Finding Turbine Inlet State - Thermodynamics

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SUMMARY

The discussion focuses on calculating the turbine inlet state in a thermodynamic system with a maximum turbine work output rate of 6.0 MW and an isentropic efficiency of 90%. The turbine exit state is given as 40 kPa with a quality (x) of 92%. The user attempts to find the inlet enthalpy using the equation W = ΔH and the specific enthalpy values from the saturated liquid table. The calculated exit enthalpy is 2450.18 kJ/kg, leading to an inlet enthalpy of 8636.1 kJ/kg, which raises questions about the validity of the results when compared to superheated tables.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically the first law of thermodynamics.
  • Familiarity with turbine performance metrics, including isentropic efficiency.
  • Knowledge of steam tables, particularly saturated and superheated steam properties.
  • Ability to perform enthalpy calculations using the equations W = ΔH and h = hf + xhfg.
NEXT STEPS
  • Review the calculation of turbine work output and the role of mass flow rate in thermodynamic systems.
  • Study the use of superheated steam tables to accurately determine pressure and temperature relationships.
  • Explore the implications of adiabatic processes in turbine and pump operations.
  • Investigate the effects of varying isentropic efficiency on turbine performance metrics.
USEFUL FOR

Students and professionals in mechanical engineering, particularly those specializing in thermodynamics and energy systems, as well as anyone involved in turbine design and performance analysis.

Magnawolf
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Homework Statement


max. Turbine work output rate: 6.0MW
Turbine isentropic efficiency: 90%
Turbine exit state (isentropic): 40KPa, x=92%
Turbine and pump actual process are assumed adiabatic

Find turbine inlet state: Pinlet, Tinlet, Sinlet

Homework Equations


W = ΔH
h = hf + xhfg

The Attempt at a Solution


I find hexit = hf + 0.92hfg

where hf = hf @ 40KPa = 317.62 on sat. liquid table and hfg=2318.4. So then I find hexit = 2450.18 kj/kg.

Then I do Wturbine = h1 - h2' to find h1 = hinlet = 8636.1 kj/kg. I then tried to look up that h on the superheated table to find the pressure and temperature and stuff but that's way too high of a number. I need help!
 
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Magnawolf said:
Then I do Wturbine = h1 - h2' to find h1 = hinlet = 8636.1 kj/kg. I then tried to look up that h on the superheated table to find the pressure and temperature and stuff but that's way too high of a number. I need help!

How? Where did you get Wturbine ? (units of kW/kg/s) You don't have a a mass flow rate to find Wturbine.
Have you included the entire problem statement?
 

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