Research On The Uniformity Of Air Flow Field And Heat And Moisture Transfer Property Of Palisade Structure In Cold Storage

Cold storage is the most important facility in cold chain logistics of fruit and vegetable, and the preservation quality and energy consumption during the cold storage’s operation are major concerns. The uneven and unstable temperature and humidity will reduce the preservation quality of fruit and vegetable. The heat and moisture transfer property of closure structure has a great influence on the operation energy consumption. Thus, the research on the uniformity and stability of thermal field and heat and moisture transfer property of palisade structure in cold storage is essential to improve the preservation quality of fruit and vegetable and reduce energy consumption.In this paper, the author chose a cold storage for apples as a research object. By combination of numerical simulation and theoretical analysis, the uniformity and stability of temperature and humidity fields and heat and moisture transfer property of palisade structure in cold storage were studied. The main work and results are as follows:(1) Comparative study were carried out on the characteristics of air distribution in cold storage with and without uniform air supply duct. A physical and numerical models for flow, heat and mass transfer inside the cold storage was developed. When the uniform air supply duct was installed in the cold storage, the non-uniformity coefficient of temperature was 20% lower than the cold storage without uniform air supply duct, and the non-uniformity coefficient of relative humidity had decreased by 22.73%, while the value of ADPI had increased by 11.13%.(2) The closure structure dynamic cooling load during storage of fruit and vegetable was calculated with a typical meteorological year data. There has a great fluctuation of cooling load during storage of fruit and vegetable, and the variation was about 1.12 times of the maximum value. The dynamic cooling load has a great influence on the energy consumption so that we can reduce energy consumption of cold storage by frequency control of air-cooler.(3) This paper theoretical analyzed the unsteady heat transfer process of the palisade structure in cold storage. When the outdoor air temperature cyclical changes, different insulation materials will result in different fluctuation of inside wall surface temperature. When extruded polystyrene board was applied as insulation material, the fluctuation of inside wall surface temperature was 44.59% lower than the polyvinyl chloride applied. The larger the thermal inertia index and heat resistance of insulation material, the better the stability of temperature field in cold storage.(4) Theoretical analyzed were carried out on the influences of outdoor meteorological parameter on condensation phenomenon in external wall under different insulation ways. Furthermore the relationship of critical vapor barrier thickness along outdoor meteorological parameter was explored. The results show that the external wall of cold storage using interior insulation was more likely to avoid condensation under the same outdoor meteorological parameter, and for different regions we can adopt different insulation ways(interior insulation or external insulation). The alignment chart which is used to solve the critical vapor barrier thickness of external wall of cold storage in different regions has been obtained.