Understanding the vapor compression cycle

The refrigerant vapor compression cycle

The vapor compression cycle is the most common method used in HVAC (Heating, Ventilation, and Air Conditioning) systems to provide cooling. The process involves four primary components: a compressor, a condenser, an expansion valve, and an evaporator.

Here's how the vapor compression cycle works:

1. Compression: The compressor takes in low-pressure refrigerant vapor and compresses it into a high-pressure, high-temperature gas.
2. Condensation: The high-pressure gas then flows into the condenser, which is a heat exchanger that removes heat from the refrigerant and releases it to the surrounding air or water. As the refrigerant gives up heat, it condenses into a high-pressure liquid.
3. Expansion: The high-pressure liquid then flows through the expansion valve, which reduces its pressure and causes it to expand rapidly. This expansion causes the refrigerant to cool down and change from a liquid to a low-pressure vapor.
4. Evaporation: The cool low-pressure refrigerant vapor then flows through the evaporator, which is another heat exchanger located in the indoor unit of the HVAC system. The warm air inside the building is blown over the evaporator, and the refrigerant absorbs heat from the air, causing the refrigerant to evaporate back into a low-pressure vapor.

The process then repeats from step 1, with the low-pressure vapor returning to the compressor to be compressed again.

Refrigerant cycle in an air-source heat pump (cooling mode)

Overall, the vapor compression cycle provides cooling by removing heat from the indoor air and releasing it to the outdoor air or water.

Additional resources

• YouTube video explaining the refrigeration cycle.

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