<p dir="ltr">An adaptive mesh refinement strategy for shock dominated flows encompassing multiple types of fluids and fluid features. </p>

Les matériaux hygroscopiques, et tout particulièrement le bois et ses dérivés possèdent des propriétés complexes rendant difficile la modélisation des transferts couplés de chaleur et de masse dans les parois incluant ces matériaux. De ce fait, très peu d'outils numériques sont aujourd'hui capables de prédire correctement la performance hygrothermique de l'habitat bois. L'objectif de ce travail est de caractériser expérimentalement les transferts chaleur-masse dans les parois des constructions bois afin de valider un outil numérique destiné à simuler le comportement hygrothermique des parois comportant des matériaux hygroscopiques. Dans un premier temps, les notions théoriques et les études antérieures sur les transferts couplés chaleur - masse sont présentés. Ensuite, nous donnons un descriptif détaillé du dispositif expérimental conçu pour caractériser les transferts couplés chaleur-masse dans les parois. Les expériences de caractérisation des performances hygrothermiques des parois fournies par les industriels partenaires du projet TRANSBATIBOIS dans lequel s'inscrit cette thèse sont également abordées. Nous détaillons par la suite les expériences réalisées ainsi que la phase de confrontation des résultats expérimentaux avec les résultats prédits par le code numérique BuildingPore et l'outil commercial WUFI. La troisième partie de ce travail est consacrée aux expérimentations à l'échelle de l'enveloppe. Nous y présentons une analyse de la performance hygrothermique et des consommations énergétiques des constructions bois à travers le suivi de modules-test exposés au climat extérieur. La dernière partie du travail est consacrée aux dispositifs de suivi de bâtiments. / Coupled heat and moisture transfer through hygroscopic materials, particularly wood and wood-based products are difficult to model. This is partly due to some specific and complex properties of these materials that are often not included in numerical models. Currently, only a few numerical models are able to predict accurately the hygrothermal performance of wooden building envelope. The aim of this work is to assess the heat and moisture transfer in wooden building envelope through experiments and validate the prediction capacity of a numerical model developed to simulate hygrothermal behavior of envelope including wooden materials. After giving a theoretical reminder of the coupled heat and moisture transfer through building envelope and reporting the results of previous studies in this field, we will give details of the experimental investigation on heat and moisture transfer through timber walls. Firstly, the experimental apparatus used for the wall tests is presented. Then, we will analysis the hygrothermal performance of wooden walls provided by the partners of the TRANSBATIBOIS project in which this work was achieved. Experimental works achieved for Buildingpore model validation and results of the comparisons between experimental assessment and numerical predictions with Buildingpore and WUFI are also reported. The third part of this study deals with the experimental assessment of wooden building envelopes exposed to climatic conditions. An analysis of the hygrothermal performance and the energy consumption of wooden test-cells is performed and reported in this part. The latest part concerns experimental works on buildings.

Master of Science / Department of Mechanical and Nuclear Engineering / Steven J. Eckels / Membrane dehumidification and evaporative cooling applications have the potential to significantly improve the energy efficiency of air conditioning equipment. The use of wire mesh media in such membrane applications is feasible but has not been studied extensively. Therefore, the aim of this work is to investigate the heat and mass transfer performance of several different wire mesh media in membrane based dehumidification and evaporative cooling. There were six wire mesh membranes tested in an experimental facility. The wire mesh membranes vary with respect to percent open area, wire diameter, pore size and material. Two non-permeable, solid membranes were also tested in the facility and compared with the wire mesh membranes. The test section of the experimental facility consists of a narrow air duct and a plate apparatus. The membrane samples were fashioned into rectangular plates and installed into the test section. The plate membranes separate liquid water and air flow streams. The inlet air temperature and humidity are altered to produce condensation or evaporation at the membrane surface. The average convective heat and mass transfer coefficient of the air boundary layer is measured for each of the experimental plates. Membrane based dehumidification and evaporative cooling were accomplished using the wire mesh media. However, the wire mesh membranes did not exhibit any significant differences in their performance. The mesh plates were compared with the solid plate membranes and it was discovered that the solid plates exhibited significantly higher heat transfer coefficients during condensation conditions. This result most likely is due to the formation of large water droplets on the solid plates during condensation. The experimental data is then compared to analytical predictions of the heat and mass transfer coefficients developed from several heat transfer correlations and by invoking the heat and mass transfer analogy. The experimental data is also compared directly with the heat and mass transfer analogy. It was found that the data did not compare well with the heat and mass transfer analogy. This result is attributed to the fact that the membrane surface limits the amount of direct exposure to the gas-liquid interface.

