Experimental Thermal and Fluid Science最新文献

{"title":"Condensation flow inside tubes: A review of heat transfer coefficient measurement techniques, experimental databases and prediction methods","authors":"","doi":"10.1016/j.expthermflusci.2024.111298","DOIUrl":"10.1016/j.expthermflusci.2024.111298","url":null,"abstract":"<div><p>Heat transfer coefficient (HTC) is one of the most important parameters for modeling forced flow condensation inside tubes. This manuscript presents an extensive review of HTC measurement techniques, experimental databases, and prediction methods for in-tube flow condensation to evidence the latest literature achievements and identify new research opportunities. HTC measurement techniques were reviewed, classified, and the most used techniques were identified along with their main characteristics. Experimental databases from the literature were grouped for analysis, totaling 15,021 data points for channel diameters ranging from 0.067 to 20.8 mm, 82 working fluids, horizontal and vertical flow directions, and 4 different tube wall materials for smooth tubes. The measurement techniques and uncertainties of individual databases were identified and discussed. Recently identified trends are the increasing interest in low GWP refrigerants, new fluid mixtures, and experiments for small-diameter channels. Many of these experimental conditions were not incorporated or tested on previous correlations, representing an extrapolation when doing so. A total of 34 prediction methods, proposed from 1958 to 2024, were evaluated and compared to this broad database to verify their prediction errors and physical fundamentals. The best predictions obtained a mean absolute percentage error of 23.4 %, showing that further work for minimizing the experimental uncertainties is still needed. In addition, HTC values higher than 10 kW/m²K are commonly observed in recent experiments. One of the challenges identified for new measuring techniques is the measurement of such high values of HTC while keeping low uncertainty levels. The experimental database collected in this work is available for download in the <span><span>supplementary material</span></span>.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142087844","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 investigation on the aerodynamics and flow patterns of a 5:1 rectangular cylinder with spoilers","authors":"","doi":"10.1016/j.expthermflusci.2024.111284","DOIUrl":"10.1016/j.expthermflusci.2024.111284","url":null,"abstract":"<div><p>The current study experimentally investigates a passive control method for the flow field by placing spoilers symmetrically on the leading edge of a 5:1 rectangular cylinder. The Reynolds number (Re) is based on the inflow velocity and the height of the model. The length of the spoiler is equal to the span length of the model, and the width and angle are defined as <em>w</em> and <em>α</em>. At <span><math><mrow><mtext>Re = 1.07 2.50</mtext><mo>×</mo><msup><mrow><mtext>10</mtext></mrow><mtext>4</mtext></msup></mrow></math></span>, the surface pressure distribution of the model is obtained to initially investigate the effects of <em>α</em> and <em>w</em> on the aerodynamic characteristics. Based on the aerodynamic results, some cases are selected to reveal the control mechanism using the particle image velocimetry (PIV) technique. The proper orthogonal decomposition (POD) is adopted to analyze the POD modes and instantaneous flow. The results show that the spoiler with a certain <em>α</em> can suppress the aerodynamic forces of the model. Spoilers with a relative angle of 247.5° significantly reduce <span><math><mrow><msubsup><mtext>C</mtext><mrow><mtext>L</mtext></mrow><mo>′</mo></msubsup></mrow></math></span> by 75 % and slightly reduce <span><math><mrow><mover><mrow><msub><mtext>C</mtext><mtext>D</mtext></msub></mrow><mrow><mo>¯</mo></mrow></mover></mrow></math></span> by 5.5 %. Also, its TKE and RSS values are reduced by 56 % and 57 %, respectively. The PIV visualization shows that the spoiler affects the flow separation at the leading edge. Then, the rolling and interactions of shear layers are suppressed, making them tend to be parallel. Besides, spoilers with a relative angle of 67.5° almost eliminate the flow separation.