Pub Date : 2025-10-24DOI: 10.1016/j.ijheatfluidflow.2025.110119
Guanzhen Liu , Xiaoyong Yang , Leping Zhou , Xiaoze Du
The dynamic coupling between Marangoni flows and capillary forces during thin-film evaporation governs microscale transport but lacks spatiotemporal resolution near contact lines. Here, we employ multilayer nanoparticle image velocimetry (MnPIV) with < 50 nm spatial resolution to quantify Triton X-100-mediated flow restructuring in evaporating liquid films. Real-time tracking reveals surfactant concentration gradients trigger a bistable flow regime: sub-critical micelle concentration (sub-CMC) systems exhibit axisymmetric Marangoni vortices, while supra-CMC conditions generate toroidal instability cells that redirect solute transport via shear-aligned pathways. Film thinning bifurcates into two distinct phases: slow capillary-dominated linear thinning (0.8 nm/s for thickness > 200 nm) transitions to Marangoni-accelerated collapse (5.2 nm/s acceleration below critical thickness), governed by the Marangoni/Capillary fluid. Energy barrier reduction (up to 85 % at CMC) mediates dynamic contact line behavior, with tracer particles revealing flow restructuring. We establish that micellization amplifies viscous dissipation, with a measured suppression of capillary compensation flows ranging from 70.6 % to 81.5 % (as calculated from the top-layer droplet velocity, with an uncertainty of approximately 8 %), while simultaneously enhancing interfacial stress fluctuations. This work provides a predictive framework for interfacial instabilities in surfactant-modulated phase-change systems, with implications for microfluidic manipulation and thermal management.
薄膜蒸发过程中马兰戈尼流和毛细力之间的动态耦合控制着微尺度的输运，但在接触线附近缺乏时空分辨率。在这里，我们使用<； 50 nm空间分辨率的多层纳米颗粒图像测速（MnPIV）来量化Triton x -100介导的蒸发液膜中的流动重组。实时跟踪显示，表面活性剂浓度梯度触发双稳态流动：亚临界胶束浓度（亚cmc）系统表现出轴对称的马兰戈尼漩涡，而超cmc条件产生环形不稳定细胞，通过剪切排列路径重新定向溶质运输。薄膜变薄分为两个不同的阶段：缓慢的毛细管主导的线性变薄（厚度为0.8 nm/s, 200 nm）过渡到马兰戈尼加速的坍塌（在临界厚度以下加速5.2 nm/s），由马兰戈尼/毛细管流体控制。能量势垒还原（在CMC下高达85%）介导了动态接触线行为，示踪颗粒揭示了流动重组。我们确定胶束化放大了粘性耗散，测量到的毛细补偿流的抑制范围为70.6%至81.5%（根据顶层液滴速度计算，不确定度约为8%），同时增强了界面应力波动。这项工作为表面活性剂调制相变系统的界面不稳定性提供了一个预测框架，对微流体操纵和热管理具有重要意义。
{"title":"Interfacial flow instability in surfactant-laden thin films: high-resolution velocimetry of marangoni-capillary competition during droplet evaporation","authors":"Guanzhen Liu , Xiaoyong Yang , Leping Zhou , Xiaoze Du","doi":"10.1016/j.ijheatfluidflow.2025.110119","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110119","url":null,"abstract":"<div><div>The dynamic coupling between Marangoni flows and capillary forces during thin-film evaporation governs microscale transport but lacks spatiotemporal resolution near contact lines. Here, we employ multilayer nanoparticle image velocimetry (MnPIV) with < 50 nm spatial resolution to quantify Triton X-100-mediated flow restructuring in evaporating liquid films. Real-time tracking reveals surfactant concentration gradients trigger a bistable flow regime: sub-critical micelle concentration (sub-CMC) systems exhibit axisymmetric Marangoni vortices, while supra-CMC conditions generate toroidal instability cells that redirect solute transport via shear-aligned pathways. Film thinning bifurcates into two distinct phases: slow capillary-dominated linear thinning (0.8 nm/s for thickness > 200 nm) transitions to Marangoni-accelerated collapse (5.2 nm/s acceleration below critical thickness), governed by the Marangoni/Capillary fluid. Energy barrier reduction (up to 85 % at CMC) mediates dynamic contact line behavior, with tracer particles revealing flow restructuring. We establish that micellization amplifies viscous dissipation, with a measured suppression of capillary compensation flows ranging from 70.6 % to 81.5 % (as calculated from the top-layer droplet velocity, with an uncertainty of approximately 8 %), while simultaneously enhancing interfacial stress fluctuations. This work provides a predictive framework for interfacial instabilities in surfactant-modulated phase-change systems, with implications for microfluidic manipulation and thermal management.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110119"},"PeriodicalIF":2.6,"publicationDate":"2025-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358684","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}
