Pub Date : 2026-01-01DOI: 10.1016/j.ijft.2025.101535
Md. Anonno Habib Akash , Md. Sohag Hossain
To prevent fuel damage and reactor instability, precise detection of boiling and burnout heat flux conditions is essential for nuclear power plant thermal safety. Using high-dimensional acoustic spectrum data acquired from controlled tests at high pressure thermo-physical bench, this paper investigates the use of supervised ML algorithms for the classification of thermal states, including normal boiling and burnout. Each of the 173 samples in the dataset is defined by 200 frequency-domain characteristics. A stratified 5-fold cross-validation pipeline was used to train seven ML models: Multilayer Perceptron, Logistic Regression, Support Vector Machine (RBF kernel), k-Nearest Neighbors, Random Forest, LightGBM, and CatBoost. Hyperparameters were adjusted using RandomizedSearchCV. Model interpretability was assessed with the use of SHAP values, permutation importance, and Gini scores, while feature selection was carried out using ANOVA F-statistics and Recursive Feature Elimination. Random Forest outperformed the other models in terms of test accuracy (88.57 %), recall consistency, and overall performance. Although they were not quite as stable in terms of interpretability, SVM and CatBoost also showed strong classification capabilities with high AUC values (≥ 0.82). The results show that ensemble-based classifiers work well in reactor settings with limited data and running in real-time. In order to provide insights into the performance of the models and their interpretability for safety-critical applications, this study builds a methodology for acoustic-based thermal diagnostics in nuclear systems.
{"title":"Machine learning based classification of boiling and burnout heat flux using acoustic signals in nuclear thermal systems","authors":"Md. Anonno Habib Akash , Md. Sohag Hossain","doi":"10.1016/j.ijft.2025.101535","DOIUrl":"10.1016/j.ijft.2025.101535","url":null,"abstract":"<div><div>To prevent fuel damage and reactor instability, precise detection of boiling and burnout heat flux conditions is essential for nuclear power plant thermal safety. Using high-dimensional acoustic spectrum data acquired from controlled tests at high pressure thermo-physical bench, this paper investigates the use of supervised ML algorithms for the classification of thermal states, including normal boiling and burnout. Each of the 173 samples in the dataset is defined by 200 frequency-domain characteristics. A stratified 5-fold cross-validation pipeline was used to train seven ML models: Multilayer Perceptron, Logistic Regression, Support Vector Machine (RBF kernel), k-Nearest Neighbors, Random Forest, LightGBM, and CatBoost. Hyperparameters were adjusted using RandomizedSearchCV. Model interpretability was assessed with the use of SHAP values, permutation importance, and Gini scores, while feature selection was carried out using ANOVA F-statistics and Recursive Feature Elimination. Random Forest outperformed the other models in terms of test accuracy (88.57 %), recall consistency, and overall performance. Although they were not quite as stable in terms of interpretability, SVM and CatBoost also showed strong classification capabilities with high AUC values (≥ 0.82). The results show that ensemble-based classifiers work well in reactor settings with limited data and running in real-time. In order to provide insights into the performance of the models and their interpretability for safety-critical applications, this study builds a methodology for acoustic-based thermal diagnostics in nuclear systems.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101535"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926537","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.ijft.2025.101542
Torikul Islam , B.M.Jewel Rana , Md.Yousuf Ali , Khan Enaet Hossain , Arnab Mukherjee , Saiful Islam , Mohammad Afikuzzaman
In the evolving field of fluid power and thermal systems, artificial neural networks (ANNs) are increasingly recognized for their robust ability to address nonlinear, coupled, and high-dimensional fluid dynamics problems. This study presents a neural network-assisted investigation of magneto-hydrodynamic Sisko nanofluid flow modelled as a blood-based magnetic suspension over an inclined stretching surface influenced by non-uniform heat generation and thermophoretic effects. The governing partial differential equations derived from mass, momentum, and energy conservation laws with complex boundary conditions are reduced to nonlinear ordinary differential equations through similarity transformations. The resulting system is first solved using MATLAB’s bvp4c solver, and the generated data is then used to train, validate, and test an ANN framework based on the Levenberg Marquardt backpropagation algorithm (BPLMA). The ANN model exhibits high predictive accuracy, with relative absolute errors ranging from 10⁻³ to 10⁻⁷ compared to the reference solution. The thermo-fluidic behaviour of shear-thinning and shear-thickening regimes is analysed under different concentrations of magnetic nanoparticles such as iron oxide and cobalt ferrite. For a 10 percent volume fraction increase, enhancements in heat transfer and reductions in mass transfer are observed, reaching up to 10 percent and 18.9 percent for iron oxide and 9.8 percent and 12 percent for cobalt ferrite, respectively, depending on the fluid rheology. Visualizations of streamlines, temperature fields, and concentration contours reveal intricate flow structures and nanoparticle distributions, offering valuable physical insights. Statistical evaluations including regression analysis, error histograms, and model fitness further support the reliability of the ANN approach. This work introduces a powerful hybrid computational methodology that integrates numerical simulation with machine learning to analyse non-Newtonian nanofluid behaviour and contributes to advancements in biomedical engineering, heat exchanger design, smart cooling systems, and microfluidic devices in fluid power applications. This work presents a novel computational framework that combines traditional numerical simulation with artificial intelligence to analyse complex non-Newtonian nanofluid behaviour. Unlike traditional methods that are often computationally intensive, the ANN model offers fast, accurate predictions and strong generalization across varying conditions. The novelty of this hybrid approach lies in its ability to enhance traditional techniques with AI driven efficiency, making it well suited for applications in biomedical engineering, heat exchanger design, smart cooling systems, and microfluidic devices.
