Which of the following statements is true regarding the Rankine cycle?

The Rankine cycle is a thermodynamic cycle commonly used for converting heat into mechanical energy, primarily in power plants. The statement indicating that heat addition occurs at constant pressure is true. In the Rankine cycle, the process involves heating the working fluid (usually water) in a boiler, where it absorbs heat from an external source. This heating leads to an increase in temperature and results in a phase change from liquid to vapor, but it specifically occurs at constant pressure.

This is a crucial feature of the cycle, as the generation of steam at constant pressure is key to effectively driving the turbine and producing work. By maintaining a constant pressure during the heat addition phase, the cycle efficiently utilizes the energy from the heat source.

The ability for the Rankine cycle to effectively manage the phase change between liquid and vapor while maintaining constant pressure is integral to its operation, which distinguishes it from other cycles that may not utilize this characteristic.