Pub Date : 2025-03-17DOI: 10.1016/j.ijthermalsci.2025.109871
Ruoxiao Huang, Xuan Zhang, Shuang Zhao, Yubo Gao, Long Zhang, Mengjie Song
Icing and frosting problems on cold surfaces affect the normal operation of equipment and optimizing the anti-icing and ice-phobic properties of structured surfaces needs exploration of the droplet icing process on typical micro-pillars. Based on the apparent heat capacity method, the icing characteristics of sessile water droplets on the top of cold micro-pillars are numerically studied with the supercooling degree considered. The effects of the micro-pillar diameter and height as well as the droplet volume and surface temperature are obtained. As the micro-pillar diameter becomes smaller, the icing rate of the droplet decreases and the freezing time increases. A higher micro-pillar enlarges the thermal resistance, slows down the movement of the freezing front, and results in an increase in the freezing time. The freezing time goes up as the droplet volume and the surface temperature increase. This changing trend becomes more conspicuous for a smaller micro-pillar diameter. Furthermore, the relationship between the freezing time and the micro-pillar diameter and height is derived from heat transfer analysis. The freezing time is negatively related to the square of the micro-pillar diameter. When the micro-pillar height increases one time, the droplet freezing time will increase by 3.42 %. The findings in this work give insights into the icing mechanism of supercooled sessile water droplets on the top of cold micro-pillars and provide references for the design and optimization of anti-icing and anti-frosting surfaces.
{"title":"Icing characteristics of supercooled sessile water droplets on the top of cold micro-pillars","authors":"Ruoxiao Huang, Xuan Zhang, Shuang Zhao, Yubo Gao, Long Zhang, Mengjie Song","doi":"10.1016/j.ijthermalsci.2025.109871","DOIUrl":"10.1016/j.ijthermalsci.2025.109871","url":null,"abstract":"<div><div>Icing and frosting problems on cold surfaces affect the normal operation of equipment and optimizing the anti-icing and ice-phobic properties of structured surfaces needs exploration of the droplet icing process on typical micro-pillars. Based on the apparent heat capacity method, the icing characteristics of sessile water droplets on the top of cold micro-pillars are numerically studied with the supercooling degree considered. The effects of the micro-pillar diameter and height as well as the droplet volume and surface temperature are obtained. As the micro-pillar diameter becomes smaller, the icing rate of the droplet decreases and the freezing time increases. A higher micro-pillar enlarges the thermal resistance, slows down the movement of the freezing front, and results in an increase in the freezing time. The freezing time goes up as the droplet volume and the surface temperature increase. This changing trend becomes more conspicuous for a smaller micro-pillar diameter. Furthermore, the relationship between the freezing time and the micro-pillar diameter and height is derived from heat transfer analysis. The freezing time is negatively related to the square of the micro-pillar diameter. When the micro-pillar height increases one time, the droplet freezing time will increase by 3.42 %. The findings in this work give insights into the icing mechanism of supercooled sessile water droplets on the top of cold micro-pillars and provide references for the design and optimization of anti-icing and anti-frosting surfaces.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109871"},"PeriodicalIF":4.9,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-17DOI: 10.1016/j.ijthermalsci.2025.109858
Xuefeng Li , Awatif M.A. Elsiddieg , Aisha M. Alqahtani , Mohamed Ben Ammar , Ali Alzahrani , Mohamed Hussien , Saipunidzam Mahamad
To achieve high quality joint in keyhole laser welding of two dissimilar metals, phase transition behavior, the temperature and velocity field according to the variation of the process parameters were evaluated by utilizing both experimental and numerical approach. Due to the existing complex phenomena, the comprehensive analysis of the weld geometry and temperature field dependency in keyhole formation was performed either numerically or experimentally. An accurate numerical simulation of temperature and velocity fields, as well as material phase change at circular geometry path of laser beam movement were analyzed on dissimilar metals of duplex 2205 stainless steel and AISI 685 alloy metals to estimate such mentioned phenomena that could not be merely evaluated via experiments. A multi-physics numerical model that employed the finite volume method (FVM) and volume of fluid method (VOF) was utilized. The major novelty of dissimilar circular weld joint was simultaneous estimation the effect of different size and thereby volume of AISI 685 alloy and duplex 2205 alloy on the parts heat sink capacity, temperature gradient, melting ratio, fusion zone microstructure and fusion zone melt volume. The main reason for this is the asymmetric temperature distribution, resulting from the combined effects of material properties and the differing geometries and material volumes of the welded parts. To distinguish the laser process parameters, impact on the weld characterization according to the numerical simulation, the findings demonstrated that increasing the speed of the laser beam leads to the formation of bulge on the part's surface and around the keyhole while simultaneously diminishing the vapor volume. Furthermore, the laser beam's deviation from −0.25 mm at the AISI 685 alloy sheet to +0.25 at duplex 2205 led to the temperature reduction up to 300 °C at 1 mm distance from the joint centerline. Comparing the weld bead geometrical changes according to the variation of laser power and welding speed implies that the predicted temperature field of numerical simulation results is in good agreement with experimental results of weld bead geometry. The maximum error for experimental temperature measurement according to the variation of welding speed and laser power was less than 3 percent. By increasing laser power from 300 to 400 W, not only has the weld bead width become twofold, but also it penetrated toward the thickness completely, and the amount of weld bead overlap evidently increased more than 40 percent. The dissimilar joint fusion zone is mainly composed of cellular and columnar dendrite microstructure mainly created from nickel base alloy solidification according to the rapid heating followed by fast cooling induced by laser heating during welding.
