A Simple Experimental Method for Thermal Characterization of Shape-Stabilized Phase Change Materials

A new method for characterization of shape-stabilized phase change materials (PCMs) based on one single sample and one single experimental device has been proposed. The simplicity of the experimental device is comparable to that of the T-history method: a cylinder of PCM, which is heated/cooled in a furnace following specific temperature patterns (steps, isotherms, and ramps). Instead of simple energy balances as in the T-history method, a numerical heat transfer model is used to retrieve the whole set of parameters/functions characterizing the PCM from temperature measurements at one single point within the PCM. A powerful inversion technique has been proposed for that. Its most striking feature is that it allows identification of enthalpy-temperature functions in an easy way. They are retrieved by solving a problem of time-dependent source estimation by inversion of a linear heat conduction model. It is shown that unknown sources are the output of a linear and invariant state model whose inputs are measured temperatures within the PCM. Enthalpy-temperature functions, as well as parameters derived from heat capacities, transition temperatures, and latent heat, are thus calculated in a simple way. An experimental test for characterization of graphite/salt composites has been carried out to illustrate the appropriateness of our developments.