Preparation and characterization of paraffin/expanded graphite composite phase change materials with high thermal conductivity

Paraffin/expanded graphite (PCM/EG) composite phase change material was prepared. The microstructure, thermal properties and cycle stability of PCM/EG were characterized. The results show that the thermal conductivity of PCM/EG increases with EG content and block density increasing. When EG content is 20%, paraffin can be adsorbed completely and there is no obvious leakage during 60 melting and solidification cycles. EG lamella structure is formed during compression process of PCM/EG, which is perpendicular to pressure direction and beneficial to enhance the directional thermal conductivity. The thermal conductivity of PCM/EG20%-800(b) along EG lamellar structure direction is 7.82 W m−1 k−1, which is 47.8% higher than that perpendicular to EG lamellar direction. In addition, experimental studies were carried out on PCM/EG melting process to reveal the effects of EG content, block density and EG lamellar direction on temperature control performance. The results show that the average temperature of heating surface in melting process of PCM/EG20%-800 is 46.2 °C, which is 4.0% lower than PCM/EG16%-800. In addition, when heat flow direction is parallel to EG lamellar structure direction, the average surface temperature is 44.8 °C, which means a better temperature control effect. The present work provides an efficient method to enhance PCM/EG heat storage and temperature control performance under fixed latent heat.