International Journal of Thermal Sciences最新文献

英文中文

Research on mini-channel heat exchangers with honeycomb modular structure: Design principles and convective heat transfer

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-06 DOI: 10.1016/j.ijthermalsci.2025.109832

Zhao-Yuan Wang, Si-Cong Tan, Jia-Min Zhu, Cong Guo, Yu-Yan Jiang

The use of micro/mini channels in heat exchangers can significantly enhance the heat transfer coefficient, reduce equipment size, and lower manufacturing costs. However, challenges such as manufacturing difficulties and scalability limitations remain. To address these issues, this paper proposes a novel assembly structure based on a honeycomb configuration, using modular cores, each containing a bundle of stainless steel tubes with an outer diameter of 3 mm and an inner diameter of 2 mm. A water-to-water heat transfer experiment system was established to investigate the heat transfer and flow resistance characteristics of the heat exchanger within the shell-side Reynolds number range of 200–1400. The results indicate that the prototype exhibits a shell-side heat transfer coefficient five times higher than that of conventional shell and tube heat exchangers, although the shell-side friction factor is correspondingly increased. The tube bundle structure was simplified using a porous media and dual-cell model, and CFD analysis was performed to investigate the mechanism through which the presence of blocking tubes enhances heat transfer performance. Furthermore, the causes of excessive shell-side resistance were analyzed, and an improved structure was designed to effectively reduce shell-side flow resistance. The design principles for this type of heat exchanger were proposed, providing a foundation for the further development of large-scale power heat exchangers.

{"title":"Research on mini-channel heat exchangers with honeycomb modular structure: Design principles and convective heat transfer","authors":"Zhao-Yuan Wang, Si-Cong Tan, Jia-Min Zhu, Cong Guo, Yu-Yan Jiang","doi":"10.1016/j.ijthermalsci.2025.109832","DOIUrl":"10.1016/j.ijthermalsci.2025.109832","url":null,"abstract":"<div><div>The use of micro/mini channels in heat exchangers can significantly enhance the heat transfer coefficient, reduce equipment size, and lower manufacturing costs. However, challenges such as manufacturing difficulties and scalability limitations remain. To address these issues, this paper proposes a novel assembly structure based on a honeycomb configuration, using modular cores, each containing a bundle of stainless steel tubes with an outer diameter of 3 mm and an inner diameter of 2 mm. A water-to-water heat transfer experiment system was established to investigate the heat transfer and flow resistance characteristics of the heat exchanger within the shell-side Reynolds number range of 200–1400. The results indicate that the prototype exhibits a shell-side heat transfer coefficient five times higher than that of conventional shell and tube heat exchangers, although the shell-side friction factor is correspondingly increased. The tube bundle structure was simplified using a porous media and dual-cell model, and CFD analysis was performed to investigate the mechanism through which the presence of blocking tubes enhances heat transfer performance. Furthermore, the causes of excessive shell-side resistance were analyzed, and an improved structure was designed to effectively reduce shell-side flow resistance. The design principles for this type of heat exchanger were proposed, providing a foundation for the further development of large-scale power heat exchangers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109832"},"PeriodicalIF":4.9,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552882","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}

引用次数: 0

Augmented heat transfer and dehumidification by in-blade diamond-like structure

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-05 DOI: 10.1016/j.ijthermalsci.2025.109824

Xiaodan Hu , Tao Chen , Xu Chen , Fan Wu , Chun Wang , Youmin Hou , Danmei Xie , Wei Jiang

Steam turbines used in clean energy systems such as solar and nuclear power typically operate at lower inlet temperatures. This leads to high exit humidity and severe erosion of the last-stage blades, thus significantly compromising operational safety and economic efficiency. Advancements in manufacturing technologies, particularly metal 3D printing, enable the incorporation of intricate internal structures within turbine blades to mitigate erosion. We introduced a novel Diamond-Like Structure (DLS) within the hollow stator blade to augment heating dehumidification by reinforcing turbulence and heat transfer. We employed a coupled fluid-structure-thermal numerical simulation to evaluate its efficacy. Our findings reveal that the DLS blades significantly enhance the heating effect compared to a normal blade. Under 100 % rated mass flow operating condition, the DLS blade exhibited a 3.59 K increase in average blade surface temperature and a 9.8 % reduction in water film thickness compared to normal blade operating under identical 370 K heating steam conditions at 4 % flow rate. The effect of incorporating DLS within the blades is comparable to an increase of 27.36 K in the heating steam temperature or to the addition of 0.86 % of the main steam flow as heating steam. Flow visualization analysis indicates that the disruptive effect of the DLS significantly intensifies the heat transfer within the blades. Further investigations employing varied design parameters revealed that a denser DLS configuration resulted in an additional 3.34 K increase in blade surface temperature and a 13.16 % reduction in water film thickness relative to the original DLS blade. The innovative application of DLS in steam turbines demonstrates its potential for widespread use in thermal management across various blade types, including those used in wind turbines and gas turbine stators.

