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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]

In order to solve undercooling and phase separation of sodium acetate trihydrate (SAT), experimental screening method was used to select nucleating agents and thickeners that are suitable for SAT, and the optimal ratio was identified. Through screening experiments of nucleating agents, it is found that disodium hydrogen phosphate can be used as an effective nucleating agent for SAT. When the weight content of disodium hydrogen phosphate in SAT is 2%, the degree of undercooling was reduced to approximately 2 K. The addition of 1–1.5% (weight) of xanthan gum (XG) to SAT can effectively inhibit the phase separation. Since the properties of SAT changes after the modification, the corresponding comparison analysis was performed. The results showed that XG has a significant influence on the SAT performance of SAT. With the addition of 1.5 wt % of XG in pure SAT, the latent heat of fusion and solid/liquid volume expansion reduce by 5.2% and 5.4% respectively, and the thermal conductivity and solid/liquid density also decreases accordingly. [ABSTRACT FROM AUTHOR]