The invention relates to a multi-split air-conditioning
system and a
supercooling and enhanced vapor injection method thereof. The multi-split air-conditioning
system comprises a compressor, an outdoor side
heat exchanger, an indoor unit
heat exchanger, a gas-liquid separator, an
intermediate heat exchanger, a first four-way valve and a second four-way valve which are connected through pipelines. As the second four-way valve, a first
branch circuit and the
intermediate heat exchanger are arranged in the multi-split air-conditioning
system, during cooling operation, the
intermediate heat exchanger serves as a subcooler, a
cooling medium flows in different directions through adjustment by the first
branch circuit and the second four-way valve after passing through the intermediate
heat exchanger, and accordingly, the
cooling medium of the first
branch circuit cools down a main-circuit
cooling medium to achieve the
supercooling purpose; and during heating operation, the intermediate heat exchanger serves as an
economizer, the cooling medium passes through the first branch circuit and the second four-way valve after passing through the indoor unit heat exchanger, and then is sprayed into a medium-pressure cavity of the compressor through a jet orifice to supply a medium-pressure gaseous cooling medium for the compressor. The structure is simple and the
supercooling and enhanced vapor injection purposes are better achieved.