Test of Two Phase Change Materials for Thermal Energy Storage: Determination of the Global Heat Transfer Coefficient

Laboratory scale experiments on the behaviour of two phase change materials, a salt and a paraffin, during fusion and solidification cycling processes, were accomplished. To do this, a system using thermal oil as the heat transfer carrier was used and the phase change material being tested operated in a fusion and solidification cycle. The heat transfer oil transferred heat to the phase change material during the fusion step and carried heat away from the change phase material during the solidification step. The influence of the mass flow rate of the heat transfer fluid, as well as of its temperature, in the response of the phase change material, was studied. Axial and radial temperature profiles inside the phase change materials were obtained during the experiments and subsequently analysed. From these temperature profiles and through an adequate mathematical treatment, global heat transfer coefficients between the heat transfer oil and the phase change material were determined, as well as average heat transfer coefficients for the phase change materials.