Heat engine

  • Thread starter kasse
  • Start date
  • #1
kasse
382
1

Homework Statement



A machine with COP = 5.0 removes 25kJ of heat from a cold reservoar. If the machine is reversible and driven the other way as a heat engine, what is the efficiency?

The Attempt at a Solution



COP = QL/W --> W = 5kJ

e = QH/W

Is QH the same as QL som that e = 20%
 

Answers and Replies

  • #2
alphysicist
Homework Helper
2,238
2
Hi kasse,

No, I don't believe that [itex]Q_H[/itex] and [itex]Q_L[/itex] are the same. Using conservation of energy, you can find out how Qh, QL, and W are related. What do you get?

Also, your efficiency formula needs to be:

[tex]
e=\frac{W}{Q_H}
[/tex]
 

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