When the heat pump air conditioner operates in cooling mode,Four way valve reversingConnect. At this point, the indoor heat exchanger becomes the evaporator, while the outdoor heat exchanger becomes the condenser. The low-temperature and low-pressure superheated gas from the indoor heat exchanger enters the gas-liquid separator through a four-way valve and muffler. After separating the liquid, the dry superheated gas is sucked in by the compressor and compressed into high-temperature and high-pressure gas, which is then dischargedfour-way valveEnter the outdoor heat exchanger to release heat and condense, becoming subcooled liquid. After being depressurized by capillary resistance, the supercooled liquid becomes a low-temperature and low-pressure two-phase fluid, which enters the indoor heat exchanger to evaporate and absorb heat (at this time, the indoor air is cooled down), and then passes through it againfour-way valveEnter the next cycle with the gas-liquid separator: The filter in the figure is mainly used for separating refrigerant from compressor oil to ensure the heat exchange efficiency of the heat exchanger. When the heat pump air conditioner operates in heating mode,Four way valve reversingConnect. At this point, the indoor heat exchanger becomes the condenser, and the outdoor heat exchanger becomes the evaporator. The low-temperature and low-pressure superheated gas from the outdoor heat exchanger passes throughfour-way valveAfter entering the gas-liquid separator with the muffler and separating the liquid, the dry and superheated gas is sucked in by the compressor and compressed into a high-temperature and high-pressure gas, which is then released. The gas enters the indoor heat exchanger through a four-way valve to release heat and condense (at this time, the indoor air is heated). It becomes a subcooled liquid, and the subcooled liquid capillary tube resistance is reduced to become a low-temperature and low-pressure two-phase fluid. It enters the outdoor heat exchanger to evaporate and absorb heat, and then the superheated gas is heatedfour-way valveEnter the next cycle with the gas-liquid separator. To prevent a decrease in indoor comfort caused by defrosting during heating, a hot air bypass uninterrupted heating defrosting method is adopted. When defrosting, the operating principle is basically the same as heating, except that the defrosting solenoid valve is turned on. Part of the high-temperature and high-pressure superheated gas coming out of the compressor is diverted to the outdoor heat exchanger, quickly raising the temperature of the outdoor heat exchanger to above O ℃, melting the frost layer on the outdoor heat exchanger, and maintaining good heat transfer efficiency.