Problem Description

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: 600^oC
• The actual data measured by Neon are:
  P₁ = 9 kPa       T₁ = 38^oC
  P₂ = 16 MPa    
  P₃ = 15.9 MPa
  P₄ = 15.2 MPa  T₄ = 625^oC
  P₅ = 15 MPa     T₅ = 600^oC
  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.

• 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?

• 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.