Technical options for Organic Rankine Cycle systems A supercritical or transcritical cycle is a cycle with a maximum pressure higher than the critical one. Working fluid is heated up from subcooled liquid to superheated vapor with a smooth transition above the critical point.

The working principle of the organic Rankine cycle is the same as that of the Rankine cycle: the working fluid is pumped to a boiler where it is evaporated, passed through an expansion device (turbine, screw, scroll, or other expander), and then through a condenser heat exchanger where it is finally re-condensed.

An Organic Rankine Cycle (ORC) system is a closed thermodynamic cycle used for power production from low to medium-high temperature heat sources ranging from 80 to 400°C and for small-medium applications at any temperature level.

Critical Point (CP) is in the curve's center, as shown in Fig 1-a and 1-b above. The curved lines on the left side of the CP are saturated-liquid lines, and the region/area to the left of these lines are called sub-cooled liquid regions.