{"title":"Augmented heat transfer and dehumidification by in-blade diamond-like structure","authors":"Xiaodan Hu , Tao Chen , Xu Chen , Fan Wu , Chun Wang , Youmin Hou , Danmei Xie , Wei Jiang","doi":"10.1016/j.ijthermalsci.2025.109824","DOIUrl":"10.1016/j.ijthermalsci.2025.109824","url":null,"abstract":"<div><div>Steam turbines used in clean energy systems such as solar and nuclear power typically operate at lower inlet temperatures. This leads to high exit humidity and severe erosion of the last-stage blades, thus significantly compromising operational safety and economic efficiency. Advancements in manufacturing technologies, particularly metal 3D printing, enable the incorporation of intricate internal structures within turbine blades to mitigate erosion. We introduced a novel Diamond-Like Structure (DLS) within the hollow stator blade to augment heating dehumidification by reinforcing turbulence and heat transfer. We employed a coupled fluid-structure-thermal numerical simulation to evaluate its efficacy. Our findings reveal that the DLS blades significantly enhance the heating effect compared to a normal blade. Under 100 % rated mass flow operating condition, the DLS blade exhibited a 3.59 K increase in average blade surface temperature and a 9.8 % reduction in water film thickness compared to normal blade operating under identical 370 K heating steam conditions at 4 % flow rate. The effect of incorporating DLS within the blades is comparable to an increase of 27.36 K in the heating steam temperature or to the addition of 0.86 % of the main steam flow as heating steam. Flow visualization analysis indicates that the disruptive effect of the DLS significantly intensifies the heat transfer within the blades. Further investigations employing varied design parameters revealed that a denser DLS configuration resulted in an additional 3.34 K increase in blade surface temperature and a 13.16 % reduction in water film thickness relative to the original DLS blade. The innovative application of DLS in steam turbines demonstrates its potential for widespread use in thermal management across various blade types, including those used in wind turbines and gas turbine stators.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109824"},"PeriodicalIF":4.9,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552793","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}

引用次数: 0

Steady-state characteristics of the open natural circulation for a new cooling water tank in secondary passive residual heat removal system

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-04 DOI: 10.1016/j.ijthermalsci.2025.109828

Yilong Guo , Ting Hou , Kejie Tian , Ming Ding , Zehua Guo , Zhongning Sun

The concept of open natural circulation has garnered considerable interest in the design of advanced nuclear reactors owing to its inherent safety features. The present study proposes an innovative configuration for the cooling water tank of a secondary passive residual heat removal system, which introduces an open natural circulation into the system. An experimental setup was meticulously built, and a comprehensive suite of experiments was carried out to research the steady-state characteristics of the natural circulation. The results reveal a stable natural circulation, with a consistent flashing flow observed across all experimental scenarios. This phenomenon is elucidated as the interplay between flashing and boiling processes. A reduction in the heating power of the residual heat removal heat exchanger and the liquid level of the recharge water tank leads to a decrease in mass flow rate of the experimental loop. Analogous trends are noted in the temperature and pressure distributions of the riser, coinciding with intensified flashing events. Furthermore, natural circulation and convection developed in the heat exchange booth markedly enhance fluid mixing, minimizing thermal stratification. Analysis of the condensation length in the heat transfer tubes indicates that the condensation section expands predominantly due to the reduced heating power. The shift fosters a more balanced distribution of wall heat flux and facilitates the downward propagation of high-temperature fluid domains in the heat exchange booth. These findings offer valuable insights into the optimal design of residual heat removal systems and their potential application in improving plant layouts of nuclear power plants.