The aerothermal performance of high-pressure turbine blade tips has a significant impact on engine efficiency and component durability. Among various tip configurations, the squealer tip design is widely adopted due to its ability to mitigate leakage losses and reduce heat loads. The present research investigates the aerothermal performance of different squealer tip designs both experimentally and numerically, including an inclined pressure-side rim and a cavity partition rib. Especially, the high-speed relative casing motion is included in this study. The results indicate that the inclined rim has a negligible influence on the blade tip aerothermal behaviours compared to the conventional straight rim design, but adding a partition rib significantly influences the blade tip flow structures as well as the tip heat transfer conditions, resulting in a notable increase of pitchwise-averaged HTC values of around 10% in the 0.1–0.4 region of blade tip. The averaged tip heat transfer coefficient values of various designs are similar, with a difference of around 3% in both experimental and numerical results. Furthermore, the cooling performance for the various squealer tip designs is explored, and the partition rib design introduces difficulties in the cooling of the suction-side cavity, with a reduction of cooling effectiveness of 30% in the 0.4–0.5 region from the experimental results. The results suggest that the cooling strategy for the partition rib squealer tip design requires further investigation due to its more complex tip flow structure.
{"title":"Aerothermal investigation of tip flow structures and heat transfer characteristics of different high-pressure turbine blade squealer tip designs","authors":"Hongmei Li, Ziyang Zhang, Shaopeng Lu, Hongmei Jiang, Yun Jin, Jinfang Teng","doi":"10.1016/j.ijheatfluidflow.2025.110118","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110118","url":null,"abstract":"<div><div>The aerothermal performance of high-pressure turbine blade tips has a significant impact on engine efficiency and component durability. Among various tip configurations, the squealer tip design is widely adopted due to its ability to mitigate leakage losses and reduce heat loads. The present research investigates the aerothermal performance of different squealer tip designs both experimentally and numerically, including an inclined pressure-side rim and a cavity partition rib. Especially, the high-speed relative casing motion is included in this study. The results indicate that the inclined rim has a negligible influence on the blade tip aerothermal behaviours compared to the conventional straight rim design, but adding a partition rib significantly influences the blade tip flow structures as well as the tip heat transfer conditions, resulting in a notable increase of pitchwise-averaged HTC values of around 10% in the 0.1–0.4 <span><math><mrow><msub><mi>C</mi><mrow><mi>x</mi></mrow></msub></mrow></math></span> region of blade tip. The averaged tip heat transfer coefficient values of various designs are similar, with a difference of around 3% in both experimental and numerical results. Furthermore, the cooling performance for the various squealer tip designs is explored, and the partition rib design introduces difficulties in the cooling of the suction-side cavity, with a reduction of cooling effectiveness of 30% in the 0.4–0.5 <span><math><mrow><msub><mi>C</mi><mrow><mi>x</mi></mrow></msub></mrow></math></span> region from the experimental results. The results suggest that the cooling strategy for the partition rib squealer tip design requires further investigation due to its more complex tip flow structure.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110118"},"PeriodicalIF":2.6,"publicationDate":"2025-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358680","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}
Pub Date : 2025-10-22DOI: 10.1016/j.ijheatfluidflow.2025.110117
Xinming Du , Zhaohui Wang , Rongqing Bao , Shousheng Hong , Haonan Yang , Hongxia Wang
To address the temperature non-uniformity in conventional uniform cooling channels caused by flow distance, this study proposes a novel battery thermal management strategy using gradient-filled Triply Periodic Minimal Surface (TPMS) porous structures in liquid-cooling channels. Unlike traditional uniform designs, the gradient configuration optimizes both thermal performance and flow resistance. Numerical simulations reveal that the gradient-filled TPMS channels significantly enhance temperature uniformity across the battery module while maintaining low pumping power. Specifically, the two-segment gradient design reduces the maximum temperature difference (△T) to 3.8°C—a 27.34 % improvement over straight channels and 20.67 % over uniformly filled TPMS channels. Furthermore, the system operates efficiently at low flow rates (1.0–1.3 g/s), avoiding high energy consumption. This work demonstrates the potential of gradient-filled TPMS structures as a high-performance, energy-efficient solution for advanced battery thermal management systems.
