Pub Date : 2025-03-06DOI: 10.1016/j.ijheatmasstransfer.2025.126851
A. Cimarelli , A. Fenzi , D. Angeli , E. Stalio
<div><div>The full mathematical representation of natural convection is very complex, as it involves, besides continuity and the equations for the transport of momentum and energy, one state equation for density and three laws for the dependency of the thermophysical parameters on pressure and temperature. In addition it requires the representation of pressure work and viscous dissipation in the energy equation. Most numerical simulations and theoretical studies of natural convection use a simplified model based on the Oberbeck–Boussinesq approximation. With respect to the general formulation, the simplified problem is characterized by a divergence-free velocity field, uses constant thermophysical parameters and neglects viscous dissipation and pressure work. Although the Oberbeck–Boussinesq equations have become a physical case in themselves, in certain flow conditions non-Oberbeck–Boussinesq phenomena are non-negligible thus significantly affecting the flow solution. The aim of the present work is to quantitatively identify the flow conditions that give rise to non-negligible non-Oberbeck–Boussinesq phenomena. We demonstrate that the use of direct numerical simulation data combined with the theoretical framework provided by Gray and Giorgini (1976) represents a sound practice to address this issue. The test-case selected is the Rayleigh–Bénard problem at Ra<span><math><mrow><mo>=</mo><mn>0</mn><mo>.</mo><mn>7</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></math></span> with air as working fluid. Direct numerical simulations carried out using the compressible, variable property formulation and the Oberbeck–Boussinesq approximation highlight that a 5% tolerance on variations of the thermophysical properties of air around the reference state <span><math><mrow><mo>(</mo><msub><mrow><mover><mrow><mi>Θ</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mover><mrow><mi>P</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>)</mo></mrow></math></span> = (30 °C, 1 atm) only marginally affects the statistical values of both global and local quantities. However, this tolerance represents a very stringent condition that for a tank of height <span><math><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>̃</mo></mrow></mover><mo>=</mo><mn>2</mn></mrow></math></span> m filled with air at a reference state <span><math><mrow><mo>(</mo><msub><mrow><mover><mrow><mi>Θ</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mover><mrow><mi>P</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>)</mo></mrow></math></span> = (30 °C, 1 atm) leads to a rather low maximum Rayleigh number of the order of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>10</mn></mrow></msup></mrow></math></span> that can be investigated without considering the influence of non-O
{"title":"Assessment of the Oberbeck–Boussinesq approximation for buoyancy-driven turbulence in air","authors":"A. Cimarelli , A. Fenzi , D. Angeli , E. Stalio","doi":"10.1016/j.ijheatmasstransfer.2025.126851","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126851","url":null,"abstract":"<div><div>The full mathematical representation of natural convection is very complex, as it involves, besides continuity and the equations for the transport of momentum and energy, one state equation for density and three laws for the dependency of the thermophysical parameters on pressure and temperature. In addition it requires the representation of pressure work and viscous dissipation in the energy equation. Most numerical simulations and theoretical studies of natural convection use a simplified model based on the Oberbeck–Boussinesq approximation. With respect to the general formulation, the simplified problem is characterized by a divergence-free velocity field, uses constant thermophysical parameters and neglects viscous dissipation and pressure work. Although the Oberbeck–Boussinesq equations have become a physical case in themselves, in certain flow conditions non-Oberbeck–Boussinesq phenomena are non-negligible thus significantly affecting the flow solution. The aim of the present work is to quantitatively identify the flow conditions that give rise to non-negligible non-Oberbeck–Boussinesq phenomena. We demonstrate that the use of direct numerical simulation data combined with the theoretical framework provided by Gray and Giorgini (1976) represents a sound practice to address this issue. The test-case selected is the Rayleigh–Bénard problem at Ra<span><math><mrow><mo>=</mo><mn>0</mn><mo>.