| With the continuous growth of China's economy,people's living standards improved significantly and people's requirements of the cold chain transport are getting higher and higher.Reasonable control of the temperature is not only the key to the entire cold chain transport system,but also the key to ensure the quality and safety of the goods.Highway refrigerated trucks are flexible,convenient and quick.It plays a very important role in the cold chain transport.Accurate control of the internal temperature distribution characteristics in the compartment is essential for the reasonable control of the temperature inside the refrigerated trucks to ensure the quality and safety of the goods.Computational fluid dynamics is a computer-based tool which is based on the control equation to simulate the flow and heat transfer problems and has been widely used in the study of temperature field in the refrigerated compartment.In this paper,the distribution characteristics of the flow field and temperature field in the refrigerated compartment are studied by the numerical simulation method and FLUENT software.In this paper,the study object is the refrigerated truck provided by a car company.First of all,the cooling performance of the refrigerated truck when it's empty and loading biological products is analyzed.According to the distribution of the temperature field and flow field in the refrigerated compartment under different air speeds,the wind speed of 4.5m/s is selected.And then the the temperature distribution characteristics in the refrigerated truck when it's empty and loading biological products are calculated and analyzed.In order to verify the accuracy of the calculation results,the calculated temperature value of each measuring point is compared with the experimental value.The simulation temperature results of the monitoring points are basically the same with the experimental value when the truck is empty,with the maximum error is about 3K.The maximum error when loading goods is about IK.The result shows that the temperature of the compartment and the cargo area can be judged accurately by the simulation.When the goods in the refrigerated compartment is apple,the heat load of the refrigerated truck is determined by analyzing the heat condition of the refrigerated truck.Then,the theoretical value of the circulating air volume and the corresponding wind speed in the evaporator outlet are calculated.Considering the effect of ambient temperature and O2 and CO2 concentration on apple's respiration,the mathematical model of cargo is established.Achieving the changes of apple's respiration caused by the temperature and gas composition concentration changes and the energy source changes of the cargo area caused by the apple's respiration through the UDF program.By calculating the influence of the air velocity in the evaporator outlet on the flow field and temperature field around the cargo area,considering the uniformity of the temperature distribution in the cargo area and the air flow rate around the cargo area,3m/s outlet wind speed is selected.The influence of the clearance between the cargo and the roof on the cargo area during steady state and dynamic cooling process is calculated.It is found that the clearance between the cargo and the roof doesn't have a significant effect on the uniformity of the temperature distribution in the cargo area during the steady state cooling process.However,the smaller the clearance,the higher the air flow rate around the cargo area,which results in increased consumption of the water of fruits and vegetables.During the dynamic cooling process,the clearance has little effect on the cooling time of the average temperature of the cargo area,but has a significant effect on the cooling time of the overall temperature of the cargo area.Lowering the same temperature,the cargo which has larger clearance with the roof spends longer time,and the greater the cooling temperature difference,the greater the difference in the cooling time of the cargo under different clearances. |
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