Studies on performance enhancement of heat storage system with multiple phase change materials

Abstract

This paper aims to improve the heat storage system's performance by using multiple phase change materials (PCMs). A heat storage device is designed with multiple PCMs firstly. The heat storage device consists of three identical shell-tube phase change thermal storage units. The numerical method is developed and verified experimentally. Two parameters, namely the latent heat utilization of PCM (ω) and the heat transfer effectiveness of heat storage device (ε), are introduced to evaluate the performance of energy storage and the heat exchange of the heat storage system with multiple PCMs. The effects of factors on ω and ε are studied, including the thermal conductivity, latent heat and melting temperature difference of PCMs, and the inlet velocity and temperature of heat transfer fluid. Results indicate that increasing the inlet velocity and temperature of HTF can greatly improve ω, but reduce ε. Increasing the thermal conductivity of PCM can obviously improve ω, but it has little effect on improving ε. Multiple PCMs with suitable melting temperature difference can improve both ω and ε. In practice, multiple PCMs can be associated with the above methods to improve the overall performance of the phase change thermal storage system. This research is used to optimize the design of phase change thermal storage device and improve its performance.