{"title":"Artificial neural network modeling of magnetic nanoparticle-enhanced Sisko blood nanofluid flow over an inclined stretching surface with non-uniform heating and thermophoretic effects","authors":"Torikul Islam , B.M.Jewel Rana , Md.Yousuf Ali , Khan Enaet Hossain , Arnab Mukherjee , Saiful Islam , Mohammad Afikuzzaman","doi":"10.1016/j.ijft.2025.101542","DOIUrl":"10.1016/j.ijft.2025.101542","url":null,"abstract":"<div><div>In the evolving field of fluid power and thermal systems, artificial neural networks (ANNs) are increasingly recognized for their robust ability to address nonlinear, coupled, and high-dimensional fluid dynamics problems. This study presents a neural network-assisted investigation of magneto-hydrodynamic Sisko nanofluid flow modelled as a blood-based magnetic suspension over an inclined stretching surface influenced by non-uniform heat generation and thermophoretic effects. The governing partial differential equations derived from mass, momentum, and energy conservation laws with complex boundary conditions are reduced to nonlinear ordinary differential equations through similarity transformations. The resulting system is first solved using MATLAB’s bvp4c solver, and the generated data is then used to train, validate, and test an ANN framework based on the Levenberg Marquardt backpropagation algorithm (BPLMA). The ANN model exhibits high predictive accuracy, with relative absolute errors ranging from 10⁻³ to 10⁻⁷ compared to the reference solution. The thermo-fluidic behaviour of shear-thinning and shear-thickening regimes is analysed under different concentrations of magnetic nanoparticles such as iron oxide and cobalt ferrite. For a 10 percent volume fraction increase, enhancements in heat transfer and reductions in mass transfer are observed, reaching up to 10 percent and 18.9 percent for iron oxide and 9.8 percent and 12 percent for cobalt ferrite, respectively, depending on the fluid rheology. Visualizations of streamlines, temperature fields, and concentration contours reveal intricate flow structures and nanoparticle distributions, offering valuable physical insights. Statistical evaluations including regression analysis, error histograms, and model fitness further support the reliability of the ANN approach. This work introduces a powerful hybrid computational methodology that integrates numerical simulation with machine learning to analyse non-Newtonian nanofluid behaviour and contributes to advancements in biomedical engineering, heat exchanger design, smart cooling systems, and microfluidic devices in fluid power applications. This work presents a novel computational framework that combines traditional numerical simulation with artificial intelligence to analyse complex non-Newtonian nanofluid behaviour. Unlike traditional methods that are often computationally intensive, the ANN model offers fast, accurate predictions and strong generalization across varying conditions. The novelty of this hybrid approach lies in its ability to enhance traditional techniques with AI driven efficiency, making it well suited for applications in biomedical engineering, heat exchanger design, smart cooling systems, and microfluidic devices.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101542"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.ijft.2025.101541
Mahmmoud M. Syam , Muhammed I. Syam , Kenan Yildirim
This study investigates the unsteady squeezing flow and heat transfer characteristics of a graphene-oxide/water nanofluid confined between two parallel plates undergoing time-dependent motion. A similarity transformation is used to convert the governing nonlinear partial differential equations into a set of coupled boundary-value problems, which are then solved using a modified operational matrix method (OMM). The proposed formulation avoids the stiffness commonly encountered in traditional OMM by introducing a forward-based coefficient computation strategy, reducing computational effort while maintaining high accuracy. The numerical results are validated through truncation error, boundary-condition deviation analysis, and comparison of the local Nusselt number against reference solutions, showing an error on the order of . A detailed parametric investigation is conducted to examine the influence of Brownian motion (), thermophoresis (), squeeze number (S), Eckert number (Ec), and Lewis number (Le) on velocity, temperature, and concentration distributions. The results show that increasing by 0.1 leads to approximately a 6%–12% rise in peak temperature gradients, while higher enhances thermal diffusion and reduces concentration gradients by nearly 8%–15% depending on . The squeeze parameter accelerates the flow and increases the wall shear stress by about 10%, whereas Ec significantly boosts the thermal boundary layer due to viscous dissipation effects. Source terms associated with nanoparticle diffusion, viscous heating, and unsteady squeezing motion play a key role in shaping the overall transport behavior. Overall, the modified OMM offers a fast, stable, and highly accurate alternative for solving nonlinear nanofluid boundary-value problems, and the presented results provide deeper insight into the thermal and mass transport mechanisms of graphene-oxide nanofluids under unsteady squeezing motion.