{"title":"Steady-state characteristics of the open natural circulation for a new cooling water tank in secondary passive residual heat removal system","authors":"Yilong Guo , Ting Hou , Kejie Tian , Ming Ding , Zehua Guo , Zhongning Sun","doi":"10.1016/j.ijthermalsci.2025.109828","DOIUrl":"10.1016/j.ijthermalsci.2025.109828","url":null,"abstract":"<div><div>The concept of open natural circulation has garnered considerable interest in the design of advanced nuclear reactors owing to its inherent safety features. The present study proposes an innovative configuration for the cooling water tank of a secondary passive residual heat removal system, which introduces an open natural circulation into the system. An experimental setup was meticulously built, and a comprehensive suite of experiments was carried out to research the steady-state characteristics of the natural circulation. The results reveal a stable natural circulation, with a consistent flashing flow observed across all experimental scenarios. This phenomenon is elucidated as the interplay between flashing and boiling processes. A reduction in the heating power of the residual heat removal heat exchanger and the liquid level of the recharge water tank leads to a decrease in mass flow rate of the experimental loop. Analogous trends are noted in the temperature and pressure distributions of the riser, coinciding with intensified flashing events. Furthermore, natural circulation and convection developed in the heat exchange booth markedly enhance fluid mixing, minimizing thermal stratification. Analysis of the condensation length in the heat transfer tubes indicates that the condensation section expands predominantly due to the reduced heating power. The shift fosters a more balanced distribution of wall heat flux and facilitates the downward propagation of high-temperature fluid domains in the heat exchange booth. These findings offer valuable insights into the optimal design of residual heat removal systems and their potential application in improving plant layouts of nuclear power plants.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109828"},"PeriodicalIF":4.9,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143552881","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}

引用次数: 0

Investigation of rail inclination effects on the aerothermal performance of turbine blade squealer tips with crown holes

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-04 DOI: 10.1016/j.ijthermalsci.2025.109808

Haimeng Zhou , Lei Luo , Fei Zeng , Han Yan , Wei Du , Songtao Wang

The purpose of the rail crown-holed blade squealer tip in heavy-duty gas turbine is to improve tip cooling and decrease gap leakage. By effectively interacting with the gap flow, the cooling air from the rail crown holes considerably lowers the leakage flow rate (LFR). Furthermore, this cooling system guarantees complete thermal protection for the cavity floor (CF) and rail crown surface (RCS). To evaluate the possible improvements of the squealer tip with rail crown holes, the pressure-side rail is inclined in this study. Heat transfer, cooling efficiency, and aerodynamic performance are assessed for two squealer tip designs (conventional and novel) and five inclined distances (−3.0 mm, −1.5 mm, 0 mm, 1.5 mm, and 3.0 mm). Results indicate that inclining the rail outward increases the coolant coverage on the CF in the novel tip, reducing heat transfer but lowering the cooling intensity. The novel configuration provides robust protection for the rail crown surface, and both inward and outward inclinations negatively impact rail cooling. In terms of aerodynamics, the LFR decreases linearly with greater inclination distances for both tip designs, and the rail crown holes are more effective in LFR control when the rail is inclined towards the inner side of the cavity.

{"title":"Investigation of rail inclination effects on the aerothermal performance of turbine blade squealer tips with crown holes","authors":"Haimeng Zhou , Lei Luo , Fei Zeng , Han Yan , Wei Du , Songtao Wang","doi":"10.1016/j.ijthermalsci.2025.109808","DOIUrl":"10.1016/j.ijthermalsci.2025.109808","url":null,"abstract":"<div><div>The purpose of the rail crown-holed blade squealer tip in heavy-duty gas turbine is to improve tip cooling and decrease gap leakage. By effectively interacting with the gap flow, the cooling air from the rail crown holes considerably lowers the leakage flow rate (LFR). Furthermore, this cooling system guarantees complete thermal protection for the cavity floor (CF) and rail crown surface (RCS). To evaluate the possible improvements of the squealer tip with rail crown holes, the pressure-side rail is inclined in this study. Heat transfer, cooling efficiency, and aerodynamic performance are assessed for two squealer tip designs (conventional and novel) and five inclined distances (−3.0 mm, −1.5 mm, 0 mm, 1.5 mm, and 3.0 mm). Results indicate that inclining the rail outward increases the coolant coverage on the CF in the novel tip, reducing heat transfer but lowering the cooling intensity. The novel configuration provides robust protection for the rail crown surface, and both inward and outward inclinations negatively impact rail cooling. In terms of aerodynamics, the LFR decreases linearly with greater inclination distances for both tip designs, and the rail crown holes are more effective in LFR control when the rail is inclined towards the inner side of the cavity.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109808"},"PeriodicalIF":4.9,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143548030","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}

