Resulting design criteria

Apart from the measures mentioned above, propane systems require practically no special features in the medium and low temperature ranges compared to a usual (H)CFC and HFC system. When sizing components, however, the relatively low mass flow should be considered (approximately 55 to 60% compared to R22). An advantage here is that the refrigerant charge can be greatly reduced. From the thermodynamic point of view, an internal heat exchanger between the suction and liquid line is recommended as this will improve the refrigerating capacity and COP.

Owing to the particularly high solubility of R290 (and R1270) in common lubricants, BITZER R290/R1270 compressors are charged with special oil of a high viscosity index and particularly good tribological properties.
Again, an internal heat exchanger is of advantage as it leads to higher oil temperatures, lower solubility and therefore improved viscosity.

Due to the very favourable temperature behaviour (Comparison of discharge gas temperatures), single stage compressors can be used down to approximately -40°C evaporation temperature. R290 could thus also be considered as an alternative for some of the HFC blends.