Dissertations / Theses on the topic 'Contact heat and mass transfer'
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Tseitlin, Musii, and Valentina Raiko. "Ratio between heat and mass transfer when concentrating the solution in a cooling tower." Thesis, Lviv Polytechnic National University, 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/42106.
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The ratio between the intensity of the mass transfer in gas and the heat transfer in liquid during the evaporative solution concentration has been studied. It was determined that the share of liquid resistance in the total resistance to enthalpy transfer increases in the temperature range from 30 to 50°C by almost 2 times, and reaches 40 %. The technique has been developed for the separate determination of the mass transfer coefficients in gas and heat transfer in liquid.Досліджено співвідношення між інтенсивністю масопереносу в газі та передачею тепла в рідині під час концентрації випарного розчину. Встановлено, що частка опору рідини в загальному опорі переносу ентальпії зростає в діапазоні температур від 30 до 50 ° С майже в 2 рази, досягає 40%. Розроблена методика для окремого визначення коефіцієнтів масопереносу в газі і теплопередачі в рідині.
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Bratuta, E. G., R. G. Akmen, T. I. Jaroshenko, and O. V. Krugliakova. "The influence of interaction surface structure and irrigation scheme on heat and mass transfer in direct contact condenser." Thesis, Országos Sugárbiológiai és Sugáregészségügyi Kutató Intézet (OSSKI), 1997. http://repository.kpi.kharkov.ua/handle/KhPI-Press/23120.
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The contact condensation of saturated steam on liquid spray has been studied. The mathematical model of heat and mass transfer processes between dispersed liquid and steam has been usin one-parameter drop distribution function has been worked out. The rational degree of liquid dispersing and optimál irrigation scheme has been defined.
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Maani, Nazanin. "A MODEL FOR THE PREDICTION OF THERMAL RESPONSE OF BONE IN SURGICAL DRILLING." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/theses/1245.
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This Thesis develops a mathematical model for predicting the thermal response in the surgical drilling of bone. The model accounts for the bone, chip and drill bit interactions by providing a detailed account of events within a cylindrical control volume enveloping the drill, the cut bone chip within the drill bit flute and the solid bone. Lumped parameter approach divides the control volume into a number of cells and cells within the sub-volumes representing the drill solid, the bone chip and the bone solid are allowed to interact. The contact mechanics of rough surfaces is used to model chip-flute and chip-bone frictional interaction. In this way not only the quantification of friction due to sliding contact of chip-flute and chip-bone rough surface contact are treated, but also the contact thermal resistances between the rubbing surfaces are included in the model. A mixed combination of constant and adaptive mesh is employed to permit the simulation of the heat transfer as the drill bit penetrates deeper into the bone during a drilling process. Using the model the effect of various parameters on the temperature rise in bone, drill and the chip are investigated. It is found that maximum temperature within the bone occurs at the location adjacent to the corner of the drill-tip and drill body. The results of the model are found to agree favorably with the experimental measurements reported in the existing literature on surgical drilling.
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Frackiewicz-Kaczmarek, Joanna. "Determination of the air gap thickness and the contact area under wearing conditions." Thesis, Mulhouse, 2013. http://www.theses.fr/2013MULH5151/document.
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Le transfert de masse et de chaleur dans les vêtements est un phénomène faisant appel àdifférents mécanismes physiques : les échanges de chaleurs sèches et les transferts de vapeur etde liquide. Ces mécanismes sont fortement influencés par les facteurs liés à la construction, laforme du vêtement par rapport à celle du corps et l’utilisation du vêtement. Ces facteurs peuventêtre optimisés en changeant la taille et la forme des différentes couches d’air emprisonnées entrela peau et les vêtements. La plupart des modèles mathématiques de vêtements font l’hypothèse que l’épaisseur d’air entrela peau et l’étoffe est uniforme, ou alors ils l’ignorent. La non-uniformité et de la non-linéaritédes transferts de chaleur et d’eau ne sont alors pas prises en compte. En effet, le processus detranspiration dépend non seulement de l’aire de contact et de l’épaisseur d’air emprisonnée entrela peau et le vêtement mais également de la région du corps. Nous proposons une méthode permettant de déterminer, avec une plus grande précision que lestechniques existantes, l’épaisseur d’air et l’aire de contact entre le corps et un vêtement à l’aided’une analyse avancée de scans 3D d’un mannequin homme nu et habillé. L’effet du tauxd’humidité sur l’aire de contact et l’épaisseur du film d’air a été étudié en fonction de la zone ducorps et ceci pour différentes tailles, structures de l’étoffe et fibres. Cette méthode contribue àévaluer de façon plus réaliste les échanges de masse et de chaleur au travers de plusieurs couchesde vêtements et ainsi de fournir des données d’entrée précises aux modèles pour la conception devêtements avec prise en compte du confort et de l’ergonomieThe heat and mass transfer within the clothing system is a composition of a number of physicalprocesses, such as: dry heat and vapour and liquid water transfer. Factors associated with theconstruction and use of the garment, such as body posture and movement, and clothing fitinfluence these processes significantly. This is achieved mainly by changing the size and theshape of the different layers of air trapped between the skin and clothing. Most existing mathematical clothing models assume uniform air gap between the body and fabric layers or ignore it. However, this approach disregards the non-uniform and non-linear heat,vapour and liquid water transfer, which depend on presence of contact between surfaces and onthe shape of the air layers trapped within clothing and the body regions which are not equivalentin terms of sweating process. In this study, we propose a method to accurately determine the air gap thickness and the contactarea between clothing and the human body through an advanced analysis of 3D body scans of thenude and dressed body of a male manikin. This method allowed more accurate measurement ofthe air gap thickness and the contact area than other existing methods. Additionally, in two casestudies the effect of garment design and moisture gain in fabric combined with effects of bodypart, garment type and its overall and regional fit, fabric structure and fibre type were determined.Consequently, this method will contribute to a more realistic evaluation of heat and massexchange rates through clothing systems and provide more accurate input for ergonomic andcomfort design of clothing
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Sobac, Benjamin. "Evaporation de gouttes sessiles : des fluides purs aux fluides complexes." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4801/document.
