Tutorial/HW Week #8

WRF Chapter 23; WWWR Chapters 25-26

ID Chapter 14

• Tutorial #8

• WWWR #25.6, #25.11, # 25.13, #26.4.

• E-Learning tutorial Session. To be discussed during the

week 19-23 March, 2018 by Webcast.

• By either volunteer or class list.

Special Forms

• Combining the flux equation with the

continuity equation,

BAAAABA D nnn

0

A

AAAAB r

tD

v

VN AAABA cycD

0

A

AAAAB R

t

ccycD V

• Assuming constant and DAB, we get

• Additionally, if there are no reactions, then

or

AAABA

A RcDt

cc

2

v

AABAA cDct

c 2

v

AABA cD

Dt

Dc 2

• And if there is also no fluid motion, v = 0,

Which is Fick’s second law of diffusion

• For steady state process, constant and

DAB,

AABA cDt

c 2

AAABA RcDc 2v

With no chemical reaction and no fluid

flow, becomes

which is the Laplace equation for molar

concentration.

02 Ac

Initial and Boundary Conditions

• Initial condition: e.g. t = 0, CA=CA0.

• Boundary condition:

• (a) The concentration of the transferring

species A at a boundary is specified.

• (b) A reacting surface boundary is specified.

Example 1

Example 2

Example 3

R2R2

R1

Review #2:

Convective Heat Transfer & Mass

Transfer Fundamentals

• Please Refer to Appendix 8.