Pub Date : 2026-01-16DOI: 10.1016/j.ijthermalsci.2026.110695
Xingji Chen , Xuqi Sheng , Daosheng Tang
Thermal spreading in GaN nanostructures is governed by the coupled effects of ballistic-diffusive phonon transport, interfacial mismatch, and mismatch-induced stress, yet these mechanisms are seldom treated in an integrated manner. Here, we develop a unified molecular-dynamics framework, combined with a PSO-based inverse method, to quantify the effective thermal conductivity of GaN under spreading heat flow. We uncover a key finding that the spreading thermal conductivity can exceed that of a single-layer GaN because introducing a heterogeneous interface transforms the bottom boundary from fully absorbing to partially transmitting, allowing ballistic phonons to bypass the dissipation bottleneck. Spreading transport also induces strong anisotropy that differs from 1-D BTE predictions due to multidimensional flux divergence. By introducing stress-relieved reference cases through substrate lattice-constant adjustment, we assess the relative contributions of interfacial structure and mismatch-induced stress, showing that structural mismatch governs GaN/Si, stress dominates GaN/SiC, and both contributions are comparable in GaN/AlN. Vibrational density of states and stress-mapping analyses reveal that interfaces generate nonuniform phonon environments inside GaN, offering an internal mechanism for conductivity reduction. These results clarify interface-modulated thermal transport in GaN and provide guidance for co-optimizing interface structure and strain in high-power GaN devices.
{"title":"Spreading thermal transport in GaN nanostructures: Impact of interface and size induced anisotropy on effective thermal conductivity","authors":"Xingji Chen , Xuqi Sheng , Daosheng Tang","doi":"10.1016/j.ijthermalsci.2026.110695","DOIUrl":"10.1016/j.ijthermalsci.2026.110695","url":null,"abstract":"<div><div>Thermal spreading in GaN nanostructures is governed by the coupled effects of ballistic-diffusive phonon transport, interfacial mismatch, and mismatch-induced stress, yet these mechanisms are seldom treated in an integrated manner. Here, we develop a unified molecular-dynamics framework, combined with a PSO-based inverse method, to quantify the effective thermal conductivity of GaN under spreading heat flow. We uncover a key finding that the spreading thermal conductivity can exceed that of a single-layer GaN because introducing a heterogeneous interface transforms the bottom boundary from fully absorbing to partially transmitting, allowing ballistic phonons to bypass the dissipation bottleneck. Spreading transport also induces strong anisotropy that differs from 1-D BTE predictions due to multidimensional flux divergence. By introducing stress-relieved reference cases through substrate lattice-constant adjustment, we assess the relative contributions of interfacial structure and mismatch-induced stress, showing that structural mismatch governs GaN/Si, stress dominates GaN/SiC, and both contributions are comparable in GaN/AlN. Vibrational density of states and stress-mapping analyses reveal that interfaces generate nonuniform phonon environments inside GaN, offering an internal mechanism for conductivity reduction. These results clarify interface-modulated thermal transport in GaN and provide guidance for co-optimizing interface structure and strain in high-power GaN devices.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110695"},"PeriodicalIF":5.0,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974799","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}
The radiative characteristics of photothermal catalyst particles directly affect the capture and utilization of solar radiation in photothermal chemical reactions. However, mechanisms by how temperature rise affects the radiative characteristics of composite catalyst micro/nanoparticles are neglected. In this study, the temperature-dependent thermal radiative characteristics of the composite CuO/ZnO/Al2O3 (Cu/Zn/Al) catalyst were measured and simulated under multi-temperature conditions. The results indicate that when the temperature is greater than 479 K, the normal reflectance of the Cu/Zn/Al particles for near-infrared waveband beyond 1100 nm increases compared with that at room temperature. The optical constants of the catalyst that determine the absorption and scattering properties of particles are temperature dependent and are reported for reference, with a maximum relative variation of 4.71 %. Elevating temperature increases the extinction cross-section of the particles in the near-infrared region, while also enhancing the interaction in particle clusters. In addition to the enhancement of overall extinction, elevated temperature significantly alters the ratio of the scattering cross-section to the absorption cross-section. When the temperature increases to 563K, the relative increase in the scattering/absorption cross-section ratio for near-infrared radiation is up to 40.03 %, accompanied by an enhancement in backscattering. These results suggest that temperature leads to an increase in the catalyst reflectance of near-infrared waveband. The obtained temperature-dependent radiation characteristics provide a reference for the radiation heat transfer calculation application of the photothermal catalytic system.