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142084191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laminar flow and convective heat transfer of ferrofluid in a tube under oscillating magnetic fields: Effect of magnetic phase shift","authors":"","doi":"10.1016/j.expthermflusci.2024.111293","DOIUrl":"10.1016/j.expthermflusci.2024.111293","url":null,"abstract":"<div><p>In this study, laminar flow and forced convective heat transfer of water-based ferrofluids flowing through a uniformly heated pipe are experimentally investigated under the presence of phase-shifted oscillating magnetic fields. To investigate the effect of phase shift on heat transfer, electromagnets are positioned along the tube, and oscillating magnetic fields are applied with various phase shift angles between opposing magnetic poles. Experiments are conducted for different Reynolds numbers (400 to 1000), magnetic field frequencies (0 Hz, 1 Hz, and 5 Hz), phase shift angles (0°, 90°, and 180°), and nanoparticle volume fractions (0.5 % and 1 %). For each parameter set, local and average Nusselt numbers, as well as pressure drop values, are determined, and the effect of applied magnetic fields on the heat transfer rate is extensively discussed. Results showed that, applying an external magnetic field resulted in significant enhancements in the forced convective heat transfer of ferrofluid. Under an oscillating magnetic field with 0° phase shift, maximum of 40 % and 20.6 % enhancements were observed in local and average Nusselt numbers respectively under the investigated parameters. Furthermore, applying oscillating magnetic fields with a phase shift between opposing poles caused significant fluctuations in the fluid, led to remarkable improvements in convective heat transfer rates. For 90° and 180° phase shifts, enhancements in local and average Nusselt numbers were observed to increase up to 73 % and 36 %, respectively.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142002015","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sub-regimes of horizontal gas–liquid intermittent flow: State-of-the-art and future challenges","authors":"","doi":"10.1016/j.expthermflusci.2024.111281","DOIUrl":"10.1016/j.expthermflusci.2024.111281","url":null,"abstract":"<div><p>Based on the shape of the interface elongated bubble/liquid slugs and the liquid slugs’ aeration, the horizontal intermittent flow can be divided into three sub-regimes including plug (PG), Less Aerated Slug (LAS) and Highly Aerated Slug (HAS) flows. These flow sub-regimes were observed from experiments performed using air–water mixture and small pipe diameters. This paper presents an analysis of the results obtained with the aim of constituting the state-of-the-art of this sub-regimes classification.</p><p>The critical review, of the current state of knowledge, has led to the conclusion that the subdivision of intermittent flow into sub-regimes may provide a better means of apprehending, understanding and advancing in the modelling of slug parameters, Interfacial Area Concentration, Pipeline Integrity Management, intermittent flow behavior across singularities, as well as for the development of more realistic mechanistic models. The acquired knowledge can be beneficial for petroleum and gas, nuclear and chemical engineering industries among others.</p><p>Finally, based on the presented state-of-the art, some recommendations are given for future works using this approach. These reflection paths will allow improving our comprehension on intermittent flow, promoting the development of more robust models.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142097798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aerodynamic performances and near wake of an Ahmed body under unsteady flow conditions","authors":"","doi":"10.1016/j.expthermflusci.2024.111285","DOIUrl":"10.1016/j.expthermflusci.2024.111285","url":null,"abstract":"<div><p>This paper experimentally characterizes unsteady effects and flow fields around the Ahmed Body, by analyzing global forces and detailed wake effects. The results are compared to those obtained under steady conditions, with varying wind tunnel velocities and different yaw angles between the model and the free stream. Unsteady fields are generated by means of oscillating blades positioned at the inlet of the test section, whose amplitudes and frequencies can be easily controlled. Specifically, low frequencies, around a few Hertz, as those in the typical range generating load oscillations on vehicles, are considered. The results in terms of force coefficients, obtained by a dynamometric balance, and velocity fields, obtained by Particle Image Velocimetry, are processed in order to derive time-average statistics and also phase-average statistics, as related to forcing blade instantaneous positioning. This type of analysis can be performed thanks to the high temporal resolution of measurement systems, around 100 Hz for the force measurements and around 4000 Hz for the velocity measurements. Results in steady conditions well compare with previous results in references, both as functions of wind tunnel velocity and yaw angles. In unsteady conditions, whatever amplitude is considered, time-average drag and lift coefficients and their dependence on yaw angle are consistently lower compared to the steady case. Phase-averaged coefficients in unsteady conditions can oscillate by around 20 % in comparison to time-average values and these fluctuations are strongly dependent on yaw angle and amplitude of oscillations, thus suggesting that they both contribute to instantaneous loads. Present investigations are related to improvements in set-up of control systems in assisted-driving (self-driving) vehicles.