International Journal of Heat and Fluid Flow最新文献

{"title":"Outer scaling of rough and smooth wall boundary layers under adverse pressure gradient conditions","authors":"Ralph J. Volino ,&nbsp;Michael P. Schultz","doi":"10.1016/j.ijheatfluidflow.2025.109821","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109821","url":null,"abstract":"<div><div>Experiments were conducted in adverse pressure gradient (APG) boundary layers over rough and smooth walls. Cases were considered with various pressure gradient strengths and upstream conditions. Profiles of mean velocity and turbulence quantities were measured at multiple streamwise stations to document the response of the flow to the APG. The data suggest that an APG causes attached turbulent eddies to become detached, and motivates the proposal of a new scaling to collapse the data in the outer part of the boundary layer. The distance from the wall is normalized as <em>y*=(y − δ*)/(</em>δ<em>-</em>δ<em>*</em>), where <em>δ</em> and <em>δ</em>* are the boundary layer thickness and displacement thickness, respectively. Velocity is scaled using the friction velocity at the start of the APG region. Data from all cases in which an APG is imposed on a canonical zero pressure gradient (ZPG) boundary layer show good collapse of the mean velocity and Reynolds stress profiles with the new scaling. For cases in which an APG followed directly after a favorable pressure gradient (FPG), the initial development of the boundary layer was changed, but after some distance the new scaling again collapsed the profiles.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109821"},"PeriodicalIF":2.6,"publicationDate":"2025-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143680022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of the Weber number and structural parameters on combustion characteristics of LOX/methane liquid–liquid swirl coaxial injectors","authors":"Ping Jin ,&nbsp;Danqi Yang ,&nbsp;Bingyang Liu ,&nbsp;Yushan Gao ,&nbsp;Guobiao Cai","doi":"10.1016/j.ijheatfluidflow.2025.109817","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109817","url":null,"abstract":"<div><div>LOX/methane engines have the advantages of a<!--> <!-->rich source, good cooling performance, low combustion temperature, difficult coking, etc., and a broad application prospect in reusable liquid rocket engines. Reasonable injector design is the key to organizing efficient and stable combustion of the engine. Among various types of injectors, the liquid–liquid swirl coaxial injector is widely used in a variety of two-component liquid rocket engines for its good atomization and high mixing efficiency. In order to comprehensively study the influence of multiple factors on combustion characteristics of LOX/methane liquid–liquid swirl coaxial injection, a 3-D combustion simulation model based on the improved 6-step mechanism is established. The simulation results of the Weber number show that when the ɷ (the Weber number ratio of methane to LOX) is in the range of 0.71 ∼ 2.64, the longest combustion length is found for ɷ of 1.36. Decreasing or increasing either propellant Weber number will shorten the combustion length. Further, combustion efficiency increases with increment of mixing ratio as well as decreasing ɷ. The simulation results of the structural parameters show that the combustion efficiency increases as the geometric characteristic coefficient (in the range of 0.5 ∼ 2.5) of the inner injector and the recess length (in the range of 0.42 ∼ 2.1) grow. The same rotation of the inner and outer injectors can effectively shorten the combustion length, but the reverse rotation has a higher combustion efficiency. The work can provide a theoretical basis for the optimal design of LOX/methane liquid–liquid swirl coaxial injectors and support the development of high-performance reusable LOX/methane engines.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109817"},"PeriodicalIF":2.6,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143680021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of pool boiling performance on a surface with copper nanowire arrays using molecular dynamics","authors":"Xin Wang,&nbsp;Hongxian Du,&nbsp;Tiansheng Li,&nbsp;Jin Wang,&nbsp;Dan Zheng","doi":"10.1016/j.ijheatfluidflow.2025.109818","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109818","url":null,"abstract":"<div><div>The heat flux increases due to the miniaturization and integration of semiconductor components. Overheating issues necessitate reliable cooling solutions. Pool boiling effectively meets the cooling requirements of semiconductor devices due to its superior heat transfer efficiency. This study investigates the heat transfer of pool boiling on textured substrates featuring nanowire arrays of varying heights. Nanowire arrays are arranged on the bottom wall in three rows and three columns. Liquid argon serves as the working fluid. The height of nanowire arrays is 10 nm, 20 nm, and 30 nm. Nanowire arrays possess the same interval of 10 nm and a diameter of 5 nm. The dynamics behaviors are analyzed on four surfaces. The results show that nanowire arrays remarkably inhibit the transition from nucleate boiling state to film boiling state. Compared to the plain substrate, textured substrate exhibits a maximum temperature increase of 33.7 K during the boiling process. The energy obtained by argon and the number of vapor argon atoms simultaneously increases with the increase of nanowire height. The enhancement heat transfer mechanisms are elucidated through simulation results. Liquid surrounding nanowire arrays absorbs additional thermal energy from sidewalls, resulting in heat accumulation and enhancement of heat transfer. The nanowire arrays with a height of 30 nm demonstrate the highest heat transfer enhancement. Compared with the plain substrate, nanowire arrays achieve a striking heat flux increase, reaching 7168.1 MW/m². This study investigates the nanoscale enhancement mechanism of pool boiling, offering guidance for improved cooling performance of electronic devices.