{"title":"Numerical study on the heat dissipation performance of lithium-ion batteries with gradient-filled TPMS channel structures","authors":"Xinming Du , Zhaohui Wang , Rongqing Bao , Shousheng Hong , Haonan Yang , Hongxia Wang","doi":"10.1016/j.ijheatfluidflow.2025.110117","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110117","url":null,"abstract":"<div><div>To address the temperature non-uniformity in conventional uniform cooling channels caused by flow distance, this study proposes a novel battery thermal management strategy using gradient-filled Triply Periodic Minimal Surface (TPMS) porous structures in liquid-cooling channels. Unlike traditional uniform designs, the gradient configuration optimizes both thermal performance and flow resistance. Numerical simulations reveal that the gradient-filled TPMS channels significantly enhance temperature uniformity across the battery module while maintaining low pumping power. Specifically, the two-segment gradient design reduces the maximum temperature difference (△<em>T</em>) to 3.8°C—a 27.34 % improvement over straight channels and 20.67 % over uniformly filled TPMS channels. Furthermore, the system operates efficiently at low flow rates (1.0–1.3 g/s), avoiding high energy consumption. This work demonstrates the potential of gradient-filled TPMS structures as a high-performance, energy-efficient solution for advanced battery thermal management systems.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110117"},"PeriodicalIF":2.6,"publicationDate":"2025-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358597","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}
This study presents a novel and comprehensive examination of heat transfer enhancement of non-Newtonian nanofluids in differentially heated domains with particular emphasis on the coupling effects between fluid rheology, geometry, and external forces. In contrast to earlier investigations, which more or less restrict the problem either to Newtonian simplifications or simple-governing parameters variations, this study examines more general and realistic configurations under thermal fluxes through employing different models to capture the shear-thinning behavior (Carreau and power-law models). The Navier-Stokes and energy equations are adjusted to consider the nanofluid altered properties using experimental models. The in-house code is validated experimentally and numerically with previous studies in different cases. The obtained results showed that while higher nanoparticle loading improves thermal conductivity, it may cause viscosity-induced heat deterioration, especially for horizontal cavities and high Rayleigh number. This deterioration is reversed by imposing intense external driving forces (high Pe). Additionally, the study also determines critical values of each governing parameter, as a function of the remaining ones, beyond which the nanofluid benefits exceed viscous costs. A key contribution is the construction of enhancement maps in the (Ra, n) plane for fixed A and Pe that identify operating conditions for heat transfer enhancement. This provides useful information for optimal design of engineering applications incorporating nanofluids, hence higher thermal performances in next-generation heat transfer technologies in energy, electronics cooling, and process engineering.
{"title":"Modeling and optimization of heat transfer and flow dynamics of non-Newtonian Carreau nanofluids in differentially heated enclosed domains: coupled effects of rheology, geometry, and external forces","authors":"Bilal El hadoui , Youssef Tizakast , Souad Tizakast , Mourad Kaddiri","doi":"10.1016/j.ijheatfluidflow.2025.110110","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110110","url":null,"abstract":"<div><div>This study presents a novel and comprehensive examination of heat transfer enhancement of non-Newtonian nanofluids in differentially heated domains with particular emphasis on the coupling effects between fluid rheology, geometry, and external forces. In contrast to earlier investigations, which more or less restrict the problem either to Newtonian simplifications or simple-governing parameters variations, this study examines more general and realistic configurations under thermal fluxes through employing different models to capture the shear-thinning behavior (Carreau and power-law models). The Navier-Stokes and energy equations are adjusted to consider the nanofluid altered properties using experimental models. The in-house code is validated experimentally and numerically with previous studies in different cases. The obtained results showed that while higher nanoparticle loading improves thermal conductivity, it may cause viscosity-induced heat deterioration, especially for horizontal cavities and high Rayleigh number. This deterioration is reversed by imposing intense external driving forces (high <em>Pe</em>). Additionally, the study also determines critical values of each governing parameter, as a function of the remaining ones, beyond which the nanofluid benefits exceed viscous costs. A key contribution is the construction of enhancement maps in the (<em>Ra, n</em>) plane for fixed <em>A</em> and <em>Pe</em> that identify operating conditions for heat transfer enhancement. This provides useful information for optimal design of engineering applications incorporating nanofluids, hence higher thermal performances in next-generation heat transfer technologies in energy, electronics cooling, and process engineering.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110110"},"PeriodicalIF":2.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358595","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}
Pub Date : 2025-10-21DOI: 10.1016/j.ijheatfluidflow.2025.110096
Max Peters , Hugo Quintens , Michele Bardi , Noud Maes , Nico Dam , Jeroen van Oijen
The mixing of fuel and ambient in a compression-igniting combustion engine is a critical process, affecting ignition delay, burn duration, and cycle efficiency. This study aims to visualize and quantify hydrogen mole fraction distributions resulting from high-pressure (10 MPa) hydrogen injections into an inert, pressurized (1 MPa) nitrogen ambient at room temperature. Using inverse planar laser-induced fluorescence, in which the ambient rather than the jet is seeded with a fluorescent tracer, two different injectors (nozzle hole sizes of 0.55 and 0.65 mm) and two different tracers (toluene and acetone) are compared.
