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Dujardin N.,CNRS Research Center for Thermal Systems and Energy
Journal of Physical Chemistry B | Year: 2011

It has been recently shown that mechanical milling can amorphize d-glucose without any mutarotation, giving rise to an anomerically pure amorphous sample. We have taken advantage of this exceptional possibility to study the kinetic of mutarotation in the amorphous solid state. The investigations have been performed in situ by time-resolved Raman spectroscopy. The results reveal an unexpected coupling between the mutarotation process and the structural relaxations involved in the glassy state. © 2011 American Chemical Society. Source

Ramdani N.,French Institute for Research in Computer Science and Automation | Ramdani N.,CNRS Montpellier Laboratory of Informatics, Robotics and Microelectronics | Meslem N.,French National Institute for Agricultural Research | Candau Y.,CNRS Research Center for Thermal Systems and Energy
Nonlinear Analysis: Hybrid Systems | Year: 2010

We address nonlinear reachability computation for uncertain monotone systems, those for which flows preserve a suitable partial orderings on initial conditions. In a previous work Ramdani (2008) [22], we introduced a nonlinear hybridization approach to nonlinear continuous reachability computation. By analysing the signs of off-diagonal elements of system's Jacobian matrix, a hybrid automaton can be obtained, which yields component-wise bounds for the reachable sets. One shortcoming of the method is induced by the need to use whole sets for addressing mode switching. In this paper, we improve this method and show that for the broad class of monotone dynamical systems, component-wise bounds can be obtained for the reachable set in a separate manner. As a consequence, mode switching no longer needs to use whole solution sets. We give examples which show the potentials of the new approach. © 2009 Elsevier Ltd. All rights reserved. Source

Lanini S.,Bureau de Recherches Geologiques et Minieres | Delaleux F.,CNRS Research Center for Thermal Systems and Energy | Py X.,University of Perpignan | Olives R.,University of Perpignan | Nguyen D.,Bureau de Recherches Geologiques et Minieres
Energy and Buildings | Year: 2014

Underground Thermal Energy Storage appears to be an attractive solution for solar thermal energy storage. The SOLARGEOTHERM research project aimed to evaluate the energetic potential of borehole thermal energy storage by means of a full-scale experimental device and heat transfer models. Analysis of the experimental data showed that a single borehole is not efficient for storage. Application of a 1D analytical model showed that the heat transfer fluid in the geothermal probe lost 15% of its energy at a depth of 100 m and 25% at 150 m. A 3D multilayer numerical model was then developed and validated against the experimental data. This model was then used to simulate different configurations over many years. Lastly, a theoretical approach to optimising design of a borehole thermal energy store (BTES) was proposed. A relation was established that enables comparison of the storage characteristic time of any vertical BTES to an optimum one. Based on these experimental, modelling and theoretical results, guidelines are formulated to optimise the design of vertical borehole fields with an objective of inter-seasonal heat storage. In particular, borehole fields should define cylindrical storage volumes with diameters twice their height, and depth should not exceed 100 m. © 2014 Elsevier B.V. Source

Mazioud A.,CNRS Research Center for Thermal Systems and Energy | Durastanti J.F.,CNRS Research Center for Thermal Systems and Energy
Comptes Rendus - Mecanique | Year: 2010

This Note presents the study of transient flow under forced convection in buried co-axial exchanger. The wall temperature as well as the wall heat flux and the heat transfer coefficient are unknown. A hybrid model consisting of a finite element method at the boundary (BEM) for the heat transfer problem on the boundary and a finite volume method (FVM) to solve the laminar flow inside solves this problem. The development of the BEM method is based on the Green's function theory. This conjugate method allows one to have fast results and to foresee the thermal behaviour of the exchanger. The heat transfer coefficients are investigated. The results are compared to those obtained using the commercial CFD package Fluent. © 2010 Académie des sciences. Source

Cabeza L.F.,University of Lleida | Barreneche C.,University of Lleida | Barreneche C.,University of Barcelona | Martorell I.,University of Lleida | And 17 more authors.
Renewable and Sustainable Energy Reviews | Year: 2015

The use of thermal energy storage by phase change materials (PCM) is increasing in interest for building applications. For the deployment of the technology, appropriate characterization of PCM and hybrid PCM is essential, but it is not always possible to carry it out with conventional equipment, mainly due to the sample size. This paper shows equipment developed in different research centers and universities to analyze thermophysical properties, such as specific heat, latent heat and melting temperature, and thermal conductivity and diffusivity of PCM and hybrid PCM materials. © 2014 Elsevier Ltd. Source

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