Cyclic performance analysis of a high temperature flat plate thermal energy storage unit with phase change material

Abstract

The cyclic performance of a high temperature flat plate thermal energy storage (FPTES) with phase change material (PCM) is numerically studied. Based on a one-dimensional model, both the thermal conduction and phase change within the PCM plate in the direction normal to the flow direction of heat transfer fluid (HTF) are taken into consideration in the this study. The proposed model is validated against the reported results and the numerical results calculated by a commercial CFD software. Then, the proposed model is used to simulate the cyclic charging and discharging processes of the FPTES with PCM. In addition, the influence of the cut-off values, HTF mass flow rate, and flat plate length and thickness on the charging efficiency and capacity ratio are investigated. The results show that the charging and discharging processes reach a repeatable state after several cycles, and the repeatable cycle is very different from the first cycle. The capacity ratio and the charging/discharging time increase with the cut-off values. An optimum charging cut-off value exists to achieve the highest charging efficiency. Extending the flat plate length helps to increase the capacity ratio and charging efficiency. Besides, the decreases in HTF mass flow rate and plate thickness can increase the charging efficiency and capacity ratio. Finally, a system design guideline of the FPTES with PCM is proposed based on the developed model and the gained results.