Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 15 - The Laws of Thermodynamics - Problems - Page 439: 26

Answer

$280^{\circ} C$.

Work Step by Step

The maximum efficiency (Carnot efficiency) is given by equation 15–5. Make sure to measure temperatures in kelvins. Find the intake temperature from the original Carnot efficiency. $$e_{ideal}=1-\frac{T_L}{T_H}$$ $$T_H=1-\frac{T_L}{1-e}=\frac{340+273K}{1-0.36}=958\;K$$ Now calculate the new low exhaust temperature for the desired Carnot efficiency of 0.42, using the intake temperature of 958 K. $$e_{ideal}=1-\frac{T_L}{T_H}$$ $$T_L=T_H(1-e)=(958K)(1-0.42)=556\;K\approx 280^{\circ} C $$
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