{"title":"Temperature-dependent thermal radiative characteristics of micro/nanoparticles for solar photothermal catalysis: experimental and theoretical investigation","authors":"Guijia Zhang, Shiquan Shan, Ziying Cheng, Jialu Tian, Jinhong Yu, Zhijun Zhou, Kefa Cen","doi":"10.1016/j.ijthermalsci.2026.110689","DOIUrl":"10.1016/j.ijthermalsci.2026.110689","url":null,"abstract":"<div><div>The radiative characteristics of photothermal catalyst particles directly affect the capture and utilization of solar radiation in photothermal chemical reactions. However, mechanisms by how temperature rise affects the radiative characteristics of composite catalyst micro/nanoparticles are neglected. In this study, the temperature-dependent thermal radiative characteristics of the composite CuO/ZnO/Al<sub>2</sub>O<sub>3</sub> (Cu/Zn/Al) catalyst were measured and simulated under multi-temperature conditions. The results indicate that when the temperature is greater than 479 K, the normal reflectance of the Cu/Zn/Al particles for near-infrared waveband beyond 1100 nm increases compared with that at room temperature. The optical constants of the catalyst that determine the absorption and scattering properties of particles are temperature dependent and are reported for reference, with a maximum relative variation of 4.71 %. Elevating temperature increases the extinction cross-section of the particles in the near-infrared region, while also enhancing the interaction in particle clusters. In addition to the enhancement of overall extinction, elevated temperature significantly alters the ratio of the scattering cross-section to the absorption cross-section. When the temperature increases to 563K, the relative increase in the scattering/absorption cross-section ratio for near-infrared radiation is up to 40.03 %, accompanied by an enhancement in backscattering. These results suggest that temperature leads to an increase in the catalyst reflectance of near-infrared waveband. The obtained temperature-dependent radiation characteristics provide a reference for the radiation heat transfer calculation application of the photothermal catalytic system.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110689"},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974797","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 : 2026-01-15DOI: 10.1016/j.ijthermalsci.2026.110700
Bin Yin , Shibo Cheng , Xue Chen , Chuang Sun , Haifeng Sun
Flow and heat transfer in a foam-filled channel is investigated by a pore-scale simulation with special concern on the non-ideal joint effect between foam matrix and heating wall. The reticulated foam structures are constructed and represented based on the Weaire-Phelan model. The finite volume method is employed to solve the governing equations of mass, momentum, and energy, thereby determining the conjugate flow and thermal fields for the forced air convection within open-cell foams. The influences of non-contact location, ratio, and distribution regarding the global thermal behavior are systematically investigated. According to the results, non-contact between the foam and the base surface is a primary factor in the performance degradation of metal foam-based heat exchangers. Compared with complete contact, heat transfer is nearly weakened by 92 % under complete non-contact case with a negligible pressure drop change. The wall temperature difference exhibits a visible increment for different non-contact regions, especially at exit region (up to 73.28 K). The non-contact has at entrance region poses the greatest impact on the thermal performance. A significant link is revealed between the extent of non-contact area and the system's thermal performance, which significantly decreases with the increasing non-contact area ratio. The results demonstrate that joint integrity between the foam skeleton and the heating wall is crucial for heat transfer performance in practical engineering applications.
