Investigation on the thermophysical properties and transient heat transfer characteristics of composite phase change materials

In this paper, the thermophysical properties and transient heat transfer characteristics of composite phase change materials (CPCMs) were investigated numerically and experimentally in details. Two kinds of microencapsulated phase change materials (MEPCMs) paraffin with melting temperatures of 28 and 37 °C, respectively, were employed in this paper. The CPCMs were fabricated by intercalating expanded graphite (EG) with average diameter of 45 m into MEPCMs. The addition amount of EG were 10%, 30%, and 50% in weight. The thermophysical properties, including density, thermal conductivity and specific heat, of the CPCMs were measured and the latent heat and specific heat were calculated from data with differential scanning calorimetry (DSC). In the experiment, the square enclosure has a cross-section dimension of 100 by 100 mm and it was 15 mm in thickness. The top side wall of the enclosure was heated with isothermal cooling on the bottom side wall while the remaining side walls were thermally insulated. The numerical model which is designed to meet the conditions of the experimental parameters was employed to examine the transient heat transfer characteristics for the CPCMs in the enclosure. Results show that MEPCMs with increasing EG would increase the thermal conductivity and the heat transfer rate. However, the specific heat of CPCMs would decrease. The numerical predictions agree well with the experimental data. In addition, the results disclose that the CPCMs could enhance the rate of heat transfer and energy storage, but minor loss in total energy storage.