Page 51 - Modelling in Transport Phenomena A Conceptual Approach
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32 CHAPTER 2. MOLECULAR AND CONVECTIVE TRANSPORT
where the total molarflvsc of species A at the interface, NA,~~=o, given by
is
By the application of the chain rule, Eq. (2) takes the form
On the other hand, the term dcAldq can be calculated by the application of the
Leibnitz formula, ie., Eq. (A.4-3) in Appendix A, as
Substitution of Eqs. (4) and (5) into Eq. (3) yields
Finally, the we of Eq. (6) in Eq. (1) gives the molar rate of transfer of species A
2.4.2 Rate of Energy Entering and/or Leaving the System
The rate of energy entering and/or leaving the system, E, is expressed as
Gradient of
Energy/Volume
L Molecular energy flux
+ (Energy) ( Characteristic )] ( Fhg ) (2.415)
Volume velocity
\ .. /
Convective energy flux
As in the case of mass, energy may enter or leave the system by two means:
