The expansion valve has different roles:
- It controls the drop in pressure for refrigerant evaporation & cold generation
- It controls the flow rate of the fluid in the evaporator
- It controls the evaporator output temperature (superheating).
The expansion valve is located downstream of the receiver drier: it receives the refrigerant fluid in a 100% liquid state and after it has been filtered. The expansion valve reduces the pressure of the refrigerant fluid upstream of the evaporator. This drop in pressure cools the fluid, it is then sprayed into the evaporator. The expansion valve is always attached to the evaporator.