Experimental Thermal and Fluid Science最新文献

Asymmetric breakup of double emulsion droplets in symmetric junctions 双乳液滴在对称结中的不对称破裂

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-13 DOI: 10.1016/j.expthermflusci.2025.111542

Xiang Wang, Zhaomiao Liu, Yan Pang

{"title":"Asymmetric breakup of double emulsion droplets in symmetric junctions","authors":"Xiang Wang, Zhaomiao Liu, Yan Pang","doi":"10.1016/j.expthermflusci.2025.111542","DOIUrl":"10.1016/j.expthermflusci.2025.111542","url":null,"abstract":"<div><div>The transportation behaviors of double emulsion droplets in symmetric microfluidic junctions are investigated experimentally, with much attention paid to the particular behavior of the asymmetric breakup. The dynamic processes of interface evolution in typical flow patterns are captured. In contrast to previous studies, the dynamic analysis is carried out with different combinations of the inner and outer droplet lengths, based on which new flow pattern maps are built. The evolutions of the interfacial parameters including the extension length, minimum neck width, gap width, deformation factor, and profile asymmetry are given thorough discussions to reveal the transition rules between neighboring flow patterns. Based on the typical feature of the breakup process, geometric expressions of the maximum extension length is proposed to quantify the critical threshold of droplet breakup, which also helps explain the different influences of the varied bifurcation junctions. Two thread pinch-off regimes in the final stage are identified and the different characteristics in terms of the thread position and satellite droplet size are discussed. The fixed pinch-off position is confirmed to be the reason why droplets are more easily broken in the Y-junction, which also results in the nearly unchanged small asymmetry. For the T-junction, the lateral bias of the neck thread is found to reversely rely on the shift of the inner core owing to the influence between interfaces and the profile asymmetry increases with the length ratio of the inner to outer droplet length.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111542"},"PeriodicalIF":2.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288812","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}

引用次数: 0

Natural convection experiments around an upper dome varying Rayleigh number and truncation angle 不同瑞利数和截断角的顶盖自然对流实验

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-13 DOI: 10.1016/j.expthermflusci.2025.111548

Su-Yeon Park, Dong-Hyuk Park, Bum-Jin Chung

{"title":"Natural convection experiments around an upper dome varying Rayleigh number and truncation angle","authors":"Su-Yeon Park, Dong-Hyuk Park, Bum-Jin Chung","doi":"10.1016/j.expthermflusci.2025.111548","DOIUrl":"10.1016/j.expthermflusci.2025.111548","url":null,"abstract":"<div><div>We carried out natural convection heat transfer experiments around upper domes varying truncation angles (<em>θ</em> = 90°, 70°, 50°, and 30°) over a wide range of Rayleigh number (<em>Ra<sub>Db</sub></em> = <em>gβ</em>Δ<em>TD<sub>b</sub></em><sup>3</sup>/<em>αν</em>, 2.63 × 10<sup>9</sup> ≤ <em>Ra<sub>Db</sub></em> ≤ 1.08 × 10<sup>13</sup>). The shape of a dome is close to the hemisphere as <em>θ</em> is 90° and to flat plate as <em>θ</em> is 0°. To achieve high <em>Ra<sub>Db</sub></em> condition, mass transfer experiments using H<sub>2</sub>SO<sub>4</sub>–CuSO<sub>4</sub> copper electroplating system were employed. Mass transfer rates were measured by electric current, and flows were observed by the Particle Image Velocimetry (PIV). The measured average Nusselt number (<em>Nu<sub>Db</sub></em> = <em>h<sub>m</sub>D<sub>b</sub></em>/<em>k</em>) increased as <em>Ra<sub>Db</sub></em> increased and as the <em>θ</em> decreased. The enhancement was more significant at lower <em>Ra<sub>Db</sub></em> values, which is attributed to variations in the location of flow transition to turbulence and separation. At a relatively low <em>Ra<sub>Db</sub></em> (1.08 × 10<sup>10</sup>), flow remains attached but undergoes an early transition to turbulence when the <em>θ</em> is small. Meanwhile, when the <em>θ</em> becomes large, flow separation occurs without prior transition. As <em>Ra<sub>Db</sub></em> increases, however, flow separation occurs irrespective of the <em>θ</em>. <em>Nu<sub>Db</sub></em> of dome with <em>θ</em> = 30° had 35 % higher than the dome with <em>θ</em> = 90° at <em>Ra<sub>Db</sub> =</em> 1.08 × 10<sup>10</sup> until 18 % higher at <em>Ra<sub>Db</sub> =</em> 1.08 × 10<sup>13</sup>. The <em>Nu<sub>Db</sub></em> correlation for an upper dome was developed. This work contributes not only to a deeper phenomenological understanding of natural convection heat transfer around upper domes but to the application to passive cooling of SMR outer containments.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111548"},"PeriodicalIF":2.8,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288761","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}