引用次数: 0

Radiative behaviour of nozzle-confined switching arcs burning in axially blown C4F7N+CO2+PTFE mixture

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-03 DOI: 10.1016/j.ijthermalsci.2025.109825

S. Esmaeili , S.H. Park , J.D. Yan

The radiative behaviour of axially blown arcs in

C_{4} F_{7} N + {CO}_{2} + PTFE

mixture is presented as the basis for developing a simplified thermal radiation transfer model in industrial switching arc simulation. The Discrete Ordinates Method (DOM) is applied to produce the results in a wide range of currents (15 kA–60 kA) and at different locations in the nozzle of a model high-voltage circuit breaker. A distinctive feature has been identified in this work, i.e. the M-shaped radial profile of the radiative flux divergence for high current switching arcs. Vital information on the algorithms to define the Effective Emission Radius (EER) and the location and size of the Net Emission Zone (NEZ) and Net Absorption Zone (NAZ) for a one-dimensional NEC-based radiation model is also presented and analysed in depth.

引用次数: 0

Development and flow optimization of “Gyroid” based additive manufacturing heat exchanger: Both computational and experimental analyses

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-01 DOI: 10.1016/j.ijthermalsci.2025.109835

Wei-Hsiang Lai , Abdul Samad

There is a pressing demand for lightweight, space-saving, and high-performance heat exchangers (HEXs) in the aerospace industry. This study explores the Gyroid structure for efficient thermal energy management. Employing laser powder bed fusion, an optimized Gyroid HEX model is designed and comprehensively analyzed. Both computational and experimental analyses investigate thermal responses, considering various inlet flow rates and temperatures. Computational results are validated against experimental data, revealing favorable concurrence. The Gyroid HEX exhibits superior performance compared to a conventional plate HEX, demonstrating a 73.28 % increase in heat transfer rate. The Gyroid HEX demonstrated significantly greater stiffness than a single unit cell under a 2 kN compressive load, exhibiting a deflection of only 0.0056 mm compared to 0.2 mm for the single cell. With a von Mises stress of 42.6 MPa and a factor of safety of 4.81 against the yield strength of stainless steel 316L (205 MPa), the Gyroid structure exhibits excellent potential for high-strength aerospace applications. Additionally, compared to a Gyroid HEX made with 316L stainless steel, an aluminum Gyroid HEX demonstrates a 6.37 % increase in heat transfer rate. This study provides valuable insights into Gyroid HEX fluid flow and thermal characteristics, offering potential applications in the aerospace industry while acknowledging influencing factors on Gyroid structure strength.

{"title":"Development and flow optimization of “Gyroid” based additive manufacturing heat exchanger: Both computational and experimental analyses","authors":"Wei-Hsiang Lai , Abdul Samad","doi":"10.1016/j.ijthermalsci.2025.109835","DOIUrl":"10.1016/j.ijthermalsci.2025.109835","url":null,"abstract":"<div><div>There is a pressing demand for lightweight, space-saving, and high-performance heat exchangers (HEXs) in the aerospace industry. This study explores the Gyroid structure for efficient thermal energy management. Employing laser powder bed fusion, an optimized Gyroid HEX model is designed and comprehensively analyzed. Both computational and experimental analyses investigate thermal responses, considering various inlet flow rates and temperatures. Computational results are validated against experimental data, revealing favorable concurrence. The Gyroid HEX exhibits superior performance compared to a conventional plate HEX, demonstrating a 73.28 % increase in heat transfer rate. The Gyroid HEX demonstrated significantly greater stiffness than a single unit cell under a 2 kN compressive load, exhibiting a deflection of only 0.0056 mm compared to 0.2 mm for the single cell. With a von Mises stress of 42.6 MPa and a factor of safety of 4.81 against the yield strength of stainless steel 316L (205 MPa), the Gyroid structure exhibits excellent potential for high-strength aerospace applications. Additionally, compared to a Gyroid HEX made with 316L stainless steel, an aluminum Gyroid HEX demonstrates a 6.37 % increase in heat transfer rate. This study provides valuable insights into Gyroid HEX fluid flow and thermal characteristics, offering potential applications in the aerospace industry while acknowledging influencing factors on Gyroid structure strength.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109835"},"PeriodicalIF":4.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520545","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}

