Pub Date : 2024-10-14DOI: 10.1016/j.ijheatfluidflow.2024.109598
Amir Eshghinejadfard, Dominique Thévenin
{"title":"Addendum: Numerical simulation of heat transfer in particulate flows using a thermal immersed boundary lattice Boltzmann method","authors":"Amir Eshghinejadfard, Dominique Thévenin","doi":"10.1016/j.ijheatfluidflow.2024.109598","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109598","url":null,"abstract":"","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109598"},"PeriodicalIF":2.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434109","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 : 2024-10-14DOI: 10.1016/j.ijheatfluidflow.2024.109596
S. Rimal , K. Pope , G.F. Naterer , K.A. Hawboldt
This paper investigates the combined effects of radiative heat transfer and chemical reactions on a participating gas–solid flow. A semi-analytical model is developed to investigate the effects of temperature dependent thermophysical properties using a similarity transformation method. It is observed that radiation significantly influences the boundary layer flow during the CuCl2 hydrolysis reaction. Larger radiation parameters and the presence of the chemical reaction led to an increase in the boundary layer thickness. Effects of the chemical reaction on the thermal boundary layer decrease in the presence of radiation. A study of the concentration profile shows that radiation, solid mass fraction, and variable thermophysical properties collectively influence the species concentration distribution near the surface, suggesting enhanced mass transfer and reaction rates. The combined influence of varying thermophysical properties and thermal radiation leads to a reduction in the chemical species concentration near the surface. This occurs from enhanced mass transfer, an increase in the reaction rate, or changes in fluid properties with temperature causing faster diffusion of species away from the boundary. The results offer useful new insights in predicting heat transfer in participating solid–gas flows during the CuCl2 hydrolysis reaction.
{"title":"Effects of chemical reactions and radiation on a participating solid-gas flow with variable thermophysical properties","authors":"S. Rimal , K. Pope , G.F. Naterer , K.A. Hawboldt","doi":"10.1016/j.ijheatfluidflow.2024.109596","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109596","url":null,"abstract":"<div><div>This paper investigates the combined effects of radiative heat transfer and chemical reactions on a participating gas–solid flow. A semi-analytical model is developed to investigate the effects of temperature dependent thermophysical properties using a similarity transformation method. It is observed that radiation significantly influences the boundary layer flow during the CuCl<sub>2</sub> hydrolysis reaction. Larger radiation parameters and the presence of the chemical reaction led to an increase in the boundary layer thickness. Effects of the chemical reaction on the thermal boundary layer decrease in the presence of radiation. A study of the concentration profile shows that radiation, solid mass fraction, and variable thermophysical properties collectively influence the species concentration distribution near the surface, suggesting enhanced mass transfer and reaction rates. The combined influence of varying thermophysical properties and thermal radiation leads to a reduction in the chemical species concentration near the surface. This occurs from enhanced mass transfer, an increase in the reaction rate, or changes in fluid properties with temperature causing faster diffusion of species away from the boundary. The results offer useful new insights in predicting heat transfer in participating solid–gas flows during the CuCl<sub>2</sub> hydrolysis reaction.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109596"},"PeriodicalIF":2.6,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142434107","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 : 2024-10-12DOI: 10.1016/j.ijheatfluidflow.2024.109603
Anxiang Ma , Houjian Zhao , Xiaowei Li , Xinxin Wu
The flow and heat transfer characteristics of turbulent cross flow over tube bundles are very complicated due to the phenomena of boundary layer separation, reattachment and wake disappearance. The method of Partially-Averaged Navier-Stokes (PANS) is considered as the bridge between Direct Numerical Simulation (DNS) and Reynolds-Averaged Navier-Stokes (RANS) and shows good prediction of separated flows with relatively lower computational resources. It may be the best choice to balance the prediction accuracy and computational resources when simulating large scale tube bundles for engineering applications. In current investigation, turbulent cross flows over in-line tube bundles are simulated with PANS method using OpenFOAM. In order to investigate the effects of unresolved-to-total kinetic energy ratio (fk), the flow is simulated with both variable fk and constant fk. The St numbers corresponding to the main frequency for the cases with fk = 0.5, fk = 0.25 and four fk expressions are all 0.1411. For the cases with fk = 0.5, fk = 0.25 and fk expression from Luo et al. (2014), the pressure coefficient and velocity magnitude distribution agree well with the experimental data from Xie et al. (2023). More small-scale structures are resolved as the fk value decreases. The numerical results show that the PANS models are capable to predict turbulent cross flow over in-line tube bundles for engineering applications.
