Aluminum Ammonium Sulfate Experimental Study Of Phase Change Material

With thermal energy storage (TES) material, the technology of heat storage can be used to balance the disparity of energy demanding and supplying via energy stored or released properly. Many problems such as the lack of energy resource and environment polluting could be worked out. Phase change materials, a kind of energy storage material, has a large capability of heat and a relatively steady process of heat storage and releasing, which is isothermal approximately and easy to control.Ammonium alum is an inorganic hydration PCM, using in the area of low temperature. Its melting point is 93.95℃, latent heat 269kJ/kg and heat transmitting coefficient 0.55W/m.K. Many characteristics of Ammonium alum are propitious to energy storage, such as a higher melting point and a larger heat storage density. But a greater super-cooling degree during the heat releasing will restrict its application in practice.The research proposed an effective method solving above problems through both theoretical and experimental investigation. Firstly, we analyzed and studied the crystal mechanism of phase change materials as well as reasons and influence factors of super-cooling. A solution was summed up to reduce super-cooling degree, adding addictives to the phase changed material.Based on the theory study, series of experiments were carried into execution: selecting some effective nucleating agent from a sum of addictives, determining the percentage of nucleating agent and other addictives in total heat storage material. At the same time, the experiment also contained a DSC testing in order to measure the latent heat variety of phase change material during melting and crystal circulation. The test was designed to keep circulated for 100 or even more times.After abundant experiments we got a delightful result: the most effective addictives to improve the heat storage performance of Ammonium alum is 21.8% calcium fluoride (CaF₂) and 0.3%active carbon(C), added with 6%deionized water. Cooling experiment proved that whether the melting material is cooled in the air or constant temperature water, the heat releasing velocity will grow with the circumstance temperature falling, which makes super-cooling more serious.It is not very ideal for the DSC testing result. The latent heat presented an obvious attenuation just after 60 times' phase changing circulation. However, we will have an earnest analysis to perfect the experiments in further research.The production resulted from experimental researches will become a powerful support of application in the large area for ammonium alum. Also it will rich the study methods and content of study field of phase change storing energy materials.