Experimental and numerical study on the thermal energy storage performance of a novel phase-change material for radiant floor heating systems

Thermal energy storage shows great potential for improving the energy performance of building heating systems. Phase-change materials are a promising type of storage medium for building envelopes due to their high storage capacity. However, the low thermal conductivity and easy leakage of the hydrated salts inhibit their practical application. In this study, sodium acetate trihydrate-acetamide/modified expanded graphite was prepared as a novel thermal-stable storage medium for space heating applications. Leakage protection tests showed that modified expanded graphite presented a better compatibility with hydrated salts. The thermal conductivity of the novel composite reached 1.87 W/m•K, 4.5 times higher than that of the pristine mixture. Moreover, the PCM exhibited a great thermal reliability with a high latent heat of 161.9 kJ/kg and an acceptable supercooling degree of 2.2 °C after cycling. The thermal performance of radiant floor heating systems with different layer structures was evaluated. The heat storage and release of the storage medium were beneficial for reducing the temperature fluctuation and improving the indoor comfort. The operation cost of the system without the storage medium was 73.1% higher than that with the storage medium. This performance enhancement suggests that the novel composite is a competitive candidate for heating applications.