Understanding the Ideal Rankine Cycle

The Rankine cycle is a fundamental thermodynamic cycle widely used in power plants to convert heat into mechanical work, typically using water as the working fluid. It is an idealized cycle that provides a theoretical basis for analyzing the performance of steam power plants.

The ideal Rankine cycle consists of four main processes:

• Process 1-2: Isentropic Compression in a pump. The working fluid (liquid water) is compressed from low pressure to high pressure. This process is considered isentropic, meaning it occurs without entropy change.
• Process 2-3: Isobaric Heat Addition in a boiler. The high-pressure liquid enters the boiler and is heated at constant pressure. It is first heated to the saturation temperature, then vaporized completely, and often superheated to a higher temperature.
• Process 3-4: Isentropic Expansion in a turbine. The high-pressure, high-temperature steam expands through the turbine, producing work. This expansion is considered isentropic, meaning it occurs without entropy change and is adiabatic (no heat transfer).
• Process 4-1: Isobaric Heat Rejection in a condenser. The low-pressure steam leaves the turbine and enters the condenser, where it is condensed back into a saturated liquid at constant pressure by rejecting heat to a cooling medium.

Therefore, the ideal Rankine cycle is comprised of two isentropic processes (pump and turbine) and two isobaric processes (boiler and condenser).