Pub Date : 2025-04-14DOI: 10.1016/j.ijthermalsci.2025.109920
Jin Lin , Jia Jia , Mengke Zhao , Qian Li , Shouxiang Lu , Mingjun Xu , Wei Li
The hydrogen diffusion and deflagration characteristics in different ignition positions in a closed battery compartment are systematically researched with experimental and numerical simulation methods, analyzing the hydrogen deflagration flame propagation process, flame propagation velocity, deflagration overpressure, and deflagration temperature. The results show that the maximum concentration gradient between the compartment top and compartment bottom is 4.9%. A nearly spherical flame is first formed after ignition, and the fireball expansion process is restricted by the compartment wall surface and gradually deformed to form a finger-shaped flame. The flame propagation velocity increases with time. And the flame front position increases slowly and then rapidly. In addition, the flame propagates upward from the bottom slightly faster than the flame propagates downward. The deflagration overpressure in ignition position S2 (the top corner of the compartment) is higher compared to that in ignition position S1 (the top center of the compartment), which is nearly 476 KPa. The rise to deflagration peak overpressure is faster when the ignition position is at the compartment top than that at the compartment bottom. In addition, the ignition position on the closed space side (ignition position S2∼S4) is more dangerous.
{"title":"Hydrogen diffusion and deflagration characteristics in a closed battery compartment: experimental and numerical simulation investigation","authors":"Jin Lin , Jia Jia , Mengke Zhao , Qian Li , Shouxiang Lu , Mingjun Xu , Wei Li","doi":"10.1016/j.ijthermalsci.2025.109920","DOIUrl":"10.1016/j.ijthermalsci.2025.109920","url":null,"abstract":"<div><div>The hydrogen diffusion and deflagration characteristics in different ignition positions in a closed battery compartment are systematically researched with experimental and numerical simulation methods, analyzing the hydrogen deflagration flame propagation process, flame propagation velocity, deflagration overpressure, and deflagration temperature. The results show that the maximum concentration gradient between the compartment top and compartment bottom is 4.9%. A nearly spherical flame is first formed after ignition, and the fireball expansion process is restricted by the compartment wall surface and gradually deformed to form a finger-shaped flame. The flame propagation velocity increases with time. And the flame front position increases slowly and then rapidly. In addition, the flame propagates upward from the bottom slightly faster than the flame propagates downward. The deflagration overpressure in ignition position S2 (the top corner of the compartment) is higher compared to that in ignition position S1 (the top center of the compartment), which is nearly 476 KPa. The rise to deflagration peak overpressure is faster when the ignition position is at the compartment top than that at the compartment bottom. In addition, the ignition position on the closed space side (ignition position S2∼S4) is more dangerous.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109920"},"PeriodicalIF":4.9,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828407","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 : 2025-04-12DOI: 10.1016/j.ijthermalsci.2025.109921
Heyu Zhang , Zihao Liu , Yuyang Chen , Gege Liu , Hongjia Bai , Jing Wu
While the broth temperature is crucial for the design, optimal operation and yield assessment of the microalgae photobioreactors (PBRs), no universal temperature model is available for large-scale outdoor fence-type horizontal tubular PBR plants. A temperature model is created as a function of both the static (location, orientation, and reactor geometry) and dynamic (light irradiance, air temperature, wind velocity, and operation) parameters. The mutual shading among the tubes has a significant effect on the broth temperature and is carefully considered. The model is applicable to both single-row and double-row coiled types of PBRs. The broth temperature in a plant consisting of 10 double-row coiled PBRs, each with 2600 L of gas-free cultivation broth, was subsequently predicted using the model. Based on an analysis of the suitability of various climate zones for algae production, subtropical and temperate monsoon climates are identified as favorable regions. Finally, the relative magnitudes of the various heat transfer rates causing the change in broth temperature are compared. The primary factors affecting the broth temperature are solar radiation, air convection and net longwave radiation, and the direct solar radiation captured by the tubular part of the plant is the most substantial contributor.
