Effect of paraffin wax with carbon nanotube on melting latent heat under different pressures: A molecular research

Abstract

Composite organic phase change materials (PCMs) with nanoparticles have attracted considerable interest in various fields. Latent heat and thermal conductivity are the critical properties of composite organic PCMs. To improve thermal conductivity and prevent leakage, composite PCMs are often encased in containers. However, during the phase transition, the pressure of the PCM changes due to a volume change. The change in latent heat caused by pressure can greatly impact the performance of PCMs and has not been investigated. We simulated the melting process of paraffin wax with carbon nanotubes under different pressures and investigated the relationship between pressure and latent heat. The results show that a small change in pressure does not significantly affect the latent heat, but a large increase in pressure will inhibit the release of latent heat. The decrease in latent heat is mainly due to the difference in total enthalpy between solids and liquids. Solids can build up more energy at high pressure, but the atomic structure of liquids fails to maintain the same energy. As a result, the increase in energy of solids and liquids do not match, leading to a decrease in latent heat. Our study aims to provide a reference for future PCM applications.