International Journal of Thermofluids最新文献

{"title":"Numerical investigation of windproof-cover geometry effects on NH3–LPG combustion characteristics","authors":"T. Sudjan,&nbsp;A. Kaewpradap","doi":"10.1016/j.ijft.2026.101696","DOIUrl":"10.1016/j.ijft.2026.101696","url":null,"abstract":"<div><div>Replacing carbon-based fuels with carbon-free alternatives in domestic cooking burners is a practical pathway toward decarbonizing household energy use. This study numerically investigates ammonia–liquefied petroleum gas (NH₃-LPG) co-combustion in a conventional KB-5 domestic cooking burner fitted with a windproof cover, using a two-stage CFD methodology with cold-flow mixing, followed by reacting of hot flow in a simulation study at NH₃ fractions of 0%, 50%, and 100%. Twelve windproof cover geometries were evaluated by varying horn diameter, D = 20–30 mm, cover height, H = 15–20 mm, and burner-to-cover distance L = 10–15 mm. The results show that CO₂ emissions decrease monotonically with NH₃ fraction and are eliminated at 100% NH₃, while flame temperature and wall heat flux decrease, relative to pure LPG, owing to ammonia’s lower heating value and slower oxidation kinetics. NOₓ exhibits a non-monotonic trend, peaking near 50–70% NH₃ due to dominant fuel-NOₓ formation before declining at 100% NH₃ as flame temperature falls. Among the twelve configurations, D = 20 mm, H = 20 mm, and L = 10–12.5 mm consistently gave the highest heat flux and most stable thermal field by maximizing internal recirculation and heat retention. These findings indicate that windproof-cover geometry is an effective, low-cost passive lever for partially compensating the thermal penalty of ammonia blending, and they identify the 50–70% NH₃ range as the operating window requiring the most attention to NOₓ control before such burners could be considered for practical low-carbon cooking applications.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101696"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951526","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mechanistic insights of free radical evolution and mechanism of oil from -180°C to 200°C using in-situ electron spin resonance spectroscopy","authors":"Rachid Ismail,&nbsp;Hajra Maqsood,&nbsp;Basim Abu-Jdayil,&nbsp;Joy H. Tannous","doi":"10.1016/j.ijft.2026.101700","DOIUrl":"10.1016/j.ijft.2026.101700","url":null,"abstract":"<div><div>Unconventional oils are difficult to process due to their high viscosity, complex chemistry, and tendency to form coke during upgrading. In this study, in-situ Electron Spin Resonance (ESR) spectroscopy was used to monitor the free radical evolution of a medium-heavy crude oil over a wide temperature range (i.e. −180°C to 200°C). ESR revealed three key regimes: a gradual radical increase of about 147% from 3.0 × 10¹⁶ to 7.5 × 10¹⁶ spins/g between −180°C and −80°C due to trapped radical release; a sharp 323 % rise to 3.2 × 10¹⁷ spins/g between −80°C and 30°C linked to enhanced radical release due to elevated molecular mobility; and a slower increase up to 4.3 × 10¹⁷ spins/g from 30°C to 190°C, nearly 35 %. A sharp decline occurred at 200°C, remaining stable over 50 mins, indicating a balance between radical generation and termination. These findings reveal the critical temperature zones where radical activity transitions, offering insight into free radical reactions as well as coke initiation and pathways to optimize low-severity thermal upgrading of heavy oils. For refinery practice, the identified transition zones can inform temperature selection and process monitoring during low-severity upgrading. Changes in the ESR-derived radical population may provide an early indication of feed instability before substantial coke becomes evident. Translation to process equipment will require validation under continuous-flow and pressurized conditions.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101700"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951622","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical simulation of blood hammer phenomenon in the posterior cerebral artery incorporating visco-hyperelastic wall and complex fluid–structure interaction","authors":"Shervin Alirahimi,&nbsp;Alireza Riasi","doi":"10.1016/j.ijft.2026.101692","DOIUrl":"10.1016/j.ijft.2026.101692","url":null,"abstract":"<div><div>This study numerically investigates the blood hammer phenomenon in an occluded posterior cerebral artery, accounting for fluid–structure interaction between the arterial wall and the blood. The non-Newtonian characteristics of blood—such as shear-thinning and viscoelasticity—are modeled using suitable constitutive equations, while rigid, hyperelastic, or visco-hyperelastic models represent the arterial wall. To examine the impact of different wall rheological models, blood dynamics are primarily described using the five-mode Phan–Thien–Tanner (PTT) viscoelastic model, which captures the complex interaction between blood flow and the arterial wall. For the visco-hyperelastic wall case, alternative constitutive equations for blood are also employed to explore model sensitivity. Key hemodynamic parameters—including velocity profiles, tensile stress distributions, pressure wave histories, and wall shear stresses—are compared across the various combinations of blood and wall models. Results show that when the arterial wall is modeled as visco-hyperelastic, the pressure wave period shortens, and both pressure and wall shear stress histories exhibit the best attenuation. Velocity and tensile stress distributions are also strongly dependent on the wall's rheological properties. When blood is modeled with viscoelastic constitutive equations, attenuation of pressure waves and wall shear stress is weaker compared with viscoplastic or purely shear-thinning models. Under fluid–structure interaction conditions, the maximum wall shear stress predicted by the FENE-P model is reduced by 100%, 43.26%, and 8% relative to the Carreau, Casson, and PTT models, respectively. Hemolysis analysis indicates that red blood cell damage is highest at the arterial midpoint along the wall, rather than at the occlusion site. This effect is most pronounced during the first period of the process, with a peak hemolysis value of 0.954%, indicating a potential health risk.