{"title":"Modeling and simulation of radiative MHD nanofluid flow with Joule heating over a variable-thickness sheet","authors":"Mahmmoud M. Syam , Muhammed I. Syam , Kenan Yildirim","doi":"10.1016/j.ijft.2025.101541","DOIUrl":"10.1016/j.ijft.2025.101541","url":null,"abstract":"<div><div>This study investigates the unsteady squeezing flow and heat transfer characteristics of a graphene-oxide/water nanofluid confined between two parallel plates undergoing time-dependent motion. A similarity transformation is used to convert the governing nonlinear partial differential equations into a set of coupled boundary-value problems, which are then solved using a modified operational matrix method (OMM). The proposed formulation avoids the stiffness commonly encountered in traditional OMM by introducing a forward-based coefficient computation strategy, reducing computational effort while maintaining high accuracy. The numerical results are validated through <span><math><msub><mrow><mi>L</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> truncation error, boundary-condition deviation analysis, and comparison of the local Nusselt number against reference solutions, showing an error on the order of <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>14</mn></mrow></msup></mrow></math></span>. A detailed parametric investigation is conducted to examine the influence of Brownian motion (<span><math><mrow><mi>N</mi><mi>b</mi></mrow></math></span>), thermophoresis (<span><math><mrow><mi>N</mi><mi>t</mi></mrow></math></span>), squeeze number (S), Eckert number (Ec), and Lewis number (Le) on velocity, temperature, and concentration distributions. The results show that increasing <span><math><mrow><mi>N</mi><mi>b</mi></mrow></math></span> by 0.1 leads to approximately a 6%–12% rise in peak temperature gradients, while higher <span><math><mrow><mi>N</mi><mi>t</mi></mrow></math></span> enhances thermal diffusion and reduces concentration gradients by nearly 8%–15% depending on <span><math><mi>ζ</mi></math></span>. The squeeze parameter accelerates the flow and increases the wall shear stress by about 10%, whereas Ec significantly boosts the thermal boundary layer due to viscous dissipation effects. Source terms associated with nanoparticle diffusion, viscous heating, and unsteady squeezing motion play a key role in shaping the overall transport behavior. Overall, the modified OMM offers a fast, stable, and highly accurate alternative for solving nonlinear nanofluid boundary-value problems, and the presented results provide deeper insight into the thermal and mass transport mechanisms of graphene-oxide nanofluids under unsteady squeezing motion.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101541"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-01DOI: 10.1016/j.ijft.2026.101549
Kavana Nagarkar , Shamitha Shetty , Sher Afghan Khan , Abdul Aabid , Muneer Baig
The present numerical study examines hypersonic flow (Mach 5.9) over a blunt body, comparing configurations with and without a forward-facing cavity (FFC). Operating at 1200 Pa and 143 K free-stream conditions, the research focuses on critical parameters, including the drag coefficient, pressure fluctuations, and shock stand-off distance, using unsteady-state RANS simulations. The findings indicate that a forward-facing cavity reduces drag by up to 18% at an L/D ratio of 3. This improvement is attributed to an increased shock stand-off distance, which alters the flow dynamics around the body. The s-a turbulence model with three coefficient equations has satisfied the Navier-Stokes equations to simulate hypervelocity flow over a blunt body. The current time-dependent simulation has provided almost steady results after reaching 11 milliseconds. A comparative analysis of blunt bodies with and without cavities and with varying L/D ratios further demonstrates that deeper cavities enhance performance in hypervelocity conditions.
