The most popular technology to reduce the operatio

2022-08-01
  • Detail

Relevant technologies to reduce the operating cost of cold storage control and reduce the operating cost of cold storage. In the operation management of machinery and equipment, we should focus on "oil, fluorine, water and electricity"; In the warehouse management, the "ice, frost, water, doors and lights" shall be strictly controlled; In quality management, advanced processes and technologies are adopted to improve product quality. How to reduce the operating cost of cold storage

(I) reasonably adjust the operating parameters of the refrigeration system to improve the equipment efficiency

evaporation pressure and temperature of refrigeration system and condensation pressure and temperature 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 continuously adjusted and controlled to make them operate under economic and reasonable parameters, which can ensure the safety of machinery, equipment and stored products, give full play to equipment efficiency, and save water, electricity, oil, etc

1. Prevent the evaporation temperature from being too low

a. if the temperature difference between the evaporation temperature and the warehouse temperature increases, the evaporation temperature will be too low, which will reduce the refrigeration coefficient and increase the energy consumption. It is estimated that when the evaporation temperature decreases by 1 ℃, 1~2% more power will be consumed under other conditions unchanged. 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 increase the dry consumption of food and reduce the quality of food

b. evaporation temperature commonly used in China. The difference between the evaporation temperature and the warehouse temperature is generally 10 ℃. The evaporation temperature of the fruit and vegetable cold storage is generally designed to be about -1010 ℃, the freezing room is -28 ℃, and the freezing room is -33 ℃. In actual operation, the temperature difference of many fruit and vegetable storage warehouses is about 15 ℃, while in Europe and other economically developed countries, the difference between the evaporation temperature and the warehouse temperature is generally 3~5 ℃

c. causes of low evaporation temperature and solutions

(1) the evaporator (cooling fan) is too small

there is a problem in the design, or the actual storage varieties are different from the designed storage varieties, and the heat load increases. For example, the cold storage to store apples is used to store garlic sprouts. Because the garlic sprouts in a production area only have a few days to harvest, it is impossible to achieve the same daily purchase volume as apples by 5%-15% of the storage capacity, However, it will be full in 3~5 days. Therefore, if the temperature is to be reduced to the appropriate storage temperature in time, it can only be achieved by reducing the evaporation temperature

the evaporation area of the evaporator should be increased or the evaporator should be replaced

(2) the cooling capacity of the compressor is too large

after the warehouse load is reduced, the energy of the compressor is not reduced in time. The compressor of the cold storage is matched according to the maximum load of the refrigeration system, while the maximum load of the fruit and vegetable cold storage occurs at the stage of goods warehousing, and the other 2 According to the test environment, it can be divided into: room temperature fatigue test, low temperature fatigue test, high temperature fatigue test, thermal fatigue test, corrosion fatigue test, contact fatigue but not everyone can use the fatigue test, fretting wear fatigue test, etc. most of the time, the load of the compressor is less than 50%. When the temperature at the end of warehousing is reduced to the appropriate storage temperature, the system load will be greatly reduced. If a larger machine is still started, a big horse pulling a small car will be formed. The temperature difference will increase and the power consumption will increase

the number of compressors to be started shall be reduced according to the change of warehouse load or the number of working cylinders shall be reduced by using energy regulating devices

(3) the evaporator is not defrosted in time

the frosting of the evaporator coil reduces its heat transfer coefficient, increases the thermal resistance, reduces the heat transfer effect, and reduces the evaporation capacity of the refrigerant. Under the condition that the compressor energy remains unchanged, the evaporation pressure of the system will be reduced, and the corresponding evaporation temperature will be reduced. Therefore, it is necessary to defrost in time

(4) there is lubricating oil in the evaporator

the lubricating oil in the evaporator will form an oil film on the pipe wall of the evaporation coil, which will also reduce the heat transfer coefficient, increase the thermal resistance, reduce the heat transfer effect, reduce the evaporation capacity of the refrigerant, reduce the evaporation pressure of the system, and reduce the corresponding evaporation temperature. Therefore, the system should be drained in time, and the lubricating oil in the evaporator should be brought out by hot ammonia defrosting