<div>In order to better understand and quantify the effect of instabilities in systems utilizing flow boiling heat transfer, the present study explores dynamic results for pressure drop, mass velocity, thermodynamic equilibrium quality, and heated wall temperature to ascertain and analyze the dominant modes in which they oscillate. Flow boiling experiments are conducted for a range of mass velocities with both subcooled and saturated inlet conditions in vertical upflow, vertical downflow, and horizontal flow orientations. High frequency pressure measurements are used to investigate the influence of individual flow loop components (flow boiling module, pump, pre-heater, condenser, etc.) on dynamic behavior of the fluid, with fast Fourier transforms of the same used to provide critical frequency domain information. Conclusions from this analysis are used to isolate instabilities present within the system due to physical interplay between thermodynamic and hydrodynamic effects. Parametric analysis is undertaken to better understand the conditions under which these instabilities form and their impact on system performance. Several prior stability maps are presented, with new stability maps provided to better address contextual trends discovered in the present study.</div><div>Further, this study utilizes experimental results for vertical upflow boiling of FC-72 in a rectangular channel with finite inlet quality to investigate Density Wave Oscillations (DWOs) and assess their potential impact on design of two-phase systems for future space missions. High-speed flow visualization image sequences are presented and used to directly relate the cyclical passage of High and Low Density Fronts (HDFs and LDFs) to dominant low-frequency oscillations present in transient pressure signals commonly attributed to DWOs. A methodology is presented to determine frequency and amplitude of DWO induced pressure oscillations, which are then plotted for a wide range of relevant operating conditions. Mass velocity (flow inertia) is seen to be the dominant parameter influencing frequency and amplitude of DWOs. Amplitude of pressure oscillations is at most 7% of the time-averaged pressure level for current operating conditions, meaning there is little risk to space missions. Reconstruction of experimental pressure signals using a waveform defined by frequency and amplitude of DWO induced pressure fluctuations is seen to have only moderate agreement with the original signal due to the oversimplifications of treating DWO induced fluctuations as perfectly sinusoidal in nature, assuming they occur at a constant frequency value, and neglecting other transient flow features. This approach is nonetheless determined to have potential value for use as a boundary condition to introduce DWOs in two-phase flow simulations should a model be capable of accurately predicting frequency and amplitude of oscillation.</div><div>Additionally, this study presents a new mechanistic model for Density Wave Oscillations (DWOs) in vertical upflow boiling using conclusions drawn from analysis of flow visualization images and transient experimental results as a basis from which to begin modeling. Counter to many prior studies attributing DWOs to feedback effects between flow rate, pressure drop, and flow enthalpy causing oscillations in position of the bulk boiling boundary, the present instability mode stems primarily from body force acting on liquid and vapor phases in a separated flow regime leading to liquid accumulation in the near-inlet region of the test section, which eventually departs and moves along the channel, acting to re-wet liquid film along the channel walls and re-establish annular, co-current flow. This process was modeled by dividing the test section into three distinct control volumes and solving transient conservation equations for each, yielding predictions of frequencies at which this process occurs as well as amplitude of associated pressure oscillations. Values for these parameters were validated against an experimental database of 236 FC-72 points and show the model provides good predictive accuracy and capably captures the influence of parametric changes to operating conditions.