{"title":"Effects of forward-facing cavity on drag in hypervelocity projectiles: A computational approach","authors":"Kavana Nagarkar , Shamitha Shetty , Sher Afghan Khan , Abdul Aabid , Muneer Baig","doi":"10.1016/j.ijft.2026.101549","DOIUrl":"10.1016/j.ijft.2026.101549","url":null,"abstract":"<div><div>The present numerical study examines hypersonic flow (Mach 5.9) over a blunt body, comparing configurations with and without a forward-facing cavity (FFC). Operating at 1200 Pa and 143 K free-stream conditions, the research focuses on critical parameters, including the drag coefficient, pressure fluctuations, and shock stand-off distance, using unsteady-state RANS simulations. The findings indicate that a forward-facing cavity reduces drag by up to 18% at an L/D ratio of 3. This improvement is attributed to an increased shock stand-off distance, which alters the flow dynamics around the body. The s-a turbulence model with three coefficient equations has satisfied the Navier-Stokes equations to simulate hypervelocity flow over a blunt body. The current time-dependent simulation has provided almost steady results after reaching 11 milliseconds. A comparative analysis of blunt bodies with and without cavities and with varying L/D ratios further demonstrates that deeper cavities enhance performance in hypervelocity conditions.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101549"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-26DOI: 10.1016/j.ijft.2025.101538
Yihui Ma, Nour Mamoun Awad, Ayesha Rashed Saif Rashed Alsalmi, Noor Ahmad Mohammad, Ahad Rashed Saif Alsalmi, Qasem M. Al-Mdallal, S. Saranya
This research addresses the influence of the solid–liquid interface layer on free convection flow and heat transfer of non-Newtonian-based ternary hybrid nanofluids over a rotating vertical cone within a curvilinear coordinate framework. The cone is placed upside down and is uniformly heated while rotating at a constant angular velocity. It is submerged in a ternary hybrid nanofluid of sodium alginate containing nanoparticles. The non-Newtonian Casson fluid model is selected as the base fluid model to study the behavior of fluids. Governing equations for mass, momentum and energy are derived and similarity transformed into a dimensionless form. Using MATLAB's BVP4C solver, the transformed governing nonlinear equations are solved numerically. The study focuses on the impacts of interfacial layer thickness, Casson parameter, magnetic field strength, and nanoparticle concentration on flow and thermal fields. The findings indicate that the thermal conductivity ratio has a more pronounced effect on thermal conductivity than nanoparticle size. The interfacial layer's thickness and its thermal conductivity ratio confirm that it can modulate the velocity and the temperature fields. This study presents a comprehensive imaging approach to thermal systems incorporating non-Newtonian effects, magnetic effects, and interfacial effects for enhanced functional systems.
{"title":"Modeling the role of interfacial layer in free convective axisymmetric MHD flow over a heated rotating cone in non-Newtonian based ternary hybrid nanofluids","authors":"Yihui Ma, Nour Mamoun Awad, Ayesha Rashed Saif Rashed Alsalmi, Noor Ahmad Mohammad, Ahad Rashed Saif Alsalmi, Qasem M. Al-Mdallal, S. Saranya","doi":"10.1016/j.ijft.2025.101538","DOIUrl":"10.1016/j.ijft.2025.101538","url":null,"abstract":"<div><div>This research addresses the influence of the solid–liquid interface layer on free convection flow and heat transfer of non-Newtonian-based ternary hybrid nanofluids over a rotating vertical cone within a curvilinear coordinate framework. The cone is placed upside down and is uniformly heated while rotating at a constant angular velocity. It is submerged in a ternary hybrid nanofluid of sodium alginate containing <span><math><mrow><mi>A</mi><msub><mi>l</mi><mn>2</mn></msub><msub><mi>O</mi><mn>3</mn></msub><mo>,</mo><mspace></mspace><mi>Ti</mi><msub><mi>O</mi><mn>2</mn></msub><mspace></mspace><mtext>and</mtext><mspace></mspace><mi>Si</mi><msub><mi>O</mi><mn>2</mn></msub></mrow></math></span> nanoparticles. The non-Newtonian Casson fluid model is selected as the base fluid model to study the behavior of fluids. Governing equations for mass, momentum and energy are derived and similarity transformed into a dimensionless form. Using MATLAB's BVP4C solver, the transformed governing nonlinear equations are solved numerically. The study focuses on the impacts of interfacial layer thickness, Casson parameter, magnetic field strength, and nanoparticle concentration on flow and thermal fields. The findings indicate that the thermal conductivity ratio has a more pronounced effect on thermal conductivity than nanoparticle size. The interfacial layer's thickness and its thermal conductivity ratio confirm that it can modulate the velocity and the temperature fields. This study presents a comprehensive imaging approach to thermal systems incorporating non-Newtonian effects, magnetic effects, and interfacial effects for enhanced functional systems.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"32 ","pages":"Article 101538"},"PeriodicalIF":0.0,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146078824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-17DOI: 10.1016/j.ijft.2025.101532
