1. Convective Mass Transfer Coefficient
Dr. Mustafa Nasser

2. Thus, for constant total concentration, The diffusion flux
Mass Transfer Coefficients
Defined as the rate of mass transfer per unit area per unit concentration difference based on equal molar flows.
Depends on (in liquids or gases) diffusivity, face of the component, physical properties (density and viscosity) of the fluid, distance of diffusion and type of diffusion (equimolar diffusion or diffusion of A through B)
Thus, for constant total concentration, The diffusion flux
(1)
Dr. Mustafa Nasser

3. Mass Transfer Coefficients
Integrating & rearranging,
Distance of the path, (z2 – z1) is often not know, thus
(2)
(3)
Convective mass transfer coefficient
Dr. Mustafa Nasser

4. Mass Transfer Coefficients
Case: equimolar counter diffusion
For the case of equimolar counter diffusion,
where NA = -NB, integrating at steady state,
where
(4)
(5)
Dr. Mustafa Nasser

5. Dr. Mustafa Nasser

6. Mass Transfer Coefficients
case of diffusion of A through stagnant B
For liquid
Dr. Mustafa Nasser

7. Mass Transfer Coefficients
Dr. Mustafa Nasser

8. ( with d = z2 – z1 ; )
Dr. Mustafa Nasser

9. Dr. Mustafa Nasser

10. Types of Mass Transfer Coefficients
And driving force expressed
Dr. Mustafa Nasser

11. Dr. Mustafa Nasser

12. Typical Magnitudes of Mass Transfer Coefficient and Film Thickness
Dr. Mustafa Nasser

13. Example
Dr. Mustafa Nasser

14. Dr. Mustafa Nasser

15. Dr. Mustafa Nasser