi.edu/etd-dissertations/424.

Повний текст джерела

Анотація:

"Gas carburizing is an important heat treatment process used for steel surface hardening of automotive and aerospace components. The quality of the carburized parts is determined by the hardness and the case depth required for a particular application. Despite its worldwide application, the current carburizing process performance faces some challenges in process control and variability. Case depth variability if often encountered in the carburized parts and may present problems with i) manufacturing quality rejections when tight tolerances are imposed or ii) insufficient mechanical properties and increased failure rate in service. The industrial approach to these problems often involves trial and error methods and empirical analysis, both of which are expensive, time consuming and, most importantly, rarely yield optimal solutions. The objective for this work was to develop a fundamental understanding of the mass transfer during gas carburizing process and to develop a strategy for the process control and optimization. The research methodology was based on both experimental work and theoretical developments, and included modeling the thermodynamics of the carburizing atmosphere with various enriching gasses, kinetics of mass transfer at the gas-steel interface and carbon diffusion in steel. The models accurately predict: 1) the atmosphere gas composition during the enriching stage of carburizing, 2) the kinetics of carbon transfer at the gas-steel surfaces, and 3) the carbon diffusion coefficient in steel for various process conditions and steel alloying. The above models and investigations were further combined to accurately predict the surface carbon concentration and the carbon concentration profile in the steel during the heat treatment process. Finally, these models were used to develop a methodology for the process optimization to minimize case depth variation, carburizing cycle time and total cycle cost. Application of this optimization technique provides a tradeoff between minimizing the case depth variation and total cycle cost and results in significant energy reduction by shortening cycle time and thereby enhancing carburizing furnace capacity."

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Kawesha, David Mukuma. "A mass transfer model for structured packing." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52647.

Повний текст джерела

Анотація:

Thesis (MScEng) -- Stellenbosch University , 2002.
ENGLISH ABSTRACT: The distillation process is the most widely used separating process in the chemical process industry. The optimal design of the distillation units can lead to reduced capital costs and improved energy utilisation. This is particularly the case for structured packed distillation column where design methods tend to over-predict the column efficiency. This work seeks to contribute to the development of a reliable mass transfer model for structured packing. A gas phase mass transfer correlation was developed based on the evaporation of pure components into an air stream. The mass transfer rates were measured in a short triangular wetted wall channel with a corrugated surface wall. The influence that the geometric configuration as well as surface structure has on the mass transfer rates was investigated. The channel geometry and surface wall structure resembled that of the structured packing (Flexipac 350Y). The influence of the channel geometry on the gas mass transfer rates was not significant except at low flow conditions. The liquid phase resistance was investigated for binary mixtures in the triangular wetted wall channel. It was found that the overall mass transfer rate decreased with increasing composition of the volatile component. The enhancement of the gas phase mass transfer rate masked the presence of the liquid resistance. ii The gas phase mass transfer correlations were used in the mass transfer model to predict the separation efficiency of a structured packed distillation column. The structured packing used to validate the mass transfer model was high-capacity Flexipac 350Y and normal Flexipac 350Y. The binary distillation experiments were done at total reflux conditions for the pressure range O.33-1atm. The accuracy of the separation efficiencies of the mass transfer model improved with increasing pressure for both materials. The mass transfer model was able to predict the variation of separation efficiencies with column loadings.
AFRIKAANSE OPSOMMING: Distillasie is die skeidingsmetode wat die meeste in die chemiese industrie gebruik word. Die optimale ontwerp van distillasie eenhede kan lei tot verlagings in kapitaalkostes en 'n verbeterde gebruik van energie. Dit is veral waar in die geval van kolomme met gestruktureerde pakking waar huidige ontwerpsmetodes, die kolomeffektiwiteit nie akkuraat beskryf nie. Hierdie studie het ten doelom 'n bydrae te lewer tot die ontwikkeling van 'n betroubare massa-oordragsmodel vir gestruktureerde pakking. 'n Gasfase massa-oordragskorrelasie is ontwikkel gebaseer op metings van die verdampingstempo van suiwer komponente in 'n lugstroom. Die massaoordragstempos is gemeet in 'n kort driehoekige benatle wand kanaal waarin die wand 'n bepaalde oppervlakprofiel het. Die invloed van beide die kanaalgeometrie en die oppervlakprofiel is ondersoek. Die geometrie en oppervlakprofiel is soorgelyk aan die van Flexipac 350Y gestruktureerde pakking. Die invloed van die kanaalgeometrie op die gasfase massaoordragstempos is slegs beduidend by lae vloeitempos. Die vloeistoffase weerstand vir binêre mengsels is ondersoek in die driehoekige kanaal. Dit is gevind dat die algehele massa-oordragstempo verlaag met 'n verhoging in die konsentrasie van die vlugtige komponent. Die verhoging in die gasfase massa-oordragstempo verberg die invloed van die vloeistoffase weerstand. Die gasfase massa-oordragskorrelasies is in 'n massa-oordragsmodel gebruik om die skeidingseffektiwiteit van gestruktureerde pakking in "n kolom te voorspel. Metings op hoë-kapasiteit Flexipac 350Y en normale Flexipac 350Y is gebruik om die modelvoorspellings te evalueer. Die binêre distillasies is by totale terugvloei gedoen in die drukbereik 0.33 - 1.0 atm. Daar is gevind dat die model meer akkuraat is by hoër drukke. Die massa-oordragsmodel is in staat om die variasie in skeidingseffektiwiteit met veranderende kolomlading te voorspel.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Mielnicki, Adam. "CO2 Mass Transfer in a Novel Photobioreactor." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1313775062.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Al-Faize, Mustafa M. "Mass transfer characteristics of large oscillating drops." Thesis, Aston University, 1986. http://publications.aston.ac.uk/10193/.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Pembery, J. G. A. "Mass transfer modelling of heat transfer in partially blocked nuclear fuel bundles." Thesis, University of Exeter, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354029.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Gadani, Clarissa. "Experimental and mass transfer modelling in agarose beads." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