{"title":"Universal temperature model for large-scale outdoor horizontal tubular microalgae photobioreactor plants","authors":"Heyu Zhang , Zihao Liu , Yuyang Chen , Gege Liu , Hongjia Bai , Jing Wu","doi":"10.1016/j.ijthermalsci.2025.109921","DOIUrl":"10.1016/j.ijthermalsci.2025.109921","url":null,"abstract":"<div><div>While the broth temperature is crucial for the design, optimal operation and yield assessment of the microalgae photobioreactors (PBRs), no universal temperature model is available for large-scale outdoor fence-type horizontal tubular PBR plants. A temperature model is created as a function of both the static (location, orientation, and reactor geometry) and dynamic (light irradiance, air temperature, wind velocity, and operation) parameters. The mutual shading among the tubes has a significant effect on the broth temperature and is carefully considered. The model is applicable to both single-row and double-row coiled types of PBRs. The broth temperature in a plant consisting of 10 double-row coiled PBRs, each with 2600 L of gas-free cultivation broth, was subsequently predicted using the model. Based on an analysis of the suitability of various climate zones for algae production, subtropical and temperate monsoon climates are identified as favorable regions. Finally, the relative magnitudes of the various heat transfer rates causing the change in broth temperature are compared. The primary factors affecting the broth temperature are solar radiation, air convection and net longwave radiation, and the direct solar radiation captured by the tubular part of the plant is the most substantial contributor.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109921"},"PeriodicalIF":4.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820589","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}
According to experiments, preliminary heating the liner of the shaped charge allows to increase its penetration effect. The reason for this increase is an increase in the ultimate elongation of the formed shaped-charge jet due to thermal softening of its material. The possibility of heating the jet itself in free flight by thermal radiation of a tube located in front of the shaped charge with heat release in tube, provided by the course of a chemical reaction of self-propagating high-temperature synthesis, is considered. The features of heating shaped-charge jets by thermal radiation are investigated on the basis of an analytical solution of one-dimensional axisymmetric problem of nonstationary heat conductivity for a uniformly elongating cylindrical rod. It is shown that radiation heating of copper shaped-charge jets in free flight is possible, until their plastic break up, to a temperature that allows one to expect some increase in the penetrating effect of the jet.
{"title":"Increasing the ultimate elongation of metal shaped-charge jets by their radiation heating in free flight","authors":"S.V. Fedorov, A.V. Attetkov, I.A. Bolotina, A.M. Kharisov","doi":"10.1016/j.ijthermalsci.2025.109930","DOIUrl":"10.1016/j.ijthermalsci.2025.109930","url":null,"abstract":"<div><div>According to experiments, preliminary heating the liner of the shaped charge allows to increase its penetration effect. The reason for this increase is an increase in the ultimate elongation of the formed shaped-charge jet due to thermal softening of its material. The possibility of heating the jet itself in free flight by thermal radiation of a tube located in front of the shaped charge with heat release in tube, provided by the course of a chemical reaction of self-propagating high-temperature synthesis, is considered. The features of heating shaped-charge jets by thermal radiation are investigated on the basis of an analytical solution of one-dimensional axisymmetric problem of nonstationary heat conductivity for a uniformly elongating cylindrical rod. It is shown that radiation heating of copper shaped-charge jets in free flight is possible, until their plastic break up, to a temperature that allows one to expect some increase in the penetrating effect of the jet.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109930"},"PeriodicalIF":4.9,"publicationDate":"2025-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820590","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 : 2025-04-11DOI: 10.1016/j.ijthermalsci.2025.109919
Wei Duan (段薇), Jing Li (李静), Wanrui Gao (高万瑞), Bingjie Shi (史炳杰), Shuxin Liu (刘树鑫), Yundong Cao (曹云东)
