Question

cyclic heat engine draws 350 KJ heat from ?
a source at 1000 K. It supplies 125 KJ of
heat to the low temperature reservoir at
400 K and performs 225 KJ of work. Is this
machine reversible, irreversible, or
impossible ? Why ?

Answer 1

Answer on Question #43262-Physics-Molecular Physics-Thermodynamics

Cyclic heat engine draws 350 KJ heat from a source at 1000 K. It supplies 125 KJ of heat to the low temperature reservoir at 400 K and performs 225 KJ of work. Is this machine reversible, irreversible, or impossible? Why?

Solution

$$\eta_{Carnot} = 1 - \frac{T_L}{T_H} = 1 - \frac{400\,K}{1000\,K} = 0.6.$$ $$\eta_{Engine} = \frac{|Q_H| - |Q_L|}{|Q_H|} = \frac{225\, \text{KJ}}{350\, \text{KJ}} = 0.64.$$

This machine is impossible, because $\eta_{Engine} > \eta_{Carnot} = \eta_{MAX}$.

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