Experimental analysis of the thermal performance of beeswax-heat exchanger as latent heat thermal energy storage system

This study presents the development of an experimental setup aimed at evaluating the thermal efficiency of a functional prototype of a latent heat thermal energy storage (LHTES) system throughout its discharging and charging phases. The LHTES system comprises a shell housing a horizontally positioned multi-tube heat exchanger, along with a bio-phase change material (PCM) beeswax serving as the energy storage medium. The experimentation involved an assessment of various operational parameters, notably the flow rate and inlet temperature (Tin) of the heat transfer fluid (HTF), on the power input/output of the LHTES system, its solidification/melting durations, as well as the released and stored energy. Results from the experiments indicated a notable effect of increasing the Tin on the charging duration, in contrast to variations in the volume flow rate of HTF ( (VHTF)-H-center dot). The charging period spanned 138, 118, 112, 106, and 80 mins for the (VHTF)-H-center dot = 50, 100, 150, 200, and 250 L/h, respectively, at Tin = 70 degrees C. However, for charging the LHTES system at a constant (VHTF)-H-center dot = 100 L/h, the completion times for Tin = 70 and 80 degrees C were recorded as 118 and 99 mins, respectively. Moreover, the experimental analysis revealed that the discharging duration significantly exceeded the charging time due to the progressive formation of a solid PCM layer around the heat exchanger's external surface during the discharge procedure, thereby diminishing the heat transfer rate between the PCM and HTF. This phenomenon remained largely consistent regardless of variations in the (VHTF)-H-center dot.