Thermal Property Enhancement of a Novel Shape-Stabilized Sodium Acetate Trihydrate-Acetamide/Expanded Graphite-Based Composite Phase Change Material

Phase change materials (PCMs) are a kind of highly efficient thermal storage materials which have a bright application prospect in many fields such as energy conservation in buildings, waste heat recovery, battery thermal management and so on. Especially inorganic hydrated salt PCMs have received increasing attention from researchers due to their advantages of being inexpensive and non-flammable. However, inorganic hydrated salt PCMs are still limited by the aspects of inappropriate phase change temperature, liquid phase leakage, large supercooling and severe phase separation in the application process. In this work, sodium acetate trihydrate was selected as the basic inorganic PCM, and a novel shape-stabilized composite phase change material (CPCM) with good thermal properties was prepared by adding various functional additives. At first, the sodium acetate trihydrate-acetamide binary mixture was prepared and the melting point was adjusted using acetamide. Then the binary mixture was incorporated into expanded graphite to synthesize a novel shape-stabilized CPCM. The thermophysical properties of the resultant shape-stabilized CPCM were systematically investigated. The microscopic morphology and chemical structure of the obtained shape-stabilized CPCM were characterized and analyzed. The experiment results pointed out that acetamide could effectively lower the melting point of sodium acetate trihydrate. The obtained shape-stabilized CPCM modified with additional 18% (mass fraction) acetamide and 12% (mass fraction) expanded graphite exhibited good shape stability and thermophysical characteristics: a low supercooling degree of 1.75 degrees C and an appropriate melting temperature of 40.77 degrees C were obtained; the latent heat of 151.64 kJ/kg and thermal conductivity of 1.411 W/(m<middle dot>K) were also satisfactory. Moreover, after 50 accelerated melting-freezing cycles, the obtained shape-stabilized CPCM represented good thermal reliability.