Enhanced thermal energy storage of a paraffin-based phase change material (PCM) using nano carbons

Thermal energy storage performance of a paraffin-based phase change material (PCM) enhanced by nano graphite and nano coconut shell charcoal was investigated. The nano carbon concentration was 0.02, 0.06, and 0.10 wt%, respectively. To understand the influence of nano carbons on the thermal behavior of PCMs, the melting process of nano-enhanced PCMs (NePCMs) was monitored using thermocouples and an infrared camera, in comparison with the melting process of pure paraffin. It was found that the melting process of NePCMs without dispersant was accelerated with nano carbons at concentration of 0.02 wt%, although the thermal conductivity of NePCMs with higher concentrations was higher. With increasing concentration, the melting process was decelerated because of the agglomeration of nano carbons and the suppression of natural convection. To eliminate the agglomeration, Span 80 and oleic acid were used as dispersants for the PCMs with 0.06 wt% and 0.10 wt% nano graphite. The melting process was accelerated further with the increasing concentration of the nano graphite. The shortest melting time was realized using 0.06 wt% nano graphite and 2.0 wt% oleic acid, which was 21% shorter than the pure paraffin. Moreover, it was noticed that the data from thermocouples were not able to represent the melting process accurately because of the limited measuring points, especially for the melting process with agglomeration and sedimentation.