In this case, the refrigerant is sprayed, which facilitates the evaporation process.
The expansion valve also regulates the flow of refrigerant supplied to the evaporator.
The refrigerant flow is controlled by the opening of the ball valve in the expansion valve.
The amount of opening is controlled by the balance of R-134a pressure on the diaphragm and the resulting pressure force at the outlet of the evaporator (PI) – on the bottom of the diaphragm and spring force (Fs), acting on the ball valve.
As PI increases, the temperature of the temperature sensor near the diaphragm rises, and the Pd of heated R-134a at the diaphragm increases.
When Pd is greater than PI + Fs, the diaphragm flexes downward and a shaft attached to the end of the temperature probe pushes down on the ball valve, increasing the refrigerant flow.
Pic. 8.65. The principle of operation of the expansion valve: 1 - diaphragm; 2 – temperature sensor; 3 - shaft; 4 - ball valve; 5 - spring; 6 - from the evaporator; 7 - to the evaporator; 8 - from the capacitor; 9 - on the capacitor; 10 - spring force; 11 – HFC-134a pressure; 12 - outlet pressure
When the temperature of the refrigerant leaving the evaporator decreases, PI + Fs becomes greater than Pd, the ball valve rises and the refrigerant flow decreases.