Gelled Na2HPO4 center dot A 12H(2)O with amylose-g-sodium acrylate: heat storage performance, heat capacity and heat of fusion

摘要

A novel gelling method was studied to stabilize phase change material Na2HPO4 center dot A 12H(2)O with amylose grafted sodium acrylate. Gelled Na2HPO4 center dot A 12H(2)O shows stable heat storage performance prepared at optimized conditions: 2.7mass/mass% sodium acrylate, 0.4 mass/mass% amylose, 0.05-0.09 mass/mass% N, N'-methylenebisacrylamide, 0.05-0.09 mass/mass% K2S2O8 and Na2SO3 (mass ratio 1:1), at 50 A degrees C. Na2HPO4 center dot A 12H(2)O was dispersed in gel network as tiny crystals less than 0.1 mm. Melting points were in the range 35.4 +/- A 2 A degrees C. Short-term thermal cycling proves the effectiveness of the novel method for eliminating phase separation in the gelled salt. Adiabatic calorimetric measurement of heat capacities shows two phase transitions, which correspond to melting of Na2HPO4 center dot A 12H(2)O and freezable bond water in gel, respectively. Heat of fusion of pure Na2HPO4 center dot A 12H(2)O was determined as 260.9 J g(-1). Distribution of extra water is: free water:freezable water:nonfreezing water = 0:0.85:0.15.