With the increase in circuit breaker interrupting capacity, the frequency of arc-flash phenomena under high-current interruptions rises significantly. However, numerical studies on internal arc-flash phenomena in such equipment are still limited, with most research remaining in its early stages. Due to the complexity of the internal environment in DC molded case circuit breakers (DC-MCCBs), multi-field coupling simulations of high-energy plasma arcs present substantial challenges. This study conducts experimental comparisons to investigate the arc motion and arc-flash pattern evolution in DC-MCCBs under a constant driving magnetic field and varying interrupting current levels. Using magnetohydrodynamics (MHD), an improved arc model accounting for Archimedes force (buoyancy) is developed to analyze the fluid flow, mass transfer, and heat transfer mechanisms within the arc-flash phenomenon. Several structural improvements are proposed to address this phenomenon, with experimental validation of the optimizations. The results show that in the arc chamber of the DC-MCCB, the airflow dispersion effect causes a reverse vortex at the bend of the arc runner, weakening the arc's buoyancy. Additionally, the strong Lorentz force causes the high-energy arc in the lower section to be cut off and move too rapidly, impeding heat dissipation, which limits the utilization of the splitter plates. This results in uneven energy distribution of the arc in the splitter plate region and is the primary cause of the arc-flash phenomenon. The improved dual-side air outlets structure can increase the gas flow rate above the arc chamber, maintaining the forward vortex lift and enhancing the utilization of the splitter plates. The improved insulated gas-generating splitter plate structure can limit arc energy accumulation in the lower splitter region, increase arc chamber pressure, and improve the heat transfer coefficient of the medium, thereby reducing arc-flash energy. Through multi-factor, multi-level orthogonal experiments, comprehensive parameter optimization for arc-flash suppression measures is conducted, providing theoretical foundation and guiding value for the redesign of the new structure of DC-MCCB.
{"title":"Investigation on heat transfer and fluid flow of arc-flash phenomenon in DC molded case circuit breakers: Model optimization and structural improvement","authors":"Wei Duan (段薇), Jing Li (李静), Wanrui Gao (高万瑞), Bingjie Shi (史炳杰), Shuxin Liu (刘树鑫), Yundong Cao (曹云东)","doi":"10.1016/j.ijthermalsci.2025.109919","DOIUrl":"10.1016/j.ijthermalsci.2025.109919","url":null,"abstract":"<div><div>With the increase in circuit breaker interrupting capacity, the frequency of arc-flash phenomena under high-current interruptions rises significantly. However, numerical studies on internal arc-flash phenomena in such equipment are still limited, with most research remaining in its early stages. Due to the complexity of the internal environment in DC molded case circuit breakers (DC-MCCBs), multi-field coupling simulations of high-energy plasma arcs present substantial challenges. This study conducts experimental comparisons to investigate the arc motion and arc-flash pattern evolution in DC-MCCBs under a constant driving magnetic field and varying interrupting current levels. Using magnetohydrodynamics (MHD), an improved arc model accounting for Archimedes force (buoyancy) is developed to analyze the fluid flow, mass transfer, and heat transfer mechanisms within the arc-flash phenomenon. Several structural improvements are proposed to address this phenomenon, with experimental validation of the optimizations. The results show that in the arc chamber of the DC-MCCB, the airflow dispersion effect causes a reverse vortex at the bend of the arc runner, weakening the arc's buoyancy. Additionally, the strong Lorentz force causes the high-energy arc in the lower section to be cut off and move too rapidly, impeding heat dissipation, which limits the utilization of the splitter plates. This results in uneven energy distribution of the arc in the splitter plate region and is the primary cause of the arc-flash phenomenon. The improved dual-side air outlets structure can increase the gas flow rate above the arc chamber, maintaining the forward vortex lift and enhancing the utilization of the splitter plates. The improved insulated gas-generating splitter plate structure can limit arc energy accumulation in the lower splitter region, increase arc chamber pressure, and improve the heat transfer coefficient of the medium, thereby reducing arc-flash energy. Through multi-factor, multi-level orthogonal experiments, comprehensive parameter optimization for arc-flash suppression measures is conducted, providing theoretical foundation and guiding value for the redesign of the new structure of DC-MCCB.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109919"},"PeriodicalIF":4.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816641","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 : 2025-04-11DOI: 10.1016/j.ijthermalsci.2025.109925
Chandra Sekhar Saran, Alok Satapathy