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109818"},"PeriodicalIF":2.6,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143680020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A novel strategy for numerical analysis of nonharmonic laser-induced acoustic streaming","authors":"Runjia Li ,&nbsp;Feng Lin ,&nbsp;Jiming Bao ,&nbsp;Dong Liu","doi":"10.1016/j.ijheatfluidflow.2025.109802","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109802","url":null,"abstract":"<div><div>Acoustic streaming in microfluidics has traditionally been driven by harmonic acoustic waves generated from on-chip ultrasound transducers. Laser-induced acoustic streaming (laser streaming) offers a transducer-free, light-driven approach to microfluidic actuation. However, the highly nonharmonic nature of laser streaming hinders its analysis using conventional methods. This work introduces a novel strategy to bridge this gap and enables quantitative numerical modeling of laser streaming. This method decomposes the nonharmonic ultrasonic field generated by pulsed laser heating into harmonic components using Fourier series expansion. The dominant components, selected from energy spectrum analysis, are then solved using successive approximations to yield the time-averaged streaming force, which incorporated into second-order streaming equations to determine the streaming field. The simulation results demonstrate good agreement with experimental data and other numerical models. This new strategy significantly reduces the computational costs while enhancing insights into the laser streaming physics. It also provides a versatile tool for analyzing general forms of acoustic streaming induced by nonharmonic sources.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109802"},"PeriodicalIF":2.6,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143644048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of the three-phase spiral countercurrent heat exchange and fluid dynamics in an innovative high-temperature particle waste heat recovery system","authors":"Anxiang Shen ,&nbsp;Tao Wang ,&nbsp;Huijie Xu ,&nbsp;Yutao Shi ,&nbsp;Yang Chen ,&nbsp;Jianqiu Zhou","doi":"10.1016/j.ijheatfluidflow.2025.109814","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109814","url":null,"abstract":"<div><div>A novel steel slag rapid cooling and heat recovery system has been proposed. Gas-liquid–solid coupled heat transfer is adopted to recover waste heat. It only needs very little air velocity and air volume, which greatly reduces the energy consumption. The key component (the spiral coil) has been simulated to study the kinetic energy transfer and heat exchange process. This study examines both the heat transfer characteristics and the fluid dynamics of particles throughout the entire spiral coil. The distribution of particles across the flow path has also been subjected to analysis. Additionally, this study has focused on evaluating the heat transfer efficiency. The performance of the novel system is evaluated with different parameters. It shows that When <em>m</em>_slag is 0.5 kg/s, <em>u</em>_{air_in} is 1 m/s, the system waste heat recovery performance reaches the maximum (<em>Q</em>_water = 16.33 kW, <em>Q</em>_air = 1.08 kW, <em>Q</em>_blower = −0.82 kW). The present work provides a theoretical basis for further improving the steel slag waste heat recovery efficiency.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109814"},"PeriodicalIF":2.6,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Computational investigation of heat transfer and frictional loss of fin-tube heat exchanger with delta winglet and shear-thinning fluid","authors":"Dheeraj Kumar ,&nbsp;Amaresh Dalal","doi":"10.1016/j.ijheatfluidflow.2025.109800","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109800","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The flow characteristics of a shear-thinning fluid and their significant impacts on the heat transfer and pressure drop effectiveness of a finned-tube heat exchanger (FTHE) incorporating delta winglet vortex generators (DWVG) have been analyzed numerically. This study employed a three-dimensional numerical approach taking into account only the laminar flow of incompressible and single-phase fluid and disregarding the impact of body forces, compressibility, and radiation. The ANSYS FLUENT 2021 R1 was used to simulate the computational domain. Specifically, the flow domain comprises a rectangular duct containing three rows of inherent cylinders and punched delta winglets mounted at various attack angles (&lt;span&gt;&lt;math&gt;&lt;mi&gt;β&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;) (160°, 165°, and 170°). The simulation was conducted over a range of Reynolds numbers (Re) from 50 to 200, using a carboxymethyl cellulose (CMC) aqueous solution at a concentration of 2000 ppm as a shear-thinning fluid. The outcomes of present study in terms of the average Nusselt number (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;), apparent