由于边界层分离、重新附着和唤醒消失等现象，管束上湍流交叉流的流动和传热特性非常复杂。部分平均纳维-斯托克斯（PANS）方法被认为是直接数值模拟（DNS）和雷诺平均纳维-斯托克斯（RANS）之间的桥梁，能以相对较低的计算资源对分离流进行良好的预测。在工程应用中模拟大规模管束时，它可能是平衡预测精度和计算资源的最佳选择。在目前的研究中，使用 OpenFOAM 的 PANS 方法模拟了在线管束上的湍流交叉流。为了研究未解决动能与总动能之比（fk）的影响，对流动进行了可变 fk 和恒定 fk 模拟。在 fk = 0.5、fk = 0.25 和四个 fk 表达式的情况下，主频对应的 St 数均为 0.1411。对于 fk = 0.5、fk = 0.25 和来自 Luo 等人（2014 年）的 fk 表达式的情况，压力系数和速度大小分布与 Xie 等人（2023 年）的实验数据非常吻合。随着 fk 值的减小，更多的小尺度结构被解析出来。数值结果表明，PANS 模型能够预测工程应用中在线管束上的湍流横流。
{"title":"An assessment of PANS for simulation of turbulent cross flow over in-line tube bundles","authors":"Anxiang Ma , Houjian Zhao , Xiaowei Li , Xinxin Wu","doi":"10.1016/j.ijheatfluidflow.2024.109603","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109603","url":null,"abstract":"<div><div>The flow and heat transfer characteristics of turbulent cross flow over tube bundles are very complicated due to the phenomena of boundary layer separation, reattachment and wake disappearance. The method of Partially-Averaged Navier-Stokes (PANS) is considered as the bridge between Direct Numerical Simulation (DNS) and Reynolds-Averaged Navier-Stokes (RANS) and shows good prediction of separated flows with relatively lower computational resources. It may be the best choice to balance the prediction accuracy and computational resources when simulating large scale tube bundles for engineering applications. In current investigation, turbulent cross flows over in-line tube bundles are simulated with PANS method using OpenFOAM. In order to investigate the effects of unresolved-to-total kinetic energy ratio (<em>f</em><sub><em>k</em></sub>), the flow is simulated with both variable <em>f</em><sub><em>k</em></sub> and constant <em>f</em><sub><em>k</em>.</sub> The St numbers corresponding to the main frequency for the cases with <em>f</em><sub><em>k</em></sub> = 0.5, <em>f</em><sub><em>k</em></sub> = 0.25 and four <em>f</em><sub><em>k</em></sub> expressions are all 0.1411. For the cases with <em>f</em><sub><em>k</em></sub> = 0.5, <em>f</em><sub><em>k</em></sub> = 0.25 and <em>f</em><sub><em>k</em></sub> expression from <span><span>Luo et al. (2014)</span></span>, the pressure coefficient and velocity magnitude distribution agree well with the experimental data from <span><span>Xie et al. (2023)</span></span>. More small-scale structures are resolved as the <em>f</em><sub><em>k</em></sub> value decreases. The numerical results show that the PANS models are capable to predict turbulent cross flow over in-line tube bundles for engineering applications.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109603"},"PeriodicalIF":2.6,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426726","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 : 2024-10-11DOI: 10.1016/j.ijheatfluidflow.2024.109587
Hongyi Zou , Qingfei Fu , Lijun Yang , Ruo-Yu Dong
The weakly nonlinear instability of viscoelastic planar liquid sheet subjected to simultaneous linear sinuous and varicose perturbations (i.e., dual-mode) has been studied. In the analysis of temporal instability, we considered the case where both sides of the sheet have an inviscid gas moving at the same velocities. The solutions of second-order interfacial perturbation instability were derived based on the perturbation technique, followed by a parametric study. The impact of different disturbance modes on the instability of the upper and lower interfaces was studied under different initial phase differences. When the linear sinuous and varicose modes start with equal initial amplitudes, the influence of the first harmonic of the sinuous mode is notably significant due to its relatively large amplitude. We also checked the influences from several parameters, like elasticity number, time constant ratio on the instability of the sheet under a fixed gas–liquid velocity difference. The results demonstrate that elasticity number has a non-monotonic dual effect on the instability of the sheet: Within a lower range of elasticity numbers, the instability of the sheet is suppressed; Conversely, the instability is enhanced at higher elasticity numbers. Furthermore, under the condition of maintaining a fixed gas–liquid velocity difference, increasing the gas–liquid velocity ratio leads to a decrease in the maximum linear growth rate of perturbations, thereby suppressing the instability of the sheet. However, it has no significant effect on the amplitude of second-order perturbations and the breakup profile of the sheet.