{"title":"Pore-scale analysis of non-ideal joint effect at foam-wall interface on the thermal performance of foam-filled channel","authors":"Bin Yin , Shibo Cheng , Xue Chen , Chuang Sun , Haifeng Sun","doi":"10.1016/j.ijthermalsci.2026.110700","DOIUrl":"10.1016/j.ijthermalsci.2026.110700","url":null,"abstract":"<div><div>Flow and heat transfer in a foam-filled channel is investigated by a pore-scale simulation with special concern on the non-ideal joint effect between foam matrix and heating wall. The reticulated foam structures are constructed and represented based on the Weaire-Phelan model. The finite volume method is employed to solve the governing equations of mass, momentum, and energy, thereby determining the conjugate flow and thermal fields for the forced air convection within open-cell foams. The influences of non-contact location, ratio, and distribution regarding the global thermal behavior are systematically investigated. According to the results, non-contact between the foam and the base surface is a primary factor in the performance degradation of metal foam-based heat exchangers. Compared with complete contact, heat transfer is nearly weakened by 92 % under complete non-contact case with a negligible pressure drop change. The wall temperature difference exhibits a visible increment for different non-contact regions, especially at exit region (up to 73.28 K). The non-contact has at entrance region poses the greatest impact on the thermal performance. A significant link is revealed between the extent of non-contact area and the system's thermal performance, which significantly decreases with the increasing non-contact area ratio. The results demonstrate that joint integrity between the foam skeleton and the heating wall is crucial for heat transfer performance in practical engineering applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110700"},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974800","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 : 2026-01-15DOI: 10.1016/j.ijthermalsci.2026.110698
Qingjun Wang , Yu Chen , Feilong Dou , Yaheng Song , Yufeng Wang
Artificial neural networks are promising for predicting highly nonlinear characteristics of convective heat transfer. Dimensionless and parametric networks are two strategies for supercritical fluid heat transfer prediction, yet their relative accuracy and extrapolation performance with few samples remain unclear. This study obtained a training sample dataset containing 410 sets of data and an extrapolation test dataset containing 940 sets of data of n-decane under supercritical pressure via experiments and calculations. Two corresponding networks were constructed and trained using the sample data, and wall temperature from the dimensionless network was obtained by a surface-intersection method. Results show that in the training sample dataset, both networks show similar errors, while the dimensionless network better captures the characteristics of heat-transfer deterioration. In the extrapolation test dataset, the dimensionless network demonstrates higher accuracy, while the parametric network yields unreasonable predictions in which the predicted wall temperature is lower than the bulk fluid temperature. The reason is that the dimensionless network leverages prior knowledge about the correlation of dimensionless number groups. By directly learning dimensionless variables strongly associated with thermophysical properties, it reduces the degree of nonlinearity in its structure. In contrast, although the parametric network has a simpler structure, it conceals the nonlinear relationships of thermophysical properties and the implicit relationships between wall temperature and other variables. This makes it difficult to extract sufficient information from a small number of samples. This research provides insights into the differences in the extrapolation capability of different artificial neural networks when faced with a limited sample size.
{"title":"Study on the extrapolability of artificial neural network for predicting convective heat transfer of supercritical fluid based on a small number of samples","authors":"Qingjun Wang , Yu Chen , Feilong Dou , Yaheng Song , Yufeng Wang","doi":"10.1016/j.ijthermalsci.2026.110698","DOIUrl":"10.1016/j.ijthermalsci.2026.110698","url":null,"abstract":"<div><div>Artificial neural networks are promising for predicting highly nonlinear characteristics of convective heat transfer. Dimensionless and parametric networks are two strategies for supercritical fluid heat transfer prediction, yet their relative accuracy and extrapolation performance with few samples remain unclear. This study obtained a training sample dataset containing 410 sets of data and an extrapolation test dataset containing 940 sets of data of n-decane under supercritical pressure via experiments and calculations. Two corresponding networks were constructed and trained using the sample data, and wall temperature from the dimensionless network was obtained by a surface-intersection method. Results show that in the training sample dataset, both networks show similar errors, while the dimensionless network