It is concluded that a non-intensified CCD camera for fluorescence detection is superior to the use of an intensified one, due to the linear behavior on contrast. The two injectors produce similar jets in terms of jet penetration and angle. Jet penetration derived from inverse-LIF measurements agree with Schlieren data on nominally the same jets, but the hydrogen mole fractions are generally 2.5-5 percent lower than those obtained by planar Rayleigh scattering. Quasi-steadiness and self-similarity were found for ensemble-averaged mole fraction distributions of both injectors, which aligns with theory and highlights the importance of using RANS simulations or time-averaged experiments for future comparisons.
{"title":"Hydrogen mole fraction distributions inferred from inverse-LIF measurements on high-pressure hydrogen injections","authors":"Max Peters , Hugo Quintens , Michele Bardi , Noud Maes , Nico Dam , Jeroen van Oijen","doi":"10.1016/j.ijheatfluidflow.2025.110096","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110096","url":null,"abstract":"<div><div>The mixing of fuel and ambient in a compression-igniting combustion engine is a critical process, affecting ignition delay, burn duration, and cycle efficiency. This study aims to visualize and quantify hydrogen mole fraction distributions resulting from high-pressure (10 MPa) hydrogen injections into an inert, pressurized (1 MPa) nitrogen ambient at room temperature. Using inverse planar laser-induced fluorescence, in which the ambient rather than the jet is seeded with a fluorescent tracer, two different injectors (nozzle hole sizes of 0.55 and 0.65 mm) and two different tracers (toluene and acetone) are compared.</div><div>It is concluded that a non-intensified CCD camera for fluorescence detection is superior to the use of an intensified one, due to the linear behavior on contrast. The two injectors produce similar jets in terms of jet penetration and angle. Jet penetration derived from inverse-LIF measurements agree with Schlieren data on nominally the same jets, but the hydrogen mole fractions are generally 2.5-5 percent lower than those obtained by planar Rayleigh scattering. Quasi-steadiness and self-similarity were found for ensemble-averaged mole fraction distributions of both injectors, which aligns with theory and highlights the importance of using RANS simulations or time-averaged experiments for future comparisons.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110096"},"PeriodicalIF":2.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358682","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}
Pub Date : 2025-10-21DOI: 10.1016/j.ijheatfluidflow.2025.110107
Pan Wang , Qingshan Liu , Donghai Xu , Wenshan Peng , Feng Liu , Jian Hou , Zili Gong
In practical operation, seawater heat exchanger tubes are highly susceptible to fouling issues. The accumulation of fouling deposits significantly reduces heat transfer efficiency, leading to localized overheating or temperature excursions. These effects progressively degrade the mechanical performance of the heat exchanger and may ultimately trigger operational failures. Compared to conventional metallic materials, titanium alloys demonstrate exceptional corrosion resistance in seawater environments. This superior property establishes titanium alloys as the material of choice for seawater heat exchanger tubes. This study addresses the efficiency degradation and safety risks caused by fouling deposition during the operation of titanium alloy seawater heat exchanger tubes. A combined approach of experimental characterization and theoretical modeling was employed to simulate actual operating conditions by establishing an experimental system for evaluating fouling development in titanium alloy heat exchanger tubes. Utilizing scanning electron microscopy (SEM) alongside ImageJ image analysis techniques, the microstructural morphology, thickness distribution, and thermal resistance evolution of the fouling layer on the inner tube wall were quantitatively characterized throughout the experimental period. The experimental results demonstrate a pronounced temperature gradient response in fouling deposition: the initial deposition rate in high-temperature regions is significantly higher than in low-temperature areas, with fouling layer thickness increasing to 269.6 μm within 90 days. Accompanied by densification of the fouling layer and reduction in porosity, the fouling thermal resistance ultimately reaches 6.76 × 10-5 m2·K·W−1. Based on the Kern-Seaton theoretical framework, a fouling kinetics model incorporating dual mechanisms of deposition and detachment was developed, with crystal growth rate described via the Arrhenius equation coupled with diffusion–reaction mechanisms. After model refinement, the average relative error between experimental data and predicted results was controlled within 12.5 %. The study reveals the spatiotemporal evolution and thermodynamic driving mechanisms of fouling deposition inside titanium alloy heat exchanger tubes, providing a theoretical basis for antifouling design of titanium alloy seawater heat exchanger tubes.
