Vapor-gas Mixture Research Articles

Теплоотдача при движении воды в трубе при температурах, близких к температурам кипения в переходном режиме

Currently, there is a problem of developing effective methods to calculate heat and mass transfer processes during steam condensation from a vapor-gas mixture in industrial devices. This is due to the need to create new reliable and highly efficient designs of heat exchangers for various purposes. The finite element method has been used in the ANSYS Fluent software package during the numerical simulation. An experimental plant is tested in the pipeline of an industrial enterprise at the production site of the Technopolis KHIMGRAD industrial park (Kazan-city). The applicability of the Lee model to solve problems of water flow in a pipeline with partial evaporation is proved. This model allows you to accurately account for the processes of evaporation and condensation, which is important for the design of cooling and air conditioning systems. The authors have designed a three-dimensional model of the flow area of the experimental module and a CFD model to calculate temperatures, phase velocities and their concentrations, considering the peculiarities of the ongoing processes of heat and mass transfer. A slight effect on the heat flow of a 180° rotation during the flow of a liquid medium in the range of the Reynolds numbers 1800–2600 is shown. The developed model is verified with the results obtained at the experimental plant. It is established that the model reproduces experimental data well. An analysis of studies of heat and mass transfer processes during the fluid flow in channels in the presence of phase transitions is carried out. The problems of calculating the parameters of heat transfer during the movement of a fluid in a transient mode are revealed, especially at values of the Reynolds number close to 2000. The experimental plant diagram is presented. It is found that in the range of Reynolds numbers of 2600–3600, the calculated temperature values differ from the temperature values obtained experimentally by less than 0,42 %. During the partial transition of water into steam in the range of Reynolds numbers of 1800–2600, the deviations were less than 6 %, which confirms the adequacy of numerical modeling of calculating the heat transfer process in a pipe. It is shown that considering the influence of temperature on surface tension, the coefficient of thermal conductivity of water and the coefficient of dynamic viscosity of water is important to obtain accurate results. The proposed approach can be used to optimize the operating parameters of condensers and evaporators, as well as to accurately calculate the heat transfer coefficient and determine the areas of vapor formation. It will improve the energy efficiency of industrial installations and reduce the cost of equipment operation.

High-temperature corrosion testing of titanium beryllides in the presence of water vapor and oxygen

Beryllium-based intermetallics are promising materials for the blankets of future fusion reactors and have potential applications in other areas of the nuclear industry, such as fission reactor reflectors and space technology. Understanding the high-temperature corrosion behavior of these materials in a noble gas medium containing chemically active impurities is essential for evaluating their suitability and guiding their application.This study investigates the high-temperature corrosion of titanium beryllide Be12Ti in the form of plate and grinded samples, produced by JSC “Ulba Metallurgical Plant” (Ust-Kamenogorsk, Kazakhstan). The corrosion tests were conducted under non-isothermal vapor-gas mixture (Ar + D2O or Ar + H2O flowing atmospheres) purging conditions using thermogravimetric (TG) analysis, differential scanning calorimetry (DSC), and mass-spectrometry of the gas phase.As a result of the corrosion tests, new experimental data on thermal effects have been obtained, describing the corrosion processes of Be12Ti samples across a wide range of temperatures and various heating rates in the presence of water vapor in the purge gas. The dependencies of sample mass change under heating conditions have been determined, and the characterization results of the samples before and after high-temperature corrosion tests are presented.Corrosion of titanium beryllides, both for Be12Ti plate and grinded samples, follows similar mechanisms. At around 500 °C, the mass of the samples begins to increase, and hydrogen isotopes are released. The test results indicate that corrosion of titanium beryllides with varying surface inhomogeneities proceeds similarly within the temperature range of 500–900 °C, showing a linear dependence on temperature.The results revealed significant insights into the oxidation mechanisms and the formation of corrosion products, which are crucial for optimizing the material's performance in fusion reactor environments.

