bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flow structure and heat transfer in a turbulent vertical bubbly flow downstream of a sudden duct expansion
Authors: Chinak A.V. , Lobanov P.D. , Pakhomov M.A. 
Published: November 2019

Abstract
The flow structure and heat transfer in bubbly flows in a sudden duct expansion were studied. The data was obtained both in a pipe and a flat channel with a sudden expansion. Measurements are performed using shadow photography and PIV/LIF system. For modelling two-phase bubbly flow the set of RANS equations is used. Reynolds stress transport model is used to predict the turbulence of the liquid phase. The influence of sudden channel expansion on the distribution of bubbles and it`s velocity is shown. It is shown, that in the pipe with sudden expansion there are not a strong influence of bubbles on the hydrodynamical structure and heat transfer in the flow recirculation zone. In a contrast, in the vertical channel with back facing step the strong increasement of void fraction were found in similar region. It can result in increasement of heat transfer.
Formation of thermocapillary structures in heated liquid film
Authors: Chinnov E A 
Published: November 2019

Abstract
Data on the formation of thermocapillary structures and breakdown of a heated liquid film flowing down a vertical surface with Reynolds number variation from 0.1 to 500 have been analyzed and generalized. Small-scale thermocapillary structures are distinguished. It is shown that the distances between temperatures heterogeneities (rivulets) of thermocapillary structures do not depend on the Reynolds number. It is determined that the interaction of waves with thermocapillary structures leads to an increase in the critical heat flux corresponding to the liquid film breakdown as compared with the data of publications.
Effect of steam supply to the air-blown gasifier on hot syngas desulphurization
Authors: Nikitin A D , Abaimov N A , Butakov E B , Burdukov A P , Ryzhkov A F 
Published: November 2019

Abstract
The IGCC technology serves to efficiently produce thermal and electrical energy with minimal impact on the environment. In operating IGCC, wet desulphurization is used at temperatures below 200°C. The use of hot desulphurization at temperatures around 500°C will significantly improve IGCC efficiency. The preferred sorbent for hot gas cleaning is ZnO. At temperature of 450-500°C, ZnO begins decomposing because of reactions with syngas components (primarily hydrogen). Steam impedes reaction of ZnO with H2 and increases ZnO thermal stability. Syngas H2/H2O ratio is determined by gasifier operation mode. The purpose of this work is to determine maximum temperature of hot gas cleaning depending on condition of ZnO-sorbent thermal stability and steam-air-blown mechanically activated coal gasifier operation mode. To determine the effect of steam supply to syngas composition, experiments were performed on entrained-flow gasifier (1 MW). Experimental results were processed using thermodynamic analysis to determine idealized syngas composition and CFD-modeling to determine real experiment process parameters. Syngas H2O content was determined by CFD-modeling results. Study of ZnO-sorbent thermal stability depending on H2 concentration and syngas H2/H2O ratio was performed by TGA. As a result of experimentally confirmed thermodynamic calculations, ZnO-sorbent thermal stability was found to increase to 815°C due to steam dilution.
Investigation of applicability area for turbulence models in the problems of mass transfer intensification by the control of a rotary divergent flow
Authors: Kabardin I.K. , Pravdina M.Kh. , Yavorsky N.I. , Polyakova V.I. , Meledin V.G. , Ezendeeva D.P. , Kakaulin S.V. , Gordienko M.R. , Kulikov D.V. , Sadbakov O. Yu. , Klimonov I.A. , Usov E.V. 
Published: November 2019

