Proton exchange membrane fuel cell (PEMFC) is a potential alternative energy conversion device for stationary and automotive applications. Wide commercialization of PEMFC depends on progress that can be achieved to enhance its reliability and durability along with cost reduction. It is desirable to operate the PEMFC at uniform local current density and temperature distributions over the surface of the membrane electrode assembly (MEA). Non-uniform distributions of both current and temperature over the MEA could result in poor reactant and catalyst utilization as well as overall cell performance degradation. Local current distribution in the PEMFC electrodes are closely related to operating conditions, but it is also affected by the organization of the reactant flow arrangements in PEMFCs. Reactant depletion and water formation along the flow channel leads to current variation from the channel inlet to the exit, which leads to non-uniformity of local electrochemical reaction activity, and degradation of the cell performance. Flow arrangements between the anode and cathode streams, such as co-, counter- and cross- flow can exacerbate the effect of the non-uniformity considerably, producing complex current distribution patterns over the electrode surfaces. Thus, understanding of the local current density and its spatial characteristics, as well as the temperature distributions under different physical and operating conditions, is crucially important in order to develop optimum design and operational strategies. Despite the importance of the influence of the flow arrangement on the local current and temperature distributions under various operating conditions, few systematic studies have been conducted experimentally to investigate this effect. In this research, an experimental setup with special PEMFC test cells are designed and fabricated in-house, in order to conduct in-situ mapping of the local current and temperature distributions over the electrode surfaces. A segmented flow field plate and the printed circuit board (PCB) technique is used to measure the current distribution in a single PEMFC. In situ, nondestructive temperature measurements are conducted using thermocouples to determine the actual temperature distribution. Experimental studies have been conducted to investigate the effect of different flow arrangements between the anode and cathode (co-, counter-, and cross- flow) on the local current density distribution over the MEA surface. Furthermore, local current distribution has been characterized for PEMFCs under various operating conditions such as reactant stoichiometry ratios, reactant backpressure, cell temperature, cell potentials, and relative humidity for each one of the reactant flow arrangements. The dynamic characteristics of the local current in PEMFC under different operating conditions also have been studied. Temperature distributions along the parallel and serpentine flow channels in PEMFs under various operating conditions are also investigated. All independent tests are conducted to identify and optimize the key design and operational parameters for both local current and temperature distributions. It has been found that the local current density distribution is strongly affected by the flow arrangement between the anode and cathode streams and the key operating conditions. It has also been observed that the counter-flow arrangement generates the most uniform distribution for the current density, whereas the co-flow arrangement results in a considerable variation in the current density from the reactant gas stream inlet to the exit. Low stoichiometry ratio of hydrogen at the anode side has a predominant effect on the current distribution and cell performance. Further, it has been found that the dynamic characteristics and the degree of fluctuation of local current density inside PEMFC are strongly influenced by the crucial operating conditions. In-situ, nondestructive temperature measurements indicate that the temperature distribution inside the PEMFC is strongly sensitive to the cell’s current density. The temperature distribution inside the PEMFC seems to be virtually uniform at low current density, while the temperature variation increases up to 2 oC at the high current density. Finally, the present work contribution related to the local current and temperature distributions is required to understand the effect of each individual or even several operating parameters combined together on the local current and temperature distributions. This will help to develop an optimum design, which leads to enhancing the reliability and durability in operational PEMFCs.

