Stability Of Flow Field During The Loading Process&Operating Mode Of Air Cooler In Cold Storage For Fruits And Vegetables

Temperature is the most important parameters of fruit and vegetable storage environment, hence the air cooler is important device to keep the interior temperature stable. There are some problems existed in the practical process of fruit and vegetable storage, such as unreasonable management, unsatisfactory preservation and low energy efficiency. Therefore, the study of flow field stability during the loading process and operating modes of air cooler in fruits and vegetables cold storage are of great values to change the current situation to improve the storage quality of fruit and vegetable, optimize cold storage design, achieve energy saving in cold storage and develop high level agricultural cold chain.This paper takes one cold store for apple in Xi’an as the research object. A three-dimensional unsteady numerical calculation model of storage environment was developed. The temperature field of the cold storage during the loading process and different operating modes of air cooler were studied concerning the factors on temperature stability of cold storage in the actual operation and management. The main research work is as follows:(1) The numerical simulation and experimental verification were carried out on temperature changes at some points at the cold storage during the loading process. The numerical results are in good agreement with the measured results. This model can be used to describe accurately the temperature change of the cold storage.(2) The spacing of newly loading goods, loading temperature, and loading quantity were numerically studied for temperature stability of goods in Fluent. The non-uniformity coefficient of temperatures was introduced to evaluate the temperature variation of the cold storage. Simulation results show that there exist suitable loading temperature and loading quantity affecting least on the apple storage environment with highest loading efficiency during the loading process in the actual operation and management; Increasing loading spacing can reduce the influence of the temperature field of existed goods, while the loading spacing is not the bigger the better. For the studied cold storage, the reasonable loading condition is proposed to be 3.0℃ for loading temperature, 0.5 m for the suitable loading spacing and less than 10 % for the loading quantity.(3) According to practical investigation on the operation mode of air cooler in automatically controlled cold storage, UDF program was written to consider the changing velocity of the air cooler. Operating patterns of air cooler with the temperature probe at different position and the influence of opening process on operating patterns of air cooler were simulated. The simulation results show that a reasonable temperature probe position should be in the upper zone of the goods. Comparing with the probe position at returning air outlet, the frequency of the air cooler reduced by 41.7 % and the door opening would not affect the operating patterns of air cooler.(4) Studying intermittent operation strategy of air cooler in different seasons. Because of the different storage requirements of different goods, and the variation of heat load from store envelope in different seasons, a reasonable intermittent operation strategy should be developed concerning different storage requirements of different goods in different seasons. The temperature fluctuations of goods were analyzed when the air cooler is off. New intermittent operation strategy are proposed by TPI.