Which cycle is used in AC?

Which cycle is used in AC is the vapor compression refrigeration cycle, which is the fundamental thermodynamic cycle that makes air conditioning and refrigeration possible. This cycle has four main components and four processes that repeat continuously. First, the compressor compresses low-pressure, low-temperature refrigerant vapor into high-pressure, high-temperature vapor, requiring electrical work. Second, in the condenser coil located outdoors, the hot vapor releases heat to outside air and condenses into high-pressure liquid. Third, the liquid passes through an expansion device such as a capillary tube or thermostatic expansion valve where pressure drops sharply, causing temperature to drop and producing a mixture of cold liquid and vapor. Fourth, in the evaporator coil indoors, the cold refrigerant absorbs heat from indoor air, evaporating completely into low-pressure vapor, which returns to the compressor. This cycle transfers heat from inside to outside against its natural direction using work input. Variations include reverse cycle for heat pumps providing heating by reversing flow, and absorption cycle using heat instead of compressor in some applications, but standard residential and commercial AC uses vapor compression.