Rising demand for cost effective and light weight thermal insulation, necessitates to use industrial and bio-wastes in polymers to develop such materials. The estimation of their thermal properties are also equally pertinent. In view of this, the present work reports on the utilization of waste glass dust (WGD) as functional fillers in polymer composites reinforced with two different natural fibers like hemp and flax to develope a new class of thermal insulation. A unique one dimensional heat conduction model is developed to numerically estimate the keff of such composites using a finite element method based tool with suitable boundary conditions. Sets of hemp-epoxy and flax-epoxy composites of different filler concentrations (0 %–20 % by weight) are then fabricated using hand lay-up route. Thermal properties such as conductivity, coefficient of thermal expansion (CTE) and glass transition temperature (Tg) of the fabricated composites are measured. The numerical model and experimental results in regard to the conductivity are found to be in good agreement. It is also found that the keff of epoxy can be reduced up to 0.144 W/m.K, about 25 % by the reinforcement of natural fibers and waste glass dust. Similarly, a maximum reduction of about 34 % in the value of CTE (27.238 × 10−6/°C) is achieved. Tg is found to improve from 97 °C (epoxy) to 125.43 °C and 127.03 °C for hemp-epoxy and flax-epoxy composites respectively with the addition of the glass dust particles. Armed with reduced conductivity and favourable CTE and Tg, these composites can potentially be used in thermal insulation applications.
{"title":"Heat transfer analysis of natural fiber composites reinforced with waste glass dust: a numerical and experimental study","authors":"Chandra Sekhar Saran, Alok Satapathy","doi":"10.1016/j.ijthermalsci.2025.109925","DOIUrl":"10.1016/j.ijthermalsci.2025.109925","url":null,"abstract":"<div><div>Rising demand for cost effective and light weight thermal insulation, necessitates to use industrial and bio-wastes in polymers to develop such materials. The estimation of their thermal properties are also equally pertinent. In view of this, the present work reports on the utilization of waste glass dust (WGD) as functional fillers in polymer composites reinforced with two different natural fibers like hemp and flax to develope a new class of thermal insulation. A unique one dimensional heat conduction model is developed to numerically estimate the k<sub>eff</sub> of such composites using a finite element method based tool with suitable boundary conditions. Sets of hemp-epoxy and flax-epoxy composites of different filler concentrations (0 %–20 % by weight) are then fabricated using hand lay-up route. Thermal properties such as conductivity, coefficient of thermal expansion (CTE) and glass transition temperature (T<sub>g</sub>) of the fabricated composites are measured. The numerical model and experimental results in regard to the conductivity are found to be in good agreement. It is also found that the k<sub>eff</sub> of epoxy can be reduced up to 0.144 W/m.K, about 25 % by the reinforcement of natural fibers and waste glass dust. Similarly, a maximum reduction of about 34 % in the value of CTE (27.238 × 10<sup>−6</sup>/°C) is achieved. T<sub>g</sub> is found to improve from 97 °C (epoxy) to 125.43 °C and 127.03 °C for hemp-epoxy and flax-epoxy composites respectively with the addition of the glass dust particles. Armed with reduced conductivity and favourable CTE and T<sub>g</sub>, these composites can potentially be used in thermal insulation applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109925"},"PeriodicalIF":4.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816643","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 : 2025-04-11DOI: 10.1016/j.ijthermalsci.2025.109907
Xindi Ming , Gaowen Liu , Lingjun Zhang , Ran Chang , Aqiang Lin
The measurement method of convective heat transfer coefficient is the technical bottlenecks in carrying out the current thermal analysis and refined design of rotating disk cavity. In order to measure the convective heat transfer coefficient of rotating disk with high rotational speed under complex thermal boundary conditions, this paper proposes a new strategy for acquiring convective heat transfer coefficient by combination with experimental data and numerical calculation of unsteady thermal conductivity in the solid domain. The convective heat transfer coefficient is indirectly obtained at the corresponding position by predicting heat flux through the loading of transient temperature field of solid surface measured in the experiment. Moreover, the effects of Fourier number and measurement random errors on the accuracy of the measurement method during unsteady heat transfer are investigated. The results show that the uncertainty of the convective heat transfer coefficient corresponding to the measurement method is less than 8.20 % when the measurement error is considered. Asymmetric flat plate heat transfer experiments are also carried out. The experimental results show that the deviation of the experimental results from the empirical correlation formula in the range of mass flow rate from 200 g/s to 400 g/s is less than 8 %, which proves that the measurement method can accurately measure the convective heat transfer coefficient under the asymmetric thermal boundary conditions. This paper provides a new convective heat transfer coefficient measurement technique for subsequent rotating disk cavity heat transfer experiments under complex thermal boundary conditions.
