No / Auditory signals have been shown to exert a marked influence on visual perception in a wide range of tasks. However, the mechanisms of these interactions are, at present, poorly understood. Here we present a series of experiments where a temporal cue within the auditory domain can significantly affect the localisation of a moving visual target. To investigate the mechanism of this interaction, we first modulated the spatial positional uncertainty of the visual target by varying its size. When visual positional uncertainty was low (small target size), auditory signals had little or no influence on perceived visual location. However, with increasing visual uncertainty (larger target sizes), auditory signals exerted a significantly greater influence on perceived visual location. We then altered the temporal profile of the auditory signal by modulating the spread of its Gaussian temporal envelope. Introducing this temporal uncertainty to the auditory signal greatly reduced its effect on visual localisation judgements. These findings support the view that the relative uncertainty in individual sensory domains governs the perceptual outcome of multisensory integration.

This thesis introduces and describes a new experimental setup for examining the effects of pulsating inflow to a ventilated enclosure. The study aimed to test the hypothesis that a pulsating inflow has potential to improve ventilation quality by reducing the stagnation zones through enhanced mixing. The experimental setup, which was a small-scale, two-dimensional (2D), water-filled room model, was successfully designed and manufactured to be able to capture two-dimensional velocity vectors of the entire field using Particle Image Velocimetry (PIV). Using in-house software, it was possible to conclude that for an increase in pulsation frequency or alternatively in the flow rate, the stagnation zones were reduced in size, the distribution of vortices became more homogeneous over the considered domain, and the number of vortices in all scales had increased. Considering the occupied region, the stagnation zones were moved away in a favorable direction from a mixing point of view. In addition, statistical analysis unveiled that in the far-field occupied region of the room model, stronger eddies were developed that we could expect to give rise to improved mixing. As a fundamental experimental study performed in a 2D, small-scale room model with water as operating fluid, we can logically conclude that the positive effect of enhanced mixing through increasing the flow rate could equally be accomplished through applying a pulsating inflow. In addition, this thesis introduces and describes an experimental setup for study of air flow over a wall-mounted radiator in a mockup of a real room, which has been successfully designed and manufactured. In this experimental study, the airflow over an electric radiator without forced convection, a common room-heating technique, was measured and visualized using the 2D PIV technique. Surface blackening due to particle deposition calls for monitoring in detail the local climate over a heating radiator. One mechanism causing particle deposition is turbophoresis, which occurs when the flow is turbulent. Because turbulence plays a role in particle deposition, it is important to identify where the laminar flow over radiator becomes turbulent. The results from several visualization techniques and PIV measurements indicated that for a room with typical radiator heating, the flow over the radiator became agitated after a dimensionless length, 5.0–6.25, based on the radiator thickness. Surface properties are among the influencing factors in particle deposition; therefore, the geometrical properties of different finishing techniques were investigated experimentally using a structured light 3D scanner that revealed differences in roughness among different surface finishing techniques. To investigate the resistance to airflow along the surface and the turbulence generated by the surfaces, we recorded the boundary layer flow over the surfaces in a special flow rig, which revealed that the types of surface finishing methods differed very little in their resistance and therefore their influence on the deposition velocity is probably small. / Det övergripande syftet med den första studien i avhandlingen var att undersöka hypotesen att ett pulserande inflöde till ett ventilerade utrymme har en potential till att förbättra ventilationens kvalitet genom att minska stagnationszoner och därigenom öka omblandningen. För genomförande av studien byggdes en experimentuppställning i form av en tvådimensionell (2D) småskalig modell av ett ventilerat rum. Strömningsmediet i modellen var vatten. Det tvådimensionella hastighetsfältet registrerades över hela modellen med hjälp av Particle Image Velocimetry (PIV). Vid ett stationärt tillflöde bildas ett stagnationsområde i centrum av rumsmodellen. Vid ett pulserade inflöde genererades sekundära virvlar. Med en egen utvecklad programvara var det möjligt att kvantifiera statistiken hos virvlarna. Det pulserade inflödet gjorde att inom området där det vid stationärt tillflöde fanns en stagnationszon ökade antalet virvlar i alla storlekar och fördelningen av virvlar blev mera homogen än tidigare. Detta kan förväntas ge upphov till förbättrad omblandning. Baserat på en grundläggande experimentell studie utförd i en småskalig tvådimensionell rumsmodell med vatten som strömningsmedium kan vi logiskt dra slutsatsen att ett pulserande tilluftsflöde har en potential att förbättra omblandningen.  