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Cette thèse présente une étude expérimentale sur l'évaporation de gouttes reposant sur un substrat solide. Dans une première partie, nous nous sommes intéressés à la description de l'évaporation d'une goutte liquide en regardant notamment l'influence du substrat. Le problème est approché sous un angle nouveau : en contrôlant avec précision les différentes propriétés du substrat que sont sa rugosité, son énergie de surface et ses propriétés thermiques. Cette méthode a permis de découpler les différentes influences du substrat et d'étudier l'évaporation pour différentes dynamiques de ligne triple et une large gamme d'angles de contact, de conductivités thermiques et de températures de substrat. Les résultats expérimentaux sont comparés au modèle classique d'évaporation. Ce modèle considère l'évaporation comme un processus contrôlé par la diffusion de la vapeur dans l'atmosphère. L'étude révèle les domaines de validité de ce modèle et met en évidence les différents mécanismes additionnels pouvant se développer ainsi que leur contribution. L'utilisation d'une caméra infrarouge dévoile le développement d'un motif hydrodynamique complexe non-axisymétrique. L'origine de cette instabilité, ces dynamiques spatiales et temporelles sont également explorées. Dans une seconde partie, l'étude a été étendue à l'évaporation d'une goutte de suspension biologique : le sang. Le séchage de ce fluide conduit à la formation d'un motif complexe dépendant de la mouillabilité du substrat. Alors qu'une situation mouillante met en évidence un dépôt de type annulaire accompagné de fractures radiales, une situation non-mouillante révèle une forme complexe composée de fractures et de plisThis thesis presents an experimental study on the evaporation of droplets on a solid substrate. In the first part we describe the evaporation of a liquid droplet, taking a particular interest in the influence of the substrate. The problem is approached from a new angle by ensuring that the various properties of the substrate, such as its roughness, surface energy and thermal properties, are controlled precisely. Thanks to this method it is possible to decouple the different influences of the substrate and to study evaporation in relation to various dynamics of triple lines and a wide range of contact angles, thermal conductivities and temperatures of the substrate. Experimental results are compared with the classic evaporation model, which considers evaporation as a process determined by the diffusion of vapor into the atmosphere. The study reveals the range of validity of this model and highlights the different additional mechanisms which may develop as well as their contribution. The use of an infrared camera reveals the development of a complex hydrodynamic non-axisymmetric pattern. The origin of this instability and its spatial and temporal dynamics are also explored. In the second part, the study is extended to the evaporation of a dropl of a biological suspension: human blood. As this fluid dries a complex pattern is formed which is dependent on the wettability of the substrate. Whereas a wetting situation leads to a ring-like deposit with radial cracks, a non-wetting situation reveals a complex shape composed of cracks and folds. The study focuses on the understanding of the physical mechanisms leading to these patterns and of the role of biology
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Viné, Thibaut. "Caractérisation expérimentale et modélisation des transferts de matière et d’énergie lors des opérations culinaires de cuisson par contact." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASB015.
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La cuisson des aliments est une des opérations de transformation les plus courantes aussi bien à l’échelle domestique, en restauration hors-foyer, qu’à l’échelle industrielle. Parmi les nombreux modes de cuisson existants, la cuisson par contact n’a fait l’objet que d’une attention très réduite dans la littérature, plus particulièrement en ce qui concerne les transferts de matière et d’énergie dans l’aliment et entre l’aliment et son environnement. Cette situation s’explique en grande du fait des difficultés métrologiques et théoriques qu’entraîne l’étude des transferts thermiques par contact dans le cas des procédés alimentaires. Cette thèse a pour objectif de contribuer à mieux comprendre et prédire les transferts de matière et d’énergie et d’apporter des nouveaux outils (notamment numériques) permettant d’améliorer le dimensionnement et la conduite de ce type d’opération. Pour atteindre cet objectif, une démarche associant étude expérimentale et modélisation des phénomènes de transfert a été conduite. Un dispositif de cuisson instrumenté a été conçu afin de réaliser une large campagne expérimentale visant à étudier l’impact de plusieurs conditions opératoires de chauffage sur la cuisson de trois produits : la pomme de terre, la crêpe et l’omelette. Les résultats obtenus ont permis de développer et valider plusieurs modèles capables de prédire avec justesse les montées en température et les pertes en eau des produits étudiés au cours de la cuisson. Ces modèles sont suffisamment génériques pour être facilement adaptables d’un produit à un autre et transposables à différents procédés de cuisson par contactCooking is one of the most common food processing operations at both domestic and industrial scale. Among the many cooking methods, contact cooking has received very little attention in the literature, particularly with regard to the transfers of mass and energy within the food and between the food and its environment. This is mostly due to the metrological and theoretical difficulties involved in the study of contact heat transfer in food processes. The aim of this thesis is to contribute to a better understanding and prediction of mass and energy transfers during contact cooking and to provide new tools (especially numerical ones) to better dimension and monitor this operation. To achieve this objective, an approach combining experimental study and modelling of transfer phenomena has been achieved. An instrumented cooking device was designed in order to carry out a large experimental campaign aimed at studying the impact of several heating conditions on the cooking of three products: potato, pancake and omelet. The results enabled the development and validation of several models capable of accurately predicting the temperature rises and water losses of these products during cooking. These models are generic enough to be easily adaptable from one product to another and transposable to different contact cooking processes
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Никольский, Валерий Евгеньевич. "Синергетические реакционно-массообменные процессы в газожидкостных аппаратах и топливных агрегатах химической технологии." Thesis, Украинский государственный химико-технологический университет, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24524.
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Диссертация на соискание ученой степени доктора технических наук по специальности 05.17.08 – процессы и оборудование химической технологии. – Национальный технический университет "Харьковский политехнический институт" Министерства образования и науки Украины, Харьков, 2016 г.