Знайти повний текст джерела

Анотація:

The typical drawbacks of chromatographic separations are associated to the inability of affinity columns to handle high volumetric flow rates at reasonable ligand utilisation efficiencies. Membrane-based separation processes can be used in order to overcome these limitations. The ligand immobilization can be realized by deposition of a high capacitive gel on the convective pore walls of the membrane. To understand the optimal coating layer design, the mass transfer can be investigated in conventional resins. This work includes characterization of agarose-based stationary phases and mass transfer description for immunoglobulin G and a fragment from its digestion. The enzymatic digestion of IgG was performed using papain and fragments of known molecular weight were isolated. The breakthrough curves obtained were simulated in MATLAB using the general rate model and Langmuir kinetics. The parameters needed were derived from empirical correlations and experimentally: particle diameter and size distribution were determined at the microscope; extra-particle porosity of the packed bed was determined through Blake-Kozeny equation; intra-particle porosity was determined through iSEC. The modelling allowed the determination of binding capacity and pore diffusivity of the resins. The latter decreased gradually with increasing agarose concentration as regards the 2%w, 4%w and 6%w beads. Binding capacity is proportional to pore accessibility, which decreased with increasing agarose concentration, and to ligand density. An abrupt reduction of both parameters was detected in the 8%w beads and was related to the low accessibility of the target molecules into the beads diffusive pores, which were the smallest among all the resins tested. These findings can be used to optimize the pore size of chromatographic stationary phases for antibodies purification, with particular focus on novel membranes adsorbers, which allow lower pressure drop, higher flow rates and higher productivity.

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Gruber, Rainer. "Radial mass transfer enhancement in bubble train flow." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=964898292.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Kadic, Enes. "Survey of gas-liquid mass transfer in bioreactors." [Ames, Iowa : Iowa State University], 2010. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1476312.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Kilic, Ilker. "Heat And Mass Transfer Problem And Some Applications." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614140/index.pdf.

Повний текст джерела

Анотація:

Numerical solutions of mathematical modelizations of heat and mass transfer in cubical and cylindrical reactors of solar adsorption refrigeration systems are studied. For the resolution of the equations describing the coupling between heat and mass transfer, Bubnov-Galerkin method is used. An exact solution for time dependent heat transfer in cylindrical multilayered annulus is presented. Separation of variables method has been used to investigate the temperature behavior. An analytical double series relation is proposed as a solution for the temperature distribution, and Fourier coefficients in each layer are obtained by solving some set of equations related to thermal boundary conditions at inside and outside of the cylinder.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Yang, Hsun-min. "Studies of distillation tray hydrodynamics and mass transfer." Thesis, Imperial College London, 2002. http://hdl.handle.net/10044/1/11960.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Lamarche, Philippe. "Air stripping mass transfer correlations for volatile organics." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4763.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Feron, Paul H. M. "Hydrodynamics and mass transfer in obstructed narrow channels." Thesis, Cranfield University, 1991. http://dspace.lib.cranfield.ac.uk/handle/1826/3633.

