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Rankine Cycle: Interactive Simulations

These simulations were prepared using Mathematica. Download the free Wolfram player, and then download the simulation CDF file (link given below or click on figure to download). Try to predict the behavior when a parameter changes before using a slider to change that parameter. Screencasts below explain how to use these simulations.

Simulation: Rankine Cycle

In a Rankine cycle, high-pressure liquid water (1) enters a boiler where it is heated to saturation temperature (2), vaporized, and superheated (3). The superheated steam is fed to a turbine, where it expands and generates mechanical work. The steam exits the turbine at a lower pressure and temperature as either superheated steam or steam with a vapor quality (4). After the steam is condensed (5), a pump compresses the liquid water to high pressure (1). Select “P-H diagram” to see the cycle on a pressure-enthalpy diagram. Use sliders to select the inlet pressure to the turbine P3 and one of four outlet pressures P4 . Use a slider to vary the turbine efficiency ηT , which is the ratio of work produced by the turbine to the work produced by a reversible turbine between the same inlet and outlet pressures. The irreversible turbine pathway (ηT < 1) is the dashed black line on the P-H diagram; the reversible turbine pathway is the orange dashed line. Select “Rankine cycle” to view a schematic of the cycle, and select “turbine” to show the inlet and outlet conditions for the turbine and the work generated.

Try to answer these questions before determining the answer with the simulation. We suggest that you write down the reasons for your answers.

1. How does decreasing the outlet pressure affect the work generated by the turbine?
2. As the inlet pressure to the turbine increases, but the inlet temperature and the outlet pressure stay the same, does the enthalpy of the steam exiting a reversible turbine increase or decrease?
Simulation: Compare Compressors or Turbines with Different Efficiencies (optional)

This Demonstration compares two adiabatic compressors or turbines with different efficiencies. Air, which is assumed to be an ideal gas is either compressed or expanded. Select “turbine”, and select whether to “compare at the same outlet pressure” or “temperature” using the buttons. Select the outlet pressure or temperature, and select the efficiency of each turbine with sliders. The efficiency is relative to a reversible turbine.

Try to answer these questions before determining the answer with the simulation. We suggest that you write down the reasons for your answers.

1. For the same outlet pressure, will a less-efficient turbine have a higher outlet temperature than a more efficient one if air is used in the turbine? Which produces more work?
2. If the inlet conditions are the same for a reversible turbine and an irreversible turbine that both use air, and the outlet temperature is the same for both, which turbine generates more work?