Comparative investigation on heat transfer enhancement of surface-roughened and nano-dispersed phase change material for thermal energy storage

Abstract

Considering the increasing energy demand and cost, phase change materials(PCM) are gaining momentum for efficient thermal energy storage (TES).However, beyond desirable properties, poor thermal stability is a major draw-back of the PCM. To address the same, the present study aims to comparativelyevaluate the thermal behavior of the plain encapsulated paraffin PCM, PCMwith surface-roughened (shot-peened) encapsulation, and PCM with Al2O3nanoparticles respectively. The charging and discharging characteristics wereassessed experimentally with the investigation on PCM's behavior consideringlower (0.0124 kg/s) and higher (0.0155 kg/s) air heat transfer fluid (HTF) massflow rates. Results indicated that shot-peened capsule contributed to the maxi-mum heat transfer rate due to efficient nucleating convective effect followedby nano-dispersed and plain capsules respectively. The duration for completemelting of PCM in the shot-peened capsule was 11.53% and 20.6% lesser com-pared to the other two cases. Similarly, the period of complete solidificationwas 20.23% and 10.38% lesser in shot-peened capsule compared to nano-dispersed and plain capsules. Further, the effect of HTF's flow rate was mini-mal (up to 5.95%) during both charging and discharging periods. Thus, com-paratively shot peening on the capsule's inner surface was found to efficientlycontribute to heat transfer augmentation of the paraffin wax PCM out-performing other cases.