Condenser vertical downflow

For condensing vapor in vertical downflow, in which the hquid flows as a thin annular film, the frictional contribution to the pressure drop may be estimated based on the gas flow alone, using the friction factor plotted in Fig. 6-31, where Re is the Reynolds number for the gas flowing alone (Bergelin, et al., Proc. Heat Transfer Fluid Mech. Inst., ASME, June 22-24, 1949, pp. 19-28). 

Figure 8.14. Some arrangements of shell-and-tube condensers, (a) Condensate inside tubes, vertical upflow. (b) Inside tubes, vertical downflow, (c) Outside tubes, vertical downflow, (d) Condensate outside horizontal tubes. (HEDH, 1983, 3.4.3).

Condenser design determines the extent of Rayleigh fractionation. Vertical upflow condensers ("vent or "inerts condensers (e.g.. Fig. 15.14c,e see Sec. 15.11) are intended to operate as Rayleigh fractionators. Other condensers which exhibit this fractionation behavior are unbaffled vertical downflow shell-side condensers (if baffles are included, they would interrupt the free fall of liquid), emd multipass horizontal in-tube condensers where liquid is segregated at the end of each pass. One case was reported (381) where this behavior caused severe inerts blanketing in an unbafiled, downflow shell-side condenser. 

Vapor entering a vertical downflow in-sbell condenser contained a hig -molecular-weig t condensable material and a low-molecular-wei t inert Poor condensation was caused by channeling that caused inert blanketing. Use sealing strips ensure adequate condenser pressure drop. 

FIGURE 14.12 Comparison of experimental data with several models during condensation on a horizontal tube with vertical vapor downflow. (Adapted from Ref. 51 and printed with permission from Pergamon Press, Tarrytown, New York.)... 

Condensation in vertical tubes depends on the vapor flow direction and its magnitude. During downflow of vapor, if the vapor velocity is very low, then the condensate flow is controlled by gravity, and the Nusselt results for a vertical flat plate are applicable (unless the tube inside diameter is very small and tube wall curvature effects become important [36]). 

R. G. Sardesai, R. G. Owen, and D. J. Pulling, Pressure Drop for Condensation of a Pure Vapor in Downflow in a Vertical T tbeProc. 7th Int. Heat Transfer Conf, Munich, 5, pp. 139-145,1982. 

Vertical ln tube condensers—downflow. This configuration is popular in the chemical industry (68). It can lead to heat transfer coefficients even higher than shell-side condensation (319), and has distinct advantages for multicomponent mixtures if significant pressure drop can be tolerated. It also minimizes condenser costs when highly corrosive materials are handled (68). An application of this condenser t3 pe as an internal condenser is illustrated in Fig. 15.14d. 

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