A cycle of operations in a heat engine. The Rankine cycle more closely approximates to the cycle of a real steam engine that does the Carnot cycle. It therefore predicts a lower ideal thermal efficiency than the Carnot cycle. In the Rankine cycle, heat is added at constant pressure p1, at which water is converted in a boiler to superheated steam; the steam expands at constant entropy to a pressure p2 in the cylinder; heat is rejected at constant pressure p2 in a condenser; the water so formed is compressed at constant entropy to pressure p1 by a feed pump. The cycle was devised by the Scottish engineer W. J. M. Rankine (1820–70).