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