Velocity outlet

Capacity Outlet velocity Outlet velocity pressure Ratings at 6.5 inH20 (1.6 kPa) static pressure ... 

A lip is attached to the entrance or ihe omlet Slack to caose liquid running down the outside of the onitet pipa to drop through the separator away from (he high-velocity outlet gas vortex. 

Typically the exit velocity in a flow domain is unknown and hence the prescription of Dirichlet-type boundary conditions at the outlet is not possible. However, at the outlet of sufficiently long domains fully developed flow conditions may be imposed. In the example considered here these can be written as... 

The most common mobile phases for GC are He, Ar, and N2, which have the advantage of being chemically inert toward both the sample and the stationary phase. The choice of which carrier gas to use is often determined by the instrument s detector. With packed columns the mobile-phase velocity is usually within the range of 25-150 mF/min, whereas flow rates for capillary columns are 1-25 mF/min. Actual flow rates are determined with a flow meter placed at the column outlet. 

Normally vessels are designed with the gas outlet location well above TDH. If circumstances force operation with a bed height so that the outlet is below TDH, an equivalent velocity, an effective velocity higher than the actual superficial gas velocity, is used ia the above calculation. The effective gas velocity can be determined from Figure 19 (27). 

The first bracketed term represents the pressure difference between the inlet and oudet no22les resulting from the difference in fluid velocity, acceleration or momentum, and the second bracketed term represents the pressure difference between the inlet and outlet no22les from the difference in elevation. 

A distributor is frequently installed at the top of the column for use during backwash. It collects water evenly and prevents resin from escaping the column should unexpected surges develop in the water flow during backwash. Columns lacking an upper distributor or screen to prevent loss of resin should have an external system to prevent resin from being lost to the drain. It is referred to as a resin trap and may consist of a porous bag that fits over the outlet pipe or a tank designed to lower the linear velocity. Resin drops to the bottom of the tank and is returned to the column when convenient. 

BI SERT Blenders. The design of a BINSERT blender consists of a hopper-within-a-hopper, both of which ate usually conical ia shape (Fig. 15). Particles flow through the inner hopper as well as through the annulus between the inner and outer hoppers. By varyiag the relative position of these two hoppers as well as the configuration of the outlet geometry, it is possible to achieve between a 5 1 and 10 1 velocity differential between particles ia the inner hopper compared to particles ia the outer annular region (7,17). 

The heating surface usually determines the evaporator cost and the vapor head the space requirements. The vapor—Hquid separator must have enough horizontal plan area to allow the bulk of the initial entrainment to settle back against the rising flow of vapor and enough height to smooth out variations ia vapor velocity and to prevent splashing directly iato the vapor outlet. Separators are usually sized on the basis of the Souders-Brown expression ... 

Simplified forms of Eq. (6-8) apply to special cases frequently found in prac tice. For a control volume fixed in space with one inlet of area Ai through which an incompressible fluid enters the control volume at an average velocity Vi, and one outlet of area Ao through which fluid leaves at an average velocity V9, as shown in Fig. 6-4, the continuity equation becomes... 

Here g is the gravity vector and tu is the force per unit area exerted by the surroundings on the fluid in the control volume. The integrand of the area integr on the left-hand side of Eq. (6-10) is nonzero only on the entrance and exit portions of the control volume boundary. For the special case of steady flow at a mass flow rate m through a control volume fixed in space with one inlet and one outlet, (Fig. 6-4) with the inlet and outlet velocity vectors perpendicular to planar inlet and outlet surfaces, giving average velocity vectors Vi and V9, the momentum equation becomes... 

Selecting the inlet and outlet surfaces 1 and 2 as shown, the continuity equation Eq. (6-9) can he used to find the exit velocity V2 = ViAi/A2. The mass flow rate is obtained by m = pViAi. 

Volute casings take the form of a spiral increasing uniformly in cross-sectional area as the outlet is approached. The volute efficiently converts the velocity energy imparted to the liquid by the impeller into pressure energy. 

Induced-draft design provides more even distribution of air across the bundle, since air velocity approaching the bundle is relatively low. This design is better suited (or exchangers designed for a close approach of product outlet temperature to ambient-air temperature. 

In a submerged-tube FC evaporator, all heat is imparted as sensible heat, resulting in a temperature rise of the circulating hquor that reduces the overall temperature difference available for heat transfer. Temperature rise, tube proportions, tube velocity, and head requirements on the circulating pump all influence the selec tion of circulation rate. Head requirements are frequently difficult to estimate since they consist not only of the usual friction, entrance and contraction, and elevation losses when the return to the flash chamber is above the liquid level but also of increased friction losses due to flashing in the return line and vortex losses in the flash chamber. Circulation is sometimes limited by vapor in the pump suction hne. This may be drawn in as a result of inadequate vapor-liquid separation or may come from vortices near the pump suction connection to the body or may be formed in the line itself by short circuiting from heater outlet to pump inlet of liquor that has not flashed completely to equilibrium at the pressure in the vapor head. 

FIG. 14-24 Performance of two crossflow plates operating at 0.13 bar pressure and total reflux. Test mixture etbylbenzene/styrene. Spacing between plates is 0.50 m, and outlet weir height is 38 mm. Ut = superficial vapor velocity, pc = vapor density. [Billet, Comad, and Giuhh, I. Chem. E. Symp. Ser. No. 32, 5, 111 (1969).]... 

In design of separating chambers, static vessels or continuous-flow tanks may be used. Care must be taken to protect the flow from turbulence, which coiild cause back mixing of partially separated fluids or which could cany unseparated hquids rapidly to the separated-hquid outlet. Vertical baffles to protect rising biibbles from flow currents are sometimes employed. Unseparated fluids should be distributed to the separating region as uniformly and with as little velocity as possible. When the bubble rise velocity is quite low, shallow tanks or flow channels should be used to minimize the residence time required. 

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