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: 17-5

Answer

$320.0$ K $320.1$ K $325.0$ K $817.5$ K

Work Step by Step

The air which strikes the probe will be brought to a complete stop, and thus it will undergo a stagnation process. The thermometer will sense the temperature of this stagnated air, which is the stagnation temperature, $T_0$. It is determined from $T_0=T+\frac{V^2}{2 c_p}$. The results for each case are calculated below: (a) $$ T_0=320 \mathrm{~K}+\frac{(1 \mathrm{~m} / \mathrm{s})^2}{2 \times 1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}}\left(\frac{1 \mathrm{~kJ} / \mathrm{kg}}{1000 \mathrm{~m}^2 / \mathrm{s}^2}\right)=\mathbf{3 2 0 . 0 K} $$ (b) $$ T_0=320 \mathrm{~K}+\frac{(10 \mathrm{~m} / \mathrm{s})^2}{2 \times 1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}}\left(\frac{1 \mathrm{~kJ} / \mathrm{kg}}{1000 \mathrm{~m}^2 / \mathrm{s}^2}\right)=\mathbf{3 2 0 . 1 K} $$ (c) $$ T_0=320 \mathrm{~K}+\frac{(100 \mathrm{~m} / \mathrm{s})^2}{2 \times 1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}}\left(\frac{1 \mathrm{~kJ} / \mathrm{kg}}{1000 \mathrm{~m}^2 / \mathrm{s}^2}\right)=\mathbf{3 2 5 . 0 K} $$ (d) $$ T_0=320 \mathrm{~K}+\frac{(1000 \mathrm{~m} / \mathrm{s})^2}{2 \times 1.005 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}}\left(\frac{1 \mathrm{~kJ} / \mathrm{kg}}{1000 \mathrm{~m}^2 / \mathrm{s}^2}\right)=\mathbf{8 1 7 . 5 K} $$
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