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101692"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geometrically complex double-layer heat exchanger with external and internal fins","authors":"Nahum Y. Godi,&nbsp;Tanimu Jatau,&nbsp;Peter Anthony","doi":"10.1016/j.ijft.2026.101694","DOIUrl":"10.1016/j.ijft.2026.101694","url":null,"abstract":"<div><div>This study presents a novel design featuring cylindrical fins of different heights and diameters inserted inside the cooling channels and on the top surface of the heat sink, aimed at reducing thermal-hydraulic resistance in the substrate volume. Micro-fins are oriented vertically and horizontally, with aspect ratios between 1.2 and 3.6, and are spaced 0.2 mm apart. Cooling is accomplished using water and air operating at Reynolds numbers of 300–500 and 6–14, respectively, within a forced convection laminar regime. The investigation utilizes the finite volume method and computational fluid dynamics (CFD) to model the processes. Numerical results indicate that the configuration with three fins in a upper channel under counter-flow conditions achieves the lowest temperature of 313.97 K, while designs with nine fins in the channel record a temperature of 308 K in the fin domain. Overall thermal resistance reductions of 21% and 15% are achieved in the lower and upper channels, respectively, whereas the fin domain exhibits a reduction of approximately 58% across all configurations studied. The lowest and highest pumping powers of 0.0326 W and 0.0329 W are obtained in the lower and upper channels, respectively, while the highest pumping power in the fin domain reaches 0.00,047 W. In addition, programming analysis shows variability and thermal couplings in the system, revealing a near-perfect correlation between upper and lower channels, indicative of strong internal thermal coupling, while the air stream shows a moderate correlation with both channels. The numerical findings are validated with available experimental and numerical data.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101694"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editorial: Thermofluidic solutions for better sustainability","authors":"İsmail Hilali,&nbsp;Gökhan Demircan","doi":"10.1016/j.ijft.2026.101671","DOIUrl":"10.1016/j.ijft.2026.101671","url":null,"abstract":"","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101671"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148995111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A submesh finite element method for the calculation of view factor","authors":"Daoming Xing,&nbsp;Jianhua Chen,&nbsp;Xiaoqian Shang","doi":"10.1016/j.ijft.2026.101697","DOIUrl":"10.1016/j.ijft.2026.101697","url":null,"abstract":"<div><div>The finite element method (FEM) for view factor calculation is prone to singularities due to the negative power of distance in the integrand. To address this issue, this study proposes a submesh FEM based on triangular mesh subdivision. Two submesh generation methods are developed using the nodes and integral points of triangular elements. The accuracy of the proposed method is validated through two benchmark cases, namely the view factor calculation of two perpendicular unit squares sharing a common edge and the radiative heat transfer in a typical radiant heating room. Parametric studies reveal that the computational performance is simultaneously affected by the submesh generation method, the integration order combination, and the number of subdivision cycles. The proposed method achieves high accuracy in both benchmarks, with a relative error as low as 0.0049% for the view factor calculation and a maximum relative error of 1.04% for the radiative heat transfer rate. The results demonstrate that the proposed submesh FEM effectively resolves the singularity issue of the conventional FEM for view factor calculations in radiative heat transfer.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101697"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Empowering water security: High-efficiency hybrid solar desalination systems","authors":"Mohamed T. Abdelghany,&nbsp;Mehmet Fatih Orhan","doi":"10.1016/j.ijft.2026.101693","DOIUrl":"10.1016/j.ijft.2026.101693","url":null,"abstract":"<div><div>The escalating global freshwater scarcity necessitates highly efficient, decentralized solar distillation solutions that require fundamental innovations to overcome the low productivity inherent in conventional designs. This comprehensive synthesis of research investigates next-generation hybrid active solar still technology, focusing on synergistic modifications across diverse still geometries, including single- and double-slope, conical, and step-type configurations. The core enhancement strategy involves active-hybridization through integration with high-flux solar collectors (Flat Plate, Evacuated Tube, Parabolic Trough) to substantially elevate basin water temperature and maximize the critical temperature differential between the saline water and the condensing cover. To ensure sustained, nocturnal freshwater production, systems strategically incorporate Thermal Energy Storage (TES) via Phase Change Materials (PCMs), such as beeswax or sodium salts. These are frequently augmented with high-conductivity Nanofluids (e.g., Al₂O₃, ZnO–WO₃) and Nano-Enhanced PCMs (NEPCMs) to boost thermal absorption and overall heat transfer capability. Further optimization includes geometric refinements, such as internal copper fins, wick-assisted absorbers, and active glass-cover cooling, to enhance internal heat and mass transfer kinetics. Rigorous experimental validation, supported by comprehensive Energy, Exergy, Economic, and Enviro-economic (4E/5E) analyses, consistently affirms the technological maturity and techno-economic feasibility of these advanced designs. Collective findings robustly report substantial performance gains, including confirmed water productivity increases exceeding 175%–183% and peak exergy efficiencies up to 8.21% compared to baseline stills. Furthermore, competitive economic metrics, with calculated costs of distilled water (CPL) reaching as low as 0.011–0.023 $/L, and validated environmental benefits, substantiate that hybrid active solar still technology offers a viable and sustainable pathway for mitigating water resource challenges, extending the application scope to include the successful distillation of complex wastewater streams like treated dairy effluent.