better captures the characteristics of heat-transfer deterioration. In the extrapolation test dataset, the dimensionless network demonstrates higher accuracy, while the parametric network yields unreasonable predictions in which the predicted wall temperature is lower than the bulk fluid temperature. The reason is that the dimensionless network leverages prior knowledge about the correlation of dimensionless number groups. By directly learning dimensionless variables strongly associated with thermophysical properties, it reduces the degree of nonlinearity in its structure. In contrast, although the parametric network has a simpler structure, it conceals the nonlinear relationships of thermophysical properties and the implicit relationships between wall temperature and other variables. This makes it difficult to extract sufficient information from a small number of samples. This research provides insights into the differences in the extrapolation capability of different artificial neural networks when faced with a limited sample size.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110698"},"PeriodicalIF":5.0,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974802","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}
As the heat flux of data center chips surpasses 1000 W/cm2, traditional air cooling (limited to 37 W/cm2) and microchannel cooling technologies struggle to meet the efficient heat dissipation demands of next-generation chips due to significant chip temperature differences and thermal stress. While two-phase immersion cooling holds substantial potential, its pool boiling critical heat flux (CHF) and heat transfer coefficient (HTC) require further improvement. To address high-heat-flux chip cooling bottlenecks, this paper proposes synergistically integrating micro heat pipe arrays (MHPA) with immersion phase change cooling (IPCC) to create a staged heat dissipation strategy. A visual experimental system was established using HFE-7100 as the working fluid to systematically investigate boiling heat transfer characteristics and thermal resistance evolution. Experimental results demonstrate that this MHPA-IPCC structure achieves a critical heat flux of 207.6W/cm2, representing a 739.29 % increase over IPCC alone, with a maximum heat transfer coefficient of 4.49 W/(cm2·K), a 219 % improvement, significantly pushing the current limits of heat dissipation. Visual observations revealed the evolution process from natural convection, through nucleate boiling, to film boiling. At a heat flux of 188.3 W/cm2, the system stabilizes hotspot temperature at 103.5 °C; however, film boiling at CHF risks temperature exceedance, necessitating mitigation. Thermal resistance analysis shows that the total thermal resistance (Rt) and MHPA thermal resistance (R2) exhibit a three-stage evolutionary pattern with increasing heat flux: during the low heat flux stage, synergistic working fluid circulation and boiling cause thermal resistance to decrease exponentially; in the medium-to-high heat flux range, the decline becomes linear and gradual; converging to a minimum value (Rt = 0.15 °C/W, R2 = 0.468 °C/W) at the critical condition, where the equivalent thermal conductivity of the MHPA reaches 557 W/(m· K). Compared to existing chip cooling technologies like microchannels and loop heat pipes, this solution demonstrates significant advantages in heat dissipation density, thermal resistance, and heat transfer performance, offering an efficient and reliable thermal management solution for high-power chips.
{"title":"Experimental study on the hotspot cooling performance of immersion chips based on micro heat pipe arrays","authors":"Jiaheng Zhao , Zhenhua Quan , Haibo Ren , Yaohua Zhao","doi":"10.1016/j.ijthermalsci.2026.110694","DOIUrl":"10.1016/j.ijthermalsci.2026.110694","url":null,"abstract":"<div><div>As the heat flux of data center chips surpasses 1000 W/cm<sup>2</sup>, traditional air cooling (limited to 37 W/cm<sup>2</sup>) and microchannel cooling technologies struggle to meet the efficient heat dissipation demands of next-generation chips due to significant chip temperature differences and thermal stress. While two-phase immersion cooling holds substantial potential, its pool boiling critical heat flux (CHF) and heat transfer coefficient (HTC) require further improvement. To address high-heat-flux chip cooling bottlenecks, this paper proposes synergistically integrating micro heat pipe arrays (MHPA) with immersion phase change cooling (IPCC) to create a staged heat dissipation strategy. A visual experimental system was established using HFE-7100 as the working fluid to systematically investigate boiling heat transfer characteristics and thermal resistance evolution. Experimental results demonstrate that this MHPA-IPCC structure achieves a critical heat flux of 207.6W/cm<sup>2</sup>, representing a 739.29 % increase over IPCC alone, with a maximum heat transfer coefficient of 4.49 W/(cm<sup>2</sup>·K), a 219 % improvement, significantly pushing the current limits of heat dissipation. Visual observations revealed the evolution process from natural convection, through nucleate boiling, to film