Rankine Vapor Power Cycle

Vapor-liquid phase-change thermodynamic cycle driving steam turbines in thermal, nuclear, and solar power stations.

Specifications & Metrics

type: Phase-Change Vapor Cycle
processes: Isentropic liquid pumping (1→2), isobaric boiler vaporization (2→3), isentropic turbine expansion (3→4), isobaric condensation (4→1)
working fluid: Water/steam (or organic fluids such as n-pentane/toluene in Organic Rankine Cycles)
efficiency formula: η = (W_turbine − W_pump) / Q_in ≈ (h₃ − h₄) / (h₃ − h₂)
originator: William John Macquorn Rankine (1859)
applications: Coal, natural-gas combined-cycle, nuclear fission, and concentrated solar thermal steam power plants

Named after Scottish polymath William John Macquorn Rankine, the Rankine cycle condenses exhaust steam completely into liquid water before pumping, so the feedwater pump consumes only 1% to 3% of the gross turbine work output.
Superheating the steam above its saturation dome and reheating it between high- and low-pressure turbine stages raises the average heat-addition temperature while preventing high-velocity liquid droplets from eroding turbine blades.
Modern ultra-supercritical steam power plants operate above water's critical point (22.1 MPa, 374 °C) at pressures up to 31 MPa and temperatures of 600 °C, achieving standalone thermal efficiencies of 42% and exceeding 60% when paired as the bottoming cycle of a gas turbine.