Thermal Properties Of Compound Low-temperature Phase Change Materials And Application In Numeric Simulation Of Refrigerator

Solving the energy crisis and power shortage has become an important topic in front of China in 21st century. Energy accumulation is one of the effective measurements proposed to solve power shortage and release energy load peak problem. Cool storage technology, by shifting electrical energy demand from peak period to off-peak period, has been a hot point in recent years. Till now,cool storage technology has been applied mainly in air-conditioning systems. Few researches were put on the low-temperature phase change cool storage materials and their application with phase change temperature below 0℃. But in the chemical,food,cryogenic logistics, low-temperature refrigerator and many other industries, a tremendous demand are requested for cool storage materials with phase change temperature below 0℃. Therefore,it's very important to research the basic physical properties of the low-temperature phase-change cool storage materials for a large-scale application in the future. In this paper, by mixing an organic and an inorganic solution, a kind of hybrid solution, with phase-change temperature from -16℃to -21℃and phase-change latent heat from 207J/g to 212 J/g, has been developed and used in refrigerator system.In the experiment,first the solidifying temperature and phase changing latent heat of ammonium chloride solution and glycol solution were tested out by employing of differential scanning calorimeter (DSC). Then a mixture solution was created by mixing the ammonium chloride solution and glycol solution in a given ratio. The solidifying temperature and phase changing latent heat of the mixing solution was also tested by DSC.The mixture solution with the highest phase changing latent heat was selected to meet the temperature range demand in cool-storage refrigerator. After the specific heat of the mixture was tested by DSC, by using a cryogenic refrigerator as the cold source and using the copper-konstantan thermal couple to test temperature, the cool storage and release process was researched and the relating curves were drawn out.By applying the FLUENT software to simulate the solidifying and melting process and the flow field as well as the temperature field of the solution in pipe cool-storage plate of refrigerator, the temperature field and solid-liquid ratio of the solution have been obtained.The solidification and melting in pipe cool-storage plate of refrigerator and temperature field and flow field of the air in refrigerator's box are simulated by the FLUENT software. The temperature field is obtained and phase change interface position changed with time is also calculated.Comparing with the common refrigerator,the results show that cool accumulation time with cool-storage plate is longer. So it can reduce the on-off frequency of compressor,avoid the power consumption and save energy. Adjusting the mass of cold-accumulating medium,storing cool-energy in night,and working on daytime without power,the power rate can be saved and"peak load shifting"will be realized. Furthermore,a more uniform temperature field and flow field will improve the food quality in refrigerator.