AC-3 Study of Backflow and Inert Accumulation in Air-Cooled Condensers

G. Breber and J. W. Palen
1981; rev 1989

The object of the report is to discuss possible causes of thermal under efficiency, which may be experienced even when an air-cooled condenser has been correctly designed and constructed. A way of identification and correction of possible operational deficiencies caused by blanketing of the heat transfer area by noncondensables is outlined. The study provides a quantitative but simple predictive method for the effective lengths of tubes in air-cooled condensers.

An analytical method was developed to determine the effective length of each tube which is not blanketed by noncondensables. The exchanger effectiveness approach was used to derive expressions for pressure drop in each row. The resulting simultaneous equations for determination of the effective length of the tube were solved numerically. The solutions, which can also be presented graphically, show the effective length of tubes to be solely a function of effectiveness. The determination of the effective lengths of the tubes in all rows allowed the development of equations for maldistribution of vapor and for the total capacity of the unit.

The presented method is applicable not only for horizontal but also for vertical bundles of tubes, smooth or finned, connected to the common inlet and outlet plenums.