Numerical thermal performance analysis of a PCM-to-air and liquid heat exchanger implementing latent heat thermal energy storage

Abstract

Due to the mismatches in energy supply and demand in thermal systems, employing latent heat thermal energy storage using phase change materials (PCMs) is a reliable and effective solution. In this regard, this paper introduces an innovative PCM-to-air and liquid heat exchanger to increase thermal system performance by providing a hybrid heat source to the airside. A novel numerical work based on multiphysics coupling of heat transfer and double fluid flow and phase change within a complex geometry is represented. Numerical heat transfer analysis is performed on the model based on three-dimensional computational fluid dynamics simulation. In order to make a thorough thermal performance assessment, the dynamic behaviour of the system is investigated for both PCM charging and discharging processes. Furthermore, the effect of airside flow variation on the thermal response of the system is studied, and the results are discussed based on fluids temperature, heat transfer rate, and the PCM phase transition procedure. It is demonstrated that the PCM can store excess heat from the working fluid during the charging process and releases it to the airside during the discharging process. The heating load of 323 kJ is stored during the charging process which has enabled the PCM to provide up to 6 min of extra airside heating time during discharging. The share of PCM latent component of the airside heat transfer is determined to be around 48 %. It is also observed that by increasing the airflow rate, the discharged heat load is decreased slightly, and the heating time is reduced notably. The presented thermal energy storage system offers a unique solution for the start-stop function implemented in many hybrid and electric vehicles. During short periods of engine shutdown, the system could provide passenger thermal comfort and enable effective energy savings.