Experimental Research And Numerical Simulation On Air Curtain For The Cold Store

The cold store is a special building which is used to low temperature storage, and it make sure quality of the storage inside. On the working process of the cold storage, the door needs to be opened and closed frequently due to the input and output of goods, and a strong heat and mass transfer will happen around the door of the cold storage due to the invasion of the outside hot-air. As results, the temperature in the cold storage will definitely rise, the quality of storage goods will be affected. Moreover, the air cooler and the calandria of evaporator will frost faster, and the heat transfer efficiency will decrease. Therefore, an air curtain will be usually stalled near the door of the cold storage. The air curtain consists of the ventilator, air ducts, air handling equipment and air distributor. It produces jets through the cross-flow wind wheel and forms a wind wall to prevent the heat and mass transfer between the outside and the inside environments. At present, the cold storage is still researched at the basic of the empty cold storage. However, the real cold storage has stored the goods. Therefore, it’s necessary to treat the cold storage with goods as the research object and optimize the flow field of cold storage. Traditional construction in cold store usually takes engineering experience and physical measurements in order to ensure a uniform flow field of cold storage. Nonetheless, the result is not accurate and couldn’t receive complete visual analysis. With the development of computer technology, computational fluid dynamics mainly conducts numerical simulation of cold storage containing goods, and experimental measurements are combined to obtain cold storage air distribution and internal flow field, temperature field, on the basis, it is verified that air curtain can effectively block the invasion of hot air outside the cold store, and ensure the quality of goods. The purpose of this article is also aimed to be useful to manage a cold store.(1)A small cold store in the labs of Shanghai Ocean University was selected as a model, goods were stacked in the cold storage, the actual operation of production was simulated, standard k-ε two-equation model was selected, natural convection was taken into account, and more precise second order upwind scheme was adopted, for goods in the cold storage, Ergun equation was introduced to establish its porous media model and its three-dimensional goods stacking was also established. Combined with boussinesq, firstly steady-state simulation of airflow distribution was assumed, and temperature field and velocity field inside the cold storage were gotten.(2) On the basis of the previous chapter of steady-state simulation, open the door of the cold storage, the fluid field of the small cold store was simulated by computational fluid dynamics in 1 min with unsteady-state simulation after door opening, and the results showed that, in the previous chapter of steady-state simulation, air temperature field and velocity field inside the cold storage were in a steady state, with door opening, hot air outside continued to invade the refrigerator, and exchanged heat with air flow, led to temperature raise 2-4℃ in the cold store, and affected quality of the goods.(3) Test and verify the CFD results in the cold store, 1min after the cold storage door opening, the cold storage was filled with a lot of heat air, then to open the air curtain at the door, after the air curtain opening for 1 min, non-steady-state simulation was carried out. The study validated that air curtain can really isolate the heat exchange in a cold store between the internal and external air flow, with air curtain opening, hot air invading into the cold storage was isolated outside the door, then the inside temperature field in a cold store was recovered gradually to the desired condition after about 50 s.