The Rankine cycle is a theoretical thermodynamic cycle used widely by coal-fired power plants or nuclear reactors, where the rejected heat is used to produce steam and generate electricity.

The four processes of the cycle are the compression in a pump, phase change from liquid to steam in a boiler, expansion of steam in a turbine, and the phase change from vapour to liquid in a condenser.

Brayton cycle is a combined power plant cycle that utilizes a gas turbine to generate electricity. 

Both Carnot and Rankine cycles are theoretical thermodynamic cycles. The Carnot cycle extrapolates the maximum efficiency of the cycle. The Rankine cycle’s efficiency is slightly lower than the Carnot cycle. In real situations, the Carnot cycle does not ensure operation but the Rankine cycle does

They are prominently in use in nuclear reactors, coal-powered power plants, geothermal plants, and industries that use steam as the working fluid.