Диссертационная работа посвящена решению актуальной инжиниринговой научно-технической проблемы: разработать современные энергоэффективные экологически чистые технологии, средства генерирования и потребления тепловой энергии с применением систем рекуперации теплоты на основе синергетического единства аппаратурно-технологического оформления процессов и системного подхода. В работе разработаны научно-методологические основы и практические способы повышения эффективности использования топлива в газожидкостных аппаратах и топливных агрегатах химической технологии за счет интенсификации тепловых процессов в их рабочем пространстве. С позиции совершенствования топливо– и материалосберегающих техники и технологий созданы новые конструкции газожидкостных аппаратов и топливных агрегатов. На их основе синтезированы экологически чистые энергоэффективные технологические системы (ЭТС), приемлемые для химической технологии и других сфер промышленности, коммунального, сельского хозяйства, отвечающие современным энергетическим и экологическим требованиям. Систематизированы методы интенсификации гетерогенных процессов в теплотехнологических аппаратах; предложены новые перспективные РТ и АК методы интенсификации и обоснована целесообразность их практического использования при синтезе новых ЭТС на базе синергетически совмещенных реакционно-разделительных процессов (обеспечение неоднофазности, наложение электрических и магнитных полей на контактирующие фазы, оптимизация параметров пульсаций в гетерогенных системах, одно- и многотипное комбинирование теплогенерирующих аппаратов, обеспечение многократных входных и концевых эффектов, соударения, закручивания, взаимной эжекции контактирующих фаз и их осциллирования, циклический подвод энергии). Разработанные и приведенные в диссертации аппараты, технологические процессы и оборудование широко внедрены на предприятиях Минхимпрома, Минметаллургии, Минавтопрома, Минкоммунхоза Украины и стран СНГ.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Нікольський, Валерій Євгенович. "Синергетичні реакційно-масообмінні процеси в газорідинних апаратах і паливних агрегатах хімічної технології." Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/24517.
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Дисертація на здобуття наукового ступеня доктора технічних наук за спеціальністю 05.17.08 – процеси та обладнання хімічної технології. – Національний технічний університет "Харківський політехнічний інститут" Міністерства освіти і науки України, Харків, 2016 р.
Дисертаційна робота присвячена вирішенню актуальної інжинірингової науково-технічної проблеми: розробити сучасні енергоефективні екологічно чисті технології, засоби генерування та споживання теплової енергії із застосуванням систем рекуперації теплоти на основі синергетичної єдності апаратурно-технологічного оформлення процесів і системного підходу. У роботі розроблено науково-методологічні основи та практичні способи підвищення ефективності використання палива в газорідинних апаратах і паливних агрегатах хімічної технології за рахунок інтенсифікації теплових процесів в їх робочому просторі. З позиції вдосконалення паливо- і матеріалозберігаючих техніки і технологій створено нові конструкції газорідинних апаратів і паливних агрегатів. На їх основі синтезовано екологічно чисті енергоефективні технологічні системи (ЕТС), прийнятні для хімічної технології та інших сфер промисловості, комунального, сільського господарства, які відповідають сучасним енергетичним та екологічним вимогам. Розроблено високоефективну контактно-модульну систему (КМС), обладнану апаратами зануреного горіння (АЗГ) з багатократною інверсією і модуляцією коливань контактуючих фаз для потреб теплопостачання промислових будівель і споруд, житлових і сільськогосподарських комплексів, яка виключає використання котельних і бойлерних установок з утилізацією теплоти продуктів згоряння, тепловою потужністю 200, 400, 600, 1000, 2000 кВт і вище залежно від потреби в генерованій теплоті. Витрати на обігрівання будівель і споруд при використанні пристрою знижуються в 2,5-2,8 рази в порівнянні з традиційними способами обігрівання. КМС пройшла державні тепло-екологічні випробування, які підтвердили її високу енергоефективність, екологічність, надійність в роботі. Отримано технічні умови на серійне її виготовлення і експлуатацію в різних галузях народного господарства. Розроблені і наведені в дисертації апарати, технологічні процеси і устаткування широко впроваджені на підприємствах Мінхімпрому, Мінметалургіі, Мінавтопрому, Мінкомунгоспу України та країн СНД.A thesis for Doctor of Technical degree, specialty 05.17.08 – process and equipments of chemical technology. – National Technical University "Kharkiv Polytechnic Institute" Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis deals with the improvement of actual engineering science-technical problem: the development of the modern energy effective ecological technologies, the means of energy generation and consumption using the heat recuperation systems on the base of synergetic unity of hardware implementation of the processes and system approach. For that the methodological fundamentals and practical methods of increasing of fuel utilization efficiency in the gas-liquid apparatuses and in the fuel combustion units of chemical technology at the expense of heat processes intensification were developed. Looking for improvements in fuel efficiency and materials saving the new constructions of gas-liquid apparatuses and fuel combustion units were created. On this base the ecological and energy efficiency technological systems were synthesized. They confirm to the requirements of modern power engineering and they are acceptable for the chemical technology and the other industries, as well as for communal services and agriculture. The high-effective contact-module system was developed. It was equipped with the immersion combustion apparatuses with multiple phase inversion and oscillation modulating of contacted phases. The system can be used for heat supply of industrial and agricultural buildings, apartment houses without using boilers with heat utilization of combustion products, when heat rating of 200, 400, 600, 1000, 2000 kWt is assumed, depending a need for generated heat. The expenses for complex structures and buildings’ heating using the development are decreased by 2,5 – 2,8 times in comparison with the traditional means. Contact-module system has stood the government heat-ecological test, which confirmed its high efficiency, ecological compatibility, serviceability. Construction standard specifications for serial production in the different branches of economy were obtained. The developed and presented in the thesis apparatuses, technological processes and equipments were applied in chemistry, metallurgy, motor-car industries and in communal services in Ukraine and CIS countries.
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Abada, Fella. "Transport d'humidité en matériaux poreux en présence d'un gradient de température : caractérisation expérimentale." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10135.
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Ce travail de these porte sur des etudes experimentales relatives aux transferts monodimensionnels d'humidite sous differents gradients thermiques dans des materiaux poreux qui sont: le beton autoclave non expanse, la vermiculite, deux roches extraites de carrieres (rouffach et rorschach) servant a la restauration de monuments historiques. Un dispositif experimental est utilise pour le suivi continu des evolutions de teneurs en eau (methode gammametrique) et de temperatures (sondes thermiques) durant des essais de condensation et de sechage. L'objectif principal de ce travail est la determination des coefficients de transfert pour chaque materiau, determination basee sur la theorie classique du transfert de masse et de chaleur de de vries. Les coefficients de transfert sont calcules par un procede de regression entre les variables mesurees: flux de masse, gradient de temperature et gradient de teneur en eau, on donne leurs evolutions avec la teneur en eau et pour differentes temperatures. D'autres experiences sont aussi realisees donnant les conductivites thermiques et les isothermes d'adsorption permettant, ainsi, d'acquerir des informations sur le comportement des materiaux vis a vis du transfert de chaleur et de vapeur d'eau
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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Souccar, Adham. "Heat transfer and mass transfer with heat generation in drops at high peclet number /." Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177603981.
