Journal of Engineering Thermophysics最新文献

{"title":"HFE-7100 Droplet Interaction with a Superheated Surface","authors":"V. O. Sitnikov,&nbsp;E. Ya. Gatapova","doi":"10.1134/S1810232825010072","DOIUrl":"10.1134/S1810232825010072","url":null,"abstract":"<p>The dynamics of HFE-7100 droplet interactions with a heated sapphire surface at superheat from 10 to 100°C for Weber numbers from 25 to 345 are considered. Top- and side-view visualizations are performed using a high-speed camera supplemented by a stereomicroscope. Top view images allow us to follow the transitions to different boiling regimes, as well as to observe bubble formation, bubble density, bubble clusters, bubble absence, and the transparency of the spreading droplet during levitation. While side view images show the rebound and levitation heights and angles. The rebound, the formation of a vapor layer, and the conditions under which the droplet levitates as the substrate temperature rises are studied. The formation of finger-like structures, which can then form secondary droplets, is observed for high We number values.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"74 - 83"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Study of Flame Combustion of Pulverized Coal Fuel in a Two-Stage Vortex Burner","authors":"E. Yu. Gorelikov,&nbsp;I. V. Litvinov,&nbsp;E. B. Butakov,&nbsp;S. I. Shtork","doi":"10.1134/S1810232825010084","DOIUrl":"10.1134/S1810232825010084","url":null,"abstract":"<p>The paper presents a study of the aerodynamics of flame combustion of coal fuel in a burner device with thermal power of 50 kW. The burner device was a two-stage tangential swirler. In the first stage, air was supplied tangentially with axial pilot supply of propane. In the second stage, the pulverized coal mixture with heated secondary air was supplied. During the experiments, the efficiency of coal fuel combustion was studied with co-swirl and counter-swirl of the second stage relatively to the first one. The temperature was measured on the wall and in the center along the muffle swirl chamber. The gas composition of the combustion products was measured at the outlet of the swirl chamber. The profiles of the mean axial and tangential velocity along the length of the swirl chamber were measured with the two-component laser Doppler anemometer (LDA) system. Particles of unburned coal fuel served as signal tracers. The obtained results have led to a conclusion about the efficiency of the system for pulverized coal fuel combustion in the counter-swirl mode for enhancement of mixing and combustion.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"84 - 92"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Graphene Nanotubes on Thermal Conductivity of a Phase Change Material","authors":"M. I. Nizovtsev,&nbsp;V. N. Letushko,&nbsp;A. N. Sterlyagov","doi":"10.1134/S1810232825010114","DOIUrl":"10.1134/S1810232825010114","url":null,"abstract":"<p>The paper presents experimental results on the use of graphene nanotubes aimed at an increase in thermal conductivity of a phase change material. Graphene nanotubes were dispersed in molten paraffin by ultrasonic treatment in an amount of 0.1–0.5 wt. %. The obtained samples of paraffin with graphene nanotubes were examined using a scanning calorimeter. During heating and cooling, the DSC curves of all samples with different content of nanotubes demonstrated two peaks corresponding to phase transitions of the main hydrocarbons in paraffin composition. The presence of nanotubes in paraffin did not significantly affect the shape of the DSC curves. Experiments with sample heating in a thermostat in terms of a time delay in changing the temperature of samples indicated an increase in thermal conductivity of solid paraffin with addition of graphene nanotubes and its decrease, when graphene nanotubes were added to liquid paraffin. These effects increased with increasing mass content of nanotubes. The method of steady-state heat flux was used to determine the coefficient of thermal conductivity of samples of a phase change material with nanotubes. According to the measurement results, the maximum increase in the thermal conductivity of paraffin in the solid state was 22% at a nanotube concentration of 0.5 wt. %. The thermal conductivity coefficients of various materials with “contrasting” inclusions were compared according to the results of calculations and experiments.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"121 - 132"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Impact of Impingement Surface Angle Variation and Channel Design on Heat Transfer Performance and Flow Characteristics for Twin Jet Impingement","authors":"K. Karabulut,&nbsp;Y. Alnak","doi":"10.1134/S181023282501014X","DOIUrl":"10.1134/S181023282501014X","url":null,"abstract":"<p>This study intends to give a detailed research of surface angles of impingement, and jet-plate distances to enhance heat transfer and improve the channel’s flow structure features for twin jet impingement. For this aim, numerical analysis of twin jet impingement was carried out for distinct impingement surface angles (<span>(alpha)</span>) of 30°, 45°, and 60° and impinging jet-plate distances (H) of 3, 4.5, and 6. The numerical investigation was performed as a steady, two-dimensional, employing the <span>(k)</span>-<span>(varepsilon)</span> turbulence model and the Ansys–Fluent program in the twin jet rectangular channel. While the isothermal flat plate impingement surface has 310 K (T<span>(_{{rm H}})</span>), the impinging air jet fluid temperature is 300 K (T). The obtained outcomes were compared with the numerical and experimental outcomes of the work in the literature and it was noticed that they are determined to be compatible. The results were presented as the local Nu number (Nu<span>(_{L})</span>) variations for <span>(alpha=30^{circ})</span>, 45° and 60° impingement surface angles along the flat plate impingement surface, and the variations of mean Nu numbers (Nu<span>(_{m})</span>) for different <span>(alpha)</span> and H values with the Re number ranges of 20000–50000. Besides, streamlines and temperature isotherms were evaluated for different <span>(alpha)</span>, H and Re number values by visualising them in detail. The results displayed that while the Nu<span>(_{m})</span> values are higher than the case without angle (<span>(alpha=0^{circ})</span>) for all angles and H values, after the 30° angle, the Nu<span>(_{m})</span> values decrease slightly at 45° and 60°. Accordingly, for H = 6, the Nu<span>(_{m})</span> value of 30° impingement surface angle is 3.09% higher than that in 60°.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"162 - 179"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correcting Spectral Density of Laser Doppler Anemometer Signals during Measuring of High-Speed Aerodynamic Flows. Part 2","authors":"I. K. Kabardin,&nbsp;V. V. Rakhmanov,&nbsp;A. V. Klimov,&nbsp;V. G. Glavnyi,&nbsp;D. V. Kulikov,&nbsp;V. G. Meledin,&nbsp;S. V. Dvoinishnikov,&nbsp;V. O. Zuev,&nbsp;G. V. Bakakin,&nbsp;V. A. Pavlov","doi":"10.1134/S1810232825010035","DOIUrl":"10.1134/S1810232825010035","url":null,"abstract":"<p>A method has been developed for constructing correction factors to compensate for distortions introduced by non-uniform frequency characteristics of the electronic path of a laser Doppler velocimeter into the spectral density of Doppler signals. The method relies on averaging a statistical ensemble of spectral densities of noise signals obtained during illumination of a photodetector with a reference white light source, constructing the inverse function to the resulting averaged spectral density with truncation in the low- and high-frequency bands, and applying digital low-pass filtering to it. In the first part, a model numerical experiment was carried out. The gas flow velocity at the Vitoshinsky nozzle exit was measured with a laser Doppler anemometer in high-velocity modes. It has been shown that in high-velocity modes (200 m/s), the application of correction factors to the spectral density of Doppler signals allows estimating the average flow velocity with an error of no more than 5%, while calculating velocities without preliminary correction of the spectral density leads to statistical measurement errors of more than 100%.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"25 - 34"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848964","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental Observations of Meridional Flow Stagnation in a Three-Fluid Vortex","authors":"M. V. Tintulova,&nbsp;I. V. Naumov,&nbsp;B. R. Sharifullin,&nbsp;V. N. Shtern","doi":"10.1134/S1810232825010059","DOIUrl":"10.1134/S1810232825010059","url":null,"abstract":"<p>In the search for a flow pattern optimal for culture growth in vortex bioreactors, our experiments discovered unusual flow structures that existing theoretical models cannot explain. Three immiscible liquids fill a vertical open cylindrical container of radius R = 47 mm whose sidewall is still while the bottom disk rotates driving a fluid motion. The centrifugal force pushes the lower liquid (L, aqueous glycerol) from the axis to the periphery near the bottom, creating its toroid circulation that in turn drives toroid circulations of the middle liquid (M, sunflower oil) and the upper liquid (U, alcoholic glycerine). With increasing rotation, counterflows develop near interfaces LM and MU: the liquids move towards (away from) the axis below (above) the interface that seems paradoxical. At a small thickness of M, a stagnation zone arises where the axial and radial velocities vanish and the M liquid only rotates. As M thickness decreases, this stagnation zone expands and occupies the entire volume of the middle liquid. These counterintuitive results await their theoretical explanation and formulation of new contact conditions at the LM and MU interfaces.