Application Research Of Controllable Separate Heat Pipe In Cool-storage Refrigerator

The direct-cooling refrigerators have large temperature fluctuation in the fresh food compartment which leads the poor food preservation ability.At the same time,the compressor starts and stops frequently 24 hours a day,which results in very high energy consumption.The application of phase change cold storage technology in the storage refrigerator not only benefits the”peak cutting and valley filling" of the power grid,but also reduces the temperature fluctuation of the fresh food compartment and the start-stop frequency of the compressor,which saves energy and extends the compressor life.Separate Heat Pipe(SHP)can use the electromagnetic valve to actively control the start-stop of the heat pipe to achieve precise temperature control.Therefore,the application of phase change cold storage materials and SHP in refrigerators has a good application prospect.In this paper,the following work has been carried out on the research of a new type of cold storage refrigerator with SHP:1)The experimental scheme of using the original evaporator of the refrigerator as the evaporation section of the SHP system is proposed.In this article,The heat transfer performance and filling rate of the SHP system under four different working fluids are simulated and experimentally studied.The optimal filling rate of the corresponding working fluid is obtained,and the heat transfer performance and temperature control performance of the four working fluids are compared.The experimental results show that R407C has the best heat transfer performance at 23.5%filling rate and the temperature in the fresh food compartment can be reduced from 25? to 5? in 90min,and to 2? in only 129min.Moreover,when the temperature in the fresh food compartment is maintained at 5 ? and 2?,the operating rate of the SHP is only 26.01%and 51.24%,respectively.The good heat transfer characteristics and temperature control capabilities of the SHP can meet the requirements of the new cool-storage refrigerator.2)The cold storage and cold release processes of inorganic eutectic salts are analyzed by using the step cooling curve.The eutectic point concentration of the sodium chloride salt solution is obtained,which is in good agreement with the chemical manual.However,since sodium chloride has low solubility at low temperatures,phase separation is apt to occur when it is repeatedly used.The orthogonal test method is used to initially screen the phase change cold storage materials of glycerol/sodium chloride/water and ethylene glycol/sodium chloride/water,and then the ratio is gradually adjusted,finally three kinds of phase change cold storage materials are screened.The peak temperature of the phase change cold storage materials is-18.4?-23.7?.and its phase change latent heat and phase transition temperature range are measured by DSC curve.3)A new experimental platform for cold storage refrigerator with separate heat pipes is built.The feasibility of the new refrigerated refrigerator is verified by cooling experiments and related experimental results are discussed.The results show that the new cold storage refrigerator can realize the cooling of the fresh food compartment by using the start-stop control of the SHP and the cold storage and release function of the phase change material.At 25 ? ambient temperature,the fresh food compartment can be cooled down from 25? to 7? in 185min.