Design for Good Heat Transfer

This all results in reduced capital cost. The disadvantage of this tube pitch is that, except for the outer few rows of tubes, the shell side cannot be cleaned by hydroblasting. Obviously, this sort of arrangement should never be used in a fouling service, unless the deposits can be chemically removed. 

The second example shown in Fig. 19.7 is 34-in tubes, also set on a 1-in spacing. But this time, the arrangement is a square pattern. This pattern reduces the number of tubes in a shell of a fixed ID. Also, less turbulence is created by the tubes. Some fluid may flow between the tubes, without encountering the tubes at all. All this reduces heat-transfer efficiency. But hydroblasting between the tubes is usually possible—depending on the extent of tube bending and twisting. 

The third example shown in Fig. 19.7 is my favorite for sensible-heat transfer in fouling service. This consists of 1-in tubes set on lV2-in rotated square pitch. The pitch layout is the same as that of the square pitch. It is just the tube bundle that is rotated by 45°. The shell-side fluid cannot flow without interference between the tubes. Hence, the tubes promote turbulence, and improve heat transfer. The large tubes, 

Most of the heat exchangers in your plant are designed with the shell-side inlet and shell-side outlet at opposite ends of the shell, as shown in Fig. 19.6. However, you may have noted a few exchangers in which both the shell-side inlet and shell-side outlet are next to the channel head. This is a two-pass shell-side exchanger, of the type shown in Fig. 19.8. 

The critical feature of this exchanger is the longitudinal baffle, which extends down the length of the shell. The baffle is fitted directly to, and thus becomes physically part of, the tube bundle. The function of the baffle is to force the shell-side fluid to flow down the entire length of the 

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This design has a number of tubes embedded inside the turbine blade to provide channels for the water (Figure 9-23). In most cases, these tubes are constructed from copper for good heat-transfer conditions. The water, which is converted to steam by the time it reaches the blade tips, is then... 

The reactions are highly exothermic and very rapid. Consequently conventional practice in the design of fixed bed reactors for phthalic anhydride production has been based on the use of multitube reactors to ensure good heat transfer and good temperature control. These are required to ensure good selectivity. Often a thousand or more small diameter tubes may be... 

There is good heat transfer in agitated gas-liquid-solid slurry reactors see, e.g., van t Riet and Tramper for correlations (Basic Bioreactor Design, Marcel Dekker, 1991). 

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