{"title":"Development and application on an unsteady measurement method of heat transfer for aero-engine rotating disk cavity with complex thermal boundary conditions","authors":"Xindi Ming , Gaowen Liu , Lingjun Zhang , Ran Chang , Aqiang Lin","doi":"10.1016/j.ijthermalsci.2025.109907","DOIUrl":"10.1016/j.ijthermalsci.2025.109907","url":null,"abstract":"<div><div>The measurement method of convective heat transfer coefficient is the technical bottlenecks in carrying out the current thermal analysis and refined design of rotating disk cavity. In order to measure the convective heat transfer coefficient of rotating disk with high rotational speed under complex thermal boundary conditions, this paper proposes a new strategy for acquiring convective heat transfer coefficient by combination with experimental data and numerical calculation of unsteady thermal conductivity in the solid domain. The convective heat transfer coefficient is indirectly obtained at the corresponding position by predicting heat flux through the loading of transient temperature field of solid surface measured in the experiment. Moreover, the effects of Fourier number and measurement random errors on the accuracy of the measurement method during unsteady heat transfer are investigated. The results show that the uncertainty of the convective heat transfer coefficient corresponding to the measurement method is less than 8.20 % when the measurement error is considered. Asymmetric flat plate heat transfer experiments are also carried out. The experimental results show that the deviation of the experimental results from the empirical correlation formula in the range of mass flow rate from 200 g/s to 400 g/s is less than 8 %, which proves that the measurement method can accurately measure the convective heat transfer coefficient under the asymmetric thermal boundary conditions. This paper provides a new convective heat transfer coefficient measurement technique for subsequent rotating disk cavity heat transfer experiments under complex thermal boundary conditions.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143814794","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 : 2025-04-11DOI: 10.1016/j.ijthermalsci.2025.109927
Shengjie Zhou, Wei Chen, Deyuan Zhao, Chuntong Li, Xinyi Chen, Hang Shi
In the compression refrigeration cycle system, the double-layered porous domain with small and large porosities respectively in dense and sparse porous layers are set above liquid flow minichannels to form evaporator on bottom heating surface for more heat flux to be enlarged, in which the convection occurs between liquid refrigerant and solid surfaces in channel while evaporation happens in porous layers due to pressure drop. The model illustrating the turbulent flow in liquid flow channel together with Darcy-Brinkman model describing the flow in porous domain or ribs are employed to investigate the effects of porosities and thickness respectively in porous ribs and porous domain on thermal performances in presented evaporator. The coefficient of system performance (COP) is utilized to evaluate the ratio of dissipated heat flux to power consumption in refrigeration system. Compared to the evaporator without porous ribs, the 131 % rise of dissipated heat flux can be obtained in mode with porous ribs paved on side wall surface in liquid channel. Besides, the larger dissipated heat flux and higher COP occur with larger and smaller porosities respectively in dense and sparse porous domains above flow channel in evaporator.
