Tube bundle diameter, heat exchanger

Db Tube bundle diameter for shell-and-tube heat exchangers (m)... 

Whereas the laboratory fluidized bed is generally operated with no internals, plant equipment often must contain bundles of heat-exchanger tubes. Screens, baffles, or similar internals are frequently used to redisperse the bubble gas in industrial reactors. The mass-transfer area is thus increased relative to the fluidized bed without internals the extra area can be utilized to partially offset the conversion-reducing effects of bed diameter and gas distributor [122]. 

FLOW OUTSIDE TUBES PARALLEL TO AXIS. Some membrane separators have bundles of hollow fibers in a shell-and-tube arrangement with liquid or gas flowing parallel to the tube axis on the outside of the tubes. The external flow passages are irregular in shape and not uniform, since the fibers are not held in position as are the tubes in a heat exchanger. Empirical correlations for the external mass-transfer coefficient have been proposed using an equivalent diameter to calculate the Reynolds number. For a bundle of fibers with diameter d packed in a shell with c void fraction, the equivalent diameter is... 

A straight tubular tube-and-shell heat exchanger is selected for the IHX In order to satisfy the compact demand, the heat transfer tubes with small diameter, close pitch, iimer spire as well as outer low fin are chosen for the IHX tube bundle Preliminary designs of the IHX are given in Table 3... 

Figure 10-8. Single-pass shell and tube Teflon tube heat exchanger, countercurrent flow. Tube bundles are flexible tube Teflon joined in integral honeycomb tubesheets. Shell-side baffles are provided for cross-flow. Standard shell construction is carbon steel shell plain or Teflon (LT) lined. Heads are lined with Teflon . Tube diameters range from 0.125-0.375 in. O.D. the temperature range is 80-400°F pressures range from 40-150 psig. (Used by permission AMETEK, Inc., Chemical Products Div., Product Bulletin Heat Exchangers of Teflon . )...

Steady two-phase flow. In rod (or tube) bundles, such as one usually encounters in reactor cores or heat exchangers, the pressure drop calculations use the correlations for flow in tubes by applying the equivalent diameter concept. Thus, in a square-pitched four-rod cell (Fig. 3.51), the equivalent diameter is given by... 

At present the direct synthesis of alkyl- and arylchlorosilanes is often carried out in apparatuses which operate using the phenomenon of fluidising. Turbulent movement of components in such a reactor guarantees good contact of reactants with contact mass, as well as steady temperature. Reactors with the fluidised layer are cylindrical apparatuses of various diameter with heat exchange elements. Fig.9 features a reactor with a heat exchange element in the form of a Field tube, and Fig. 10 shows a reactor with a heat exchange element in the form of a small-diameter tube bundle. 

For reactors of a larger diameter (e.g. more than 600 mm) it is more advisable to use a bundle of small tubes as heat exchangers. Such a distribution of heat exchange surfaces virtually does not inhibit fluidising and ensures that the heat is efficiently withdrawn from the whole surface of the apparatus. It should be also kept in mind that tube bundles allow one to select the reaction space and place rotating gas distribution devices between sections this considerably increases the coefficient of heat transfer and ensures a more uniform gas distribution in the reaction zone. 

Consider the following problem. In the petrochemical industry, many reactions are oxidations and hydrogenations that are very exothermic. Thus, to control the temperature in an industrial reactor the configuration is typically a bundle of tubes (between 1 and 2 inches in diameter and thousands in number) that are bathed in a heat exchange fluid. The high heat exchange surface area per reactor volume allows the large heat release to be effectively removed. Suppose that a new catalyst is to be prepared for ultimate use in a reactor of this type to conduct a gas-phase reaction. How are appropriate reaction rate data obtained for this situation ... 

Example 3.11 Atmospheric air (p = 0.1 MPa) is to be heated in a tube bundle heat exchanger from 10 °C to 30 °C. The exchanger consists of 4 neighbouring rows and zr rows of tubes aligned one behind the other. The outer diameter of the tubes is 25 mm, their length 1.5m, the longitudinal pitch is the same as the transverse pitch s /d = sq/d = 2. The wall temperature of the tubes is 80 °C with an initial velocity of the air of 4m/s. Calculate the required number zr of tube rows. 

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