Experimental investigation on the charging and discharging performance enhancement of a vertical latent heat thermal energy storage unit via snowflake fin design

The application of latent heat thermal energy storage (LHTES) technology in solar energy systems is greatly restricted by the poor thermal conductivity of the phase change materials (PCM). Inspired by the natural snowflakes, a snowflake fin is designed to enhance the charging and discharging performance of the LHTES unit in this paper. The phase interface, temperature response, thermal energy storage and release characteristics, as well as the entire melting and solidification time of LHTES unit with the same material volume but varying fin designs, e.g., nullity fin, longitudinal fin and snowflake fin, are experimentally compared. Paraffin is selected as the PCM, which is filled into the annular region between the brass finned tube and the transparent acrylic shell to enable visual observation of the melting and solidification processes. Water is used as the heat transfer fluid (HTF), whose effects of various flow conditions on the charging and discharging performance of the LHTES unit were inspected. The preliminary results show that the snowflake fin design significantly reduces the entire melting and solidification time by 32.23 similar to 51.81% as compared to the longitudinal fin. In addition, snowflake fin is found to be more beneficial for the discharging process, since the time-averaged heat transfer rate of HTF only increases by 12.27% for charging but increases by 179.81% for discharging if compared to the traditional longitudinal fin. (c) 2022 Elsevier Ltd. All rights reserved.