</mo><mn>7</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>6</mn></mrow></msup></mrow></math></span> with air as working fluid. Direct numerical simulations carried out using the compressible, variable property formulation and the Oberbeck–Boussinesq approximation highlight that a 5% tolerance on variations of the thermophysical properties of air around the reference state <span><math><mrow><mo>(</mo><msub><mrow><mover><mrow><mi>Θ</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mover><mrow><mi>P</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>)</mo></mrow></math></span> = (30 °C, 1 atm) only marginally affects the statistical values of both global and local quantities. However, this tolerance represents a very stringent condition that for a tank of height <span><math><mrow><mover><mrow><mi>H</mi></mrow><mrow><mo>̃</mo></mrow></mover><mo>=</mo><mn>2</mn></mrow></math></span> m filled with air at a reference state <span><math><mrow><mo>(</mo><msub><mrow><mover><mrow><mi>Θ</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>,</mo><msub><mrow><mover><mrow><mi>P</mi></mrow><mrow><mo>̃</mo></mrow></mover></mrow><mrow><mn>0</mn></mrow></msub><mo>)</mo></mrow></math></span> = (30 °C, 1 atm) leads to a rather low maximum Rayleigh number of the order of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>10</mn></mrow></msup></mrow></math></span> that can be investigated without considering the influence of non-O","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126851"},"PeriodicalIF":5.0,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143549278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-06DOI: 10.1016/j.ijheatmasstransfer.2025.126867
Sina Tahmooresi, Danial Goodarzi, Abdolmajid Mohammadian, Ioan Nistor
This study investigates the behavior of turbulent horizontal dense jets (THDJs) under varying bottom confinement scenarios using laser-induced fluorescence (LIF) techniques. The experiments aim to extend the current understanding of both mean and turbulent characteristics of these jets as they propagate streamwise up to 75 nozzle diameters () from the nozzle exit. The selected scenarios avoid typical wall jet and Coanda effects, focusing instead on medium and low bottom confinements. A comprehensive study on the concentration fluctuation field was carried out along and across the trajectories for multiple sections. Proper orthogonal decomposition (POD) analysis reveals that buoyancy-induced instabilities in the lower layer impede the formation of helical or axisymmetric structures. It turns out that contribution of turbulence in the most confined case () was more than the rest of the scenarios.
{"title":"LIF measurement of turbulent horizontal dense jets in stagnant ambient","authors":"Sina Tahmooresi, Danial Goodarzi, Abdolmajid Mohammadian, Ioan Nistor","doi":"10.1016/j.ijheatmasstransfer.2025.126867","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126867","url":null,"abstract":"<div><div>This study investigates the behavior of turbulent horizontal dense jets (THDJs) under varying bottom confinement scenarios using laser-induced fluorescence (LIF) techniques. The experiments aim to extend the current understanding of both mean and turbulent characteristics of these jets as they propagate streamwise up to 75 nozzle diameters (<span><math><mrow><mn>75</mn><mi>D</mi></mrow></math></span>) from the nozzle exit. The selected scenarios avoid typical wall jet and Coanda effects, focusing instead on medium and low bottom confinements. A comprehensive study on the concentration fluctuation field was carried out along and across the trajectories for multiple sections. Proper orthogonal decomposition (POD) analysis reveals that buoyancy-induced instabilities in the lower layer impede the formation of helical or axisymmetric structures. It turns out that contribution of turbulence in the most confined case (<span><math><mrow><mi>H</mi><mo>/</mo><mi>D</mi><mo>=</mo><mn>3</mn></mrow></math></span>) was more than the rest of the scenarios.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"244 ","pages":"Article 126867"},"PeriodicalIF":5.0,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143563080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-05DOI: 10.1016/j.ijheatmasstransfer.2025.126900
Mohammadsadegh Pahlavanzadeh, Włodzimierz Wróblewski, Krzysztof Rusin
Momentum diffusion and kinetic energy transfer play crucial roles in turbomachinery. The Tesla turbine is a radial turbine that operates based on energy transfer between the operating flow and corotating disks. It has applications in various energy systems, such as the Organic Rankine Cycle and combined heat and power systems. Design parameters, particularly the nozzle configuration, significantly impact turbine performance. This study investigates two nozzle supply designs: one-to-many, where the nozzle provides fluid to all gaps, and one-to-one, with the individual nozzle for each gap. To minimize computational costs, only a portion of the entire domain is examined, and flow structures and their effects on Tesla turbine performance are analyzed. Large Eddy Simulation (LES) employing the Smagorinsky subgrid-scale model is used for flow simulation, enabling a comparison of flow structures, fluctuations, parameters, and their impact on system performance. The one-to-many configuration demonstrates lower efficiency with considerably higher fluctuations. The main source of these fluctuations is found to be the interaction of the inlet jet with the disk tips. In the one-to-one configuration, the source of the fluctuations is the rotating disks, with a different trend of distribution along the gap compared to the one-to-many configuration.