friction factor (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;), and quality factor (&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;) were compared to those of a channel with a rectangular winglet vortex generators (RWVG) and a base channel without a DWVG. The results indicated that, compared to the rectangular winglet, the implementation of the DWVG caused a 28% decrease in &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and a 34% decrease in &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, while &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; increased by 9%. In contrast, compared to the base channel, &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;, and &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; are increased by 81%, 33%, and 36%, respectively. The results indicate that, compared to DWVGs, RWVGs enhance heat transfer, but this comes with a significant pressure drop. Using aqueous solutions of carboxymethylcellulose as a working fluid in a channel with DWVGs enhances the &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;N&lt;/mi&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;u&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;m&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;Q&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 147% and 104% respectively and decreases the &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mrow&gt;&lt;mi&gt;f&lt;/mi&gt;&lt;/mrow&gt;&lt;mrow&gt;&lt;mi&gt;a&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;mi&gt;p&lt;/mi&gt;&lt;/mrow&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; by 40% compared to w","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109800"},"PeriodicalIF":2.6,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143631755","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Production and survival of early turbulence due to flow modulation at the duct inlet","authors":"Md Ashfaqul Bari,&nbsp;Manuel Münsch,&nbsp;Jovan Jovanović,&nbsp;Antonio Delgado","doi":"10.1016/j.ijheatfluidflow.2025.109792","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109792","url":null,"abstract":"<div><div>The paper reports a fully resolved numerical simulation of turbulent duct flow developing under complex inlet flow conditions at very low Reynolds number <span><math><mrow><mi>R</mi><msub><mrow><mi>e</mi></mrow><mrow><mi>m</mi></mrow></msub><mo>=</mo><mn>1250</mn><mo>−</mo><mn>4070</mn></mrow></math></span> based on the channel width and bulk velocity. Turbulence was initiated by inflectional instabilities created at the duct center owing to the special inlet design. All simulations were performed using the open-source software OpenFOAM. Computations reveal that turbulence persisted over more than 60 turnover time. Its statistical features were characterized by distributions of the mean flow and turbulent stresses at multiple duct locations. The turbulent stresses were used to analyze the anisotropic nature of turbulence by evaluating trajectories of across the anisotropy-invariant map which bounds all realizable states of turbulence. The limiting behavior of turbulence stresses reveals explosive production of the dissipation at the wall. This evidence suggests that the chief mechanisms involved during the transition process and self-maintenance of turbulence at very low Reynolds numbers is related to the dynamics of the turbulent dissipation rate which attains the maximum amplification by approaching the two-component isotropic state at the wall.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109792"},"PeriodicalIF":2.6,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143611586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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":"To what extent does local oscillation influence the thermal performance of finned PCM-based energy storage systems: A numerical study","authors":"Amir Hossein Vakilzadeh ,&nbsp;Amirhossein Bagheri Sarvestani ,&nbsp;Kourosh Javaherdeh ,&nbsp;Reza Kamali ,&nbsp;Satyam Panchal","doi":"10.1016/j.ijheatfluidflow.2025.109798","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109798","url":null,"abstract":"<div><div>Enhancing the thermal performance of phase change materials (PCMs) is vital for improving the efficiency of energy storage systems. While fins are widely used to expedite the melting process by boosting thermal conductivity, their effectiveness diminishes as melting progresses and natural convection becomes dominant. Meanwhile, local mechanical oscillation has emerged as a promising technique to further accelerate melting, though its isolated use has been the primary focus of prior studies. The combined effect of fins and local oscillation, particularly their interaction in influencing the heat transfer dynamics of PCM, remains unexplored. Thus, this study develops a numerical model to investigate the interaction between various fin configurations (namely, sinusoidal, and positive/negative straight fins) and local oscillation within a finned rectangular enclosure. Moreover, the local oscillator’s placement on the hot wall, as well as its proximity to the fins, are among key factors analyzed. The results demonstrate that negative rectangular fins consistently deliver superior thermal performance, while the effectiveness of local oscillation diminishes when placed between fins, particularly as the melting front progresses. The optimal configuration is a vertical oscillator positioned at the base of the hot wall near a negative fin, which achieves a 64.3 % reduction in melting time. Notably, as the lower fin is installed closer the bottom wall of the enclosure, two distinct mechanisms arising from extension of the heating area and local flow stimulation by the oscillator plate, though differing fundamentally, result in similar effects during the later stages of the melting process, thereby diminishing the overall influence of localized oscillation on the melting process.