Heat transfer enhancement of charging and discharging of phase change materials and size optimization of a latent thermal energy storage system for solar cold storage application

In this work, phase change material (PCM) is considered as thermal energy backup system for solar cold storage applications when there is peak power demand or power failure or no sun shines situations. A numerical study of solidification (charging) and melting (discharging) of PCM validated by experimental data is performed to explore the performance of a unique latent heat thermal energy storage (LHTES) system. The LHTES unit (PCM pack) occupied with PCM acts as a heat exchanger made up from evaporator tube along with rectangular metal fins which enhance the heat transfer during phase changing of PCM. Evaporator with 5, 8, 10, and 12 longitudinal aluminum fins, and without fin inside the PCM pack of six different thicknesses (4.5 cm, 5.0 cm 5.5 cm, 6.0 cm, 6.5 cm, and 7.0 cm) are considered to investigate the charging and discharging characteristics of PCM in our present study. To obtain the best performance from the PCM pack, heat transfer characteristics and temperature distributions of PCM, and the effect of variation of thickness of the PCM pack are studied through computational fluid dynamics (CFD) simulation. Solidification and melting model of ANSYS Fluent 15.0 package employing enthalpy-porosity technique is used to develop 3-D simulation models. Faster solidification, as well as a higher energy storage capacity and heat flux during melting is found for the PCM pack of 6.5 cm thickness with higher number of fins. A lab scale experimental set-up is fabricated to compare the present simulation results which shows reasonably well validation during both the charging and discharging.