{"title":"Nonlinear dual-mode instability of viscoelastic planar liquid sheet in two inviscid gas streams of equal velocities","authors":"Hongyi Zou , Qingfei Fu , Lijun Yang , Ruo-Yu Dong","doi":"10.1016/j.ijheatfluidflow.2024.109587","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109587","url":null,"abstract":"<div><div>The weakly nonlinear instability of viscoelastic planar liquid sheet subjected to simultaneous linear sinuous and varicose perturbations (i.e., dual-mode) has been studied. In the analysis of temporal instability, we considered the case where both sides of the sheet have an inviscid gas moving at the same velocities. The solutions of second-order interfacial perturbation instability were derived based on the perturbation technique, followed by a parametric study. The impact of different disturbance modes on the instability of the upper and lower interfaces was studied under different initial phase differences. When the linear sinuous and varicose modes start with equal initial amplitudes, the influence of the first harmonic of the sinuous mode is notably significant due to its relatively large amplitude. We also checked the influences from several parameters, like elasticity number, time constant ratio on the instability of the sheet under a fixed gas–liquid velocity difference. The results demonstrate that elasticity number has a non-monotonic dual effect on the instability of the sheet: Within a lower range of elasticity numbers, the instability of the sheet is suppressed; Conversely, the instability is enhanced at higher elasticity numbers. Furthermore, under the condition of maintaining a fixed gas–liquid velocity difference, increasing the gas–liquid velocity ratio leads to a decrease in the maximum linear growth rate of perturbations, thereby suppressing the instability of the sheet. However, it has no significant effect on the amplitude of second-order perturbations and the breakup profile of the sheet.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109587"},"PeriodicalIF":2.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426736","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}
With the development of nanosurface preparation and nanoscale simulation techniques, the effect of nanostructured surfaces on bubble nucleation and boiling heat transfer capability has received much attention. Many studies have shown that nanostructured surfaces can provide preferential nucleation sites for bubble nucleation and effectively enhance heat transfer, attributing to the increased solid–liquid contact area. However, few studies have systematically compared and assessed the performance of different nanostructured surfaces. The geometric effects and negative impact on heat transfer under certain conditions are still not well understood. In this study, the bubble nucleation process on nanostructured surfaces with different geometries were simulated using molecular dynamics method. The geometric effects of nanostructured surfaces are studied for bubble nucleation and heat transfer enhancement, with mechanisms revealed through surface temperature and energy distribution. The critical roughness factor of nanostructured surfaces with different morphologies is obtained. The critical roughness factor for SCUP is 1.215 and SCOP has the lowest critical roughness factor of 1.062. It can be found that the nanostructured surface will inhibit bubble nucleation and weaken surface heat transfer when the surface roughness factor is less than the critical value. It can delay bubble nucleation time by up to 400 ps and reduce the surface critical heat flux by 6.9 %. We believe that the conclusions of this study can provide some quantitative basis for a more comprehensive understanding of nanostructured surface performance.