{"title":"Analysis on thermal performances in the evaporator with double-layered porous domain above flow channels in refrigeration system","authors":"Shengjie Zhou, Wei Chen, Deyuan Zhao, Chuntong Li, Xinyi Chen, Hang Shi","doi":"10.1016/j.ijthermalsci.2025.109927","DOIUrl":"10.1016/j.ijthermalsci.2025.109927","url":null,"abstract":"<div><div>In the compression refrigeration cycle system, the double-layered porous domain with small and large porosities respectively in dense and sparse porous layers are set above liquid flow minichannels to form evaporator on bottom heating surface for more heat flux to be enlarged, in which the convection occurs between liquid refrigerant and solid surfaces in channel while evaporation happens in porous layers due to pressure drop. The <span><math><mrow><mi>S</mi><mi>S</mi><mi>T</mi><mspace></mspace><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> model illustrating the turbulent flow in liquid flow channel together with Darcy-Brinkman model describing the flow in porous domain or ribs are employed to investigate the effects of porosities and thickness respectively in porous ribs and porous domain on thermal performances in presented evaporator. The coefficient of system performance (COP) is utilized to evaluate the ratio of dissipated heat flux to power consumption in refrigeration system. Compared to the evaporator without porous ribs, the 131 % rise of dissipated heat flux can be obtained in mode with porous ribs paved on side wall surface in liquid channel. Besides, the larger dissipated heat flux and higher COP occur with larger and smaller porosities respectively in dense and sparse porous domains above flow channel in evaporator.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109927"},"PeriodicalIF":4.9,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816642","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 : 2025-04-10DOI: 10.1016/j.ijthermalsci.2025.109922
Yihui Xiong, Yu Rao, Yuli Cheng
The Active Clearance Control (ACC) system utilizes multiple jet impingement to cool the turbine casing of aero engines, aiming to reduce the tip clearance through thermal contraction. This study models the flange structures at the external turbine casing as transverse high ribs, and the performance of ACC configurations are compared on baseline ‘I’-shaped smooth surface, the ‘L’-shaped high rib surface, and the ‘U’-shaped high rib surface. Experimental study and numerical simulation are carried out to obtain the flow and heat transfer characteristics. The results indicate that the arrangement of transverse high ribs on the target surface significantly influences the flow and heat transfer characteristics. The heat transfer on the high rib is lowered by 23.5 % and 15.5 % on Geometry L and U compared to baseline flat surface, respectively, while the heat transfer on the bottom surface is slightly affected. Based on numerical results, the total heat transfer increases by up to 6.74 % and 122 % on Geometry L and U due to extended wetted area, respectively. As the separation distance elevates, the Nusselt number on the bottom surface reduces by 15.6 % and 20.2 % for Geometry L and U, while the Nusselt number on the high rib increased by 0.5 % and 8.5 %, respectively. The Geometry U has more uniform heat transfer distributions, especially at high separation distances. The discharge coefficients of Geometry I and L are similar for using the same manifolds, and the discharge coefficient of Geometry U is 4.7 % higher for larger outlet to inlet area ratio. Based on the experimental data, Nusselt number correlations of the jet impingement over the total surfaces with different high ribs is developed over low Reynolds number ranging from 1,000 to 10,000, which provide more accurate heat transfer predictions than peer works.