boiling. At a heat flux of 188.3 W/cm<sup>2</sup>, the system stabilizes hotspot temperature at 103.5 °C; however, film boiling at CHF risks temperature exceedance, necessitating mitigation. Thermal resistance analysis shows that the total thermal resistance (<em>R</em><sub><em>t</em></sub>) and MHPA thermal resistance (<em>R</em><sub><em>2</em></sub>) exhibit a three-stage evolutionary pattern with increasing heat flux: during the low heat flux stage, synergistic working fluid circulation and boiling cause thermal resistance to decrease exponentially; in the medium-to-high heat flux range, the decline becomes linear and gradual; converging to a minimum value (<em>R</em><sub><em>t</em></sub> = 0.15 °C/W, <em>R</em><sub><em>2</em></sub> = 0.468 °C/W) at the critical condition, where the equivalent thermal conductivity of the MHPA reaches 557 W/(m· K). Compared to existing chip cooling technologies like microchannels and loop heat pipes, this solution demonstrates significant advantages in heat dissipation density, thermal resistance, and heat transfer performance, offering an efficient and reliable thermal management solution for high-power chips.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110694"},"PeriodicalIF":5.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974803","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}
This study systematically investigates the flow condensation characteristics of the zeotropic mixture R1234ze(E)/R1336mzz(Z) in horizontal smooth tubes through experimental methods. A sapphire-quartz coaxial visualization heat exchanger was developed to enable simultaneous measurement of heat transfer coefficients (HTCs) and flow patterns. Experimental parameters encompassed tube diameters (8 mm and 2 mm), mass fluxes (100–600 kg/(m2·s)), and bubble-point temperatures (75 °C and 85 °C). Results demonstrated that stratified and annular flows dominated in the macro-channel (8 mm), while intermittent and annular flows prevailed in the mini-channel (2 mm). The modified Breber flow pattern map is suitable for zeotropic mixtures. Heat transfer analysis revealed a positive relationship between condensation HTCs and both mass flux and vapor quality, with limited sensitivity to bubble-point temperature variations. In the macro-channel, all models (Shah, Marinheiro, and Cavallini et al. with the Bell and Ghaly and Silver correction) overpredicted HTCs by 120–300 % under non-annular flow conditions, which is attributable to non-negligible thermal resistance induced by concentration gradients. By incorporating an attenuation factor related to vapor-liquid composition differentials (y1−x1) and Bond number (Bo), a modified heat transfer correlation accounting for non-equilibrium effects was proposed, reducing the total mean absolute relative deviation from over 60 % (in non-annular flow) to 12.2 % for macro- and mini-channels. This work provides valuable insights and a reliable tool for the design of compact condensers in high-temperature heat pumps and organic Rankine cycles using zeotropic mixtures.
{"title":"Study on the flow condensation flow patterns and heat transfer characteristics of low-GWP zeotropic mixture R1234ze(E)/R1336mzz(Z) in macro- and mini-channels","authors":"Chunyu Feng, Cong Guo, Junbin Chen, Sicong Tan, Yuyan Jiang","doi":"10.1016/j.ijthermalsci.2026.110665","DOIUrl":"10.1016/j.ijthermalsci.2026.110665","url":null,"abstract":"<div><div>This study systematically investigates the flow condensation characteristics of the zeotropic mixture R1234ze(E)/R1336mzz(Z) in horizontal smooth tubes through experimental methods. A sapphire-quartz coaxial visualization heat exchanger was developed to enable simultaneous measurement of heat transfer coefficients (HTCs) and flow patterns. Experimental parameters encompassed tube diameters (8 mm and 2 mm), mass fluxes (100–600 kg/(m<sup>2</sup>·s)), and bubble-point temperatures (75 °C and 85 °C). Results demonstrated that stratified and annular flows dominated in the macro-channel (8 mm), while intermittent and annular flows prevailed in the mini-channel (2 mm). The modified Breber flow pattern map is suitable for zeotropic mixtures. Heat transfer analysis revealed a positive relationship between condensation HTCs and both mass flux and vapor quality, with limited sensitivity to bubble-point temperature variations. In the macro-channel, all models (Shah, Marinheiro, and Cavallini et al. with the Bell and Ghaly and Silver correction) overpredicted HTCs by 120–300 % under non-annular flow conditions, which is attributable to non-negligible thermal resistance induced by concentration gradients. By incorporating an attenuation factor related to vapor-liquid composition differentials (<em>y</em><sub><em>1</em></sub>−<em>x</em><sub><em>1</em></sub>) and Bond number (Bo), a modified heat transfer correlation accounting for non-equilibrium effects was proposed, reducing the total mean absolute relative deviation from over 60 % (in non-annular flow) to 12.2 % for macro- and mini-channels. This work provides valuable insights and a reliable tool for the design of compact condensers in high-temperature heat pumps and organic Rankine cycles using zeotropic mixtures.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110665"},"PeriodicalIF":5.0,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975201","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}
