Thermal Expansion Valve (TXV) and a Hot Gas Bypass Valve (HGBPV) in refrigeration dryers

Have you ever noticed the similarities and differences between a Thermal Expansion Valve ( TXV) and a Hot Gas Bypass Valve ( HGBPV)  in refrigeration dryers?

Here is what you may need to know:

• Both are deemed to control the dryer cooling capacity as per the requirement/ loading of the dryer.
• Both function using their probe to check the refrigerant temp upstream the compressor/downstream evaporator to adjust the refrigerant flow and cooling capacity.
• Both are filled with a gas which could be identical to the dryer refrigerant or different.
• Both convert the temp into pressure to accomplish the refrigerant flow control and thereon the dryer cooling capacity.
• Both are adjustable.
• While TXV controls the dryer capacity by adjusting the liquid refrigerant entering the evaporator, HGBPV adjusts the high temp., high pressure gaseous refrigerant return back to the compressor.
  
• While for reduced loading of the dryer, TXV limits the refrigerant flow into the evaporator, HGBPV, directs more refrigerant gas back into the compressor.
  
• While TXV is the first to react to partial loading, HGBPV starts later to prevent TXV from overcompensating.
  
• While HGBPV is normally used in any dryer, TXV is sometimes replaced with a Capillary Tube (CT)