Numerical Simulation And Experimental Research On Phase Change Cold Storage Heat Exchanger Of Cold Plate Refrigerated Vehicle

With the improvement of living standards,people have higher requirements for the quality of food.Cold chain logistics technology has been paid more and more attention.At present,there are problems such as low transport efficiency and high energy consumption in cold chain transportation.For this reason,The General Office of the State Council issued the Circular on the Issuance of the "14th Five-Year Plan" cold chain logistics Development Plan,in order to solve the shortcomings such as high carbon emissions,long cooling time and slow cooling release speed of refrigerated vehicles in the current market.The research of this paper provides technical guidance for the design and transformation of cold plate refrigerated truck.This paper studied a kind of cold storage heat exchanger which could be used in cold plate refrigerated vehicle.The heat exchanger was fixed in the cold plate refrigerated vehicle,and could be used as the cold storage plate,which could be filled without disassembly.The cold storage heat exchangers were connected together by pipelines,which could achieve complete the cooling process.In order to increase the cooling rate of the cold storage heat exchanger,the structure of the cold storage heat exchanger was optimized by combining numerical calculation and experiment to shorten the cooling time.In order to improve the charging rate of the heat exchanger,the optimization of the structure of the heat exchanger was carried out by the research method combining numerical calculation and experiment,so as to shorten the charging time.This paper mainly did the following work:(1)A cold storage and charging unit test piece were established,and a single-pipe ice storage experiment was conducted on the charging pipe.A three-dimensional numerical simulation of single-pipe ice storage was also established,and the accuracy of the simulation results was verified through experimental data.Firtly,the freezing point,latent heat value and thermal conductivity of the coolant were measured as-1.87℃,318.5kj/kg and1.104W/m K by differential scanning calorimetry(DSC)and Hot disk;The ice storage speed of cold storage units with different pipe diameters at different temperatures of brine(-12.5°C,-15°C,-17.5°C and-20°C)was simulated by numerical simulation.The research found that the smaller the tube diameter of the cold storage unit and the lower the temperature of the brine,the more favorable it was to increase the ice storage speed.Considering the factors such as ice storage time,pressure loss and energy consumption,the optimal tube diameter of the cold storage unit was determined to be 10 mm and the temperature of the refrigerant is-15℃.(2)Secondly,on the basis of studying the cold storage characteristics of the cold storage unit,the cold storage heat exchanger was designed,and the two-dimensional material flow distribution numerical model of the cold storage heat exchanger was established,and the material distribution characteristics of the cold storage heat exchanger with different inlet forms were numerically simulated.Compared with the "upward and downward" type,"left in and left out" type of heat exchanger,the "slope" type of heat exchanger had the best distribution uniformity of logistics,the use of "slope" type of heat exchanger in the design of the structure ice storage speed is the fastest.(3)Finally,the heat load of the refrigerated truck was calculated by heat balance,and the total mass of the refrigerated ice was obtained.Three kinds of arrangement of cold storage plates were studied,and a three-dimensional numerical model of cooling release of heat exchangers was established.It was found that the average temperature variation trend in the refrigerated vehicles with three arrangement modes was basically the same,and the temperature went through the process of temperature rise,temperature balance and temperature rose successively.The average air temperature in the carriage in mode 3 was lower than that in the other two modes,and the temperature fluctuation was smaller and the temperature uniformity was better.