Inverse method for the identification of the enthalpy of phase change materials from calorimetry experiments

Thermal energy storage is now a key parameter to overcome :he delay between energy supply and demand in many applications. To address this issue, the use of phase change materials (PCM) tends to be more and more common. Given the attempted objectives of such applications, performances of the PCM are a cornerstone of the whole system. Therefore, a correct determination of their intrinsic properties is crucial. To perform this step, one may use a calorimetry experiment. Unfortunately, the interpretation of the thermogram is not straightforward and consequently, when not feasible at all, estimations may be wrong. As an example, pure substance as sometimes said to melt at a non-uniform temperature (their enthalpy being smeared over several degrees), and binary solutions are associated with liquidus temperature and latent heat that do not match the correct form of their enthalpy. The present work proposes a new method to avoid such issues. To summarize the novelty of our approach, the main idea is to use an inverse method to identify the thermodynamical parameters of the sample through a matching step between the experimental curves and theoretical ones. It means that contrary to many others methods, we do not directly extrapolate the thermodynamical properties (e.g. the enthalpy) from the thermogram. Instead, we suppose an a priori formulation of the enthalpy, based on thermodynamical principles. Thus the thermodynamical parameters are inputs of which only values are computed from the experiments. Capabilities of the method are shown on pure substances and binary solutions examples. (C) 2012 Elsevier B.V. All rights reserved.