Bin Chen, Yutong Lei, Jiayun Ding
The advancement and implementation of low-carbon buildings are crucial for global climate change mitigation and sustainable development. However, conventional single-energy systems often suffer from limited efficiency and high carbon emissions, highlighting the need for integrated and efficient multi-output energy solutions. This study proposes a novel cogeneration system for simultaneous electricity, hydrogen, and heat production based on photovoltaic power generation, with operational parameters for electrolysis and fuel processes determined through parametric analysis. Energy and environmental assessments were conducted to evaluate system performance. The results show that the system achieves a peak solar power output of 125.68 kW/h, an alkaline electrolysis hydrogen production rate of 708.9 mol/h, and a proton exchange membrane fuel cell power generation of 10.3 kW. The overall system efficiency reaches 0.90, representing improvements of 30.19% and 74.77% compared to standalone alkaline electrolysis and fuel cell systems, respectively. Additionally, the system can reduce CO₂ emissions by 352,451 kg annually, demonstrating significant potential for enhancing energy efficiency and supporting decarbonization in the building sector.
{"title":"Energy and environmental analysis of a hydrogen energy cogeneration system based on photovoltaic power generation for low-carbon building","authors":"Bin Chen, Yutong Lei, Jiayun Ding","doi":"10.1016/j.ijft.2025.101532","DOIUrl":"10.1016/j.ijft.2025.101532","url":null,"abstract":"<div><div>The advancement and implementation of low-carbon buildings are crucial for global climate change mitigation and sustainable development. However, conventional single-energy systems often suffer from limited efficiency and high carbon emissions, highlighting the need for integrated and efficient multi-output energy solutions. This study proposes a novel cogeneration system for simultaneous electricity, hydrogen, and heat production based on photovoltaic power generation, with operational parameters for electrolysis and fuel processes determined through parametric analysis. Energy and environmental assessments were conducted to evaluate system performance. The results show that the system achieves a peak solar power output of 125.68 kW/h, an alkaline electrolysis hydrogen production rate of 708.9 mol/h, and a proton exchange membrane fuel cell power generation of 10.3 kW. The overall system efficiency reaches 0.90, representing improvements of 30.19% and 74.77% compared to standalone alkaline electrolysis and fuel cell systems, respectively. Additionally, the system can reduce CO₂ emissions by 352,451 kg annually, demonstrating significant potential for enhancing energy efficiency and supporting decarbonization in the building sector.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"32 ","pages":"Article 101532"},"PeriodicalIF":0.0,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145981467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-12DOI: 10.1016/j.ijft.2025.101531
Irfan Ahmad Sheikh , Emad Elnajjar , Mahmoud Elgendi
Flow control is essential in various engineering applications and environmental contexts to ensure safety, improve efficiency, and enhance overall performance. This study examines the influence of slot configurations at turbulent flow separation points on a circular cylinder and their ability to passively control vortex shedding at a high Reynolds number (Re) = 3.6 × 10⁶. An unsteady Reynolds-Averaged Navier–Stokes (URANS) simulation using a realizable k–ε turbulence model with standard wall treatment was employed to evaluate the aerodynamic behavior of two slot geometries, straight and curved, under identical flow conditions. The results reveal that the introduction of slots substantially modifies the wake structure and aerodynamic loading, increasing the mean drag coefficient from 0.379 for the smooth cylinder to 0.99 and 1.5 for the straight and curved slot configurations, respectively. Similarly, the lift coefficient amplitude increased nearly tenfold, from ±0.1 to approximately ±1 for the curved-slotted cylinder. These findings confirm that slot-induced flow reattachment and momentum exchange enhance vortex coherence and wake stability, providing a robust passive flow-control mechanism. The proposed configuration demonstrates strong potential for integration into bluff-body-based systems such as bladeless wind turbines and tidal energy harvesters, where enhanced lift and controlled drag can improve energy capture efficiency and structural performance.