I en fortsatt studie i avhandlingen visuliserades och mättes hastighetsfältet och därefter beräknades statistiska värden av exempelvis medelhastighet, standardavvikelse och skjuvspänning hos hastighetsfluktuationerna i luftströmmen över en väggmonterad radiator med 2D-PIV-teknik.  Bakgrunden till studien är att en bidragande orsak till partikelavsättning på väggytor är turbofores som uppträder vid en turbulent luftström. Studien genomfördes genom uppbyggnad av en fullskalig rumsmodell. Eftersom turbulens spelar en roll vid partikelavsättning genom turbofores är det viktigt att identifiera var det laminära flödet över radiatorn blir turbulent. Resultaten baserat på visualisering och PIV-mätningar indikerade att, för ett rum med denna typ av radiatoruppvärmning, blev flödet över radiatorn turbulent efter en dimensionslös längd lika med 5,0‒6,25 gånger radiatorns tjocklek. Ytors egenskaper är viktiga vid partikelavsättning. Därför har de geometriska egenskaperna hos några olika metoder för ytbehandling undersökts experimentellt med hjälp av en scanner för strukturerat 3D-ljus. Resultaten visar på skillnader i ytråhet hos de olika ytbehandlingsmetoderna. För att undersöka motståndet mot luftströmning längs ytan och den turbulens som genereras av ytorna registrerade vi gränsskiktsflödet över ytorna i en speciell luftströmningsrigg. Detta påvisade att motståndet hos de olika typerna av ytbehandlingsmetoder skilde sig mycket litet åt och därför är troligt vid deras påverkan på depositionshastigheten mycket liten. / <p>QC 20150525</p>

Un modèle numérique d’un arc électrique diffus dans un disjoncteur à vide à champ magnétique axial (AMF) a été développé dans le but de mieux comprendre à terme la transition d’un mode de fonctionnement diffus de l’arc vers un mode plus concentré. Le comportement du plasma d’arc a été simulé depuis la sortie de la zone de mélange cathodique jusqu’à l’entrée de la gaine anodique. Le modèle bidimensionnel est basé sur un système d’équations hydrodynamiques à deux fluides non magnétisés (ions et électrons), incluant les équations de conservation d’énergie ionique et électronique. Il est démontré que les processus d’ionisation et de recombinaison et les effets visqueux sont négligeables. Les transferts radiatifs ne sont pas considérés en première approximation. Outre les forces dues au champ AMF, le modèle inclut les forces dues aux trois composantes du champ magnétique induit par l’arc. Deux régimes d’écoulement des ions, supersonique (aux faibles densités de courant) et subsonique (aux fortes densités de courant), sont considérés. Près de la cathode, les conditions aux limites sont spécifiées à partir de résultats de la littérature. A proximité de l’anode, elles sont basées sur une description simplifiée de la gaine anodique. Les résultats de simulation présentés mettent en évidence une constriction du courant et un comportement différent des ions aux faibles et aux fortes densités de courant, et renseignent sur l’influence de divers paramètres (intensité du courant, distance interélectrode). Ce travail présente également une étude expérimentale, basée sur des visualisations par vidéo rapide de l’arc et des mesures pyrométriques de la température de la surface de l’anode / A model of a diffuse arc in a vacuum circuit breaker with an axial magnetic field (AMF) has been developed with the ultimate aim to better understand the transition of the arc from a diffuse mode to a more confined mode. The interelectrode plasma is simulated from the exit of the mixing region on the cathode side to the entrance of the anode sheath. The two-dimensional model is based on the solution of a system of two-fluid (ions and electrons) hydrodynamic equations, including in particular the energy balance equations relative to both the ions and the electrons, which are treated as non-magnetized particles. It is demonstrated that ionisation and recombination processes, as well as viscous effects, can be neglected. Radiation losses are not taken into account in a first approximation. In addition to the forces due to the AMF, the model considers the forces created by the three components of the magnetic field induced by the arc current. The possibility of both supersonic (at low current density) and subsonic (at high current density) ionic flow regimes is considered. On the cathode side, the boundary conditions are specified using results from the literature. On the anode side, they are based on a simplified description of the anode sheath. The simulation results presented show a constriction of the current lines, emphasize the differences in the behaviour of the ions at low and high current densities, and provide some insight on the influence of various operating parameters (arc current, gap length). The present work comprises also an experimental study, based on high-speed camera visualisations of the arc and measurements of the temperature at the anode surface