Shell-and-tube heat exchangers (STHXs) are widely used in industrial thermal systems; however, conventional baffle designs often suffer from high pressure drop, non-uniform shell-side flow distribution, and flow-induced vibration of tube bundles. To address these coupled thermo-hydraulic and dynamic limitations, two bio-inspired baffle configurations—a cobweb-shaped baffle (CWB) and a batwing-shaped baffle (BWB)—are proposed and numerically investigated in comparison with a conventional double-flower baffle (DFB). Three dimensional steady-state simulations are conducted by solving the incompressible continuity, momentum, and energy equations. Turbulence is modeled using the standard k–ε model with standard wall functions, and the near-wall mesh resolution is maintained within the recommended y+ range. Water with temperature-dependent thermophysical properties is employed as the working fluid, while viscous dissipation and thermal radiation are neglected. Flow-induced vibration is evaluated using a one-way fluid-structure interaction (FSI) approach, assuming that tube displacements are sufficiently small to avoid feedback on the flow field. The numerical results indicate that both bio-inspired baffles enhance shell-side heat transfer by inducing geometry-controlled secondary flows and improving flow redistribution. The BWB-STHX achieves a 4.53 % increase in the convective heat transfer coefficient with only a 0.65 % increase in pressure drop, resulting in superior overall thermal-hydraulic performance relative to the DFB configuration. In contrast, the CWB-STHX generates distributed small-scale vortices that improve flow uniformity and reduce the maximum tube-bundle vibration displacement by 19.79 %, while maintaining stable thermal performance. Overall, the proposed bio-inspired baffle designs offer an effective trade-off between heat transfer enhancement, pressure-drop penalty, and vibration mitigation, providing practical guidance for high-performance STHX design.
{"title":"Design and analysis of bionic baffles for coupled thermal and dynamic performance enhancement in shell-and-tube heat exchangers","authors":"Wenpeng Shen , Xiangjiang Xu , Xiancheng Zhang , Peishuo Tang , Wei Song","doi":"10.1016/j.ijthermalsci.2026.110677","DOIUrl":"10.1016/j.ijthermalsci.2026.110677","url":null,"abstract":"<div><div>Shell-and-tube heat exchangers (STHXs) are widely used in industrial thermal systems; however, conventional baffle designs often suffer from high pressure drop, non-uniform shell-side flow distribution, and flow-induced vibration of tube bundles. To address these coupled thermo-hydraulic and dynamic limitations, two bio-inspired baffle configurations—a cobweb-shaped baffle (CWB) and a batwing-shaped baffle (BWB)—are proposed and numerically investigated in comparison with a conventional double-flower baffle (DFB). Three dimensional steady-state simulations are conducted by solving the incompressible continuity, momentum, and energy equations. Turbulence is modeled using the standard <em>k–ε</em> model with standard wall functions, and the near-wall mesh resolution is maintained within the recommended y<sup>+</sup> range. Water with temperature-dependent thermophysical properties is employed as the working fluid, while viscous dissipation and thermal radiation are neglected. Flow-induced vibration is evaluated using a one-way fluid-structure interaction (FSI) approach, assuming that tube displacements are sufficiently small to avoid feedback on the flow field. The numerical results indicate that both bio-inspired baffles enhance shell-side heat transfer by inducing geometry-controlled secondary flows and improving flow redistribution. The BWB-STHX achieves a 4.53 % increase in the convective heat transfer coefficient with only a 0.65 % increase in pressure drop, resulting in superior overall thermal-hydraulic performance relative to the DFB configuration. In contrast, the CWB-STHX generates distributed small-scale vortices that improve flow uniformity and reduce the maximum tube-bundle vibration displacement by 19.79 %, while maintaining stable thermal performance. Overall, the proposed bio-inspired baffle designs offer an effective trade-off between heat transfer enhancement, pressure-drop penalty, and vibration mitigation, providing practical guidance for high-performance STHX design.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110677"},"PeriodicalIF":5.0,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975205","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 : 2026-01-13DOI: 10.1016/j.ijthermalsci.2026.110680
Luka S. Volkov , Yakov V. Miroshnikov , Aleksandr A. Firsov