Abstract
The fundamental scientific problem of this kind arises in mechanics, chemistry and catalysis in the intensification of mass transfer. The turbulent mass transfer characteristics were analyzed experimentally in a controlled rotational-divergent flow. The laser Doppler anemometry was used for turbulent mass transfer diagnostic. The verification of numerical calculations by computational hydrodynamics has been carried out according to the results of experimental studies. Calculation of turbulent kinematic is build on solving of a system of continuity and the Navier-Stokes equations. The fluid is incompressible and isothermal. For averaged equations closure, semi-empirical turbulence models were used: the k-ε model of turbulence and the Reynolds stresses transfer model. The calculation has showed the existanceof a near-wall jet after a rotating device and the generation of reverse flow zones. Comparison with experimental data has shown that all models of turbulence adequately model the rotational-divergent flow only until the formation of flow gaps and the formation of reverse flow zones. The discrepancy with the experiment occurs while controlling the flow to equalize the velocity profiles.
Investigation of high speed steam jet effect on combustion of substandard liquid hydrocarbons
Authors: Kopyev E.P. , Anufriev I.S. , Osintsev Ya.A. , Mukhina M.A. 
Published: November 2019

Abstract
Combustion of liquid hydrocarbon fuel dispersed by superheated steam jet was experimentally studied. Characteristics of the combustion process (heat release, emission of toxic products, flame temperature) were investigated in a laboratory direct-flow atmospheric burner (capacity up to 20 kW) at different operating systems with waste transmission automotive oil as fuel example. Regimes were found which provoke stable combustion of non-quality liquid hydrocarbons. It was shown dependences of heat, flue gas parameters on superheated steam flow rates, fuel flow rates, flame temperatures.
Effect of the angle of rotation of structured packing layers on separation efficiency in distillation column
Authors: Pavlenko A N , Pecherkin N I , Zhukov V E , Nazarov A D , Meski G , Houghton P 
Published: November 2019

Abstract
It is well known that a good quality of liquid distribution over the surface of structured packings is crucial for high performance of large diameter columns. The angle of rotation of the packing layers and their number are among the main parameters characterizing the distribution of liquid in a structured packing over the column cross-section and height. This paper presents investigation results on the influence of the rotation angle of structured packing layers on separation efficiency, pressure drop, distribution of local composition of mixture and local liquid flow rate under the packing. The experiments were carried out in distillation column with the internal diameter of 0.9 m on a structured packing with a specific area of 500 m2/m3, and the corrugation angle of packing equal to 45°. The mixture of refrigerants R114 and R21 at the pressure of 3 bar and total reflux was used as the working fluid. The column was packed with 11 packing layers with rotation angles of 20, 45, 70, and 90 degrees. According to experimental results, a decrease in the angle of packing layer rotation from 90 to 20 degrees leads to a decrease in separation efficiency, while the HETP value increases by 10–12%.
Effect of the wall properties on the shock wave / laminar boundary layer interaction
Authors: Kutepova A I , Polivanov P A , Sidorenko A A 
Published: November 2019

Abstract
The CFD calculations have been performed based on RANS approach with the Menter transition model [1]. The boundary layer developing on a flat plate was considered. To generate the incident shock wave, a wedge was installed over the plate. The wall was represented by one cm thick solid flat plate made from aluminum and polyacetal. Flow parameters were M∞=1.41, P0=0.7 bar, T0=293K. As a result of solving the conjugate heat transfer problem, the SWBLI flow was studied. The temperature and pressure distributions on the wall for different surface materials were obtained. It was found that the streamwise heat fluxes inside the wall can lead to a change of the separation zone length.
Stretched flame behavior in a planar meso-scale channel with heat conducting walls
Authors: Mokrin S , Sharaborin D , Odintsov E , Uriupin G , Minaev S 
Published: November 2019

Abstract
The influence of the wall on flow field, combustion regimes and flame extinction limit of premixed methane/air flames stabilized in the planar channel with heat conducting walls was experimentally investigated. Experimental data were compared with the results obtained in previous theoretical works. The influence of channel walls on gas flow was estimated by using PIV experiments with non-reacting gas flow and compared with the results of numerical simulation.
Experimental research of supersonic flow heat transfer in the wake of a backward-facing step
Authors: Leontiev A I , Popovich S S , Vinogradov Y A , Strongin M M 
Published: November 2019