{"title":"Investigation of fouling development and kinetics in titanium alloy seawater heat exchanger tubes","authors":"Pan Wang , Qingshan Liu , Donghai Xu , Wenshan Peng , Feng Liu , Jian Hou , Zili Gong","doi":"10.1016/j.ijheatfluidflow.2025.110107","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110107","url":null,"abstract":"<div><div>In practical operation, seawater heat exchanger tubes are highly susceptible to fouling issues. The accumulation of fouling deposits significantly reduces heat transfer efficiency, leading to localized overheating or temperature excursions. These effects progressively degrade the mechanical performance of the heat exchanger and may ultimately trigger operational failures. Compared to conventional metallic materials, titanium alloys demonstrate exceptional corrosion resistance in seawater environments. This superior property establishes titanium alloys as the material of choice for seawater heat exchanger tubes. This study addresses the efficiency degradation and safety risks caused by fouling deposition during the operation of titanium alloy seawater heat exchanger tubes. A combined approach of experimental characterization and theoretical modeling was employed to simulate actual operating conditions by establishing an experimental system for evaluating fouling development in titanium alloy heat exchanger tubes. Utilizing scanning electron microscopy (SEM) alongside ImageJ image analysis techniques, the microstructural morphology, thickness distribution, and thermal resistance evolution of the fouling layer on the inner tube wall were quantitatively characterized throughout the experimental period. The experimental results demonstrate a pronounced temperature gradient response in fouling deposition: the initial deposition rate in high-temperature regions is significantly higher than in low-temperature areas, with fouling layer thickness increasing to 269.6 μm within 90 days. Accompanied by densification of the fouling layer and reduction in porosity, the fouling thermal resistance ultimately reaches 6.76 × 10<sup>-5</sup> m<sup>2</sup>·K·W<sup>−1</sup>. Based on the Kern-Seaton theoretical framework, a fouling kinetics model incorporating dual mechanisms of deposition and detachment was developed, with crystal growth rate described via the Arrhenius equation coupled with diffusion–reaction mechanisms. After model refinement, the average relative error between experimental data and predicted results was controlled within 12.5 %. The study reveals the spatiotemporal evolution and thermodynamic driving mechanisms of fouling deposition inside titanium alloy heat exchanger tubes, providing a theoretical basis for antifouling design of titanium alloy seawater heat exchanger tubes.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110107"},"PeriodicalIF":2.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358596","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}
Pub Date : 2025-10-21DOI: 10.1016/j.ijheatfluidflow.2025.110097
Deepak Kumar , Akhilesh K. Sahu
This study numerically investigates the convective heat transfer characteristics of a rotating heated elliptic cylinder immersed in non-Newtonian power law fluid in an unconfined laminar flow regime. The cylinder rotates at a constant angular velocity while the surrounding fluid flows longitudinally at a uniform velocity, while the cylinder surface is maintained at a higher temperature than the ambient fluid. Investigations are carried out on a wide range of variable parameters, including cylinder aspect ratio (), rotational speed (), Reynolds number ( and 40), Prandtl number (), and power law index (). The results show that the heat transfer rate, represented by local and average Nusselt numbers (), is highly responsive to these parameters. The surface averaged Nusselt numbers exhibit periodic variation with angular rotation of the cylinder, with the amplitude significantly influenced by , , , and . Rotating elliptical cylinders consistently outperform circular cylinders in enhancing heat transfer, particularly in shear-thinning fluids and at higher values of and . The isotherm patterns further illustrate the effects of shape, rotation, and fluid behavior on thermal boundary layer characteristics. The results indicate that shear-thinning fluids () provide up to 25% higher heat transfer compared to Newtonian fluids. Cylinder rotation further augments convection, yielding about 30% improvement in heat transfer at higher rotation rates. At the end of the report, correlations were established for average Nusselt numbers were established to facilitate result interpolation for intermediate values of Re and and/or the estimation of changes in heat transfer in a new application.
