Reversible heat pumps work by transferring heat, rather than generating it, and can reverse this process to provide both heating and cooling. They essentially function like air conditioners but with the added capability to pump heat into a building during the winter. This is achieved through a reversing valve which changes the direction of refrigerant flow.
Here's a breakdown of how it works in both heating and cooling modes:
1. Basic Heat Pump Components:
- Refrigerant: A fluid that absorbs and releases heat as it changes state (liquid to gas and vice versa).
- Compressor: Increases the pressure and temperature of the refrigerant.
- Condenser: Releases heat from the refrigerant to the surrounding environment (either indoors or outdoors, depending on the mode).
- Evaporator: Absorbs heat from the surrounding environment, causing the refrigerant to evaporate.
- Expansion Valve (or Metering Device): Reduces the pressure of the refrigerant before it enters the evaporator.
- Reversing Valve: This is the key component that allows the heat pump to switch between heating and cooling modes.
2. Cooling Mode (Air Conditioning):
- The refrigerant absorbs heat from inside the home in the evaporator (indoor coil), cooling the air.
- The refrigerant, now a hot gas, flows to the compressor, which increases its pressure and temperature.
- The high-pressure, hot refrigerant then flows to the condenser (outdoor coil), where it releases heat to the outside air.
- The refrigerant, now a cooler liquid, flows through the expansion valve, which reduces its pressure and temperature.
- The cycle repeats.
3. Heating Mode:
- The reversing valve changes the direction of refrigerant flow.
- The refrigerant absorbs heat from the outside air in the evaporator (now the outdoor coil), even when it's cold outside. It's important to note that even cold air contains some heat energy.
- The refrigerant, now a cool gas, flows to the compressor, which increases its pressure and temperature.
- The high-pressure, hot refrigerant then flows to the condenser (now the indoor coil), where it releases heat into the home.
- The refrigerant, now a cooler liquid, flows through the expansion valve, which reduces its pressure and temperature.
- The cycle repeats.
4. Reversing Valve Operation:
The reversing valve is a solenoid-operated valve that changes the path of the refrigerant based on whether heating or cooling is desired. When energized, it directs the hot, high-pressure refrigerant from the compressor to the indoor coil (heating mode). When de-energized, it directs the hot refrigerant to the outdoor coil (cooling mode).
In essence, a reversible heat pump uses the same components and processes for both heating and cooling; the reversing valve simply changes the direction in which the heat is transferred. This makes them a versatile and efficient option for year-round climate control.
