Heat transfer in agitated vessels

The heat generation varies during processing if an exothermic reaction is carried out in a batch reactor. The temperature can be controlled by external 

The factors that can affect the rate of heat transfer within a reactor are the speed and type of agitation, the type of heat transfer surface (coil or jacket), the nature of the reaction fluids (Newtonian or non-Newtonian), and the geometry of the vessel. Baffles are essential in agitated batch or semi-batch reactors to increase turbulence which affects the heat transfer rate as well as the reaction rates. For Reynolds numbers less than 1000, the presence of baffles may increase the heat transfer rate up to 35% [180]. 

Another technique of cooling is to use a boiling solvent to withdraw heat from the reaction mass, usually in a reflux mode as has been discussed previously. An adequate supply of solvent and the appropriate coolant supply to he condenser must obviously be assured. 

The choice of the heat exchange system also depends on the overall purpose of the reactor. 

The heat transferred in an agitated vessel can be expressed by the basic standard equation  

TWO-PHASE PRESSURE DROP CALCULATION IN A PIPE LINE PIPE INTERNAL DIAMETER, inch 3.070 

INDEX 4553. IS LESS THAN 10000.0 PIPE EROSION IS UNLIKELY 

The pitch of the coils and the area covered can be selected to provide the heat transfer area required. Standard pipe sizes from 60 imn to 120 mm outside diameter area are often used. Half-pipe construction can produce a jacket capable of withstanding a higher pressure than conventional jacket design. 

When proeessing is eontrolled by heat transfer variables, a log mean temperature differenee (ATLj. j.p) and heat transfer surfaee area will predominate over the agitation variables. Provided it is suffieient to give a homogeneous proeess fluid temperature, inereased agitation ean only reduee the inside film resistanee, whieh is one of a number of resistanees that determines the overall heat transfer eoeffieient. 

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 

In an idealized situation, the vessel and its jacket each operate continuously under isothermal conditions. Rearranging Equation 7-69 becomes  

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Heat transfer in agitated vessels with internal coils containing the heat transfer fluid (process on outside of coil) is expressed by the outside coefficient on coils ... 

There is further discussion of heat transfer in agitated vessels by Rase [34] and Holland and Chapman [35]. 

Hruby, M., Int. Chem. Engng. 7 (1967) 1, 86-90 Relationship between the dissipation of mechanical energy and heat transfer in agitated vessels... 

K. Ishibashi, A. Yamanaka, and N. Mitsuishi, Heat transfer in agitated vessels with special types of impellers, J. Chem. Eng. Japan, 12(3),... 

Wilkinson, W L. and Edwards, M. F. (1972) Chem Engr, London, No. 264 (August) 310, No. 265 (September) 328. Heat transfer in agitated vessels. 

Havas G., Deak A., Sawinski )., The ect of the impeller diameter on the heat transfer in agitated vessels provided with vertical tube baffles, Chem. Engng. J. 27 (1983), p. 197-198... 

Strek, F., Karcz )., Experimental Determination of the Optimal Geometry of Baffles for Heat Transfer in Agitated Vessels, Chem. Eng. Process. 29 (1991), p.165-172... 

Bondy, F., and Lippa, S., Heat Transfer in Agitated Vessels, Chemical Engineering, April 4, 1983. 

Edwards, M. F., and M. A. Wilkinson (1972b). Heat transfer in agitated vessels II. Non-Newtonian fluids, Chem. Eng., Sept., pp. 328-335. 

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