Any user's compressed air load is always changing, so the refrigerating capacity of the cold dryer is required to change accordingly to adapt to the change of compressed air load, so as to achieve stable pressure dew point. In the cold dryer, expansion valve (or capillary tube), bypass valve (fluorine solenoid valve), water control valve/pressure switch and other components participate in the regulation of refrigeration capacity of the cold dryer.

Cold dryer

1. The throttling function of the expansion valve changes the condensed refrigerant from normal temperature and high pressure to low temperature and low pressure and supplies it to the evaporator. At the same time, the refrigerant liquid supply is controlled by detecting the suction superheat of the refrigeration compressor, so as to adjust the refrigeration capacity of the evaporator to adapt to the compressed air load.

2. When the expansion valve reduces the liquid supply of the evaporator to adapt to the change of compressed air load, the bypass valve also acts-the refrigerant without condensation is directly bypassed to the back of the expansion valve or the suction side of the compressor. Its functions are as follows: 1) When the refrigeration compressor works, the displacement is unchanged. When the expansion valve reduces the refrigerant supplied to the evaporator, a part of the refrigerant stays on the high pressure side of the refrigeration system, and the bypass can make the refrigeration cycle proceed normally; 2) Prevent the phenomenon of icing (i.e., "ice blocking") in the evaporator when the compressed air load is reduced (because the surface temperature of the evaporator copper tube may be lower than the freezing point of water when the load is reduced, the condensed water will freeze in the evaporator and block the airflow channel); 3) It can prevent the compressor from "liquid hammering" phenomenon.

3. The refrigeration system is a cycle process, so after adjusting the evaporator and compressor to adapt to the compressed air load through the expansion valve and bypass valve, the condensing capacity of the condenser is also required to adapt to the load change of the evaporator. The condensation capacity of the condenser in the cold dryer is regulated by the water quantity regulating valve (water condenser) or the pressure switch (air condenser). By detecting the refrigerant condensation pressure, the water quantity regulating valve can automatically adjust the opening degree of its valve core to control the cooling water quantity and keep the refrigerant pressure within the normal range. By detecting the refrigerant condensation pressure, the pressure switch can automatically start/stop the cooling fan of the condenser and keep the refrigerant pressure within the normal range.