It's like reversing the valve and putting the CO2 back where it came from.
这就像扭转阀门并将二氧化碳放回原来的地方。
英语百科
Reversing valve
A reversing valve a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow. By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a residence or facility to be heated and cooled by a single piece of equipment, by the same means, and with the same hardware.