引用次数: 0

First experimental investigation of high pressure methanol cavitating flow characteristics in quasi two-dimensional nozzles 准二维喷嘴高压甲醇空化流动特性的首次实验研究

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-12 DOI: 10.1016/j.expthermflusci.2025.111547

Yizhou Yang , Zhixia He , Lian Duan , Wei Huang , Zhen Yang , Ao Kang , Genmiao Guo , Wei Guan

{"title":"First experimental investigation of high pressure methanol cavitating flow characteristics in quasi two-dimensional nozzles","authors":"Yizhou Yang , Zhixia He , Lian Duan , Wei Huang , Zhen Yang , Ao Kang , Genmiao Guo , Wei Guan","doi":"10.1016/j.expthermflusci.2025.111547","DOIUrl":"10.1016/j.expthermflusci.2025.111547","url":null,"abstract":"<div><div>The global shift toward low-carbon solutions is driving the transition from fossil fuels to carbon-neutral fuels in engine applications. Methanol is gaining attention as a promising alternative due to its clean combustion and potential for reducing greenhouse gas emissions. High-pressure direct injection of methanol can reduce emissions and improve fuel efficiency, making it a viable solution for sustainable energy. However, the flow characteristics of methanol in injector nozzles are not well understood due to its unique physical properties compared to diesel and gasoline. The lack of experimental data limits precise control of injection rates and spray patterns. This study presents the first experimental analysis of high-pressure methanol flow in a quasi two-dimensional optical nozzle. An experimental platform was developed to control injection pressures from 1 to 10 MPa and back pressures from 0.1 to 4 MPa with ±1 % accuracy. Flow characteristics are studied under various pressures and temperatures, providing high-precision data for model validation. Comparative experiments were conducted to analyze the flow characteristics of methanol and diesel, providing insights for replacing diesel with methanol in engines. Results show that methanol has a higher discharge coefficient than diesel at higher cavitation numbers due to its lower viscosity, but a lower discharge coefficient at lower cavitation numbers due to stronger cavitation. Finally, a rounded-corner nozzle is introduced to reduce cavitation at the orifice entrance, confirming the role of back suction of the cavitation region in the exit shear layer in promoting the growth of the cavitation region inside the orifice.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111547"},"PeriodicalIF":2.8,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144312476","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}

引用次数: 0

Blue emission in premixed hydrogen flames 预混氢火焰中的蓝色辐射

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-11 DOI: 10.1016/j.expthermflusci.2025.111545

Seunghyun Jo

{"title":"Blue emission in premixed hydrogen flames","authors":"Seunghyun Jo","doi":"10.1016/j.expthermflusci.2025.111545","DOIUrl":"10.1016/j.expthermflusci.2025.111545","url":null,"abstract":"<div><div>The origin of the blue emission in premixed hydrogen flames has been studied. Experiments examining the blue flame were performed using premixed hydrogen/air mixtures in an axisymmetric burner at a jet velocity of 12 m/s and varied equivalence ratios. Nitrogen was used to prevent the influence of a diffusion flame between the ambient air and the hydrogen flame. A spectrometer with a CCD camera measured emission spectra between 385 and 495 nm to identify species that affect the blue emission. Reaction rates, mole and mass fractions were calculated using Chemkin with the GRI 3.0 mechanisms. The blue flame is identified in visible pictures by its distinct emissions, which can be categorized into dark blue and light blue. Clear peaks have been identified in the wavelength range of 385–495 nm. The most pronounced peaks occur between 385 and 420 nm under fuel-lean and stoichiometric combustion conditions, while the peaks between 420 and 495 nm exhibit lower intensities. Emission intensities associated with hydroxyl radicals (OH) and atomic oxygen (O) demonstrate a strong correlation with the reaction rates of chemical reactions and their mole and mass fractions. Emission intensities linked to molecular hydrogen (H<sub>2</sub>) and molecular oxygen (O<sub>2</sub>) reveal a pronounced correlation with the reaction rates. Conversely, emissions related to atomic hydrogen (H) do not reveal a consistent relationship with their mole and mass fractions. The blue emission observed is likely influenced by a combination of OH, H<sub>2</sub>, O<sub>2</sub>, and O. The distinguishable peaks between 390 and 420 nm appear to result from the combined contributions of these species. The comparatively low peaks in the range of 440–495 nm are primarily associated with H<sub>2</sub>. It is important to recognize that the blue emission in hydrogen flames could be affected by OH, H<sub>2</sub>, O<sub>2</sub>, and O.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111545"},"PeriodicalIF":2.8,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297701","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}

