Thermodynamics: An Engineering Approach 8th Edition

Published by McGraw-Hill Education
ISBN 10: 0-07339-817-9
ISBN 13: 978-0-07339-817-4

Chapter 4 - Energy Analysis of Closed Systems - Problems - Page 203: 4-84

Answer

$\dot{Q}=408.91\ kW$

Work Step by Step

Treating the system as static with $\Delta t=1\ min$, we get a closed system with a $2\ m$ long cylinder. The energy balance for the system is: $Q=\Delta U=mc(T_2-T_1)$ With the mass given by: $m=\rho.(L.\frac{\pi}{4}D^2 )$ Given $\rho=7833\ kg/m³, L=2\ m,\ D=0.08\ m$, the mass is $m=78.75\ kg$. Plugging in the values of: $c=0.465\ kJ/kg.K,\ T_2=700°C, T_1=30°C$: we get $Q=24,534.56\ kJ$ Since $\dot{Q}=\frac{Q}{\Delta t}$ $\dot{Q}=408.91\ kW$
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