Determine the time rate at which heat is supplied to the engine

  • #1

Homework Statement


a heat engine consists of an oil fired steam turbine driving an electric power generator with a power output of 120 megawatts. the efficiency of the heat engine is 40 percent. How do determine the time rate at which heat is supplied to the engine?


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The Attempt at a Solution


Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
dynamicsolo
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To get help at the Homework Forum, you have to show your attempt to solve the problem first. So the first thing to start with would be:

We know the efficiency of the engine is 40% = 0.4. What is the definition of efficiency for a heat engine?
 
  • #3
my teacher didnt teach us how to do this so im completly lost
 
  • #4
dynamicsolo
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Have you been shown yet the equation

efficiency = (net work or energy output) / ( heat or energy input) ?

What would be the input and the output in your problem statement?
 
  • #5
The efficiency is 40%, the output is 120 megawatts. Therefore, to fine the (heat or energy input) i can just divide (Efficiency)/(network or energy output) to find the anwswer? Also, do i have to change 120 megawatts or can i just leave it?
 
  • #6
dynamicsolo
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1,648
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The efficiency is 40%, the output is 120 megawatts. Therefore, to fine the (heat or energy input) i can just divide (Efficiency)/(network or energy output) to find the anwswer?
Check your algebra: if you're solving for the input (heat supply to the engine), what should your quotient be?

Also, do i have to change 120 megawatts or can i just leave it?
You can just leave it. The same formula also work for power, since it is the rate at which work or energy is transferred:

efficiency = (net power output) / (power input)

Don't forget that, while efficiency is often expressed as a percentage, it must be used in the equations as a fraction. So the efficiency here is 0.4 .
 

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