1. Correlation of Mass Transfer Coefficient
Dan Duffield
Rick Pelletier

2. Mass Transfer Coefficient, km
Correlated using-
where x = constant
Figure 5 shows the plot of the present data by the relation of log(Sh/Sc1/3) vs. log(Re)
All data points fall on the straight line defined by-

3. Comparison to Previous Results
Smith et al. (1968)
Batch dialyzer agitated by a four-blade impeller rotating parallel to the membrane.
0.634 < m < 0.752
Dependent on system geometry
Kaufmann and Leonard (1968)
Similar diffusion cell
m = 0.68

4. Comparison to Previous Results (cont.)
Colton and Smith (1972)
Flat-bottom tank agitated by a four-blade paddle impeller.
0.567 < m < 0.746
At low and high Re, respectively.
Holmes et a. (1963)
Diaphragm diffusion cell
Sh = Re0.79 Sc0.38

5. Comparison to Previous Results (cont.)
Due to difference in cell design, the correlation obtained in this study may not be compared directly with the results reported previously.
Can be concluded that the exponent value on Re is varied from 0.5 to 1.0, dependent on the design of in vitro membrane permeation systems.
Under turbulent flow conditions, the exponent m on Re was reported to be 0.9 to 1.0.

6. Diffusion Boundary Layer Characteristics
km for current diffusion cell 50% greater than that studied by Keshary & Chien with same driving unit
When correlation is adjusted for differences in design there is excellent agreement between diffusion cell correlations

7. Diffusion Boundary Layer Characteristics
Correlation can be used to evaluate diffusion boundary layer thickness
Volume Fraction of PEG 400 in water 0%
10%
20%
40%
dn, µm
50.0
57.2
70.4
98.0

8. Diffusion Boundary Layer Characteristics
Correlation can be used to analyze effect of hydrodynamic diffusion layer on rate controlled drug release

9. Questions ?