The refrigerant cycle is the process by which a refrigerant is used to transfer heat from one location to another in a heating, ventilation, and air conditioning (HVAC) system. The refrigerant cycle is a critical component of many types of HVAC systems, including air conditioners, heat pumps, and refrigerators, and it is used to cool or heat the air in a building or structure.

The refrigerant cycle begins when the refrigerant is compressed in the compressor, which increases the temperature and pressure of the refrigerant. The hot, high-pressure refrigerant is then passed through the condenser, where it releases its heat to the outside air and is cooled. The cooled, high-pressure refrigerant is then passed through the expansion valve, where it is allowed to expand and its pressure is reduced. The low-pressure, cooled refrigerant is then passed through the evaporator, where it absorbs heat from the air in the building or structure and is warmed. The warmed, low-pressure refrigerant is then returned to the compressor to start the cycle again.

The refrigerant cycle is a continuous process, and it is designed to maintain a constant temperature in the building or structure by removing excess heat or adding heat as needed. The efficiency of the refrigerant cycle depends on the design of the HVAC system and the properties of the refrigerant being used, and it is important to properly maintain and service the system to ensure that it is functioning properly and efficiently.