The Heat Transfer Performance Research In The Cold Chain Box Based On Stirling Refrigerated Technology

As a very large branch of cold chain logistics industry,pharmaceutical cold chain is faced with huge problems such as difficult terminal transportation and large energy consumption due to multi-batch and small-batch of pharmaceutical transportation.At the same time,the strict refrigerating conditions in the transportation and transshipment of biological samples also put great pressure on the pharmaceutical cold chain transportation.At present,most of the common logistics transport vehicles are equipped with cold chain box without cold source to solve this problem.However,in the process of distribution,cold chain box without cold source cannot effectively maintain the constant temperature required by biological samples,while the cold chain box with cold source can better solve the above problems.Therefore,this paper applies the Stirling refrigeration system to the portable cold chain box,so as to meet the requirements of the cold chain box with cold source in the aspects of compact structure,light weight,wide refrigeration temperature range,high refrigeration efficiency and environmental protection of refrigeration working medium.In this paper,the cold chain box with cold source is taken as the research object.The Stirling refrigeration system is used to design the cold displacement device to make the cold displacement efficiency higher.Fluent software is used to simulate the refrigeration rate of different cold source structures,the refrigeration performance of cold chain box in the air / load state and the insulation performance of cold chain box after the cooling is stopped.With the combination of numerical simulation and experimental data monitoring,the cooling effect and temperature field uniformity of the medical cold chain box were studied systematically.The main research work and results are as follows:(1)The thermal calculation of cold load and gravity heat pipe of cold chain box is carried out.Taking Stirling refrigerator as the cold source,the structure of compound cold displacement device is designed to obtain the cold end cooling capacity more efficiently,so as to ensure the adequacy and continuity of the cold source.(2)Based on the numerical simulation of the placement angle of the gravity heat pipe,the optimal placement angle was determined to be 30°.After verifying the grid independence,the models of the cold chain box with different cold source structures are simulated.The comparative analysis shows that the composite cold source structure has high refrigeration efficiency and the temperature in the cold chain box was more uniform.(3)The temperature field in the cold chain box with cold source is simulated by FLUENT software,so as to study the refrigeration and insulation characteristics of the whole box.The results show that: when no load refrigeration,the average temperature of the cold chain box reaches the required temperature in about 28.6min.The most unfavorable point took about 36.75 min to reach the required temperature,and the cooling time difference was about 8min.During load refrigeration,plasma with an initial temperature of 273 k was built in,and the plasma was frozen for about 39.97 min.when the plasma was frozen,the average temperature of the box and plasma decreased gently.After the refrigeration is stopped,the insulation effect is similar to the cold chain box with no cold source.(4)Design and build the temperature measuring bench and monitor the temperature of each characteristic point in the box.According to the comparative analysis of simulation data and experimental data,there is 1.1% ~ 3.9% allowable error between the simulation value and the measured value.Through the research and analysis of the practicability of cold chain box with cold source in the direction of medical cold chain,the theoretical basis and important reference are provided for its future promotion.