Study on basic properties of phase change material for thermal energy storage

Abstract

Freezing and melting characteristics of ice ball for thermal energy storage (TES) system are analyzed and important factors such as behavior of temperature inside sphere encapsulated ice is identified. An ice ball model was developed considering the heat transfer fluid (HTF) that flow through the ice ball that contained phase change material (PCM). The model was simplified and the numerical simulations were validated by comparison with experimental results from previous study. The study shows that the rate of complete freezing of the ice ball is roughly three times the rate of diameter increment. The 9.6% increment of ice ball diameter will result in the increasing of 16.7% the time for center of ice ball to reach the 293K temperatures in melting process. The study also shows that it is critical to control the flows of heat transfer fluid inside tank storage. The formation of ice was estimated based on the volume of ice formed at certain increment of time. The formation of ice for 94mm ice ball is 4% more than 103mm ice ball. Thermal energy storage (TES) is one of the popular alternatives nowadays to replace the traditional method in air-conditioning system. The heart of the ice storage lies in the performance of the ice ball in the storage tank. In this study, the geometrical effect of the ice ball is investigated. Several ice balls with different size were studied in lab-scale rig for their freezing behavior. The study shows that there exists an optimum ball size to achieve effective freezing process.