Rapid mixing of fuel and oxidizer is one of the key conditions for raising the efficiency of combustion chambers with incoming supersonic flow. In this paper, the impact of spark discharges on mixing performance was studied. The mixing was considered for a standard flow configuration: a jet interacting with supersonic crossflow (JISC). The discussed method of mixing enhancement implied placing a repetitive spark discharge near the wall on the windward side of the jet in order to generate disturbances in the jet boundary. To identify the optimal operation modes of the discharge, several series of computer simulations of JISC were performed using the method of unsteady Reynolds-averaged Navier–Stokes equations (URANS). The periodic spark discharge was modeled as a pulsed volumetric heat source. The heat source had several operation modes with different energies and different pulse frequencies, having a fixed average power that was identical for all modes. For each mode, an integral criterion of mixing efficiency was calculated. It was found that the mixing efficiency depends on the discharge frequency non-monotonically. Optimal frequencies were found at which the mixing efficiency reached its maximum. An explanation for the discovered dependence was proposed based on the qualitative analysis of the flow characteristics. The mechanism of JISC instability was described in detail based on the baroclinic term in the vorticity equation for both natural and discharge-induced instabilities.
{"title":"Modeling of jet mixing with supersonic crossflow under the influence of repeated spark discharges","authors":"Luka S. Volkov , Yakov V. Miroshnikov , Aleksandr A. Firsov","doi":"10.1016/j.ijthermalsci.2026.110680","DOIUrl":"10.1016/j.ijthermalsci.2026.110680","url":null,"abstract":"<div><div>Rapid mixing of fuel and oxidizer is one of the key conditions for raising the efficiency of combustion chambers with incoming supersonic flow. In this paper, the impact of spark discharges on mixing performance was studied. The mixing was considered for a standard flow configuration: a jet interacting with supersonic crossflow (JISC). The discussed method of mixing enhancement implied placing a repetitive spark discharge near the wall on the windward side of the jet in order to generate disturbances in the jet boundary. To identify the optimal operation modes of the discharge, several series of computer simulations of JISC were performed using the method of unsteady Reynolds-averaged Navier–Stokes equations (URANS). The periodic spark discharge was modeled as a pulsed volumetric heat source. The heat source had several operation modes with different energies and different pulse frequencies, having a fixed average power that was identical for all modes. For each mode, an integral criterion of mixing efficiency was calculated. It was found that the mixing efficiency depends on the discharge frequency non-monotonically. Optimal frequencies were found at which the mixing efficiency reached its maximum. An explanation for the discovered dependence was proposed based on the qualitative analysis of the flow characteristics. The mechanism of JISC instability was described in detail based on the baroclinic term in the vorticity equation for both natural and discharge-induced instabilities.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110680"},"PeriodicalIF":5.0,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975204","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 : 2026-01-13DOI: 10.1016/j.ijthermalsci.2026.110671
Deng Yang , Chongwen Jiang , Kaidi Wan , Chun-Hian Lee
Gas transport through nanochannels is widespread in both natural and industrial systems and is critical for the design of advanced porous materials. While Knudsen theory is traditionally used to describe this regime, its assumption of fully diffuse reflections fails for graphite-based nanopores, where atomically smooth surfaces promote specular scattering. High-pressure adsorption layers further alter scattering and flow behavior, yet quantitative models that incorporate both effects remain limited. In this study, molecular dynamics simulations are employed to investigate gas transport in graphitic slit nanopores. Gas-solid collisions follow the Cercignani-Lampis-Lord (CLL) model on smooth surfaces, whereas adsorption layers introduce partial diffuse reflection. To quantify the resulting deviations from ideal CLL behavior, we propose a linear-combination scattering framework and develop a semi-empirical tangential momentum accommodation coefficient (TMAC) model. Building upon this framework, new permeability and mass flow rate models are established that incorporate dense gas behavior and confinement effects. Simulation results reveal that the velocity profile within slit nanopores tends toward a plug-like shape, with flow rates enhanced by one to three orders of magnitude compared to no-slip Poiseuille flow. The presence of adsorption layers impedes molecular motion, and the ability of gas molecules to overcome this resistance is directly related to temperature. Compared with conventional models developed for inorganic porous media, the proposed model accurately captures the distinct gas transport behavior along graphitic surfaces. These findings offer valuable guidance for the development and utilization of carbon aerogels and, more broadly, for understanding mass transport in carbon-based nanoporous materials.