Abstract
The results of an experimental study of heat transfer for a supersonic flow behind a backward-facing step are presented. Input flow Mach number was 2.2, Reynolds number was over 20 million when calculated with the use of the dynamic boundary layer length from the critical section to the exit section of the nozzle. The height of the step ranged from 8 to 14 mm. The thickness of dynamic boundary layer for plane model flow was about 6 mm in the region of nozzle exit section. The heat transfer coefficient and adiabatic wall temperature for the wake flow behind the step have been analysed in comparison with the plane model flow. The experiment was made with the use of chromel-kopel thermocouples with thermal compensation of cold junction, stagnation and static pressure meters, NI LabView powered programs of experimental automation. The graphs of the wall temperature, stagnation flow temperature, adiabatic wall temperature, the stagnation and static pressure, the distribution of the temperature recovery coefficient and the relative Stanton number along the model length are presented.
A laboratory setup based on porous burner for coal particles combustion investigation
Authors: Ponomareva A A , Tcoi K A , Mokrin S N , Shtym K A 
Published: November 2019

Abstract
In this work, physicochemical features, thermal behaviour, and combustion properties of a coal dust of Pavlovskiy brown coal were studied. For investigations of kinetic properties of fine coal particles combustion, the laboratory-made setup was developed and constructed. An experimental research on the properties of fine coal particles was carried out. Additionally, thermophysical characteristics of coal dust, compositions of thermal decomposition products and particle size distribution were investigated.
Results of Thermal Tests of Recirculation Cooling Installations
Authors: Balunov Boris , Lychakov Vitalii , Egorov Mikle , Sheglov Andrey , Suhorukov Yurii 
Published: November 2019

Abstract
The article presents the results from thermal tests of some recirculation installations for cooling air in nuclear power plant premises, including the volume under the containment. The cooling effect in such installations is produced by pumping water through its heat-transfer tubes. Air from the cooled room is blown by a fan through a bundle of transversely finned tubes and is removed to the same room after having been cooled. The finning of tubes used in the tested installations was made of Grade 08Kh18N10T and Grade 08Kh18N10 stainless steels or Grade AD1 aluminum. Steel fins were attached to the tube over their entire length by means of high-frequency welding. Aluminum fins were extruded on a lathe from the external tube sheath into which a steel tube had preliminarily been placed. Although the fin extrusion operation was accompanied by pressing the sheath inner part to the steel tube, tight contact between them over the entire surface was not fully achieved. In view of this, the air gap’s thermal resistance coefficient was introduced in calculating the heat transfer between the heat-transferring media. The air gap average thickness was determined from the test results taking into account the gap variation with temperature due to different linear expansion coefficients of steel and aluminum. These tests were mainly aimed at checking if the obtained thermal characteristics were consistent with the values calculated according to the standard recommendations with introduction, if necessary, of modifications to those recommendations.
Experimental investigation of freon mixture spreading over the structured Sulzer 500X packing at single drip point irrigation
Authors: Zhukov V E , Pavlenko A N , Yu Slesareva E , Pecherkin N I , Meski G , Houghton P. 
Published: November 2019

Abstract
The paper presents the results of experimental studies on liquid spreading over the Sulzer 500X packing at single drip point irrigation. The experiments were carried out using a 10% mixture of R114/R21 freons on one packing layer with a diameter of 0.6 m. The flow rate of liquid flowing from the lower edge of the packing was measured automatically by a flow meter moving along the packing sheets with a given step. The flow meter used volumetric measurement method. The receiving collector of flow meter is 50x50 mm in size, operating range of flow measurement is 0.05–50 ml/s. Distributions of liquid over the packing were measured at single-jet irrigation in the range of jet flow rates 2.5 < q
irrig < 60 ml/s. Spreading zone in the case of irrigation by a single jet is limited by the corrugation channels coming from the irrigation point. The pattern of spreading at low-flow jet irrigation has the shape of a dome with a low flow rate at the outlet of corrugation channels, which limit the spreading zone. With an increase in the flow rate, the share of liquid in these channels increases and dominates over other parts of the spreading zone.
Pore scale numerical simulation of heat transfer in propagating thermal wave during filtration combustion of rich and lean methane-air mixtures
Authors: Yakovlev I A , Zambalov S D 
Published: November 2019