引用次数: 0

Molecular interactions study and thermophysical properties of glycerol-calcium chloride DESs: Insights from micro-nanoscale interfacial dynamics

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-01 DOI: 10.1016/j.ijthermalsci.2025.109836

Xiao Zhang , Long Geng , Kaifeng Luo , Wenbo Huang , Jiateng Zhao , Changhui Liu

Investigating the relationship between molecular interactions and thermophysical properties offers valuable insights into the development of advanced heat transfer fluids. In this work, glycerol-calcium chloride-based deep eutectic solvents (DES) were systematically examined through quantum chemical calculations and experimental methods to reveal their unique molecular mechanisms and thermal performance. Strong hydrogen bonding and coordination interactions were identified as critical factors enhancing the stability of the DES system, at the B3LYP-D3/6-31G(d, p) theoretical level, the calculated binding energy of DES reaches −223.94 kJ/mol, significantly lower than that of pure glycerol (−61.62 kJ/mol), indicating stronger and more stable interactions. Experimentally, the DES exhibited exceptional thermal stability, retaining structural integrity below 200 °C, while its boiling point increased by 4–5 °C and freezing point decreased by 4–6 °C compared to glycerol. Additionally, at an 8:1 glycerol-calcium chloride molar ratio, the specific heat capacity was approximately 1.5 % higher at 80 °C, demonstrating superior thermal storage capacity. These findings highlight the potential of DES as environmentally friendly and high-performance alternatives for industrial heat transfer and energy storage applications.

{"title":"Molecular interactions study and thermophysical properties of glycerol-calcium chloride DESs: Insights from micro-nanoscale interfacial dynamics","authors":"Xiao Zhang , Long Geng , Kaifeng Luo , Wenbo Huang , Jiateng Zhao , Changhui Liu","doi":"10.1016/j.ijthermalsci.2025.109836","DOIUrl":"10.1016/j.ijthermalsci.2025.109836","url":null,"abstract":"<div><div>Investigating the relationship between molecular interactions and thermophysical properties offers valuable insights into the development of advanced heat transfer fluids. In this work, glycerol-calcium chloride-based deep eutectic solvents (DES) were systematically examined through quantum chemical calculations and experimental methods to reveal their unique molecular mechanisms and thermal performance. Strong hydrogen bonding and coordination interactions were identified as critical factors enhancing the stability of the DES system, at the B3LYP-D3/6-31G(d, p) theoretical level, the calculated binding energy of DES reaches −223.94 kJ/mol, significantly lower than that of pure glycerol (−61.62 kJ/mol), indicating stronger and more stable interactions. Experimentally, the DES exhibited exceptional thermal stability, retaining structural integrity below 200 °C, while its boiling point increased by 4–5 °C and freezing point decreased by 4–6 °C compared to glycerol. Additionally, at an 8:1 glycerol-calcium chloride molar ratio, the specific heat capacity was approximately 1.5 % higher at 80 °C, demonstrating superior thermal storage capacity. These findings highlight the potential of DES as environmentally friendly and high-performance alternatives for industrial heat transfer and energy storage applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109836"},"PeriodicalIF":4.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143527172","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}

引用次数: 0

Throughflow and imperfect heat transfer effects on the stability of natural convection in a vertical porous layer 垂直多孔层中自然对流稳定性的通流和不完全传热效应

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-01 DOI: 10.1016/j.ijthermalsci.2025.109764

