Cyclic heat transfer in a novel storage unit of multiple phase change materials

Abstract

A novel storage unit of multiple phase change materials (PCMs) is developed. The physical module consists of a tube which is surrounded by an external coaxial cylinder made up of several segments of different PCMs with different melting points. A heat transfer fluid flows through the tube to store-extract thermal energy from the PCMs. A finite element model has been developed to simulate the cyclic thermal process involved as a result of alternating melting and freezing processes. Computations have been carried out for the case of high-temperature thermal storage to investigate the advantages of using multiple PCMs over a single PCM in the module. Numerical results indicate that the heat transfer rates can be greatly enhanced using multiple PCMs as compared with a single PCM. The enhancement of the heat transfer rate is of practical significance to improve the performance of latent thermal storage exchangers.