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Dissertation (Ph.D.)--University of Toledo, 2007.Typescript. "Submitted as partial fulfillment of the requirements for The Doctor of Philosophy degree in Engineering." Bibliography: leaves 65-74.
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Souccar, Adham W. "Heat Transfer and Mass Transfer with Heat Generation in Drops at High Peclet Number." University of Toledo / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177603981.
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Prince, Dallan R. "Measurement and Modeling of Fire Behavior in Leaves and Sparse Shrubs." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5545.
Full textAbstract:
Wildland fuels and fire behavior have been the focus of numerous studies and models which provide operational support to firefighters. However, fuel and fire complexity in live shrubs has resulted in unexpected and sometimes aggressive fire behavior. The combustion of live fuels was studied and modeled, and the results were assimilated into a shrub-scale fire behavior model which assumes fire spread by flame-fuel overlap. Fire spread models have usually assumed that radiation heat transfer is responsible for driving fire spread, but that assumption is a topic of continuing debate, and appears to contradict some experimental observations. A convection-based shrub-scale fire spread model has been developed, building on a heritage of experiments and modeling previously performed at Brigham Young University. This project has (1) characterized fundamental aspects of fire behavior, (2) integrated the resulting submodels of fire behavior into an existing shrub model framework, and (3) produced shrub-scale fire spread experiments and (4) made model comparisons. This research models fire spread as a convection-driven phenomenon and demonstrates strategies for overcoming some of the challenges associated with this novel approach.
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Douglas, Zachary W. "Acoustically Enhanced Boiling Heat Transfer." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16325.
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An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.
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Kayikci, Ramazan. "Metal-mould contact and heat transfer during casting solidification." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681341.
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Krugliakova, O. V. "Mathematical study of heat transfer in direct contact condenser." Thesis, NTU "KhPI", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/38262.
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Kilic, Ilker. "Heat And Mass Transfer Problem And Some Applications." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614140/index.pdf.
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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.
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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.
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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.
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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.
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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.
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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.
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Sabir, Hisham. "Heat and mass transfer processes in absorption systems." Thesis, King's College London (University of London), 1993. https://kclpure.kcl.ac.uk/portal/en/theses/heat-and-mass-transfer-processes-in-absorption-systems(ab68d065-c159-4292-ad39-b7a820ac0054).html.
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Hussain, Arshad. "Heat and mass transfer in tubular inorganic membranes." [S.l.] : [s.n.], 2006. http://diglib.uni-magdeburg.de/Dissertationen/2006/arshussain.htm.
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Shao, Ming. "Modelling simultaneous heat and mass transfer in wood." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42073.
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The fundamental and quantitative study of heat and mass transfer processes in wood plays an important role for understanding many important production processes, such as wood drying and hot-pressing. It will help us improve the existing products and production techniques and develop new manufacturing technology. The most difficult aspect of the study is the complicated interactions of heat and mass transfer mechanisms. Extensive characterization of these physical processes using a strictly experimental approach is extremely difficult because of the excessively large number of variables that must be considered. However, mathematical modeling and numerical techniques serve as a powerful tool to help us understand the complicated physical processes.
The goal of this research is to model the simultaneous heat and mass transfer in wood. The specific objectives of this research are:
1) develop a computer simulation program, implementing an existing one-dimensional mathematical drying model, using a finite difference approach, to numerically evaluate the mathematical model.
2) study sensitivity of the heat and mass transfer model to determine the effects of wood physical properties and environmental conditions on the drying processes.Master of Science
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Staton, JoAnna Christen II. "Heat and Mass Transfer Characteristics of Desiccant Polymers." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/9785.
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Desiccant-enhanced air conditioning equipment has exhibited both the capability to improve humidity control and the potential to save energy costs by lowering the latent energy requirement of the supply air stream. The resulting increasing popularity of desiccant-enhanced air conditioning systems has sparked new interest in the search for a better, more efficient desiccant material. The ultimate goal of this research was to develop a material that, when applied to an existing air-to-air heat exchanger, would achieve the necessary heat and mass transfer in a single process, thus transforming a sensible heat exchanger into a total enthalpy exchanger.
This study focuses on the development and determination of appropriate polymeric desiccant materials for use in different heat and mass transfer applications. Various candidate materials were initially studied. It was decided that polyvinyl alcohol best met the pre-determined selection criteria. After the focus material was chosen, numerical models representing two heat and mass transfer applications were created. One-dimensional numerical models were developed for the performance studies of a rotary wheel total enthalpy exchanger. A two-dimensional numerical model was developed for the performance studies of a fixed plate total enthalpy exchanger as well. Material characterization tests were performed to collect material property information required by the numerical models.
Sensible, latent, and total efficiencies gathered from both the rotary wheel total enthalpy exchanger and the fixed plate total enthalpy exchanger models indicate potential uses for some candidate polyvinyl alcohol materials.Master of Science
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Glockling, James L. D. "Heat and mass transfer in specific aerosol systems." Thesis, London South Bank University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303937.
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Цюра, Надія Ярославівна. "Сумісний процес фільтрування та сушіння дисперсних матеріалів." Diss., Національний університет "Львівська політехніка", 2021. https://ena.lpnu.ua/handle/ntb/56692.
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Дисертаційна робота присвячена теоретичним та експериментальним дослідженням фільтраційного сушіння дисперсних матеріалів, зокрема Fe(II) сульфат гептагідрату, відпрацьованого деревного
борошна й залізоокисного пігменту з метою проектування енергоощадного обладнання. Встановлені основні фізико-механічні характеристики стаціонарного шару досліджуваних матеріалів, а саме: насипна густина, пористість, питома поверхня, еквівалентний діаметр каналів, крізь якіфільтрується тепловий агент, усереднений діаметр частинок. На основі узагальнення результатів досліджень гідродинаміки запропоновані рівняння для встановлення гідравлічного опору стаціонарного шару за різних параметрів теплового агенту, які можуть бути використані на етапі проектування нового сушильного обладнання.
Експериментальним шляхом досліджений теплообмін під час фільтраційного сушіння й запропоновані критеріальні залежності у вигляді безрозмірних комплексів для визначення коефіцієнтів тепловіддачі від
теплового агенту до шару Fe(II) сульфат гептагідрату. Встановлений характер впливу висоти стаціонарного шару Fe (II) сульфат гептагідрату, відпрацьованого деревного борошна й залізоокисного пігменту, а також температури теплового агенту й швидкості фільтрування на інтенсивність
фільтраційного сушіння та запропоновані розрахункові залежності для прогнозування процесу висушування вказаних матеріалів в періодах повного та часткового насичення теплового агенту вологою.
