Expansion valves and Orifice tubes

Expansion valve

Expansion valve: to regulate the refrigerant flow

The expansion valve has different roles:

It controls the drop in pressure for refrigerant evaporation and 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.

Orifice tube

Orifice tube: an alternative to the expansion valve for some architectures of the air conditioning loop

The orifice tube is a tube with a given length and cross-section which expands the refrigerant but, unlike the expansion valve, it is unable to regulate flow rate and superheating.

The orifice tube is always associated with an accumulator at the evaporator outlet. Orifice tubes are made up of three main parts:

A metal tube with a chamfered inlet

A plastic tube body

An inlet and outlet filter If the A/C loop is contaminated, then the orifice tube becomes clogged. In this case, replace the orifice tube.

The orifice tube must always be replaced when another important part of the circuit is replaced (compressor, condenser, evaporator, accumulator). Valeo info: Flush the A/C loop before installing a new orifice tube.