{"title":"Passive control of turbulent flow around a circular cylinder using slots at separation points","authors":"Irfan Ahmad Sheikh , Emad Elnajjar , Mahmoud Elgendi","doi":"10.1016/j.ijft.2025.101531","DOIUrl":"10.1016/j.ijft.2025.101531","url":null,"abstract":"<div><div>Flow control is essential in various engineering applications and environmental contexts to ensure safety, improve efficiency, and enhance overall performance. This study examines the influence of slot configurations at turbulent flow separation points on a circular cylinder and their ability to passively control vortex shedding at a high Reynolds number (<em>Re</em>) = 3.6 × 10⁶. An unsteady Reynolds-Averaged Navier–Stokes (URANS) simulation using a realizable k–ε turbulence model with standard wall treatment was employed to evaluate the aerodynamic behavior of two slot geometries, straight and curved, under identical flow conditions. The results reveal that the introduction of slots substantially modifies the wake structure and aerodynamic loading, increasing the mean drag coefficient from 0.379 for the smooth cylinder to 0.99 and 1.5 for the straight and curved slot configurations, respectively. Similarly, the lift coefficient amplitude increased nearly tenfold, from ±0.1 to approximately ±1 for the curved-slotted cylinder. These findings confirm that slot-induced flow reattachment and momentum exchange enhance vortex coherence and wake stability, providing a robust passive flow-control mechanism. The proposed configuration demonstrates strong potential for integration into bluff-body-based systems such as bladeless wind turbines and tidal energy harvesters, where enhanced lift and controlled drag can improve energy capture efficiency and structural performance.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101531"},"PeriodicalIF":0.0,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798227","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-11DOI: 10.1016/j.ijft.2025.101522
Praveen Cheekatamarla , Vishaldeep Sharma , Hongbin Sun
The increasing prevalence of counterfeit and incompatible refrigerants presents significant risks to Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R) systems, including compromised equipment performance, safety hazards, and non-compliance. This article details the development of a novel, cost-effective, and portable detection device designed to accurately verify refrigerants. The device utilizes a controlled gas sampling and analysis system within a sealed chamber, ensuring precise measurements while maintaining safety through a purging mechanism. The system features a high-sensitivity sensor integrated with an onboard control module that analyzes gas composition in real-time, providing feedback within a 2-minute duration. Laboratory validation demonstrated the device’s high accuracy (>95 % based on correct identification of compliant vs. non-compliant blends) in detecting unauthorized refrigerant blends. The projected cost of the product stands at ∼ $150, based on the retail pricing of individual components. Laboratory validation demonstrated the device’s high accuracy (>95 % for composition identification, 100 % rejection of tested counterfeit/incorrect blends) in detecting unauthorized refrigerant blends with a response time <2 min. The device correctly identified authentic R-454A/B/C blends and reliably rejected R-407F and closely related counterfeit mixtures. Key advantages include affordability, ease of use, rapid response time, and compatibility with a wide range of refrigerants. This solution supports compliance with regulatory frameworks, enhances safety in HVAC&R operations, and mitigates the risks associated with counterfeit refrigerants.
{"title":"Innovative approach to counterfeit and noncompliant refrigerant detection: A cost-effective, portable solution","authors":"Praveen Cheekatamarla , Vishaldeep Sharma , Hongbin Sun","doi":"10.1016/j.ijft.2025.101522","DOIUrl":"10.1016/j.ijft.2025.101522","url":null,"abstract":"<div><div>The increasing prevalence of counterfeit and incompatible refrigerants presents significant risks to Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R) systems, including compromised equipment performance, safety hazards, and non-compliance. This article details the development of a novel, cost-effective, and portable detection device designed to accurately verify refrigerants. The device utilizes a controlled gas sampling and analysis system within a sealed chamber, ensuring precise measurements while maintaining safety through a purging mechanism. The system features a high-sensitivity sensor integrated with an onboard control module that analyzes gas composition in real-time, providing feedback within a 2-minute duration. Laboratory validation demonstrated the device’s high accuracy (>95 % based on correct identification of compliant vs. non-compliant blends) in detecting unauthorized refrigerant blends. The projected cost of the product stands at ∼ $150, based on the retail pricing of individual components. Laboratory validation demonstrated the device’s high accuracy (>95 % for composition identification, 100 % rejection of tested counterfeit/incorrect blends) in detecting unauthorized refrigerant blends with a response time <2 min. The device correctly identified authentic R-454A/B/C blends and reliably rejected R-407F and closely related counterfeit mixtures. Key advantages include affordability, ease of use, rapid response time, and compatibility with a wide range of refrigerants. This solution supports compliance with regulatory frameworks, enhances safety in HVAC&R operations, and mitigates the risks associated with counterfeit refrigerants.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101522"},"PeriodicalIF":0.0,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-08DOI: 10.1016/j.ijft.2025.101509