Розроблена схема сушильної установки для зневоднення дисперсних матеріалів в стаціонарному шарі шляхом профільтровування теплового агенту крізь пористу структуру, на яку отриманий патент України на винахід. Наведена методика розрахунку та проведені технологічні обчислення, які дали змогу розрахувати основні розміри сушарки та встановити параметри процесу фільтраційного сушіння. The work deals with the filtration method for drying Fe (II) sulfate of heptahydrate, the exhausted wood flour and iron oxide pigment. This method is elected as the most effective according to the critical analysis of literature data. The work is dedicated to the theoretical and experimental researches of filtration drying of dispersed materials, in particular Fe (II) sulfate of heptahydrate, the exhausted wood flour and iron oxide pigment for the purpose of designing of the energy saving equipment. The basic physical and mechanical characteristics of
the stationary layer of the studied materials are determined, such as: bulk density, porosity, specific surface area, averaging of particles size, equivalent diameter of the channels through which the heat agent is filtered. On the basis of obtained experimental data of hydrodynamics research, the equations for establishing the
hydraulic resistance of the stationary layer at variable parameters of the heat agent are proposed. Heat transfer during filtration drying is investigated experimentally and criterion dependences in the form of dimensionless complexes for determination of heat transfer coefficients from heat agent to Fe (II) sulfate heptahydrate layer are proposed. The nature of the influence of the height of the stationary layer of Fe (II) sulfate heptahydrate, exhausted wood flour and iron oxide pigment, as well as the temperature of the heat agent and filtration rate on
the intensity of filtration drying and the proposed dependences for predicting the drying process of these materials. The basic scheme of the drying installation for dehydration of dispersed materials, a technique of its calculation are developed and the basic technological calculations are carried out. The patent of Ukraine for
the invention has protected the plant.
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Mason, Brian L. "An experimental investigation of charge transfer during ice contact interactions /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9769.
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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.
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McClelland, Elizabeth A. "Heat and mass transfer in an axisymmetric sudden expansion." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/16462.
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Tzevelecos, Wassilis. "Contribution to Heat and Mass Transfer for Space Experiments." Doctoral thesis, Universite Libre de Bruxelles, 2018. https://dipot.ulb.ac.be/dspace/bitstream/2013/269864/6/contratWT.pdf.
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This manuscript has been realized in the frame of SELENE experiment research activities. SELENE is the ac-ronym of Self-rewetting fluids for ENErgy management and consists of a space project aiming to investigate heat and mass transfer phenomena in mono-groove configuration with self-rewetting fluids (SRFs). Self-rewetting fluids are mixture showing an anomalous trend of surface tension with temperature, an inversion of the surface tension slope after certain temperature. As consequence, when the minimum in surface ten-sion is crossed, surface tension gradient at the meniscus interface pulls the liquid towards the warmest region, preventing hot spots. This mechanism is completely spontaneous and has an interesting potential when applied to heat transfer applications as heat pipes (HPs). In HPs heat is removed by the liquid at the warmest region (the evaporator) and transported at the coldest zone (the condenser) by phase change; here, heat is removed by the pipe and dissipated outside through a radiator. To operate correctly, liquid is supplied to the evaporator by capillarity and the liquid vapour is allowed to flow back to condenser from a dedicated pipe region where liquid is not allowed. Vapour condensation releases at the condenser the heat to be dissipated. When SRFs are replacing working fluid in HP applications and temperatures are higher than the characteristic minimum in surface tension, capillary force is assisted by inverse Marangoni flow at the vapour-liquid interface.Since heat pipe performances are related to liquid supplied at the evaporator, in order to compare SRFs and not SRFs working fluids, it is needed to split the contribution of Marangoni and capillary force in the liquid flow. Marangoni effect is related to surface tension gradient that, in a mixture as SRF, is dependent on temperature and local composition at the liquid interface. For all these reasons, SELENE is designed to be the link between scientific research on HPs and heat transfer applications using SRFs. SELENE consists of a mono-groove with trapezoidal section that can be considered as a “clump” of an Inner Grooved Heat Pipe (IGHP) and, in order to split capillary and Marangoni contribution, it is integrated dedicated tools providing the required data in terms of concentration and liquid meniscus shape. Experimental data are used to build a simplified thermo-soluto-fluido dynamic model describing the thermo-mechanic mechanisms between the liquid bulk and the vapour flow. In the manuscript here presented it has been carried on a technology development of the required diag-nostics for the SELENE space project. The diagnostics have been designed to work in microgravity condi-tions even if they are tested on ground. As concentration diagnostic, in the text are proposed several tech-niques and more interest is spent on the adaptation of I-VED (In vivo Embolic Detection) technology meas-uring fluid AC impedance to retrieve composition information; the technology is not yet mature to be inte-grated in SELENE but it presents interesting features to be investigated in microgravity conditions. As me-niscus reconstruction technique it is proposed a new and innovative technology developed in the frame of the presented thesis and it consists of a non-intrusive optical technique aiming to retrieve liquid meniscus shape (and so curvature) from a single visualization window mounted at the top of the SELENE breadboard.An analytical approach aiming to retrieve a simplified mathematical model of the transfer mechanisms is also provided in the text. The analytical analysis clearly shows the relations between the experimental measured data and the velocity profiles in the liquid and vapour regions. In addition, since in SELENE exper-iment the heat conduction across the groove itself is not negligible, in the text it is provided a semi-empirical thermal model based on the Multi Lumped Model (MLM) theory and able to retrieve local heat exchanged information along the pipe length. The model is used to compare experiments with different working fluids at different operational regimes.Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished
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Song, Yang. "Solids transportation, heat and mass transfer in rotary dryers." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26346.
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In this thesis, the mechanisms of solids transportation, heat and mass transfer within rotary dryers were first examined.
Some experimental data obtained in pilot-scale and industrial rotary dryers were used to investigate the influences of moisture content of solids and gas temperature on solids transportation, typically on solids mean residence time distribution, and on heat and mass transfer to estimate the volumetric heat and mass transfer coefficients.
One pilot-scale rotary dryer with direct contact between the gas and the solids with co-current flow has been designed, constructed and tested in our laboratory. It mainly consists of four parts: an electric fan, an electric heater, a solids feeding system and a rotary cylinder. Numerous experiments were performed to investigate the dynamic characteristics of solids transportation in this pilot-scale rotary dryer. (Abstract shortened by UMI.)