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109798"},"PeriodicalIF":2.6,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143611585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 the flow pattern and heat transfer characteristics of the refrigerant flow condensation through metal foam inserts","authors":"Mohamad Vahid Rafieinejad ,&nbsp;Rasool Mohammadi ,&nbsp;Mohammad Ali Akhavan-Behabadi ,&nbsp;Behrang Sajadi","doi":"10.1016/j.ijheatfluidflow.2025.109801","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109801","url":null,"abstract":"<div><div>Metal foams have shown remarkable effects on heat transfer improvement in diabatic two-phase flows, especially for refrigeration applications. The present experimental study addresses the flow condensation regimes and characteristics of R134a in 10 PPI and 20 PPI copper foam inserts inside 8 mm i.d. tubes. The flow pattern maps were extracted under uniform wall temperature boundary conditions for mass flux 75–150 kg m⁻² s⁻¹. In this study, three distinct flow regimes are introduced in the presence of metal foams: stratified–wavy, wavy–annular, and annular. Although the outcomes prove that the PPI of metal foam is a determining factor for the distribution of flow patterns on the map, the stratified–wavy regime is majorly captured at low-quality and low-mass flux zones, while the annular pattern is only observable at high-quality and high-mass flux zone of the maps. The flow maps revealed that the annular to wavy–annular regime transition withdraws from a vapor quality of 0.6 to approximately 0.3 at the highest mass flux. Similarly, the wavy–annular to stratified–wavy pattern transition falls back from a quality of 0.7 to around 0.35 at the mass flux of 100 kg m⁻² s⁻¹. In addition, this research investigates how vapor quality, mass flux, and foam pore density affect heat transfer and pressure losses during condensation. An intensive correlation between heat transfer coefficient and flow variables of mass flux and vapor quality is noted. 20 PPI foam owns larger heat transfer coefficients than 10 PPI, while the pressure drop within the 20 PPI insert is significantly larger than in 10 PPI. The metal foam inserts helped enhance the heat transfer coefficient by about 220 %. The findings show that the pressure drop progressively elevates as the quality of vapor and mass flux rise. The use of copper foam inserts of 20 PPI, particularly at high vapor qualities, is beneficial in applications where heat transfer enhancement is a priority.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109801"},"PeriodicalIF":2.6,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143591552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characteristics of turbulent Taylor-Couette flow of low-viscosity fluid on plastron-covered superhydrophobic surface","authors":"Seongbin Ahn ,&nbsp;Sungwon Jo ,&nbsp;Woobin Song ,&nbsp;Haeyeon Lee ,&nbsp;Garam Ku ,&nbsp;Minjae Kim ,&nbsp;Dong Rip Kim ,&nbsp;Simon Song","doi":"10.1016/j.ijheatfluidflow.2025.109805","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109805","url":null,"abstract":"<div><div>This study introduces a newly developed Taylor-Couette (TC) flow system designed to investigate flow dynamics in low-viscosity fluids, such as water, under fully turbulent conditions. To ensure precise drag measurements, the system accounts for mechanical friction from bearings and von Kármán torque (the torque generated by fluid motion in the gap between the end-plates of the cylinders), enabling accurate evaluation of TC torque. Utilizing exact counter-rotation conditions that produce featureless turbulence, we explored the drag reduction capabilities of a hybrid superhydrophobic surface (SHS) mounted on the inner cylinder, alongside visualizing the resultant plastron formations. For the first time, two-dimensional particle image velocimetry (2D PIV) was used near the wall to quantify drag reduction based on total shear stress derived from flow visualization on SHS in a TC flow system. The plastron-induced slip conditions led to significant shifts in bulk velocity within the TC gap. A detailed analysis of Reynolds stresses revealed substantial modifications in flow dynamics, including reduced peak Reynolds stress and increased near-wall Reynolds stress, while total shear stress decreased across the gap. Additionally, simultaneous visualization and assessment of the plastron provided novel insights into its role in enhancing drag reduction. These findings underscore the importance of accounting for bearing mechanical friction in torque measurements when using low-viscosity fluids and confirm the effectiveness of SHS in modifying turbulence for drag reduction. The results highlight the TC-PIV system’s robust capability for detailed fluid dynamics investigations and its potential to inform hydrodynamic drag reduction strategies.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"114 ","pages":"Article 109805"},"PeriodicalIF":2.6,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579883","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}