Thermal properties and thermal conductivity enhancement of composite phase change material using sodium acetate trihydrate–urea/expanded graphite for radiant floor heating system

Abstract

For heat exchanger used as latent heat storage system, heat storage capacity and thermal conductivity of phase change material are key indicators to determine its performance. In this paper, sodium acetate trihydrate-urea non-eutectic mixture as phase change material and expanded graphite as thermal conductivity enhancer, a sodium acetate trihydrate-urea/expanded graphite composite phase change material (CPCM) with both high latent heat and thermal conductivity for heat exchanger was developed by physical mixing method. The mass fractions of urea in the mixture and expanded graphite in CPCM were optimized. The crystalline phase and morphology of the obtained CPCM were characterized by X-ray diffraction and scanning electron microscope, and its thermal properties were investigated systematically. The results showed that the prepared CPCM containing 8% urea and 8% expanded graphite had a suitable phase change temperature (47.84 °C), high latent heat (223.1 kJ·kg−1), low supercooling degree (1.54 °C) as well as a satisfactory thermal conductivity (2.076 W·m−1·K−1). Moreover, the CPCM possessed a good shape stability and comparable thermal reliability. The results indicate that the obtained CPCM is an up-and-coming candidate for heat exchanger.