What to Do When the Condensing Pressure of the Cold Storage Is Too Low in Winter?

First, we need to understand two concepts: condensing temperature and condensing pressure. The condensing temperature refers to the saturation temperature at which the refrigerant vapor in the condenser condenses under a certain pressure. The condensing temperature is not equal to the temperature of the cooling medium, and there is also a heat transfer temperature difference between them.

The condensing pressure refers to the pressure at which the refrigerant condenses from a gas to a liquid in the condenser. Since the pressure inside the condenser in the refrigeration system cannot be measured, and in fact, the pressure drop of the refrigerant in the exhaust pipe and the condenser is very small, whether in design or commissioning, the exhaust pressure is often approximated to the condensing pressure.

During the operation of the refrigeration device, the condensing pressure has a great influence on the system performance. When the condensing pressure (or condensing temperature) is high, the compression ratio increases, the volumetric efficiency decreases, the refrigeration capacity decreases, and the power consumption increases. The exhaust temperature rises, and the higher the condensing pressure, the greater the degree of its adverse effects. The phenomenon of high condensing pressure mainly occurs in summer, and at this time, the condensing pressure should be reduced as much as possible to ensure the economy and reliability of the system operation.

However, for refrigeration devices that operate throughout the year, such as air conditioning machine rooms, refrigeration and cold storage (cold storage) and other equipment, the phenomenon of too low condensing pressure may occur during winter operation. When the condensing pressure is too low, the pressure difference before and after the expansion valve is too small, and the capacity of the expansion valve decreases, resulting in insufficient liquid supply capacity. The evaporator is short of liquid, and the refrigeration capacity of the system drops significantly, thus causing faults in the refrigeration system.

Therefore, the condensing pressure must be controlled within a reasonable range, otherwise, it will cause frequent low-pressure alarms or low-suction-pressure alarms and other faults in the refrigeration device.

In the refrigeration system, if the condenser is installed outdoors, the exhaust pressure (condensing pressure) of the system is often relatively low in winter (or in a low-temperature environment). This situation is more common in the north, and it also exists for air conditioners as well as other equipment (such as cold storage);

Too low a condensing pressure will make it impossible for the expansion valve to obtain a sufficient pressure drop at both ends, and it is difficult to provide an appropriate amount of refrigerant to the evaporator. On the one hand, the refrigeration capacity of the system cannot meet the requirements, and on the other hand, it will also cause frequent low-pressure alarms and other faults in the system.

The methods for adjusting the condensing pressure vary for different condensers. The following are several methods to increase the condensing pressure at low temperatures: