Phase change materials characterisation and applications to the thermal simulation of buildings

This study aims at presenting the main results of the Stock-E MICMCP project, fund by the French National Research Agency (ANR). The principal goal of this project is the correct characterisation of the thermophysical properties of phase change materials (PCMs) in order to have reliable inputs when considering their use in numerical simulations of thermal behaviour of buildings. Firstly, the method developed to determine the dependency of the enthalpy function with respect to the temperature of the material is presented. It is based on the use of experimental measurements together with an inverse method combined with a numerical modelling. By assuming an a priori formulation of the enthalpy, based on some basic thermodynamic constraints, a simulated heat flux may be computed. It is then compared to the measured one, which permits to define an objective function. Its minimization thus allow to determine the value of the parameters involved in the equation of state. This step is first tested with microscopic samples thanks to differential scanning calorimetry (DSC). Secondly, it will be shown that this method can be extended to macroscopic and heterogeneous materials, which are more representative of real samples. Eventually, some examples of thermal simulations of buildings are done so as to highlight the necessity to correctly represent the PCM behaviour. This is particularly important since they appeared to be a promising way to save energy and achieve a better comfort in buildings, therefore an incorrect determination of their properties may lead to wrong conclusions on their real benefits.