Condensation of a Vapor-Gas Mixture Containing Solid Particles on the Surface of Finned Pipes

Condensation of a Vapor-Gas Mixture Containing Solid Particles on the Surface of Finned Pipes

Effects of Nozzle Configuration on Efficiency of Direct-Contact Gas-Vapor Mixture Generators

Effects of Nozzle Configuration on Efficiency of Direct-Contact Gas-Vapor Mixture Generators

Using methane hydrate to intensify the combustion of low-rank coal fuels

Coal mining and processing waste amounts to hundreds of millions of tons annually. Piles of coal refuse pollutes the air with dust and has a risk of self-ignition. However, it can be put to good use as an alternative energy source. To reduce the gas emissions released from its combustion and to increase its integral characteristics, this research suggests co-firing coal mining waste with a gas-vapor mixture formed upon hydrate heating. The corresponding experiments were conducted using a newly developed experimental setup with a boiler unit. The experimental findings were used to obtain an equation for predicting the flame length required for the effective combustion of waste coal. The use of methane hydrate was found to increase the fuel combustion temperature and minimize the unburned carbon. It also provided a significant reduction in the toxic gas emissions (sulfur and nitrogen oxides). A conceptual technological solution has been developed for the co-combustion of gas hydrate with coal and coal mining waste. This technology will help with heating hard-to-reach settlements, producing clean water for population and equipment, as well as recovering slime waste.

APPLICATION OF ATOMIC OXYGEN FOR GASOLINE OCTANE NUMBER DETERMINATION

There is a method that measures the thermal effect of a low-temperature oxidation reaction to determine the octane number of gasoline. The reaction was conducted in the presence of ozone on a thermistor surface at a temperature of the vapor-gas mixture equal to the end boiling point of gasoline in order to lower the analysis temperature. Keywords: low-temperature oxidation, atomic oxygen, gasoline, detonation resistance, octane number, ozone, and thermistor.

DUST COLLECTION EFFICIENCY UNDER IN-PHASE TURBULENCE CONDITIONS IN THE PRESENCE OF PHASE TRANSITIONS

The article presents the results of a study of the dust collection efficiency in a regular packing layer of a rotoclone-type hybrid apparatus on the particle inertia index in the presence of phase transition processes. The effect of phase transitions on the efficiency of gas purification processes under inphase turbulence conditions is considered. Based on the conditions of stability of the in-phase vortex formation regime of the gas phase in a regular packing layer, the dominant influence of turbulent diffusion mechanisms on the intensity of phase transition processes and, as a consequence, on the dust collection efficiency has been established. In this case, the predominant influence is in the area of highly dispersed and finely dispersed dust fractions. The results of the experimental studying the patterns of dust collection efficiency depending on the particle inertia index in the presence of phase transition processes are presented. The studies were carried out for three phase transition modes: condensation of vaporsfrom a vapour-gas mixture, evaporation of a spraying liquid as well as a neutral mode. Using A.N. Kolmogorov’s hypothesis,the basic equations and results of calculating the numerical values of local characteristics of a turbulent gas flow in a regular packing layer are presented under the assumption of isotropic turbulence realized in a layer of a regular packing, whose local characteristics do not depend on coordinates and direction.

High-temperature interaction of water vapor with lithium ceramics Li2TiO3

Selection of materials for fusion reactors and, in particular, for blanket systems is one of the most important tasks that determine the development of fusion energy. Lithium ceramics Li2TiO3 is considered as prospective candidate for solid breeders of future fusion reactors' blankets. The paper presents the results of high-temperature tests of Li2TiO3 + 5 mol% TiO2 ceramics, performed under conditions of blowing with argon containing impurities of water vapor of different isotopic compositions (H2O, HDO, D2O) in the range of temperature from 100 °C to 1400 °C. The vapor–gas mixture for the experiment was prepared in a special mixing tank. The interaction of Li2TiO3 + 5 mol% TiO2 ceramics with chemically active gases and water vapors was investigated by thermogravimetry (TG), differential scanning calorimetry (DSC) and mass spectrometry (MS) methods. As a result of experiment, the dependences of the sample mass change during heating under single purge gas composition was obtained. Mass spectra that characterize the changes in the qualitative composition of the gas mixture in the reaction chamber with the investigated sample were recorded and subsequently analyzed. An isotope effect is observed during the experiment: the release of D2 gas begins significantly earlier than the release of HD gas. The observed effect appears only in the high-temperature region (above 1050 °C), which characterizes the investigated material as almost completely chemically neutral towards water vapor.

