Explore And Study Of Melted Hydrated Salts PCM Based On Thermodynamic Models

With the advent of “low carbon economy”, energy saving and emission reduction hasbecome the subject of society, to seek renewable energy and improve energy utilization havebeen focused by researchers. Explore a new energy, which can take full advantage of the heat,is an important way to solve the energy crisis. The PCM is a high–energy storage material,which can collect and release energy in the form of latent heat, has high phase transitionenthalpy, energy density and low cost, etc. However, a few of existing salt PCM is found,most of which are expensive. So, developing low cost, no security risk and great performanceof the salt PCM is a key to that the salt PCM is applied in practice. The method of“Prescription” takes a lot of time and money to find the salt PCM. Therefore, in our study,the calculation about the phase diagram of multi-component salt hydrate system is carried outwith the thermodynamics model to find the new phase change materials of energy storage.The central works as follows:（1） The current situation of five international thermodynamic models in research and application fields is evaluated, based on the characteristics of the five models as well as the subject of our research, Pitzer–Simonson–Clegg and BET two kinds of thermodynamic models have been chosen to research the binary system （Mg（NO₃）₂–H₂O,CaCl₂–H₂O, Mn（NO₃）₂–H₂O） and the ternary system （CaCl2–LiCl–H₂O, LiCl–LiNO₃–H2O, KNO₃–LiNO₃–H₂O）, according to the result of research, BET theoretical model have been selected to predict the solubility of the melted salt phase diagram.（2） Use of the BET model parameters of the binary system （Mg（NO₃）₂–H₂O, NH4NO3–H₂O, LiNO₃–H₂O, KNO₃–H₂O） to predict the solubility of the multi–temperaturephase diagram of series of ternary systems and the quaternary system （LiNO₃–Mg（NO3）2–NH₄NO₃–H₂O）, the eutectic points, which may exist in those above system, are discovered.（3） The properties of the melted salt system are tested according to the results oftheory prediction, including the material storage exothermic performance and DSC, DTA curve. The experimental results show that the eutectic point material of LiNO₃–Mg（NO3）2–NH₄NO₃–H₂O can be used as PCM, the eutectic point materials of series of ternary salt water systems can be used as potential PCM. The work of the phenomenonof supercooled and hierarchical of these three system is in progress.（4） As recycled many times, the storage performance of the PCM has declined. Ananti–precipitant, which can help improve the storage performance of the melted phase change material（LiNO₃–Mg（NO₃）₂–NH₄NO₃–H₂O）, is found by experiment. And the experimentsshowed that0.8g starch was added into40g sample, the storage performance of the PCM isbest.In this paper, the theoretical prediction and result of experiments showed that the BETthermodynamic model can play an important role in the design of PCM.