The Effect of Expanded Graphite on the Caloric Properties of Paraffin Wax of 50°C Melting

Expanded graphite (EG) is a promising component to improve the thermophysical properties of paraffin wax (PW) for its use as a phase change material (PCM) for thermal energy storage. The objects of study were followed PCMs: industrial PW, PW containing 0.0320, 0.0362, and 0.0399 g.g
⁻¹
of EG. The procedures of the vacuum impregnation of EG by PW were utilized during composite PCM preparation. The measurement of the enthalpy of phase transition was performed by the method of monotonic heating in the calorimeter of variable temperature. The temperature dependences of the effective specific heat capacity during samples cooling in the range of 25…65 °C were obtained. It was shown that the presence of EG in PW contributes to a slight decrease in the temperatures of the start and finish of the phase transition and deterioration of the enthalpy of phase transition by 3.3…6.9 % (depending on the EG mass fraction). The obtained results can be explained by structural changes in the PW due to molecular interaction between PW and the extended surface of EG.