Characterization of expanded graphite-based erythritol/urea eutectic phase change material and corresponding mathematical solar heating application analysis

Abstract

• Preparation of binary eutectic mixture of erythritol and urea. • Thermal property of eutectic with various expanded graphite contents was studied. • Supercooling and thermal conductivity of erythritol/urea eutectic were optimized. • Performance of solar heating system with phase change materials tank was studied. The mid-temperature phase change materials have attracted wide attention in solar energy storage. In this study, erythritol and urea binary eutectic mixture was prepared and expanded graphite was used to reduce supercooling and enhance thermal conductivity of the binary material. The supercooling of binary eutectic mixture with 3 wt% expanded graphite was 7.43 K, which was 43.03 K less than pure binary mixture (50.46 K). The thermal conductivity of composite phase change material was 2.25 W·m −1 ·K −1 , which was approximately 3.73 times higher than the pure eutectic mixture. The test of corrosion results turned out that the new-made material had lower corrosion rate to common metal materials. X-ray diffraction and Fourier transform infrared spectroscopy tests exhibited that no chemical reaction was triggered during the preparation of the proposed composite. The energy consumption of the solar heating system with the proposed composite was numerically investigated by TRNSYS software. Compared with the traditional heating mode, composite phase change materials integrated solar heating system could save 5 tons of standard coal in a heating season for a building with heating area of 1125 m 2 in Tianjin, China. Therefore, it is proposed as a promising phase change material for solar energy storage.