为了在两种异种金属的锁孔激光焊接中实现高质量的接头，我们利用实验和数值方法对相变行为、温度场和速度场随工艺参数变化的情况进行了评估。由于存在复杂的现象，对焊接几何形状和锁孔形成过程中的温度场依赖性进行了数值或实验综合分析。针对双相 2205 不锈钢和 AISI 685 合金等异种金属，对激光束运动的圆形几何路径上的温度场、速度场以及材料相变进行了精确的数值模拟分析，以估计上述无法通过实验进行评估的现象。研究采用了有限体积法（FVM）和流体体积法（VOF）的多物理场数值模型。异种圆形焊接接头的主要创新点是同时估算了 AISI 685 合金和双相 2205 合金的不同尺寸和体积对零件散热能力、温度梯度、熔化率、熔合区微观结构和熔合区熔体体积的影响。造成这种情况的主要原因是材料特性和焊接零件的不同几何形状和材料体积的综合影响导致温度分布不对称。为了根据数值模拟来区分激光工艺参数对焊接特征的影响，研究结果表明，提高激光束的速度会导致在零件表面和锁孔周围形成隆起，同时减少蒸汽体积。此外，激光束的偏差从 AISI 685 合金板材的 -0.25 mm 到双相 2205 的 +0.25 mm，导致距离接头中心线 1 mm 处的温度降低到 300 °C。比较焊缝几何形状随激光功率和焊接速度的变化而变化的情况表明，数值模拟结果预测的温度场与焊缝几何形状的实验结果非常吻合。根据焊接速度和激光功率的变化，实验温度测量的最大误差小于 3%。激光功率从 300 W 增加到 400 W 后，焊缝宽度不仅增加了一倍，而且完全向厚度方向渗透，焊缝重叠量明显增加了 40% 以上。异种接头熔合区主要由蜂窝状和柱状树枝状微观结构组成，这些微观结构主要由焊接过程中激光加热引起的快速加热和快速冷却在镍基合金凝固过程中产生的。
{"title":"Numerical and experimental evaluation of temperature field and melt flow in keyhole laser welding of dissimilar duplex stainless steel and nickel base alloy","authors":"Xuefeng Li , Awatif M.A. Elsiddieg , Aisha M. Alqahtani , Mohamed Ben Ammar , Ali Alzahrani , Mohamed Hussien , Saipunidzam Mahamad","doi":"10.1016/j.ijthermalsci.2025.109858","DOIUrl":"10.1016/j.ijthermalsci.2025.109858","url":null,"abstract":"<div><div>To achieve high quality joint in keyhole laser welding of two dissimilar metals, phase transition behavior, the temperature and velocity field according to the variation of the process parameters were evaluated by utilizing both experimental and numerical approach. Due to the existing complex phenomena, the comprehensive analysis of the weld geometry and temperature field dependency in keyhole formation was performed either numerically or experimentally. An accurate numerical simulation of temperature and velocity fields, as well as material phase change at circular geometry path of laser beam movement were analyzed on dissimilar metals of duplex 2205 stainless steel and AISI 685 alloy metals to estimate such mentioned phenomena that could not be merely evaluated via experiments. A multi-physics numerical model that employed the finite volume method (FVM) and volume of fluid method (VOF) was utilized. The major novelty of dissimilar circular weld joint was simultaneous estimation the effect of different size and thereby volume of AISI 685 alloy and duplex 2205 alloy on the parts heat sink capacity, temperature gradient, melting ratio, fusion zone microstructure and fusion zone melt volume. The main reason for this is the asymmetric temperature distribution, resulting from the combined effects of material properties and the differing geometries and material volumes of the welded parts. To distinguish the laser process parameters, impact on the weld characterization according to the numerical simulation, the findings demonstrated that increasing the speed of the laser beam leads to the formation of bulge on the part's surface and around the keyhole while simultaneously diminishing the vapor volume. Furthermore, the laser beam's deviation from −0.25 mm at the AISI 685 alloy sheet to +0.25 at duplex 2205 led to the temperature reduction up to 300 °C at 1 mm distance from the joint centerline. Comparing the weld bead geometrical changes according to the variation of laser power and welding speed implies that the predicted temperature field of numerical simulation results is in good agreement with experimental results of weld bead geometry. The maximum error for experimental temperature measurement according to the variation of welding speed and laser power was less than 3 percent. By increasing laser power from 300 to 400 W, not only has the weld bead width become twofold, but also it penetrated toward the thickness completely, and the amount of weld bead overlap evidently increased more than 40 percent. The dissimilar joint fusion zone is mainly composed of cellular and columnar dendrite microstructure mainly created from nickel base alloy solidification according to the rapid heating followed by fast cooling induced by laser heating during welding.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109858"},"PeriodicalIF":4.9,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-17DOI: 10.1016/j.ijthermalsci.2025.109863
Jie Wen , Chenghua Zhu , Yanan Chen , Guoqiang Xu , Hao Li , Jiale Wang
