Optimal Regimes of Heat-Mass Transfer in a Falling Film

Abstract

For the first time, numerical simulations of mass transfer for real flow conditions have been made in a wavy liquid film falling down a vertical wall. Hydrodynamical parameters have been calculated by solving the Kapitsa-Shkadov system with a semi-parabolic velocity profile. Calculations have been performed with natural waves and forced waves. Optimal frequencies of forced inlet disturbances that enhance the mass transfer have been found along with the main mechanisms of the mass transfer. The calculated mass absorption has been compared with experimental data and a good agreement was obtained.Brought to you by | University of Arizona Authenticated Download Date | 5/27/15 2:35 PM

Three-dimensional localized coherent structures of surface turbulence. I. Scenarios of two-dimensional–three-dimensional transition

“…In this figure, we present experimental data for gas absorption to the film from the studies of Alekseenko et al, 2 Bakopoulos, 21 Nakoryakov et al, 22,23 and Seban and Faghri. 24 For more details, see Rastaturin et al 25,26 These experimental results indicate the existence of different points where the Sherwood number as a function of Reynolds number appears to have a discontinuity ͑in logarithmic coordinates͒. The first such point is close to ͗Re ͑2͒ ͘Ӎ40− 70 while the second one is located at ͗Re͘Ӎ400, close to ͗Re ͑3͒ ͘.…”

“…Quite recently, we have been able to obtain theoretical evidence of 2D-3D transitions at ͗Re ͑2͒ ͘ = 40− 70 by a direct numerical simulation of the coupled heat/mass transfer process and hydrodynamics in a falling film ͑Rastaturin et al 25,26 ͒. The results of these computations are shown as solid lines in Fig.…”

A numerical study of mass transfer from laminar liquid films

“…Accordingly, as can be seen from the figure, the mass flux in this neighbourhood remains close to zero for all times. As noted, among others, by Yoshimura et al (1996), Rastaturin et al (2006) and Dietze (2019), this liquid from the previous boundary layer is deflected under the separation streamline penetrating the large wave toward its rear face thus acquiring a velocity component normal to the interface. Interestingly, these streamlines do not reach the free surface at the back (to the left) of the wave but are deflected thus leaving a thin 'whisker' of relatively solute-rich fluid, particularly evident in frame (c), between themselves and the free surface on which, therefore, a new boundary layer forms; as cited in Yoshimura et al (1996) a similar pattern was also shown in a conference contribution by Nagasaki & Hijikata (1990).…”

“…As noted by several authors (see, e.g. Yoshimura et al 1996; Sisoev, Matar & Lawrence 2005; Rastaturin, Demekhin & Kalaidin 2006), these independent parameters have a strong effect on the transfer rates which cannot simply be attributed to either the large waves or the capillary waves. Secondly, as already noted in the literature (see, e.g.…”

Selection of solitary waves in vertically falling liquid films

“…a roll, appears in the main hump [25]: this mixing is a key element to transfer intensification [34]. At given flow conditions, the onset of recirculation regions is sensitive to the separation distance between waves and therefore to the frequency [24]. It is thus essential to determine the preferred wavelength of the natural evolution of the film.…”