How to Control the Condensing Pressure of the Chiller?

2022/08/15 ClassificationNouvelles de l'industrie 239

How to Control the Condensing Pressure of the Chiller?

During the operation of the chiller, when the load changes, the temperature and flow rate of the cooling medium, air or water in the condenser of the chiller change, which will cause the condensing pressure (P) to change. When P increases, the suction of the refrigeration cycle will change. The exhaust pressure ratio increases, the exhaust temperature rises, the cooling capacity decreases, and the performance coefficient decreases, and it also causes the compressor to increase labor consumption and even cause the motor to overload. Therefore, it is necessary to control the condensing pressure of the chiller.

The condenser pressure control of the chiller is mainly realized by adjusting the heat exchange capacity of the condenser.

When the equipment is running in summer, it is beneficial to adjust the condensing pressure to be lower, which is beneficial to the cycle characteristics and the work of the compressor. But in winter operation, if the condensing pressure is too low, there will be some problems. For systems that use expansion valves for liquid supply, the flow capacity of the expansion valve is a function of the pressure difference before and after the valve. If the pressure is too low, the pressure difference before and after the expansion valve is too small, and the liquid supply power is insufficient, so that enough refrigerant liquid cannot be supplied to the evaporator. If the infusion pipeline from the condenser to the expansion valve passes through a warm room or stands upright, the refrigerant is easily vaporized in the liquid pipeline due to static pressure or heat transfer loss, and the vaporization of the liquid before the valve also seriously affects the capacity of the expansion valve. cause insufficient fluid supply.

If the cooling flow of the bench-type chiller is too low, it will not only affect the cooling capacity of the chiller refrigeration unit, but also make it difficult for the system to return oil, hindering the normal operation of the chiller. For the device using hot gas defrosting, if the condensing pressure is too low, the exhaust temperature will be low, so that the hot gas defrosting cannot be carried out effectively. For the device with low pressure control compressor on or off, the condensing pressure is too low, and the suction side pressure cannot reach When the low-pressure start-up control value is used, the compressor cannot be started normally. The condensing pressure is very low in the cold winter season every year, and if it is not controlled, the above troubles are likely to occur. This is especially important for refrigeration units with a certain annual load in the manufacturing sector.

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