Modern advanced turbine blade mid-chord cooling systems typically have three passages with different geometric shapes and cooling schemes. The current study conducts experimental and numerical analysis of the aerothermodynamic performance in a blade-shaped serpentine channel. The channel features asymmetric cross sections, 180-degree tip and hub turns, a minor secondary inlet, staggered ribs and bleed holes. The main inlet Reynolds number (Re) and rotation number (Ro) respectively vary between 17000 and 33000 and from 0 to 0.4, and the mass flow ratio of the minor secondary coolant to the main (MR) ranges from 0 to 0.2. It is revealed that the flow interactions between bleed holes and ribs significantly improve wall heat transfer. The rotation effect on heat transfer is less pronounced in a realistic channel than in a smooth one. The minor secondary stream can increase the channel heat transfer, and the ideal MR falls between 0.1 and 0.15. The proportion of the mass flow rate of each bleed hole to the total remains almost consistent regardless of the Re and Ro. Finally, the correlations of averaged heat transfer with high accuracy (≤10 %) are developed, which could interest turbine blade researchers and designers.
{"title":"Rotational flow and heat transfer in a serpentine cooling channel with realistic internal cooling schemes of a turbine blade","authors":"Jie Wen , Chenghua Zhu , Yanan Chen , Guoqiang Xu , Hao Li , Jiale Wang","doi":"10.1016/j.ijthermalsci.2025.109863","DOIUrl":"10.1016/j.ijthermalsci.2025.109863","url":null,"abstract":"<div><div>Modern advanced turbine blade mid-chord cooling systems typically have three passages with different geometric shapes and cooling schemes. The current study conducts experimental and numerical analysis of the aerothermodynamic performance in a blade-shaped serpentine channel. The channel features asymmetric cross sections, 180-degree tip and hub turns, a minor secondary inlet, staggered ribs and bleed holes. The main inlet Reynolds number (Re) and rotation number (Ro) respectively vary between 17000 and 33000 and from 0 to 0.4, and the mass flow ratio of the minor secondary coolant to the main (MR) ranges from 0 to 0.2. It is revealed that the flow interactions between bleed holes and ribs significantly improve wall heat transfer. The rotation effect on heat transfer is less pronounced in a realistic channel than in a smooth one. The minor secondary stream can increase the channel heat transfer, and the ideal MR falls between 0.1 and 0.15. The proportion of the mass flow rate of each bleed hole to the total remains almost consistent regardless of the Re and Ro. Finally, the correlations of averaged heat transfer with high accuracy (≤10 %) are developed, which could interest turbine blade researchers and designers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109863"},"PeriodicalIF":4.9,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143637604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-15DOI: 10.1016/j.ijthermalsci.2025.109860
Yu Sun, Xiaojun Fan, Jiao Wang, Yijun Wang, Junlin Cheng, Lu Luo, Yueru Li
To explore new efficient cooling technology for advanced gas turbine blades and reduce dependence on film cooling, this paper proposes a novel pipe network cooling structure. The design connects leading-edge impingement cooling holes to trailing-edge slits through lateral pipes and incorporates independent vertical pipes to form a network structure. This cooling structure can be applied to a complete blade cooling system, demonstrating strong cooling performance in the mid-chord region despite the absence of film holes, while achieving a more uniform overall temperature distribution, showing promising developmental potential. Through experimental and numerical simulations, comparisons were made with typical gas turbine blade cooling structures and double-wall cooling structures. The results indicate that this new pipes network cooling structure offers superior cooling performance and achieves a more uniform temperature distribution. In addition, the study investigated the impact of lateral pipes shapes and the distances between transverse and vertical pipes relative to the end wall on cooling performance. The results showed that, under the same boundary conditions, hexagonal pipes performed better. The relative positions of transverse and vertical pipes significantly affected blade cooling efficiency. P1/P2 = 0.5, the temperature distribution was the most uniform; P1/P2 = 1, heat transfer in the mid-chord region improved.
