Numerical Simulation Of Thermal And Humid Environment In Fruits And Vegetables’ Cold Store

It is well known that the exchanges of heat and mass are very complicated in coldstore．Some empirical methods were used to optimize the selection of refrigerationequipment and determine storage conditions in the past．But it is proved that thosemethods have their own limitations and quality control of food can’t get reliableguarantee. The method of Computational Fluid Dynamics (CFD) is applied to study thedynamic distributions of cold store, therefore it is possible to optimize the design ofrefrigeration equipment and quality control of food products．The research target of this paper is an fruit and vegetable cold store in Yan ’an.The physical and mathematical models of cold store are established. The distribution ofthe thermal and humid environment in the cold store respectively from the cooling fanair supply speed, the layout form of goods, and the respiratory heat of the goods werestudied by numerical simulation. Main conclusions of the study are as follows:(1) Under the condition of empty cold storage, the thermal and humid environmentis simulated. It is concluded that the there is a big backflow area in the cold store. Thecharacteristics of the flow field are attached with a wall flow and the velocity is smallerat the wall corner. The velocity distribution presented this phenomenon that velocity inthe center is slow and in the both side is high. The temperature and humidity arewell-distributed. It is not suitable for the goods to pile up within2m away from the wallof the inlet side of the cooling fan and1m from the wall which is opposite from thecooling fan outlet side.(2) With the goods dividing into two stacks, the distribution of the thermal andhumid environment in the cold store is simulated under different air supply speed. Theresults indicate that with the increase of air supply speed, the center reflux area has a trendence to move to the top and the distribution velocity is presented large. Thedistribution of the temperature and relative humidity has little change, the condition cansatisfy the requirement of the goods storage. a low velocity is suggested in order tosaving energy and reduce consumption of dry goods.(3) The distribution of thermal and humid environment is simulated under differentstacking forms. By comparing the simulation results of these stacking forms, it isconcluded that with the increase of the number of the goods, the performance of the gasflow become much better and is good to the exchange of the heat and humidity. Alongwith the increase of the number of goods, the temperature decreases and a slightlydifferent distribution of temperature and humidity happen. It will also make thedistribution of velocity more homogeneous and the consumption of goods graduallyreduced;(4) The distribution of thermal and humid environment is simulated under differentrespiratory heat. Compared the simulation results, the respiratory heat has significanteffects on goods consumption. With the increase of respiratory heat, the temperature isrelatively an apparent increase, while the relative humidity reduces. The consumption ofgoods is greater during the period of storgage and it is disadvantageous for the storageof the goods.This paper aimed at the distributions of temperature, humidity and relativehumidity on the surface of goods in cold store. The results provide certain guidancefunction in controlling the temperature and humidity during storage time so as to reducethe weight loss.