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 5 - Mass and Energy Analysis of Control Volumes - Problems - Page 260: 5-96

Answer

$\dot{Q}_s=63\ W$

Work Step by Step

The flowrate is given by: $\dot{m}=\frac{P_1\dot{V}_1}{RT_1}$ Given $P_1=101.325\ kPa,\ \dot{V}_1=0.6\ m³/min,\ R=0.287\ kJ/kg.K,\ T_1=30°C$: $\dot{m}=0.70\ kg/min$ From the energy balance: $\dot{Q}_a+\dot{m}h_1=\dot{m}h_2$ $\dot{Q}_a=\dot{m}c_p(T_2-T_1)$ and since $T_2=40°C,\ c_p=1.005\ kJ/kg.C$: $\dot{Q}_a=0.117\ kW=117\ W$ Therefore: $\dot{Q}=\dot{Q}_a+\dot{Q}_s,\ \dot{Q}=180W$: $\dot{Q}_s=63\ W$
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