{"title":"Numerical research of a new pipe network cooling scheme without film holes for the gas turbine blade mid-chord region","authors":"Yu Sun, Xiaojun Fan, Jiao Wang, Yijun Wang, Junlin Cheng, Lu Luo, Yueru Li","doi":"10.1016/j.ijthermalsci.2025.109860","DOIUrl":"10.1016/j.ijthermalsci.2025.109860","url":null,"abstract":"<div><div>To explore new efficient cooling technology for advanced gas turbine blades and reduce dependence on film cooling, this paper proposes a novel pipe network cooling structure. The design connects leading-edge impingement cooling holes to trailing-edge slits through lateral pipes and incorporates independent vertical pipes to form a network structure. This cooling structure can be applied to a complete blade cooling system, demonstrating strong cooling performance in the mid-chord region despite the absence of film holes, while achieving a more uniform overall temperature distribution, showing promising developmental potential. Through experimental and numerical simulations, comparisons were made with typical gas turbine blade cooling structures and double-wall cooling structures. The results indicate that this new pipes network cooling structure offers superior cooling performance and achieves a more uniform temperature distribution. In addition, the study investigated the impact of lateral pipes shapes and the distances between transverse and vertical pipes relative to the end wall on cooling performance. The results showed that, under the same boundary conditions, hexagonal pipes performed better. The relative positions of transverse and vertical pipes significantly affected blade cooling efficiency. P<sub>1</sub>/P<sub>2</sub> = 0.5, the temperature distribution was the most uniform; P<sub>1</sub>/P<sub>2</sub> = 1, heat transfer in the mid-chord region improved.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109860"},"PeriodicalIF":4.9,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143628142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-15DOI: 10.1016/j.ijthermalsci.2025.109864
Davoud Abdi Lanbaran , Pouria Farokhi Kojour , Chao Wang , Chuang Wen , Zhen Wu , Bo Li
Corona discharge-produced ionic wind has emerged as a promising area of research for enhancing heat transfer. In contrast to conventional cooling methods, which often require complex geometrical designs and inefficient energy consumption, corona wind induction offers a cost-effective solution with lower energy requirements. This study focuses on investigating the effectiveness of direct and alternating corona discharge in enhancing heat transfer from pin fin arrays of heat sources. Using numerical simulations performed with COMSOL Multiphysics (6.0) and the finite element method (FEM), both DC and AC-sourced corona ionic winds were evaluated at electric field strengths ranging from to . Key parameters examined included the distance arrangement of high voltage electrodes to the pin surface (), pin fin diameter (), induced voltage (), depth of corona wind penetration, and the differences between DC and AC corona. The findings revealed a direct relationship between the amount of induced voltage and the diffusion of corona discharge, resulting in significant heat transfer enhancement of up to 66.83 % in turbulent flow at . Furthermore, direct corona induction exhibited a greater capability to enhance the heat transfer rate in comparison to AC induction. This discrepancy was notably more pronounced under turbulent conditions, registering at , whereas in the laminar flow regime, the difference amounted to . In addition, the results show that the implementation of corona wind leads to a significant increase in the Nusselt number, especially within the turbulent flow range, with the use of direct corona wind at a voltage elevating the local Nusselt number value from to . The results highlight the effectiveness and advantages of corona wind induction as an energy-efficient solution for tackling heat dissipation challenges in complex geometries.
