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

Abstract: 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.