Salah Addin Burhan Al-Omari , Farooq Mahmoud , Mohammad Qasem , Zahid Ahmed Qureshi , Emad Elnajjar
This study investigated the conundrum of 2D simplification employability in transient thermal management problems by comparing 2D and 3D numerical simulations of finite-size finned Phase Change Material (PCM) heat sinks. Gallium has been employed as the PCM in the heat sinks owing to its superior thermal response as opposed to conventional paraffinic PCMs. We analyzed two designs; a taller/narrower (Case 2A) and a shorter/wider (Case 1A); both with identical PCM volume, fin material, and heated base dimensions, subjected to a constant 10 W/cm² heat flux. Initial 2D simulations indicated superior heat dissipation for the shorter/wider design. Consistent with this, 3D results corroborated the shorter/wider finned PCM heat sink's superior performance, exhibiting peak base temperatures 10 to 25 K lower than the taller/narrower configuration (Fig. 4a). This advantage is attributed to the strategic PCM allocation in the shorter/wider design, positioning a larger latent heat storage capacity closer to the heat source. Crucially, 3D effects, notably the onset and nature of chaotic mixing, were found to be highly dependent on the applied base boundary conditions. In Case 1A, an unheated base portion created a stabilizing cool region, promoting prolonged near-two-dimensional flow despite emerging 3D effects. Conversely, Case 2A, with its entirely heated base, lacked this stabilization, leading to earlier and more pronounced three-dimensionality and highly chaotic mixing. Quantitatively, these enhanced 3D effects in Case 2A resulted in peak sink base temperatures up to about 10 °C lower than its 2D counterpart (Case 2), alongside faster melting. Despite these significant quantitative deviations, 2D simulations demonstrated qualitative consistency with 3D findings regarding the relative performance ranking of the two designs and the overall PCM melting behavior. These results confirm that while 3D simulations offer a more complete capture of the underlying physics, 2D models remain invaluable for preliminary design purposes, serving as a computationally efficient approach for initial comparative assessments and concept screening before detailed 3D modeling or experimental validation for final design optimization.
{"title":"The conundrum of employability of 2D simplifications in phase change numerical problems: A case of finite sized PCM heat sink","authors":"Salah Addin Burhan Al-Omari , Farooq Mahmoud , Mohammad Qasem , Zahid Ahmed Qureshi , Emad Elnajjar","doi":"10.1016/j.ijft.2025.101509","DOIUrl":"10.1016/j.ijft.2025.101509","url":null,"abstract":"<div><div>This study investigated the conundrum of 2D simplification employability in transient thermal management problems by comparing 2D and 3D numerical simulations of finite-size finned Phase Change Material (PCM) heat sinks. Gallium has been employed as the PCM in the heat sinks owing to its superior thermal response as opposed to conventional paraffinic PCMs. We analyzed two designs; a taller/narrower (Case 2A) and a shorter/wider (Case 1A); both with identical PCM volume, fin material, and heated base dimensions, subjected to a constant 10 W/cm² heat flux. Initial 2D simulations indicated superior heat dissipation for the shorter/wider design. Consistent with this, 3D results corroborated the shorter/wider finned PCM heat sink's superior performance, exhibiting peak base temperatures 10 to 25 K lower than the taller/narrower configuration (Fig. 4a). This advantage is attributed to the strategic PCM allocation in the shorter/wider design, positioning a larger latent heat storage capacity closer to the heat source. Crucially, 3D effects, notably the onset and nature of chaotic mixing, were found to be highly dependent on the applied base boundary conditions. In Case 1A, an unheated base portion created a stabilizing cool region, promoting prolonged near-two-dimensional flow despite emerging 3D effects. Conversely, Case 2A, with its entirely heated base, lacked this stabilization, leading to earlier and more pronounced three-dimensionality and highly chaotic mixing. Quantitatively, these enhanced 3D effects in Case 2A resulted in peak sink base temperatures up to about 10 °C lower than its 2D counterpart (Case 2), alongside faster melting. Despite these significant quantitative deviations, 2D simulations demonstrated qualitative consistency with 3D findings regarding the relative performance ranking of the two designs and the overall PCM melting behavior. These results confirm that while 3D simulations offer a more complete capture of the underlying physics, 2D models remain invaluable for preliminary design purposes, serving as a computationally efficient approach for initial comparative assessments and concept screening before detailed 3D modeling or experimental validation for final design optimization.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"32 ","pages":"Article 101509"},"PeriodicalIF":0.0,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145947972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-07DOI: 10.1016/j.ijft.2025.101516