B.M. Shankar , D.H. Mayur , I.S. Shivakumara

The Gill stability problem of parallel buoyant flow in a differentially heated vertical porous channel (A.E. Gill, J. Fluid Mech., vol. 35, 1969, pp. 545–547) is revisited under the influence of uniform horizontal throughflow and imperfect heat transfer at the vertical boundaries. The boundary imperfections are modelled using Robin-type temperature conditions. The base flow solution is derived analytically, followed by a linear stability analysis that results in a fourth-order eigenvalue problem. The validity of Squire's theorem is established; therefore, two-dimensional motions are considered. Given the limitations of Gill's linear stability proof, a numerical solution to the eigenvalue problem is provided across a broad spectrum of input parameters. The findings suggest that convective instability is precluded for isothermal boundaries, even when horizontal throughflow is present. This conclusion is substantiated by an analysis of the eigenvalue spectrum, which reveals a negative amplification rate for normal mode perturbations, thereby affirming the asymptotic stability of the basic flow. For non-isothermal boundaries, the study traces neutral stability curves that define the threshold for linear instability and identifies the critical Darcy-Rayleigh number at which instability arises, considering various values of the Prandtl-Darcy number, Péclet number, and Biot number. Notably, the magnitude of the Biot number discloses a new pathway for instability, with throughflow not only influencing its onset but also giving rise to different onset modes.

{"title":"Throughflow and imperfect heat transfer effects on the stability of natural convection in a vertical porous layer","authors":"B.M. Shankar , D.H. Mayur , I.S. Shivakumara","doi":"10.1016/j.ijthermalsci.2025.109764","DOIUrl":"10.1016/j.ijthermalsci.2025.109764","url":null,"abstract":"<div><div>The Gill stability problem of parallel buoyant flow in a differentially heated vertical porous channel (A.E. Gill, <em>J. Fluid Mech.</em>, vol. 35, 1969, pp. 545–547) is revisited under the influence of uniform horizontal throughflow and imperfect heat transfer at the vertical boundaries. The boundary imperfections are modelled using Robin-type temperature conditions. The base flow solution is derived analytically, followed by a linear stability analysis that results in a fourth-order eigenvalue problem. The validity of Squire's theorem is established; therefore, two-dimensional motions are considered. Given the limitations of Gill's linear stability proof, a numerical solution to the eigenvalue problem is provided across a broad spectrum of input parameters. The findings suggest that convective instability is precluded for isothermal boundaries, even when horizontal throughflow is present. This conclusion is substantiated by an analysis of the eigenvalue spectrum, which reveals a negative amplification rate for normal mode perturbations, thereby affirming the asymptotic stability of the basic flow. For non-isothermal boundaries, the study traces neutral stability curves that define the threshold for linear instability and identifies the critical Darcy-Rayleigh number at which instability arises, considering various values of the Prandtl-Darcy number, Péclet number, and Biot number. Notably, the magnitude of the Biot number discloses a new pathway for instability, with throughflow not only influencing its onset but also giving rise to different onset modes.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109764"},"PeriodicalIF":4.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520546","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}

引用次数: 0

Determining the critical air gap influencing heat transfer mode under firefighter's clothing exposed to different fire conditions 确定影响暴露在不同火灾条件下消防员服装传热模式的临界气隙

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-01 DOI: 10.1016/j.ijthermalsci.2025.109830

Miao Tian , Songxue Fu , Ye Han , Yunyi Wang

Understanding the heat transfer mechanisms in the air gap under firefighter's uniform is crucial for accurately evaluating its thermal protective performance (TPP). However, existing research presents conflicting views regarding the air gap width (AGW) that natural convection begins and its relationship with the optimal TPP for the human body. To quantitively determine the critical AGW under clothing, experiments were conducted under three types of fire conditions, and the indicators for natural convection begin were calculated. Results indicated that both fire conditions and fabric layers affected the AGW in which natural convection began (9–18 mm). The largest t_2nd (time to second degree burns) was detected for single-layer fabric at 30 mm AGW. However, the t_2nd reached the maximum value at an AGW of 18 mm under 84 kW/m² hybrid heat environment, which was higher than no air gap (50 %) and 30 mm AGW condition (2.5 %), indicating an optimal TPP. Critical AGW also influenced the optimal TPP. The AGW of 18 mm at which multi-layer fabric achieved time-unsteady natural convection was comparable to the optimal TPP. The results of our investigation can provide theoretical reference for the structural design of fire-fighting suits and improve the safety of fire-fighting personnel.