{"title":"Comparative analysis of heat transfer enhancement using direct current and alternating current corona discharge in pin fin arrays","authors":"Davoud Abdi Lanbaran , Pouria Farokhi Kojour , Chao Wang , Chuang Wen , Zhen Wu , Bo Li","doi":"10.1016/j.ijthermalsci.2025.109864","DOIUrl":"10.1016/j.ijthermalsci.2025.109864","url":null,"abstract":"<div><div>Corona discharge-produced ionic wind has emerged as a promising area of research for enhancing heat transfer. In contrast to conventional cooling methods, which often require complex geometrical designs and inefficient energy consumption, corona wind induction offers a cost-effective solution with lower energy requirements. This study focuses on investigating the effectiveness of direct and alternating corona discharge in enhancing heat transfer from pin fin arrays of heat sources. Using numerical simulations performed with COMSOL Multiphysics (6.0) and the finite element method (FEM), both DC and AC-sourced corona ionic winds were evaluated at electric field strengths ranging from <span><math><mrow><mi>V</mi><mo>=</mo><mn>15</mn><mspace></mspace><mi>k</mi><mi>V</mi></mrow></math></span> to <span><math><mrow><mi>V</mi><mo>=</mo><mn>25</mn><mspace></mspace><mi>k</mi><mi>V</mi></mrow></math></span>. Key parameters examined included the distance arrangement of high voltage electrodes to the pin surface (<span><math><mrow><mi>A</mi></mrow></math></span>), pin fin diameter (<span><math><mrow><msub><mi>D</mi><mi>f</mi></msub></mrow></math></span>), induced voltage (<span><math><mrow><mi>V</mi></mrow></math></span>), depth of corona wind penetration, and the differences between DC and AC corona. The findings revealed a direct relationship between the amount of induced voltage and the diffusion of corona discharge, resulting in significant heat transfer enhancement of up to 66.83 % in turbulent flow at <span><math><mrow><mi>V</mi><mo>=</mo><mn>25</mn><mspace></mspace><mi>k</mi><mi>V</mi></mrow></math></span>. Furthermore, direct corona induction exhibited a greater capability to enhance the heat transfer rate in comparison to AC induction. This discrepancy was notably more pronounced under turbulent conditions, registering at <span><math><mrow><mn>10.02</mn><mo>%</mo></mrow></math></span>, whereas in the laminar flow regime, the difference amounted to <span><math><mrow><mn>4.73</mn><mo>%</mo></mrow></math></span>. In addition, the results show that the implementation of corona wind leads to a significant increase in the Nusselt number, especially within the turbulent flow range, with the use of direct corona wind at a <span><math><mrow><mn>25</mn><mspace></mspace><mi>k</mi><mi>V</mi></mrow></math></span> voltage elevating the local Nusselt number value from <span><math><mrow><mn>29.37</mn></mrow></math></span> to <span><math><mrow><mn>52.18</mn></mrow></math></span>. The results highlight the effectiveness and advantages of corona wind induction as an energy-efficient solution for tackling heat dissipation challenges in complex geometries.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109864"},"PeriodicalIF":4.9,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-13DOI: 10.1016/j.ijthermalsci.2025.109861
Junhao Gao, Jie Xu, Jin Lin, Shouxiang Lu
The current standard methods for evaluating the fire resistance of high-speed train floor structures involve large-scale experiments that incur significant costs. To explore the feasibility of reducing the scale of these structural fire resistance tests, this study develops a two-dimensional numerical simulation model to assess the fire resistance of multilayer floor structures. The model's accuracy and applicability are rigorously validated through various fire resistance experiments conducted at multiple scales. The study emphasizes the dynamic thermal response of high-speed train floor structures, demonstrating a clear correlation between structural scale and fire resistance. Notably, the times to thermal insulation failure and integrity failure of multilayer composite floor structures decrease progressively with increasing scale. This trend can be described by an exponential function. Additionally, the model is employed to examine the effect of the ratio of the exposed surface size to the actual material size on fire resistance, with larger ratios leading to more rapid fire resistance failures.
