Effect of carbon nanotubes on melting latent heat of paraffin wax: An experimental and simulated research

Abstract

Paraffin wax (PW) is a typical organic phase change material (PCM) widely used in energy storage systems, and carbon nanotubes (CNT) are general additives to improve thermal conductivity. The latent heat of PW with a low mass fraction of CNT is explored in experiments and simulations. Both experiments and simulations show additives will decrease the melting latent heat of the material. For experiments, the lowest melting latent heat is 177.2 J/g, with a decrease of 1.6 % compared to pure PW. Besides the melting temperature barely changes with the mass fraction (about 325 K for both pure PW and composite PCM). The experimental results also show CNT is covered by PW uniformly, and CNT in materials keeps clusters and knots. The simulation shows that the decreasing melting temperature is caused by the energy change between PW and CNT. Moreover, the dense layer is not the reason for the decreasing latent heat. The latent heat of the material is affected by the energy change between PW and CNT. The final latent heat is closely connected to the sensible heat of the material. For PW adding a low mass fraction of CNT in normal atmospheric pressure, the final latent heat would be high if a material can keep a high melting temperature and high constant-pressure specific heat.