Impreza Wagon FWD F4-1820cc 1.8L SOHC (1995)
Expansion Valve: Description and Operation
Expansion Valve
1. MECHANISM
The expansion valve is attached to the evaporator inlet. It converts high pressure liquid refrigerant which comes from the liquid tank to misty, low
pressure refrigerant, and delivers to the evaporator Being at low pressure and low temperature, the liquid refrigerant evaporates in the evaporator
removing heat from the compartment. It automatically controls the flow rate of refrigerant to obtain the necessary cooling ability required by the
fluctuating heat load.
The expansion valve is composed of a sensing bulb with a capillary tube that senses the temperature at the evaporator outlet, an equalizer that
transmits the pressure of the refrigerant in the evaporator to the diaphragm and other parts such as the spring, ball and diaphragm.
2. FUNCTION
The operation of the external equalizer type is as follows.
The expansion valve opening is automatically controlled by the functions of three force: the pressure of the temperature-sensing bulb (P1)
containing a liquid or vapor, the pressure at the evaporator outlet (P2), and the force of the spring (F).
Temperature-sensing bulb pressure (P1)