| Energy is an important material foundation of human survival and development,which associate with the development of modern society and the prosperity of economy. In recent years, along with the continuous development of the domestic construction industry, building energy consumption was increased gradually. Under the current low energy efficiency situation, the rapid growth of energy demand made the exhausted of fossil energy and pollution of environmental more and more serious. Therefore, how to reduce building energy consumption has become one of the important subject that human face.Room-temperature PCM is an efficient material for building energy efficiency, because it can be used to store the heat of low temperature and reduce indoor temperature fluctuation, and become an important part of building energy saving technology.Hydrated salt phase change material has stable properties, high thermal storage density, high thermal conductivity, low price, and mostly belongs to the low temperature phase change energy storage material, which can be used for the preparation of room-temperature PCM, its application and market prospect is considerable. In this study, MgCl2·6H2O and CaCl2·6H2O which are the by-products of the potash production of the Chaerhan salt lake and industrial soda production respectively were used as raw materials to study the preparation of CaCl2·6H2O–MgCl2·6H2O room temperature phase change energy storage material.The room-temperature PCM of CaCl2·6H2O–MgCl2·6H2O were prepared by adding 10wt%, 15wt%, 20wt%, 25wt% of MgCl2·6H2O respectively. Through experimental determination, their phase transition temperature were in 21~25 ℃ and gradually reducing along with the increased content of MgCl2·6H2O. There was a serious super-cooling behavior in their solidification process, the condensate depression were more than 10 ℃. In response to the super-cooling and phase separation defect, in this research, modification experiment was proceeded to the Ca Cl2·6H2O–25wt%MgCl2·6H2O room-temperature PCM by adding nucleating and thickener agents. In the modified experiment, this study adopted the uniform experiment method instead of the traditional single factor experiment. According to the quadratic regression analysis, the effective nucleating agents and thickener were selected successfully. SrCl2·6H2O and SrCO3 are effective nucleating agents, and HEC is excellent thickener. Finally, the stable PCM was prepared, its phase change temperature and latent heat are 21℃ and 102.3 J/g, respectively. The composition of additive is 3wt% SrCl2·6H2O + 1wt% SrCO3 + 0.5wt% HEC. After 50 times melt-crystallization experiment, the heat storage performance of PCM does not appear serious attenuation, this material has an excellent and stable thermal storage performance.In the experimental application research, the room-temperature PCM was packaged with PE and PE-aluminum foil composite material. Thermal storage element was made, and the heat exchanger model and phase change heat storage water tank model was design by using room-temperature PCM. In the application of heat storage water tank, PCM increases the storing capacity of the hot water tank of heat storage. Compared with ordinary water tank, the phase change heat storage water tank has a slower cooling rate, which can maintain the water-temperature for a long time, though experimental determination, it can maintain more than 600 minutes on water temperature above 20 ℃. Additionally, after 50 times thermal storage- exothermic cycle, phase change heat storage water tank still has good heat storage capacity, this room-temperature PCM can be applied to solar heating system. |
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