Modeling of subcooling and solidification of phase change materials

Phase change materials (PCM) are able to store thermal energy in small temperature intervals very efficiently due to their high latent heat. Particularly high storage capacity is found in salt hydrates. Salt hydrates however often show subcooling, thus inhibiting the release of the stored heat. In the state of the art simulations of PCM, the effect of subcooling is almost always neglected. This is a practicable approach for small subcooling, but it is problematic for subcooling in the order of the driving temperature gradient on unloading the storage. In this paper, we first present a new algorithm to simulate subcooling in a physically proper way. Then, we present a parametric study to demonstrate the main features of the algorithm and a comparison of computed and experimentally obtained data. The new algorithm should be particularly useful in simulating applications with low cooling rates, for example building applications.