Expansion valve in a heat pump: what is its role

The expansion valve controls the amount of refrigerant entering the evaporator and reduces its pressure.

Pressure drop

After expansion, the refrigerant is at a lower pressure and temperature.

Flow control

Proper supply to the evaporator is critical for constant superheat and high efficiency.

Modern systems

Many heat pumps use an electronic expansion valve (EEV) for precise control at different loads.