Comprehensive evaluation of Paraffin-HDPE shape stabilized PCM with hybrid carbon nano-additives

Thermal energy storage using phase change materials (PCMs) is of great interests in many fields, especially in solar thermal applications. To overcome the leakage problem caused by phase change and the low thermal conductivities of most PCMs, the current study prepared and tested two Paraffin-HDPE-based composites by adding two hybrid Carbon Nano-additives (CNs) fillers: Expanded Graphite-Multi-walled Carbon Nanotube (EG-MWCNT) and Expanded Graphite-Carbon Nanofiber (EG-CNF). A comprehensive evaluation method was first proposed based on the Efficacy Coefficient Method (ECM) to assess the thermal performance of Paraffin-HDPE shape stabilized PCM (SSPCM). Seven individual indexes, including phase change temperature, latent heat, thermal conductivity, leakage rate, specific heat of both solid and liquid phase, and heat storage/heat release rates, were measured and applied to obtain the overall efficacy coefficients of the prepared SSPCM composites. The results showed that in all studied composites, n-octadecane-HDPE/EG-MWCNT composite exhibited the best comprehensive thermal performance with an optimal mass ratio of EG and MWCNT being 4:1.