Introduction to Control Valves in Refrigeration Systems

Today, let's talk about three control valves in the refrigeration system, namely the evaporating pressure control valve, the condensing pressure control valve, and the suction pressure control valve. They can optimize the performance of the refrigeration system, and these valves are of great significance in the refrigeration system.

Now, let's discuss them one by one.

The evaporating pressure control valve is also known as the angle valve or back - pressure valve. It is installed in the suction line after the evaporator and is used to regulate one or more evaporators to maintain different minimum evaporating pressures. The evaporating pressure control valve is widely used in refrigeration and cold - storage systems, especially in parallel refrigeration units and multi - temperature cold storage with a single compressor.

As we all know, if the temperature of the cooled object in the refrigeration system needs to be maintained at a specified temperature, a relatively constant evaporating temperature is required, and the adjustment of the evaporating temperature is achieved through the adjustment of the evaporating pressure. When the load changes, the liquid supply of the expansion valve changes, which will cause fluctuations in the evaporating pressure. By installing an evaporating pressure control valve at the outlet of the evaporator, the evaporating pressure can be maintained stable.

The pressure change at the outlet end of the evaporating pressure control valve will not affect its opening degree because the pressure regulator is equipped with a balanced bellows. The evaporating pressure regulator has a pressure gauge interface for setting the required evaporating pressure.

When the cooling load decreases or the refrigeration capacity of the compressor increases due to a decrease in the condensing pressure, the refrigeration capacity of the compressor is excessive, which will inevitably cause the evaporating pressure to drop. With the installation of the evaporating pressure control valve, the valve automatically closes. Even if the suction pressure of the compressor drops, the evaporating pressure can still be maintained at the set value. The valve will not open again until the evaporating pressure rises above the set pressure.

The condensing pressure control valve is generally installed on the cooling water pipeline of the condenser and adjusts the flow rate of the cooling water according to the change of the condensing pressure. It adjusts the opening degree of the valve by directly sensing the pressure change of the refrigerant cycle, so that an adequate amount of cooling water can flow through, thus saving cooling water. In areas where the ambient temperature changes drastically, this system can solve many condenser control problems because it can suppress pressure changes and prevent problems from occurring.

When the condensing pressure of the refrigeration system rises, the condensing pressure valve will automatically open wider, allowing more cooling water to enter the condenser and accelerating the condensation speed of the refrigerant. Conversely, when the condensing pressure drops, the condensing pressure valve will automatically close smaller, reducing the amount of cooling water entering the condenser, thus keeping the condensing pressure within a certain range.

The condensing pressure control valve can be used together with the differential - pressure valve. Under the action of the internal spring force, the differential - pressure valve starts to open when the pressure difference reaches 1.4 bar and fully opens when it reaches 3 bar.

The larger the pressure difference of the valve, the larger its opening degree.

The differential - pressure valve is usually used in the hot gas pipeline between the exhaust pipeline and the receiver, aiming to maintain the pressure of the receiver at a certain level.

The suction pressure control valve, also known as the crankcase pressure control valve, is installed on the suction pipe of the compressor. The suction pressure control valve is an automatic valve set between the outlet of the evaporator and the inlet of the compressor.

The suction pressure control valve has direct - acting type and combined type of pilot valve and main valve. The purpose of its adjustment is to avoid the compressor operating under high suction pressure.

It adjusts the vapor flow rate according to the outlet pressure to prevent the suction pressure at the inlet of the compressor from exceeding the specified value, and it is a product used to prevent the motor driving the compressor from overloading.