The thermal conductivities of four composite paraffin phase change materials (PCMs) containing embedded multi-walled carbon nanotubes (MWCNTs) with varying dimensions were determined. The goals of this study were to investigate the interfacial thermal resistance between two MWCNTs, and to investigate the ballistic and diffusive components of the thermal resistance at the interface. It was found that the thermal conductivity of the composite PCMs increased with the diameter of the MWCNT ...