The effects of various carbon nanofillers on the thermal properties of paraffin for energy storage applications

The addition of carbon nanofillers to phase change materials (PCMs) has received much attentions recently. The shape effects of carbon nanofillers on the thermal properties of paraffin were investigated in this work. Four types of nanocomposite PCMs were prepared by mixing paraffin with multi-wall carbon nanotubes (MWCNTs), graphitized MWCNTs, nanographene with different layer numbers (GNP-B, GNP-C). It shows that phase change enthalpy of nanocomposite PCM decreases gradually with the increasing of the loading of carbon nanofillers. Due to the nucleating action of carbon nanofillers, the supercooling degree of nanocomposite PCM slightly decreases. The microstructure of the nanofillers plays an important role in enhancing the thermal conductivity of paraffin. It is the flaky structure of GNP shows a more significant effect on enhancing the thermal conductivity of paraffin than the tubular structure of CNTs, which is confirmed by comparing the melting/freezing time of PCM. In the four kinds of carbon nanofillers, GNP-C shows the greatest thermal conductivity enhancement up to 52.4 % at the loading of 3 mass%.