Compact infrared cryogenic wafer-level camera: design and experimental validation

International audienceWe present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120 degrees. By merging the optics with the detector, the concept is compatible with both cryogenic constraints and wafer-level fabrication. The design strategy of such a camera is described, as well as its fabrication and integration process. Its characterization has been carried out in terms of the modulation transfer function and the noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images. (C) 2012 Optical Society of Americ

Experimental results of an organic rankine cycle (ORC) associated to a passive heat removal system for advanced pressurized water reactors (PWR)

International audienceThis work concerns a specific passive system design for advanced pressurized water reactor (PWR). The studied system first relies on passive safety condensers, which are increasingly being used in the design of new generation nuclear power plants (NPP). These condensers are typically immersed in large water tanks that function as a cold source or heat sink. They have to be situated in a sufficient elevation enabling a two-phase natural circulation mode, with both a condensing phase of the steam extracted from the steam generator, and a gravity draining return for the condensates to the steam generator. Such power extraction can be used for a relatively long period of time depending on the pool size.The present research is based on the use of a portion of the energy stored in this boiling water volume as a hot source for a thermodynamic cycle via an immersed heat exchanger. The power generated by this cycle will be used as an autonomous supply for various critical components, in addition to existing systems. This technology used here which can convert electricity from low-grade heat is similar with existing technologies already used for the valorization of renewable (biomass, solar, geothermal) or industrial waste heat at low and medium temperature (<150°C) into electricity.An efficient technology is the organic Rankine cycle (ORC), which has been used at laboratory and industrial scales for about several decades. However, two major issues hamper the use of ORC in the context of PWR: the nature of the hot source (water at 100°C) and the requirement for system reliability and robustness. Aside from these two challenges, there are the usual constraints associated with this type of cycle: maximizing energy performance, using an environmentally friendly fluid, and minimizing space requirements.An experimental test bench with a boiling water pool and an ORC with immersed evaporator was built to address this problem. The design of the immersed evaporator is explained, as well as the correlations used. The system reliability is then studied through the investigation of off-nominal situations (degraded heat transfer at ORC evaporator, ''high'' temperature of ORC condenser) for a first approach of reliability assessment. This study gives first elements for the demonstration of the adaptability of a partial admission axial micro-turbine to the variation of cold source temperature and to the entry of two-phase fluid in Novec649TM. All the experimental results will be used to validate the theoretical model of the ORC (condenser - evaporator - turbine) in order to design the ORC at scale 1

Experimental results of an organic rankine cycle (ORC) associated to a passive heat removal system for advanced pressurized water reactors (PWR)

International audienceThis work concerns a specific passive system design for advanced pressurized water reactor (PWR). The studied system first relies on passive safety condensers, which are increasingly being used in the design of new generation nuclear power plants (NPP). These condensers are typically immersed in large water tanks that function as a cold source or heat sink. They have to be situated in a sufficient elevation enabling a two-phase natural circulation mode, with both a condensing phase of the steam extracted from the steam generator, and a gravity draining return for the condensates to the steam generator. Such power extraction can be used for a relatively long period of time depending on the pool size.The present research is based on the use of a portion of the energy stored in this boiling water volume as a hot source for a thermodynamic cycle via an immersed heat exchanger. The power generated by this cycle will be used as an autonomous supply for various critical components, in addition to existing systems. This technology used here which can convert electricity from low-grade heat is similar with existing technologies already used for the valorization of renewable (biomass, solar, geothermal) or industrial waste heat at low and medium temperature (<150°C) into electricity.An efficient technology is the organic Rankine cycle (ORC), which has been used at laboratory and industrial scales for about several decades. However, two major issues hamper the use of ORC in the context of PWR: the nature of the hot source (water at 100°C) and the requirement for system reliability and robustness. Aside from these two challenges, there are the usual constraints associated with this type of cycle: maximizing energy performance, using an environmentally friendly fluid, and minimizing space requirements.An experimental test bench with a boiling water pool and an ORC with immersed evaporator was built to address this problem. The design of the immersed evaporator is explained, as well as the correlations used. The system reliability is then studied through the investigation of off-nominal situations (degraded heat transfer at ORC evaporator, ''high'' temperature of ORC condenser) for a first approach of reliability assessment. This study gives first elements for the demonstration of the adaptability of a partial admission axial micro-turbine to the variation of cold source temperature and to the entry of two-phase fluid in Novec649TM. All the experimental results will be used to validate the theoretical model of the ORC (condenser - evaporator - turbine) in order to design the ORC at scale 1

