For vapor flow

The term in equation 42 is called a Souders-Brown capacity parameter and is based on the tendency of the upflowing vapor to entrain Hquid with it to the plate above. The term E in equation 43 is called an E-factor. and E to be meaningful the cross-sectional area to which they apply must be specified. The capacity parameter is usually based on the total column cross section minus the area blocked for vapor flow by the downcomer(s). Eor the E-factor, typical operating ranges for sieve plate columns are... 

Slotted plate for catalyst support designed with openings for vapor flow Ion exchanger fibers (reinforced ion exchange polymer) used as solid-acid catalyst None specified Hydrolysis of methyl acetate Evans and Stark, Eiir. Pat. Appl. EP 571,163 (1993) Hirata et al., Jap. Patent 05,212,290 (1993)... 

The first step in sizing a PR valve for vapor flow is to determine the critical flow pressure P from the following equation ... 

To derive formula (4.318) for vapor flow in a porous material, we approximate the pressure gradient in Eq. (4.318) with... 

Figure 4-64A. Adjustable floating" caps for vapor flow. By permission, Koch Engineering Co., Inc.

The slot opening is the vertical opening available for vapor flow during operation of the cap under a given set of conditions. It has been found to be essentially independent of surface tension, viscosity and depth of liquid over... 

The values of liquid gradient read from these charts are uncorrected for vapor flow. This correction is a multiplier read from Figure 8-113. 

Figure 8-129. Discharge coefficients for vapor flow, sieve trays. Used by permission, Smith, B. O., Design of Equilibrium Stage Processes, Chapter 15, by J. R. Fair, McGraw-Hill Book Co. (1963) data from I. Liebson, R. E. Kelley, and L. A. Bullington, Petroleum Refiner, V. 36 (2), Feb. (1957) p. 127 V. 36 (3), (1957) pg. 288, all rights reserved.

An = Net cross-section area for vapor flow above tray,... 

Coalescing flow map for vaporizing flows in micro-channels... 

Fig. 2.32 Diabatic flow pattern map for vaporizing flow in uniformly heated micro-channel, R-134a, d = 0.5 mm, L = 70 mm, Tg = 30 °C, = 50 kW/m without subcooling at inlet. Flow patterns isolated bubble regime (IB), coalescing bubble regime (CB), annular (completely coalesced) regime (A), post-dryout regime (PD). Reprinted from Thome et al. (2006) with permission...

For vapor flows that are not choked by sonic flow the area is determined using Equation 4-48. The downstream pressure P is now required, and the discharge coefficient C0 must be estimated. The API Pressure Vessel Code4 provides working equations that are equivalent to Equation 4-48. 

The apparent velocity, t 4, is related to the fraction of area covered by liquid, t. The liquid-free surface for vapor flow is, therefore, 1 —<), with. 4, being the total surface area of the impingement pad. And the apparent velocity becomes ... 

In a trayed tower, the area used for the downcomer which feeds liquid to a tray, and the area used for draining liquid from a tray, are unavailable for vapor flow. In a packed tower, the entire cross-sectional area of the tower is available for vapor flow. 

FA = fractional free area available for vapor flow. 

Bubbling area AB (also called active area) The total tower cross-sectional area minus the sum of downcomer top area Apr, downcomer seal area ADB, and any other nonperforated areas on the tray. The bubbling area represents the area available for vapor flow just above the tray floor. 

Slot area As The total (for all open valves) vertical curtain area through which vapor passes in a horizontal direction as it leaves the valves. It is a function of the narrowest opening of each valve and the number of valves that are open. The slot area is normally the smallest area available for vapor flow on a valve tray. 

Waddington, G., Smith, J.C., Williamson, K.D., Scott, D.W. (1962) Carbon disulfide as a reference substance for vapor-flow calorimetry the chemical thermodynamic properties. J. Am. Chem. Soc. 66, 1074—1077. 

Recently there has been an increasing trend to replace the conventional trays depicted in Fig. 5 by trays having receiving pans that terminate some 15 cm above the tray deck. This provides more column cross-sectional area for vapor flow and allows increased vapor capacity. Even greater vapor capacity can be obtained from trays that utilize localized, upward co-current flow of vapor and liquid. But, as each tray then requires a vapor-liquid separation device, they are more expensive and are used only in specialized applications. 

Net area, AN the total tower cross-section area A less the area at the top of the downcomer (sometimes referred to as free area the term free area has been used inconsistently in the literature). The net area represents the smallest area available for vapor flow in the intertray spacing. 

Effect of column diameter (at constant UV and percent of flood). As column diameter increases, both the liquid and vapor flow rates increase as the square of the diameter. The area for vapor flow also increases as the square of the diameter, so the vapor load remains unaffected. On the other hand, the area available for liquid flow only increases in proportion to the diameter. Therefore, the liquid rate per unit of weir length increases, the increase being proportional to the column diameter. The operating point on Fig. 6.29 will therefore shift horizontally to the right, toward the emulsion regime. Increasing the number of liquid passes on the tray reverses the above action, and shifts the operating point back to the left. 

Cross-sectional areas for vapor flow through riser, direction-reversal space, annular cap space, and slots are equal. 

Vc = linear velocity of gas in riser, reversal area, or annulus of bubble cap (maximum value) or in sieve hole, ft/s = maximum allowable superficial linear velocity of gas (based on net cross-sectional area of tower for vapor flow), ft/s, see Eq. (3)... 

Next, the Fc value is used in calculating required free area for vapor flow, via the relation... 

Slotted plate for catalyst support designed with openings for vapor flow None specified Evans and Stark, Eur. Pat. Appl. EP 571,163 (1993)... 

The relationship between the area for vapor flow, A and the height above the liquid level, hp, can been found from tables giving the dimensions of the segments of circles see Perry et al. (1997), or from Figures 11.34 and 11.35 in Chapter 11. 

Cross-sectional area for vapor flow = x 0.5 = 0.393D ... 

As the area for vapor flow varies with the flow rate, valve plates can operate efficiently at lower flow rates than sieve plates, the valves closing at low vapor rates. 

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