Jacketed vessels dimpled

Figure 12.72. Jacketed vessels, (a) Spirally baffled jacket (b) Dimple jacket (c) Half-pipe jacket (d) Agitation...

Dimpled jacket A dimpled jacket consists of an outer shell having regular indentations of the shell material. These dimples are intended to promote turbulence by creating high local velocities at the dimple. Heat-transfer information concerning dimple-jacketed vessels are proprietary to the fabricators there is a little information in the open literature [77], Other devices There are other special devices such as clamp-on plate coils, weld-on plate coils, etc., that are often used when an unjacketed vessel needs limited heat-transfer capability. 

When liquids are to be evaporated on a small scale, the operation is often accomplished in some form of jacketed kettle. This may be a batch or continuous operation. The rate of heat transfer is generally lower than for other types of evaporators and only a limited heat transfer surface is available. The kettles may or may not be agitated. Jackets may be of several types conventional jackets (formed with another cylinder concentric to the vessel), dimpled jackets, patterned plate jackets, and half-pipe coil jackets. (See Figure 11-1.) This variety provides a great deal of flexibility in the choice of heat transfer medium. 

P). Otherwise the baffles should be located iaside the cod helix. A conventional jacket consists of a vessel outside the main vessel with a gap for the flow of heat-transfer fluid. Half-pipe jackets are usefld for high pressures up to 4 MPa (600 psi). They are better for Hquid than for vapor service fluids and can be easdy 2oned. Dimple jackets are suitable for larger vessels and process conditions up to 2 MPa (300 psi) and 370°C. Internal cods can be either hehcal or baffle cods (Fig. 34). 

The equivalent diameter D,. in a dimpled jacket equals 0.66 m. the cross-sectional flow area equals 1.98 m." per foot of vessel circumference. 

Dimpled jackets are similar to the conventional jackets but are constructed of thinner plates. The jacket is strengthened by a regular pattern of hemispherical dimples pressed into the plate and welded to the vessel wall, Figure 2.12b. 

The integral type utilizes the inner surface of the dimple jacket for the vessel shell. Advantages of the integral type are as follows ... 

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