ENHANCEMENT OF TRANSFER PROCESSES IN GRAVITY LIQUID-FILM FLOW .1. ANALYSIS OF THEORETICAL AND EXPERIMENTAL STUDIES

The transfer processes in film-apparatus can be enhanced due to two methods of thin liquid layer turbulence stimulation: 1) passive (constructional) caused by artificial roughness of the apparatus wall or by the sprinkling device and 2) active, resulting from the centrifugal forces' effect, mechanical film break off, wall vibration, liquid or gas pulsation, which requires and additional energy expenditure. In industrial film-apparatus the above mentioned methods are useful, but the first one is more interesting from the economical viewpoint. This paper presents the models of transfer processing in liquid film flowing down the rough surfaces and an analysis of experimental studies in the field. It has been shown that the models reported in the available literature are not numerous. From these only that proposed by KHOLPANOV et al. for turbulent film flow down the plates with perpendicular incisions of the optimal value of surface geometry gives the values of mass transfer coefficients comparable with experimental data reported by DAVIES and WARNER. The analysis of experimental literature data slows that the results obtained are incomparable. Heat and mass transfer enhancement factors defined as the ratio of the value of a given kinetic quantity obtained for rough wall surfaces to the equivalent value for smooth tube or plate permit comparing the results of various papers. Significant differences in qualitative and quantitative effects of geometrical and flow parameters have been shown.