Proton exchange membrane fuel cell (PEMFC) is a potential alternative energy conversion device for stationary and automotive applications. Wide commercialization of PEMFC depends on progress that can be achieved to enhance its reliability and durability along with cost reduction. It is desirable to operate the PEMFC at uniform local current density and temperature distributions over the surface of the membrane electrode assembly (MEA). Non-uniform distributions of both current and temperature over the MEA could result in poor reactant and catalyst utilization as well as overall cell performance degradation. Local current distribution in the PEMFC electrodes are closely related to operating conditions, but it is also affected by the organization of the reactant flow arrangements in PEMFCs. Reactant depletion and water formation along the flow channel leads to current variation from the channel inlet to the exit, which leads to non-uniformity of local electrochemical reaction activity, and degradation of the cell performance. Flow arrangements between the anode and cathode streams, such as co-, counter- and cross- flow can exacerbate the effect of the non-uniformity considerably, producing complex current distribution patterns over the electrode surfaces. Thus, understanding of the local current density and its spatial characteristics, as well as the temperature distributions under different physical and operating conditions, is crucially important in order to develop optimum design and operational strategies. Despite the importance of the influence of the flow arrangement on the local current and temperature distributions under various operating conditions, few systematic studies have been conducted experimentally to investigate this effect. In this research, an experimental setup with special PEMFC test cells are designed and fabricated in-house, in order to conduct in-situ mapping of the local current and temperature distributions over the electrode surfaces. A segmented flow field plate and the printed circuit board (PCB) technique is used to measure the current distribution in a single PEMFC. In situ, nondestructive temperature measurements are conducted using thermocouples to determine the actual temperature distribution. Experimental studies have been conducted to investigate the effect of different flow arrangements between the anode and cathode (co-, counter-, and cross- flow) on the local current density distribution over the MEA surface. Furthermore, local current distribution has been characterized for PEMFCs under various operating conditions such as reactant stoichiometry ratios, reactant backpressure, cell temperature, cell potentials, and relative humidity for each one of the reactant flow arrangements. The dynamic characteristics of the local current in PEMFC under different operating conditions also have been studied. Temperature distributions along the parallel and serpentine flow channels in PEMFs under various operating conditions are also investigated. All independent tests are conducted to identify and optimize the key design and operational parameters for both local current and temperature distributions. It has been found that the local current density distribution is strongly affected by the flow arrangement between the anode and cathode streams and the key operating conditions. It has also been observed that the counter-flow arrangement generates the most uniform distribution for the current density, whereas the co-flow arrangement results in a considerable variation in the current density from the reactant gas stream inlet to the exit. Low stoichiometry ratio of hydrogen at the anode side has a predominant effect on the current distribution and cell performance. Further, it has been found that the dynamic characteristics and the degree of fluctuation of local current density inside PEMFC are strongly influenced by the crucial operating conditions. In-situ, nondestructive temperature measurements indicate that the temperature distribution inside the PEMFC is strongly sensitive to the cell’s current density. The temperature distribution inside the PEMFC seems to be virtually uniform at low current density, while the temperature variation increases up to 2 oC at the high current density. Finally, the present work contribution related to the local current and temperature distributions is required to understand the effect of each individual or even several operating parameters combined together on the local current and temperature distributions. This will help to develop an optimum design, which leads to enhancing the reliability and durability in operational PEMFCs.

Communication by voice is foundational in our society and many rely on their voices for their occupations. Voice disorders affect a significant number of individuals each year, and diagnosis and treatment improvements are therefore sought via advancements in voice research. Contained in this thesis is a description of work intended to contribute to vocal fold research by using synthetic, self-oscillating vocal fold replicas to study the impact of replica vibration on perfusion fluid flow through the replica. Methods for manufacturing vocal fold replicas containing imbedded channels allowing for fluid perfusion are discussed. Experimental procedures developed for delivering perfusion fluid to the imbedded channel at a constant pressure during replica vibration are described. Methods for measuring perfusion parameters of perfusion fluid pressure, imbedded channel diameter, flow rate, and vibration parameters (subglottal pressure, frequency, amplitude, channel length, and glottal width) are detailed. Experiments performed using both stationary and vibrating vocal fold replicas are presented. Correlations between perfusion pressure and channel diameter are discussed. Vibration parameters were correlated to perfusion flow parameters and it is shown that perfusion flow rate through the channels decreased significantly with model vibration. Potential mechanisms for changes in perfusion flow resistance with vibration are discussed and analyzed. Output of a theoretical model, developed to incorporate some of the possible flow resistance mechanisms, was compared to vibrating replica experimental data.

My thesis is divided into three separate parts. The first part is devoted to the theoretical part of the ventilation systems. The second part deals with the determination of the conditions for a number of air exchange, a comparison of three variants of the location of air outlets in dwelling units and the application image airflow from experimental measurements on the common room. The third part is focused on the description of the experimental tasks in the laboratory at the Institute building services.

