Two Types of Baffles

Charge (Explosive Charge). See Ref 44, p 050 Cluster. See Vol 3 of Encycl, p C351-L 

under CELLULOSE NITRATES. Also known as Pyroxylin 

Complete Round of Ammunition. See Ammunition, Complete Round in Ref 43, p A385-L 

D38-R and D107-L. Known also as Low Explosives (See in this Glossary) 

Delay Charges Delay Compositions or Delay Powders. See Ref, 48, p D50-Lff and Section 4, Part F in this Vol 

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Segmental and disk-and-doughnut baffles contain tube-pass holes of size close to that of the diameter of the tubes. With these two types of baffles, the clearance between the tubes and the edge of the holes may range from 1 percent to as high as 3 percent of the tube diameter. As a result, some fluid passes through the clearance spaces, but the major portion of the fluid should flow between the baffles in a direction perpendicular to the tubes. 

Baffles Baffles aie installed perpendicular at tube bundle to 1) control the shell side fluid velocity (also the shell side heat transfer coefficient and pressure drop), 2) prevent tube failure due to the flow induced tube vibration, and 3) support the tubes to avoid sagging. There are two types of baffles plate type and rod type, We will discuss plate ty baffle only in this chapter. 

Two types of bioreactors have been used to produce SCP from sugar sources, namely stirred/baffled type and the air-lift with draught tube type (figure 4-5), with various capacities up to 400 m. 

The latter two types of stirrers are produced by Ekato Company, Schop-fheim, Germany. These are low-speed stirrers with a dx/d, ratio of 1.5 in the presence of baffles and 1.1 in the absence of baffles. The stirrers are versatile and are used for liquid homogenization, gas-liquid or liquid-liquid dispersion, and solids suspension in slurry reactors. 

The motion of the vessel contents is influenced by the agitator and any baffles. The agitator, or impeller, provides the power to move the vessel contents. There are two types of impellers radial-flow impellers, which move the liquids along the radius of the impeller, and axial-flow impellers, which move the liquids parallel to the axis of the agitator shaft. Without baffles, low-viscosity fluids tend to create... 

Other variations of stirred columns which are available include the asymmetric rotating disc (ARD) contactor, the Kuhni column, and two types of Scheibel columns. The rotor of the ARD is located off center, which permits more elaborate baffling for the necessary transport of flows with less backmixing. 

A four blade glass rectangle, specially made to fit the reactor, was used as a baffle system when desired. Figure 3 shows the reactor mixing configuration and the dimensions of the two types of impellers tested. A Sage Instruments model 355 syringe pump was used to feed the reaction solution to the quench reactor at a... 

Figure 23-6. Two types of muffler designs, (a) A straight-through dissipative design, (b) A reactive type with baffle and tubes.

Cooling Towers. There are two types of cooling towers, wet towers and dry towers. Wet towers cool by evaporation and require constant water replacement Warm water from the condenser is sprayed over baffles unevaporated water drips to the foimdation, where it is collected and recirculated. Evaporation requires about 3 percent of the water to be replaced continuously. 

The impeller blades are usually mounted at a height between 0.25 and 0.5 of the height of the liquid layer. The diameter of the impeller conunonly varies between 0.2 and 0.5 of the tank diameter a diameter ratio of 1/3 is often preferred. The tanks are usually equipped with baffles (most often four), flat plates of a width of about 0.1 of the tank diameter, mounted vertically along the walls. These baffles serve to reduce liquid circulation around the axis and so to avoid the formation of a vortex in the middle they also promote vertical circulation. Propellers are usually made so that they pump downwards, as a result of which there is a liquid flow going up near the wall. Turbine impellers pump radially, so that in the lower half of the tank the liquid circulates downwards near the wall and upwards in the middle, and in the upper half the other way around. In some respects there is no important difference between these two types of impellers. Both create an effective circulation, and in both cases most of the supplied mechanical energy is eventually dissipated in small eddies. The friction losses at the wall and at the impeller blades are a relatively small fraction of the total energy dissipation. 

Fill Packing Specially designed baffling used to provide a large surface area for heat transfer. Two classes of materials are used splash bars of wood, metal transite or plastic and film pack (cellular fill). The splash type cools the water as the droplets bounce down a series of bars in the air stream film packing converts droplets into a thin film. 

The simplest type of shell-and-tube heat exchanger is shown in Eigure 3-1. The essential parts are a shell (1), equipped with two nozzles and having tube sheets (2) at both ends, which also serve as flanges for the attachment of the two channels or beads ( 3) and their respective channel covers (4). The tubes are expanded into both tube sheets and are equipped w nil transverse baffles (5) on the shell side for support. The calculation of the effective heat transfer surface is based on the distance between the inside faces of the tube sheets instead of the overall tube length. 

Fig. 2. This plot shows to which degree, according to a LES, the turbulence in a plane midway between two baffles in a stirred vessel provided with a Rushton turbine can be typified. For clarity, not all grid points in such a plane have been used for this plot. According to Lumley (1978), the borders represent different types of turbulent flows 3-D isotropic turbulence, 2-d axis-symmetric turbulence, 2-D turbulence, and 1-D turbulence. Most but not all points are concentrated in the lower part of this Lumley triangle. Reproduced with permission from Hartmann et al. (2004a).

Vertical blowdown drum/catch tank This type of drum, shown in Fig. 23-51, performs the same function and operates on similar princi-les as horizontal separators. These separators are usually used where orizontal space is limited. The two-phase mixture enters the vessel via a nozzle on the vertical shell and is distributed by an inlet baffle chamber. 

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