During the use of the Refrigerated air dryer, if the suction temperature is too high, which is much higher than the design dew point temperature, what should be done? We will provide solutions based on cause analysis:

Cause analysis 1:

The expansion valve is out of control.

When the cooling load (air handling capacity) increases, the refrigerant suction temperature increases, and the temperature of the thermal expansion valve temperature sensing package also increases accordingly. Through the adjustment of the regulating spring in the valve, the opening of the valve is increased, and the flow of liquid refrigerant is increased, thus reducing the suction temperature. However, if there are impurities in the expansion valve, the regulating spring is stuck and the expansion valve cannot be opened. The flow of liquid refrigerant remains unchanged, and excessive cooling load will change all liquid refrigerants into gas. The gas refrigerant absorbs heat and the temperature rises sharply, resulting in excessive "superheat".

resolvent:

Disassemble the valve for maintenance or replacement

Cause analysis 2:

The heat exchange area of evaporator is too large or the design is unreasonable.

Under normal working conditions, the liquid refrigerant in the evaporator accounts for 70% of the total space, thus ensuring proper suction "superheat". If the designed heat exchange area of the evaporator is too large (large evaporator is often used to ensure the air pressure drop in the design of the low pressure cold dryer), the liquid refrigerant in the evaporator is completely converted to the gas state prematurely (or due to structural reasons, the liquid refrigerant cannot be filled into the appropriate space of the evaporator), the gas refrigerant absorbs heat and the temperature rises significantly, leading to high suction temperature.

resolvent:

The model of thermal expansion valve was enlarged, and the evaporator was redesigned.

Cause analysis 3:

Unreasonable design of liquid pipeline leads to "instant evaporation".

When the liquid refrigerant appears "instant evaporation" phenomenon, the temperature of the liquid pipeline drops significantly, part of the liquid refrigerant will change to the gaseous state, and the volume of the refrigerant will increase significantly. The selected thermal expansion valve is designed based on liquid refrigerant, and the volume of refrigerant (whether gaseous or liquid) it can pass through is unchanged. When "instant evaporation" occurs, the refrigerant volume flow through the thermal expansion valve remains unchanged, but the mass flow decreases a lot (the volume of gas with the same mass is much larger than the volume of liquid). That is to say, the quality of refrigerant supplied by the thermal expansion valve to the evaporator is far from enough, resulting in excessive "overheating" of refrigerant gas.

resolvent:

Redesign the liquid pipeline and discharge the factors that cause the pressure drop of liquid refrigerant in the pipeline to increase.