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Pub Date : 2026-01-13DOI: 10.1016/j.ijthermalsci.2025.110650
Brajesh Kumar Ahirwar , Arvind Kumar
The growing need for efficient thermal management has spurred extensive research into enhancing heat exchanger performance. Among emerging methods, nanofluids—especially hybrid variants—have shown significant potential due to their superior thermal properties. This study explores the thermal performance of CuO + ZnO-water hybrid nanofluids in a double-pipe heat exchanger (DPHE) equipped with wire coil inserts as a passive enhancement technique. Hybrid nanofluids were prepared using CuO and ZnO nanoparticles at three volume concentrations: 1.0 % (80:20), 0.5 % (60:40), and 0.1 % (40:60). These fluids were tested over a Reynolds number range of 5500–15000 with wire coil inserts of varying diameters (1.0 mm, 1.5 mm, 2.0 mm) and pitch ratios (0.625–3.125). Results demonstrated that the highest heat transfer performance was achieved using 1.0 % CuO: ZnO (80:20) with a 2.0 mm wire diameter and tightest pitch ratio (0.625), yielding a Nusselt number increase of up to 281.87 % over water. While the friction factor also rose—leading to a maximum pressure drop penalty of 600.72 %—the thermal performance factor (TPF) remained favourable, ranging from 1.61 to 1.74. Lower concentrations and alternate compositions showed moderate performance improvements. Empirical correlations for Nusselt number and friction factor were developed, with predictive deviations within ±10 % of experimental values, confirming their reliability. This comprehensive analysis highlights the synergistic benefits of hybrid nanofluids and optimized wire coil geometries, offering valuable insights for the design of high-efficiency, compact heat exchangers in advanced thermal systems.
{"title":"Enhanced heat transfer using CuO+ZnO-water hybrid nanofluid with helical coil inserts in double pipe heat exchanger: Performance analysis and correlation development","authors":"Brajesh Kumar Ahirwar , Arvind Kumar","doi":"10.1016/j.ijthermalsci.2025.110650","DOIUrl":"10.1016/j.ijthermalsci.2025.110650","url":null,"abstract":"<div><div>The growing need for efficient thermal management has spurred extensive research into enhancing heat exchanger performance. Among emerging methods, nanofluids—especially hybrid variants—have shown significant potential due to their superior thermal properties. This study explores the thermal performance of CuO + ZnO-water hybrid nanofluids in a double-pipe heat exchanger (DPHE) equipped with wire coil inserts as a passive enhancement technique. Hybrid nanofluids were prepared using CuO and ZnO nanoparticles at three volume concentrations: 1.0 % (80:20), 0.5 % (60:40), and 0.1 % (40:60). These fluids were tested over a Reynolds number range of 5500–15000 with wire coil inserts of varying diameters (1.0 mm, 1.5 mm, 2.0 mm) and pitch ratios (0.625–3.125). Results demonstrated that the highest heat transfer performance was achieved using 1.0 % CuO: ZnO (80:20) with a 2.0 mm wire diameter and tightest pitch ratio (0.625), yielding a Nusselt number increase of up to 281.87 % over water. While the friction factor also rose—leading to a maximum pressure drop penalty of 600.72 %—the thermal performance factor (TPF) remained favourable, ranging from 1.61 to 1.74. Lower concentrations and alternate compositions showed moderate performance improvements. Empirical correlations for Nusselt number and friction factor were developed, with predictive deviations within ±10 % of experimental values, confirming their reliability. This comprehensive analysis highlights the synergistic benefits of hybrid nanofluids and optimized wire coil geometries, offering valuable insights for the design of high-efficiency, compact heat exchangers in advanced thermal systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110650"},"PeriodicalIF":5.0,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975206","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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