Cette thèse apporte des éléments sur la compréhension de la gestion de l'eau et de ses effets sur les performances électriques d'une PEMFC au moyen de modélisations multi-échelle des transferts. Une analyse du transport couplé de charges et de matière dans les pores de la membrane est proposée. La présence d'eau liquide est prise en compte dans les GDL (écoulements diphasiques) et les couches actives (noyage). Le couplage de ces modèles à une description des transferts de matière le long des canaux d’alimentation permet de mettre en évidence une répartition non-uniforme des concentrations en eau, des flux et donc de la densité de courant. Les résultats numériques sont comparés à des données expérimentales (coefficient de partage de l'eau et performance électrique locale) obtenues au laboratoire sur deux piles. Ceci permet de valider les modèles de fonctionnement du cœur de pile et d'alimenter la réflexion sur la connaissance et la modélisation des transferts d'eau dans le cœur de pile / This works contributes to the understanding of water management of polymer electrolyte membrane fuel cell and of its links with the electrical performances. More specifically, the manuscript deals with the multi-scale modelling of transport phenomena. An analysis of coupled mass and charge transfer in the pores of a polymer membrane is presented. The presence of liquid water is considered in the GDL (two-phase flow) and in the active layers (flooding). The description of these phenomena is associated with that of gas depletion along the bipolar plate channels. This allows to emphasize the non-uniformity of water concentration, of the fluxes and as a consequence, of current density. The numerical results are compared with experimental data (water transport coefficient, local electrical performances) measured on two different fuel cells. This comparison validates at least partially the numerical models and provides further information for the analysis of water management within PEMFC

Le présent travail de recherche concerne l'étude de la convection de Rayleigh-Bénard-Marangoni dans un récipient cylindrique doté d'un fond en substrat solide. Le substrat solide est chauffé sur sa face inférieure par un flux de chaleur localisé. L'étude comporte deux parties : La première partie du travail consiste en une modélisation physique du problème associée à des simulations numériques. Les équations de Navier-Stokes et de l'énergie sont résolues en 3D par une méthode de volumes finis. Un transfert de chaleur conjugué solide-liquide est considéré. Des morphologies originales de cellules (type et nombre) sont observées, elles dépendent des conditions géométriques, des nombres adimensionnels qui régissent la physique de l'écoulement (nombre de Prandtl, de Rayleigh et de Marangoni ainsi que du rapport des conductivités thermiques du substrat solide et du fluide). Les transferts de chaleur sont aussi évalués pour chaque cas d'étude. Dans la deuxième partie, nous allons détaillons une étude expérimentale de la convection de Rayleigh-Bénard-Marangoni dans la même configuration que celle étudiée numériquement. Les structures convectives et leurs évolutions sont étudiées à partir d’images relevées par thermographie infra-rouge. Différents modes d'organisation des cellules convectives ont pu être mis en évidence pour ce type de chauffage à flux thermique imposé non uniforme. / The present research work concerns the study of Rayleigh-Bénard-Marangoni convection in a cylindrical container with a solid substrate base. This solid substrate is heated by a localized heat flux on its underside. The study is divided into two parts : The first part of the work consists of a physical modelling of the problem associated with numerical simulations. The Navier-Stokes and energy equations are solved by using a 3D finite volume method. A conjugate solid-liquid heat transfer is considered. Original morphology of cells (type and number) are observed, they are linked to the geometrical conditions, the dimensionless numbers which govern the physical problem (Prandtl, Rayleigh and Marangoni numbers and the ratio of solid substrate to liquid thermal conductivities). The heat transfers are also evaluated in each case. In the second part of the work, we present an experimental study of Rayleigh-Bénard-Marangoni convection in the same configuration as that studied numerically. Convective structures and their evolutions are studied from images recorded by infrared thermography. Different modes of organization of convective cells have been highlighted for this type of heating with imposed non-uniform heat flux.

