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THERMODYNAMICS - CASE STUDY

    Introduction


Problem Description
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The Actual Cycle



 

Neon, who works in a steam power plant, is asked to monitor the performance of a new system. The new system is running a Rankine cycle with water as the working fluid.

What is known:

  • The Schematic of the new system is shown on the left. The design data is:
    Condenser Pressure: 10 kPa
    Boiler Pressure: 16 MPa
    Steam temperature at the turbine inlet: 600oC
  • The actual data measured by Neon are:
    P1 = 9 kPa       T1 = 38oC
    P2 = 16 MPa    
    P3 = 15.9 MPa
    P4 = 15.2 MPa  T4 = 625oC
    P5 = 15 MPa     T5 = 600oC
    P6 = 10 kPa   
  • The pump has an efficiency of 85% and the turbine has an efficiency of 80%.   
  • The mass flow rate is 20 kg/s.
   
  Question

 
  • What is the net work output?
  • What is the thermal efficiency of the cycle?
  • What is the thermal efficiency if modeling the cycle as an ideal Rankine cycle with the design data?
     
    Approach

   
  • Model the cycle of new system as a Rankine cycle.
  • Use the water table to determine the enthalpy at each state.
  • The net work output equals the difference between the turbine work and the pump work.
  • The heat input equals the enthalpy difference between the boiler exit and inlet.