The condensation pressure Pk is less than 2~3/(absolute), T0 > 0 (?) e.g. R11 (CFCl3), and its T0 is 23.7 (?). This kind of refrigerant is suitable for centrifugal refrigeration compressor of air conditioning system. Usually at 30 C, Pk is less than 3.06/.
Medium Pressure and Medium Temperature Refrigerants
The condensation pressure Pk < 20/(absolute), 0 (> T0 > - 60 (> T0). Such refrigerants as R717, R12, R22, etc. are commonly used in piston refrigeration air conditioning with single-stage compression and double-stage compression.
Shrinkage.
High pressure cryogenic refrigerant
The condensation pressure Pk is greater than 20/(absolute), and T0 is less than-70 C. For example, R13 (CF3Cl), R14 (CF4), carbon dioxide, ethane, ethylene and so on, these refrigerants are suitable for the low-temperature part of the cascade refrigeration unit or the low-temperature device below - 70 C.