Tubular design

Higher overall heat transfer coefficients are obtained with the plate heat exchanger compared with a tubular for a similar loss of pressure because the shell side of a tubular exchanger is basically a poor design from a thermal point of view. Considerable pressure drop is used without much benefit in heat transfer efficiency. This is due to the turbulence in the separated region at the rear of the tube. Additionally, large areas of tubes even in a well-designed tubular unit are partially bypassed by liquid and low heat transfer areas are thus created. 

Figure 1.5 shows ways of designing tubular reactors to include heat transfer. If the amount of heat to be transferred is large, then the ratio of heat transfer surface to reactor volume will be large, and the reactor will look very much like a heat exchanger as in Fig. 1.5b. If the reaction has to be carried out at a high temperature and is strongly endothermic (for example, the production of ethylene by the thermal cracking of naphtha or ethane—see also Section 1.7.1, Example 1.4), the reactor will be directly fired by the combustion of oil or gas and will look like a pipe furnace (Fig. 1.5c).

Cichy, P.T. Russell, T.W.F. Two-phase reactor design tubular reactors—reactor model parameters. Ind. Eng. Chem. Res. 1969, 61, 15. 

Design tubular electrolyzer stack for high-pressure operation. 

In order to study the prospects of the application of diffuser-confusor designed tubular turbulent reactors for the production of homogeneous finely dispersed suspensions, by condensation in fast chemical reactions, and to compare their operating efficiency with volume reactors, a model reaction, which occurs at high rate, was chosen [28] ... 

The constraints in designing tubular and convective reformers are hence primarily the mechanical material properties. The catalyst volume may then be considered a derived property. However, high catalyst activity is essential to ensure low tube-wall temperature. A higher... 

The latter is normally the preferred method employed in industry since it is the mass of catalyst present in the reactor that significantly impacts the reactor design. Since the rate expression is often more complex for a catalytic reaction than for a non-catalytic (homogeneous) reactor, the design equation may be difficult to solve analytically. Numerical solution of the reactor design equation is usually required when designing tubular flow reactors for catalytic reactions. 

Cichy, P.T., J.S. Ultman and T.W.F. Russel. Two-Phase Reactor Design Tubular Reactors - Reactor Model Development 61 (1969) (No. 8) 6-26. 

Mechanical Design. Tubular reformers are designed with a variety of tube and burner arrangements (Rostrup-Nielsen, 1984a). Basically there are four types of reformers as illustrated in Figure 3. 

Fig. 3a. Schematic view of SOFC cell design tubular type.

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