Jacketed vessels heat transfer

Figure 10-93A. Typical vessel external jackets for heat transfer.

Florin and Bartesch described fluid-bed drying of soybeans (23). Unlike steam-jacketed vessels that transfer heat from the vessels wall into the seeds as the seeds tumble through the vessel, a fluid-bed conditioner uses air to suspend and move the seed through the conditioning chamber. If the air is heated, it can transfer heat... 

Most of the factors in Table 4.1 apply equally to batch and flow vessels. The throughput in a well-designed CSTR is small compared to the internal circulation and does not affect quantities such as power, mixing time, and heat transfer to the jacket. The heat transfer factors in Table 4.1 are discussed in Chapter 5. 

The volume of the nitration reactor is about 110 L equipped with an explosion proof motor, a cycloidal reducer, mechanical seals, an anchor agitator, a temperature sensor, a pressure gauge, three feeding holes with different size, a segregator with a glass mirror, 1,000 mm condenser, and a jacket of heat transfer oil. The system also includes a temperature controller, an agitation controller, and a washing vessel. By application of the production unit, the yield of n-butyl nitrate is up to 95.7 % with the purity of 98.88 %. 

Many industrial processes are carried out in agitated tanks with accompanying heat transfer. In such cases, the vessel is jacketed. The heat transfer fluid used for heating or cooling circulates through the jacket. Heating or cooling coils are also sometimes immersed in the vessel as well. 

Commonly used heat-transfer surfaces are internal coils and external jackets. Coils are particularly suitable for low viscosity Hquids in combination with turbine impellers, but are unsuitable with process Hquids that foul. Jackets are more effective when using close-clearance impellers for high viscosity fluids. For jacketed vessels, wall baffles should be used with turbines if the fluid viscosity is less than 5 Pa-s (50 P). For vessels equipped with cods, wall baffles should be used if the clear space between turns is at least twice the outside diameter of the cod tubing and the fluid viscosity is less than 1 Pa-s (10... 

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). 

Most of the correlations for heat transfer from the agitated hquid contents of vessels to jacketed walls have been of the form ... 

This chapter reviews the various types of impellers, die flow patterns generated by diese agitators, correlation of die dimensionless parameters (i.e., Reynolds number, Froude number, and Power number), scale-up of mixers, heat transfer coefficients of jacketed agitated vessels, and die time required for heating or cooling diese vessels. 

Consider a vessel containing an agitated liquid. Heat transfer occurs mainly through forced convection in the liquid, conduction through the vessel wall, and forced convection in the jacket media. The heat flow may be based on the basic film theory equation and can be expressed by... 

Heat transfer coefficient to fluids in a vessel using mechanical agitated coils or jacket... 

Heating or cooling of process fluids in a batch-operated vessel is common in the chemical process industries. The process is unsteady state in nature because the heat flow and/or the temperature vary with time at a fixed point. The time required for the heat transfer can be modified, by increasing the agitation of the batch fluid, the rate of circulation of the heat transfer medium in a jacket and/or coil, or the heat transfer area. Bondy and Lippa [45] and Dream [46] have compiled a collection of correlations of heat transfer coefficients in agitated vessels. Batch processes are sometimes disadvantageous because ... 

Approximate Overall Heat Transfer Coefficients for Jacketed Mixing Vessels... 

Heat Transfer in Jacketed, Agitated Vessels/Ketdes... 

See Figures I0-93A and I0-93B as limited examples of reaction and other process vessels that require heat transfer for proper processing. Markovitz reports improved heat transfer for the inside of jacketed vessels when the surface has been electropolished, which gives a fine, bright surface. 

For heat transfer fluids inside reactor jackets or other process vessels with agitation to fluids in vessels (Figure 10-93A), the heat transfer is expressed as... 

A useful application is for tank and vessel heating, with the heater protruding into the vessel. Bayonet heat exchangers are used in place of reactor jackets when the vessel is large and the heat transfer of a large mass of fluid through the wall would be difficult or slow, because the bayonet can have considerably more surface area than the vessel wall for transfer. Table 10-43 compares bayonet, U-tube, and fixed-tubesheet exchangers. ... 

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