Numerical study of heat transfer in macro-encapsulated phase change material for thermal energy storage

The successful development and implementation of systems using renewable energy sources, which are usually of intermittent character, require cheap and effective thermal energy storing for diurnal or seasonal heat accumulation. Thermal accumulators are also used for increasing the efficiency of conventional fuel dependent systems by storing the waste heat in low consumption periods. Much of the efforts are directed towards creation of compact solutions to replace the presently used hot water tanks requiring very large space. This is especially important for small capacity thermal systems in buildings. There are a lot of suggestions in literature using the latent heat of phase change materials (PCM), but only a few close to commercial stage of implementation. A heat accumulator with paraffin as a PCM is a cost effective innovative solution for low grade heat storage. One of the design approaches is encapsulation of the phase change material in containers with a variety of shapes and materials. The aim of the present work is a 3D numerical simulation of the phase change process in a stainless- steel container filled with commercial E53 paraffin. This is a part of a study directed towards design optimization of a hybrid solar installation with thermal storage. The focus is on development and testing of a time effective method for numerical prediction of the thermal behaviour of the container with paraffin and assessment of the factors influencing the heat transfer process prior to the physical experiment.