Refrigeration process design

Different thermodynamic properties of the refrigerants lead to different optimum process and system designs. Here, 3 different system layouts are evaluated in parallel:

Single stage compression, low suction superheat.
This layout represents a simple circuit with dry expansion.
Single stage compression, high useful suction superheat.
This layout represents a simple circuit with an internal heat exchanger that superheats the gas after the evaporator by subcooling the liquid leaving the condenser. Please be aware that the enthalpy difference of the subcooling is identical with that of the superheat and thus only one of these can be counted in the refrigeration capacity.
Economiser system.
This layout cools the compression by mixing some refrigerant in that evaporates at an intermediate pressure and thereby subcools the main mass flow after the condenser. For this system, 2-stage compressors resp. screw or scroll compressors with economiser port are necessary (for screw compressors see BITZER document ST-610, for scroll compressors EST-610).

System processes in p-h-diagram: simple circuit with low superheat (red), single stage compression with high superheat via internal heat exchange (green) and economiser system (yellow).