Back to a liquid

Liquid at 45 °C

As it gives off heat, the refrigerant cools and turns back into a liquid at about 45 °C. Watch the large dots (gas) turn into small dots (liquid). It becomes a liquid even though it is hotter than the outdoors, because the pressure in these pipes is high, about 28 atm. The higher the pressure, the higher the boiling point.

Why?At high pressure, particles find it harder to escape from the liquid into a gas, so it has to get hotter before it boils. In a pressure cooker, water has to get hotter than 100 °C before it boils for the same reason. And the other way around: gas that cools below this temperature turns back into a liquid.

Learn moreWhen a gas turns into a liquid, it gives back as much heat as it took in when it boiled. So the refrigerant dumps a lot of heat in this part. A gas turning into a liquid is called condensation, and these pipes are called the condenser. When it leaves the condenser, the refrigerant is a liquid at about 40 °C.

Temperature where refrigerant turns liquid

45 °C

Turns liquid at

45 °C (28 atm)

Leaving the condenser

40 °C · liquid

calculated from R-32 property tables (CoolProp) · example: room 27 °C, outdoors 35 °C