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In order to solve the phase separation problem of Na2S2O3·5H2O–CH3COONa·3H2O PCM (phase change material), sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), xanthan gum (XG), sodium polyacrylate (PAAS) and polyacrylamide (PAM) were selected as additives. The effects of different proportions of the above thickeners on the supercooling degree, phase separation, phase change temperature and latent heat of Na2S2O3·5H2O–CH3COONa·3H2O system were studied by using the cooling curve and DSC, so as to screen the best thickener for eutectic PCM. The experimental results show that CMC, XG and PAAS can eliminate the phase separation of Na2S2O3·5H2O–CH3COONa·3H2O. Among them, the optimal ratio of CMC, XG and PAAS is 3 mass%, 3 mass% and 1 mass%, respectively. From the perspective of heat storage performance, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O. The phase change temperature is 40.5 °C. The subcooling degree is about 14.7 °C, and the latent heat is about 221 J g−1. The melting time is 15 min. Only PAAS can make Na2S2O3·5H2O–CH3COONa·3H2O eutectic PCM completely exothermic at room temperature, which can not only play the role of thickener to eliminate phase separation, but also is a nucleating agent. After 100 melting-solidification cycles, the change rate of latent heat value was only 5%, and the change rate of phase transition temperature was less than 1%. Considering heat storage performance and cyclic stability, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O PCM. [ABSTRACT FROM AUTHOR]

This paper had carried out the optimization screening experiment for the nucleating agent and thickening agent of sodium acetate trihydrate (SAT) targeting its problems of supercooling and phase separation. Our results verified that the addition of 2 mass% disodium hydrogen phosphate dodecahydrate in SAT could effectively suppress the SAT supercooling and control the degree of supercooling within 2 K. Besides, the addition of 1–1.5 mass% xanthan gum in SAT could effectively suppress its phase separation during melting/freezing cycle and could evenly disperse the nucleating agent in SAT. Moreover, comparative test analysis on the modified SAT suggested that the thickening agent in the additive had great influence on the SAT physical property parameters. Additionally, to improve the comprehensive utilization quality of the modified SAT, the modified SAT thermodynamic analysis was performed, which discovered that the initial charging temperature had little influence on the exergy efficiency of the modified SAT, while the final charging temperature had great influence on the exergy efficiency. Typically, the optimal final charging temperature of the modified SAT was 72 °C. [ABSTRACT FROM AUTHOR]