N

Diagram A

Exit weir =2' _ Water rate = 25gpm per. foot of piate width Superficial air velocity c 2.6 ft/sec.

1 23456789 10 Number of rows of caps in direction of liquid flow Diagram B Fig. 16-6.

Higher air rates or foaming agents increased the apparent liquid height, but static pressure probes indicated that for these cases the density was approximately one-third that of the liquid for the main region of fluid flow just above the plate and on top of this layer there was a light froth containing essentially no liquid. Practically all the liquid flow was accounted for in the layer with the one-third normal density. The light froth did not appear to have a significant effect on the hydraulic gradient.

Klein correlated his data and that of other investigators on the basis of a Fanning-type friction equation.

where F = loss in head from inlet to exit calming sections, ft. f = friction factor Vf « velocity of liquid in foam, f.p.s.

= Qw/(p/L0b) Qw = liquid rate, lbs. per sec. Pf = density of foam, lbs. per cu. ft. L0 = foam height, ft. b = width of plate, ft. B = length of bubbling section, ft. gc = conversion constant = 32.2

The values of /' were calculated from the experimental data and correlated as a function of a modified Reynolds number, fie' = (:rhVfpf)/nf, where /¿/ = viscosity of foam. In making the correlation it was assumed (1) that the average foam density was one-third the density of the normal liquid, (2) that the viscosity of the foam, nf, was one-third the true viscosity of the liquid, and (3) that L0 was equal to two times the hydrostatic head in the outlet calming section. Thus,

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