空气源热泵与简单蒸气压缩循环较为相似，也由压缩机、冷凝器、节流阀和蒸发器串联而成，唯一的区别是在压缩机出口设置四通阀用于制冷和热泵模式下的制冷剂流向切换，如图1所示。在制冷模式下，压缩机出口排气经四通阀被引入室外冷凝器，制冷剂向环境空气放热后被冷凝成液体，之后液态制冷剂节流为低压两相状态，在蒸发器中吸收外侧流体中的热量，实现制冷效果；蒸发后的制冷剂返回到压缩机，被循环压缩。制热模式下，四通阀切换制冷剂流通方向，压缩机排气经四通阀被引入室内冷凝器，制冷剂向室内空气或流体中排热，实现供暖；然后液态制冷剂经节流为低压两相状态，通过室外换热器吸收环境空气中的热量。
The air source heat pump is similar to the simple vapor compression cycle. It is also composed of a compressor, a condenser, a throttle valve and an evaporator in series. The only difference is that a four-way valve is set at the outlet of the compressor for refrigerant flow switching in refrigeration and heat pump modes, as shown in figure 1. The heat is introduced into the liquid refrigerant at the outlet of the compressor and discharged into the refrigeration mode of the four-way refrigerant after being throttled to the outside, which is cooled by the refrigerant at the outlet of the condenser; The evaporated refrigerant returns to the compressor and is circularly compressed. In the heating mode, the four-way valve switches the refrigerant flow direction, the compressor exhaust is introduced into the indoor condenser through the four-way valve, and the refrigerant discharges heat into the indoor air or fluid to realize heating; Then, the liquid refrigerant is throttled to a low-pressure two-phase state, and absorbs the heat in the ambient air through the outdoor heat exchanger.