Ali Rehman , Abdullah Aziz Saad , Mustafa Inc , Siti Sabariah Binti Abas , Edrisa Jawo , K. Sudarmozhi
A base fluid containing a three-component mixture of distinct nanoparticles called a ternary hybrid nanofluid (THNF). In single- or binary-hybrid nanofluids (HNF), these ternary systems exhibit synergistic thermal effects that enhance heat transfer more efficiently. The purpose of this research is to present a semi-numerical simulation and model for analysing the thermal performance of unsteady squeezing flow of a non-Newtonian magneto-hydrodynamic couple-stress THNF confined between 2 parallel surfaces, with the influence of viscous dissipation and heat generation. The THNF, synthesised by dispersing in a non-Newtonian base fluid, was investigated to investigate its superior energy transfer capabilities under complex flow regimes. The key nonlinear PDEs, accounting for squeezing motion, coupling stress effects, magnetic field (MF) interaction, and nanoparticle suspension, are converted into dimensionless nonlinear ODEs via suitable similarity transformations. A semi-numerical approach, the Homotopy analysis method (HAM), combining analytical and numerical schemes, is employed to achieve high-accuracy solutions for velocity and temperature fields. The influence of important parameters, such as the unsteady parameter, the couple stress parameter, the magnetic parameter, the nanoparticle volume fraction, the heat generation parameter, the rotation parameter, and the Eckert number, on the velocity and temperature profiles is observed. The results show that adding ternary hybrid nanoparticles greatly increases thermal conductivity, while the coupling stress and MHD parameters control energy dissipation and flow resistance. For engineering applications such as lubrication systems, extrusion processes, microfluidics, and biomedical devices, the analysis shows that squeezing dynamics and unsteady effects significantly influence energy transfer improvements.
{"title":"Semi-numerical simulation for the thermal performance of unsteady squeezing non-Newtonian MHD couple stress ternary hybrid nanofluid flow between parallel surfaces","authors":"Ali Rehman , Abdullah Aziz Saad , Mustafa Inc , Siti Sabariah Binti Abas , Edrisa Jawo , K. Sudarmozhi","doi":"10.1016/j.ijft.2025.101516","DOIUrl":"10.1016/j.ijft.2025.101516","url":null,"abstract":"<div><div>A base fluid containing a three-component mixture of distinct nanoparticles called a ternary hybrid nanofluid (THNF). In single- or binary-hybrid nanofluids (HNF), these ternary systems exhibit synergistic thermal effects that enhance heat transfer more efficiently. The purpose of this research is to present a semi-numerical simulation and model for analysing the thermal performance of unsteady squeezing flow of a non-Newtonian magneto-hydrodynamic couple-stress THNF confined between 2 parallel surfaces, with the influence of viscous dissipation and heat generation. The THNF, synthesised by dispersing <span><math><mrow><mi>M</mi><mi>W</mi><mi>C</mi><mi>N</mi><mi>T</mi><mo>,</mo><mi>S</mi><mi>W</mi><mi>C</mi><mi>N</mi><mi>T</mi><mo>,</mo><mi>A</mi><mi>g</mi></mrow></math></span>in a non-Newtonian base fluid, was investigated to investigate its superior energy transfer capabilities under complex flow regimes. The key nonlinear PDEs, accounting for squeezing motion, coupling stress effects, magnetic field (MF) interaction, and nanoparticle suspension, are converted into dimensionless nonlinear ODEs via suitable similarity transformations. A semi-numerical approach, the Homotopy analysis method (HAM), combining analytical and numerical schemes, is employed to achieve high-accuracy solutions for velocity and temperature fields. The influence of important parameters, such as the unsteady parameter, the couple stress parameter, the magnetic parameter, the nanoparticle volume fraction, the heat generation parameter, the rotation parameter, and the Eckert number, on the velocity and temperature profiles is observed. The results show that adding ternary hybrid nanoparticles greatly increases thermal conductivity, while the coupling stress and MHD parameters control energy dissipation and flow resistance. For engineering applications such as lubrication systems, extrusion processes, microfluidics, and biomedical devices, the analysis shows that squeezing dynamics and unsteady effects significantly influence energy transfer improvements.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"31 ","pages":"Article 101516"},"PeriodicalIF":0.0,"publicationDate":"2025-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145738202","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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