{"title":"Size effect on the fire resistance of multilayer composite floor structures","authors":"Junhao Gao, Jie Xu, Jin Lin, Shouxiang Lu","doi":"10.1016/j.ijthermalsci.2025.109861","DOIUrl":"10.1016/j.ijthermalsci.2025.109861","url":null,"abstract":"<div><div>The current standard methods for evaluating the fire resistance of high-speed train floor structures involve large-scale experiments that incur significant costs. To explore the feasibility of reducing the scale of these structural fire resistance tests, this study develops a two-dimensional numerical simulation model to assess the fire resistance of multilayer floor structures. The model's accuracy and applicability are rigorously validated through various fire resistance experiments conducted at multiple scales. The study emphasizes the dynamic thermal response of high-speed train floor structures, demonstrating a clear correlation between structural scale and fire resistance. Notably, the times to thermal insulation failure and integrity failure of multilayer composite floor structures decrease progressively with increasing scale. This trend can be described by an exponential function. Additionally, the model is employed to examine the effect of the ratio of the exposed surface size to the actual material size on fire resistance, with larger ratios leading to more rapid fire resistance failures.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109861"},"PeriodicalIF":4.9,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-12DOI: 10.1016/j.ijthermalsci.2025.109859
Xiaoyu Li , Yongkang Hao , Ziang Zhu , Anjun Li , Zhuangjun Wu , Xiaogang Xu , Fuyao Wang
The heat absorption efficiency of particles in a solar receiver is significantly affected by internal flow characteristics. A detailed investigation of the transient behavior of bubbles is essential for optimizing receiver design and improving its control. The present work investigates the transient flow characteristics and heat transfer in a fluidized bed particle solar receiver through numerical simulations with a Eulerian-Eulerian framework. The results reveal that the gas volume fraction showed significant temporal fluctuations, with increased gas flow rates and higher axial positions promoting the formation of larger gas core structures. The transient distribution of bubble diameters was obtained and analyzed. As the axial position and inlet flow rate increased, the growth rate of the cumulative curve declined, leading to a reduced cumulative probability of smaller bubbles. The power spectral energy was predominantly concentrated in the 0–1 Hz frequency range. With higher inlet flow rates, the spectral energy peak shifted leftward, indicating an extended period of bubble diameter variation. Finally, wall-to-bed heat transfer was analyzed. Higher flow rates led to improved temperature distribution and wall-to-bed heat transfer coefficient, but beyond a critical threshold, further increases would hinder effective heat transfer.
{"title":"Numerical investigation of transient flow characteristics and heat transfer in a fluidized bed particle solar receiver","authors":"Xiaoyu Li , Yongkang Hao , Ziang Zhu , Anjun Li , Zhuangjun Wu , Xiaogang Xu , Fuyao Wang","doi":"10.1016/j.ijthermalsci.2025.109859","DOIUrl":"10.1016/j.ijthermalsci.2025.109859","url":null,"abstract":"<div><div>The heat absorption efficiency of particles in a solar receiver is significantly affected by internal flow characteristics. A detailed investigation of the transient behavior of bubbles is essential for optimizing receiver design and improving its control. The present work investigates the transient flow characteristics and heat transfer in a fluidized bed particle solar receiver through numerical simulations with a Eulerian-Eulerian framework. The results reveal that the gas volume fraction showed significant temporal fluctuations, with increased gas flow rates and higher axial positions promoting the formation of larger gas core structures. The transient distribution of bubble diameters was obtained and analyzed. As the axial position and inlet flow rate increased, the growth rate of the cumulative curve declined, leading to a reduced cumulative probability of smaller bubbles. The power spectral energy was predominantly concentrated in the 0–1 Hz frequency range. With higher inlet flow rates, the spectral energy peak shifted leftward, indicating an extended period of bubble diameter variation. Finally, wall-to-bed heat transfer was analyzed. Higher flow rates led to improved temperature distribution and wall-to-bed heat transfer coefficient, but beyond a critical threshold, further increases would hinder effective heat transfer.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109859"},"PeriodicalIF":4.9,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-11DOI: 10.1016/j.ijthermalsci.2025.109840
Bo Ren , Shihao Yang , Lixin Yang , Xiang Luo , Zeyu Wu
In the rotor-stator system, the windage effect due to rotating bolts has become a significant limitation on the cooling performance of the secondary air system (SAS). To address this issue, this paper develops a quasi-3D modeling method for the rotor-stator system with superimposed flow, capable of effectively analyzing the power consumption and temperature rise under different bolt geometries (shape and number) and operating parameters (throughflow Reynolds number and rotating Reynolds number). The results using quasi-3D modeling method can not only preserve the effect of non-uniform flow on power consumption and temperature rise but also align well with the experimental values. The windage losses due to bolts account for over 81 % of the total power consumption and changing bolt shape leads to significant differences in form drag. Using cylindrical bolts can apparently reduce the windage losses and heating compared to polygonal bolts. The bolt shape has minimal influence on the windage in cavity region. The adiabatic wall temperature is sensitive to the bolt number as the turbulent parameter is below 0.219. Both the power consumption and temperature rise decrease due to lower form drag losses once the pitch ratio exceeds 0.69. Using a bolt cover to create a continuous band distribution can effectively alleviate the windage effect from bolts. The quasi-3D modeling method enhances efficiency in applying CFD to SAS design and the findings hold significant implications for improving the cooling properties of SAS and controlling the power consumption of windage losses in the rotor-stator system.