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101693"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951528","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unexplored integration of dimple-protrusion structures in coil wound heat exchangers: a comprehensive numerical assessment","authors":"Arman Shateri,&nbsp;Ali Jahangiri,&nbsp;Sahand Majidi","doi":"10.1016/j.ijft.2026.101695","DOIUrl":"10.1016/j.ijft.2026.101695","url":null,"abstract":"<div><div>Improving the efficiency of heat exchangers is crucial for meeting growing global energy demands, particularly in energy-intensive cryogenic applications such as liquefied natural gas (LNG) production. This work investigates the impact of dimple and protrusion surface features on the thermal-hydraulic performance of Coil Wound Heat Exchangers (CWHEs), vital components in cryogenic applications. Numerical simulations were conducted for methane-ethane mixtures under cryogenic conditions (220 K gas, 130 K liquid), varying flow rates with Reynolds numbers from 1000 to 25,000. The dimple-protrusion geometry significantly enhanced heat transfer, increasing the average Nusselt number by up to 18% for gaseous flow and 12% for liquid flow compared to a smooth tube. While this came with a pressure-drop penalty of up to 21% at peak flow rates, the Performance Evaluation Criterion (PEC) consistently remained above 1.1, indicating a net performance benefit.</div><div>Furthermore, a novel geometry modification applied to the initial two loops of the CWHE increased PEC to 1.17 with a notable 7% reduction in pressure drop. This research uniquely accounts for simultaneous shell-side and tube-side flow dynamics. In addition, a new Nusselt number correlation for these enhanced geometries is presented. These findings offer a pathway for optimizing CWHE design through geometric modifications, promising substantial efficiency gains in industrial-scale cryogenic processes.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101695"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148951621","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Predictive design using physics-informed neural network for the bioconvection of an electrically conducting casson hybrid nanofluid with heat and mass flux model","authors":"Priya Mathur,&nbsp;Amit Kumar Gupta,&nbsp;S.R. Mishra,&nbsp;Hari Mohan Singh","doi":"10.1016/j.ijft.2026.101690","DOIUrl":"10.1016/j.ijft.2026.101690","url":null,"abstract":"<div><div>The development of intelligent computational models for complex bio-thermal transport systems is important for biomedical applications involving controlled heat and mass transfer. The objective of the present study is to develop a physics-informed neural network (PINN)-based predictive framework for analyzing the MHD stagnation-point bioconvective transport of an electrically conducting blood-based Casson hybrid nanofluid. The novelty of this study lies in the unified PINN treatment of MgO–SiO₂–blood hybrid nanofluid transport incorporating motile microorganisms, thermal radiation, viscous dissipation, chemical reaction, and Cattaneo–Christov heat and mass fluxes. The governing PDEs are transformed into a coupled system of nonlinear ODEs through similarity transformations, while the governing physical laws and boundary conditions are embedded directly into the PINN learning process to predict the velocity, temperature, concentration, and microorganism-density fields. The results demonstrate that the magnetic parameter enhances the velocity distribution under the considered stagnation-point flow conditions, whereas thermal radiation elevates the temperature field and chemical reaction suppresses species concentration. Quantitatively, at <span><math><mrow><mi>β</mi><mo>=</mo><mn>3</mn></mrow></math></span> and <span><math><mrow><mi>M</mi><mo>=</mo><mn>0.1</mn></mrow></math></span>, the skin-friction coefficient decreases from <strong>0.64457</strong> for the MgO–blood nanofluid to <strong>0.40608</strong> for the MgO–SiO₂–blood hybrid nanofluid, corresponding to an approximately <strong>37.0% reduction</strong>. Furthermore, the hybrid nanofluid exhibits approximately <strong>56.33% higher Nusselt number</strong> than the MgO–blood nanofluid under the corresponding investigated conditions, demonstrating enhanced heat-transfer performance. The low MSE, MAE, and loss values further demonstrate the predictive capability and stable convergence of the proposed PINN framework.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101690"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148854411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Editorial: Special Issue: New technologies for net zero","authors":"Zaenab Abd-Allah","doi":"10.1016/j.ijft.2026.101670","DOIUrl":"10.1016/j.ijft.2026.101670","url":null,"abstract":"","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"35 ","pages":"Article 101670"},"PeriodicalIF":0.0,"publicationDate":"2026-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148995112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}