Maximum Power Output of a Turbine

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Discussion Overview

The discussion revolves around calculating the maximum power output of an adiabatic turbine using argon gas, focusing on the expansion process from high pressure and temperature to a lower pressure. Participants explore the necessary thermodynamic principles and assumptions required to solve the problem, particularly regarding state changes and energy equations.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant outlines the steps needed to find the maximum power output, emphasizing the need to determine the temperature at state two (T2) and the enthalpy at that state (h2).
  • Another participant suggests assuming the turbine operates under isentropic conditions, which is a common approach in thermodynamic problems involving turbines.
  • A different viewpoint argues against the notion that a closed system implies no temperature change, clarifying that an adiabatic process allows for temperature changes while preventing heat transfer.
  • There is a mention that turbines are typically treated as open systems, which may affect the assumptions made in the calculations.

Areas of Agreement / Disagreement

Participants express differing views on the assumptions regarding the system's nature (closed vs. open) and the implications for temperature changes during the adiabatic process. No consensus is reached on the correct approach to take in solving the problem.

Contextual Notes

Participants highlight the importance of assumptions in thermodynamic calculations, particularly regarding isentropic processes and system boundaries. The discussion reflects various interpretations of the problem's conditions, which may affect the solution.

thermohelp12
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Hi,
I need with the following question.

Argon gas expands in an adiabatic turbine from 3MPa and 750 C to .2 MPa at a rate of 5 kg/s. Neglect KE and PE effects. Find maximum power output.

I know I need to first find the temperature of state two and then use that to solve for h2 (I have already solved for h1) then plug it into W=mass flow rate(h1-h2) to solve for the work and go from there but I am having a problem finding T2. Any help would greatly be appreciated.
 
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Welcome thermohelp12,

I think you need to make the assumption that the turbine is isentropic.

P.S. There is a HW help section of the forums.
 
thermohelp12 said:
Hi,
I need with the following question.

Argon gas expands in an adiabatic turbine from 3MPa and 750 C to .2 MPa at a rate of 5 kg/s. Neglect KE and PE effects. Find maximum power output.

I know I need to first find the temperature of state two and then use that to solve for h2 (I have already solved for h1) then plug it into W=mass flow rate(h1-h2) to solve for the work and go from there but I am having a problem finding T2. Any help would greatly be appreciated.

I think h2oski1326 was right you need to consider the isentropic process because according to your problem the gas expands in adiabatic process, that means you have a closed sytem, and if the system is closed there is no cahange in temperature. you can solved h2 using temperature from h1.
 
rodeliocueva said:
I think h2oski1326 was right you need to consider the isentropic process because according to your problem the gas expands in adiabatic process, that means you have a closed sytem, and if the system is closed there is no cahange in temperature. you can solved h2 using temperature from h1.

Turbines are open systems (i.e. control volumes).

A closed system does not necessarily mean that there is not a temperature change. An adiabatic system means that no heat is transferred across the system boundary. This is a common assumption (in homework problems) with turbines since they are normally well insulated.

BTW, this thread is 5 months old.

CS
 

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