Air Conditioners Move Heat
All scenes › Chapter 3 Compressor: squeeze it hot
Squeeze it and it heats up
The compressor squeezes the refrigerant gas and makes it hot
View in 3DSqueezed gas gets hot
The compressor inside the outdoor unit squeezes the refrigerant gas hard and forces it into a tight space. As the pressure rises from about 10 atm to about 28 atm, the gas warms from about 12 °C to about 92 °C. Now the refrigerant is a gas much hotter than the 35 °C outdoor air.
Why?The push that squeezes the gas makes its tiny particles move faster, and the faster they move, the higher the temperature. It is the same reason a bicycle pump gets warm at the tip when you pump hard.
Learn moreThe compressor uses more electricity than any other part of an air conditioner, and it sits inside the outdoor unit. The hum of an outdoor unit is mostly the compressor and the fan. Real compressors lose some energy to things like friction, so the calculation includes that too (70% efficiency).
- Refrigerant leaving the compressor
- 92 °C
- Going in
- 12 °C · 10 atm
- Coming out
- 92 °C · 28 atm
calculated from R-32 property tables (CoolProp) · example: room 27 °C, outdoors 35 °C
View this scene in 3D →Read more
More in the series
Temperatures, pressures and amounts of heat are calculated from property tables for the refrigerant R-32 (CoolProp). The example is a home air conditioner removing 2.5 kW of heat, with the room at 27 °C and the outdoors at 35 °C. In the 3D view, the refrigerant moves far slower than in real life, and the inside of the compressor and the expansion valve are shown as enlarged, simplified models.