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 890: 17-20

Answer

$ c_{1} = 342.9 m/s$ $ Ma_{1} = 0.292$ $T2 = 111C^o = 384K$ $ c_{2} = 399m/s$ $Ma2 = 0.501$

Work Step by Step

The gas const $R = 0.2968 KJ/(KG.K)$ The specific heat at constant pressure at constant temperature, $c_{p} = 1.040 KJ/(KG.K) $ Specific heat ratio , $K =1.4$ we have $c_{1} = \sqrt (K1RT1)$ Substituting the values $ c_{1} = \sqrt(1.4 KJ/(KG.K) x 0.2968 KJ/(KG.K) x 283K x ((1000m2/s2)/(1KJ/Kg))$ on solving we get $ c_{1} = 342.9 m/s$ We have $ Ma_{1} = v_{1}/c_{1} = (100 m/s)/(342.9 m/s) = 0.292$ We have the equation $Q_{in} = c_{p}(T_{2}-T_{1}) + (v_{2}^2-v_{1}^2)/2$ given ,$ v_{2}=200m/s^2$, $v_{1}= 100m/s^2$, $Q_{in} = 120KJ/Kg$, T1= $10C^o$ substituriong the values we get $120 Kj/kg = 1.040Kj/Kg C^o(T2 - 10C^o) + (((200 - 100)m/s2)/2 x ((1KJ/Kg)/(1000m2/s2)))$ $T2 = 111C^o = 384K$ we have $c_{2} = \sqrt(K2RT2)$ substituting the vaues $c_{2} = \sqrt(1.4 KJ/(KG.K) x 0.2968 KJ/(KG.K) x 384K x ((1000m2/s2)/(1KJ/Kg))$ we get $ c_{2} = 399m/s$ similarly $Ma2 = v_{2}/c_{2}= (200 m/s)/(3399 m/s) = 0.501$
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