Étude expérimentale et numérique des phénomènes thermomécaniques lors de la congélation de produits alimentaires. Application à des structures multicouches.

This PhD concerns the characterization of the thermal and mechanical properties for a model food : Tylose and a real food: chocolate; and a numercial simulation of the thermal and mechanical phenomena during freezing. The experimental study (static and dynamic tests) showed the influence of the ice's formation on the mechanical properties during freezing. The numerical study (finite element) was done for three cases: a layer of Tylose in Cartesian coordinates and two two-layers in Cartesian and cylindrical coordinates. Simulations show a stress, during freezing, in compression at the crystallization temperature and in tension after 90% ice formed. This complex stress can produce fractures. Futhermore, the global displacement of the sample during freezing is a new parameter for the optimization and the control of the process. Strong stresses at the interfaces can be also produce cracks at the surface of the product.Cette thèse s'articule autour de la caractérisation des propriétés thermophysiques et mécaniques d'un produit modèle : la Tylose et d'un produit alimentaire: le chocolat, ainsi qu'une modélisation du couplage thermique-mécanique en cours de congélation. L'étude expérimentale (en statique et en dynamique) a mis en évidence l'influence de la formation de glace sur la variation des propriétés mécaniques en fonction de la température. L'étude numérique a été réalisée sur une géométrie simple (plaque de Tylose) et sur deux géométries bicouches (plaque et cylindre), en éléments finis. Les simulations ont mis en évidence une contrainte parallèle au flux thermique qui engendre au sein de la structure une compression (proche de la température de cristallisation) suivi d'une tension (après l'apparition de 90% de glace). Cette contrainte complexe pourra engendrer l'apparition de fissures au sein du produit. De plus, le champ de déformation globale peut être utilisé comme un nouveau paramètre de contrôle et d'optimisation de la congélation. La présence de fortes contraintes aux interfaces peut également engendrer la création de fissures

Influences of confinement on subatmospheric water vaporization phenomena in a vertical rectangular channel

International audienc

Implementation of Adapted Black Box Models for the Performance Characterization of Commercial Sorption Chillers

International audienc

Life cycle analysis of 4.5Â MW and 250Â W wind turbines

Electric generation by wind turbine is growing very strongly. However, the environmental impact of wind energy is still a matter of controversy. This paper uses Life Cycle Assessment, comparing two systems: a 4.5 MW and a 250 W wind turbines, to evaluate their environmental impact. All stages of life cycle (manufacturing, transports, installation, maintenance, disassembly and disposal) have been analysed and sensitivity tests have been performed. According to the indexes (PEPBT (primary energy pay back time), CO2 emissions, etc.), the results show that wind energy is an excellent environmental solution provided first, the turbines are high efficiency ones and implemented on sites where the wind resource is good, second, components transportation should not spend too much energy and, third, recycling during decommissioning should be performed correctly. This study proves that wind energy should become one of the best ways to mitigate climate change and to provide electricity in rural zones not connected to the grid.Life cycle assessment (LCA) Wind turbine Pay back time

Pompe à chaleur : technologies et applications dans le résidentiel

La pompe à chaleur nécessite une bonne compréhension des composants technologiques ainsi que du besoin à satisfaire afin d’être correctement dimensionnée et ainsi optimiser sa consommation énergétique. Cet article traite du secteur résidentiel (le chauffage et/ou l’eau chaude sanitaire). Après une présentation du principe de fonctionnement, les composants technologiques sont décrits. Le dimensionnement de la pompe à chaleur est ensuite présenté en prenant en compte ou non la présence d’un appoint énergétique. Enfin, des règles d’installation sont proposées en mettant en avant les avantages et contraintes des solutions existantes

Experimental study of water vaporization occurring inside the channel of a smooth-plate type heat exchanger connected to an adsorber and comparison with trends observed in absorption configuration

International audienc

Etude des mécanismes de vaporisation de l’eau à basse pression : application à un échangeur à plaques au cours d’un cycle d’adsorption. Congès Société Française de Thermique.

National audienc

Development of an object-oriented model for chilled-water thermal energy storage applications

International audienc

A modeling and simulation approach for thermal energy storage devices.

International audienceThe energy efficiency simulation of building systems requires an accurate modelling of their individual components as well as a reliable representation of the dynamic interaction between them. We present in this paper, a modelling approach for an energy storage device, following an object-oriented paradigm based on the MODELICA modelling language. The model predicts 3D fluid motion in a thermally isolated cylindrical tank as well as the temperature profile variation, of the fluid within, in respond to variable tank volume, inlet and outlet conditions. The model integration in multi-component systems is straightforward via the simulation environment OpenModelica and does not require co-simulation as it was the practice in multi-domain simulations. A simulation test of the model shows its ability to achieve reliable results in a compromise manner between computationally light 1D models and computationally heavy CFD models. It also shows that in charging a 300L storage tank with cold water, a temperature uniformity in water layers inside the tank could not be achieved before 3h which is equivalent to half of the charging cycle period. This shows that the horizontal isothermal layer division used in the traditional 1D models, shall no longer be suitable for the future energy efficiency simulations of larger more complex multi-components systems integrating storage devices as the charge/discharge cycles becomes shorter and more interactive. Hence, a modelling and simulation approach such as the one described in this paper will be useful for the future energy efficiency studies related to thermal storage systems. 1. Context In recent years, policies to promote improved energy efficiency have been established in response to European and International regulatory obligations. Thermal energy storage has proven to be a technology that can have positive effects on the energy efficiency of a building by contributing to an increased share of renewable energy and/or reduction in energy demand or peak loads for both heating and cooling [1]. For example, the integration of a thermal energy storage device in an air conditioning application can shift the power consumption from peak periods to off-peak periods which contributes significantly in reducing the energy consumption and increasing the overall efficiency of the chilled water plant. However, such component integration have created additional challenges to design and manage the resulting more complex system, where the storage device dynamic behavior plays a significant role between the energy supply and energy demand loops. To approach these challenges, an accurate modelling of the storage component dynamic behavior is required from one hand and from the other an easy and effective way to couple it with other components and simulate their interaction simultaneously is needed in order to evaluate the energy efficiency of the resulting multi-component system. Achieving these two requirements, simultaneously, was difficult to accomplish in traditional modelling and simulation practices. From one side, 3D-CFD (Computational Fluid Dynamics) tools are used for accurate modelling of the storage devices but the resulting models require large computational resources and computing time and are limited in terms of coupling with models from different simulation domains. From the opposite side, 1D-DAE (Differential Algebraic Equation) tools use simplified 1D models o