Core Tip: To control and reduce the operating cost of cold storage, evaporation pressure and temperature and condensation pressure and temperature of refrigeration system are the main parameters. It is an important basis for operation and adjustment. According to the actual conditions and system changes, the operating parameters are constantly adjusted and controlled to make them run under economic and reasonable parameters, which can ensure the safety of machinery and equipment and stored products, give full play to equipment efficiency, and save water, electricity and oil.To control and reduce the operating cost of cold storage, evaporation pressure and temperature and condensation pressure and temperature of refrigeration system are the main parameters. It is an important basis for operation and adjustment. According to the actual conditions and system changes, the operating parameters are constantly adjusted and controlled to make them run under economic and reasonable parameters, which can ensure the safety of machinery and equipment and stored products, give full play to equipment efficiency, and save water, electricity and oil.A. If the temperature difference between evaporation temperature and warehouse temperature increases, the evaporation temperature will be too low, which will lead to the decrease of refrigeration coefficient and the increase of energy consumption. It is estimated that when other conditions remain unchanged, when the evaporation temperature decreases by 1℃, it will consume 1~2% more power. In addition, with the increase of temperature difference, the dehumidification capacity of the air cooler will increase and the humidity of the warehouse will decrease, which will lead to the increase of dry consumption and the decline of food quality.B. Evaporation temperature commonly used in China. The difference between evaporation temperature and warehouse temperature is generally 10℃, the evaporation temperature of fruit and vegetable cold storage is generally designed to be around -1010℃, the freezing room is around -28℃, and the freezing room is around -33℃. In actual operation, the temperature difference of many fruit and vegetable storage rooms is around 15℃, while in economically developed countries such as Europe, the difference between evaporation temperature and warehouse temperature is generally 3~5℃.C, causes of evaporation temperature is too low and solutions(1) (air cooler) is too smallThere are problems in the design, or the actual storage varieties are different from those in the design plan, and the heat load increases. For example, the cold storage where apples are to be stored is used to store garlic shoots. Because the harvesting period of garlic shoots in a production area is only a few days, it is impossible to achieve the daily purchase volume of apples as 5%-15% of the storage capacity, but it will be full in 3-5 days. Therefore, if the temperature is to be reduced to suitable storage in time,The evaporation area of the evaporator should be increased or the evaporator should be replaced.(2) the compressor cooling capacity is too largeAfter the warehouse load was reduced, the energy of the compressor was not reduced in time. The compressor of cold storage is matched according to the heavy load of refrigeration system, while the heavy load of fruit and vegetable cold storage occurs in the stage of goods storage, and most of the time, the load of compressor is less than 50%. When the storage temperature drops to the suitable storage temperature, the system load is greatly reduced. For example, if a larger machine is still turned on, a large horse-drawn cart will be formed, and the temperature difference will increase and the power consumption will increase.According to the change of warehouse load, the number of compressors should be reduced or the number of working cylinders should be reduced with energy adjustment devices.(3) The evaporator failed to defrost in time.Frosting on the evaporator coil reduces the heat transfer coefficient, increases the thermal resistance, reduces the heat transfer effect, and reduces the evaporation capacity. Under the condition of constant compressor energy, the evaporation pressure of the system will be reduced, and the corresponding evaporation temperature will be reduced, so it is necessary to defrost in time.(4) there is lubricating oil in the evaporatorThe lubricating oil in the evaporator will form a layer of oil on the wall of the evaporator coil, which will also reduce the heat transfer coefficient, increase the thermal resistance, reduce the heat transfer effect, and reduce the evaporation capacity of refrigerant, which will lead to the decrease of the evaporation pressure and the corresponding evaporation temperature of the system. Therefore, the system should be drained in time and the lubricating oil in the evaporator should be taken out by using hot ammonia defrosting.(5) Opening is too smallThe expansion valve is opened too small, and the liquid supply of the system is small. Under the condition of constant compressor energy, the evaporation pressure decreases, which leads to the decrease of evaporation temperature. The opening of expansion valve should be increased. Time, as soon as possible to stock fruit, get real benefits, to prevent the market from continuing to decline.