Improving Supercooling and Properties of Hydrated Salt Phase-Change Materials Using Binary Nucleating Agent

This study employed sodium acetate trihydrate as the phase-change matrix and used a binary nucleating agent composed of disodium hydrogen phosphate dodecahydrate (DHPD) and borax (BX) to suppress supercooling. Sodium carboxymethyl cellulose (CMC) was used as a thickener to mitigate phase separation, and expanded graphite (EG) was introduced as a supporting matrix to enhance thermal conductivity. The composite phase-change material was prepared via melt blending. By means of thermal storage and release performance tests, differential scanning calorimetry and thermal conductivity tests, the effects of the binary nucleating agent ratio, CMC content and EG addition amount on phase-change thermal storage performance, supercooling degree, phase stability and thermal conductivity of the system were systematically investigated. The results indicated that the addition of 3.0 wt% DHPD and 2.0 wt% BX as the binary nucleating agent reduced the supercooling temperature from 20.52 °C to 1.92 °C; 1 wt% CMC effectively suppressed phase separation during thermal cycling; and the incorporation of 3.0 wt% EG increased the thermal conductivity of the composite to 2.92 times that of the pure hydrated salt.