Les opérations géométriques appliquées aux maillages 3D introduisent des dis torsions géométriques qui peuvent être visibles pour un observateur humain. Dans cette thèse, nous étudions l’impact perceptuel de ces distorsions. Plus précisément, notre objectif est de calculer le seuil à partir duquel les distorsions géométriques locales deviennent visibles. Afin d’atteindre notre but, nous définissons tout d’abord des caractéristiques perceptuelles pour les maillages 3D. Nous avons ensuite effectué une étude expérimentale des propriétés du système visuel humain (sensibilité au contraste et effet du masquage visuel) en observant un maillage 3D. Les résultats de ces expériences sont finalement utilisés pour proposer un algorithme qui calcule le seuil de visibilité relatif à une distorsion locale. L’algorithme proposé s’adapte aux différentes conditions d’affichage (résolution et taille de l’écran), d’illumination et au type de rendu. Enfin, nous montrons l’utilité d’un tel algorithme en intégrant le seuil de visibilité dans le pipeline de plusieurs opérations géométriques (ex: simplification, subdivision adaptative) / Geometric operations applied to a 3D mesh introduce geometric distortion in the form of vertex displacement that can be visible to a human observer. In this thesis, we have studied the perceptual impact of these geometric distortions. More precisely, our goal is to compute the threshold beyond which a local geometric distortion becomes visible. In order to reach this goal, we start by evaluating perceptually relevant properties on 3D meshes. We have then performed a series of psychophysical experiments in which we measured the visibility threshold relative to various properties of the Human Visual System (contrast sensitivity and visual masking). The results of these experiments allowed us to propose an algorithm that computes the visibility threshold relative to a local geometric distortion. This algorithm is capable of adapting to the different display condition of 3D meshes (resolution, display size, illumination condition and rendering). Finally, we showcase the utility of our work by integrating the developed perceptual method in several geometric operations such as mesh simplification and adaptive subdivision

O Teste de software é uma atividade de garantia da qualidade que tem por finalidade diminuir o número de defeitos do software. Esta atividade contribui para redução do custo de manutenção e para a melhora da qualidade do software, durante o processo de desenvolvimento. Isso tem motivado a investigação e proposta de estratégias, técnicas, critérios e ferramentas de teste para diferentes paradigmas de desenvolvimento, tais como procedimental, orientado a objetos e orientado a aspectos. Vários estudos experimentais têm sido desenvolvidos para avaliar e comparar critérios de teste. Grande parte desses experimentos foram realizados com programas construídos sob um mesmo paradigma ou desconsiderando a influência do mesmo sobre os resultados. Entretanto, é importante avaliar o impacto de um paradigma específico sobre a atividade de teste uma vez que alguns defeitos podem estar relacionados ao seu uso. Este trabalho apresenta um estudo experimental realizado para caracterizar e avaliar o custo de aplicação e a dificuldade de satisfação de critérios de teste, comparando dois paradigmas: o orientado a objetos e o procedimental. O estudo considera critérios de teste funcionais e estruturais e utiliza um conjunto de programas do domínio de Estrutura de Dados. Os termos e fases do processo de experimentação controlada foram usados, à medida em que estes se mostraram adequados, para definir e executar o presente estudo. Os objetivos com a execução dessa pesquisa foram obter resultados iniciais sobre as questões investigadas bem como gerar artefatos que sirvam de base para a definição e condução de futuros experimentos e a criação de pacotes de laboratório. Além disso, pretende-se apoiar, por meio dos materiais gerados, o treinamento e o ensino da atividade do teste de software / Software Testing is a quality assurance activity that aims at reducing the number of software faults. This activity contributes for the reduction of maintenance costs and for software quality improvement during the development process. These factors have motivated the investigation and proposal of several testing