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Okorafor, Agbai Azubuike. "A study of heat and mass transfer in a double-diffusive system /." Available from the University of Aberdeen Library and Historic Collections Digital Resources. Restricted: no access until May 13, 2009, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=26048.
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Oh, Sung Hyuk. "Experimental and numerical investigation of turbulent flow and heat (mass) transfer in a two-pass trapezoidal channel with turbulence promoters." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3198.
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Malhotra, Karun. "Particle flow and contact heat transfer characeristics of stirred granular beds." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74233.
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Particle flow features and wall-to-bed contact heat transfer characteristics of beds of granular solids stirred by flat blades (paddle-type) in horizontal cylindrical troughs are presented and discussed. Variables examined include: bed-to-blade height ratio (2-10), agitator speed (0-60 rev/min), wall-to-blade clearance (2.3-80 mm), vessel diameter (250 and 500 mm), solids flowability (0.07-0.25), air flow rate (0-0.5 m/s), particle moisture content (0-0.85 kg water/kg dry particles), particle surface stickiness (0-1.3 $ times$ 10$ sp{-3}$ kg glycerine/kg dry particles) and blade configuration (perforated and non-perforated). Glass beads, rice, millet and linseed were used as model particles.Overall mixing maps showing regimes of good and poor solids mixing are presented. Granular solids flowability was found to influence particle flow characteristics substantially within the bulk as well as the wall-to-blade clearance region of the bed. Bulk solids flowability in stirred vessels was characterized by a novel procedure which incorporated the combined effects of particle shape, surface roughness, moisture/stickiness and deformability. The torque required to stir the particulate bed is influenced strongly by the solids flowability and blade configuration.
A physical model for the wall-to-bed contact heat transfer coefficient based on particle renewal rates at the heated surface is proposed. The particle renewal rates and particle-surface contact times are evaluated exclusively from the particle flow information in the clearance region with no empirical parameters. The effects of particle shape and bed porosity at the contacting surface on the surface-to-particle thermal contact resistance were evaluated. Experimental results showing the effects of agitator speed, wall-to-blade clearance, solids flowability and air flow rate on the wall-to-bed average heat transfer rate are presented and discussed. The contact heat transfer model was found to predict the experimentally measured results reasonably well.
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Ayers, George Harold. "Cylindrical thermal contact conductance." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969/88.
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Parra, Saldivar Maria Luisa. "Heat and mass transfer behaviours of building materials and structures." Thesis, Cranfield University, 2005. http://hdl.handle.net/1826/4019.
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Heat storage as a means to respond to the requirements for improved energy
efficiency motivated this study. The objective was to evaluate the impact of thermal
energy storage systems in dwellings under Mexican climatic conditions. In the first part
of this work thermal behaviors of adobe traditional architecture is discussed; in the
second part a latent heat storage system using phase change materials (PCMs) is
proposed and assessed.
The high thermal mass structural elements of adobe traditional architecture have been
charactefted as heat wave modulators. Nevertheless, the moisture content in these
structures also plays a significant role as a means for heat storage and potentially
enhancing thermal lag. The objective of this part of the study was to assess the scope
of existing coupled heat and mass transport models regarding water contained latent
heat storage on porous structures.
The significant contribution of latent heat storage recognized in adobe structures, led to
the study of a solar-thermal storage system using (PCMs).
The objective of this part of the study was twofold: 1) Enhance the existing
computational models on the Stephan problem by considering the effect of regional
variations (weather conditions imposed) on the boundary conditions. 2) Evaluate the
impact of the solar-thermal system proposed when applied in dwellings in view of
regional variations under Mexican weather conditions.
Solar-thermal storage systems independent of the structure offer the possibility to be
applied to existing buildings as well as new constructions. The proposal is a storage
element that constitutes internal blinds in windows. The computational model of the
Stephan problem was solved with the enthalpy method. Simulations were run under
different sets of climatic conditions. For the first time the main factors for promoting
system's optimisation, when gathered in a single comparison study, provided a more
general insight on system's performance. Experimental work was also carried out
regarding the charging of the heat storage unit by heat gains other than direct
radiation, and the storage unit's performance as insulator. A large-scale solar simulator
was constructed.
Statistical analysis of experimental results showed interesting findings including: The
important role that internal heat gains play on the charging of the latent heat storage
unit proposed. A larger effect on the discharging ratio was found with lower air
temperatures than with faster air flow rates. The faster discharging rate tests also
released slightly more energy. PCM volume was found to be the most critical factor on
system performance. The importance of providing the means to discharge the total
quantity of heat stored was pointed out. For the cooling mode, elements to enhance
discharging might be required. For system control, thermal insulation was found to be
an effective measure when the discharging is required to occur over a longer period.
The multiple PCM unit was found to be more efficient during the charging process
(storing more energy) than units containing a single PCM. Nevertheless the single PCM
unit performed better for cooling than the multiple PCM unit. The question was raised as
to what extent PCM thermal conductivity actually influences system's performance.
The thermal storage system proposed in this study reduced the heating system energy
consumption requirements for an experimental room by 28.6%.
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Kadylak, David Erwin. "Effectiveness method for heat and mass transfer in membrane humidifiers." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7092.
Full textAbstract:
A thermodynamic model for use in predicting heat and water transfer across a membrane in a membrane humidifier was created that could take into account fuel cell operating conditions. Experiments were conducted to obtain the necessary information to make the model complete, and also to validate its use over a range of temperatures and flow rates.
The latent effectiveness and latent number of transfer units (ε-NTU) method for mass transfer in membrane humidity exchangers was applied to PEMFC membrane humidifiers to comprise the heat and mass transfer thermodynamic model. Two limitations that cause deviations in the theoretical outlet conditions previously reported were discovered: 1. using a constant enthalpy of vaporization derived from the reference temperature in the Clausius-Clapeyron equation; and, 2. simplifying the relationship between relative humidity and absolute humidity as linear. In the model presented here, these limitations are alleviated by using an effective mass transfer coefficient Ueff. The model was created in Mathcad and the constitutive equations are solved iteratively to find the flux of water through the membrane.