The main aim of this thesis is to provide and explore main factors that affect a drying process. The first part contains brief description of the drying process and focuses on a convectional industrial drying process. The following section discusses the theory of an experiment planning followed by an experiment design of the compact tumble industrial dryer. The thesis also includes an exact description of the executed experiment, then outputs of the measurements and model characterizing the drying process of the tested dryer. The last part deals with the methodology and recommendations for the measurements in operating conditions.

The present work is a result of collaboration between the LMFA (Laboratoire de Mécanique des Fluides et d'Acoustique, Ecole Centrale de Lyon - France), Snecma and the Cerfacs. It aims at studying the flow in the 3.5-stages high-speed axial compressor CREATE (Compresseur de Recherche pour l'Etude des effets Aérodynamique et TEchnologique - rotation speed: 11543 RPM, Rotor 1 tip speed: 313 m/s), designed and built by Snecma and investigated at LMFA on a 2-MW test rig. Steady measurements, as well as laser velocimetry, fast-response wall static and total pressure measurements have been used to experimentally investigate the flow. The analysis focuses on two main aspects: the study of the flow at stable operating points, with a special interest on the rotor-stator interactions, and the study of the instabilities arising in the machine at low mass flow rates.The description of the unsteady flow field at stable operating points is done through measurements of wall-static pressure, total pressure and velocity, but also total temperature, entropy and angle of the fluid. It is shown that the complexity and unsteadiness of the flow in a multistage compressor strongly increases in the rear part of the machine, because of the interactions between steady and rotating rows. Therefore, a modal analysis method developed at LMFA and based on the decomposition of Tyler and Sofrin is presented to analyze these interactions. It is first applied to the pressure measurements, in order to extract the contributions of each row. It shows that all the complex pressure interactions in CREATE can be reduced to three main types of interactions. The decomposition method is then applied to the entropy field extracted from URANS CFD calculations performed by the Cerfacs, in order to evaluate the impact of the interactions on the performance of the machine in term of production of losses.The last part of this work is devoted to the analysis of the instabilities arising in CREATE at low mass flows. It shows that rotating pressure waves appear at stable operating points, and increase in amplitude when going towards the surge line, until reaching a critical size provoking the onset a full span stall cell bringing the machine to surge within a few rotor revolutions. The study of these pressure waves, and the understanding of their true nature is achieved through the experimental results and the use of some analytical models. A precise description of the surge transient through wall-static pressure measurements above the rotors is also provided, as well as a description of a complete surge cycle. An anti-surge control system based on the detection of the amplitude of the pressure waves is finally proposed.

La simulation détaillée au niveau carte de ces nouveaux types de packages est quasiment impossible du fait de la limitation des moyens de calculs actuels. En outre, dans la plupart des cas de conception électronique, seule l’estimation des températures en quelques points est intéressante. Une étude détaillée au niveau composant n’est pas nécessairement pertinente. Il faut donc un compromis entre faisabilité et/ou rapidité des calculs et une précision sur les paramètres importants. Une alternative est de trouver des modèles comportementaux équivalents aux modèles détaillés, capable de reproduire son comportement thermique aux points cruciaux. C’est dans cette optique que le projet européen DELPHI (Development of libraries of physical models of electronic components for an integrated design environment) a été initié en 1993. L’objectif de ce projet était de pouvoir générer un modèle compact à partir d’un modèle détaillé d’un composant électronique. Celui-ci a ainsi abouti à une standardisation du processus de génération des modèles mis en oeuvre. Néanmoins, les avancées issues de ce projet sont limitées aux composants mono-puces et à leur comportement thermique en régime permanent. L’objectif de cette thèse est d’avoir une approche multi-échelle de la génération de modèles compacts et leur interaction avec la carte. La modélisation multi-échelle consiste à la génération de modèles mono-puces ou multi-puces et leur réutilisation éventuelle dans des systèmes plus complexes tels que le PCB ou les « System-In-packages ». / This thesis is dedicated to the generation of behavioral thermal model for electronic component having multiple active sensitive chips. This innovative study focuses on the necessary improvements of the concept of steady-state and dynamic compact model in order to elaborate pertinent and accurate modeling practical techniques. To help the electronic designer to early identify the overheated electronic components, the purpose is to generate simplified models, capable to mimic the thermal behavior of sophisticated detailed models. These simplified or compact models using well-known thermal resistances network replicate the thermal path from the most sensitive elements to the external package surfaces and enable to accurately predict their temperatures as well as the case heat flow rates. Preliminary evaluations performed on the popular, plastic Quad Flat-pack No lead package family showed that the simplest network definition, restricted to the heating source and two external surfaces, is always insufficient to properly characterize the thermal response of real device. So our development of steady-state compact thermal model (CTM) for electronic component is based on a process flow defined by the European project DELPHI which was revised by the presented work to address multi-chip components. DELPHI style compact thermal model presents an enlarged node number, especially for the component external surfaces which are divided in a set of relevant areas.

