Thermal Analysis of Phase Change Materials by Utilizing Nanoparticles

Abstract

Latent TES systems utilize phase change materials (PCMs) which at a suitable temperature range can be melted and thus store thermal energy. The stored energy is removed during the reverse process which solidifies the PCM. Due to the superiority of high latent heat compared to sensible heat, PCMs can contribute to the reduction of the storage systems’ size offering a promising solution especially when coupled with solar collectors. Despite the aforementioned advantages, the relatively low thermal conductivity of PCM hinders their wide utilization. In the present study, a thermal analysis of phase change materials is carried out. Different types of phase change materials (PCMs) are analyzed at various temperature ranges. The energy equation for the PCM is solved by implementing a 1D explicit finite difference scheme in Matlab and the results are compared with corresponding results deriving from Comsol. The properties of the utilized PCMs are altered accordingly so as to take into account their variation during phase change. In this analysis, only the thermal behavior of a PCM is investigated while the gravitational effect is neglected. The results of the analysis regard the temperature variations within the phase change material, the stored energy in the PCM per volume unit, the process speed and the effect of thermal conductivity on phase change, especially on the melting front displacement. Primary results have shown that the stored energy depends on the heat source and on the utilized PCM. In order to tackle the problem of PCM low conductivity, nanoparticles are added so as to enhance the stored energy due to the higher thermal conductivity. Upon the addition of two types of nanoparticles, the enhancement of melting fraction and stored heat are determined.