{"title":"QUASI-3D modelling of heat generation in rotor-stator systems: Explicit roles of bolt geometry and operating parameters","authors":"Bo Ren , Shihao Yang , Lixin Yang , Xiang Luo , Zeyu Wu","doi":"10.1016/j.ijthermalsci.2025.109840","DOIUrl":"10.1016/j.ijthermalsci.2025.109840","url":null,"abstract":"<div><div>In the rotor-stator system, the windage effect due to rotating bolts has become a significant limitation on the cooling performance of the secondary air system (SAS). To address this issue, this paper develops a quasi-3D modeling method for the rotor-stator system with superimposed flow, capable of effectively analyzing the power consumption and temperature rise under different bolt geometries (shape and number) and operating parameters (throughflow Reynolds number and rotating Reynolds number). The results using quasi-3D modeling method can not only preserve the effect of non-uniform flow on power consumption and temperature rise but also align well with the experimental values. The windage losses due to bolts account for over 81 % of the total power consumption and changing bolt shape leads to significant differences in form drag. Using cylindrical bolts can apparently reduce the windage losses and heating compared to polygonal bolts. The bolt shape has minimal influence on the windage in cavity region. The adiabatic wall temperature is sensitive to the bolt number as the turbulent parameter is below 0.219. Both the power consumption and temperature rise decrease due to lower form drag losses once the pitch ratio exceeds 0.69. Using a bolt cover to create a continuous band distribution can effectively alleviate the windage effect from bolts. The quasi-3D modeling method enhances efficiency in applying CFD to SAS design and the findings hold significant implications for improving the cooling properties of SAS and controlling the power consumption of windage losses in the rotor-stator system.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109840"},"PeriodicalIF":4.9,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143592527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-10DOI: 10.1016/j.ijthermalsci.2025.109827
Irina Znamenskaya, Murat Muratov, Daria Dolbnya
This study investigates the application of a specific infrared thermography technique to visualize high-speed flows by analyzing the emerging thermal distribution on quartz windows of a shock tube channel’s sidewalls (). The interaction between non-stationary flow () and the streamlined channel walls results in energy exchange at the interface, forming a corresponding thermal load distribution due to the heat tangential conduction. These integral heat flux traces were captured using an infrared camera and quantitatively investigated. Panoramic infrared imaging conducted by a thermal camera with operating range and an exposure time of up to was combined and compared with a frame-by-frame shadowgraphy. The resulting radiation intensity integral maps were analyzed as a function of the incident shock wave Mach number, local flow-quartz interaction duration and heat flux magnitude, influenced by non-stationary boundary layer behavior. It is shown that the acquired inhomogeneous integral thermal patterns on the channel inner surfaces accurately correspond to the gas-dynamic structures of the flow according to their duration and intensity. The analysis underscores key local flow characteristics, including regions of deceleration and compression, stagnation zones, and rarefaction areas. Thermal maps captured from different observation angles () revealed sidewall-specific heating patterns and composite images of overall radiation intensity. Experimental findings underline the feasibility of using this approach to investigate spatial–temporal characteristics of non-stationary flows via evolving thermal distributions on streamlined surfaces under conditions of non-stationary heat and mass transfer.
