Preparation and thermal properties of Na2HPO4•12H2O composite phase change material for thermal energy storage

Disodium hydrogen phosphate(Na2HPO4•12H2O) had some problems such as supercooling, phase separation and low thermal conductivity affecting its applications in the low temperature thermal storage. Therefore, it needs to be further improved. By means of the selecting experiment of nucleating agent and thickening agent and adding thermal conductive enhancer nano-iron oxide(α-Fe2O3), composite phase change energy storage materials with mass ratio of Na2HPO4•12H2O+2% Na4P2O7•10H2O+1% xanthan gum(GX)+0.2% α-Fe2O3 were prepared, and the solidification exothermic test, thermophysical properties test and cycling stability test were carried out. The results showed that the nucleating effect of adding 2% Na4P2O7•10H2O was the best and did not decrease with the increase of cycle times, and the degree of supercooling was maintained at about 2℃. GX can effectively control the phase separation of Na2HPO4•12H2O, for which mass ratio of 0.75%~1.25% was much better. α-Fe2O3 can effectively improve the thermal conductivity of Na2HPO4•12H2O, and mass ratio of 0.2% can increase by 90.8%. The latent heat of composite phase change energy storage materials was 252J/g after 150 cycles, which decreased by 7.4%. The phase change temperature was 35.4℃, while the supercooling was 1.3℃.The thermal conductivity was 2.054W/(m•K), which was 100.2% higher than that of pure materials. The modified composite materials with the suitable phase change temperature, high latent heat, high thermal conductivity and stable thermal performance can be widely used in heat pump storage, greenhouse production and heat dissipation of electronic devices. © 2019, Chemical Industry Press. All right reserved.