FTFS Chap09 P160 - Chapter 9 Gas Mixtures and...

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Chapter 9 Gas Mixtures and Psychrometrics Review Problems 9-160 The molar fractions of constituents of air are given. The gravimetric analysis of air and its molar mass are to be determined. Assumptions All the constituent gases and their mixture are ideal gases. Properties The molar masses of O 2 , N 2 , and Ar are 32.0, 28.0, and 40.0 kg/kmol. (Table A-1). Analysis For convenience, consider 100 kmol of air. Then the mass of each component and the total mass are    kg 40 kg/kmol 40 kmol 1 kmol 1 kg 2,184 kg/kmol 28 kmol 78 kmol 8 7 kg 672 kg/kmol 32 kmol 21 kmol 21 Ar Ar Ar Ar N N N N O O O O 2 2 2 2 2 2 2 2       M N m N M N m N M N m N m m m m m O N Ar 2 2 kg 2,184 kg 40 kg 2,896 kg 672 Then the mass fraction of each component (gravimetric analysis) becomes mf m m mf m m mf m m m m m O O N N Ar Ar 2 2 2 2 672 kg 2,896 kg 0.232 or 2,184 kg 2,896 kg 0.754 or 40 kg 2,896 kg 0.014 or 23.2% 75.4% 1.4% The molar mass of the mixture is determined from its definitions, M m N m m m 2,896 kg 100 kmol 28.96 kg / kmol 9-103 AIR 21% O 2 78% N 2 1% Ar
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Chapter 9 Gas Mixtures and Psychrometrics 9-161 Using EES (or other) software, a program is to be written to determine the mole fractions of the components of a mixture of 3 gases with known molar masses when the mass fractions are given, and to determine the mass fractions of the components when the mole fractions are given. The program is to be run for a sample case, and the results are to be listed. Procedure Fractions(Type$,A$,B$,C$,A,B,C:mf_A,mf_B,mf_C,y_A,y_B,y_C) {If Type$ <> ('mass fraction' OR 'mole fraction' ) then Call ERROR('Type$ must be set equal to "mass fraction" or "mole fraction".') GOTO 10 endif} Sum = A+B+C If ABS(Sum - 1) > 0 then goto 20 MM_A = molarmass(A$) MM_B = molarmass(B$) MM_C = molarmass(C$) If Type$ = 'mass fraction' then mf_A = A mf_B = B mf_C = C sumM_mix = mf_A/MM_A+ mf_B/MM_B+ mf_C/MM_C "[kJ/kmol]" y_A = mf_A/MM_A/sumM_mix y_B = mf_B/MM_B/sumM_mix y_C = mf_C/MM_C/sumM_mix GOTO 10 endif if Type$ = 'mole fraction' then y_A = A y_B = B y_C = C MM_mix = y_A*MM_A+ y_B*MM_B+ y_C*MM_C "[kJ/kmol]" mf_A = y_A*MM_A/MM_mix mf_B = y_B*MM_B/MM_mix mf_C = y_C*MM_C/MM_mix GOTO 10 Endif Call ERROR('Type$ must be either mass fraction or mole fraction.') GOTO 10 20: Call ERROR('The sum of the mass or mole fractions must be 1') 10: END "Either the mole fraction y_i or the mass fraction mf_i may be given by setting the parameter Type$='mole fraction' when the mole fractions are given or Type$='mass fraction' is given" {Input Data in the Diagram Window} {Type$='mole fraction' A$ = 'N2' B$ = 'O2' C$ = 'Argon' A = 0.71 "When Type$='mole fraction' A, B, C are the mole fractions" 9-104
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Chapter 9 Gas Mixtures and Psychrometrics B = 0.28 "When Type$='mass fraction' A, B, C are the mass fractions" C = 0.01} Call Fractions(Type$,A$,B$,C$,A,B,C:mf_A,mf_B,mf_C,y_A,y_B,y_C) SOLUTION Variables in Main A=0.71 A$='N2' B=0.28 B$='O2' C=0.01 C$='Argon' mf_A=0.680 mf_B=0.306 mf_C=0.014 Type$='mole fraction' y_A=0.710 y_B=0.280 y_C=0.010 9-105
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Chapter 9 Gas Mixtures and Psychrometrics 9-162
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This homework help was uploaded on 04/18/2008 for the course EML 3007 taught by Professor Chung during the Spring '08 term at University of Florida.

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FTFS Chap09 P160 - Chapter 9 Gas Mixtures and...

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