Characteristics Of Humidity Distribution In A Controlled Atmosphere Store For Apples

It is well known that Controlled Atmosphere Storage has become one of the important means for fresh fruits in many developed countries. However,many of the factors may cause the fluctuations of humidity in a CA store,such as unreasonable design parameters,less tightness of store envelope,varied supply air temperature of air-cooler due to frost forming, improper humidification, or the unreasonable distribution of fruits. Whereas the relative humidity has a crucial role for fruit storage,which may cause fruit to wither or decay faster. Therefore,the study on characteristics of humidity distribution will be valuable to provide suitable atmosphere,and lower energy consumption for storage.The 3D physical and mathematical models were established for flow,heat and mass transfer inside a cold room of a CA Storage Technology Research Center for Apples. By combination of numerical simulation and experimental study,the humidity distribution was investigated under different O2 concentration,different parameters of air-cooler and humidifier.The main contents include:(1) Based on the survey of actual CA store,a geometric model of the object being studied was established. Further the characteristics of the airflow in empty CA Store was analyzed to provide theoretical guidance for a reasonable distribution of goods.(2) The humidity distribution at different O2 concentrations was studied and the results agreed well with the experimental results,which indicateds that the developed numerical model in this study is correct.(3) The influence of air-coller’s operating parameters was carride out on humidity distribution. The humidity distribution was simulated at the following air-cooler supply air velocities: 3 m/s,4 m/s,5 m/s and 6 m/s. The results show that with the increase of supply velocity,the air temperature decreases,whereas the change of relative humidity is not obvious. The supply air temperature has a significant impact on the humidity distribution. The relative humidity rises with lower supply air temperature. But the temperature should not be suggested to be too low,since too high humidity would make the fruits decay faster.(4) The influence of humidifier device was studied on the humidity distribution in CA Store. The inlet relative humidity also has a great impact on the humid distribution. The humidity gradient in cargo area is larger than that of gas zone. In conclusion,the suggestion was made for the supply air paramenters of the air-cooler are 273 K,5 m/s and air humidity is 95%. The research results would provid a reference for the design and operation management in CA store.