Baffles configurations

Mechanical equivalent of heat Correction factors for baffle by )assing, baffle configuration, baffle 1.0(N-m)/J 778(ft-lkf)/Btii... 

Figure 10-73. Shell-side pressure loss for 3 shell-side baffle configurations—RODbaffles . (Used by permission Small, W. M., and Young, R. K. Heat Transfer Engineering, V. 2, 1979. Taylor and Francis, Inc., Philadelphia, PA. All rights reserved.)...

Find the conection factor for baffle-configuration effects J from Fig. 11-10. 

A helical baffle bundle built in this w produces two distinct flow regions. The area outside of the adjacent baffle contact diameter tends to produce a stable helical cross flow. However, inside the diameter where adjacent baffles touch is a second region where vortical flow is induced but in which the intensity of the rotational component tends to decrease as one approaches the center of the bundle. For a fixed flow rate and helix angle, this tendency may be minimized by the proper selection of the baffle contact diameter. With the correct selection, stream temperatures may be made to be close to uniform across the bundle cross section through the shell. However, below a critical velocity (for the baffle configuration and fluid state), the tendency for nonuniformity of temperatures increases as velocity decreases until ever-increasing portions of the central core surface area pinch out with respect to temperature and become ineffective for further heat transfer. 

Heat transfer can occur in either batch or continuous configurations. Both types of processes require fluid motion to obtain an effective heat transfer to the bulk of the fluid. In batch processing using jacketed vessels, helical coils, or coils in a baffle configuration, for example, sufficient agitation is required for heat transfer through the medium while continuous systems rely on flow rate to achieve effective heat transfer to satisfy process requirements. Effective heat transfer in batch operations for structured liquid detergents may require scrapers or anchor-type impellers to increase heat transfer coefficients in jacketed vessels. 

FIGURE 6.28 (a) Single-segmental baffle configuration, (b) Double-segmental baffle configuration. 

Edwards and Ellis found somewhat similar result in that a T propeller was most efficient with a clearance off the base of centrally placed and without any baffles (compared to a wide range of baffle configurations and impeller clearances using the propeller, a disc turbine and a flat paddle), i.e. they found central vortexing with solids added into the vortex the best. 

Figure 16.10 A preferred baffle configuration and the position of the vortex ...

Question by B. M. Warner, United Aircraft Corp. Have you investigated various condensing baffle configurations ... 

A standard baffle configuration consists of four vertical plates having width equal to 8 to 10% (T/12 to T/10) of the tank diameter. Narrower baffles are sometimes used for high viscosity systems, buoyant particle entrainment (width = 2% of T), or when a small vortex is desired. A small spacing between baffles and the tank wall (1.5% of T) is allowed to minimize dead zones particularly in solid-liquid systems. Wall baffles increase the power consumption of the mixer and generally enhance the process result. 

The power number, Np, also is a function of impeller blade width, number of blades, blade angle, D/T, baffle configuration and impeller elevation. Figure 6-14 shows the relationship between Np and Re for seven impellers. It is important to recognize that at Re < 100, the conditions become laminar flow and mixing quality, obtained using these impellers, becomes extremely poor. Under such conditions, impellers designed for laminar flow conditions are reconunended. 

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