Assignment #2
(Due Feb 10, 2012)
Question 1 (5 marks)
Acetone in the bottom of a narrow metal tube is held at a constant temperature of 25C.
The total pressure of dry air out of this tube is 1.0 atm and 25C. Acetone evaporates and
diffuses through the air
Assignment #2
(Due Feb 10, 2012)
Question 1 (5 marks)
Acetone in the bottom of a narrow metal tube is held at a constant temperature of 25C.
The total pressure of dry air out of this tube is 1.0 atm and 25C. Acetone evaporates and
diffuses through the air
2.3 Unsteady Diffusion
2.3.1 Unsteady diffusion in a semi-infinite slab
Physical situation (1-dimensional diffusion)
Mass balance on a thin layer of volume Az
solute accumulation = rate of diffusion - rate of diffusion out
in volume Az
into the layer at
2.2 Steady Diffusion
Physical situation
Mass balance on a thin layer z
solute
= rate of diffusion
accumulation
into the layer at z
c10
- rate of diffusion out
of the layer at z+z
Because the process is steady state, the accumulation item at the left
han
Assignment #1
Question 1 (3 marks)
We have steady state diffusion of 1-propanol across a thin water film with a thickness of
0.1 mm. On one side of the film the 1-propanol concentration is 20 mol/m3. We desire a
1-propanol flux rate of 3.310-5 mol/m2-s. T
Chapter 1 Introduction
1.1 Basic concepts
1.2 Review of thermodynamics
1.1 Basic Concepts
Mass transfer phenomena
Case 1: what can you see when you add one drop of dark blue ink into a cup of
water without stirring?
Color change of water, mixing of the
1.2 Basic Thermodynamics
Ideal gas, ideal liquid solutions
Ideal gas law
Equation of state models, p-v-T relationship
Apply only at near-ambient pressure, up to 345 kPa.
For single component pv = nRT, R is the universal gas constant
For mixture: c i
2.4 Diffusion with Convection
Introduction
Convection is also a major mode of mass transfer in fluids
Convection is the transfer of mass by the physical movement of the fluid
Diffusion and convection always occur together
Combination of diffusion and conv
4.2 Mass Transfer Theories
In the Mass Transfer Coefficient approach, effects of forced convection and
diffusion are lumped into one parameter (k)
Several theories of mass transfer have been proposed, which have helped us
to understand how k is related
3.3 Diffusion Coefficients in Porous Solids
Classification of porous solids by their functions
Catalysts
metal impregnated alumina
zeolites
Adsorbents
activated carbon
activated alumina
silica gel
zeolites
Classification by pore size (IUPAC classifica
3.2 Diffusion Coefficients in Liquids
3.2.1 Diffusion in nonelectrolyte solutions
Molecular theory of the liquid state, as it stands today, does not allow
prediction of diffusion coefficient with the same degree of confidence possible
for dilute gas syste
2.4 Diffusion with Convection
Equimolar counterdiffusion
For binary system, the molar fluxes of A and B are equal but opposite in
direction, thus N=NA+NB=0
As NA=xAN+JA
NB=xBN+JB
Assuming total concentration is a constant, we have
dx A
dz
dx
N B J B cDB
Assignment #1
(Due Feb 3, 2012)
Question 1 (3 marks)
We have steady state diffusion of 1-propanol across a thin water film with a thickness of
0.1 mm. On one side of the film the 1-propanol concentration is 20 mol/m3. We desire a
1-propanol flux rate of 3
Tutorial Problem Set #1
1. Complete the followings:
(a) What is the density of air at 25 and 1 bar? The molecular weight of air is 29 g/mol.
(b) Calculate the volume of 0.5 kmol of any ideal gas at 15.6C and 1.2 bar.
Note: R=8.314Jmol-1K-1=8.314 m3Pamol-1
Tutorial Problem Set 3
1. Oxygen diffuses through the pores of a 2mm thick piece of unglazed porcelain at a total
pressure of 0.1 atm and a temperature of 293K. The average pore size is 0.3 um, the porosity
is 0.305 and the tortuosity is 4.39. It is obser
Tutorial Problem Set #2
1. Find a steady state flux of a pipe with a porous wall. The pipe has an inner radius Ri and Ro. the solute has a fixed, finite concentration c1i inside of the pipe, but is essentially at zero concentration outside. As a result, s