{"title":"Geometric effects on boiling heat transfer performance: A molecular dynamics study","authors":"Deyang Gao, Zhiyuan Sun, Jinyu Han, Zhanwei Liu, Chenru Zhao, Hanliang Bo","doi":"10.1016/j.ijheatfluidflow.2024.109599","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109599","url":null,"abstract":"<div><div>With the development of nanosurface preparation and nanoscale simulation techniques, the effect of nanostructured surfaces on bubble nucleation and boiling heat transfer capability has received much attention. Many studies have shown that nanostructured surfaces can provide preferential nucleation sites for bubble nucleation and effectively enhance heat transfer, attributing to the increased solid–liquid contact area. However, few studies have systematically compared and assessed the performance of different nanostructured surfaces. The geometric effects and negative impact on heat transfer under certain conditions are still not well understood. In this study, the bubble nucleation process on nanostructured surfaces with different geometries were simulated using molecular dynamics method. The geometric effects of nanostructured surfaces are studied for bubble nucleation and heat transfer enhancement, with mechanisms revealed through surface temperature and energy distribution. The critical roughness factor of nanostructured surfaces with different morphologies is obtained. The critical roughness factor for SCUP is 1.215 and SCOP has the lowest critical roughness factor of 1.062. It can be found that the nanostructured surface will inhibit bubble nucleation and weaken surface heat transfer when the surface roughness factor is less than the critical value. It can delay bubble nucleation time by up to 400 ps and reduce the surface critical heat flux by 6.9 %. We believe that the conclusions of this study can provide some quantitative basis for a more comprehensive understanding of nanostructured surface performance.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109599"},"PeriodicalIF":2.6,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426727","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 : 2024-10-08DOI: 10.1016/j.ijheatfluidflow.2024.109592
Fucheng Chang , Xiaoyi Wu , Shuai Li , Jiaqi Yang , Jiacheng Lou , Huixiong Li
Vibrations of the heat transfer devices can affect bubble formation and detachment processes, leading to instability at the liquid–vapor interface in convective boiling, thereby impacting heat transfer performance and stability in heat transfer systems. This paper investigates the influence mechanism of mechanical vibration on film boiling using the Volume-of-Fluid and Level Set (VOSET) approach. The impacts of vibration amplitude and frequency on film boiling heat transfer characteristics are comprehensively examined. Parameters such as bubble detachment volume (Vb), detachment time (td), and bubble rise velocity (ub) are analyzed to elucidate the influence mechanism of mechanical vibration on the film boiling heat transfer process. Results show that with increasing frequency, the bubble nucleation site and detachment frequency significantly increase, the wall temperature (Tw) decreases noticeably, and the Nusselt number (Nu) increases. Compared to the non-vibration scenario, the average Nusselt number (Nuavg) increases by 15.1 % at a vibration frequency of 10 Hz. Increasing the amplitude effectively promotes the film boiling heat transfer process, but the enhancement effect gradually diminishes. When the amplitude is 3 mm, Nuavg increases by 26.7 % compared to no vibration. The study further explores the impact of vibration on the instability of the vapor film. Vibration significantly alters the dynamic process of bubble growth and detachment. Increasing the vibration frequency and amplitude can enhance bubble rise speed, but with more complex periodic oscillations as frequency and amplitude increase. Additionally, vibration significantly shortens td, further optimizing heat transfer efficiency. This study uncovers how vibration affects film boiling, offering crucial insights for designing and optimizing heat transfer enhancement techniques.
{"title":"Numerical study on the influence mechanism of vibration on the film boiling heat transfer using the VOSET method","authors":"Fucheng Chang , Xiaoyi Wu , Shuai Li , Jiaqi Yang , Jiacheng Lou , Huixiong Li","doi":"10.1016/j.ijheatfluidflow.2024.109592","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109592","url":null,"abstract":"<div><div>Vibrations of the heat transfer devices can affect bubble formation and detachment processes, leading to instability at the liquid–vapor interface in convective boiling, thereby impacting heat transfer performance and stability in heat transfer systems. This paper investigates the influence mechanism of mechanical vibration on film boiling using the Volume-of-Fluid and Level Set (VOSET) approach. The impacts of vibration amplitude and frequency on film boiling heat transfer characteristics are comprehensively examined. Parameters such as bubble detachment volume (<em>V</em><sub>b</sub>), detachment time (<em>t</em><sub>d</sub>), and