Research on heat transfer performance of composite phase change materials based on expanded graphite

Pure paraffin was used as phase change medium, and expanded graphite was added to reinforce the heat-conducting skeleton. Subsequently, a composite phase change material(CPCM) with excellent thermal conducting property was prepared. A visualized testing platform was set up to analyze the influence of adding material mass fraction on the melting process of composite phase change materials under constant heat flux condition. The difference in heat transfer performance and regularity of the composite phase change material with various mass fractions were investigated. In addition, the evolution of the temperature distributions was visualized by using the infrared thermal imager at specified points during the melting process. The results show that the thermal performance of CPCM can be furtherly enhanced by adding EG-100. When the mass fraction is 5%, the thermal diffusion coefficient of the CPCM based on EG-100 is increased by 42% compared with that of the CPCM based on EG-80. When 2% or 4% heat conduction enhancement material is added, the natural convection inside the material is weakened in the later stage of melting, resulting in a decrease in the overall heat transfer effect. Adding 6% of thermal conductivity enhancement material improves the overall heat transfer performance. As the mass fraction of thermally enhanced materials increases, the heat transfer along the y-direction inside the composite phase change material is basically unaffected, but the thermal stratification along the direction of gravity(z-direction) gradually decreases. © 2021, Central South University Press. All right reserved.