A kind of composite phase change materials (PCMs) was prepared by the process of “melting blend - solidification and form-stable” to improve the comprehensive performance of PCMs. Palmitic acid (PA) is used as PCM and expanded graphite (EG) is used for the supporting material. Twenty-one kinds of form-stable composite PCMs were prepared with different contents of EG. The morphologies and structures were characterized microscopically by SEM. On this basis

heat transfer performance analysis

thermophysical test

thermal stability test and heat storage performance analysis were conducted. SEM morphological characterization showed that PA could be absorbed into the pores of EG and the distribution was uniform. DSC test results revealed that the melting enthalpy of PCMs is 193.01 J/g with the 70%(mass) PA corresponding to the melting point of 61.08℃. The melting enthalpy of pure PA is 275.35 J/g corresponding to the melting point of 59.53℃. The thermal conductivity of the PCMs is significantly improved by the addition of EG. When the sample density was 900 kg/m3 and the content of EG was 30%(mass)

the thermal conductivity of the composite PCM is 14.09 W/(m·K)

which is about 87 times higher than that of pure PA. Cycle stability tests were carried out

the results suggest the samples with 24% and 30% EG content have no any change in shape

and therefore show excellent cycle stability in repeating charging and discharging processes.