Thermal conductivity enhancement of a sodium acetate trihydrate-potassium chloride-urea/expanded graphite composite phase-change material for latent heat thermal energy storage

摘要

To create an energy-efficient heat pump latent heat thermal energy storage (HPLHTES) system, a novel sodium acetate trihydrate (SAT)-potassium chloride (KCl)-urea/expanded graphite (EG) composite phase-change material (CPCM) was developed in this study. EG was introduced into the base composite salt to prepare the novel CPCM, SAT-KCl-urea/EG. The thermal properties, crystalline phase, and morphology of the resulting CPCM were experimentally characterized. It was found that the SAT-KCl-urea/EG CPCM comprising 9 wt% EG was optimal for affording improved thermal-energy storage performance without compromising phase-change properties. The obtained CPCM exhibits an appropriate melting point of 47.5 degrees C and a high phase-change enthalpy of 200.3 kJ/kg. The thermal conductivity of the SAT-KCl-urea/EG CPCM was 1.48 W/mK, approximately 5.3 times that of the SAT-KCI-urea composite salt (0.28 W/mK). The required phase-change duration of the SAT-KCl-urea/EG CPCM was approximately 30% less than that of the SAT-KCI-urea composite salt. After 100 thermal-cycle tests, the SATKCl-urea/9 wt% EG CPCM retained a desirable phase-change temperature of 45.9 degrees C, high latent heat of 190.8 kJ/kg, and an acceptable supercooling degree of 1.56 degrees C. These thermal feature results showed that the SAT-KCl-urea/9 wt% EG CPCM exhibited great potential for use in the HPLHTES systems. (C) 2020 Elsevier B.V. All rights reserved.