{"title":"Convective heat transfer from a rotating elliptic cylinder to non-Newtonian fluid in laminar flow condition","authors":"Deepak Kumar , Akhilesh K. Sahu","doi":"10.1016/j.ijheatfluidflow.2025.110097","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110097","url":null,"abstract":"<div><div>This study numerically investigates the convective heat transfer characteristics of a rotating heated elliptic cylinder immersed in non-Newtonian power law fluid in an unconfined laminar flow regime. The cylinder rotates at a constant angular velocity while the surrounding fluid flows longitudinally at a uniform velocity, while the cylinder surface is maintained at a higher temperature than the ambient fluid. Investigations are carried out on a wide range of variable parameters, including cylinder aspect ratio (<span><math><mrow><mn>0</mn><mo>.</mo><mn>1</mn><mo>≤</mo><mi>e</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span>), rotational speed (<span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>α</mi><mo>≤</mo><mn>2</mn><mo>.</mo><mn>0</mn></mrow></math></span>), Reynolds number (<span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>5</mn><mo>,</mo><mn>10</mn><mo>,</mo><mn>20</mn></mrow></math></span> and 40), Prandtl number (<span><math><mrow><mn>1</mn><mo>≤</mo><mi>P</mi><mi>r</mi><mo>≤</mo><mn>100</mn></mrow></math></span>), and power law index (<span><math><mrow><mn>0</mn><mo>.</mo><mn>4</mn><mo>≤</mo><mi>n</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>6</mn></mrow></math></span>). The results show that the heat transfer rate, represented by local and average Nusselt numbers (<span><math><mrow><mi>N</mi><mi>u</mi></mrow></math></span>), is highly responsive to these parameters. The surface averaged Nusselt numbers exhibit periodic variation with angular rotation of the cylinder, with the amplitude significantly influenced by <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>, <span><math><mi>n</mi></math></span>, <span><math><mi>α</mi></math></span>, and <span><math><mi>e</mi></math></span>. Rotating elliptical cylinders consistently outperform circular cylinders in enhancing heat transfer, particularly in shear-thinning fluids and at higher values of <span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span> and <span><math><mrow><mi>P</mi><mi>r</mi></mrow></math></span>. The isotherm patterns further illustrate the effects of shape, rotation, and fluid behavior on thermal boundary layer characteristics. The results indicate that shear-thinning fluids (<span><math><mrow><mi>n</mi><mo><</mo><mn>1</mn></mrow></math></span>) provide up to 25% higher heat transfer compared to Newtonian fluids. Cylinder rotation further augments convection, yielding about 30% improvement in heat transfer at higher rotation rates. At the end of the report, correlations were established for average Nusselt numbers were established to facilitate result interpolation for intermediate values of <span><math><mrow><mi>e</mi><mo>,</mo><mi>α</mi><mo>,</mo></mrow></math></span>Re<span><math><mrow><mo>,</mo><mi>P</mi><mi>r</mi><mo>,</mo></mrow></math></span> and <span><math><mi>n</mi></math></span> and/or the estimation of changes in heat transfer in a new application.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110097"},"PeriodicalIF":2.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145747167","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}
Pub Date : 2025-10-21DOI: 10.1016/j.ijheatfluidflow.2025.110098
Jian Cao, Sen Li, Chuangxin He, Peng Wang, Yingzheng Liu
Turbulent scalar transport in annular purging jet issuing from the moving wafer stage of lithography machine are investigated through numerical simulations in the moving reference frame. As the jet and moving velocities vary, three distinct flow patterns are identified: crossflow-dominated, purging-dominated, and transitional. The annular jet protects the inner region, which is the focus of analysis. To capture the most intense jet–crossflow interactions, the study examines the central plane as a representative slice of the three-dimensional flow. Coherent structures of velocity and scalar fluctuations are extracted using spectral proper orthogonal decomposition (SPOD) to elucidate the relationship between flow dynamics and passive scalar transport. As the flow transitions from crossflow-dominated to purging-dominated patterns, unstable modes on the leeward side are suppressed while new modes emerge within the inner region. At low and moderate frequencies, velocity and scalar modes exhibit distinct large-scale dynamics, whereas at high frequencies, both share similar shear-layer wavepackets associated with Kelvin–Helmholtz instabilities. Leading scalar modes, which carry most of the fluctuation energy, are used to reconstruct instantaneous scalar fields and visualize dominant mixing structures. Shielding effectiveness is evaluated using scalar-based metrics and jet deflection behaviors, which are characterized by the deflection modulus. As the deflection modulus increases, both windward and leeward deflection angles grow but eventually saturate in the purging-dominated regime. The local momentum ratio along the windward trajectory reflects the varying rigidity of the jet across different flow patterns, while trends in scalar concentration and gradient distributions indicate improvements in shielding performance. Compared to a prior study with a shorter jet development length (H/δ = 5), the present configuration (H/δ = 50) exhibits reduced deflection and diminished shielding effectiveness, attributed to enhanced turbulent entrainment along the extended development region and mixing within the inner region. These findings underscore the challenge of maintaining effective purging in highly turbulent environments.
