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 17 - Compressible Flow - Problems - Page 889: 17-7

Answer

$72.4$ kPa

Work Step by Step

The stagnation temperature of air is determined from $$ T_0=T+\frac{V^2}{2 c_p}=238 \mathrm{~K}+\frac{(325 \mathrm{~m} / \mathrm{s})^2}{2 \times 1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}}\left(\frac{1 \mathrm{~kJ} / \mathrm{kg}}{1000 \mathrm{~m}^2 / \mathrm{s}^2}\right)=290.5 \cong \mathbf{2 9 1 K} $$ Other stagnation properties at the specified state are determined by considering an isentropic process between the specified state and the stagnation state, $$ P_0=P\left(\frac{T_0}{T}\right)^{k /(k-1)}=(36 \mathrm{kPa})\left(\frac{290.5 \mathrm{~K}}{238 \mathrm{~K}}\right)^{1.4 /(1.4-1)}=72.37 \mathrm{kPa} \cong 72.4 \mathrm{kPa} $$
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