D. A. Kazenin

Interfacial Mass Transfer in the Liquid–Gas System: An Optical Study

Mass transfer across the liquid–gas interface was studied by a number of optical methods: holographic interferometry in real time, polarization microscopy, shadow imaging, and modified surface-fluctuation spectroscopy. These methods visualize the evolution of the surface layer, the in-depth profile of density, and mass fluxes. Absorption and desorption of various gases by perfluorodecalin is discussed. The origination and development of irregularities in the diffusion–reaction zone were observed during chemical absorption of carbon dioxide by monoethanolamine and KOH solutions.

The time evolution of chemo-gravitational convection on a brim meniscus of wetting

By using optical interference microscope it becomes possible to visualize the generation and real time evolution of an instability generated by chemosorption of carbon dioxide with water solutions of a base at the brim meniscus of wetting. The reaction product is obtained at the interface in the form of droplets with the size increasing in time. At a definite size, the droplets begin to settle along the meniscus on the bottom as if the product was a new quasi-phase. It was found that in the case when liquid wets the experimental cell walls, the droplets move from walls to the center. Due to this fact, at the scale of a cell, the movement of the liquid is vortical. Liquid in the center of the cell moves down from the interface to the bottom, whereas along the wall it rises up to the interface.

Kinetic Model of Depth Filtration with Reversible Adsorption

A mathematical model of a depth filter that removes colloidal particles from suspension by reversible adsorption is studied. The filtration problem is analytically solved when the adsorption and peptization coefficients are written as a function of van der Waals, electrical double layer, and Born interaction potential energies. The solution is used to study the performance of a depth filter as a function of the size of colloidal particles, filtration velocity, specific filter surface area on which reversible adsorption takes place, and filter depth.

Motion of a gas slug in inclined tubes

The velocities of a freely rising gas slug and a phase boundary (gas-liquid) under conditions of liquid discharge in tubes of various diameters are experimentally studied. It is shown that the nonmonotonic character of the dependence of measured velocities on the angle of inclination is determined only by the curvature in the vicinity of the critical point of the head of the slug or the phase boundary during liquid discharge. Experimental results are obtained by measuring the profiles of curvature of the bubble head in mutually perpendicular planes. For these purposes, an appropriate computer program was developed, and an immersion optical procedure was used that made it possible to eliminate optical “noises” associated with the thickness of a tube wall.

Selection of membranes for deadend micro- and ultrafiltration outside-in hollow fiber filters

A mathematical model taking into account the adsorption of particles around a membrane pore mouth at the stage of standard blocking is developed. The model is used to study the effect of the average membrane pore size, the cutoff coefficient, and the ratio of the length of the pore inlet region to be blocked to the whole pore length on the product flow rate of a deadend outside-in hollow fiber filter. It is shown that the use of membranes with an average pore size higher than the cutoff diameter for the particles to be removed from the suspension will be profitable only for the first 15–20 min of operation. In this case, the membrane should have an average pore size as large as possible, but not exceeding a limit value at which the membrane selectivity can drop; the cutoff coefficient as low as possible; and a pore inlet region to be blocked as long as possible.

Hydrodynamics, mass transfer, and power consumption in air-core stirred tank reactors

Hydrodynamic and mass transfer processes in industrial air-core reactors stirred by flexible impellers are studied. Dimensionless-number correlations for determining the power consumption and mass transfer characteristics in designing laminar-and turbulent-flow stirred vessels are experimentally obtained. The dependence of the stirring power on key design parameters such as the number of blades, impeller rotational speed, and the viscosity of the stirred liquid is experimentally determined for a wide range of the Reynolds number. A radial distribution of circumferential velocities is experimentally measured and a correlation generalizing these experimental data for different impeller rotational speeds is obtained. A formula based on the value of the velocity lag determined by extrapolating the measurements of the profile of the liquid circumferential velocity is proposed. A method developed on the basis of the theory of surface renewal for predicting the phase contact time is proposed.

Some modern optical methods for the diagnostics of processes in multiphase granular media

Modern optical methods (mainly, immersion tomography) for studying the fluid flow and heat and mass processes in a granular medium flooded with a liquid are described. The transparency of this composite medium is provided by an appropriate choice of the refractive index of the saturating liquid. This makes it possible to use all available visualization methods, including polarization interference microscopy, for obtaining the information on the processes proceeding in the medium. Applications of the method to different engineering problems are discussed.

Effects of vortices on diffusion and heat transfer

The unusual phenomenon observed by D.I. Taylor and other researchers was explained. During the vortex motion of the liquid, the distributed component of the diffusing substance is concentrated only in the vortex core. The effect was explained in terms of our hypothesis that takes into account the dependence of the diffusing substance flow not only on the concentration gradients, but also on the vorticity of the liquid. The concept offers a new glimpse on natural and technical effects such as the tornado and the Ranque effect.