Study On Influencing Factors On Gas Environment And Ventilation Control Strategy In Apple Cold Storage

The gas composition and its concentration distribution in the cold storage are important factors influencing the quality of fruit and vegetable storage.Ventilation is the key process to ensure the reasonable gas environment in the cold storage.The high concentration of CO2 and C2H4 during the storage will affect the edible and commercial value of fruits and vegetables.The arbitrary nature of human operation during the actual ventilation process,lead the unsatisfactory ventilation effect and unnecessary energy consumption.Therefore,it is important to study the distribution of CO2 and C2H4 in the cold storage of apple and the influencing factors during ventilation process.It has important academic significance and engineering application value to explore the form mechanism of gas environment and the develop strategy of ventilation.It also provides some reference value for the study of ventilation mechanism of other types of fruit and vegetable storage.In this paper,the release rule of ethylene from apple was studied by gas chromatography,and a three-dimensional mathematical model of gas flow and heat and mass transfer in the reservoir was established.Based on the numerical simulation,the distribution of gas components in cold storage and the operation mode of different air cooler,the exhaust speed and the setting of air outlet on the distribution of CO2 and C2H4 in the reservoir were obtained.The main research work was as follows:(1)The release rule of ethylene from apple was studied by gas chromatography,and the release of ethylene from apple was higher.Therefore,the apple should be concerned with the content of ethylene in the storage process and take reasonable ventilation.(2)Through compile the UDF program to solved the two complex issues which due to the changed of gas concentration of storage environment result to the changed of apple's respiratory strength and CO2 and C2H4 mass fraction of cooling fan outlet and proved the rationalization of this method by experimental measurement.The experimental results of ethylene concentration at the measuring point were compared with the simulated value.The gas zone and the cargo area C2H4 concentration deviation of 19.7% and 15.1%,respectively,in the simulation study acceptable range,it can be more accurate description of the gas concentration changes in the library.(3)The distribution of CO2 and C2H4 in storage environment was studied by CFD software.The results showed that the distribution of CO2 and C2H4 in the cargo area and gas area of the storage area was uniform after 24 h storage,but the concentration was high,the concentration of carbon dioxide in the cargo area was 2.8%,and the ethylene concentration exceeded 15 ppm,which out of apple frozen storage requirements.Indicating the respiration and biochemical had more effects for early storage of apple.(4)Based on the influencing factors of ventilation process,studying the effects on the start and stop of air cooler,the exhaust velocity and the setting of air outlet on the distribution of gas concentration in the air.The results show that the airflow in the reservoir is enhanced when the air cooler are turned on.The ventilation performance is deteriorated.Therefore,the air cooler should be closed when ventilated.With the increase of the exhaust speed,the mass transfer effect of the airflow in the reservoir is enhanced,the storage environment is improved,the ventilation effect is better,and there is a minimum exhaust speed,so that the harmful gas in the warehouse is reduced to the storage requirement within the stipulated time,The minimum exhaust speed is 8 m / s for the cold storage studied in this paper.The double-row fan form can improve the airflow in the reservoir so that more fresh air passes through the cargo area and can be more efficient and efficient than the single-row fan Reduce the concentration of harmful gases in the cargo area.