Thermal performance evaluation of a latent heat thermal energy storage unit with an embedded multi-tube finned copper heat exchanger

The experimental thermal characterization during charging and discharging of a prototype compact latent heat thermal energy storage system (LHTESS) with an embedded horizontally oriented finned multi-tube copper heat exchanger is presented. The thermal store was filled with a commercial-grade, CrodaTherm (TM) 60, phase change material (PCM) with a nominal melting temperature of 60 degrees C. The proposed heat exchanger (HX) configuration mitigates the effect of low PCM thermal conductivity and increases the rates of heat transfer to and from the store during the charging and discharging processes compared to multi-tube copper HX without fins. The experimental testing regime assessed the impact of heat transfer fluid (HTF) volume flow rate and inlet temperature on I) transient PCM temperature distribution, II) the total charging/discharging time and III) instantaneous/average power during the charging and discharging processes. The experimental results showed that the HTF volume flow rate and inlet temperature play a significant role in the thermal performance of the LHTESS during the charging/discharging process. During the charging process, the influence of increasing HTF inlet temperature is greater than that due to increasing HTF volume flow rate. Moreover, it is shown that during the first 30 minutes of the discharging process, the average power output was 4.3, 5.1 and 5.3 kW for HTF volume flow rate of 2.5 and 7.2 and 10.5 l/min, respectively.