{"title":"Evaluation of nozzle configuration impact on flow structures and performance in Tesla turbine","authors":"Mohammadsadegh Pahlavanzadeh, Włodzimierz Wróblewski, Krzysztof Rusin","doi":"10.1016/j.ijheatmasstransfer.2025.126900","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126900","url":null,"abstract":"<div><div>Momentum diffusion and kinetic energy transfer play crucial roles in turbomachinery. The Tesla turbine is a radial turbine that operates based on energy transfer between the operating flow and corotating disks. It has applications in various energy systems, such as the Organic Rankine Cycle and combined heat and power systems. Design parameters, particularly the nozzle configuration, significantly impact turbine performance. This study investigates two nozzle supply designs: one-to-many, where the nozzle provides fluid to all gaps, and one-to-one, with the individual nozzle for each gap. To minimize computational costs, only a portion of the entire domain is examined, and flow structures and their effects on Tesla turbine performance are analyzed. Large Eddy Simulation (LES) employing the Smagorinsky subgrid-scale model is used for flow simulation, enabling a comparison of flow structures, fluctuations, parameters, and their impact on system performance. The one-to-many configuration demonstrates lower efficiency with considerably higher fluctuations. The main source of these fluctuations is found to be the interaction of the inlet jet with the disk tips. In the one-to-one configuration, the source of the fluctuations is the rotating disks, with a different trend of distribution along the gap compared to the one-to-many configuration.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126900"},"PeriodicalIF":5.0,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-05DOI: 10.1016/j.ijheatmasstransfer.2025.126903
Liuyang Zhang, Xingsen Mu, Shengqiang Shen, Boyu Wang
In the horizontal-tube falling film evaporators, the overall heat transfer performance is directly affected by the liquid film flow outside the tube. To investigate the flow characteristics of the evaporating falling film outside the tube, a three-dimensional (3-D) two-phase model for falling film flow of water and seawater was developed. The heat transfer and evaporation were considered in this model. The Tanasawa model was applied for simulating the phase transition process. The spatial distribution of the local film thickness (δ) along the circumferential angle (θ) and dimensionless axial distance (L*) was discussed in detail. The effect of spray density (Γ), salinity (S) and spray fluid temperature (Tsf) on the average tangential velocity, local spray density and δ was analyzed within the range of 0.03 ≤ Γ ≤ 0.07 kg/(m·s), 0 ≤ S ≤ 100 g/kg and 323.15 ≤ Tsf ≤ 343.15 K. The results indicates that the impact of Γ, S and Tsf on δ is obviously different in space. The collision of liquid film at L* = 0.5 results in a reflux vortex within the liquid film. When θ is less than 60°, there is a slight decrease in the distribution of δ along L* before a rapid increase with L* due to the secondary collision between the liquid film spreading along L* and the reflux flow. As S increases from 0 to 100 g/kg, the maximum difference of δ in the axial direction decreases by 0.038 mm on average. It indicates that increasing S makes the liquid film more evenly distributed along the axial direction.
