出风道参数对冷藏集装箱温度场的影响

结合货物多孔介质理论,建立了装有荔枝货物的保鲜集装箱三维数值模型。考虑荔枝货物及箱体物理特性,通过改变出风道风速、开孔面积和位置对制冷过程中集装箱内空气和货物温度的变化进行了数值分析,获得了箱内温度场分布特性。研究结果表明,提高出风道风速、增大开孔面积,可以促进箱内空气降温速度,并提高货物表面的温度分布均匀性;货物降温速度随出风道风速增大而增大,而与开孔面积关系不明显;出风道开孔位置对箱内空气降温速度影响不大,集中开孔形式下的货物温度降幅较其他开孔形式小。经试验验证,模拟结果与试验结果吻合较好,空气温度变化平均误差为5.05%、均方根误差为5.95%;温度分布平均误差为14.04%、均方根误差为16.48%,证明了模型的准确性。

Effects of Air-outlet Duct Parameters on Temperature Distribution in Fresh-keeping Container

Temperature is one of the key factors for maintaining the quality of fruits and vegetables during storage or transportation. Improving airflow in the container is beneficial for adjusting the temperature in a container quickly and effectively. 3-D numerical models, which combined with the theory of porosity media, were built to investigate the temperature distribution in a 40 feet container. The thermal characteristics of litchi products and the container wall were considered in the models. Totally 12 models, including different air-outlet duct velocities, porosity areas and hole locations on the air-outlet duct, were conducted to study the effects of those factors on change of air and products temperature during the cooling process in the container, by which the airflow characteristics in the container were obtained and analyzed. After comparison of the data, some results can be drawn. Improving the air velocity in air-outlet duct and the porosity area of air-outlet duct can increase the cooling speed of air, which also improved the homogeneity of temperature distribution on the products surface. The effect of porosity area on products temperature was not obvious, while products temperature was decreased faster with bigger ventilation velocity. Changing the location of holes on the air-outlet duct had little effects on the temperature decrease of air, but the decreasing amplitude was smaller after cooling process when the holes were concentrated in the middle of the air-outlet duct. A test was developed to verify the results from one of the models, and the simulated results were matched well with the test results, in which the average difference rate (MD) and the root mean square error (RMSE) were 5.05% and 5.95% for change of air temperature, respectively, while those were 14.04% and 16.48% for temperature distribution in the container, respectively. The results revealed the rules of air and products cooling in a fresh-keeping container for fruits and vegetables, which provided a certain reference for the design and optimization of fresh-keeping equipments.