关键词: 相变储能材料, 热力学模型, 水的活度, 溶解度, 蒸汽压

Five widely used typical thermodynamic models were selected to describe and predict the thermodynamic properties of the six binary salt-water systems, LiCl-H2O, LiBr-H2O, CaCl2-H2O, Mg(NO3)2-H2O, MnCl2-H2O and Mn(NO3)2-H2O. The predicted results were compared with reliable experimental results, showing that the primitive Pitzer model has poor prediction ability. The extended Pitzer model, although can reproduce the thermodynamic properties of a binary system to a quite high salt concentration, shows weak extrapolation prediction ability. The Pitzer-Simonson-Clegg model can reproduce and predict thermodynamic properties of some binary systems with satisfactory results. However, when the salt concentration range used for the parameterization of the thermodynamic models is far less than the solubility limit, the Pitzer-Simonson-Clegg model can not give accurate property prediction of the saturated solution. S-MSA model can not give accurate thermodynamic property prediction of the saturated solution. Furthermore, the requirement of solution density for this model limits its application. The BET model, showing strong extrapolation ability in all six binary system, is worthwhile to be recommended for the application in theoretical design of phase change materials.

Key words: phase change material, thermodynamic model, water activity, solubility, vapor pressure