Compare reheat and regeneration cycles in steam power plants.

Both improve Rankine cycle efficiency but through different mechanisms. Reheat returns partially expanded steam to the boiler for reheating before completing expansion, increasing average heat addition temperature and preventing excessive moisture at turbine exit. Regeneration uses extracted steam to preheat feedwater, reducing external heat input required. Reheat primarily addresses moisture content and mean temperature of heat addition, while regeneration reduces heat rejection. Modern plants combine both - feedwater heating through 6-8 stages and single or double reheat.