{"title":"Numerical study of the effect of liquid flow parameters on the three-dimensional film thickness distribution outside the horizontal tube","authors":"Liuyang Zhang, Xingsen Mu, Shengqiang Shen, Boyu Wang","doi":"10.1016/j.ijheatmasstransfer.2025.126903","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126903","url":null,"abstract":"<div><div>In the horizontal-tube falling film evaporators, the overall heat transfer performance is directly affected by the liquid film flow outside the tube. To investigate the flow characteristics of the evaporating falling film outside the tube, a three-dimensional (3-D) two-phase model for falling film flow of water and seawater was developed. The heat transfer and evaporation were considered in this model. The Tanasawa model was applied for simulating the phase transition process. The spatial distribution of the local film thickness (<em>δ</em>) along the circumferential angle (<em>θ</em>) and dimensionless axial distance (<em>L</em>*) was discussed in detail. The effect of spray density (Γ), salinity (<em>S</em>) and spray fluid temperature (<em>T</em><sub>sf</sub>) on the average tangential velocity, local spray density and <em>δ</em> was analyzed within the range of 0.03 ≤ Γ ≤ 0.07 kg/(m·s), 0 ≤ <em>S</em> ≤ 100 g/kg and 323.15 ≤ <em>T</em><sub>sf</sub> ≤ 343.15 K. The results indicates that the impact of Γ, <em>S</em> and <em>T</em><sub>sf</sub> on <em>δ</em> is obviously different in space. The collision of liquid film at <em>L</em>* = 0.5 results in a reflux vortex within the liquid film. When <em>θ</em> is less than 60<sup>°</sup>, there is a slight decrease in the distribution of <em>δ</em> along <em>L</em>* before a rapid increase with <em>L</em>* due to the secondary collision between the liquid film spreading along <em>L</em>* and the reflux flow. As <em>S</em> increases from 0 to 100 g/kg, the maximum difference of <em>δ</em> in the axial direction decreases by 0.038 mm on average. It indicates that increasing <em>S</em> makes the liquid film more evenly distributed along the axial direction.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126903"},"PeriodicalIF":5.0,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548698","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-04DOI: 10.1016/j.ijheatmasstransfer.2025.126780
VS Suvin , Ean Tat Ooi , Chongmin Song , Sundararajan Natarajan
This paper presents a numerical framework for solving temperature dependent non-linear transient heat conduction problems using the Scaled Boundary Finite Element Method (SBFEM) combined with fixed point iteration. Non-linear terms are interpolated using SBFEM shape functions to capture non-linearity effectively. The flexibility of the proposed method is demonstrated through various discretization techniques, including polygonal meshes, a node relocation technique for inclusions in a non-linear medium, and a moving quadtree meshing technique for complex non-linear problems. The proposed method is validated through three numerical examples, encompassing both steady-state and transient heat conduction problems. Additionally, a moving heat source problem is solved using the moving quadtree meshing technique, and a comparative study is conducted with its linear counterpart. This research showcases the robustness and versatility of the SBFEM framework in addressing complex non-linear heat conduction problems.
{"title":"Temperature-dependent nonlinear transient heat conduction using the scaled boundary finite element method","authors":"VS Suvin , Ean Tat Ooi , Chongmin Song , Sundararajan Natarajan","doi":"10.1016/j.ijheatmasstransfer.2025.126780","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126780","url":null,"abstract":"<div><div>This paper presents a numerical framework for solving temperature dependent non-linear transient heat conduction problems using the Scaled Boundary Finite Element Method (SBFEM) combined with fixed point iteration. Non-linear terms are interpolated using SBFEM shape functions to capture non-linearity effectively. The flexibility of the proposed method is demonstrated through various discretization techniques, including polygonal meshes, a node relocation technique for inclusions in a non-linear medium, and a moving quadtree meshing technique for complex non-linear problems. The proposed method is validated through three numerical examples, encompassing both steady-state and transient heat conduction problems. Additionally, a moving heat source problem is solved using the moving quadtree meshing technique, and a comparative study is conducted with its linear counterpart. This research showcases the robustness and versatility of the SBFEM framework in addressing complex non-linear heat conduction problems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126780"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-04DOI: 10.1016/j.ijheatmasstransfer.2025.126870
Chih-Hsiang Chen, Kentaro Yaji
The demand for high-performance heat sinks has significantly increased with advancements in computing power and the miniaturization of electronic devices. Among the promising solutions, nanofluids have attracted considerable attention due to their superior thermal conductivity. However, designing a flow field that effectively utilizes nanofluids remains a challenge due to the complex interactions between fluid and nanoparticles. In this study, we propose a density-based topology optimization method for microchannel heat sink design using nanofluids. An Eulerian-Eulerian framework is utilized to simulate the behavior of nanofluids, and the optimization problem aims to maximize heat transfer performance under a fixed pressure drop. In numerical examples, we investigate the dependence of the optimized configuration on various parameters and apply the method to the design of a manifold microchannel heat sink. The parametric study reveals that the number of flow branches increases with increasing pressure drop and decreasing particle volume fraction. In the heat sink design, the topology-optimized flow field achieves an 11.4% improvement in heat transfer performance compared to a conventional parallel flow field under identical nanofluid conditions. The numerical investigations indicate this improvement increases with higher pressure drops and volumetric heat generation rates.
