INFLUENCES OF EXPANDED GRAPHITE ON THERMAL CHARACTERIZATIONS OF ERYTHRITOL , PARAFFIN, AND STEARIC ACID FOR LOW - TEMPERATURE PHASE CHANGE MATERIAL COMPOSITES

Phase change material (PCM) composites for latent thermal energy storage were made by mixing three different kinds of PCM (erythritol (Er), stearic acid (SA), and paraffin (Pa)) loaded with expanded graphite (EG) in liquid PCM with a mass fraction of 5, 10, and 20 wt%. The effect of EG on thermal behaviors of the PCM composites was evaluated. As a result, the thermal conductivity of the PCM composites increased with increasing the EG content. Among the three types of the PCM composites, EG/Er composites were observed to have relative enhancement up to 84.02% at 20 wt% EG content . However, the latent heat was somewhat decreased from 251.08 to 214.58 J/g owing to the presence of EG which caused the decrement of super cooling effect. Thermal cycling and thermal gravimetric analyses showed that the PCM composites had good thermal rel iability and proper thermal stability. Therefore, the prepared PCM composites were appropriate for thermal energy storage applications because of their acceptable thermal conductivity, good thermal reliability, fast response speed, and proper thermal stabi lity.