Study On The Airflow And Heat Transfer Characteristics In A Tall Space Cold Storage For Pepper With Fiber Air Dispersion System

In recent years,with the continuous development of the logistics industry,cold storage has achieved rapid development and growth in scale and quantity.The problems of the development and management in cold storage have become increasingly prominent in China.The airflow organization characteristics in the cold storage directly affect the storage environment of the cargo,which determine the storage quality and economic benefits Reasonable airflow organization can not only improve the air circulation in the cold storage,but also the uniformity of temperature distribution.It can reduce the operating energy consumption of the cold storage while maintaining the storage quality of the cargo and prolonging the storage time.The fiber air dispersion system is a low-temperature air supply technology developed on the basis of the traditional uniform air supply mode.It combines the advantages of uniform air supply and sufficient heat transfer of the fiber air dispersion system to create a low speed and uniform airflow organization environment.In this paper,a pepper cold storage in Hancheng City was taken as the research object.The CFD numerical simulation technology was used to study the airflow characteristics in the airflow in the air distribution mode of the fiber air dispersion system.The main research work of this paper is as follows:Based on the actual building profile of a pepper cold storage in Hancheng,a threedimensional coupled computational model for a fan-fiber air dispersion system-cargo-air environment was established.The grid-independent analysis and verification were carried out to study the influence of natural convection on the total heat transfer in the cold storage,and the distribution of velocity and temperature fields in the cold storage were analyzed.Then the air supply mode of the fiber air dispersion system suitable for the cold storage is explored to improve the uniformity of the velocity field and temperature field in the cold storage.For studying the airflow characteristics with semi-circular fiber air dispersion system,the heat transfer mechanism of air to cargo was studied.Then the average velocity and average temperature of cold air and its distribution characteristics were discussed.The temperature change of the cargo and the most unfavorable area in the cold storage was determined.Finally,the energy utilization coefficient of the cold storage was investigated.The result shown that the energy utilization coefficient was less than 1 for about 6% of the cold storage space,which needs to be further improved.After changing the semicircular fiber duct to a quarter round duct,the average velocity and average air-temperature were firstly studied.Then the temperature changes in cargo area and the improvement of energy utilization efficient in cold storage were discussed.The study found that the temperature in most areas decreased,and so do the temperature non-uniformity coefficient in the far-distance area from the air-chiller.Moreover,the energy utilization coefficient in the entire cold storage was improved after optimization.The minimum energy utilization coefficient was increased from 0.94 to 1.04.However,after optimization,the non-uniformity coefficient of the velocity at both ends in the longitudinal direction of the air zone is increased.This paper proposes an improved scheme of airflow distribution that can reduce the temperature unevenness coefficient of the cargo and improve the energy utilization efficient in the cold storage.The heat exchange mechanism of the cold air and cargo is also described.The research results have theoretical guiding significance for the application of fiber air dispersion system in high space cold storage.