The new procedure was applied to three types of membrane and compared to the curves of εL and NTUL found using Zhang and Niu’s method, which is normally applied to energy recovery ventilators (ERVs). For a 70°C isothermal case, a deviation in latent effectiveness predictions was observed of 29% for Type-I membranes, 23% for linear-type membranes, and 46% for Type-III membranes, as compared to the latent effectiveness values obtained with the ERV method.
Experiments were conducted on a commercially available fuel cell humidifier to determine which parameters could be removed from a full-factorial experimental matrix. It was discovered that pressure had a lower effect on water transport than temperature over the practical operating range of fuel cell systems, so pressure effects were neglected throughout the study. The focus of the study was then on the effect of overall temperature. Furthermore, it was determined that water recovery ratio is the best performance metric because it takes into account the water supplied to the humidifier.
Two different membranes were characterized to incorporate into the thermodynamic model. The first, used as a baseline, was a porous polymer membrane with a hydrophilic additive. The second membrane was a competing novel ionic membrane. Both membranes showed similar behavior, with low water uptake profiles at relative humidities less than 80%, and a steep increase in water uptake after 80% relative humidity. The porous membrane exhibited greater maximum sorption than the ionic membrane.
Experiments were conducted with samples of the porous and ionic membrane in a single cell humidifier at isothermal conditions at temperatures of 25°C, 50°C, and 75°C. The ionic membrane showed greater water transfer over the range of laminar flows investigated. The ionic membrane’s water recovery was almost unaffected by flow rate; whereas the porous membrane displayed a decrease in water recovery as flow rate increased. Finally, the model was correlated with the experimental data by obtaining a corresponding diffusion coefficient for each membrane over the range of temperatures tested.
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Francis, Nicholas Donald. "Heat and mass transfer in a semi-porous textile composite." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17085.
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Roberts, David Nigel. "Heat and mass transfer studies in sodium-argon filled enclosures." Thesis, London South Bank University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245136.
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Li, Yi. "Heat and mass transfer for the diffusion driven desalination process." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013737.
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ARAÚJO, PAULO MURILLO DE SOUZA. "HEAT AND MASS TRANSFER BETWEEN LIQUID FILM AND AIR STREAM." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1986. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20587@1.
Full textAbstract:
O objetivo deste trabalho é analisar as transferências de momentum, calor e massa num canal bidimensional inclinado, onde escoam um filme líquido descendente e uma corrente turbulenta de ar de sentido oposto, ou de mesmo sentido oposto, ou de mesmo sentido. O filme líquido, suposto laminar, consiste numa solução fraca, ou degenerada, de trietileno glicol em água. A placa inferior do canal é mantida aquecida numa temperatura uniforme, de modo a facilitar a remoção de água do líquido para a fase gasosa. A corrente de ar deve ser turbulenta, para garantir taxas convenientes da massa de água transferida. Considera-se, não obstante, a possibilidade do ar também escoar liminarmente. A placa superior do canal, ou cobertura é adiabática e ambas as placas são impermeáveis à transferência de água. A parte hidrodinamica do problema é resolvida separadamente. Atribui-se maior importância à determinação dos perfis de temperatura e concentração de águas nas duas fases.
Pretende-se que a aparelhagem acima descrita opere como um regenerador da substância líquida higroscópica, tendo este sido previamente usado num secador de ar, em aplicação de fim industrial ou agrícola. A tarefa proposta pelo problema é a simulação das condições operativas do trocador de massa. Como resultado desta simulação, tenciona-se predizer os valores dos coeficientes de transferências de calor e massa, variando amplamente as taxas de escoamento, tanto da fase gasosa, quanto da líquida.
Na verdade, diversos pesquisadores têm revelado, nos últimos anos, um grande interesse no estudo de regeneradores do tipo aqui analisado. Toda vez que se tem disponibilidade de energia a temperaturas moderadas e baixo custo, como energia solar ou calor de rejeito industrial, parece indicado regenerar desta forma o desumidificante líquido nas instalações de condicionamento de ar por resfriamento evaporativo.
Estabelecidas as equações diferenciais parciais do problema e as condições de contorno pertinentes, elas são resolvidas através de algoritmos obtidos por diferenças finitas, dentro do enfoque de volumes de controle. O procedimento numérico é interativo, usando-se o computador digital na obtenção da solução. Verifica-se que os resultados se mantêm dentro da analogia entre transferência de calor e massa, conforme era esperado. A partir dos resultados, podem-se estabelecer algumas correlações para os principais parâmetros do problema.
Propõe-se, por fim, uma metodologia para o projeto do equipamento. Para isto, não é necessário fazer uso direto do método numérico, pois existem algumas poucas equações analíticas, simples, que podem ser facilmente manipuladas num microcomputador ou, até mesmo, numa calculadora eletrônica. Estas equações são deduzidas a partir da aplicação da teoria de penetração ao problema. As correlações dos resultados numéricos são, entretanto, essenciais ao bom emprego da teoria penetração.The combined momentum, heat and mass transfer is analysed in a two domensional inclined channnel for a countercurrent, or co-current turbulent air strem flowing past a liquid falling film. The film flow, supposed to be laminar, consists of a weak, or co-current tubulent air stream flowing past a liquid falling film. The film flow, supposed to be laminar, consists of a weak, or degenerate, solution of triethylene glycol and water. The film flow, supposed to be laminar, consists of a weak, or degenerate, solution of triethylene glycol and water. The lower plate of the channel is maintained at a constant, relatively high from the liquid to the gas phase. The stream of air is usually turbulent, thus assuring convenient rates of tranferred mass of water. Nevertheless, the possibility of laminar flow in the gas is not avoided. The second plate of the channel is considered as adiabatic and both plates are impervious to water. The hydrodynamic part of the problem is solved separately, and the determination of temperature and concentration of water profiles in the two phases is of major importance. The apparatus above described is intended to be a regenerator of the hygroscopic liquid, previously used in an air dryer, for industrial or agricultural purposes. The tash suggested by the problem is then to simulate the conditions, under which this mass exchanger will operate. Following the simulation, heat and mass transfer coefficientes can be predicted for a large range of flow rates of both gas an liquid phases. In fact, in recent years several investigators have manifested an increasing interest in developing studies of such equipment. In situations where a source of energy at low temperature is freely available, and this is the case of solar energy or industrial rejects, the employment of liquid dehumidifier regenerators is particularly attractive for evaporative cooling air conditioning systems. The partial differential equations of the problem, accompanied by suitable boundary conditions, are solved by a finite difference scheme, based on the volume of control approach. There are iterative procedures involved and solutions is reached in a mainframe computer. The results seem to be in accordance with the expected analoggy between heat and mass transfer. Some correlations are presented for the principal parameters of the problem. Lastly, a methodology is proposed for the design of the equipment. In spite of the complexity of the problem, it is possible to provide the user with a few simple analytic equations, which can be solved in any micro-computer or even in a pocket calculation. Theses equations arise from the employment of the penetration theorym briefly discussed and compared with numerical results. Indubitably, the use of this theory must be in compliance with the previously obtained numerical correlations.
