Precautions for the Hot Gas Bypass Valve of Refrigeration Units in Cold Storage

Hot gas bypass is used in small refrigeration units for capacity regulation. The hot gas bypass valve needs to be added. The high-pressure exhaust gas passes through the bypass valve and drops to near the evaporating pressure, and then mixes with the throttled liquid before entering the evaporator for evaporation. In this way, the unit refrigeration capacity is reduced, which can meet the capacity regulation requirements of small compressors. Liquid injection cooling is used to reduce the discharge temperature in systems with relatively low evaporating temperatures. There is no inevitable connection between the two, and they can be used independently.

Hot gas bypass requires the addition of a solenoid valve. However, the hot gas bypass valve cannot be replaced by a capillary tube.

The hot gas bypass valve is used to regulate pressure, reducing the high-temperature exhaust pressure to the required evaporating pressure. Theoretically, the suction pressure of the compressor is the same, the displacement remains unchanged, and the condensing load will not increase.

You can check it on the pressure-enthalpy diagram. Since the unit refrigeration capacity is reduced, the condensing load is also reduced.

Moreover, the solenoid valve should be controlled according to the changes in the cold room load. If the working condition of the compressor stays at a high evaporating temperature for a long time or frequently, it will be very dangerous without liquid injection. If there is no liquid injection under the maximum load and the return gas is overheated for a long time, the compressor is prone to thermal protection.

The amount of hot gas bypass = the refrigeration capacity of the compressor - the minimum load of the evaporator.