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 3 - Properties of Pure Substances - Problems - Page 157: 3-94

Answer

a) $P=1588.38kPa$ $(5.54\% error)$ b) $P=1494.71kPa$ $(0.68\% error)$ c) $P=1504kPa$ $(0.07\% error)$

Work Step by Step

a) Based on the ideal gas equation: $P=\frac{mRT}{V}=\frac{100kg*0.2968\frac{kPam^3}{kgK}*175K }{3.27m^3}=1588.38kPa$ $(5.54\% error)$ b) Using the Van Der Waals equation: $a=\frac{27R^2T_{cr}^2}{64P_{cr}}=\frac{27*(0.2968\frac{kPam^3}{kgK})^2*(136.2K)^2}{64*3390kPa}=0.175\frac{m^6kPa}{kg^2}$ $b=\frac{RT_{cr}}{8P_{cr}}=\frac{0.2968\frac{kPam^3}{kgK}*126.2K}{8*3390kPa}=0.00138\frac{m^3}{kg}$ $P=\frac{RT}{\upsilon-b}-\frac{a}{\upsilon^2}=\frac{0.2968\frac{kPam^3}{kgK}*175K}{\frac{3.27m^3}{100kg}-0.00138\frac{m^3}{kg}}-\frac{0.175\frac{m^6kPa}{kg^2}}{(\frac{3.27m^3}{100kg})^2}=1494.71kPa$ $(0.68\% error)$ c) Using the Beattie-Bridgeman equation $v=M\upsilon=28.013\frac{kg}{kmol}*\frac{3.27m^3}{100kg}=0.916\frac{m^3}{kmol}$ $A=A_{0}(1-\frac{a}{v})=136.2315*(1-\frac{0.02617}{0.916})=132.339$ $B=B_{0}(1-\frac{b}{v})=0.05046*(1-\frac{-0.00691}{0.916})=0.05084$ $c=4.2*10^4\frac{m^3K^3}{kmol}$ $P=\frac{R_{u}T}{v^2}(1-\frac{c}{vT^3})(v+B)-\frac{A}{v^2}=\frac{8.314*175}{0.916^2}(1-\frac{4.2*10^4}{0.916*175^3})(0.916+0.05084)-\frac{132.339}{0.916^2}$ $P=1504kPa$ $(0.07\% error)$
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