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

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 drawback of the PCM. To address the same, the present study aims to comparatively evaluate the thermal behavior of the plain encapsulated paraffin PCM, PCM with surface-roughened (shot-peened) encapsulation, and PCM with Al2O3 nanoparticles respectively. The charging and discharging characteristics were assessed experimentally with the investigation on PCM's behavior considering lower (0.0124 kg/s) and higher (0.0155 kg/s) air heat transfer fluid (HTF) mass flow rates. Results indicated that shot-peened capsule contributed to the maximum heat transfer rate due to efficient nucleating convective effect followed by nano-dispersed and plain capsules respectively. The duration for complete melting of PCM in the shot-peened capsule was 11.53% and 20.6% lesser compared to the other two cases. Similarly, the period of complete solidification was 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 minimal (up to 5.95%) during both charging and discharging periods. Thus, comparatively shot peening on the capsule's inner surface was found to efficiently contribute to heat transfer augmentation of the paraffin wax PCM outperforming other cases.

Automated summary

This study compares the thermal behavior of different encapsulated paraffin PCMs and finds that surface-roughened encapsulation contributes to the highest heat transfer rate. The duration for complete melting and solidification of PCM in the shot-peened capsule is significantly shorter compared to other cases, while the effect of air heat transfer fluid (HTF) flow rate on heat transfer is minimal.