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Steam turbine physics problem

  • Thread starter name_ask17
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  • #1
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Homework Statement


A steam turbine takes vapor at 463 deg c and exahusts it to a steam boiler at 238 deg c. the turbine then recieves a steam from the boiler at this temperature and exhausts it to a condenser at 38 deg c. what the is the maxumim efficiency of this combination.



Homework Equations


honestly, i am not sure what equation to use. i tried efficiency=work/Q but then i have unknown variables.



The Attempt at a Solution


(under relevant equations) all i am sure of s that i have to convert to kelvin, which makes the new temperatures 736, 511, and 311 respectivley.
 
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Answers and Replies

  • #2
Zryn
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C and K both increase at the same rate (C + 273 = K, i.e. +1C = +1K), so you should be able to use either in your calculations. You should be wary of F however, which has a rate of 9/5C (F = 9/5C + 32, i.e. +1C = +9/5F) and always change F to either C or K.

*Bum Steer.

Check the maximum efficiency engine efficiency formula , and assume that the entire process is one giant engine.
 
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  • #3
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yes but how does that help me find efficiency?
 
  • #4
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im still a bit confused
 
  • #5
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would i still use the equation i stated above?
Will someone please help me one this? i really need help before tomorrow. its not like im cheating anything... i have the answer but i have a test on this and i dont know how to get to the answer. i want to learn it. will someone please help?
 
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  • #6
Andrew Mason
Science Advisor
Homework Helper
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Homework Statement


A steam turbine takes vapor at 463 deg c and exahusts it to a steam boiler at 238 deg c. the turbine then recieves a steam from the boiler at this temperature and exhausts it to a condenser at 38 deg c. what the is the maxumim efficiency of this combination.
What kind of a (theoretical) heat engine gives maximum efficiency? What does the efficiency of this type of engine? Assume that the turbine is that kind of engine.

AM
 
  • #7
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the answer should be 91.8%
 
  • #8
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should i refer to the carnot engine?
 
  • #9
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if it is the carnot engine, i would use the equation T(hot)-T(cold)/T(hot). but in the problem, there are three different temperatures. which ones do i use?
 
  • #10
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nevermind i got it(: thanks !
 

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