Condensation on horizontal tubes

For laminar film condensation on horizontal tubes Nusselt obtained the relation... 

J. M. McNaught, Two-Phase Forced Convection Heat Transfer During Condensation on Horizontal Tube Bundles, Proc. 7th Int. Heat Transfer Conf, Munich, 5, pp. 125-131,1982. 

The Diikler theory is applicable for condensate films on horizontal tubes and also for falling films, in general, i.e., those not associated with condensation or vaporization processes. 

Table 9.8. Average values of film coefficients hm for condensation of pure saturated vapours on horizontal tubes...

Shell-and-tube heat exchangers are also used extensively for condensing duties. Condensers can be horizontally or vertically mounted with the condensation on the tube-side or the shell-side. Condensation normally takes place on the shell-side of horizontal exchangers and the tube-side of vertical exchangers. 

EXAMPLE 10-7 Condensation of Steam on Horizontal Tube Banks... 

So, if a tube of length 3 m and diameter 0.029 m was chosen, then a mjhor = 2.46 am. Around 2.5 times more vapour condenses on a tube positioned vertically compared to on the same tube lying horizontally. 

Enhanced surfaces can often significandy increase the effective heat-transfer coefficient in condensation, especially if the condensing heat-transfer coefficient is the limiting factor in the overall heat-transfer-coefficient equation. Such enhancements include low fins on horizontal tubes, which increase the heat-transfer area, and fluting on vertical tubes and plane surfaces, which thins the condensate film over part of the surface by surface-tension effects. However, these improvements are limited by condensate retention between the fins and flooding of the drainage paths [7, 34],... 

For shell-and-tube condensation related topics include evaporation (Section 16.11.4.1) and distillation (Section 16.11.4.2). Prefer condensation outside horizontal tubes use vertical tubes when condensing immiscible liquids to subcool the condensate. Assume pressure drop of 0.5 of the pressure drop calculated for the vapor at the inlet conditions. Baffle spacing is 0.2 to 1 times the shell diameter with the baffle window about 25%. Limit pressure drop for steam to 7 kPa on the shell side. U = 0.5 to 0.85 kW/m °C. 

Reynolds number, however, for T for horizontal tubes is typically only about one-tenth for vertical tubes. On horizontal tubes the flow of the condensate film is virtually always laminar, whereas on vertical tubes it may not be and Eqs. 

One way of preventing inundation of condensate on lower tubes is to incline the tube bundle with respect to the horizontal. As the inclination angle increases, a critical value is reached where the condensate no longer drips off the tube but instead clings to the tube and flows to its base. Shklover and Buevich [66] conducted an experimental investigation of steam condensation in an inclined bundle of tubes and recommend an inclination angle of 5°. 

D. W. Nobbs and Y. R. Mayhew, Effect of Downward Vapor Velocity and Inundation on Condensation Rates on Horizontal Tube Banks, Steam Turbine Condensers, National Engineering Laboratory Report No. 619, East Kilbride, Glasgow, pp. 39-52,1976. 

P. J. Marto, An Evaluation of Film Condensation on Horizontal Intergral-Fin Tubes, 7 Heat Transfer, 110, pp. 1287-1305,1988. 

J. W. Rose, Models for Condensation on Horizontal Low-Finned Tubes, Proc. 4th UK Heat Transfer Conf, I. Mech. E., pp. 417-429,1995. 

T. Adamek and R. L. Webb, Prediction of Film Condensation on Horizontal Integral Fin Tubes, Int. J. Heat Mass Transfer, 33, pp. 1721-1735,1990. 

A. G. Michael, P. J. Marto, A. S. Wanniarachchi, and J. W. Rose, Effect of Vapor Velocity During Condensation on Horizontal Smooth and Finned Tubes, Heat Transfer for Phase Change, ASME HTD-Vol. 114, pp. 1-10,1989. 

TABLE 17.24 Heat Transfer Correlations for External Condensation on Horizontal and Inclined Tubes and Tube Bundles... 

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