{"title":"Topology optimization for microchannel heat sinks with nanofluids using an Eulerian-Eulerian approach","authors":"Chih-Hsiang Chen, Kentaro Yaji","doi":"10.1016/j.ijheatmasstransfer.2025.126870","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126870","url":null,"abstract":"<div><div>The demand for high-performance heat sinks has significantly increased with advancements in computing power and the miniaturization of electronic devices. Among the promising solutions, nanofluids have attracted considerable attention due to their superior thermal conductivity. However, designing a flow field that effectively utilizes nanofluids remains a challenge due to the complex interactions between fluid and nanoparticles. In this study, we propose a density-based topology optimization method for microchannel heat sink design using nanofluids. An Eulerian-Eulerian framework is utilized to simulate the behavior of nanofluids, and the optimization problem aims to maximize heat transfer performance under a fixed pressure drop. In numerical examples, we investigate the dependence of the optimized configuration on various parameters and apply the method to the design of a manifold microchannel heat sink. The parametric study reveals that the number of flow branches increases with increasing pressure drop and decreasing particle volume fraction. In the heat sink design, the topology-optimized flow field achieves an 11.4% improvement in heat transfer performance compared to a conventional parallel flow field under identical nanofluid conditions. The numerical investigations indicate this improvement increases with higher pressure drops and volumetric heat generation rates.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126870"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-04DOI: 10.1016/j.ijheatmasstransfer.2025.126890
Chao Yang , Tong-lu Zeng , Ji-wei Xu , Yue Li , Guo-jun Yu , Hai-bo Huo , Fang Wang
Proton exchange membrane fuel cells (PEMFCs) are a promising hydrogen energy solution for marine applications. However, marine motion induced by waves and wind can significantly affect the gas-water multiphase flow within the channels and membrane, particularly in large cell and stack. In this study, both mathematical modeling and experimental investigations were conducted to analyze multiphase transport and electrochemical reactions under typical marine motion loads. The effects of viscous and inertial on multiphase flow and the associated electrochemical reactions within the channel and membrane were also investigated during periodic marine motion. The results indicated that marine pitch and roll motions significantly influenced multiphase flow in the PEMFC cathode. Inertial forces periodically delayed the movement of oxygen and water, leading to periodic nonuniformity and electrochemical degradation. Current densities of 4550–5000 A/m² under pitch and 4625–5000 A/m² under roll were 3.05 % and 2.28 % lower, respectively, than the 4700–5150 A/m2 observed under stationary conditions. Both experimental and predicted results highlighted the detrimental impact of marine motion loads, particularly pitch, on multiphase transport and electrochemical reactions, with higher current densities exacerbating nonuniformity and causing localized oxygen starvation.
{"title":"Numerical and experimental analysis of effects of marine motions on multiphysics transport processes and electrochemical reactions in proton exchange membrane fuel cell","authors":"Chao Yang , Tong-lu Zeng , Ji-wei Xu , Yue Li , Guo-jun Yu , Hai-bo Huo , Fang Wang","doi":"10.1016/j.ijheatmasstransfer.2025.126890","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126890","url":null,"abstract":"<div><div>Proton exchange membrane fuel cells (PEMFCs) are a promising hydrogen energy solution for marine applications. However, marine motion induced by waves and wind can significantly affect the gas-water multiphase flow within the channels and membrane, particularly in large cell and stack. In this study, both mathematical modeling and experimental investigations were conducted to analyze multiphase transport and electrochemical reactions under typical marine motion loads. The effects of viscous and inertial on multiphase flow and the associated electrochemical reactions within the channel and membrane were also investigated during periodic marine motion. The results indicated that marine pitch and roll motions significantly influenced multiphase flow in the PEMFC cathode. Inertial forces periodically delayed the movement of oxygen and water, leading to periodic nonuniformity and electrochemical degradation. Current densities of 4550–5000 A/m² under pitch and 4625–5000 A/m² under roll were 3.05 % and 2.28 % lower, respectively, than the 4700–5150 A/m<sup>2</sup> observed under stationary conditions. Both experimental and predicted results highlighted the detrimental impact of marine motion loads, particularly pitch, on multiphase transport and electrochemical reactions, with higher current densities exacerbating nonuniformity and causing localized oxygen starvation.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126890"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534575","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-04DOI: 10.1016/j.ijheatmasstransfer.2025.126888
Hao Cheng, Dominique Tarlet, Lingai Luo, Yilin Fan
This paper presents the mass transfer behaviors accompanied by chemical reaction under Taylor flow pattern. Experiments were conducted to study the absorption of CO2 into MEA aqueous solution in a vertical straight minichannel with square cross-section of 1.5 mm in width. The velocity field in the liquid slug was characterized using particle tracking velocimetry (PTV), revealing a liquid internal recirculation pattern featuring dual vortex symmetry structure. The recirculation intensity increased with higher two-phase velocities and MEA concentration, and was accurately predicted using a proposed empirical correlation. A pH-sensitive colorimetric method was employed to measure the spatial and temporal distribution of CO2 concentration within the liquid slug. High CO2 concentration zones were observed near bubble caps and channel walls, while low concentration zones were identified in the liquid bulk. Although liquid recirculation motion significantly enhanced axial convection-driven mass transfer, radial mass transfer remained diffusion-dominated. To better account for these phenomena, a modified unit-cell flow and mass transfer model was developed, incorporating the enhancing effects of liquid flow recirculation and chemical reaction. This model enables the determination of local mass transfer coefficients within the liquid slug, offering new insights into the transport mechanisms at the local level.
