Wall baffles

Wagner equation Wagner number Wakamatsu reaction Waldhof fermentor Walkman Wallace plasticity Wallach procedure Wall baffles Wallboard Wall geometries Wallpaper paste Wallpaper pastes Wallpapers Wall plaster Walnut oil... 

The numbei of wall baffles and tfiek widtfi B also have a significant effect on As increases, increases (Fig. 6a) up to the of the... 

Commonly used heat-transfer surfaces are internal coils and external jackets. Coils are particularly suitable for low viscosity Hquids in combination with turbine impellers, but are unsuitable with process Hquids that foul. Jackets are more effective when using close-clearance impellers for high viscosity fluids. For jacketed vessels, wall baffles should be used with turbines if the fluid viscosity is less than 5 Pa-s (50 P). For vessels equipped with cods, wall baffles should be used if the clear space between turns is at least twice the outside diameter of the cod tubing and the fluid viscosity is less than 1 Pa-s (10... 

FK . 15-22 Uqiiid agitation by a disc flat blade turbine in the presence of a gas-liquid interface a) without wall baffles, (h) with wall baffles, and (c) in full vessels without a gas-bqiiid interface (continuous flow) and without baffles. [Couitesy Treyhal, Mass Transfer Operations, 3rd ed., p. 148, McGraw-Hill, NY,... 

Figure 12. Variation of velocity distribution in a mixing tank on insertion of full side wall baffles.

We round this off to T = 1370 mm, which for a flat bottom tank is Z = 1360 mm. The vessel should have four full length wall baffles having a width between T/12 and T/10. Thus B = 130 mm. 

Solid partieles in liquids generally tend to settle to the bottom of a vessel under gravity due to their exeess density. To maintain a suspension, some form of agitation is normally provided together with wall baffles to prevent vortex formation in the swirling flow (Figure 2.14). 

The power required for vertical tubes in a vessel is 75 percent of that for standard wall baffles [13]. It is sometimes difficult to physically place as much vertical coil surface in a tank as helical coil surface. Dunlap studied vertical coils and the results are correlated for dimensionally similar systems by [6] [29]... 

Boiler fireside walls, baffles, tubesheets, tubes and drums should be cleaned to remove ash and soot before examination. Where soot blowers are installed, they should be utilized as a means of cleaning fireside surfaces before the boiler load has dropped to 50% and should not be operated again, especially if the fire has been extinguished because a risk of explosion exists. 

The polymerizations were conducted in a 20-liter stainless steel reactor with a pitched-blade turbine agitator and four side-wall baffles. The monomer was polymerized at the same temperature, initiator and monomer concentration in two different inert diluents. The data (Figure 6) illustrate the substantial lowering of the overall heat transfer coefficient for the system with the more highly swollen particles. 

Madden and Damerell carried out their study in a 1.5-liter vessel of stainless steel internally coated with Teflon to prevent wetting by the aqueous dispersed phase. This reactor was stirred by means of a turbine and equipped with wall baffles. They investigated the effect of stirring rate (corresponding with a power input from 0.25 to 2 hp./m.8) and the effect of dispersed phase fraction from 0.0014 to 0.011. The interaction rate co< they found varied from 0.04 to 0.5 sec.-1 (see Fig. 25). 

Measurements were carried out in a 6-liter brass vessel stirred by means of a flat blade stirrer and equipped with 4 wall baffles. The influence of dispersed phase fraction and of stirring rate was investigated. The dispersed phase fraction was varied from 0.06 to 0.15 while the power input by the stirring was varied from 0.1 to 3 hp./m.8. The interaction rate found was invariably 0.035 sec.-1. Another experiment was carried out by Kramers and de Korver using a short rotary contactor (height = 10 cm., diameter = 9.3 cm., diameter of rotor = 8.0 cm.) which was made entirely of Teflon to prevent wetting of the wall by the aqueous dispersed phase. This reactor... 

The need to use wall baffles to eliminate vortexing decreases as fluids become more viscous (5000-10,000 cP or more). But swirl will still be present if there are no baffles. Accordingly, quite often baffles of about one-half normal width are used in viscous materials. In such cases they are placed about halfway between the impeller and the wall. 

FIGURE 11 Effect of baffles in position on flow pattern, (a) Typical swirling and vortexing flow in a tank without baffles, (b) Typical top-to-bottom flow pattern with radial flow impellers with four wall baffles, (c) Typical angular off-center position for axial flow impellers to give top-to-bottom flow pattern to avoid swirl without the use of wall baffles. 

A is the cross-sectional area of the jet impinging on the vessel wall/baffle in the stirrer plane. 

The characteristic solid body rotation is the primary flow pattern in un-bafiled tanks. To avoid these phenomena, baffles are installed in the tank. On wall baffles are sketched in Fig 7.1. Generally, baffles are placed in the tank to modify the flow and surface destroy vortices. Baffles mounted at the tank wall are most common, but also bottom baffles, floating surface baffles and disk baffles at the impeller shaft are possible. Often tank wall baffles are mounted a certain distance from the wall, as illustrated in Fig 7.3. This creates a different flow pattern in the tank. The purpose of installing baffles away from the wall is to avoid dead zones where liquid is seldom exchanged and where impurities accumulate. Experiments have confirmed that the flow patterns in baffled agitated tanks are different from the flow patterns in unbaffled agitated tanks. In baffled tanks the discharge flow dissipates partly in the bulk... 

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