Generation of electricity from ocean waves has seen increasing research and commercial interest in recent years. The development of projects of several hundred megawatts rated capacity is now being considered. There is a clear need for improved understanding of the environmental impact of large-scale wave energy extraction, particularly in nearshore regions where sediment transport and cliff erosion may be affected. This thesis investigates the change in nearshore wave conditions and sediment transport due to energy extraction by long strings of wave energy devices. The influence of wave energy converter (WEC) arrays has been studied using transmission coefficients implemented within a spectral wave model. It is shown that the breaking wave height nearshore is larger (5%) if transmission is defined as frequency dependent. This is due to the energy dissipation processes associated with different wave frequencies. Linear wave theory is employed to determine frequency dependent transmission and reflection coefficients across a line of wave energy devices based onthe amplitude of scattered and radiated waves. This approach is compared with experimental measurements of the wave field in the vicinity of an array of five heaving floats. The transmitted wave amplitude is predicted with reasonable accuracy but additional numerical damping is required to predict the measured float response amplitude. This comparison indicates that linear analysis is an acceptable approach for predicting float response and wave field in the vicinity of the array for a certain range of conditions. Linear wave analysis is subsequently applied to investigate the variation of transmission coefficients with distance inshore of a long array of heaving WECs undergoing free response and with damping specified to optimise power extraction. A method is presented for identifying representative transmission and reflection coefficients such that change in wave energy is equal to energy extraction by the devices. These coefficients are employed to quantify the change in nearshore conditions due to deployment of a long line of wave devices at a site near the East Anglian coastline. Wave conditions are modelled at 12 points along the shoreline over a 140 year period and significant wave height reductions up to 30% were obtained. Importantly, changes in nearshorewave direction are also observed. Analysis using the sediment transport model SCAPE (Soft Cliff and Platform Erosion model) indicates that the introduction of the array reduces both the sediment transport rate and cliff recession rate by an average of 50%.

The dissertation thesis is focused on thermal insulating properties of reflective insulation under boundary conditions typical for low-energy buildings. In the introductory part of this thesis the attention is focused on the heat transfer process. There is described primarily heat transfer by radiation. There is also described the reflective insulation and the methods of determination their thermal performance. The remaining part of the thesis deals with the analysis of the results obtained in experimental measurements. Measurement results are compared with the calculation model. Conclusions for technical practice including possibilities of further research are summarized in the final section.

The main aim of this thesis is to explore fouling of air ducts and its influence on energy consumption of HVAC systems. The first part focuses on typical parts that create the IAQ in buildings and on evaluating energy consumption of air transportation. The following section deals with the theories of fluid flow, flow regimes and pressure losses that are created as a side effect. The thesis outlines possible methods of assessing the impact of pollution with an emphasis on pressure losses and their influence on the fan power consumption. The actual experimental measurement, conducted in a selected industrial plant, is focused on an influence of cleanness of textile diffuser on HVAC device power consumption. For the further research of this process, measuring equipment with suitable measurement method is designed and constructed.