In addition to heating a property or building, an air-to-water heat pump can also provide cooling. In this mode, the thermodynamic cycle is reversed, and the building is cooled via underfloor heating or another emission system. This cooling process is made possible by a four-way valve within the heat pump. This valve alters the flow direction of the refrigerant. In this article, we explain exactly how the four-way valve in a heat pump operates.
The function of the four-way valve
The four-way valve allows a heat pump to provide both heating and cooling. This mechanism changes the direction in which the refrigerant flows through the device, effectively reversing the functions of the heat exchangers: the finned tube exchanger becomes the condenser, and the plate heat exchanger becomes the evaporator. Inside the four-way valve is a sliding mechanism known as the actuator. An electromagnetic force triggers this component to switch to the desired position. This shift in the actuator changes the refrigerant's flow path, allowing the heating water in the building to be either cooled or heated, depending on the requirements.
The heating and cooling process via the four-way valve
A heat pump operates on a closed cycle consisting of four main components: an evaporator, a compressor, a condenser, and an expansion valve. During heating: The evaporator (finned tube exchanger) extracts heat from the outside air. The refrigerant evaporates, is pressurized by the compressor (which further increases the temperature), and then releases heat to the building's water circuit via the condenser (plate heat exchanger).
Reversing the cycle
During cooling: This is where the four-way valve comes into play. It reverses the flow direction of the refrigerant, swapping the roles of the heat exchangers. The finned tube exchanger now acts as the condenser, and the plate heat exchanger acts as the evaporator.
The cooling process step-by-step:
- Relatively warm water from the building flows through the plate heat exchanger.
- Upon contact with this warmer water, the refrigerant evaporates and absorbs heat from the exchanger (providing cooling).
- The compressor then increases the pressure and temperature of the refrigerant.
- In the finned tube exchanger, the refrigerant condenses, releasing the absorbed heat into the outside air. The refrigerant cools down and becomes liquid.
- The pressure drops via the expansion valve, the refrigerant becomes cold, and the cycle begins again.
This process creates chilled water in the building's circuit, which radiates "cold" via underfloor heating, climate ceilings, or other emission systems.
The four-way valve during the defrost cycle
When temperatures drop in winter, frost and ice can build up on the finned tube exchanger. In this case, the heat pump automatically melts the ice by running a defrost program. The four-way valve switches to the "cooling" position, causing the finned tube exchanger to heat up due to the reversed cycle. Once the ice has melted, the four-way valve switches back, restoring the original flow direction to resume heating the building.
Want to learn more about our heat pumps?
Our heat pumps utilize the four-way valve to provide both heating and cooling. We even offer 4-pipe systems that can heat and cool simultaneously. This is particularly beneficial for environments like hospitals, where operating rooms with sensitive equipment may require cooling while public areas need to be heated at the same time.
Interested in seeing our technology in action? Please feel free to contact us or visit our factory. We have a working heat pump system on-site for you to inspect. We look forward to welcoming you.
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