{"title":"Turbulent scalar transport in annular purging jet issuing from moving wafer stage of lithography machine","authors":"Jian Cao, Sen Li, Chuangxin He, Peng Wang, Yingzheng Liu","doi":"10.1016/j.ijheatfluidflow.2025.110098","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110098","url":null,"abstract":"<div><div>Turbulent scalar transport in annular purging jet issuing from the moving wafer stage of lithography machine are investigated through numerical simulations in the moving reference frame. As the jet and moving velocities vary, three distinct flow patterns are identified: crossflow-dominated, purging-dominated, and transitional. The annular jet protects the inner region, which is the focus of analysis. To capture the most intense jet–crossflow interactions, the study examines the central plane as a representative slice of the three-dimensional flow. Coherent structures of velocity and scalar fluctuations are extracted using spectral proper orthogonal decomposition (SPOD) to elucidate the relationship between flow dynamics and passive scalar transport. As the flow transitions from crossflow-dominated to purging-dominated patterns, unstable modes on the leeward side are suppressed while new modes emerge within the inner region. At low and moderate frequencies, velocity and scalar modes exhibit distinct large-scale dynamics, whereas at high frequencies, both share similar shear-layer wavepackets associated with Kelvin–Helmholtz instabilities. Leading scalar modes, which carry most of the fluctuation energy, are used to reconstruct instantaneous scalar fields and visualize dominant mixing structures. Shielding effectiveness is evaluated using scalar-based metrics and jet deflection behaviors, which are characterized by the deflection modulus. As the deflection modulus increases, both windward and leeward deflection angles grow but eventually saturate in the purging-dominated regime. The local momentum ratio along the windward trajectory reflects the varying rigidity of the jet across different flow patterns, while trends in scalar concentration and gradient distributions indicate improvements in shielding performance. Compared to a prior study with a shorter jet development length (<em>H/δ</em> = 5), the present configuration (<em>H/δ</em> = 50) exhibits reduced deflection and diminished shielding effectiveness, attributed to enhanced turbulent entrainment along the extended development region and mixing within the inner region. These findings underscore the challenge of maintaining effective purging in highly turbulent environments.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110098"},"PeriodicalIF":2.6,"publicationDate":"2025-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145747158","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}
Pub Date : 2025-10-18DOI: 10.1016/j.ijheatfluidflow.2025.110105
Zhonghe Han , Xiaoyu Deng , Chen Li , Hengfan Li , Peng Li
Traditional eccentric straight tube heat exchangers fail to optimize heat storage and release performance simultaneously. This limitation significantly reduces the efficiency of latent heat thermal energy storage systems. To overcome this limitation, this study proposes a novel eccentric helical shell and tube heat exchanger (EHSTHE) designed to enhance both performance. This study evaluates the thermal efficiency of the EHSTHE and traditional heat exchangers through FLUENT simulations, and thoroughly investigates the influence of eccentricity on natural convection. The impacts of geometric/operational parameters, phase change materials, and heat loss on the phase change process are examined. The results demonstrate the superior heat transfer ability of the EHSTHE. For the EHSTHE with 13 mm eccentricity, the melting time is reduced by up to 58.78 %, and the solidification time by 43.18 %. Increased eccentricity promotes vortex formation, intensifying natural convection. The average Nusselt number for the EHSTHE with an eccentricity of 13 mm surpasses those with smaller eccentricities, reaching values of 15.05 and 5.19 during melting and solidification, respectively. Moreover, larger coil diameters and smaller coil pitches reduce phase change duration. Higher inlet temperatures significantly decrease melting time, while lower temperatures accelerate solidification. Compared to inlet temperatures of 348 K (melting) and 308.15 K (solidification), using 358 K and 298.15 K reduces the times by 30.42 % and 27.84 %, respectively. In contrast, the inlet flow rate has a minimal impact. The alteration of the phase change material and the consideration of heat loss do not alter the conclusions of this study.