{"title":"IR-thermography studies of high-speed gas-dynamic flows","authors":"Irina Znamenskaya, Murat Muratov, Daria Dolbnya","doi":"10.1016/j.ijthermalsci.2025.109827","DOIUrl":"10.1016/j.ijthermalsci.2025.109827","url":null,"abstract":"<div><div>This study investigates the application of a specific infrared thermography technique to visualize high-speed flows by analyzing the emerging thermal distribution on quartz windows of a shock tube channel’s sidewalls (<span><math><mrow><mn>24</mn><mo>×</mo><mn>48</mn><mspace></mspace><mi>m</mi><mi>m</mi></mrow></math></span>). The interaction between non-stationary flow (<span><math><mrow><mi>M</mi><mo>=</mo><mn>1</mn><mo>.</mo><mn>8</mn><mo>−</mo><mn>4</mn><mo>.</mo><mn>0</mn></mrow></math></span>) and the streamlined channel walls results in energy exchange at the interface, forming a corresponding thermal load distribution due to the heat tangential conduction. These integral heat flux traces were captured using an infrared camera and quantitatively investigated. Panoramic infrared imaging conducted by a thermal camera with operating range <span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mo>−</mo><mn>5</mn><mo>.</mo><mn>1</mn><mspace></mspace><mi>μ</mi><mi>m</mi></mrow></math></span> and an exposure time of up to <span><math><mrow><mn>500</mn><mspace></mspace><mi>μ</mi><mi>s</mi></mrow></math></span> was combined and compared with a frame-by-frame shadowgraphy. The resulting radiation intensity integral maps were analyzed as a function of the incident shock wave Mach number, local flow-quartz interaction duration and heat flux magnitude, influenced by non-stationary boundary layer behavior. It is shown that the acquired inhomogeneous integral thermal patterns on the channel inner surfaces accurately correspond to the gas-dynamic structures of the flow according to their duration and intensity. The analysis underscores key local flow characteristics, including regions of deceleration and compression, stagnation zones, and rarefaction areas. Thermal maps captured from different observation angles (<span><math><mrow><mi>Θ</mi><mo>≈</mo><mn>0</mn><mo>°</mo><mo>,</mo><mn>25</mn><mo>°</mo><mo>,</mo><mn>36</mn><mo>°</mo></mrow></math></span>) revealed sidewall-specific heating patterns and composite images of overall radiation intensity. Experimental findings underline the feasibility of using this approach to investigate spatial–temporal characteristics of non-stationary flows via evolving thermal distributions on streamlined surfaces under conditions of non-stationary heat and mass transfer.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109827"},"PeriodicalIF":4.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579328","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}
To limit the environmental footprint of refrigeration, transport of frozen goods based on natural fluids and phase change materials (PCMs) may be a promising solution. However, frost formation on the surface of the PCM encasing might limit the heat exchange and overall efficiency of the frozen food transport. The present work reports the numerical modeling of the heat and mass transfer for a flat plate cooled by a melting PCM located inside an air channel on which frost develops. Eulerian–Eulerian multiphase model is employed in conjunction with the Shear Stress Transport (SST) model to simulate the frost formation on the surface of the PCM encasing. It is first favorably validated against a number of published experimental and numerical data. Then the melting model based on the so-called enthalpy-porosity approach is applied as a User-Defined Function (UDF). The solidification and melting model as an applied UDF has been also validated against experimental and numerical works for lauric acid as PCM. The combined Eulerian–Eulerian Multiphase frost model and the solidification and melting model show that the flow must be below the PCM rather than above, in order to promote the formation of the Rayleigh–Bénard convection cells within the PCM when the melting process begins. Otherwise, the heat released from the frost formation on the surface of the PCM encasing and the heat transferred from the high temperature humid air are not effectively diffused within the PCM and results in localized high-temperature zones within the PCM.
{"title":"Combined Eulerian–Eulerian Multiphase Frost model and solidification and melting model to predict the cooling performance of subcooled eutectic plates","authors":"Jihyuk Jeong , Sébastien Poncet , Benoit Michel , Jocelyn Bonjour","doi":"10.1016/j.ijthermalsci.2025.109837","DOIUrl":"10.1016/j.ijthermalsci.2025.109837","url":null,"abstract":"<div><div>To limit the environmental footprint of refrigeration, transport of frozen goods based on natural fluids and phase change materials (PCMs) may be a promising solution. However, frost formation on the surface of the PCM encasing might limit the heat exchange and overall efficiency of the frozen food transport. The present work reports the numerical modeling of the heat and mass transfer for a flat plate cooled by a melting PCM located inside an air channel on which frost develops. Eulerian–Eulerian multiphase model is employed in conjunction with the <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> Shear Stress Transport (SST) model to simulate the frost formation on the surface of the PCM encasing. It is first favorably validated against a number of published experimental and numerical data. Then the melting model based on the so-called enthalpy-porosity approach is applied as a User-Defined Function (UDF). The solidification and melting model as an applied UDF has been also validated against experimental and numerical works for lauric acid as PCM. The combined Eulerian–Eulerian Multiphase frost model and the solidification and melting model show that the flow must be below the PCM rather than above, in order to promote the formation of the Rayleigh–Bénard convection cells within the PCM when the melting process begins. Otherwise, the heat released from the frost formation on the surface of the PCM encasing and the heat transferred from the high temperature humid air are not effectively diffused within the PCM and results in localized high-temperature zones within the PCM.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109837"},"PeriodicalIF":4.9,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143579327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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