引用次数: 0

An analysis of the air intake process impacts on powdered fuel compression characteristics 进气过程对粉末燃料压缩特性的影响分析

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-09 DOI: 10.1016/j.expthermflusci.2025.111544

Jiangang Yang , Chunbo Hu , Yijun Cao , Wei Gao , Xiangwen Zhang , Kai Ma

{"title":"An analysis of the air intake process impacts on powdered fuel compression characteristics","authors":"Jiangang Yang , Chunbo Hu , Yijun Cao , Wei Gao , Xiangwen Zhang , Kai Ma","doi":"10.1016/j.expthermflusci.2025.111544","DOIUrl":"10.1016/j.expthermflusci.2025.111544","url":null,"abstract":"<div><div>To clarify the influence of the tank intake process on the filling characteristics of powdered fuel in a powder ramjet, a method combining powder pneumatic compression experiments and theoretical analysis is employed to study the impact of intake flow rate, powdered fuel stacking height, and flow regulation process on the powdered fuel volume compression ratio (VCR). Based on the Ergun equation and the modified Kawakita equation, a calculation method for the VCR of powdered fuel during the intake process is proposed. The results indicate that the pressure drop between the upper and lower layers of powdered fuel during the intake process is the key factor leading to the volume compression of powdered fuel. Moreover, the VCR of powdered fuel is positively correlated with the intake flow rate and stacking height. The time when the powdered fuel reaches the maximum volume compression ratio (MVCR) is the same as the time when the change rate of gas pressure in the tank stabilizes. The MVCR of powdered fuel in the intake process is 20 %–45 % greater than that in the piston axial compression process. During the flow regulation process, the MVCR of powdered fuel is only related to the maximum intake flow rate and is independent of the regulation process.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111544"},"PeriodicalIF":2.8,"publicationDate":"2025-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144262553","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}

引用次数: 0

Characterization of flame dynamics in a single-element lean direct injection combustion system 单元件精益直喷燃烧系统火焰动力学特性研究

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-06 DOI: 10.1016/j.expthermflusci.2025.111541

Mohamad M. Ghulam, Kranthi Yellugari, Shyam S. Muralidharan, Yuvi Nanda, Ephraim J. Gutmark

{"title":"Characterization of flame dynamics in a single-element lean direct injection combustion system","authors":"Mohamad M. Ghulam, Kranthi Yellugari, Shyam S. Muralidharan, Yuvi Nanda, Ephraim J. Gutmark","doi":"10.1016/j.expthermflusci.2025.111541","DOIUrl":"10.1016/j.expthermflusci.2025.111541","url":null,"abstract":"<div><div>This study explores how the equivalence ratio, inlet air temperature, confinement ratio, and exit boundary influence flame dynamics in a single-element, low-emission nozzle used in a lean direct injection combustion system. Using high-speed OH* chemiluminescence and sound pressure measurements, the research identifies three flame types—V-flame, M−flame, and lifted-distributed flame—with distinct behaviors. At higher equivalence ratios, the V-flame type shows axial fluctuation modes, in-phase coupling with the acoustic field, and higher sound intensity. This is highlighted by the near match in frequency between flame mode (830 Hz) and sound pressure (822.6 Hz), suggesting flame-acoustic interaction. In contrast, the M−flame, found at lower equivalence ratios, exhibits radial fluctuation modes, out-of-phase acoustic decoupling, and lower sound intensity. Sound intensity shows a linear correlation with equivalence ratio; as lean blowout (LBO) nears, the flame structure becomes incoherent, and turbulence dominates external noise. Increasing the inlet temperature or adding an exit plate shifts the flame anchoring point upstream. Higher inlet temperatures lower air density, raising axial velocity and shrinking inner recirculation zones, promoting a V-flame near the nozzle exit. Similarly, adding an exit plate increases the pressure gradient in reverse flow regions, pushing the flame upstream. Inlet temperature amplifies axial fluctuation modes, while the exit plate enhances an axial-radial fluctuation mode. Larger confinement ratios, such as 6.9 and 9.6, enlarge the inner recirculation zone and favor radial fluctuation modes, with sound pressure levels shifting by up to 15 dB during flame structure transitions. These parameters influence the LBO limit, critical for NOx emissions.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111541"},"PeriodicalIF":2.8,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144239610","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}