(5) the opening of expansion valve is too small

the opening of expansion valve is too small, and the liquid supply of the system is small. Under the condition that the compressor energy remains unchanged, the evaporation pressure decreases, resulting in the reduction of evaporation temperature. The opening of expansion valve shall be increased

2. Prevent the condensation pressure from being too high

the increase of condensation pressure will lead to the increase of compression function, the decrease of refrigeration capacity, the decrease of refrigeration coefficient and the increase of energy consumption. It is estimated that when other conditions remain unchanged, the power consumption will increase by about 3% when the condensation temperature corresponding to the condensation pressure increases by 1 ℃. It is generally considered that the economic and reasonable condensation temperature is 3~5 ℃ higher than the outlet temperature of cooling water. Causes of condenser pressure rise and solutions:

(1) the condenser is too small. Replace or add condenser

(2) few condensers are put into operation. Increase the number of operating units

(3) insufficient cooling water flow. Increase the number of running water pumps and increase the water flow

(4) the cooling water temperature is too high. Supplement low-temperature water (tap water or well water); Use frost flushing water; To ensure the cooling effect of the cooling tower, the cooling tower is installed outdoors. Due to the function of the fan, a large amount of dust, leaves, insects, etc. will enter the tower, and the cooling tower packing, pipes, etc. will be blocked after a long time. In addition, after a long time of use, the spray hole of the water distributor will also be blocked by sundries or scale, affecting the cooling effect. Therefore, the cooling tower needs to be cleaned regularly and kept clean. When the water temperature is close to the air wet bulb temperature, the cooling tower fan shall be shut down to reduce power consumption

(5) the heat exchange area of condenser decreases. Sufficient heat exchange area is an important guarantee for the heat exchange effect of condenser. In particular, the refrigeration system of the compressor condensing unit is adopted, because the condenser of this unit also has the function of liquid reservoir. When the liquid level in the condenser is too high, the condensing effect of the condenser will be seriously affected, the condensing temperature and pressure will rise, and the power consumption of the refrigeration compressor will increase. Therefore, during operation, attention should be paid to the change of liquid level, the condensed liquid in the condenser should be discharged in time, and the amount of refrigerant should be strictly controlled when filling refrigerant, Ensure sufficient heat exchange area of condenser

(6) uneven water distribution of condenser. When the water distribution is uneven, the water flow in some tubes is the largest, and the water flow in some tubes is small, which will reduce the heat transfer efficiency and increase the condensation temperature. Good water flow distribution should be that the water flows down along the pipe wall. If the water flows down from the middle of the pipe, most of the water will not have the effect of condensation. Therefore, when the water distribution of the water distributor is uneven, the water distributor should be replaced

(7) there is scale on the condenser pipe. The scale on the condenser pipe increases the thermal resistance, reduces the heat transfer coefficient, reduces the heat exchange effect, and increases the condensation temperature. Improve water quality and remove scale in time

(8) there is air in the condenser. The air in the condenser will increase the partial pressure and total pressure in the system, and the air will also form a gas layer on the surface of the condenser, resulting in additional thermal resistance, which will reduce the heat transfer efficiency and increase the condensation pressure and temperature. Air shall be released in time

3. Prevent excessive exhaust temperature

excessive exhaust temperature will worsen the lubrication of the compressor, increase friction and increase energy consumption; At the same time, too high exhaust temperature will also enhance the heat exchange between refrigerant gas and cylinder wall, resulting in the decrease of compressor efficiency. Causes of excessive exhaust temperature and solutions:

(1) poor cooling of compressor cylinder. Increase cooling water and improve cooling conditions

(2) if the suction superheat of the compressor is too large, improve the insulation of the suction pipe or increase the liquid supply of the evaporator

(3) the suction pressure is too low. The solution is the same as "preventing too low evaporation temperature"

(4) the condensation pressure is too high. The solution is the same as "prevent excessive condensation pressure"

(II) prevent impurities from entering the refrigeration system

the refrigeration system is a sealed circulating system. The refrigerant circulating in the system is required to be clean and free of impurities, but it is impossible to be completely clean in actual operation. This is related to the working conditions and that the refrigerant added to the system is not clean enough. Impurities include lubricating oil, air, water, etc. these impurities entering the refrigeration system are very unfavorable to the operation of the refrigeration device and should be eliminated in time

1. After the lubricating oil

enters the system, due to the high viscosity of the oil, it is easy to mix dirt and mechanical impurities into colloidal substances. When it accumulates in the pipeline or valve with small section, it is easy to be blocked; The thermal conductivity of oil is much smaller than that of metal. When it is attached to the wall of heat exchanger, the heat transfer will deteriorate, causing the condensation temperature to rise and the evaporation pressure to decrease, the exhaust temperature to rise, and the working efficiency to decrease. According to relevant information, there is 0.1mm oil film on the inner surface of the condenser, which will reduce the cooling capacity of the compressor by 16.6% and increase the power consumption by 12.4%. In order to avoid and reduce the oil entering the system, reduce the compressor exhaust temperature, correctly master the oil filling amount of the compressor, and regularly prevent oil from the equipment in a planned way during operation

2. Water

water entering the system will cause the evaporation temperature to rise. For the refrigeration system with ammonia as the refrigerant, the water contained in ammonia has a corrosive effect on zinc, copper, bronze and copper alloys (except phosphor bronze). For the refrigeration system with freon as refrigerant, freon contains water, which has corrosive effect on metals (the allowable content is 0.0025%); Since Freon is slightly dissolved in water, it is also easy to cause ice jam at the expansion valve, etc. Ways for water to enter the system and preventive measures:

(1) the air is not evacuated or not completely evacuated during installation or maintenance. Evacuate the air during installation or maintenance, and install the dryer

(2) enter from unsealed place. Do not have leakage points and avoid negative pressure operation

(3) there is water in oil or refrigerant. The moisture content of the added oil or refrigerant shall be strictly controlled. In addition, since the oil absorbs water, the long-term open oil storage container will absorb moisture, and the oil barrel shall be closed

3. Air

when air enters the system, the pressure of condensate in the system will increase, the total pressure will increase, and the air will form a gas layer on the surface of the condenser, resulting in additional thermal resistance, which will reduce the heat transfer efficiency, resulting in the increase of condensation pressure and condensation temperature. The power consumption will increase by about% when the condensation pressure is 1kg/cm2 per liter. In addition, the adiabatic index of air (k=1.41) lies in the adiabatic index of refrigerant (ammonia k=1.28, freon 12k=1.13, freon 22k=1.18), which causes the exhaust temperature to rise, so air should be released in time.

(III) dirt and frost on the heat exchange equipment should be removed in time to improve the heat transfer efficiency of the heat exchange equipment

1 Timely remove the frosting on the evaporator, which makes the growing ceramic and aluminum new material enterprises such as Anhui Xiangbang composite materials Co., Ltd. continue to grow. When the evaporator works for a period of time, it will form a frost layer on the coil, or even form ice. Because the heat transfer system of the frost (which will significantly increase the ice production rate by 1.9kcal/mh ℃) is much smaller than the heat transfer coefficient of steel or copper, the frost on the evaporator coil will increase the heat transfer resistance, Reduce the heat transfer effect, affect the cooling speed, increase the startup time, and increase the power consumption. Therefore, defrost in time according to the frosting condition of the evaporator

2. Timely remove the scale on the condenser

in the cooling system of water-cooled condenser, due to the mineral content in the water and the heating effect, the condenser will form scale and sediment after running for a certain period of time. Because the thermal conductivity of the scale is very small (about 0.2kcal/mh ℃), the heat transfer heat shade of the condenser tube wall increases and the condensation effect of the condenser deteriorates. According to statistics, the 1.5mm scale on the water side surface of the condenser will increase the condensation temperature by 2.8 ℃ and increase the power consumption of the refrigeration device by about 9%. Additional knot

Copyright © 2011 JIN SHI