bubble rise velocity (<em>u</em><sub>b</sub>) are analyzed to elucidate the influence mechanism of mechanical vibration on the film boiling heat transfer process. Results show that with increasing frequency, the bubble nucleation site and detachment frequency significantly increase, the wall temperature (<em>T</em><sub>w</sub>) decreases noticeably, and the Nusselt number (<em>Nu</em>) increases. Compared to the non-vibration scenario, the average Nusselt number (<em>Nu</em><sub>avg</sub>) increases by 15.1 % at a vibration frequency of 10 Hz. Increasing the amplitude effectively promotes the film boiling heat transfer process, but the enhancement effect gradually diminishes. When the amplitude is 3 mm, <em>Nu</em><sub>avg</sub> increases by 26.7 % compared to no vibration. The study further explores the impact of vibration on the instability of the vapor film. Vibration significantly alters the dynamic process of bubble growth and detachment. Increasing the vibration frequency and amplitude can enhance bubble rise speed, but with more complex periodic oscillations as frequency and amplitude increase. Additionally, vibration significantly shortens <em>t</em><sub>d</sub>, further optimizing heat transfer efficiency. This study uncovers how vibration affects film boiling, offering crucial insights for designing and optimizing heat transfer enhancement techniques.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109592"},"PeriodicalIF":2.6,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426734","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}
Temporally developing thermocapillary convection induced by step laser heating of a thin liquid film has been studied numerically. Computations are performed using the commercial software STAR CCM+ version 2022.1. The liquid film of silicone oil (high Prandtl number fluid) is 60 mm in diameter and 3 mm in thickness. Flow characteristics related to surface velocity and surface temperature have been studied. Validation of the computations is achieved for the surface velocity, the velocity along thickness and the surface temperature through comparison with PIV and IR camera measurements. The laser-beam with a carbon dioxide gas laser (10.4 μm in wavelength) is used for heating. It is found that the temporally developing profile of surface velocity shows two local velocity peaks ( and ) at two radial locations ( and ) respectively. The first peak, , appearing due to the steep temperature gradient generated by laser-beam heating and its radial position, , do not change noticeably with time. On the other hand, the second peak, , travels radially outwards with decreasing magnitude in a self-propelling manner until its radial position, , approaches an asymptotic maximum. Detailed analysis of the coupling among radial temperature gradient, local pressure variation and local convective acceleration near the second peak reveals that hydrothermal mechanisms are responsible for self-propelling travel of . The transient behaviors of both primary and secondary velocity peaks are found to depend on the fluid viscosity and the laser-beam settings.
{"title":"Transient behavior of thermocapillary convection in thin liquid film exposed to step laser heating","authors":"Tiwari Ratnanjali, Ogawa Shuma, Ishimura Misa, Nishino Koichi","doi":"10.1016/j.ijheatfluidflow.2024.109602","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109602","url":null,"abstract":"<div><div>Temporally developing thermocapillary convection induced by step laser heating of a thin liquid film has been studied numerically. Computations are performed using the commercial software STAR CCM+ version 2022.1. The liquid film of silicone oil (high Prandtl number fluid) is 60 mm in diameter and 3 mm in thickness. Flow characteristics related to surface velocity and surface temperature have been studied. Validation of the computations is achieved for the surface velocity, the velocity along thickness and the surface temperature through comparison with PIV and IR camera measurements. The laser-beam with a carbon dioxide gas laser (10.4 μm in wavelength) is used for heating. It is found that the temporally developing profile of surface velocity shows two local velocity peaks (<span><math><msub><mi>u</mi><mrow><mi>S</mi><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mi>u</mi><mrow><mi>S</mi><mn>2</mn></mrow></msub></math></span>) at two radial locations (<span><math><msub><mi>r</mi><mrow><mi>S</mi><mn>1</mn></mrow></msub></math></span> and <span><math><msub><mi>r</mi><mrow><mi>S</mi><mn>2</mn></mrow></msub></math></span>) respectively. The first peak, <span><math><msub><mi>u</mi><mrow><mi>S</mi><mn>1</mn></mrow></msub></math></span>, appearing due to the steep temperature gradient generated by laser-beam heating and its radial position, <span><math><msub><mi>r</mi><mrow><mi>S</mi><mn>1</mn></mrow></msub></math></span>, do not change noticeably with time. On the other hand, the second peak, <span><math><msub><mi>u</mi><mrow><mi>S</mi><mn>2</mn></mrow></msub></math></span>, travels radially outwards with decreasing magnitude in a self-propelling manner until its radial position, <span><math><msub><mi>r</mi><mrow><mi>S</mi><mn>2</mn></mrow></msub></math></span>, approaches an asymptotic maximum. Detailed analysis of the coupling among radial temperature gradient, local pressure variation and local convective acceleration near the second peak reveals that hydrothermal mechanisms are responsible for self-propelling travel of <span><math><msub><mi>u</mi><mrow><mi>S</mi><mn>2</mn></mrow></msub></math></span>. The transient behaviors of both primary and secondary velocity peaks are found to depend on the fluid viscosity and the laser-beam settings.