Understanding the Rankine Cycle Process

Sep 18, 2024

Rankine Cycle Lecture Notes

Overview

  • The Rankine Cycle is essential for converting heat energy into mechanical work, particularly in steam turbine power plants.
  • Key components include the boiler, turbine, condenser, and pump.

Components of the Rankine Cycle

1. Boiler

  • Function: Converts water into steam at constant pressure (Process 1 to 2).
  • Process:
    • Water is supplied from the feed pump and heated by burning fuel.
    • Heat addition occurs at constant pressure, raising the temperature to reach the saturation point.
    • Process is represented on the PV diagram as a horizontal line (constant pressure).

2. Turbine

  • Function: Expands steam to produce mechanical work (Process 2 to 3).
  • Process:
    • Steam enters turbine at high pressure and temperature, expands isentropically, and produces work.
    • The work done by the turbine is represented as WT = h2 - h3.
    • Point 3 can be in various states: saturated, dry, or superheated.

3. Condenser

  • Function: Rejects heat to the atmosphere (Process 3 to 4).
  • Process:
    • Exhaust steam from turbine enters condenser, where it condenses back into water at constant pressure.
    • Heat rejected is represented as QR = h3 - h4.

4. Pump

  • Function: Increases pressure of the liquid water (Process 4 to 1).
  • Process:
    • Water from the condenser is pumped back to the boiler at a higher pressure.
    • Work required for pumping is represented as WP = h1 - h4.

PV and TS Diagrams

PV Diagram

  • Key Points:
    • Process 1 to 2: Constant pressure heat addition.
    • Process 2 to 3: Isentropic expansion.
    • Process 3 to 4: Constant pressure heat rejection.
    • Process 4 to 1: Isentropic compression.

TS Diagram

  • Key Points:
    • Similar representation as PV diagram but focused on temperature and entropy.
    • Important to identify critical points and phase changes.

Efficiency of the Rankine Cycle

  • Equation for Efficiency:

    • Efficiency (η) = (Net Work Developed) / (Heat Supplied in Boiler)
    • Net Work Developed:
      • WT (turbine work) - WP (pump work) = (h2 - h3) - (h1 - h4)
    • Heat Supplied: QS = h2 - h1

  • Final Efficiency Equation:

    • η = 1 - (QR / QS)
    • Neglecting pump work gives a simplified equation for efficiency.

Conclusion

  • The lecture summarizes the Rankine Cycle's functioning, components, diagrams, and efficiency calculations.
  • Encouragement to engage with related content for better understanding.