</div><div>Also, this study shows analysis of pressure signals in condensing systems reveal the presence of relevant oscillatory phenomena during flow condensation as well, which may impact performance in applications concerned with precise system control. Towards this end, the present study presents results for oscillatory behavior observed in pressure measurements during flow condensation of FC-72 in a smooth circular tube in vertical upflow, vertical downflow, and horizontal flow orientations. Dynamic behavior observed within the test section is determined to be independent of other components within the flow loop, allowing it to be isolated and interpreted as resulting from physical aspects of two-phase flow with condensation. The presence of a peak oscillatory mode (one of significantly larger amplitude than any others present) is seen for 72% of</div><div>vertical upflow test cases, 61% of vertical downflow, and 54% of horizontal flow. Relative intensities of this peak oscillatory mode are evaluated through calculation of Q Factor for the corresponding frequency response peak. Frequency and amplitude of peak oscillatory modes are also evaluated. Overall, vertical upflow is seen to exhibit the most significant oscillatory behavior, although in its maximum case amplitude is only seen to be 7.9% of time-averaged module inlet pressure, indicating there is little safety risk posed by oscillations under current operating conditions. Flow visualization image sequences for each orientation are also presented and used to draw parallels between physical characteristics of condensate film behavior under different operating conditions and trends in oscillatory behavior detected in pressure signals</div><div>Further, the present work outlines a new methodology utilizing temperature and pressure measurements to identify condensation flow regimes. For vertical upflow condensation, amplitude of dynamic temperature and pressure oscillations are shown to clearly indicate transition from counter-current flow regimes (i.e., falling film, oscillating film, flooding) to annular, co-current flow (climbing film flow regime). In horizontal flow condensation, standard deviation between multiple thermocouple measurements distributed around the tube circumference was calculated at all axial (stream-wise) measurement locations. High values of standard deviation are present for stratified flow (stratified flow, wavy-stratified, plug flow), while axisymmetric flow regimes (i.e., slug flow, annular flow) yield significantly lower values. Successful development of this technique represents a valuable contribution to literature as it allows condensation flow regime to be identified without the often-costly restriction of designing a test section to allow optical access. Identified flow regimes in both vertical upflow and horizontal flow orientations are compared to regime maps commonly found in the literature in pursuit of optimum performing maps.</div><div>Finally, the present study aims to better analyze the influence of body force on flow condensation heat transfer by conducting tests at multiple orientations in Earth’s gravity. Dielectric FC-72 is condensed in a smooth stainless-steel tube with 7.12 mm diameter and 574.55 mm condensing length by counterflow of cooling water across the outer surface of the tube. Test conditions span FC-72 mass velocities of 50.3 – 360.3 kg/m2s, test section inlet pressures of 127.0 – 132.1 kPa, and test section inlet thermodynamic equilibrium qualities of 0.13 – 1.15. A subset of data gathered corresponding to axisymmetric, annular condensation heat transfer is identified and a detailed methodology for data reduction to calculate heat transfer coefficient presented. Uncertainty analysis is also presented and indicates channel average heat transfer coefficients are calculated within ±3.6% to ±26.7% (depending on operating conditions). Analysis of parametric trends for condensation heat transfer reveals the dominant influence of mass velocity (flow inertia), secondary influence of vapor mass fraction (thermodynamic equilibrium quality), and strong dependence on orientation (body force) at low mass velocities. At higher mass velocities results for all orientations investigated begin to converge, indicating body force independent annular condensation heat transfer is achieved. Separated Flow Model predictions of vertical downflow condensation heat transfer provide reasonable agreement with experimental results, evidence by a Mean Absolute Error (MAE) of 31.2%. Evaluation of condensation heat transfer correlations for horizontal flow reveal most correlations struggle for cases with high liquid content. Specific correlations are identified for superior accuracy in predicting the measured data.</div>

