Abstract: The supercooling and phase separation of hydrated salt phase-change heat storage materials are two key issues that affect thermal stability and heat-storage performance of hydrated salt phase change heat storage materials. Using MgCl₂·6H₂O (MCH) as the main material and MgSO₄·7H₂O (MSH) as the nucleating agent, the composite phase change system MCH/MSH is prepared by the melt blending method. The effects of MSH on the phase change enthalpy, phase-change temperature, supercooling degree and phase separation phenomenon of composite phase-change materials are studied. The results show that the phase-change heat storage performance of MCH/MSH system constructed with appropriate amount of MSH is significantly higher than that of MCH. The system show the smallest supercooling, the best phase separation inhibition effect and the best heat storage performance when the MSH content is 5%. Its initial enthalpy change value can reach 330.91 kJ/kg, and the stable value can reach 254.43 kJ/kg after the cycle test, showing the prepared MCH/MSH composite material has good heat storage performance and cycle performance.

Key words: composite phase-change material, heat storage, supercooling, the phase separation, thermal cycle stability