Tubular flow reactors heat transfer

Tubular flow reactors are suited to high production rates at short residence times (sec or mmj and when substantial heat transfer is needed. Embedded tubes or shell-and-tube construction are then used. 

All chemical reactions are accompanied by some heat effects so that the temperature will tend to change, a serious result in view of the sensitivity of most reaction rates to temperature. Factors of equipment size, controllability, and possibly unfavorable product distribution of complex reactions often necessitate provision of means of heat transfer to keep the temperature within bounds. In practical operation of nonflow or tubular flow reactors, truly isothermal conditions are not feasible even if they were desirable. Individual continuous stirred tanks, however, do maintain substantially uniform temperatures at steady state when the mixing is intense enough the level is determined by the heat of reaction as well as the rate of heat transfer provided. 

Continuous-stirred tank reactors lie somewhere between tubular and batch reactors. Mixing and heat transfer problems are similar to those of batch reactors. However, many of the stirred-tank reactors have benefits of the tubular flow reactors. These include isolation of intermediates, automatic control, and low labor costs. 

The design equations for ideal tubular-flow reactors involve no new concepts but simply substitute a rate of reaction for a heat-transfer rate or mass-transfer-rate function. The increased complexity of reactor design in comparison with the design of equipment for the purely physical processes lies in the difficulty in evaluating the rate of reaction. This rate is dependent on more, and less clearly defined, variables than a heat- or mass-transfer coefficient. Accordingly, it has been more difficult to develop correlations of experimental rates, as well as theoretical means of predicting them. 

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