Повний текст джерела

Анотація:

The objective of this research was to carry out a comprehensive investigation on hydrodynamics and mass transfer of different idealised geometries representing typical conditions which might occur in the narrow cells common in membrane process plant. The method used was to represent these cells by a ten times scale model, adjusting velocity and viscosity to match the Reynolds numbers which might occur in actual membrane equipment, typically between 100 and 1000. The geometries investigated had rods of circular cross-section placed at right angles to the direction of flow: the spacing, positioning and diameter of the rods were varied. Observations of flow patterns indicated that in most geometries flow instability arose at Reynolds numbers-of 200-300, i. e. an order of magnitude below the value at which it would arise in the empty channel. Pressure drop measurements showed that to a reasonable approximation the pressure loss per rod was constant for any given rod diameter. Flow instability did not significantly affect the rate of increase of pressure loss with increasing flow velocity. Mass transfer measurements and shear rate measurements using the diffusion limited current technique were made on these geometries. In contrast with pressure drop, mass transfer generally showed an upturn at higher values of the Reynolds number than the value at which flow instability set in. Local mass transfer and shear rate were correlated by means of a simple theoretical model. Excellent agreement was achieved for steady flow but agreement was only qualitative for unsteady flow. The conclusions which have emerged point the way to development of actual geometries superior, to those currently in use with respect to their pressure loss/mass transfer characteristics. These would improve the performance of membrane equipment, _and. possibly other mass and heat transfer processes in which geometry of this kind is encountered.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Jauhari, Ritika. "Gas-solid mass transfer in a rotary drum." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21176.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Krothapalli, Deep. "Gas-liquid Mass Transfer in Oxygen Delignification Systems." Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/KrothapalliD2004.pdf.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Lindblom, Jenny. "Condensation irrigation : simulations of heat and mass transfer." Licentiate thesis, Luleå : Luleå University of technology, 2006. http://epubl.luth.se/1402-1757/2006/08.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Hussain, Arshad. "Heat and mass transfer in tubular inorganic membranes." [S.l.] : [s.n.], 2006. http://diglib.uni-magdeburg.de/Dissertationen/2006/arshussain.htm.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Hall, Charles A. "Kinetics and mass-transfer effects in batch alkoxylations." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11213.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Lutostansky, Elizabeth McClelland. "The role of convective mass transfer in atherosclerosis." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15933.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Morin, Francois. "Mass transfer limitations in sulfite pulping with anthraquinone." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28495.

Повний текст джерела

Анотація:

The objective of this project was to study systematically the NSSC-AQ pulping process in order to improve the penetration of anthraquinone and sodium sulfite in wood and to simulate the mass transfer and delignification processes.
In a heterogeneous reaction system, such as wood pulping, two main factors control the overall reaction rate: liquor penetration and chemical diffusion. As a first step, some wood characteristics affecting liquor impregnation were evaluated: 1) fiber hydraulic radius, 2) air, steam and water content, 3) wood elasticity and compressibility. Secondly, impregnation and pulping experiments were performed while varying the pre-steaming, compression and soaking time. Finally, experimental profiles were compared to computer simulated results. The two most commonly used species by the pulp industry were chosen for this study: 1) black spruce sapwood and heartwood as well as 2) trembloid poplar sapwood.
Impregnation of sulfite-AHQ liquor in wood blocks was simulated by a three-dimensional "Control Volume Finite Difference Method (CVFDM)". To de-couple the pressure and velocity fields, typical to convection-diffusion problems, a mass balance around individual control volume was performed using Poiseuille's capillary flow equation. The pulping kinetic differential equations were included into the CVFDM model to simulate a three-dimensional delignification pattern in the wood.
In general, the progression of the anthraquinone impregnation was slow and non-uniform in comparison to sulfite which penetrated rapidly and uniformly during pulping. Furthermore, delignification uniformity was related to the initial chemical profiles observed after impregnation. This confirms the importance of chemical pre-treatment for high yield pulping in order to minimize uneven delignification for chips thicker than 3mm. Results showed that, in most cases, computer simulated profiles were similar to experimental anthraquinone and sulfite impregnation patterns.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Zhao, Min. "Mass transfer to viscous liquids in bubble columns." Thesis, University of Cambridge, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315975.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Lund, I. D. "Hydrodynamics and mass transfer problems in wet spinning." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370283.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Porter, Simon William. "Heat and mass transfer during structured cereal baking." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505758.

