What Causes the Evaporation Temperature in a Cold Storage Refrigeration System to Be Too Low?

(1) The evaporator (cooling fan) is too small. There are problems in the design, or the actual stored variety is different from the designed planned stored variety, increasing the heat load. For example, if a cold storage designed to store apples is used to store garlic sprouts.

Since the harvesting period of garlic sprouts in one production area is only a few days, it is impossible to have the daily intake volume account for 5% - 15% of the storage capacity as in the case of apples. Instead, the storage needs to be filled within 3 - 5 days. Therefore, to reduce the temperature to the appropriate storage temperature in a timely manner, it can only be achieved by lowering the evaporation temperature. The evaporation area of the evaporator should be increased or the evaporator should be replaced.

(2) The refrigerating capacity of the compressor is too large. After the load of the storage room decreases, the energy of the compressor is not reduced in a timely manner. The compressor of the cold storage is matched according to the maximum load of the refrigeration system. The maximum load of a fruit and vegetable cold storage occurs during the goods - entering stage. Most of the other time, the load of the compressor is less than 50%. After the goods - entering is completed and the temperature drops to the appropriate storage temperature, the system load is greatly reduced. If a large - capacity machine is still running, it is like using a big horse to pull a small cart, increasing the temperature difference and power consumption. According to the change of the storage room load, the number of running compressors should be reduced or an energy - regulating device should be used to reduce the number of working cylinders.

(3) The evaporator is not defrosted in a timely manner. Frost on the evaporator coil reduces its heat - transfer coefficient, increases the thermal resistance, reduces the heat - transfer effect, and decreases the refrigerant evaporation amount. With the constant energy of the compressor, it will lead to a decrease in the evaporation pressure of the system, and correspondingly, the evaporation temperature decreases. So, defrosting should be carried out in a timely manner.

(4) There is lubricating oil in the evaporator. The lubricating oil in the evaporator will form an oil film on the wall of the evaporation coil, which also reduces the heat - transfer coefficient, increases the thermal resistance, reduces the heat - transfer effect, and decreases the refrigerant evaporation amount, resulting in a decrease in the evaporation pressure of the system and a corresponding decrease in the evaporation temperature. Therefore, the system should be drained of oil in a timely manner, and hot ammonia defrosting should be used to remove the lubricating oil in the evaporator.

(5) The expansion valve is opened too small. When the expansion valve is opened too small, the liquid supply to the system is insufficient. With the constant energy of the compressor, the evaporation pressure decreases, leading to a decrease in the evaporation temperature.