Preparation and properties of Na2SO4·10H2O-Na2HPO4·12H2O composite shaped phase change material for greenhouse

The sodium sulphate decahydrate has limited use in solar greenhouses due to problems such as supercooling, phase separation, high temperature of the phase transition and liquid phase leakage. In this paper, Na2HPO4·12H2O was added to improve supercooling, potassium chloride to reduce the phase transition temperature, and resin as a matrix to resolve phase separation and liquid phase leakage. The mass fraction of Na2SO4·10H2O+80%Na2HPO4·12H2O+6%KCl+6% resin was tested for temperature rise and fall, DSC and cycle stability. Because of adding 80% Na2HPO4·12H2O, the degree of supercooling and the latent heat of phase change were 1.35℃ and 268.7J/g, respectively. With adding 6% KCl, the temperature of phase change can reach 23.89℃ and latent heat was 183.25J/g. Finally, adding 6% resin can suppress phase separation and liquid phase leakage of phase change materials. Its crystallization temperature, the temperature of phase change, subcooling degree and phase transition latent heat were 11.56℃, 22.61℃, 1.41℃ and 143.6J/g, respectively. The composite molding phase change material was no liquid phase leakage with heating to 50℃. The latent heat of the cycle after 100 was 127.8J/g, which was 11.2% lower than one cycle. The obtained composite molded phase change material had advantages such as a large latent heat value, the appropriate temperature of phase transition and good thermal stability, and can be applied to the field of solar greenhouses. © 2022, Chemical Industry Press Co., Ltd. All right reserved.