{"title":"Taylor flow CO2 chemical absorption in a minichannel: Characterization of transport behaviors in the liquid slug and mass transfer modeling","authors":"Hao Cheng, Dominique Tarlet, Lingai Luo, Yilin Fan","doi":"10.1016/j.ijheatmasstransfer.2025.126888","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126888","url":null,"abstract":"<div><div>This paper presents the mass transfer behaviors accompanied by chemical reaction under Taylor flow pattern. Experiments were conducted to study the absorption of CO<sub>2</sub> into MEA aqueous solution in a vertical straight minichannel with square cross-section of 1.5 mm in width. The velocity field in the liquid slug was characterized using particle tracking velocimetry (PTV), revealing a liquid internal recirculation pattern featuring dual vortex symmetry structure. The recirculation intensity increased with higher two-phase velocities and MEA concentration, and was accurately predicted using a proposed empirical correlation. A pH-sensitive colorimetric method was employed to measure the spatial and temporal distribution of CO<sub>2</sub> concentration within the liquid slug. High CO<sub>2</sub> concentration zones were observed near bubble caps and channel walls, while low concentration zones were identified in the liquid bulk. Although liquid recirculation motion significantly enhanced axial convection-driven mass transfer, radial mass transfer remained diffusion-dominated. To better account for these phenomena, a modified unit-cell flow and mass transfer model was developed, incorporating the enhancing effects of liquid flow recirculation and chemical reaction. This model enables the determination of local mass transfer coefficients within the liquid slug, offering new insights into the transport mechanisms at the local level.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126888"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Correctly integrating and planning the use of heat source to provide heat and mass transfer on demand is the key factor to achieving high forming efficiency and high forming accuracy in arc-based directed energy deposition. The Alternating-Arc through Polarity-Switching Self-Adaptive Shunt (PSSAS) method precisely manages current distribution between wire and substrate, effectively decoupling heat and mass transfer. This allows tailored heat input for each deposition layer while maintaining high efficiency. Using in-situ measurements, this study quantifies heat transfer to the substrate and wire, calculates droplet temperature, and captures droplet size via high-speed imaging. Results show that PSSAS transfers anode heat from the substrate to the wire during the electrode negative (EN) phase, reducing substrate heat transfer by 45.9 % to 55.7 %. As EN current increases, substrate heat transfer grows slowly, rising only 41.7 % within 70A to 150A. At the same welding current, wire heat transfer in PSSAS is 31.3 % to 43.9 % higher than in traditional Variable Polarity Plasma Arc (VPPA), indicating superior wire melting efficiency. Overall, PSSAS reduces heat transfer to the substrate by approximately 50 % compared to the traditional VPPA mode, while increasing heat transfer to wire by about 35 %. Further analysis reveals that electromagnetic and plasma flow forces drive droplet transfer in PSSAS, ensuring controlled transfer and good forming quality. PSSAS thus offers decoupled heat and mass transfer with controllable droplet transfer, providing a novel approach for arc-based directed energy deposition.