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001547/pdfft?md5=46d44469ddd351e42049d159f1f4b056&pid=1-s2.0-S0894177724001547-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142097684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Collision adhesion law of oil Droplets-Bubbles with different particle sizes in free floating","authors":"","doi":"10.1016/j.expthermflusci.2024.111292","DOIUrl":"10.1016/j.expthermflusci.2024.111292","url":null,"abstract":"<div><p>The treatment of oily wastewater has become a serious problem in the late stage of oilfield development. At the same time, it is of great significance to the improvement of ecological environment. As the key process of oil-bearing wastewater treatment, the study on the binding and adhesion law of oil droplets and bubbles in flotation and its related mechanism can provide reference for its application. Using a double high-speed camera acquisition system, the floating process and collision adhesion law of oil droplets and bubbles in a vertical transparent circular tube were experimentally studied, and the collision adhesion process of oil droplets (0.721 ∼ 3.759 mm) and bubbles (0.797 ∼ 2.886 mm) in different diameters were analysed. It is concluded that the oil droplet and the bubble collide with each other, and then the bubble slides along the surface of the oil droplet, and a neck shape appears at the end of the contact site, and then the neck increases with the diffusion of the oil droplet to form an oil-bubble adhesion body. And the process of elastic drags and contraction separation of the mixture is also demonstrated. It is found that the combination of oil droplets and bubbles with different diameters will have two types of collision adhesion modes, which oil droplet type and oil film type, respectively. Therefore, the diameter ratio of oil droplets and bubbles is a key factor, and when the diameter ratio is greater than 0.75, the adhesion mode of the adhesive body changes from unstable oil droplet type to more stable oil film type.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142012925","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Flow mixing enhancement by crossflow induced oscillations of an open semicircular cylinder","authors":"","doi":"10.1016/j.expthermflusci.2024.111283","DOIUrl":"10.1016/j.expthermflusci.2024.111283","url":null,"abstract":"<div><p>Flow-induced vibrations of a rigid prism with an open semicircular cross section, supported elastically, were experimentally studied in a free-surface water channel. The objective of the study was to explore the prism’s potential to promote flow mixing in its wake and simultaneously harvest mechanical energy from the incoming flow. The mechanical dimensionless parameters, namely the mass ratio and damping, were kept constant, focusing primarily on the influence of flow speed (or reduced velocity <span><math><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span>) on mixing efficiency and energy extraction. The following findings were obtained: (i) a clear correlation exists between the efficiency of mixing and the efficiency of energy extraction, (ii) mixing efficiency is higher in the near wake and gradually decreases downstream, and (iii) mixing efficiency scales with <span><math><mrow><msup><mrow><mi>A</mi></mrow><mrow><mo>∗</mo></mrow></msup><msup><mrow><mrow><mo>(</mo><msup><mrow><mi>f</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>/</mo><msup><mrow><mi>U</mi></mrow><mrow><mo>∗</mo></mrow></msup><mo>)</mo></mrow></mrow><mrow><mn>2</mn></mrow></msup></mrow></math></span>, where <span><math><msup><mrow><mi>A</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> and <span><math><msup><mrow><mi>f</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> represent the dimensionless amplitude and frequency of the prism’s oscillation, respectively. This indicates that flow mixing is directly influenced by the transverse acceleration of the prism and the unperturbed flow speed. Then, maximum mixing efficiency is expected to be achieved when high oscillation amplitudes occur at low reduced velocities which suggest that synchronization of vortex shedding contributes to enhance flow mixing.