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109602"},"PeriodicalIF":2.6,"publicationDate":"2024-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426735","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 : 2024-10-07DOI: 10.1016/j.ijheatfluidflow.2024.109601
Yong Li , Fanyu Kong , Qiang Gao , Yingchun Zhang , Yu Fu , Jianchun Zhang , Bengt Sunden
To enhance the heat transfer efficiency of a printed circuit heat exchanger (PCHE) under ocean rolling conditions, a fractal structure of the NACA 4822 asymmetric airfoil fins was proposed innovatively. This new configuration features two layers of channels: the upper is dedicated to hot CO2 while the lower is aimed for cold CO2. Notably, the asymmetric airfoil fin structure exhibits a remarkable improvement factor of heat transfer ranging from 1.0 to 3.5, accompanied by a friction factor ratio varying between 0.6 and 1.3, which signifies a dual benefit of reduced pressure drop and augmented heat transfer. Under rigorous analysis of the fractal-structured asymmetric airfoil fins in the PCHE, their performance is evaluated through varying rolling periods and angles. Our findings reveal that a rolling period of 2.0 s outperforms a rolling period of 4.0 s in terms of heat transfer performance. Specifically, at a rolling angle of 30°, the thermal performance soars by approximately 2.0 to 4.7 times, which indicates a positive correlation between a larger rolling angle and enhanced heat transfer. Intriguingly, the influence of the rolling angle on heat transfer performance eclipses that of the rolling period.
{"title":"Thermo-hydraulic performance of SCO2 in PCHE with NACA 4822 asymmetric airfoil fins under ocean rolling conditions","authors":"Yong Li , Fanyu Kong , Qiang Gao , Yingchun Zhang , Yu Fu , Jianchun Zhang , Bengt Sunden","doi":"10.1016/j.ijheatfluidflow.2024.109601","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109601","url":null,"abstract":"<div><div>To enhance the heat transfer efficiency of a printed circuit heat exchanger (PCHE) under ocean rolling conditions, a fractal structure of the NACA 4822 asymmetric airfoil fins was proposed innovatively. This new configuration features two layers of channels: the upper is dedicated to hot CO<sub>2</sub> while the lower is aimed for cold CO<sub>2</sub>. Notably, the asymmetric airfoil fin structure exhibits a remarkable improvement factor of heat transfer ranging from 1.0 to 3.5, accompanied by a friction factor ratio varying between 0.6 and 1.3, which signifies a dual benefit of reduced pressure drop and augmented heat transfer. Under rigorous analysis of the fractal-structured asymmetric airfoil fins in the PCHE, their performance is evaluated through varying rolling periods and angles. Our findings reveal that a rolling period of 2.0 s outperforms a rolling period of 4.0 s in terms of heat transfer performance. Specifically, at a rolling angle of 30°, the thermal performance soars by approximately 2.0 to 4.7 times, which indicates a positive correlation between a larger rolling angle and enhanced heat transfer. Intriguingly, the influence of the rolling angle on heat transfer performance eclipses that of the rolling period.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109601"},"PeriodicalIF":2.6,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426732","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 : 2024-10-07DOI: 10.1016/j.ijheatfluidflow.2024.109595
Mingchao OuYang , Zhongmin Lang , Ximin Xu , Yingjie Kang , Gangqiang Wu , Ruifeng Wang , Yaxiong Wang , Qing Ma , Yongli Wu
Pool boiling represents an efficient method of heat transfer. In this experiment, porous media with microchannels are prepared using the high-temperature sintering method for copper powder. The investigation focuses on the impact of various proportions of free particles dispersed within the microchannels on the heat transfer performance during deionized water pool boiling. The microchannels within the porous media maintain consistent width and depth. The findings reveal enhancements in critical heat flux (CHF) and heat transfer coefficient (HTC). Notably, the heat transfer surface featuring 20 % free particles dispersed within the microchannels (FPPM-20 %) exhibits the most significant strengthening effect. This is evidenced by a reduction of ΔT by 5 °C, an increase in CHF by 192 %, and an increase in HTC by 333 % compared to the polished copper surface. The physical model with the same structure is simulated using ANSYS, yielding results consistent with the experimental findings.
