I. Refrigeration System

The piston type single stage compression refrigeration system is mostly used in the refrigeration equipment of air conditioned storage. Ammonia or Freon-22 is used as refrigerant. The cooling mode in the storage can be either direct evaporation cooling of refrigerant or indirect cooling of intermediate refrigerant. The latter is more effective than the former in air conditioned storage. Because the intermediate refrigerant is more convenient to control the temperature of the liquid supplied to the air cooler, it is only necessary to install a reflux stroke control three-way valve on the liquid supply pipeline to meet the requirements of different temperatures in different warehouses at the same time.

In order to reduce the dry consumption of the goods stored in the warehouse, the good performance of the air-conditioned warehouse requires the difference of heat transfer temperature between 2 and 3 degrees, that is to say, the difference of evaporation temperature and storage temperature between 2 and 3 degrees, which is much smaller than that of the ordinary cold storage. Only by controlling and reaching the small difference between evaporation temperature and storage temperature, can the frosting of evaporator be reduced and the required high relative humidity be maintained in the reservoir. Therefore, in the design of air-conditioned storage, under the same conditions, the heat transfer area of the air-conditioned storage fan is larger than that of the ordinary fruit and vegetable cold storage fan. That is to say, the so-called "large evaporation area and low heat transfer temperature difference" scheme is adopted in the design of air-conditioned storage cold fan.

II. Configuration of Temperature Sensors

During the operation of a well-designed controlled atmosphere reservoir, the temperature difference within the reservoir can be less than 0.5 C. Therefore, it is necessary to select an electronic temperature controller with accuracy greater than 0.2 C to control the storage temperature. The number and location of temperature sensors are also very important for the good control of the temperature in the air conditioned storage. The minimum recommended number of probes is: 3 in storage of 50 tons or less, 4 in storage of 100 tons and 5 or 6 in larger storage. One of the probes is used to monitor the air temperature of free circulation in storage. For ceiling type air coolers, the probes should be installed in the space between the entrance of cargo and air cooler. The remaining probes are placed at different positions of fruits and vegetables to measure the actual temperature of fruits and vegetables.

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