A Recent Advance on Partial Evaporating Organic Rankine Cycle: Experimental Results on an Axial Turbine

The organic Rankine cycle (ORC) technology is an efficient way to convert low-grade heat from renewable sources or waste heat for power generation. The partial evaporating organic Rankine cycle (PEORC) can be considered as a promising alternative as it can offer a higher utilization of the heat source. An experimental investigation of a small ORC system used in full or partial evaporation mode is performed. First characterized in superheated mode, which corresponds to standard ORC behavior, a semi-empirical correlative approach involving traditional non-dimensional turbomachinery parameters (specific speed, pressure ratio) can accurately describe one-phase turbine performance. In a second step, two-phase behavior is experimentally investigated. The efficiency loss caused by the two-phase inlet condition is quantified and considered acceptable. The turbine two-phase operation allows for an increase in the amount of recovered heat source. The ability to operate in two phases provides a new degree of flexibility when designing a PEORC. The semi-empirical correlative approach is then completed to take into account the partially evaporated turbine inlet condition. The qualitative description and the quantitative correlations in the one-phase and two-phase modes were applied to different pure working fluids (Novec649TM, HFE7000 and HFE7100) as well as to a zeotropic mixture (Novec649TM/HFE7000)

A Recent Advance on Partial Evaporating Organic Rankine Cycle: Experimental Results on an Axial Turbine

The organic Rankine cycle (ORC) technology is an efficient way to convert low-grade heat from renewable sources or waste heat for power generation. The partial evaporating organic Rankine cycle (PEORC) can be considered as a promising alternative as it can offer a higher utilization of the heat source. An experimental investigation of a small ORC system used in full or partial evaporation mode is performed. First characterized in superheated mode, which corresponds to standard ORC behavior, a semi-empirical correlative approach involving traditional non-dimensional turbomachinery parameters (specific speed, pressure ratio) can accurately describe one-phase turbine performance. In a second step, two-phase behavior is experimentally investigated. The efficiency loss caused by the two-phase inlet condition is quantified and considered acceptable. The turbine two-phase operation allows for an increase in the amount of recovered heat source. The ability to operate in two phases provides a new degree of flexibility when designing a PEORC. The semi-empirical correlative approach is then completed to take into account the partially evaporated turbine inlet condition. The qualitative description and the quantitative correlations in the one-phase and two-phase modes were applied to different pure working fluids (Novec649TM, HFE7000 and HFE7100) as well as to a zeotropic mixture (Novec649TM/HFE7000)

Études de santé

La crise du Covid-19 a exacerbé et mis au grand jour les difficultés du système de santé français, notamment sur le volet de la gestion des ressources humaines : pénuries de personnel, épuisement professionnel, rémunérations insuffisantes… Beaucoup de territoires connaissaient déjà ces maux : les déserts médicaux ne datent pas d’hier, pas plus que les problèmes de coordination des soins pour la prise en charge des maladies chroniques ou les lacunes en termes d’accompagnement au grand âge. Tous ces problèmes ne viennent pas de la formation et tous ne trouvent pas leur solution dans les réformes conduites dans ce domaine, mais la façon dont l’appareil de formation délivre les connaissances et fabrique les spécialités, son organisation (entre les universités, les CHU, les facultés, les instituts… et les territoires), les politiques en matière d’admission et de flux d’étudiants (les fameux numerus clausus et quotas), tout cela façonne le système de santé, influe sur les possibilités de coopération et les conflits et modèle le rapport à l’innovation et la distribution des ressources sur le terrain. Si la santé est un bien commun, la réforme des études est l’affaire de tous. Ce livre, qui donne la parole aux acteurs (enseignants, professionnels de santé, chercheurs, étudiants et acteurs des politiques), place les réformes actuelles des études de santé à la portée du plus grand nombre