strategies, techniques, criteria and tools for different programming paradigms, such as procedural, object-oriented and aspect-oriented. Regarding testing criteria, many experimental studies have been performed to evaluate and compare them. In general, these experiments comprise programs developed under the same paradigm or this influence over the results. However, some faults can be paradigm-related and it is important to evaluate its impact on the testing activity. This work presents an experimental study developed to characterize and evaluate the application cost and strength of testing criteria, comparing two programming paradigms: object-oriented and procedural. This study considers functional and strutural testing criteria and uses a set of programs from the data structure domain. Terms and phases from controlled experimentation process were used, as long as they showed to be adequated, to define and execute the present study. The research aims at obtaining initial results about the questions investigated as well as generating artifacts which support the definition and conduction of future experiments and the creation of laboratory packages. In addition, it intends to support, through the materials generated, the training and teaching of software testing activity

[pt] A tecnologia automotiva moderna alcança progressos consideráveis tanto no aspecto mecânico como funcional, com esses avanços tecnológicos, o maior progresso foi feito na estrutura dos automóveis e dos sistemas de ar condicionado. O presente trabalho é desenvolvido considerando a importância da utilização de gás refrigerante, já que se tornou um assunto ambiental de grande importância pelo fato de ter um papel na destruição da camada de ozônio. Foi construída uma bancada experimental que consta de duas câmaras isoladas para a colocação do equipamento, instrumentos, dispositivos de medição e geração de carga térmica, em seguida foi montado um condicionador de ar automotivo composto por componentes originais do sistema de condicionamento de ar de um automóvel para simular funcionamentos, com a finalidade de avaliar os parâmetros de funcionamento afetados quando são utilizadas diferentes cargas de gás refrigerante. Foram realizados testes controlando a temperatura e umidade constantes no habitáculo automotivo (câmara 1), para variações de temperatura na câmara (2), da vazão mássica no sistema e variações de torque e velocidade, no sistema motor - compressor, com diferentes quantidades de gás refrigerante originando situações de insuficiência de carga, carga adequada e sobre carga. Para o controle da carga térmica dentro das câmaras foram utilizados controladores de potência e um software aplicativo. Os parâmetros de operação do equipamento foram obtidos e arquivados mediante um sistema automático de aquisição de dados. Os resultados experimentais mostraram o comportamento real do ciclo de refrigeração, a queda de pressão nas linhas de descarga e de sucção, assim como no condensador e no evaporador. Apresenta-se o sub-resfriamento do refrigerante na saída do condensador bem como o superaquecimento na sucção. Verifica-se uma tendência politrópica, no lugar do processo isentrópico do ciclo ideal. Esta divergência do ciclo faz com que a temperatura de descarga do compressor (T2) seja elevada. A carga de gás refrigerante exerce influência no desempenho de um sistema de condicionamento de ar e os resultados do presente trabalho concordaram bem com as expectativas teóricas do problema considerado. / [en] The modern automotive technology reaches considerable progress s in the mechanical aspect as in the functional, with these technological advances, the biggest progress was made in the structure of the automobiles and in the air conditioning systems. Considering the importance of the use of refrigerant, the present work is developed, because the refrigerant gas became a great importance ambient subject for its paper in the ozone layer destruction. An experimental bench was constructed; it consists of two isolated chambers, where equipment, instruments, devices of measurement and thermal load generation were installed. After that, an automotive air conditioner was mounted, made up of original components from an automobile air conditioning system to simulate operation, with the purpose to evaluate the operation parameters affected when using