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引用次数: 0

Stability and transport characteristics of Poiseuille-Rayleigh-Bénard double diffusive convection of binary fluids 二元流体的 Poiseuille-Rayleigh-Bénard 双扩散对流的稳定性和传输特性

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-01 DOI: 10.1016/j.ijthermalsci.2025.109833

Heng Lin , Li Zhang , Chun-Mei Wu , You-Rong Li

To investigate the stability, heat and mass transfer characteristics of Poiseuille-Rayleigh-Bénard (P-R-B) double diffusive convection of binary fluids in horizontal channels, we conducted three-dimensional numerical simulations using the finite volume method. The ranges of spanwise aspect ratio (B) of the channel, Reynolds (Re) number, buoyancy ratio (N) and Rayleigh (Ra) number are 1 ≤ B ≤ 10, 3 ≤ Re ≤ 25, −0.3 ≤ N ≤ 0.3, and 1.1 × 10³≤Ra≤1.2 × 10⁵, respectively. Results reveal that when secondary flow forms, the fluid's temperature and concentration exhibit sinusoidal variations in the spanwise direction. The secondary flow is characterized by the longitudinal rolls (LRs). As B increases or Re decreases, the onset of LRs and instability occurs at a lower critical Ra. As N shifts from negative to positive, the critical values for the onset of LRs and instability decrease. The variations of both Nusselt (Nu) and Sherwood (Sh) numbers along the streamwise direction can be divided into three regions. Despite the influence of solute buoyancy, the behavior of Nu variation in binary fluids is similar to that in pure working fluids. Meanwhile, Nu and Sh consistently follow the same trend, regardless of change in the direction of the solute buoyancy force. The increases in Ra and N enhance heat and mass transfer. The influence of B on heat and mass transfer abilities depends on the interplay between the number of LRs and the non-uniformities of the temperature and concentration distributions. Lastly, correlations for heat and mass transfer in fully developed regions of P-R-B double diffusive convection of binary fluids have been derived.

{"title":"Stability and transport characteristics of Poiseuille-Rayleigh-Bénard double diffusive convection of binary fluids","authors":"Heng Lin , Li Zhang , Chun-Mei Wu , You-Rong Li","doi":"10.1016/j.ijthermalsci.2025.109833","DOIUrl":"10.1016/j.ijthermalsci.2025.109833","url":null,"abstract":"<div><div>To investigate the stability, heat and mass transfer characteristics of Poiseuille-Rayleigh-Bénard (P-R-B) double diffusive convection of binary fluids in horizontal channels, we conducted three-dimensional numerical simulations using the finite volume method. The ranges of spanwise aspect ratio (<em>B</em>) of the channel, Reynolds (<em>Re</em>) number, buoyancy ratio (<em>N</em>) and Rayleigh (<em>Ra</em>) number are 1 ≤ <em>B</em> ≤ 10, 3 ≤ <em>Re</em> ≤ 25, −0.3 ≤ <em>N</em> ≤ 0.3, and 1.1 × 10<sup>3</sup>≤<em>Ra</em>≤1.2 × 10<sup>5</sup>, respectively. Results reveal that when secondary flow forms, the fluid's temperature and concentration exhibit sinusoidal variations in the spanwise direction. The secondary flow is characterized by the longitudinal rolls (LRs). As <em>B</em> increases or <em>Re</em> decreases, the onset of LRs and instability occurs at a lower critical <em>Ra</em>. As <em>N</em> shifts from negative to positive, the critical values for the onset of LRs and instability decrease. The variations of both Nusselt (<em>Nu</em>) and Sherwood (<em>Sh</em>) numbers along the streamwise direction can be divided into three regions. Despite the influence of solute buoyancy, the behavior of <em>Nu</em> variation in binary fluids is similar to that in pure working fluids. Meanwhile, <em>Nu</em> and <em>Sh</em> consistently follow the same trend, regardless of change in the direction of the solute buoyancy force. The increases in <em>Ra</em> and <em>N</em> enhance heat and mass transfer. The influence of <em>B</em> on heat and mass transfer abilities depends on the interplay between the number of LRs and the non-uniformities of the temperature and concentration distributions. Lastly, correlations for heat and mass transfer in fully developed regions of P-R-B double diffusive convection of binary fluids have been derived.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109833"},"PeriodicalIF":4.9,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143520543","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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