Research on Average Control of Temperature Field in Refrigerated Transport Carriages

In order to solve the problem of uneven temperature distribution in refrigerated transportation carriages, which directly leads to the deterioration of the nutritional status and quality of characteristic fruits such as Yangmei, the orthogonal experimental method was used to optimize the design, and the evaluation index of average temperature field was introduced. The influence of factors such as the speed of the airflow circulation fan, the porosity of the uniform flow plate, and the vertical spacing of the cargo frame on the temperature field inside the refrigerated transportation carriage was analyzed. Effect note: The higher the fan speed, the better the average temperature field, and the highest temperature inside the chamber is basically stable; The smaller the porosity, the better the average temperature field. When the porosity is 0.1, the highest temperature inside the chamber is the lowest; The smaller the vertical spacing within a certain limit, the lower the maximum temperature, and the better the uniformity. Aiming at the "Cenling" region in the temperature field, a refrigerated transportation box structure was designed based on the principle of field synergy. The average control was achieved by adjusting the deviation of the air curtain fan at the right return air outlet.

Accepting refrigerated and fresh transportation is the main link in the logistics process of perishable agricultural products. In the cold chain transportation process, it is necessary to control its temperature and humidity limitations and uniformity to ensure taste and quality. Yangmei, as one of the characteristic fruits, is highly sensitive to temperature. The suitable storage temperature is 0-2 ℃. The higher the temperature, the greater the rate and magnitude of the decrease in nutrients such as sugar, total acid, and vitamin C, and the lighter the flavor of the fruit. The current structure of refrigerated transportation carriages generally exhibits uneven temperature distribution within the compartment due to the unreasonable airflow circulation and cargo stacking methods, resulting in some fruits not being at the appropriate temperature and not being able to meet the transportation requirements of characteristic fruits well. Therefore, it is particularly urgent and important to control the flow field movement inside the refrigerated compartment, optimize and adjust multiple design parameters, reasonably allocate the entire compartment's cooling capacity and airflow organization, and design a new type of refrigerated compartment to ensure the uniformity of the temperature field inside the compartment, in order to reduce transportation consumption of yangmei and ensure taste quality.

In recent years, with the widespread application of Computational Fluid Dynamics (CFD) as a numerical calculation tool in the food industry [2], some scholars have adopted this method to simulate and analyze the internal flow field of refrigerated carriages and carried out structural improvement designs [3-10].

This article takes the refrigerated transportation of characteristic fruit Yangmei in the Yuyao area of Zhejiang Province as an example. Through numerical simulation of the temperature field inside the box, 96 temperature sensors are deployed on a real vehicle to measure and record temperature data in real time, in order to compare and verify the accuracy of the CFD model built. Analyze the influence of the rotational speed of the airflow circulation fan, the porosity of the uniform flow plate, and the vertical spacing of the shelves on the average temperature diffusion, apply the orthogonal experimental method to find the optimal parameter combination, obtain the temperature diffusion areas of each longitudinal and transverse section in the carriage, and use the split air curtain at the return air outlet to effectively control the average temperature inside the carriage, in order to provide a basis for controlling the average temperature inside the refrigerated transportation carriage and optimizing the structural design, Provide guidance for long-distance transportation of Yangmei.