1. Gas

At temperatures below 0°C, the properties of nitrogen, air and helium are similar to those described above for gases used as heat transfer fluids, and the main points made in the previous article [BE 9 571] apply to gases used as refrigerants.

The only specific aspect of using these fluids at low temperatures is associated with the presence of water vapour mixed with these gases, and the risk of frost forming on the cooled walls of the circuit (often the evaporator of the refrigeration unit). This presence of water vapour, which generally has harmful consequences, is due to leaks...