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"54 - 61"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Using LED Interferometry Technique to Study Pressure Reduction Effect on Microlayer Thickness during Pool Boiling","authors":"V. Serdyukov,&nbsp;I. Kosovskikh,&nbsp;I. Malakhov","doi":"10.1134/S1810232825010011","DOIUrl":"10.1134/S1810232825010011","url":null,"abstract":"","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"1 - 11"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848962","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of Light Gas Injection on the Weakly Accelerated Xenon Flow","authors":"A. Yu. Sakhnov,&nbsp;V. S. Naumkin","doi":"10.1134/S1810232825010102","DOIUrl":"10.1134/S1810232825010102","url":null,"abstract":"<p>The paper presents a numerical modeling of boundary layer equations supplemented with the <span>(k)</span>-<span>(omega)</span>-<span>(gamma)</span> turbulence model, that describe an accelerated xenon flow at the helium injection through the wall. Authors set values of the acceleration parameter <span>(K)</span> of <span>(4cdot10^{-7})</span> and the injection parameter <span>(overline{j_{w}})</span> in the range from <span>(10^{-4})</span> to <span>(10^{-3})</span>. The problem was solved by the finite difference approach with the implicit scheme. The study showed that the helium as a light gas injection into the accelerated xenon flow may results to the occurrence of the local flow laminarization near the wall together with turbulent flow in the outer part of the boundary layer. It was shown that the increase of the injected gas temperature leads to the increase of the skin-friction in two times under considered conditions. At that, the thermal and mass Stanton numbers increase by no more than 20% relatively the flow with the quasi-isothermal light gas injection.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"107 - 120"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correcting Spectral Density of Laser Doppler Anemometer Signals during Measuring of High-Speed Aerodynamic Flows. Part 1","authors":"V. V. Rakhmanov,&nbsp;I. K. Kabardin,&nbsp;A. V. Klimov,&nbsp;V. G. Glavny,&nbsp;D. V. Kulikov,&nbsp;V. G. Meledin,&nbsp;S. V. Dvoynishnikov,&nbsp;V. O. Zuev,&nbsp;G. V. Bakakin,&nbsp;V. A. Pavlov","doi":"10.1134/S1810232825010023","DOIUrl":"10.1134/S1810232825010023","url":null,"abstract":"<p>The first part of the work sets out the problem for a method of constructing correction coefficients to compensate for distortions introduced by the non-uniform frequency characteristics of the electronic path of a laser Doppler velocimeter into the spectral density of Doppler signals. The method relies on averaging a statistical ensemble of the spectral densities of noise signals obtained during illumination of a photodetector by a white light source, constructing the inverse function to the averaged spectral density acquired with truncation in the low- and high- frequency bands, and applying digital low-pass filtering to it. A model numerical experiment has been carried out. The results of the experiment are presented, and they confirm increase in the velocity measurement error as the flow rate grows.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"12 - 24"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat Transfer Increase Research According to Using Different Combined Jet Flow Channel Design and Nanofluids","authors":"Y. Alnak","doi":"10.1134/S1810232825010151","DOIUrl":"10.1134/S1810232825010151","url":null,"abstract":"<p>This study focused on the numerical investigation of heat transfer from various shaped copper plate surfaces exposed to a constant heat flux of 1000 W/m². The analysis employed a combination of cross-flow and impinging jet flows. The numerical simulations were carried out by solving the energy and Navier–Stokes equations using the Ansys–Fluent computer program with the <span>(k)</span>-<span>(varepsilon)</span> turbulence model. To guide the combined jet flow towards the heated surfaces in the channel, horizontal fins with 30° and 60° angles were placed in the channel. The channel height (<span>(H)</span>) was set at 4 times the diameter (<span>(D)</span>), and the fin distance from the jet inlet (<span>(N)</span>) was equal to <span>(D)</span>. Different fin lengths of <span>(D)</span>, <span>(1.166D)</span>, and <span>(1.333D)</span> (K) were utilized in the channels. The study considered three types of fluids: water, 2% CuO-Water, and 0.02% GO-Water nanofluids. The upper and lower surfaces of the channel and the fin were assumed to be adiabatic, and the Reynolds number of the flow ranged from 5000 to 15000. The results of this work were compared with experimental studies from the literature, and good agreement was found between them. Unlike previous studies, this research explored the effects of fin lengths and fin angles on heat transfer from differently shaped surfaces and the flow structures created by the fins in the channels, using GO-Water and CuO-Water nanofluids. The results were presented in terms of the mean Nusselt number variations for each model surface. Additionally, velocity and temperature contour distributions of the combined jet flow along the channel for CuO-Water nanofluid were analyzed. Performance Evaluation Coefficient (PEC) values, along with average Nusselt number (Nu<span>(_{m}))</span> and surface temperature (<span>(T_{m}))</span> values, were assessed at different Reynolds numbers for all three patterned surfaces in the channels. At Re = 5000 and <span>(K=D)</span>, there were significant increases in Nu<span>(_{m})</span> values for cube, roofed, and square hollow model surfaces when using a 60° fin and GO-Water nanofluid compared to channels with water flow and no fins.</p>","PeriodicalId":627,"journal":{"name":"Journal of Engineering Thermophysics","volume":"34 1","pages":"180 - 207"},"PeriodicalIF":1.3,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143848926","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}