Percent opening area

For counterflow plates, the curves of Fig. 14-25 may be used for open areas of 20 percent or greater. Plates with 15 percent open areas have about 85 percent of the cui ve values, and open areas or less than 15 percent are not recommended. For counterflow-plate columns of the segmental-baffle type, 50 percent cut, allowable values are about 15 percent greater than tnose shown in Fig. 14-25, when vertical spacings of the baffles are equal to the trav spacings shown. 

Turbogrid plate—4.6-mm (0.18-in) slot width, 14.7 percent open area... 

Ripple plate—2.85-mm in) holes, 10.8 percent open area Efficiency data from the work are summarized in Fig. 14-40. 

Hole Size, Spacing, Percent Open Area... 

To avoid such flooding, the designer uses the corrugated bed support shown in Fig. 7.8. This grid will have over 100 percent open area. Crushed packing laying on even this excellent type of bed support can, however, cause flooding. 

The Karr reciprocating-plate column (Fig. 15-50) is a popular example. It uses dual-flow plates with 50 to 60 percent open area and has no downcomers [Karr, AlChE J., 5(4), pp. 446-452 (1959) Karr and Lo, Chem. Eng. Prog., 72(11), pp. 68-70 (1976) and Karr, AIChE J., 31(4), pp. 690-692 (1985)]. Because of the high open area, a Karr column may be operated with relatively high throughput compared to other types of agitated columns, up to about 1000 gaF(h ft ) [40 m /(h m )] depending upon the application. The plates are mounted... 

Percent Open Area = (Opening x Mesh Count) x 100... 

Plate efficiency is a function of the rate of mass transfer between liquid and vapor. The prediction of mass-transfer coefficients in sieve trays and their relationship to plate efficiency are discussed in Chap. 21. Some published values of the plate efficiency of a 1.2-m column are shown in Fig. 18.34. This column had sieve trays with 12.7-mm holes and 8.32 percent open area, a 51-mm weir height, and... 

A sieve-tray column with 15 plates is used to prepare 99 percent methanol from a feed containing 40 percent methanol and 60 percent water (mole percent). The plates have 8 percent open area, in. holes, and 2-in. weirs with segmental downcomers, (a) If the column is operated at atmospheric pressure, estimate the flooding limit based on conditions at the top of the column. What is the F factor and the pressure drop per plate at this limit (Z>) For the flow rate calculated in part (a) determine the F factor and the pressure drop per plate near the bottom of the column. Which section of the column will flood first as the vapor rate is increased ... 

Originally, the gas distributors in fluidized beds were made of perforated steel plates (see Fig. 7.70, top). The size of the holes, in most cases the diameter of circular bores, the percent open area, defined by the sum of all hole areas, sometimes the distribution pattern of the holes in the plate, and the gas pressure in the plenum below the distribution plate, which, together with the other dimensions, defined the gas flow rate, were major design parameters. To obtain a good, stable fluidized bed, the gas velocity has to be uniform across the entire area of the bed and must be adjusted such that, as a result, the solid particles are in a suspended state. 

Percent open area Corps of Engineers protocol CW02215... 

---