Abstract: A new type of composite phase change material (PCM) for heat dissipation of power battery was prepared. Paraffin, octadecanoic acid and octadecanol were used as the PCM materials, and expanded graphite was used as the filler for heat conduction material. Differential scanning calorimetry (DSC) was used to test the variation of thermal properties with temperature. Octadecanoic acid and octadecanoic alcohol mainly affect the temperature range and the latent heat of phase change materials, respectively. The optimal phase change material contains 56% paraffin, 16% octadecanoic acid and 28% octadecanol. The melting temperature of phase change material is 48 ℃, and the latent heat of phase change is 241.9 kJ/kg. The thermal conductivity and heat transfer behavior of PCM were studied by adding expanded graphite in the self-designed storage/heat release device. The results show that the thermal conductivity of PCM can be increased by adding expanded graphite. At the same time, it will make the heat distribution more uniform, and weaken the temperature imbalance phenomenon. The heating rate of the phase change material in the lower layer is faster when the expanded graphite is added at different horizontal surfaces. On the same horizontal plane, the heating rate of PCM is consistent with the direction of temperature transfer, that is, the heating wall is outside, so the heat transfer direction is from outside to inside, and the heating rate is gradually slowed down from outside to inside.

Key words: Paraffin, Octadecanoic acid, Octadecanol, Expanded graphite, Phase transition temperature, Phase change latent heat