O. V. Vitovsky

Experimental investigation of upward gas-liquid flow in a vertical narrow annulus

Abstract Flow structures in vertical upward two-phase flow in a concentric narrow annular channel have been studied. A map of flow patterns has been drawn. The frictional loss has been measured for the two-phase flow over a wide range of superficial liquid and gas velocities. A mathematical model predicting frictional loss has been developed.

Experimental investigation of adiabatic evaporation waves in superheated refrigerants

Propagation of adiabatic evaporation waves arising while refrigerants R-11 rapidly transit to metastable state due to depressurization in the rarefaction wave is experimentally investigated. New regularities of the interphase surface dynamics and the influence of interphase heat and mass transfer in propagation of adiabatic evaporation waves are obtained. It has been found that the phase transition in metastable liquid occurs in the conditions of developing multiscale turbulence in liquid and vapor phases under dynamic action of a vapor flow on the interphase surface and convective heat supply to the zone of high-intensity phase transition. The surface phase transition was visualized by a rapid video camera, its pulsating character is revealed and its properties are determined.

Methane Steam Reforming in an Annular Microchannel with Rh/Al2O3 Catalyst

Regularities of methane conversion in the presence of water steam were obtained experimentally while activating chemical conversions on the inner convex wall of an annular microchannel. The steam methane reforming was done on the Rh/Al2O3 nanocatalyst with the heat applied through the microchannel gap from the outer wall. Concentrations of the products of chemical reactions in the outlet gas mixture are measured at different temperatures of the outer microchannel wall. The range of channel wall temperatures at which the ratio of hydrogen and carbon oxide in the outlet mixture grows substantially is determined. Data on the composition of methane conversion products for the ratio H2O/CH4 = 1.77 and the activation energy of methane steam reforming at reactor outer wall temperatures of up to 880°C are obtained. The effect of the radiation heat exchange and the external diffuse limitation on the rate of chemical conversions in methane steam reforming in an annular microchannel with external heat supply is determined.

Hydrogen Production by Methanol Steam Reforming in an Annular Microchannel on a Cu-ZnO Catalyst

Steam reforming of methanol into a hydrogen-containing gas under activated methanol conversion on annular microchannel walls was experimentally investigated. The methanol conversion was carried out on a copper-zinc catalyst deposited on the channel internal wall. The concentrations of the chemical conversion products in the output gas mixture were determined at different reactor temperatures and residence times. The channel wall temperature range within which the methanol steam reforming is intensified was also determined. It was shown that the CO content in the reaction products is determined by the CO2 partial pressure rather than by the reactor temperature. A kinetic model of methanol steam reforming on a copper-zinc catalyst was developed.

Hydrodynamics and heat and mass transfer at chemical conversions in slot reactors

In this paper, experimental and numerical investigations of the hydrodynamics and heat transfer in a disk slot heat exchanger-reactor for a radial flow of a gas mixture reacting on the channel walls are described. Data for the coefficients of heat transfer from the wall being heated to the gas flowing inside the reactor are presented. The temperature field of a catalytically active reactor plate at heat release on it has been investigated experimentally. Calculations of the flow and heat transfer in a slot reactor element for a catalytic reaction with heat release have been performed. Partial oxidation of methane in an oxygen medium with the formation of a hydrogen-containing synthesis gas in a two-dimensional microchannel has been investigated numerically. Data for the extent of the chemical conversion of methane versus the initial mixture consumption and reaction temperature are presented.

Heat Transfer in a Flow of Gas Mixture with Low Prandtl Number in Triangular Channels

We investigated heat transfer in a channel with a triangular cross-section. The working medium is a helium–xenon mixture with a low Prandtl number. This channel configuration corresponds to one of possible cases of fuel cells layout in a gas-cooled nuclear reactor. New experimental data on heat transfer in helium–xenon mixtures were obtained. Results of numerical modeling were compared with the experimental data and the known empirical correlations.

Experimental Investigation of Heat Transfer in Helium-Xenon Mixtures in Triangle Channels

Correlations are obtained for resistance and heat transfer of a helium-xenon mixture with a helium mass fraction of 9.1% in a triangle channel for Reynolds numbers from 103 to 2.4 × 104 and thermal fluxes up to 9.3 kW/m2. It is shown that the resistances of the turbulent dependence are in agreement and the heat transfer corresponds to the Tetelbaum dependence.

Heat and Mass Transfer With Chemical Reactions Producing Hydrogen in Microchannels

The reduction of effective transfer length on microscale eliminates the external diffusion limitation on reaction rate and makes it possible to realize the non-equilibrium chemical reactions. The peculiarities of methane and carbon monoxide steam reforming in a minichannel reactor with activation of reactions on thin film catalyst prepared by nanotechnology are considered in this paper. Consistent accomplishment of these reactions can increase the hydrogen yield and reduce the concentration of carbon monoxide in the product. Steam reforming of methane was studied on Rh/Al2 O3 nanocatalyst deposited on the inner wall of the annular minichannel. Steam reforming of carbon monoxide was studied at Pt/CeO2 /Al2 O3 nanocatalyst deposited on the walls of the minichannel plate. The procedure of catalyst preparation which makes the nanoparticles of two nanometers in size is developed. The catalyst has uniform fraction of nanoparticles and optimal oxygen mobility in the lattice of carrier. During tests the data on the composition of the reacting gas mixture in temperature range from 200 C to 940 C were obtained including data on conversion in controlled temperature field when hydrogen content in the product reaches 68% and carbon monoxide content reduces to 1%. Methane steam reforming and water gas shift reaction in the minichannel were modeled numerically. The detailed information on the temperature and species concentration fields has been obtained, and kinetics of multistage reactions was defined when the external heat is supplied to proceed the steam reforming. The temperature regimes of high conversion of methane and carbon monoxide were defined and discussed in connection with the experimental data.Copyright