{"title":"In-situ measurement of heat and mass transfer behavior in alternating-arc through polarity-switching self-adaptive shunt","authors":"Qingsong Hu, Minliang Wang, Zhaoyang Yan, Shujun Chen","doi":"10.1016/j.ijheatmasstransfer.2025.126891","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126891","url":null,"abstract":"<div><div>Correctly integrating and planning the use of heat source to provide heat and mass transfer on demand is the key factor to achieving high forming efficiency and high forming accuracy in arc-based directed energy deposition. The Alternating-Arc through Polarity-Switching Self-Adaptive Shunt (PSSAS) method precisely manages current distribution between wire and substrate, effectively decoupling heat and mass transfer. This allows tailored heat input for each deposition layer while maintaining high efficiency. Using in-situ measurements, this study quantifies heat transfer to the substrate and wire, calculates droplet temperature, and captures droplet size via high-speed imaging. Results show that PSSAS transfers anode heat from the substrate to the wire during the electrode negative (EN) phase, reducing substrate heat transfer by 45.9 % to 55.7 %. As EN current increases, substrate heat transfer grows slowly, rising only 41.7 % within 70A to 150A. At the same welding current, wire heat transfer in PSSAS is 31.3 % to 43.9 % higher than in traditional Variable Polarity Plasma Arc (VPPA), indicating superior wire melting efficiency. Overall, PSSAS reduces heat transfer to the substrate by approximately 50 % compared to the traditional VPPA mode, while increasing heat transfer to wire by about 35 %. Further analysis reveals that electromagnetic and plasma flow forces drive droplet transfer in PSSAS, ensuring controlled transfer and good forming quality. PSSAS thus offers decoupled heat and mass transfer with controllable droplet transfer, providing a novel approach for arc-based directed energy deposition.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126891"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-04DOI: 10.1016/j.ijheatmasstransfer.2025.126897
Haiyan Wu , Bing Bai , Qingke Nie , Xiangxin Jia
Static adsorption-desorption experiments were conducted at four different temperatures, revealing that increasing temperature enhances both adsorption and desorption, with the increment in adsorption being greater than that in desorption. A nonlinear adsorption-desorption model with hysteresis effects was employed to describe the adsorption-desorption processes among multiphase suspended substances, confirming that the adsorption-desorption of suspended particles on the solid-phase matrix at high temperatures follows a nonlinear relationship. Based on SEM, Zeta potential, and DLVO theory calculations, it was found that both increasing temperature and the addition of lead ions reduce the interfacial energy between the red mud and quartz sand surfaces, facilitating better fixation of lead ions within the porous medium. EDX, XRD, FTIR, and XPS experimental results indicate that carbonate ions in red mud can form precipitates with lead ions, exhibiting different chemical reaction characteristics under varying pH conditions. A two-phase flow migration model for contaminant ions and suspended particles was established based on granular thermodynamics. The model's validity and practicality were confirmed through coupled migration experiments of contaminants and suspended particles under different seepage rates and injection concentrations. The simulation results accurately reflect the adsorption-desorption behavior of contaminants and suspended particles during their migration within the solid-phase matrix.
{"title":"The coupled migration model of two-phase flow with nonlinear adsorption-desorption patterns exhibiting delays","authors":"Haiyan Wu , Bing Bai , Qingke Nie , Xiangxin Jia","doi":"10.1016/j.ijheatmasstransfer.2025.126897","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126897","url":null,"abstract":"<div><div>Static adsorption-desorption experiments were conducted at four different temperatures, revealing that increasing temperature enhances both adsorption and desorption, with the increment in adsorption being greater than that in desorption. A nonlinear adsorption-desorption model with hysteresis effects was employed to describe the adsorption-desorption processes among multiphase suspended substances, confirming that the adsorption-desorption of suspended particles on the solid-phase matrix at high temperatures follows a nonlinear relationship. Based on SEM, Zeta potential, and DLVO theory calculations, it was found that both increasing temperature and the addition of lead ions reduce the interfacial energy between the red mud and quartz sand surfaces, facilitating better fixation of lead ions within the porous medium. EDX, XRD, FTIR, and XPS experimental results indicate that carbonate ions in red mud can form precipitates with lead ions, exhibiting different chemical reaction characteristics under varying pH conditions. A two-phase flow migration model for contaminant ions and suspended particles was established based on granular thermodynamics. The model's validity and practicality were confirmed through coupled migration experiments of contaminants and suspended particles under different seepage rates and injection concentrations. The simulation results accurately reflect the adsorption-desorption behavior of contaminants and suspended particles during their migration within the solid-phase matrix.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"243 ","pages":"Article 126897"},"PeriodicalIF":5.0,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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