Charging and discharging processes of low capacity nano-PCM based cool thermal energy storage system: An experimental study

The present study aims to investigate the performance of the low-capacity energy storage tank in different heat transfer fluid (HTF) conditions (at various flow rates) filled with spherical capsules containing nano-enhanced phase change material (nano-PCM). The nano-PCM is prepared by dispersing functionalized graphene nano-platelets (f-GNP) with deionized (DI) water. The influence of HTF inlet temperature and volumetric flow rates on the total charging and discharging time of an energy storage tank filled with 35 spherical capsules are analyzed. The maximum reduction in total charging and discharging time of 18.26% and 22.81% is recorded for different HTF conditions. The amount of latent heat energy stored is nearly 5.5 times higher than the sensible heat stored at the HTF temperature of-4 degrees C. The cumulative energy recovery of 2637 kJ is recorded during the discharging process, which is 85.89% of the actual energy stored (3070 kJ) in the storage tank. In addition, the dispersion of f-GNP reduces the specific energy consumption (SEC) by around 28% for the nano-PCM at-4 degrees C HTF tem-perature. It is found that the required output temperature and average melting rate can be achieved in practical applications through the control of the flow rate of HTF and its inlet temperature.