Thermal and flow behaviors in heat transportation container using phase change material

Abstract

A waste heat transportation system using a phase change material (PCM) – the so-called trans-heat (TH) system that uses a direct heat exchanger with an extremely simple structure to store and release the latent heat of PCMs – is quite attractive. The purpose of this paper is to study the thermal and flow behaviors in a TH container in which the solidification and melting of PCMs are directly observed by using a two-dimensional, roundly sliced model. In the heat storage experiments, we observed many HTO channels within the solid PCM in the early stage, which caused a large heat storage rate. In the final stage, the heat storage rate was extremely small; leading to the formation of a dead zone for the solid PCM in the lower part of both ends of the container owing to the non-uniform distribution of the HTO. In the heat release experiments, interestingly, the observed features of the solid PCMs were classified into three types; formation and growth of solidified PCM masses in the inlet pipes, sinking of solidified PCM particles and foaming oil coated by solidified PCM film. In particular, the sinking of the solidified PCM particles was effective for mixing the liquid PCM and cooling the container uniformly. The results revealed that the shape of the inlet pipes should be designed by considering their position, the number of pipes and the nozzle angle using a sophisticated heat and fluid flow model to maximize the heat exchange rate.