HomeworkSolutions_C12 - Homework Set # 12: Shell mass/molar...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Homework Set # 12: Shell mass/molar balance for components in a multi- component system Problem #1: Recall the example of evaporation of component A contained in a test tube in the lecture note (or see section 18.2, 2 nd edition, 17.2, 1 st edition). (a) By neglecting the convective flux of component A, show that this leads to () 1 12 21 AA zz cD Nx = =− A x (b) What error is made in the determination of D in the example 18.2-2 (or 17.2-2, 1 st edition) if the result in (a) is used? Answer: a. Without the convection term, the total molar flux of A is equal to the diffusion flux of A. For steady state . A A dx N cD const dz = Since c and D are constant, thus ( ) . A x x dx const dz z z == Therefore, 1 cD = A x b. Error in the determination of D in the example 18.2-2 To get the solution of Example 18.2-2 by using the result in (a), we make the following calculation with the help of the equation of state for an ideal gas. ( )( )( )( ) ( ) 9 2 7.26 10 82.06 273 17.1 0.0641 / / / 755/760 33/755 0 Az Az NR T N Dc c dx dz p dx dz × = = −− ⎡⎤ ⎣⎦ m s Hence the error is % 79 . 0 100 0636 . 0
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/01/2011 for the course PGE 312 taught by Professor Peters during the Fall '08 term at University of Texas at Austin.

Page1 / 3

HomeworkSolutions_C12 - Homework Set # 12: Shell mass/molar...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online