Wave frequency of falling liquid films and the effect on reflux condensation in vertical tubes

Visual investigations of effective wave frequency, structure and formation of isothermal and fully developed falling liquid films inside vertical tubes are presented without and with countercurrent flow of vapour. These are supplemented by novel transmissivity measurements leading to considerable improvement of the established wave shape and liquid film structure classifications. In addition, reflux condensation heat transfer data evaluated for the limiting case of zero shear stress are represented in terms of the wave factor. These are correlated with Reynolds and Kapitza numbers and they are interrelated with the observed wave characteristics.