Rod Baffles

Rod Baffles Rod or bar baffles have either rods or bars extending through the lanes between rows of tubes. A baffle set can consist of a baffle with rods in all the vertical lanes and another baffle with... 

Figure 8.12. Arrangements of cross baffles and tube-side passes, (a) Types of cross baffles, (b) Rod baffles for minimizing tube vibrations each tube is supported by four rods, (c) Tube-side multipass arrangements.

The type of exchanger influences cleaning frequency. For example, spiral-plate units are often used in fermentation plants, owing to the ease of solid resuspension and the devices nonplugging characteristics. A rod-baffle design provides more-effective shellside turbulence at a lower pressure drop than a segmented-baffle unit, so the former is likely to have less fouling. 

Figure 8.19 shows the flux-time profiles obtained in filtration of 5% yeast cell suspension using a mbular membrane of 6 mm i.d. (inside diameter) and 0.14 pm pore size with a helical baffle (HB), a rod baffle (RB), and the mbular membrane without baffle (NB) [35]. The comparison has been made at the same hydraulic-dissipated power, which is defined as the product of the flow rate and the pressure drop along the mbular membrane, or the energy consumed to generate the crossflow through the mbular membrane. Using the hydraulic-dissipated power rather than the crossflow rate as a control parameter for the comparison of the mbular membrane with and without inserts eliminates the effect of the reduced crossflow section by... 

FIGURE 17.5 Rod baffle supports (a) four rod baffles supported by skid bars (no tubes shown), (b) a tube supported by four rods at 90° angle around the periphery, (c) a square layout of tubes with rods, (d) a triangular layout of tubes with rods. 

Rod baffles have been reported to reduce fouling of shellside fluids in some applications. The apparent reason is the vortices created downstream of the rods and the elimination of stagnant flow areas. 

Flow distribution is also important on the shellside, especially in cases where parallel flow baffles or Rod Baffles are required. Vapor belts, or distribution belts, serve to distribute shellside fluids in many cases. Vapor belts may be used to permit fluid to enter the shell over the entire circumference or they may be designed such that the fluid enters only a specified area of the shell. Vapor belts reduce entrance velocities and entrance pressure drops while effecting good distribution. 

Rod baffle heat exchangers. (Courtesy of the Noofer Corporotion, St. Louis.)... 

---