Mass Transfer in a Liquid Film Falling Down a Wetted-Wall Tower

Wave-augmented mass transfer in a liquid film falling inside a vertical tube

“…At the laminar flow range of Re, the present measurements are in good agreement with Bakopoulos [3] correlation (Fig. 5), and Bakopoulos constructed the correlations at laminar and turbulent flow ranges mainly from the data of Kamei and Oishi [5] for 47.6 mm inner diameter tube, Hikita et al [4] for 27 mm inner diameter and Lamourelle and Shandall [6] for 16 mm outer diameter, respectively. Though our data have a 17% deviation from Bakopoulos correlation at the turbulent-flow range (Fig.…”

“…The revised correlations pass through or near the upper boundary of Kamei and Oishi's [5] and Hikita et al's [4] measurements which supplied the main body of the data for Bakopoulos' first and second correlations, while his existing correlations pass through or near the lower boundary (refer to Fig. 1 in [3]).…”

“…1 in [3]). Kamei and Oishi [5] and Hikita et al [4] formed films through overflowing, and Bakopoulos cited the serious difficulties in obtaining uniform distribution by overflowing especially at low flow rates. Bakopoulos' measurements of the mass transfer in a film discharged from an undulated annular distributor fall on or near the revised correlations and are larger than those in film discharged from a ring slot (refer to Fig.…”

“…Wave-induced convections are most intense at or near the film surface, and thus they drastically augment the mass transfer from the surface into the bulk of film and vice versa; otherwise the mass transfer rate is very small due to the low molecular diffusion. Several researchers measured the mean mass transfer coefficient k L in films falling down vertical walls at various flow rates as reviewed by Alekseenko et al [1], Roberts and Chang [2], Bakopoulos [3], Hikita et al [4] and Kamei and Oishi [5]. These measurements show that the mean mass transfer coefficient k L rapidly increases at small Re, after which the rate of increase suddenly drops at a certain Re and then continue to increase slowly until the turbulent-flow range of Re is reached whereby the coefficient starts to sharply increase again.…”

“…For practical use, Bakopoulos [3] constructed empirical correlations of the Sherwood number Sh as a function of Re at the three Re ranges for water films. He selected the measurements of Kamei and Oishi [5], Hikita et al [4], Lamourelle and Sandall [6] and Emmert and Pigford [7] where most of the data had been determined in 1 m or taller films, so that his correlations can neglect the effect of the film height or the smooth entry pass. Waves appear at some downstream distance on the entry smooth surface, and the length of the smooth entry pass increases with Re up to about 0.3 m [8].…”