Views: 0 Author: Site Editor Publish Time: 2026-06-04 Origin: Site
The evaporator is the cold side heat exchanger of a heat pump, operating in two working modes depending on cooling/heating cycle via reversing valve:
Cooling mode (summer): Absorbs indoor air heat → refrigerant evaporates from liquid to low-pressure gas, cools room air.
Heating mode (winter): Swaps role with condenser via 4-way valve; becomes the outdoor heat absorber, picking ambient heat from outside air even at low temp.
Key principle: Refrigerant boils at low pressure/low temp inside coil to capture free environmental heat for heat pump heating.
Working Cycle Breakdown (Heating Mode, Air-source HP)
Low-pressure, low-temp liquid refrigerant enters evaporator tubes.
Outdoor ambient air blows across fins → refrigerant absorbs air heat and vaporizes into cold suction gas.
Cold gaseous refrigerant flows back to compressor, compressed into high-pressure hot gas.
Hot gas moves to indoor condenser coil to release heat and warm indoor air.
Critical Design Parameters
Fin spacing: 10–14 FPI (10–12 FPI for humid climate to boost dehumidification).
Tube: Copper tube + hydrophilic aluminum fin (anti-corrosion, fast condensate drain).
Superheat control: Maintained 5–12°F to prevent liquid refrigerant flood-back damaging compressor.
Common Faults & Impacts
Dirty clogged fins: Reduced airflow → poor heat absorption → low heating/cooling capacity, high compressor current.
Frost/ice buildup (outdoor evaporator in winter): Triggers auto defrost cycle; excessive ice causes system efficiency drop.
Leaking coil: Low refrigerant charge → insufficient evaporation, weak heat pump performance.