Рекуперация и очистка газовых выбросов целлюлозного производства

For pulp production, large-scale enterprises have been built which, while in operation, are subject to new requirements, different from the design ones, for economic efficiency, labour safety, as well as impact on the local population and the environment. Significant success in this work has been achieved by changing the liquor recovery technology, switching to burning black liquor of increased concentration, which makes it possible to almost completely eliminate the largest source of hydrogen sulfide and methyl mercaptan emissions with flue gases, reduce sulfur losses and improve energy efficiency of soda recovery boilers. Another significant source of soda recovery boiler emissions is a smelt dissolving tank vent. An important technological operation of dissolving molten sodium salts with weak white liquor supplied from the causticization shop takes place in the tank. The modern development of smelt leaching technology is related to the improvement of equipment compatible with the technology of regeneration of chemical reagents for pulp production. Heat exchangers and gas purifiers of “gas-liquid” systems, easier to adapt to technological requirements compared to other systems, are installed on the dissolving tank vent. The installation of such equipment provides the change in the smelt leaching technology, and affects the technology of causticization and lime recovery. This article covers the research of the relationship between the technical solutions ensuring the safety of personnel in the boiler shop, heat and chemicals recovery, as well as purification of gas emissions and the changes in the technology of smelt leaching in the soda recovery boiler of the pulp mill. On the basis of experimental data and a mathematical model of the movement of the vapour-gas mixture in the smelt dissolving tank vent, the technological feasibility of installing heat exchangers at different heights of the vent and the possibility of effective purification of gas emissions using a direct-flow sprayer have been considered. The applicability of the irrigation of the steam-gas flow with weak white liquor, which is formed during the cycle of chemical regeneration in pulp production, as well as the conditions for ensuring reliable operation of gas purification equipment, have been investigated. The quantitative characteristics of the necessary change in consumption and composition of weak white liquor and the methods of its supply to the dissolving tank have been obtained.

MODELING OF THREE-LAYER FLOWS WITH NON-UNIFORM EVAPORATION BASED ON THE EXACT SOLUTION OF CONVECTION EQUATIONS

Mathematical modeling of three-layer convective flows of two liquids and a gas-vapor mixture in a horizontal channel is based on the exact solution of the Navier-Stokes equations in the Boussinesq approximation. Thermocapillary interfaces are assumed to be non-deformable. The inhomogeneous mass transfer of the light liquid to the upper layer is considered. The Soret and Dufour effects are taken into account in the upper layer, and the gas flow rate is given. The influence of thermal load and flow geometry on the main characteristics of the flow was studied using the example of the water–benzine–air system. It is shown that the Soret effect has an impact on the nature of the flow. The influence of the effect of thermodiffusion, changes in the longitudinal temperature gradients, and thicknesses of the layers of the system on the dew point is revealed.

АНАЛИЗ РАБОТЫ ДВУХСТУПЕНЧАТОЙ ГИДРОЭЖЕКТОРНОЙ ВАКУУМСОЗДАЮЩЕЙ СИСТЕМЫ, ОПРЕДЕЛЕНИЕ ЕЕ ОПТИМАЛЬНЫХ ТЕХНОЛОГИЧЕСКИХ ПАРАМЕТРОВ

The article considers the features of the operation of hydro-ejector vacuum-generating systems. The diagram of a two-stage hydro- ejector vacuum-generating system is described, and a calculation algorithm is given. The dependence of the yield of the components of the vapour-gas mixture on the temperature of the working fluid was analyzed, and the required heating temperature of the working fluid was determined. A calculation of a two-stage hydraulic ejector vacuum-creating system was made, and the dependence of the flow rate of the working fluid on the pressure and power consumption of the pumps was determined.

Calculation of Sediment Formation on Finned Heat Exchanger Tubes on Condensation of a Vapor–Gas Mixture with Solid Particles

Calculation of Sediment Formation on Finned Heat Exchanger Tubes on Condensation of a Vapor–Gas Mixture with Solid Particles

