Page 405 - Modelling in Transport Phenomena A Conceptual Approach

9.5. MASS TRANSFER WITH CONVECTION 385

From Table (3.8 in Appendix C, the non-zero mass flux components for species
A axe

dWA
WA, = - PDAB - (9.52)
a?.
dWA
WA. = -pDAB - +PA"% (9.53)
az
For a dilute liquid solution, the total density is almost constant and Eqs. (9.52)
and (9.53) become

(9.54)

+A +
WA. = - DAB - PAV~ (9.55)
dz
Dividing Eqs. (9.54) and (9.55) by the molecular weight of species A, MA, gives

(9.56)

dCA +
NA. = -DAB - CAV, (9.57)
a2
Since there is no generation of species A, Eq. (9.41) simplifies to
Rate of Rate of ) =o
( species A in ) - ( species A out (9.58)