Down flow pipe from plate above Fig. 16-13. Layout of bubble-cap plate.

Hydraulic Gradient. The section with the bubble caps approximates a rectangular section, and Eq. (16-16) will be employed for the calculation of the hydraulic gradient. The average foam velocity by Eq. (16-19) is

The value of b 4.6 feet was taken as the average of the diameter of the column md the width at the first row of caps. By Eq. (16-17),

ind from Eq. (16-18), using the viscosity of the liquid equal to 0.00067 (see p. 418),

Using this value with Fig. 16-7 gives

The loss in head is calculated from Eq. (16-16)

= 0.0061 ft. of toluene = 0.073 in. of toluene = 0.062 in. of water

The gradient for this plate is somewhat smaller than the assumed value of 0.1 in. of toluene. However, the difference is not large and no corrections will be made.

Pressure Drop through Caps.

1. Assume uniform vapor distribution with no gradient,

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