Morphologies and thermal characterization of paraffin/carbon foam composite phase change material

Paraffin/carbon foam composite phase change material (PCM) was prepared with vacuum assistance in the present study, and the structure and thermo-physical properties of the composite PCM were studied. The impregnation ratios were studied comparatively for the cases with and without vacuum assistance, and the results showed that the impregnation process with vacuum assistance was superior to that without vacuum assistance. Micro-Computed Tomography (Micro-CT) technique was used to investigate the inner structural characteristics of the composite PCM. The gray value analysis was conducted, and two dimensional (2D) cross-section images and three dimensional (3D) renderings were constructed accordingly. Both the surface porosity and bulk porosity were obtained from the image analysis. Compared with pure paraffin, the thermal conductivity of the composite PCM was enhanced, e.g., the composite PCM with vacuum assistance was about three times larger than that of pure paraffin. The measured thermal conductivity showed agreement with the theoretical models. The phase change behaviors of the composite PCM were investigated with a differential scanning calorimeter (DSC). The presence of the porous carbon foam affected the phase change behavior of pure paraffin in that the extrapolated onset melting/freezing temperatures shifted from 52.10/60.56 °C for pure paraffin to 51.73/61.16 °C. The thermal effusivity of the composite PCM was larger than that of pure paraffin, which was apparently advantageous for latent thermal energy storage (LTES).