Expanded Graphite/Paraffin composite phase change materials: Effect of solvent and ultrasonication on thermal properties.*

The broad application of phase change materials (PCMs) is restricted due to their low thermal conductivity. Numerous techniques have been applied to enhance the thermal conductivity of PCMs, one of which is the use of Expanded-graphite (EG) as a thermal enhancer. High thermal conductivity, low density, and chemical inertness make EG a great candidate for enhancing the thermal conductivity of PCMs. The present work focuses on enhancing the thermal conductivity of Paraffin based PCMs with the use of EG via various preparation techniques. Two different mesh sizes of EG were used to make EG/Paraffin composite PCM (CPCM). The results demonstrated that the smaller mesh size EG leads to a better enhancement in the thermal conductivity of CPCM. The CPCM was prepared via the vacuum impregnation method followed by hot pressing the prepared mixture in the mold. Acetone and Dimethylformamide (DMF) were used as solvents during the mixing of paraffin and EG. When solvents were used better homogeneous dispersion of EG in the CPCM. An ultrasonic tip-sonication time study showed sonicating EG in acetone for 30sec at 20% amplitude gave the best enhancement in thermal conductivity of CPCM.