Numerical Simulation And Optimization On Temperature Field In Cold Store

The cold store,a key link of cold chain,plays a vital role in ensuring food quality.Whether the distribution of flow field in the cold store is reasonable or not exerts a direct influence on the quality of food.Especially,when opening the door,owing to temperature difference between the outside and inside of cold store,there will be strong heat transfer near the door.Invasion of outside hot air will not only beget a rise in inside temperature,causing by the decline in the quality of goods,but also produce vapour,thus blocking operator’s view.What’s worse,it may lead to frosting on the surface of evaporator,heat transfer deterioration,etc.In order to solve these problems,installing air curtain on the top of door is a good way,because it is able to spray jet flow as the brattice and isolate from external heat.For this reason,air curtain has been more widely used.Since the sealing effect of air curtain can be affected by many parameters,if any improper selection occurs during operation process,the curtain will not only fail to realize favorable function,but waste energy.It is necessary to study the distribution rules of the flow field and the performance of air curtain.With upgrade of computer functions,numerical simulation technology has been more widely used in the refrigeration field.Low-cost,fast and correct in solving complicated problems,and accurate in simulating the distribution of flow field,the technology is of great importance for the rapid development of refrigeration industry.By use of computational fluid dynamics(CFD)and numerical simulation technology,the paper was focused on steady and unsteady state simulation of the temperature field in the cold store and the results were used for experimental verification.In addition,the research simulations on explores parameters and fitting styles of air curtain were done to provide reference for optimizing flow field of the cold store,improve quality of stored goods,and reduce energy consumption,etc.Analysis of the above-mentioned problems,the conclusions were listed as follows,(1)A small experimental cold store was taken as research object,and standard k-ε model,SIMPLEC and PISO algorithm were used to simulate the temperature field in cold store under the steady and unsteady state.The results showed that when the door of the cold store was closed under steady state,the temperature at the corner of cold store was slightly higher,when the door was opened,intensive heat exchange occurred near the door,especially upper part of the door.At 30 s,their temperature was up to about 10℃,when the door was closed,the temperature of cold store recovered to the initial state with more than 30 s.(2)A large cold store loaded with goods was taken as the research object,and the stacked goods were modeled to simulate and verify the temperature distribution in the cold store under steady state,and to further study the variation regularity of temperature field when the door was opened and air curtain was installed.The results showed that the temperature fields were unevenly under steady state,especially in the place near goods where had relatively higher temperature,its temperature was-18℃,the temperature of other areas were basically maintained at-22℃,when an air curtain was installed on the top of door,the hot-air entering into the cold store reduced significantly,and if the blowing-in velocity of air curtain was 8 m/s,external environment would exert minimum impact on the temperature field of the cold store.(3)A large cold store installed with vertical air curtain inside,vertical air curtain outside and horizontal air curtain were selected as research objects,they were applied to simulate the change of temperature field of the cold store.The results showed that the vertical air curtain inside created a good seal but increased energy consumption,vertical air curtain outside met the requirements with relatively lower energy consumption,and horizontal air curtain met basically the requirements,but the location of the air curtain caused inconvenience to operation.