РАЗРАБОТКА, ИССЛЕДОВАНИЯ И ОПЫТНО-ПРОМЫШЛЕННОЕ ОСВОЕНИЕ ТЕХНОЛОГИИ АГЛОМЕРИРОВАНИЯ ТЕХНИЧЕСКОГО УГЛЕРОДА

The article examines the issues of agglomeration of polydisperse technogenic materials with low bulk density, in particular carbon black (CB). Patent-protected technical solutions and technology for processing organic solid technogenic materials obtained by processing MSW by low-temperature thermolysis (T≤500 C) are presented. Distinctive features of the developed technical means are: sealing loading and unloading units without access to air oxygen, geometric profile and configuration of internal working parts, a system for aspiration and condensation of a vapor-gas mixture, etc. A patent-protected design of a drum-screw unit for agglomeration of technical specifications of low-temperature thermolysis technology has been presented. Specification studies have been carried out, obtained by processing organic solid municipal waste using low-temperature thermolysis. A mechano-rheological model of the agglomeration process of the material under study has been developed. Theoretical studies of the mechano-rheological model of stage-by-stage agglomeration of polydisperse materials have been carried out. The fundamental principles of organizing technological processes of granule formation at each stage of material processing and granulate classification have been established. The necessity of using elements (Hooke, Newton, Saint-Venant, etc.) and mechano-rheological models of volumetric-spatial orientation of CB particles and agglomerated granulate constructed on their basis at various stages is substantiated. The combination of elements used in the models of Maxwell, Bingman, Shvedov, etc., at each stage of the agglomeration process is theoretically justified. On the basis of theoretical studies and modeling of stage-by-stage agglomeration processes, special devices have been developed, implemented in the patent-protected design of a combined-action drum-screw unit (DSU CA). Design documentation has been developed and a pilot industrial sample of BVA CD has been manufactured for agglomeration of technogenic polydisperse materials

Gas Discharge Source of Synchronous Flows of UV Radiation and Silver Sulphide Microstructures

The results of the study of the characteristics of a pulsed source of time-synchronous UV radiation streams of silver atoms and ions and micro-nanostructures of silver sulfide are given. An overvoltage nanosecond discharge was ignited in nitrogen between electrodes made of silver sulfide (Ag2S) at a distance between electrodes of 2 mm. Silver sulfide vapors were introduced into the gas-vapor mixture "Nitrogen - Ag2S" due to the ectonic mechanism. The voltage and current pulses, the pulsed power of the discharge, the energy contribution to the plasma for one pulse at pulse repetition frequencies of 40-1000 Hz were studied. The spectral characteristics of the discharge and the spatial characteristics of the microstructures deposited from the discharge plasma on a quartz substrate installed near the electrode system were studied.
 The discharge can be used as a source of bactericidal radiation and a source of microstructures based on silver sulfide, as well as a plasma chemical reactor for the synthesis of thin microstructured films of silver sulfide.

Vapor-phase deposition of polymer siloxane coatings on aluminum and magnesium alloys

Adsorption and polymerization of vinyltrimethoxysilane (VS) on the surface of aluminum AMG and magnesium alloy M20 in the presence of water vapor and ethylene glycol (EG) was investigated. It is shown that ethylene glycol is an effective polymerization promoter due to the crosslinking of hydroxyl and ethanol groups during polycondensation of VS and EG molecules on the surface of alloys. The main factors influencing the polymerization rate and protective properties of coatings are determined. Using XPS methods, it was found that ethylene glycol molecules interact with magnesium hydroxides to form magnesium glycolate polymolecules in the form of developed three-dimensional structures. The variation of the composition of the vapor-gas mixture makes it possible to obtain protective coatings with a different ratio of siloxane and poly-oxy magnesium structures. Azeotropic mixtures of vapor-gas deposition of coatings and optical methods for controlling the chemical composition of working solutions have been developed. Electrochemical and EIS studies of siloxane coatings on smooth and oxidized surfaces of alloys have been carried out. Impregnation of oxidized aluminum and magnesium alloys with organosilanes by vapor-gas gas deposition significantly increases their corrosion and mechanical resistance.