Повний текст джерела

Анотація:

The majority of modern cereal baking ovens are tunnel ovens with multiple zones, each of which is individually controlled. A baking profile is set by the oven operator, which describes the target temperatures and air velocities in each of the zones along the length of the oven. There may be up to ten zones in modern tunnel ovens; it is thus a complex procedure to generate an optimum profile. A computer numerical model was developed to model the baking process and to make predictions of the biscuit temperature, heat flux and moisture content through the bake.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Galbraith, Graham H. "Heat and mass transfer within porous building materials." Thesis, University of Strathclyde, 1992. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21508.

Повний текст джерела

Анотація:

The thermal and structural performance of building elements can be significantly impaired by the presence of excess moisture. At present, designers have available only simplistic steady-state techniques to predict such effects, for example that presented by Glaser in 1959. These simple models recognise moisture transport in vapour form only and do not allow information on material moisture content to be obtained directly. They are also based on the assumption that the material transport properties are independent of the prevailing environmental conditions, whereas they are in fact complex functions of parameters such as relative humidity. This research has been carried out to develop a set of model equations which account for both liquid and vapour transfer through porous structures, and which enable material moisture content profiles to be produced. The equations generated in this work are transient and enable the effects of moisture and thermal capacity to be considered. An experimental investigation has also been carried out to produce a methodology which can be used to obtain the required material properties. These equations and material properties have been combined with realistic boundary conditions to produce a finite difference model which enables simple wall structures to be analysed in terms of temperature, vapour pressure, relative humidity, moisture content and moisture flow rate. The use of this FORTRAN 77 computer code is illustrated by application to traditional and timber-framed wall constructions. The results illustrate the applicability and flexibility of such an approach and confirm the importance of its further development in the future.

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Xiang, Yuanyuan. "Mass Transfer Phenomena in Rotating Corrugated Photocatalytic Reactors." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30342.

Повний текст джерела

Анотація:

Photocatalysis is a green technology that has been widely used in wastewater treatment. In this work, mass transfer processes in corrugated photocatalytic reactors were characterized both experimentally and through computer simulations. For the experimental work, various drum rotational speeds, reactor liquid volumes and number of corrugations were studied to elucidate their effects on mass transfer phenomena. The mass transfer rate was found to increase with increasing rotational speed. Liquid volumes in the reactor significantly affect the mass transfer rate when 20% of the surface area of the drum was immersed. A higher mass transfer rate was found using the drum with 28 corrugations, which had the lowest mass transfer coefficient when compared to the drums with 13 and 16 corrugations. In the computer simulations, velocity and concentration fields within the corrugated reactors were modelled to explore the characteristics of mass transfer processes. The mass transfer coefficients predicted by the simulations were lower than those measured experimentally due to mass transfer limitations occurring between the corrugation volume and bulk solution in the simulations. Based on mass transfer characteristics, it was determined that the drum with 28 corrugations was the most efficient photocatalytic reactor, and had the lowest mass transfer coefficient among those studied.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Aboulhasanzadeh, Bahman. "Multiscale computations of mass transfer in bubbly flows." Thesis, University of Notre Dame, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3583008.

Повний текст джерела

Анотація:

Mass transfer and reaction in the liquid phase of gas-liquid multiphase flows usually takes place at a considerably slower rate than the transfer of momentum, so mass flux boundary layers are much thinner than momentum boundary layers. In Direct Numerical Simulations (DNS) the resolution requirement for flows with mass transfer are therefore significantly higher than for flow without mass transfer and reaction. In this work we develop a multi-scale approach and demonstrate its implementation in 2D to compute the mass transfer from buoyant bubbles, using a boundary-layer approximation next to the bubble and a relatively coarse grid for the rest of the flow. This approach greatly reduces the overall grid resolution required. Then we implement our method in 3D and perform validation of the approach by comparing to experimental data and semi-empirical correlations from the literature. We study the effect of void fraction and bubble interactions on the mass transfer from many bubbles using a 3D implementation of the code. Specifically, we do simulations of single bubbles in periodic boxes and we compare it to the simulation of several bubbles in a larger domain with the same void fraction. Comparisons shows that even though the average Reynolds number of freely moving bubbles drops after a while the mass transfer from the bubbles for most case studies increases slightly when bubbles start wobbling which increases bubble interactions. We also develop a film model to recover the under-resolved viscous forces between colliding non-coalescing droplet.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Bashir, Skander. "Studies in mass transfer for liquid-liquid systems." Thesis, Teesside University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277632.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Khan, Nasar Ahmed. "Modelling and mass transfer studies in continuous crystallisers." Thesis, Teesside University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410867.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Дисертації з теми "Mass transfer"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями