Working condition and adjustment of refrigeration system of low temperature chiller

Working condition and adjustment of refrigeration system of low temperature chiller Low-temperature chiller refrigeration system operating conditions and adjustments Nowadays, chillers are widely used in the refrigeration industry, and the refrigeration working fluid is usually R22 (also R404a) and so on. In order to facilitate operation and maintenance and reduce the installation location, the refrigeration compressor, oil separator, water-cooled shell and tube condenser, filter drier, solenoid valve and other components are usually installed on the same base to form a compression condensing unit. The reuse pipeline is connected to the evaporator through the expansion valve to form a complete refrigeration system. Normal operating conditions in the operation of the refrigeration system: 1. The suction temperature of the compressor should be 5-15℃ higher than the evaporation temperature 2. The exhaust temperature of the compressor R22 system shall not exceed 150℃ 3. The oil temperature of the compressor crankcase must not exceed 70℃ 4. The suction pressure of the compressor should correspond to the evaporation pressure; 5. The discharge pressure of the compressor R22 system must not exceed 1.8MPa 6. The oil pressure of the compressor is 0.12-0.3MPa higher than the suction pressure 7. Always pay attention to the amount of cooling water and water temperature. The outlet water temperature of the condenser should be 2-5℃ higher than the inlet water temperature. 8. Always pay attention to the oil level of the compressor crankcase and the oil return of the oil separator 9. The compressor should not have any knocking sound, and the heat of all parts of the body should be normal 10. The condensing pressure must not exceed the compressor discharge pressure range Adjustment of the operation of the refrigeration system: The expansion valve is one of the four major components of the refrigeration system. It is an important device for regulating and controlling the flow and pressure of the refrigerant into the evaporator. It is also the high and low pressure side; the dividing line;. Its adjustment is not only related to the normal operation of the entire refrigeration system, but also an important indicator of the operator's technical level; the adjustment of the expansion valve must be carried out carefully and patiently, and the adjustment pressure must pass through the evaporator heat exchange boiling (evaporation), and then It takes a time process to enter the suction chamber of the compressor through the pipeline to reflect on the pressure gauge. Every time the expansion valve is adjusted, it usually takes 10 to 15 minutes to stabilize the adjustment pressure of the expansion valve on the suction pressure gauge. The suction pressure of the compressor is an important reference parameter for the adjustment pressure of the expansion valve. The opening degree of the expansion valve is small, the flow rate of the refrigerant is less, and the pressure is low; the opening degree of the expansion valve is large, the flow rate of the refrigerant is more, and the pressure is also higher. According to the thermodynamic properties of the refrigerant, the lower the pressure, the lower the corresponding temperature; the higher the pressure, the higher the corresponding temperature. According to this law, if the outlet pressure of the expansion valve is too low, the corresponding evaporation pressure and temperature are also too low. However, due to the decrease in the flow rate into the evaporator and the decrease in pressure, the evaporation rate is slowed, the cooling capacity per unit volume (time) decreases, and the cooling efficiency decreases. On the contrary, if the outlet pressure of the expansion valve is too high, the corresponding evaporation pressure and temperature are also too high. The flow and pressure into the evaporator are increased. Due to excessive liquid evaporation, excessive moisture (even liquid) is sucked into the compressor, causing a wet stroke (liquid strike) of the compressor, which prevents the compressor from working properly, resulting in a series of work The condition is bad and even damages the compressor. From this perspective, correct adjustment of the expansion valve is particularly important for the operation of the system. In order to reduce the pressure and temperature loss after the expansion valve is adjusted, the expansion valve should be installed on the horizontal pipeline at the entrance as much as possible. The temperature sensor should be wrapped around the center of the side of the return air pipe (low pressure pipe). When the expansion valve is working normally, the valve body is slanted with frost, and there should be no frost on the inlet side, otherwise it should be regarded as an ice block or dirty block in the inlet filter. Under normal circumstances, the expansion valve is very quiet when it is working. If there is a more obvious rustle, it means that the refrigerant in the system is insufficient. The expansion valve should be replaced when it has malfunctions such as air leakage and adjustment failure of the temperature sensing system. The compressor discharge temperature is too high : 1. The suction pressure is too low, the suction and discharge pressure difference is too large (cylinder compression ratio is large), the opening degree of the expansion valve is small, and the adjustment pressure is low 2. The suction temperature is too high, that is, the suction is overheated, the suction pipe is too long or the heat preservation effect is poor
3. The amount of cooling water is insufficient or the water temperature is too high 4. Too much non-condensable gas (air) in the system 5. The condensing pressure is too high, the corresponding condensing temperature is also high, causing the exhaust temperature to rise 6. Malfunction of compressor cylinder or valve group The discharge pressure of the compressor is too high: 1. Too much non-condensable gas (air) in the system 2. The amount of cooling water is insufficient or the water temperature is too high 3. The condenser is too dirty and too much scaling 4. Too much refrigerant in the system 5. The oil temperature of the compressor is too high: 1. The suction and discharge temperature of the compressor is too high 2. The lubricating oil is too dirty or the oil quality is too bad 3. The compressor parts are severely worn Condensation pressure and condensation temperature are too high: 1. The condenser cooling water is insufficient or the water temperature is too high 2. The condenser is too dirty and too much scaling 3. Too much non-condensable gas (air) in the system 4. Too much refrigerant in the system 5. The heat transfer area configuration of the condenser is too small