Abstract
The porous media combustion phenomenon was numerically studied with focus on the heat transfer effect in propagating combustion wave for lean and ultra-rich mixture compositions using the approach when the three-dimensional porous structure and interstitial flow are simulated directly at pore scale with explicit consideration of the thermal interaction between fluid and solid phases including the detailed chemical kinetics model and solid-to-solid radiation. The results demonstrate that irregularity of the porous structure leads to a large spatial variation of the process parameters and the flow inhomogeneity. The most intensive heat sources placed within the cavities where the flow is developed. During the process, the interface heat transfer and radiation contribute to heat recuperation mechanism that leads to thermal non-equilibrium in the combustion wave. The heat is transferred through the bed via radiation layer-by-layer due to restricted visibility of the particles. The numerical data about a local variation of the process parameters were presented. The data of this type can be used for modification of the volume-averaged models within the context of spatial variation consideration. It was shown that there is a correlation between the heat release rate, the interface heat flux, the radiative heat flux, and its root mean square values.
Heat transfer and dynamics of transient processes at liquid film flowing on smooth and modified surfaces
Authors: Pavlenko A N , Kuznetsov D V , Volodin O A , Zubkov N N 
Published: November 2019

Abstract
The paper presents the results of an experimental study on propagation dynamics and structure of the wetting front under adiabatic conditions and on a preheated surfaces with a needle-like microstructure, as well as heat transfer and critical heat fluxes at a film flow of liquid nitrogen. The surface was structured by the method of deforming cutting (MDC). A comparison with the data obtained on a smooth plate was performed. Data of high-speed video of the processes are presented.
The heat transfer crisis in shear driven water film
Authors: Cheverda V V , Ponomarenko T G 
Published: November 2019

Abstract
In this work the authors demonstrate efficiency of thin water film, shear driven by gas flow in the mini-channel with local heater. The effect of microgrooves on heating surface is demonstrated. It is shown that microgrooves on the heating surface can provide an increase in the critical heat flux due to the capillary effect of microgrooves.
Vapour bubble dynamics in a flat mimi-channel under intense heating
Authors: Belosludtsev V V 
Published: November 2019

Abstract
Investigation of subcooled nucleate boiling in minichannels was conducted with high speed recording optical system also equiped with high spatial resolution optics. Obtained data on the bubble dynamics is in good agreement with well-known correlations from the literature. The final stage of bubble dynamics is in good agreement with the Labuntsov correlation for spherical vapor bubble growth on a heated wall.
Simulation of flows with phase transitions and heat transfer using mesoscopic methods
Authors: Kupershtokh A L , Medvedev D A 
Published: November 2019

Abstract
We use mesoscopic lattice Boltzmann and phase-field methods to simulate the growth of crystals from supercooled melt in the presence of melt convection and the behavior of a pinned droplet under the action of the electric field. In the first problem, the flow influences significantly the shape and the stability of growing patterns, leading to the enhanced development of fingers in the direction opposite to the flow. In the second problem, after the application of the electric field, the droplet begins to elongate in the field direction and the oscillations are produced. These oscillations decay in time due to a viscosity of a fluid. After several oscillations, the droplet acquires its equilibrium shape. The contact angle is essentially reduced compared to the case without an electric field.
Calculations of shock-wave flow structure in axisymmetric channel with near-wall ethylene burning with throttle air jet
Authors: Zamuraev V P , Kalinina A P , Fedorova DV , Popova D.S 
Published: November 2019

