The Function, Structure And Principle of Three Pressure Regulating Valves in Refrigeration System

Today we talk about the refrigeration system of three control valves, they are: evaporative pressure control valve, condensing pressure control valve, suction pressure control valve. They can optimize the performance of the refrigeration system, in the refrigeration system these valves are of great significance.

Evaporative pressure control valve ：

evaporative pressure control valve alias: Angle Valve, back pressure valve. Installed in the suction line behind the evaporator, it is used for adjusting the minimum evaporating pressure containing one or more evaporators. The evaporative pressure regulating valve is widely used in the refrigeration system, especially in the parallel refrigerating unit and the multi-temperature cold storage.If the temperature of the cooled object in the refrigeration system needs to be maintained at a specified temperature, it must have a more constant evaporating temperature, and the evaporating temperature is regulated by the evaporating pressure. When the load changes, the liquid supply of the expansion valve changes, which will cause the fluctuation of evaporation pressure.The pressure change at the outlet of the evaporative pressure regulator does not affect the opening and closing degree because the pressure regulator is equipped with an equalizing bellows and the evaporative pressure regulator has a pressure gauge interface for setting the required evaporative pressure

Internal working principle of evaporative pressure regulating valve

When the cooling load is reduced, or because the condensing pressure is reduced and the refrigeration capacity of the compressor increases, due to the excess refrigeration capacity of the compressor, the evaporation pressure must be reduced. Install the evaporation pressure control valve, the valve automatically closed, compressor suction pressure even down, but also to maintain the evaporation pressure in the set value. The valve does not open again until the evaporation pressure is re-raised above the set pressure. The function of evaporative pressure regulating valve can be summarized as follows:

1.Ensure the constant evaporation temperature, reduce the fluctuation of storage temperature. 

2.To prevent the evaporation pressure is too low, when the evaporation pressure below the set value of the valve closed. 

3.When a machine has more than one storehouse, it can make evaporators in different storehouse temperature run under different evaporating pressure.

Condensing pressure control valve 

Condensing pressure control valve is generally installed in the condenser cooling water line, according to the change of condensing pressure to regulate the flow of cooling water. It adjusts the valve opening by directly sensing a change in pressure in the refrigerant cycle to allow enough cooling water to flow through, thereby saving cooling water. The system can solve many condenser control problems in areas where ambient temperature changes are severe, because it can suppress pressure changes and thus prevent problems. When the condensing pressure of the refrigeration system increases, the condensing pressure valve will automatically open up, so that more cooling water into the condenser, accelerating the rate of refrigerant condensation; conversely, when the condensing pressure drops, the condensing pressure valve will automatically close small, so that the amount of cooling water entering the condenser is reduced, thus, the condensing pressure is maintained in a certain range.

Condensing pressure regulator can be used with the differential valve, under the action of internal spring force, the differential valve in the differential pressure reached 1.4 bar began to open, reached 3bar when fully open. The greater the pressure difference of the valve, the greater the opening and closing degree.The differential pressure valve is usually used in the hot gas line between the exhaust pipe and the liquid reservoir in order to maintain the liquid reservoir pressure at a certain level.

Suction pressure control valve 

Suction pressure control valve alias: crankcase pressure control valve, installed in the compressor suction pipe above. The suction pressure regulating valve is an automatic valve arranged between the evaporator outlet and the compressor inlet.The suction pressure regulating valve has the direct-acting type and the guide valve and the main valve combination type. It is adjusted to avoid the compressor in high suction pressure under operation, it according to the outlet pressure to adjust the steam flow, so as to avoid the compressor inlet suction pressure exceeds the specified value, a product designed to prevent overload of the motor that drives the compressor.