Performance improvement of metal hydride hydrogen storage tanks by using phase change materials

Abstract

In metal hydride based hydrogen storage tanks, heat transfer fluid (HTF) has been extensively used to continuously transfer the reaction heat for promoting the reaction via heat exchangers. In this study, the phase change material (PCM) is integrated with the tank to enhance heat transfer and recycle the reaction heat. A novel storage tank with a simple concentric straight-tube heat exchanger surrounded by PCM is put forward to improve the hydrogen storage performance. A numerical model is built to track the transfer and reaction process. By comparison, the new tank shows better heat transfer and storage performance, and the hydrogen absorption time is shortened by 60.2% than that of the tank without PCM. For the new tank, the optimal amount of PCM is obtained, based on which the increased absorption pressure could effectively accelerate the heat discharge and reaction rate during the absorption process. However, the increased inlet velocity of HTF has a limited improvement effect on heat transfer and reaction performance. Furthermore, on the PCM side of the tank, the addition of fins and increasing the thermal conductivity of PCM had little effect on the performance of the tank.