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Table 16. Coefficients of Eq. (116) for all considered systems, for positive and negative ones
Systems c« c 3 e 4
All systems 2.552 0.033 -0.239 0.306 0.290 -0.530
Positive* 25.462 -0.0065 -0.439 0.027 1.061 -2.50
Negative* 3.203 0.07H -0.394 0.387 0.136 2.45
* See Chapter 4.

Since the sizes of the investigated packings are very small, the
application of Eq. (116) for industrial calculations is not to be recommended.

3.2.1.2.1.5. Equation for calculation of the axial mixing coefficients

3.2.1.2.1.5.1. Axial mixing in the gas phase
In general, the dispersion of a gas flowing in a packed bed is considered
to be a result of two main mechanisms: molecular diffusion and eddy
(turbulent) diffusion. At low Reynolds number (ifee<l) the dispersion is
controlled by the molecular diffusion. At RgQ>\Q, the turbulent diffusion is a
dominant factor. Since all industrial packings operate at rather great values of
Re G, the molecular diffusion is not of importance for the axial mixing in the gas
phase.
Based on own data for Raschig rings 6-13 mm for the axial mixing in
the gas phase, De Maria and White [116] obtained the equations:

for dry packings

Pea = 1.94, (117)

for irrigated packings

(118)

where:

— - Peclet number for the gas phase;
Pe G=Bo G
a.H s(l-H d).a.D G
2
D G - axial mixing coefficient for the gas phase, m /s;