引用次数: 0

Flow dynamics in cavitation induced micro pumping 空化诱导微泵的流动动力学

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-04 DOI: 10.1016/j.expthermflusci.2025.111540

V. Agrež, J. Zevnik, Ž. Lokar, M. Dular, R. Petkovšek

{"title":"Flow dynamics in cavitation induced micro pumping","authors":"V. Agrež, J. Zevnik, Ž. Lokar, M. Dular, R. Petkovšek","doi":"10.1016/j.expthermflusci.2025.111540","DOIUrl":"10.1016/j.expthermflusci.2025.111540","url":null,"abstract":"<div><div>The micro pumping process driven by the laser induced cavitation bubbles is scalable, requires only optical access and does not require mechanical moving parts. We investigate how the positioning of the cavitation bubble affects the flow dynamics through differently sized holes in a transparent boundary mimicking a microchannel. For normalized standoff distance above 0.8 and normalized hole radius of 0.22 a significant flow through a hole was observed while decreasing the standoff distance a focused reverse flow was formed impeding downward pumping flow. The details of reverse flow formation were investigated. It was found that bubbles generated next to larger holes with a normalized radius of 0.66 also produce reverse flow, however without it impeding the flow through the structure, even at small normalized standoff distances. Simulations were found to agree well with experiments and used to further study the pumping behavior. Indentation on the bottom side of the bubble was found to be the driver of the focused reverse flow in simulations and differences were investigated for various hole radii and standoff distances. For larger hole radii, reverse flow was found to be both weaker and failed to block the entire hole width, permitting pumping behavior. To improve the flow in the pumping direction, additional structures were produced on top of the flat plate with holes. It was found that adding the entry structure to the hole mitigated the effect of the focused reverse flow on the pumping action.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111540"},"PeriodicalIF":2.8,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144239611","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}

引用次数: 0

Enhancement of the anti-icing performance by surface modification during droplet impact on subcooled surfaces 液滴撞击过冷表面时表面改性提高抗冰性能

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-03 DOI: 10.1016/j.expthermflusci.2025.111539

Xiaowei Yang, Xiaohua Liu, Hongyu Ge, Heyu Jin, Junnan Jiang

{"title":"Enhancement of the anti-icing performance by surface modification during droplet impact on subcooled surfaces","authors":"Xiaowei Yang, Xiaohua Liu, Hongyu Ge, Heyu Jin, Junnan Jiang","doi":"10.1016/j.expthermflusci.2025.111539","DOIUrl":"10.1016/j.expthermflusci.2025.111539","url":null,"abstract":"<div><div>Icing phenomena during droplet impact on subcooled surfaces frequently cause economic losses and safety problems in industry. In this paper, the processes of droplet impact on subcooled flat surfaces were experimentally studied by high-speed camera technique. The results indicated that increases in Weber number (<em>We</em>) and surface subcooling (Δ<em>T</em>) were unfavorable to anti-icing on the copper surface. This was caused by shortening the icing delay time and icing time, while increasing the icing diameter. The connection between icing morphology and icing characteristics was established. Through surface modification, the copper surface was successfully converted into a superhydrophobic one. This superhydrophobic surface enhanced anti-icing performance by promoting droplet rebound or reducing the icing diameter. A critical formula for predicting droplet rebound under different <em>We</em> and Δ<em>T</em> was provided. Increasing both <em>We</em> and Δ<em>T</em> was unfavorable for droplet to leave the surface. When the droplet rebounded from the surface, the contact time increased slightly with Δ<em>T</em>, but was less significantly affected by <em>We</em>. When the droplet failed to rebound, the icing diameter increased with <em>We</em> and Δ<em>T</em>. However, it remained smaller than that on copper surfaces under the same conditions, which was beneficial for anti-icing. These findings provide valuable insights for the advancement of anti-icing technologies.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111539"},"PeriodicalIF":2.8,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144229598","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}

引用次数: 0

Investigating condensation heat transfer and flow pattern of R1233zd(E) in hyper-, micro- and normal gravity conditions 研究了R1233zd(E)在超重力、微重力和正常重力条件下的冷凝传热和流动模式

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-03 DOI: 10.1016/j.expthermflusci.2025.111537

Nicolò Mattiuzzo , Arianna Berto , Gaëtan Brunetto , Patrick Queeckers , Stefano Bortolin , Andrey Glushchuk , Marc Miscevic , Marco Azzolin , Pascal Lavieille