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Mattingly, Brett T. (Brett Thomas). "Containment analysis incorporating boundary layer heat and mass transfer techniques." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/84749.
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Tien, Hwa-Chong. "Analysis of flow, heat and mass transfer in porous insulations /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487672631599499.
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Khalafallah, Bahjat H. "Coupled heat and mass transfer in concrete exposed to fire." Thesis, Aston University, 2001. http://publications.aston.ac.uk/14160/.
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The first investigation of this study is concerned with the reasonableness of the assumptions related to diffusion of water vapour in concrete and with the development of a diffusivity equation for heated concrete. It has been demonstrated that diffusion of water vapour does occur in concrete at all temperatures and that the type of diffusion is concrete is Knudsen diffusion. Neglecting diffusion leads to underestimating the pressure. It results in a maximum pore pressure of less than 1 MPa. It has also been shown that the assumption that diffusion in concrete is molecular is unreasonable even when the tortuosity is considered. Molecular diffusivity leads to overestimating the pressure. It results in a maximum pore pressure of 2.7 MPa of which the vapour pressure is 1.5 MPa while the air pressure is 1.2 MPa. Also, the first diffusivity equation, appropriately named 'concrete diffusivity', has been developed specifically for concrete that determines the effective diffusivity of any gas in concrete at any temperature. In thick walls and columns exposed to fire, concrete diffusivity leads to a maximum pore pressures of 1.5 and 2.2 MPa (along diagonals), respectively, that are almost entirely due to water vapour pressure. Also, spalling is exacerbated, and thus higher pressures may occur, in thin heated sections, since there is less of a cool reservoir towards which vapour can migrate. Furthermore, the reduction of the cool reservoir is affected not only by the thickness, but also by the time of exposure to fire and by the type of exposure, i.e. whether the concrete member is exposed to fire from one or more sides. The second investigation is concerned with examining the effects of thickness and exposure time and type. It has been demonstrated that the build up of pore pressure is low in thick members, since there is a substantial cool zone towards which water vapour can migrate. Thus, if surface and/or explosive spalling occur on a thick member, then such spalling must be due to high thermal stresses, but corner spalling is likely to be pore pressure spalling. However, depending on the exposure time and type, the pore pressures can be more than twice those occurring in thick members and thought to be the maximum that can occur so far, and thus the enhanced propensity of pore pressure spalling occurring on thin sections heated on opposite sides has been conclusively demonstrated to be due to the lack of a cool zone towards which moisture can migrate. Expressions were developed for the determination of the maximum pore pressures that can occur in different concrete walls and columns exposed to fire and of the corresponding times of exposure.
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Haq, Inam Ul. "Heat and mass transfer analysis for crud coated PWR fuel." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6373.
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In water-cooled nuclear reactors, various species are present in the coolant, either in ionic solution, or entrained as very fine particles. Most arise from corrosion of primary circuit surfaces, or from chemicals, such as boric acid, lithium hydroxide, zinc and hydrogen, deliberately added to the coolant. These materials deposit on the surfaces of fuel pins, typically in the upper regions of the core, forming what is generally termed “crud”. This thesis reports a study of the thermal-hydraulic consequences of this deposit. These crud deposits are generally found to contain a large population of through-thickness chimneys, and it is believed that this gives rise to a wick-boiling mechanism of heat transfer. A coupled two-dimensional model of the processes of heat conduction, advection and species diffusion in the crud has been developed. An iterative scheme has been employed to solve the set of coupled equations of each process. The wick boiling process has been found to be an efficient heat transfer mode, taking away about 80% of the heat generated. It has also been found that consideration of heat transfer in the clad can increase the predicted solute concentration in the crud. The effects of some important parameters, such as chimney density, chimney radius, porosity of the crud, crud thickness, clad heat flux and boron concentration in the coolant have been investigated. The fuel thermal performance has been characterized in terms of an effective crud thermal conductivity, and the non-linear dependence this has on parameters such as crud thickness and chimney density had been determined. Lastly, it is observed that plausible pore sizes of the crud, coupled with higher temperatures in the crud, may be such that a film of vapour is generated at the base of the crud. Initial estimates are presented of the cladding temperatures and solute concentration that may be generated as a consequence of this vapour layer.
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Jia, Dening. "Heat and mass transfer in pulsed fluidized bed of biomass." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61087.
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Biomass is a promising energy source that has been considered in a variety of thermal conversion processes where fluidized beds with their exceptional heat and mass transfer rates, are often considered as potential candidates. However, the fluidization of biomass is held back by its cohesive nature. This work has demonstrated that pulsed gas flow in fluidized bed is highly effective in overcoming channeling, partial and complete defluidization, without the need for inert bed particles. Both heat transfer and mass transfer were investigated in a pulsed fluidized bed with 0.15 m by 0.10 m rectangular cross-section area, and a fluidized bed with a tapered bottom to improve reactor performance. Biomass used in this work included Douglas fir, pine and switchgrass. Batch drying test was selected as an indirect indicator of gas–solid contact, heat and mass transfer.
Mass transfer was evaluated through batch drying tests, where better gas–solid contact and mass transfer was assessed through the water removal efficiency. An optimum operating condition was identified after analyzing the intricate relationship between pulsation frequency, gas flow rate and the hydrodynamics. A two-phase drying model that linked single-particle mass transfer to macroscopic hydrodynamics in fluidized bed was implemented to verify the effect of flow rate, temperature and biomass properties on drying and mass transfer. Good agreement was observed between the modelled effective diffusivity and experimental results.
Bed-to-surface heat transfer coefficients of all three biomass species in two reactor geometries were measured at various operating conditions. The heat transfer coefficient was influenced greatly by the intensity and frequency of gas pulsation, where both particle convection and gas convection existed. A new heat transfer model was proposed to address the influence of gas pulsation. Modelling results showed good agreement with experimental data.Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate