Rankine cycle (redirected from Reverse-Rankine cycle)

Rankine cycle

Ideal cyclical sequence of changes of pressure and temperature of a fluid, such as water, used in an engine, such as a steam engine. Described in 1859 by William Rankine, it is used as a standard for rating the performance of steam power plants. In the Rankine cycle, the working substance of the engine undergoes four successive changes: (1) heating at constant volume (as in a boiler), (2) evaporation and superheating (if any) at constant pressure, (3) isentropic expansion in the engine, and (4) condensation at constant pressure with return of the fluid to the boiler. See also Carnot cycle.

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Rankine cycle

A thermodynamic cycle used as an ideal standard for the comparative performance of heat-engine and heat-pump installations operating with a condensable vapor as the working fluid. Applied typically to a steam power plant, as shown in the illustration, the cycle has four phases: (1) heat addition bcde in a boiler at constant pressure p₁ changing water at b to superheated steam at e, (2) isentropic expansion ef in a prime mover from initial pressure P₁ to back pressure P₂, (3) heat rejection fa in a condenser at constant pressure p₂ with wet steam at f converted to saturated liquid at a, and (4) isentropic compression ab of water in a feed pump from pressure p₂ to pressure p₁.

This cycle more closely approximates the operations in a real steam power plant than does the Carnot cycle. Between given temperature limits it offers a lower ideal thermal efficiency for the conversion of heat into work than does the Camot standard. Losses from irreversibility, in turn, make the conversion efficiency in an actual plant less than the Rankine cycle standard. See Carnot cycle, Refrigeration cycle, Thermodynamic cycle, Vapor cycle