This document discusses methods for obtaining the overall mass transfer coefficient in packed columns. It presents experimental data for oxygen-water systems using ceramic rings of different diameters. For 1/2 inch rings, the height of transfer coefficient is proportional to the liquid mass velocity to the power of 0.4. For larger rings, it is proportional to liquid mass velocity to the power of 0.2. The relationship between height of transfer coefficient and liquid mass velocity changes with ring diameter. The document also provides equations that can be used to calculate the liquid film resistance for other systems based on differences in diffusivity and viscosity.

2. Mohammad Zia Ullah
Department of Chemical and Polymer Engineering
University of Engineering and Technology , Lahore(Fsd
Campus)
muhammadzia7272@gmail.com

3. • To obtain
overall mass transfer coefficient
height of a transfer coefficient
• Based on experimental data obtained from certain
arrangements and then generalized for all systems.

5. • This experimental data for O2-H2O with ceramic rings
shown in fig.
• Relationship between Hox and Gx(liq mass velocity)
changes with dia of rings
• For ½ inch rings:
Hx α Gxⁿ n=0.4
• For larger rings:
Hx α Gxⁿ n=0.2

6. • At high mass velocities Hx is nearly proportional to the
Gx.
• The liquid film resistance for other systems can be
calculated by correcting differences in diffusivity and
viscosity.
• The relation is

7. • Where ‘α’ and ‘n’ are empirical constants
given in literature for different packing types.
• The exponent 0.5 on schmidt number is obtained from
penetration theory.
• ‘n’ varies with packing size and packing type but typical
value is taken 0.3.

8. • Molecular weight have no net effect on coefficient.
• The coefficient mainly depends upon flow rate, diffusivity
and viscosity.