Effects of nanoparticles on phase change heat transfer rate in the presence of Rayleigh-Benard convection

This paper experimentally analyzes the effects of nanoparticles on the melting time of Nano-enhanced Phase Change Materials (NePCMs) when Rayleigh-Benard convection is involved. To understand the effects of nanoparticles on the phase change rate reported in many studies, the changes in the parameters affecting the heat transfer are studied. These parameters are identified using scaling analysis on the heat transfer of NePCM in an enclosure heated from the bottom. Al2O3 nanoparticles are dispersed in a PCM (coconut oil) with different concentrations. Several experiments are conducted on these samples to understand whether the effects of nanoparticles on the phase change rate change at different experimental conditions. The results show that the melting rate may increase, decrease or remain unchanged with adding a certain concentration of nanoparticles if the heat transfer conditions change. Adding nanoparticles to a PCM is not recommended in an enclosure heated from the bottom at high Grashof numbers due to the greater Grashof number reduction, although adding nanoparticles to a PCM may reduce the melting time at small Grashof numbers due to the improvement in the thermal conductivity. With the experimental data and scaling analysis, correlations are developed to estimate the effects of nanoparticles on the melting rate and the solid-liquid interface location in the presence of Rayleigh-Benard convection. (C) 2020 Elsevier Ltd. All rights reserved.