{"title":"Numerical study on the heat storage and release performance of eccentric helical shell and tube heat exchanger","authors":"Zhonghe Han , Xiaoyu Deng , Chen Li , Hengfan Li , Peng Li","doi":"10.1016/j.ijheatfluidflow.2025.110105","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110105","url":null,"abstract":"<div><div>Traditional eccentric straight tube heat exchangers fail to optimize heat storage and release performance simultaneously. This limitation significantly reduces the efficiency of latent heat thermal energy storage systems. To overcome this limitation, this study proposes a novel eccentric helical shell and tube heat exchanger (EHSTHE) designed to enhance both performance. This study evaluates the thermal efficiency of the EHSTHE and traditional heat exchangers through FLUENT simulations, and thoroughly investigates the influence of eccentricity on natural convection. The impacts of geometric/operational parameters, phase change materials, and heat loss on the phase change process are examined. The results demonstrate the superior heat transfer ability of the EHSTHE. For the EHSTHE with 13 mm eccentricity, the melting time is reduced by up to 58.78 %, and the solidification time by 43.18 %. Increased eccentricity promotes vortex formation, intensifying natural convection. The average Nusselt number for the EHSTHE with an eccentricity of 13 mm surpasses those with smaller eccentricities, reaching values of 15.05 and 5.19 during melting and solidification, respectively. Moreover, larger coil diameters and smaller coil pitches reduce phase change duration. Higher inlet temperatures significantly decrease melting time, while lower temperatures accelerate solidification. Compared to inlet temperatures of 348 K (melting) and 308.15 K (solidification), using 358 K and 298.15 K reduces the times by 30.42 % and 27.84 %, respectively. In contrast, the inlet flow rate has a minimal impact. The alteration of the phase change material and the consideration of heat loss do not alter the conclusions of this study.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110105"},"PeriodicalIF":2.6,"publicationDate":"2025-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145319932","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}
Pub Date : 2025-10-16DOI: 10.1016/j.ijheatfluidflow.2025.110090
Julio C. Vega Ott, Ramón L. Frederick
This work investigates the thermal characteristics of the Graetz problem in a microchannel subjected to an alternating distribution of piecewise constant wall temperatures. The classical microchannel heat transfer problem is extended by integrating viscous dissipation, pressure work, and alternating wall temperature conditions. Rarefied gas effects are accounted for by incorporating slip boundary conditions governed by the Knudsen number, and the Maxwell model is employed to capture the temperature jump at the walls. Piecewise constant wall temperatures are imposed to model alternating hot and cold segments. The energy equation is solved numerically using the finite difference method combined with a marching technique. Finally, the Brinkman number is introduced to examine the influence of viscous dissipation – both with and without pressure work – on the thermal performance of the microchannel.
The results show that rarefaction reduces the efficiency of wall–fluid heat transfer, generating a characteristic sawtooth profile in the bulk temperature and a significant decrease in the Nusselt number under slip conditions. Sectional heating requires more source alternations to achieve convergence as the Knudsen number increases, with the Nusselt number reduced by up to 50% at . Furthermore, including pressure work produces responses opposite to those obtained with viscous dissipation alone, highlighting a mechanism that strongly influences both the bulk temperature and the evolution of the Nusselt number. At high Brinkman numbers, the dominance of the source term drives the asymptotic Nusselt values to approach those reported for the classical constant wall temperature case, regardless of the alternating wall configuration.
{"title":"Laminar forced convective slip flow in a microchannel with piecewise constant temperature in axial direction","authors":"Julio C. Vega Ott, Ramón L. Frederick","doi":"10.1016/j.ijheatfluidflow.2025.110090","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110090","url":null,"abstract":"<div><div>This work investigates the thermal characteristics of the Graetz problem in a microchannel subjected to an alternating distribution of piecewise constant wall temperatures. The classical microchannel heat transfer problem is extended by integrating viscous dissipation, pressure work, and alternating wall temperature conditions. Rarefied gas effects are accounted for by incorporating slip boundary conditions governed by the Knudsen number, and the Maxwell model is employed to capture the temperature jump at the walls. Piecewise constant wall temperatures are imposed to model alternating hot and cold segments. The energy equation is solved numerically using the finite difference method combined with a marching technique. Finally, the Brinkman number is introduced to examine the influence of viscous dissipation – both with and without pressure work – on the thermal performance of the microchannel.</div><div>The results show that rarefaction reduces the efficiency of wall–fluid heat transfer, generating a characteristic sawtooth profile in the bulk temperature and a significant decrease in the Nusselt number under slip conditions. Sectional heating requires more source alternations to achieve convergence as the Knudsen number increases, with the Nusselt number reduced by up to 50% at <span><math><mrow><mi>K</mi><mi>n</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>1</mn></mrow></math></span>. Furthermore, including pressure work produces responses opposite to those obtained with viscous dissipation alone, highlighting a mechanism that strongly influences both the bulk temperature and the evolution of the Nusselt number. At high Brinkman numbers, the dominance of the source term drives the asymptotic Nusselt values to approach those reported for the classical constant wall temperature case, regardless of the alternating wall configuration.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"117 ","pages":"Article 110090"},"PeriodicalIF":2.6,"publicationDate":"2025-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145358679","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}
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