Neste trabalho, foi estudado o desempenho de um sistema constituído de torres de resfriamento e a sua integração em uma planta industrial de hidrogenação de butadieno. Caracterizou-se o desempenho das torres de resfriamento com base em um modelo fenomenológico, cujos parâmetros foram obtidos a partir da medição de variáveis operacionais reais. O processo de hidrogenação foi configurado em um simulador de processos, sendo o caso base estabelecido nas condições de projeto. Elaborou-se um módulo específico referente às torres de resfriamento, que foi integrado ao processo configurado no simulador. Em seguida, analisaram-se as interações das condições operacionais da torre de resfriamento no desempenho do processo industrial. / In the present work, the performance of a system composed of a cooling tower integrated in butadiene hydrogenation plant was studied. An experimental investigation was made to characterize the cooling towers based on a phenomenological model and in real process conditions. The hydrogenation process was configured on a process simulator and design specifications were considered as base case. A cooling tower module was developed and integrated to the process simulator. The interaction of the cooling tower system and the plant operation was investigated.

The study is focused on study of surface and interfacial properties of oil at high temperatures, to understand the mechanisms of heat transfer and oil absorption during frying

Com base em um modelo fenomenológico e a partir de dados experimentais obtidos numa planta piloto, foi obtida uma correlação entre o desempenho de uma torre de resfriamento em função das principais variáveis de processo: fluxos mássicos do gás e da água pela torre, e temperatura de entrada da água. Os resultados apresentaram boa consistência, comparados com os da literatura. A metodologia desenvolvida pode, com relativa facilidade, ser aplicada para torres de resfriamento industriais, pois se baseia em medidas de variáveis, factíveis em termos práticos. Efetuou-se também um estudo paralelo com base em modelagem e simulações matemáticas do comportamento de uma torre de resfriamento de água em condições severas, com temperatura da água de alimentação superior a 50°C. Constatou-se que o coeficiente de transporte de massa na torre de resfriamento aparentemente não é afetado. / Cooling towers are widely used in many industrial and utility plants and its thermal performance is of vital importance. In the present work, using a phenomenological model and by experiments carried on over a pilot installation, the mass transfer coefficient dependence of air and water flow rates and inlet cooling water temperature is determined. The approach proposed may be useful in addition for characterization of industrial cooling towers since it depends on temperature and flow rate measurement usually available in typical plants. A parallel study concerning high mass transfer rate theory is accomplished. Through mathematical modeling and simulations based on this study no influence is detected on the mass transfer coefficient in the cooling tower, operating under harsh conditions with inlet water temperature up to 90°C.

<p>The thesis covers the following topics:</p> <p>1. aggregation and size effect on metal-polymer nanocomposite thermal interface materials</p> <p>2. diffusion limited cluster aggregation lattice simulation on thermal conductivty</p> <p>3. thermal interfacial resistance reduction between metal and dielectric materials by inserting an intermediate metal layer</p> <p>4. absence of coupled thermal interfaces in al2o3/ni/al2o3 sandwich structure</p> <p>5. ultra-efficient low-cost radiative cooling paints</p>

Disponibilidade dos recursos energéticos junto com o despertar da consciência ambiental criaram um interesse por uma condição climática sensível compatível com os recursos disponíveis. Dentro desse cenário o trabalho se volta à necessidade de se criarem e manterem ambientes industriais termicamente adequados aos processos de produção para minimizar as interferências que as condições ambientais exercem sobre os custos dos processos de produtivos e sobre o consumo energético. Os sistemas de resfriamento evaporativo, por sua vez, têm sido a ferramenta de maior potencial de aplicação na criação de ambientes termicamente adequados aos processos. Este modelo revisto de conforto térmico nos coloca um passo à frente para o aumento eficiência energética na construção de projeto de climatização vinculados a temperaturas interiores que atendam conjuntamente tanto aos ocupantes como às atividades que desenvolvem no interior da área climatizada. Apesar de esse sistema apresentar vantagens operacionais, quando comparado a outros sistemas convencionais, existem certas limitações no seu desempenho. Uma das maiores dificuldades das instalações destes sistemas reside na existência de incertezas em qualquer resultado. Possibilitar um controle dos parâmetros, minimizando os erros de aplicação, evitando criar no ambiente um desconforto de tal grau que inviabilize sua aplicação, é o fundamento deste trabalho. A busca passa a ser pela garantia da aceitabilidade dos resultados do sistema projetado e seus limites de aplicabilidade. O estudo das variáveis que interferem no processo do resfriamento por micro aspersão permitiu desenvolver um processo que alterara esses parâmetros durante o funcionamento do sistema, interferindo, conforme a necessidade no seu desempenho, garantindo a completa evaporação da água micro aspergida. / Energy resources along with an environmental conscience awakening has created an interest in sensitive climate together with a more understanding regarding the use of available resources. Inside this scenario our work focus on the needs of creating and maintaining industrial environments thermally suited to these production processes that seeking to minimize interference that environmental conditions have on the costs of production processes and energy consumption. Evaporative cooling systems, in turn, has been a interesting tool to be used in the creation of thermally suitable environments to these processes. This new revised thermal comfort model puts us a step forward to increase energy efficiency in elaborating air treatment projects linked to indoor temperatures that meet both the occupants and the activities that develop inside the controlled area. Although this system has operational advantages when compared to other conventional systems, there are some limitations in their performance. A major difficulty of the installation envolving these systems is about the existence of uncertainty in any results. To allow the control of these parameters in order to minimize the errors in this kind of application and to avoid creating environmental discomfort to such a degree that prevent the implementation, it is the foundation of this work. The search is to ensure the acceptability of the results of the system designed and their limits of applicability. The study of the variables that affect the cooling process by misting allowed us to develop a process that altered these parameters during operation of the system, interfering, as required in its performance, ensuring complete evaporation of water applied by misting in the area.

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’ergonomie. / The 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.