Study Of Phase Diagiam Of System Ca And Design Of Related Pcm Based On Thermodynamic Model

Under the circumstances of increasingly serious energy crisis,molten salt hydrates phase change materials attracted a wide spread attention,because they can store and release latent heat in the phase change process,and have large energy storage density and phase change enthalpy.However,that it will be time-consuming and consumable to find the correct eutectic materials as phase change materials by means of experiment measure to construct the complete phase diagram of multicomponent salt-water system.In order to obtain the potential eutectic phase change energy storage materi al in Ca(N03)2-NaN03-Mg(NO3)2-H20 and Ca(N03)2-Zn(N03)2-Mg(N03)2-H20 quaternary system,we used the BET thermodynamic model,combining the mode lparameters of Ca(NO3)2-H2O,NaNO3-H2O,Zn(NO3)2-H2O and Mg(NO3)2-H2O sub-binary systems and the salt-salt interact parameter of Ca(NO3)2O-Mg(NO3)2-H 2O sub-ternary systems,and predicted the solubility at 273.15 K and 298.15 K,and phase diagrams of two quaternary system from 273 K to 333 K,without any experimental data of quaternary system.For verifying the reliability of the model predication,we used a method of solid phase disappearance to measure t he solubility of the quaternary system at 273.15 K and 298.15 K.Comparing th e difference between dry basis moisture content of experimental data and one of model calculation value,the results show that the relative errors are not more t han 5%.Aiming at the predicted eutectic materials,the experiment of exothermal and endothermal behaviors has been measured,and results show that the predicted eutectic material posses excellent heat storage and release ability and can be used as potential phase change material.Extreme supercooling of Ca(NO3)2·4H2O limits its widespread application as an energy storage material.Due to different supercooling of Ca(NO3)2·4H2O and Zn(NO3)2·6H2O,research of viscosity and Raman information of above melten salts could be important for exploring reason of supercooling and be theoretical basis for searching nucleating agents.The results show that the viscosity of Ca(NO3)2·4H2O is large,and the Raman absorption peak of Crystal and melten salt in the low frequency region(<200 cm-1)is obviously different.The viscosity of Zn(NO3)2·6H2O is small,The difference of crystal and melten salt in Raman absorption peak in the low frequency region(<200 cm-1)is not obvious.