冷库空气幕流场的非稳态数值模拟及验证

Unsteady state numerical simulation and verification of flow field of air curtain in cold stores

为了真实地研究冷库空气幕开启后冷库气流场和温度场的变化规律,该文建立了冷库三维模型,利用CFD模拟软件对试验冷库空气幕的流场进行了非稳态模拟,预测库门和空气幕开启60s内冷库温度场和气流场的变化,并对温度场模拟结果进行了试验验证。模拟结果得出库门和空气幕开启后,空气幕射流的中心主流速度衰减慢,而两侧气流的速度衰减快,库外热空气从入口两侧和底部侵入库内;冷库内靠近冷风机一侧底部的温度上升较快;侵入的热空气改变了冷气流的流动轨迹,冷热空气存在压力差导致冷库中心处形成多个涡旋,从而破坏了库内均匀的气流组织。在今后的研究中可以通过数值模拟优化冷库空气幕的送风速度、喷口宽度等参数,从而提高冷库空气幕的隔离性能,维持库内控温要求。

The temperature in cold stores is easily influenced due to hot air infiltration into the cold store during loading and uploading. Air curtains are commonly used to cut off airflow between the cold store and a hot environment, and reduce heat and mass transfer for maintaining the low temperature in the cold store. This was done in order to study the variation of the airflow field and temperature field in the cold store when the air curtain was opened. The aim of this study was to predict the temperature field and air flow field in the cold store when the door and air curtain were opened for 60s against an unsteady state simulation of air curtain used in the cold store by using CFD software and the simulation results of the temperature field in the cold store were used for experimental verification. The simulation results reflected that when the door and air curtains were opened, the hot air easily infiltrated into the cold store from both the sides and bottom of the entrance due to the slow velocity decrease of the central mainstream and fast velocity decrease of both sides of the air curtain. The temperature of the area closer to the fan increased faster in the cold store because the air velocity of this area was so low that the temperature field of this area was easily influenced by the hot air. Furthermore, the intrusive hot air changed the cold airflow trace, and swirling eddies formed around the central area of the cold store by the pressure difference between the hot and cold air destroyed the uniform air distribution and temperature field in the cold store. In a future study, the unsteady state simulation time step of the air curtain can be increased to obtain the time in which the temperature field and airflow field reach a uniform state in the cold store.