Effect of temperature and graphite particle fillers on thermal conductivity and viscosity of phase change material n-eicosane

Organic materials like simple, long chain n-alkanes have high latent heat and find application as a phase change material (PCM). In this work, we measure the thermal conductivity, k, and viscosity, µ, of n-eicosane (C20H48) as a function of temperature, and examine the effect of homogenously dispersed graphite particles (GP) in the PCM. Our results show a large enhancement in k (450%) and µ (1200%) for a 3.5% vol. concentration of GP fillers. The surprising reduction of the interfacial thermal resistance (Reff) with increasing filler concentration, together with the high thermal conductivity of GP contributes to the large enhancement in k. Reff increases with temperature when n-eicosane is in solid phase and decreases after phase transition. The enhancement in µ is attributed to the layering of liquid n-eicosane at the graphene surfaces, and agglomeration of GP at higher concentrations.