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001523/pdfft?md5=08e879d9883d2f0ce8bace97236370cd&pid=1-s2.0-S0894177724001523-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141978378","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Data-informed characterization of spatio-temporal scales in experiments of microconfined high-pressure transcritical turbulence","authors":"","doi":"10.1016/j.expthermflusci.2024.111282","DOIUrl":"10.1016/j.expthermflusci.2024.111282","url":null,"abstract":"<div><p>The spatio-temporal scales of microconfined high-pressure transcritical turbulence are characterized in relation to the resolution capabilities of present time-resolved two-dimensional <span><math><mi>μ</mi></math></span>PIV technology. Utilizing <span><math><msub><mrow><mi>CO</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> as the working fluid, the physical scales are examined by considering the main dimensionless groups of the problem, which correspond to the Reynolds, Brinkman, and Stokes numbers and the mass fraction of particles in the fluid. In detail, the methodology employed leverages direct numerical simulation data to inform the estimation of hydrodynamic, thermophysical, and particle-related scales, and selects a state-of-the-art <span><math><mi>μ</mi></math></span>PIV setup to describe the optical performance of the current technology. The results indicate that the temporal scales can be experimentally captured for a wide range of operating conditions. However, the scenario becomes much more complex when trying to capture the spatial scales of microconfined high-pressure transcritical turbulent flow. Particularly, the Kolmogorov and Batchelor spatial scales can be captured for bulk Reynolds numbers below <span><math><mrow><mi>O</mi><mrow><mo>(</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>3</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span>. Otherwise, the spatial scales can only be partially captured and/or remain completely masked due to insufficient resolution, like for example in the case of boundary layer viscous scales and fluid density variations. This limitation is not imposed by the tracer behavior of microparticles, as the Stokes number remains significantly low for all the system configurations studied. Instead, the limitation is mainly a result of the optical capabilities of present <span><math><mi>μ</mi></math></span>PIV systems. Finally, given the generalizable properties of dimensionless numbers, the results and insight obtained can be extended to other experiments of <span><math><mi>μ</mi></math></span>PIV-based visualization/quantification of microconfined multiscale flows involving large thermophysical variations.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001511/pdfft?md5=d7ae0722a7382e6146445b2b69e932d4&pid=1-s2.0-S0894177724001511-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141963888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrigendum to “Effect of liquid preheating on high-velocity airblast atomization: From water to crude rapeseed oil” [Exp. Therm. Fluid Sci. 102 (2019) 137–151]","authors":"","doi":"10.1016/j.expthermflusci.2024.111275","DOIUrl":"10.1016/j.expthermflusci.2024.111275","url":null,"abstract":"","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001444/pdfft?md5=3b918ced54568229be18d50b11e2e8d4&pid=1-s2.0-S0894177724001444-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142168239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental evaluation of the flow field induced by an active vortex generator","authors":"","doi":"10.1016/j.expthermflusci.2024.111280","DOIUrl":"10.1016/j.expthermflusci.2024.111280","url":null,"abstract":"<div><p>This investigation examined the flow field generated by a ramp-shaped vortex generator (VG) that underwent active oscillation within a laminar boundary layer. The oscillations were applied through a servomotor, which pivoted the VG around its leading edge. The study evaluated the influence of varying the maximum VG height during the oscillations (<em>h</em>), actuation frequency (<em>f</em>), and the waveform governing the periodic oscillation of the VG. Planar particle image velocimetry (PIV) measurements were conducted to estimate flow mixing and the drag induced by the VG. The height-based Reynolds number (<em>Re</em>_h) ranged from 300 to 600, and the chord-based Strouhal number (<em>St</em>_c) for the oscillations varied from 0.67 to 3.33. The findings of the study indicate that active VGs lead to a greater wall-normal transport of streamwise momentum and result in lower drag compared to static VGs. Furthermore, increasing <em>h</em> results in larger momentum transport and drag of the active VGs. The investigation also revealed that the highest momentum transport and drag occurred when <em>f</em> was close to the instability frequency of the shear layer. The results show the potential of active VGs for separation control under various flow conditions.</p></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":null,"pages":null},"PeriodicalIF":2.8,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0894177724001493/pdfft?md5=691b324f0c38c36f39003b7e1af296fb&pid=1-s2.0-S0894177724001493-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142002016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}