Abstract
The CFD modelling of the ramjet start with low losses of the stagnation pressure was carried out. The basic feature of this start technology was the jet of compressed air creating effect of a throttle which aids in preliminary decelerating of the flow up to transonic velocities. The comparison with experiment was performed for the hydrogen burning. We studied the axial and near-wall supply of gas fuel. The physical mechanisms stimulating stable presence of transonic mode in the part with constant section were investigated within the frameworks URANS approach. It was shown that fuel supply blockage is a way to control near-wall supplying of gaseous fuel at considerably low pressure falls. And blocking the ignition processes is a way to control the axial supply at quite high pressure falls.
Usefulness of cutting planes in the hierarchical segmentation of cardiac anatomical structures
Authors: Vera M , Valbuena O , Huérfano Y , Vera M I , Gelvez-Almeida E , Salazar-Torres J 
Published: November 2019

Abstract
A spatial geometric plane is defined by the three-dimensional coordinates of a pair of spatial points and the direction that the normal vector establishes, which is formed by joining those points by means of an oriented line segment. This type of planes, in three-dimensional images, is extremely useful as an alternative solution to the problem of low contrast that exhibit the anatomical structures present in cardiac computed tomography images. To do this, after using a predetermined filter bank and in order to define a region of interest, a smart operator based on least squares support vector machines is trained and validated in order to detect the aforementioned coordinates which enables the location of the plane, in the three-dimensional space that contains the considered images. Once the structure that is required to segment is identified, a discriminant function is used that cancels all information not linked to this structure. In this work, the segmentation of the left ventricle, based on region growing technique, is firstly considered and then the left atrium is segmented considering region growing technique and an inverse discriminant function. The results show an excellent correspondence relationship when the spatial union of both structures is made.
Testing GeoGebra as an effective tool to improve the understanding of the concept of limit on engineering students
Authors: Aréchiga Maravillas J C , Díaz S Arceo , Salazar-Torres J , Andrade D A Sierra 
Published: November 2019

Abstract
The impact GeoGebra on the teaching of the concept of limit was analyzed. Two groups of engineering students, studying differential calculus, served as control and test groups. The traditional teaching, based on examples solved by hand, was given to the control group while a series of activities involving the usage of the mathematical software GeoGebra were applied in an attempt of improving the degree of assimilation on the concept of limits.
Conceptions and pedagogical practices on the mathematical processes of teachers
Authors: Hernández C A , Prada R , Gamboa A 
Published: November 2019

AbstractThe objective of this research work is to establish the disciplinary, didactic and pedagogical conceptions of teachers in the area of mathematics in basic education against the formative process by competences and mathematical processes. The relationship between the standards developed in the institution against those stipulated by the “Ministerio de Educación Nacional” of Colombia was analyzed. This research was developed considering a hermeneutical historical paradigm, guided by the integrated qualitative approach, from an ethnographic design and therefore microetnography as a method. The research contributes from the epistemological, pedagogical and didactic categories, towards the achievement of evidence related to the classroom practices of teachers where contextualized problematic situations do not prevail so that the classes of the students are routine, not very impactful and the environment or Space becomes unmanageable, they do not have an adequate use of educational texts, and the use of educational material such as technological tools is not evident.
Errors and difficulties in solving algebraic procedures in secondary school students
Authors: Diaz A , Hernández C A , Paz L S 
Published: November 2019

AbstractThe research presented was aimed at determining the errors and difficulties presented by secondary school students in a Colombian public educational institution when faced with the solution of algebraic procedures. A contribution is sought to contribute to studies that monitor the performance of the teaching and learning processes of students. The methodology was based on the quantitative paradigm with a descriptive design, for which two instruments were applied to detect errors and difficulties in students. The results allowed to detect that, of the 12 errors that were taken as dimensions, six are significantly replicated, the most significant being the simple calculation error, unfinished procedure and the errors when performing arithmetic-algebraic operations. Participants allege associated difficulties, mostly to teaching problems, which generated guidelines aimed at teachers in order to raise didactic situations related to error as a source of learning.