different refrigerant loads. Tests with constant temperature and humidity in the simulated automotive chamber (1) for variations of chamber (2) temperature, of mass outflow in the system and variations of torque and speed in the motor-compressor system were performed with different refrigerating amounts creating situations of insufficient load, adequate load and over load. For the chambers thermal load controlling, power controlling and appropriate software were used. The equipment operational parameters had been gotten and filed by means of an automatic data acquisition system. The experimental results had shown the real behavior of the refrigeration cycle, the pressure drop in the discharge and suction lines, as well as in the condenser and the evaporator. Also the refrigerant sub-cooling in the exit of the condenser, the gas overheating in the suction, the polytrophic trend instead of the ideal cycle isentropic process was observed. This divergence from the ideal cycle makes the discharge compressor temperature (T2) was higher. The refrigerant gas charge influences the performance of an air conditioning system and the present work results agreed well with the theoretical expectations for the considered problem.

Over the last two centuries, there has been a continual evolution of how occupied rooms are heated, with inventors competing to design new heating devices. In particular, there is a wide range of convector types, which vary in shape, size, design, material, operating medium and application. With approximately 190 million convectors installed in the UK alone, the question arises regarding the dependencies on the efficiency of heat distribution through convector-induced filling flows. A standard approach to evaluate convector performance is based on the convector strength only, the implication being the stronger the convector the better the performance. This work has gone beyond the limits of a stereotypical assessment in pursuit of answers regarding the physics of convector-induced filling and a new objective method to evaluate the efficiency of this transient process. The ultimate goal has been to provide a deep understanding of filling and stratification induced by a convector, in order to heat rooms rapidly and effectively. An experimental facility has been designed that approximates dynamic similarity between the experimental set-up and a real-life room with a convector. In the experiments, a rectangular sectioned water tank represents a room and a saline source rectangular sectioned panel with sintered side walls provides a convector representation. Experiments have been performed in water with a saline solution to ensure high Rayleigh numbers. Diagnostic techniques involve a combination of a shadowgraph method, a dye-attenuation method, direct salinity measurements and a new application of Particle Image Velocimetry (PIV). Interesting insight into convector-induced buoyancy-driven flows has been gained. As a result, new guidelines aimed at heating rooms more rapidly and effectively have been proposed. The key outcome that can be immediately applied is that, for a given convector strength, heat distribution with height can be improved by adjusting the convector position. For instance, faster filling leading to more uniform heat distribution occurs in rooms with convectors detached from side walls, due to large-scale mixing flows in the early period of filling. Also shorter convectors relative to the room height, positioned close to the floor level, promote faster and more uniform filling. An attempt to describe the transient filling has been made and to do so statistical methods, application specific, have been developed. As a result, the empirical equations describing both the filling rates in different stages of filling and the development of stratification have been derived, which rank the governing parameters, based on their importance, as either dominant or subordinate. Two dominant parameters governing filling flows are the non-dimensional accumulation parameter B and the Rayleigh number ΔRa, which are related to the convector strength. The impact of these two parameters is constant throughout the process. The parameters accounting for the system geometry and filling time (T) are subordinate parameters. Their impact, visible in the early period, decreases as filling continues.

