| The continuous growth of the world population and economy,along with the improvement of people’s living standards and the rapid development of modernization,coupled with the rapid process of urbanization,has led to the huge growth of energy demand and the increasing consumption of electricity.As a household appliance that needs to run continuously for 24 hours,the refrigerator has become one of the household appliances with the highest energy consumption.The thermostatic chamber can provide a suitable storage temperature for the food,so that the food can be kept fresh for a long time,but for the food that needs precise temperature control,the thermostatic chamber cannot meet the requirements.The appearance of the constant temperature fresh-keeping room can keep the food fresh without freezing,and preserve the nutrition of the food to the maximum extent without destroying the nutritional structure of the food itself.The temperature of the constant temperature fresh-keeping room of the refrigerator is generally about 0 ℃.Although the existing refrigerator preservation technology is very advanced,the temperature distribution inside The thermostatic chamber is still uneven and the temperature rises too fast.The application of phase change materials can effectively improve the temperature distribution,prolong the heat preservation and save energy.In this paper,two different methods were used to prepare organic composite phase change materials with a temperature of about 0 °C.Chemical properties,microstructure and thermal properties of variable materials are analyzed.Then a group of phase change materials with suitable properties are selected and applied to the thermostatic chamber.The numerical simulation method was used to apply the phase change material to the constant temperature chamber of the refrigerator,to study the extension of the internal heat preservation time of the refrigerator under the condition of shutdown and power failure of the refrigerator compressor,to improve the internal temperature fluctuation and energy saving.The thermal conductivity of n-decanol-lauryl alcohol binary eutectic aliphatic alcohol was prepared by porous media adsorption method,expanded graphite was used as supporting material,and nano-silicon carbide was used as thermal conductivity enhancing particles.The leakage experiments show that expanded graphite has good adsorption,and its maximum adsorption rate can reach 92%.Using the expanded graphite with a mass ratio of 8% as the adsorption material,3%,5%,7% and 9% of silicon carbide composite phase change materials were added.Chemical structure and morphology characterization of composite phase change materials by Fourier transform infrared transform and scanning electron microscopy.The results show that silicon carbide is successfully adsorbed on the surface and pores of expanded graphite,and the n-decanol-lauryl alcohol phase change material,silicon carbide and expanded graphite are only physically combined without chemical reaction.Its thermal properties were characterized by DSC,TGA and thermal conductivity instruments.The analysis results show that the melting and solidification temperatures of CPCM-3 with a mass proportion of 3wt% silicon carbide are-0.85℃ and 1.08℃,respectively,the latent heat of melting and solidification are 85.62j/g and 74.94j/g,respectively,and its thermal conductivity is 1.31 W/m·K is 1.21 times that of n-decanol-lauryl alcohol/expanded graphite,and has good thermodynamic properties and thermal stability.The thermal conductivity of n-decanol-n-decanoic acid binary eutectic aliphatic alcohol was prepared by solution blending method,expanded graphite was used as support material,and boron nitride was used as thermal conductivity enhancing particle.Fourier transform infrared transform and scanning electron microscope test results show that boron nitride is well adsorbed on the surface and pores of expanded graphite,and the materials are only physically combined without chemical reaction.Its thermal properties were characterized by DSC,TGA and thermal conductivity instruments.The analysis results show that the melting and solidification temperatures of SPCM-3 with3wt% boron nitride are-3.68℃ and-3.92℃,respectively,the latent heat of melting and solidification are 129.2j/g and 128.2j/g,respectively.Its thermal conductivity is It is 0.75 W/m·K,which is 4.4 times that of n-decanol-n-decanoic acid/expanded graphite,and has good thermodynamic performance and reliability.The composite phase change material prepared is applied to the intermediate constant temperature chamber of a three-door refrigerator by numerical simulation.Taking 4°C as the upper limit of the temperature of the thermostatic chamber,during the shutdown or power failure of the refrigerator compressor,for the two arrangements of PU2 and PU4,the internal holding time of the thermostatic chamber increases with the increase of the thickness of the phase change material cold storage plate.The heat preservation time of 10 mm phase change material cold storage plates PU4 and PU2 are14.89 and 4.64 h respectively,and the heat preservation time is 37 and 11.5 times of that without adding phase change material.The cooling efficiency of the two types of phase change material cold storage plates increases with the increase of the thickness of the cold storage plate.When the thickness is 10 mm,the cooling efficiency of PU4 is 0.77,which is twice that of PU2.The cooling efficiency of PU2 increases less with the increase in the thickness of the cold storage plate.Three different refrigerator insulation materials were used to study the changes of the phase change material cold storage plate on the temperature of the thermostatic chamber under different insulation materials.The study found that the use of VIP insulation materials with low thermal conductivity can greatly prolong the insulation time.A new type of composite thermal insulation material was obtained by adding VIP thermal insulation material to PU thermal insulation material,and its thermal insulation time was 4 times that of PU,and it had a higher liquid percentage.The application strategy of phase change materials and thermal insulation materials in the thermostatic chamber of refrigerators can provide a certain guiding value for realizing the preservation of refrigerator food and maintaining low temperature inside the refrigerator under the condition of power failure. |
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