temperature, and water temperature throughout the diffusion tower. However, since a
one-dimensional model is utilized, closure must be achieved. This requires that both the
heat transfer coefficient and mass transfer coefficient be known. Directly measuring the
heat transfer coefficients is not possible because of the fact that the interfacial film
temperature cannot be measured. Therefore to overcome this difficulty the heat and mass
transfer analogy [19] has been utilized. The heat transfer coefficient for the liquid side is
evaluated using,
Nu, Sh
L (3.15)
Prl/2 Scl/2
L L
U, =k, pCPL L (3.16)
Similarly, the heat transfer coefficient for the gas side is calculated as,
NuG ShG
G (3.17)
PrG/3 ScG/3
UG k GPG1/ K (3.18)
where D is the molecular diffusion coefficient and K is the thermal conductivity. Thus
the overall heat transfer coefficient is evaluated as,
U, = (U,-+UG1) (3.19)
The mass transfer coefficient is evaluated using a widely known and well tested
correlation. Onda' s correlation [20] allows for evaluation of the mass transfer
coefficients in packed beds. Onda' s correlation, found in Appendix A, is used to
calculate the mass transfer coefficients, kG and kL. In the correlation the coefficient, C,
can take on two possible values C=5.23 for dp > 15 mm and C=2.00 for dp <;15 mm.