{"title":"Investigating condensation heat transfer and flow pattern of R1233zd(E) in hyper-, micro- and normal gravity conditions","authors":"Nicolò Mattiuzzo , Arianna Berto , Gaëtan Brunetto , Patrick Queeckers , Stefano Bortolin , Andrey Glushchuk , Marc Miscevic , Marco Azzolin , Pascal Lavieille","doi":"10.1016/j.expthermflusci.2025.111537","DOIUrl":"10.1016/j.expthermflusci.2025.111537","url":null,"abstract":"<div><div>The increasing duration and complexity of space missions for extra-terrestrial exploration have raised the need for developing more reliable and efficient thermal control systems (TCS). In fact, TCS are aimed at supporting life in shuttles and planetary bases and ensuring the proper operation of instrumentation for experiments. Consequently, their study is of high interest, particularly as TCS are required to reduce their weight and volume. This latter requirement has led to the introduction of two-phase heat transfer systems in place of traditional single-phase ones. As a result, two-phase heat transfer processes need to be thoroughly studied under reduced gravity conditions to ensure the adequate design of thermal control systems for space applications.</div><div>In this work, the condensation heat transfer of R1233zd(E) was studied during the 84<sup>th</sup> ESA Parabolic Flight Campaign using a 3.38 mm inner diameter channel. Experiments were conducted under hyper-, micro- and normal gravity conditions at saturation temperature equal to 40 °C and mass fluxes equal to 30 kg m<sup>−2</sup> s<sup>−1</sup> and 40 kg m<sup>−2</sup> s<sup>−1</sup>. The results reveal a significant reduction in heat transfer coefficients under microgravity conditions, with annular flow patterns being predominantly observed. Notably, this study presents experimental condensation data under hyper-gravity conditions for the first time. Comparisons with HFE-7000 data (tested during a previous Parabolic Flight Campaign) and evaluations against existing correlations are presented, highlighting the need for accurate predictive models for condensation heat transfer in microgravity and hyper-gravity.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111537"},"PeriodicalIF":2.8,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290591","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}

引用次数: 0

Performance analysis of novel wavy-wall-based flow control method for wind turbine blade 基于波浪壁的新型风力机叶片流动控制方法的性能分析

IF 2.8 2区工程技术

Experimental Thermal and Fluid Science Pub Date : 2025-06-01 DOI: 10.1016/j.expthermflusci.2025.111527

Artur Dróżdż , Vasyl Sokolenko , Witold Elsner

{"title":"Performance analysis of novel wavy-wall-based flow control method for wind turbine blade","authors":"Artur Dróżdż , Vasyl Sokolenko , Witold Elsner","doi":"10.1016/j.expthermflusci.2025.111527","DOIUrl":"10.1016/j.expthermflusci.2025.111527","url":null,"abstract":"<div><div>In this paper, the experimental study in flat-plate turbulent boundary layer (TBL) under various Reynolds number and adverse pressure gradient (APG) conditions was performed downstream of the wavy wall, which proved to be effective in delaying flow separation in Dróżdż et al. (2021). Three Reynolds numbers that reproduce the effect of slow changes in wind conditions on a large-scale pitch adjusted wind turbine (range of wind speed: <span><math><mrow><mn>5</mn><mo>−</mo><mn>40</mn><mspace></mspace><mi>m/s</mi></mrow></math></span>) and three pressure gradient evolutions that reproduce sudden changes in the relative inflow wind angle resulting from a rotation cycle and/or a blade torsional deflection cycle were analysed. The effect of Reynolds number was found to have a weak dependence on the performance of the method, since there was only about a 2% reduction in performance in the Reynolds number range studied, compared to the maximum efficiency of 15.5%. In contrast, for the maximum change in the pressure gradient, a decrease of 8.8% in the efficiency of the flow control method was reported. Assuming that a strong change in the pressure distribution occurs for at most a quarter of the blade deflection cycle, the rotor efficiency decreases by no more than 3.5%. Thus, the total efficiency of the method is not less than 10%. The results show that the chosen corrugation geometry works well under both nominal and off-design wind turbine rotor conditions. It was also shown that the method’s efficiency in postponing flow separation can be evaluated by increasing or maintaining total momentum, quantified by the changes in momentum-loss thickness due to wavy wall.</div></div>","PeriodicalId":12294,"journal":{"name":"Experimental Thermal and Fluid Science","volume":"169 ","pages":"Article 111527"},"PeriodicalIF":2.8,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221994","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}

引用次数: 0