Jacketed vessels conventional

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). 

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 conventional photolysis apparatus consists of a concentrically arranged immersion well for the lamp, which is surrounded by a cooling jacket, which is itself surrounded by the reaction vessel. If this last compartment is used for the filter solution an additional external flask for the reaction mixture has to be used. There are also photochemical reactors wherein the lamps are arranged externally around the reaction flask. 

A water-less bath method is stated in < 711 > as an alternative way to heat the vessels other than a conventional water bath (11). As shown in Figure 2, the vessels are heated with a water jacket and are not submerged into a water bath. With this bath, as with all testers that use the basket apparatus, when the basket shaft with the basket is introduced into the vessel medium, the temperature will drop slightly. There-... 

Used widi steam or coofing. Liquid flow velocities are low and the flow is poorly distributed. Natural convection equations are suitable and cooling coefficients have low values. Conventional jackets are best applied to small vessels or high pressure applications, where flie vessel internal pressure is twice the jacket pressure as a minimum. The conventional jacket is the most common... 

This design provides high velocity and turbulence within the jacket. This in turn will result in an unusually high film coefficient. The half pipe coil is recommended for high temperature and all liquid applications. It is better than conventional jackets because the pressure drop can be carefully controlled and calculated. It is not however practical for small vessels, less than 500 gallons. Because there are no limitations to the number of inlet and outlet connections, this type of jacketing can be divided into multiple zones for maximum flexibility and efficiency. 

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. 

The mixer used, for example, in a stirred tank, can be given a boost in performance by generating heat in the blades of the mixer itself. Conventionally, in a stirred vessel, the heat input is via a jacket, with conduction of heat through the vessel wall and some forced convection thereafter in the mixed product. Using electrical induction heating via a coil, the paddles themselves can be heated, allowing local reductions in viscosity. 

The conventional stirred-tank reactor is an agitated vessel, typically a jacketed pressure vessel, and often with provisions for reflux of a solvent or monomer. The continuous-feed version is the CSTR. Continuous operation is typical of high-volume polymers but large batch and fed-batch stirred-tank reactors are occasionally used. Reactors other than stirred tanks may be functionally equivalent to stirred tanks. Loop reactors are widely used in the polymer industry, especially for solution and slurry olefin polymerizations the agitator in the stirred tank is replaced with a circulation pump. The loop many consist of jacketed pipe or there may be heat exchangers and even flash vessels in the loop. The loop may consist of many legs for space considerations, but the legs are connected in series and there is only one circulation pump. 

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