Gas Discharge Point Source of UV Radiation Based on Argon–Copper Gas–Vapor Mixture

Gas Discharge Point Source of UV Radiation Based on Argon–Copper Gas–Vapor Mixture

Investigation of Characteristics and Parameters of Plasma of an Overstressed Nanosecond Discharge in Krypton between Electrodes Made of a Superionic Conductor – Silver Sulfide

The results of a study of the electrical and optical characteristics of an overvoltage nanosecond atmospheric pressure discharge between electrodes made of a superionic conductor (Ag2S) in krypton are presented. The destruction of electrodes in the discharge and the introduction of Ag2S vapor into the interelectrode gap occurred due to microexplosions of inhomogeneities on the working surfaces of polycrystalline electrodes (the formation of ectons) in order to synthesize thin films based on this compound on the surface of a dielectric substrate which was installed near the electrodes. By numerically solving the Boltzmann kinetic equation for the electron energy distribution function, the temperature and the electron density in the discharge, the specific discharge power losses for the main electronic processes, and the rate constants of the electronic processes depending on the parameter E/N for the plasma of vapor-gas mixtures based on krypton and silver sulfide have been calculated. Homogeneous thin films based on silver sulfide were synthesized on the quartz substrates by the gas-discharge method under conditions of ultraviolet assisted discharge plasma.

Computational Fluid Dynamics Modeling of Steam Condensation in the Presence of Noncondensable Gas in Inclined Tubes

In this paper, film condensation of steam in inclined tubes in the presence of noncondensable gases is modeled using numerical method. A single-phase fluid model incorporating a wall-function boundary condition is proposed to simulate the heat and mass transfer interaction between the liquid condensate and the gas-vapor mixture region. A user defined function is implemented to impose the proposed boundary to the governing equations for steady state incompressible flow. The performance of applying this boundary condition and subsequent treatment of the heat transfer at the liquid-mixture interface is validated against published experimental results. The calculated profiles of local and average Nusselt number for various inlet conditions compares favorably to the previous published experimental results and correlations. For all simulated cases, increases in inlet and bulk concentrations of noncondensable gases resulted in a decrease in the thermal performance of the condensing tube. Additionally, it is found that the inclination angle of the condensing tube can impact the local distribution of the heat transfer coefficient and Nusselt number, while there is only small effect on the average along the length of the entire tube.

Заправно-нейтралізаційна станція. Нові розробки та аспекти використання

The article dwells on development and study of the multifunctional operations while preparing propellant components for launch vehicle tank filling by high-boiling propellant components at the neutralization stations. The article considers the preparation of propellant for filling the launch vehicle stages with high-boiling propellant components of nitrogen tetroxide (oxidizer) and unsymmetrical dimethyl hydrazine (fuel) in terms of propellant saturation with helium and denitrogenation. Usually these issues refer to the common technology of propellant preparation and are tackled sequentially: first, propellant is drained into the filling tank of the filling system, then the propellant is denitrogened, for example purging the propellant by helium under atmospheric pressure in the tank, then propellant is saturated with helium to the given concentration by bubbling helium in the propellant, maintaining the set pressure of helium in the tank. This technology significantly complicates the process of propellant preparation, increases helium consumption, as well as the amount of the generated vapor, which requires recycling in the neutralization units. This article studies multifunctional operations, where the propellant is simultaneously drained from delivery vehicles, saturated with helium and denitrogenated. Amount of residual nitrogen in the propellant and the main direction of deep denitrogenation of the propellant are calculated. Amount of generated vapor and consumed helium are determined. The process of propellant draining by extrusion, maintaining the given pressure in the tank and alternating the propellant drain on the closed vent device (compression) and open vent device (decompression) is studied. As a result, the theoretical justification of multifunctional operations in preparation of high–boiling propellant components to fill the launch-vehicle stages is presented. Key words: saturation with helium and denitrogenation of the propellant, drain with closed vent device, excessive pressure draining, gas-vapor mixture, neutralization system.

Falling film evaporation in a partially heated parallel plate channel: Elliptic numerical analysis with an excess moisture condensation model

A fully coupled elliptic numerical method is used to conduct a detailed numerical analysis of laminar water falling film evaporation with a co-current laminar gas vapour mixture flow inside a partially heated vertical parallel plate channel. In order to obtain a fully coupled implicit solution, a complete set of elliptic two-phase two-dimensional governing equations is solved. The liquid-gas interface is obtained over a non-orthogonal structured moving mesh (grid) during the solution process. An excess moisture condensation model is proposed as a novel numerical method to address supersaturation in the system. Comparisons with the previous studies are made to verify the accuracy and capability of the present numerical model. The effects of the liquid and mixture Reynolds numbers variation on the hydrodynamic and thermal characteristics of the evaporation process inside the partially heated channel are investigated. Thermal and solutal buoyancy effects are seen in the form of recirculating flow in the gas phase.