{"title":"Experimental and numerical simulation of the effect of free particles dispersed within microchannels on pool boiling heat transfer","authors":"Mingchao OuYang , Zhongmin Lang , Ximin Xu , Yingjie Kang , Gangqiang Wu , Ruifeng Wang , Yaxiong Wang , Qing Ma , Yongli Wu","doi":"10.1016/j.ijheatfluidflow.2024.109595","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109595","url":null,"abstract":"<div><div>Pool boiling represents an efficient method of heat transfer. In this experiment, porous media with microchannels are prepared using the high-temperature sintering method for copper powder. The investigation focuses on the impact of various proportions of free particles dispersed within the microchannels on the heat transfer performance during deionized water pool boiling. The microchannels within the porous media maintain consistent width and depth. The findings reveal enhancements in critical heat flux (CHF) and heat transfer coefficient (HTC). Notably, the heat transfer surface featuring 20 % free particles dispersed within the microchannels (FPPM-20 %) exhibits the most significant strengthening effect. This is evidenced by a reduction of ΔT by 5 °C, an increase in CHF by 192 %, and an increase in HTC by 333 % compared to the polished copper surface. The physical model with the same structure is simulated using ANSYS, yielding results consistent with the experimental findings.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109595"},"PeriodicalIF":2.6,"publicationDate":"2024-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426733","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 : 2024-10-04DOI: 10.1016/j.ijheatfluidflow.2024.109586
K. Suga, K. Takeda, Y. Amano, Y. Kuwata, M. Kaneda
To describe the aerodynamic and thermal effects in the flow between the slotted stator and rotor of electric motors, we have conducted direct and large eddy simulations using the lattice Boltzmann method. The flow between the stator and rotor is influenced by turbulence and Taylor–Couette (TC) vortices. Axial grooves (slots) are incorporated either on the stationary outer cylinder or the rotating inner cylinder. These groove shapes and numbers are designed based on the groove geometry of drive motors used in commercial electric vehicles. The radius ratio of the TC flow configuration in this study is 0.955, and the simulated bulk Reynolds numbers reach up to 21 000 which corresponds to the Taylor number of . The characteristics of torque and heat transfer are analysed by comparing cases with and without grooves. Regardless of the groove placement, it is suggested that while the grooved surface effects are not significant on torque and heat transfer performance at Taylor numbers , where Taylor vortices are still evident, the effects become pronounced at as the flow transitions to the ultimate regime.
{"title":"Torque and heat transfer characteristics in Taylor–Couette turbulence with an axially grooved cylinder","authors":"K. Suga, K. Takeda, Y. Amano, Y. Kuwata, M. Kaneda","doi":"10.1016/j.ijheatfluidflow.2024.109586","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109586","url":null,"abstract":"<div><div>To describe the aerodynamic and thermal effects in the flow between the slotted stator and rotor of electric motors, we have conducted direct and large eddy simulations using the lattice Boltzmann method. The flow between the stator and rotor is influenced by turbulence and Taylor–Couette (TC) vortices. Axial grooves (slots) are incorporated either on the stationary outer cylinder or the rotating inner cylinder. These groove shapes and numbers are designed based on the groove geometry of drive motors used in commercial electric vehicles. The radius ratio of the TC flow configuration in this study is 0.955, and the simulated bulk Reynolds numbers reach up to 21<!--> <!-->000 which corresponds to the Taylor number of <span><math><mrow><mi>T</mi><mi>a</mi><mo>=</mo><mn>4</mn><mo>.</mo><mn>63</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span>. The characteristics of torque and heat transfer are analysed by comparing cases with and without grooves. Regardless of the groove placement, it is suggested that while the grooved surface effects are not significant on torque and heat transfer performance at Taylor numbers <span><math><mrow><mi>T</mi><mi>a</mi><mo>≤</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>7</mn></mrow></msup></mrow></math></span>, where Taylor vortices are still evident, the effects become pronounced at <span><math><mrow><mi>T</mi><mi>a</mi><mo>≥</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>8</mn></mrow></msup></mrow></math></span> as the flow transitions to the ultimate regime.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109586"},"PeriodicalIF":2.6,"publicationDate":"2024-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426731","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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