Electrically-triggered nucleation of supercooled sodium acetate trihydrate phase change composites

Abstract

Phase change energy storage technology has broad applications in many engineering fields, such as building energy conservation, aerospace, and thermal management of electric equipment. However, the inorganic phase change materials suffer a lot from supercooling, phase separation, and low thermal conductivity. Therefore, this paper aims at developing a novel electrically-triggered phase change composite by making use of its supercooling characteristics, achieving a controllable release of latent heat as it is wanted. Polished by radial and axial grinding respectively, both surface-triggered electrodes (STE) with a uniform rough structure and point-triggered electrodes (PTE) with the gradient rough structure were prepared to investigate the effect of surface structure on the electrical crystallization. The 100-cycle test results indicated the newly-prepared electrode achieved a stable electrically-triggering ability. The oxidation rate of electrodes was significantly affected by interface characteristics of the gas–liquid-solid interfaces. What’s more, the effect of voltage and supercooling degree on the crystallization behaviours, like induction time, morphology, and growth of the dendrite, and heat transfer process, were comprehensively investigated. With the increase of the supercooling degree, the dendrite shape gradually changed from acicular crystal to flocculent crystal, and the induction time decreased rapidly. To improve the thermal conductivity, a novel phase change composite using sodium acetate trihydrate/carboxymethyl cellulose/expanded graphite (SAT/CMC/EG) was developed. Considering both thermal conductivity and electrical nucleation, the optimized mass ratio of SAT: CMC: EG was 100:1:8. These research findings would provide valuable guidance in the intelligently-controllable energy storage technology.