Constant Pressure Expansion Valve

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Constant pressure expansion valve also known as an automatic expansion valve. Since it maintains the constant evaporator pressure. Evaporator pressure is the main moving force. Dry expansion evaporators uses constant pressure expansion valve where the load is generally constant. It consists of a needle valve and a seat which shapes a hole, spring and an altering screw. It also consists of a metallic diaphragm or bellows. The opening and shutting of the valve as for seat relies on the two opposing forces acting on the diaphragm:

  • The spring pressure and the atmospheric pressure acting on the top of the diaphragm.
  • The evaporator pressure acting below the diaphragm.
Constant Pressure Expansion Valve

Constant Pressure Expansion Valve


Working of Constant Pressure Expansion Valve

  • At the point when the compressor is running, the valve keeps up an evaporator pressure in harmony with the spring pressure and the atmospheric pressure. The spring pressure can be shifted by changing the strain of the spring with the assistance of spring altering screw.
  • When the spring is balanced for an ideal evaporator pressure, at that point the valve works automatically, to keep up consistent evaporator pressure by controlling the flow of refrigerant to the evaporator.
  • When the evaporator pressure falls down the diaphragm moves to descend to open the valve. This permits progressively fluid refrigerant to go into the evaporator. It flows till the ideal evaporator pressure reaches.
  • Again, when the evaporator pressure rises, the diaphragm moves upwards to decrease the opening of the valve. This diminishing the progression of fluid refrigerant to the evaporator. Thus, brings down the evaporator pressure till the ideal evaporator pressure reaches. 
  • At the point when the compressor stops, the liquid refrigerant keeps on flowing into the evaporator and increases the pressure in the evaporator. This increase in evaporator pressure causes the diaphragm to move upwards and the valve shuts. It stays shut until the compressor begins again and diminishes the pressure in the evaporator.


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