Avec l’avènement des véhicules hybrides rechargeables, voire tout électrique et la nécessité d’une augmentation de l’autonomie et de l’énergie volumique des batteries de traction, leur refroidissement au cours du roulage devient nécessaire pour garantir leur fiabilité et leur durabilité. Pour ces véhicules, le système de production de froid peut avoir à alimenter deux évaporateurs pour la climatisation de l’habitacle (Climatisation au rang 1 et rang 2) ainsi qu’un refroidisseur de liquide pour le refroidissement de la batterie de traction. Ce type de système de réfrigération multi-évaporateur présente un certain nombre de verrous technologiques qu’il convient de lever liés au dimensionnement des éléments dans un contexte de réduction de la charge en fluide frigorigène et au contrôle - commande de tels systèmes. Dans les systèmes de climatisation multi-évaporateurs, la pression d’évaporation est sensiblement égale dans chaque évaporateur de telle manière que leur fonctionnement est couplé dynamiquement. Cependant, la demande en puissance frigorifique et les consignes de température de l’air soufflée et de l’eau peuvent varier d’un évaporateur à l’autre. Le détendeur devient alors un composant clé et son fonctionnement doit être étudié. Pour ces raisons, un banc d’essais expérimental a été créé pour étudier ce type de climatisation multi-évaporateurs en régime stabilisé et en régime transitoire. Des détendeurs thermostatique et électronique ont été montés en parallèle sur chaque évaporateur afin de pouvoir étudier leur impact sur le système. Une fois les différents bilans réalisés, les résultats expérimentaux sont exploités pour caractériser l’ensemble des composants avec le nouveau fluide frigorigène R-1234yf. Les phénomènes de mauvaise distribution du fluide frigorigène dans l’évaporateur ainsi que de l’évaporateur endormi sont également étudiés. Dans un second temps, à partir des résultats expérimentaux, un modèle numérique et dynamique du climatiseur a été réalisé avec le logiciel LMS Imagine Lab Amesim® 1D. Après avoir validé indépendamment chacun des composants, le système est validé sur une série de points de fonctionnement en régime stationnaire. Le modèle est ensuite exploité afin d’étudier diverses lois de contrôle permettant l’optimisation du fonctionnement. / With the arrival of plug-in hybrid and fully electrified vehicles, the air-conditioning system has to be reconsidered. Battery cooling management system and high level of comfort for passengers make the single evaporator air-conditioning system a multi-evaporator one. In a multi-evaporator air-conditioning system, evaporating pressures are equal in each evaporator so that evaporators are coupled dynamically. However, the demand in cooling capacity and temperature target can vary from each other. For an operating point with a first evaporator working at high load and a second at low partial load, thermal interaction can occur from the superheated refrigerant coming from a first evaporator to the outlet of a second evaporator. This phenomenon makes the second evaporator sleeping since its expansion valve bulb misreads the superheat and closes. Furthermore, sleeping evaporator looks like an extreme case of refrigerant maldistribution in the evaporator. Refrigerant maldistribution is then investigated to show some drawbacks and advantages multi-evaporator air-conditioning systems (MEAC) have to face or can benefit by comparing two types of expansion valve: thermostatic and electronic ones. In this paper, sleeping evaporator and refrigerant maldistribution phenomena are experimentally investigated in order to propose in the future a robust control of an automotive MEAC. A test bench was built to compare two types of expansion valves (thermostatic/electronic) and study their behaviours in steady and transient state to tackle sleeping evaporators and benefit from refrigerant maldistribution. An automotive multi-evaporator air conditioning system, which is composed of two evaporators and a secondary fluid cooler, was modeled using the LMS Imagine.Lab Amesim® 1D software. The present study focuses on understanding the dynamic coupling of the several loop components such as the three evaporators having different cooling capacities. This kind of multi-evaporator air-conditioning system has a number of technological barriers that must be overcome. Understanding the behavior of their respective expansion devices and the choice of these latter is also essential to control properly the transient phase and ensure an optimal operation of the air-conditioning system. In order to study the behavior of the loop, step disturbances were simulated on an operating point at medium and high load. The impact of these disturbances on the stability of the supplied cooled air temperature is analyzed for two types of expansion valve. Initial results show that the thermostatic expansion valves can cause instabilities. Furthermore, the electronic expansion valves have to be regulated with an advanced control in order to use their full potential and to try to achieve desired results.