主动间隙控制(ACC)系统利用多次喷射撞击来冷却航空发动机的涡轮壳,目的是通过热收缩来减小尖端间隙。本研究将涡轮壳外部的凸缘结构建模为横向高肋,并比较了 ACC 配置在基线 "I "形光滑表面、"L "形高肋表面和 "U "形高肋表面上的性能。通过实验研究和数值模拟获得了流动和传热特性。结果表明,靶面横向高肋的布置对流动和传热特性有显著影响。与基线平面相比,几何形状 L 和 U 上高肋的传热量分别降低了 23.5% 和 15.5%,而底面的传热量则受到轻微影响。根据数值结果,由于扩大了润湿面积,几何形状 L 和 U 的总传热量分别增加了 6.74 % 和 122 %。随着分离距离的增加,几何形状 L 和 U 的底面努塞尔特数分别降低了 15.6 % 和 20.2 %,而高肋上的努塞尔特数则分别增加了 0.5 % 和 8.5 %。几何形状 U 的传热分布更均匀,尤其是在高分离距离处。在使用相同分流板的情况下,几何形状 I 和 L 的排出系数相似,当出口与进口面积比较大时,几何形状 U 的排出系数高出 4.7%。根据实验数据,在雷诺数为 1,000 到 10,000 的低雷诺数范围内,建立了射流撞击具有不同高肋的总表面的努塞尔特数相关性,这比同行的研究提供了更精确的传热预测。
{"title":"Jet impingement heat transfer over surfaces with transverse high ribs at low Reynolds numbers pertinent to aeroengine ACC system","authors":"Yihui Xiong, Yu Rao, Yuli Cheng","doi":"10.1016/j.ijthermalsci.2025.109922","DOIUrl":"10.1016/j.ijthermalsci.2025.109922","url":null,"abstract":"<div><div>The Active Clearance Control (ACC) system utilizes multiple jet impingement to cool the turbine casing of aero engines, aiming to reduce the tip clearance through thermal contraction. This study models the flange structures at the external turbine casing as transverse high ribs, and the performance of ACC configurations are compared on baseline ‘I’-shaped smooth surface, the ‘L’-shaped high rib surface, and the ‘U’-shaped high rib surface. Experimental study and numerical simulation are carried out to obtain the flow and heat transfer characteristics. The results indicate that the arrangement of transverse high ribs on the target surface significantly influences the flow and heat transfer characteristics. The heat transfer on the high rib is lowered by 23.5 % and 15.5 % on Geometry L and U compared to baseline flat surface, respectively, while the heat transfer on the bottom surface is slightly affected. Based on numerical results, the total heat transfer increases by up to 6.74 % and 122 % on Geometry L and U due to extended wetted area, respectively. As the separation distance elevates, the Nusselt number on the bottom surface reduces by 15.6 % and 20.2 % for Geometry L and U, while the Nusselt number on the high rib increased by 0.5 % and 8.5 %, respectively. The Geometry U has more uniform heat transfer distributions, especially at high separation distances. The discharge coefficients of Geometry I and L are similar for using the same manifolds, and the discharge coefficient of Geometry U is 4.7 % higher for larger outlet to inlet area ratio. Based on the experimental data, Nusselt number correlations of the jet impingement over the total surfaces with different high ribs is developed over low Reynolds number ranging from 1,000 to 10,000, which provide more accurate heat transfer predictions than peer works.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109922"},"PeriodicalIF":4.9,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143816644","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 : 2025-04-09DOI: 10.1016/j.ijthermalsci.2025.109928
Agustín Salazar, Arantza Mendioroz
Laser-line lock-in thermography consists in illuminating the sample surface with a modulated and focused laser beam and recording the spatial distribution of the temperature oscillations with an infrared camera. In this work we show that it is possible to measure the thermal diffusivity and conductivity of thin films. When the sample is in vacuum, both amplitude and phase of the temperature oscillations behave as a linear functions of the distance to the center of the illumination, and the thermal diffusivity can be obtained from their slopes. When the thin film is surrounded by air, the linearity of amplitude and phase is lost due to the influence of heat conduction to the air. In this case, the thermal conductivity of the material can be obtained by fitting the complete theoretical model (which includes all the heat transfer mechanisms) to the recorded experimental temperature profiles. Validation is performed on two thin films of different thermal transport properties.
{"title":"Measurement of thermal diffusivity and conductivity of thin films using laser-line lock-in thermography","authors":"Agustín Salazar, Arantza Mendioroz","doi":"10.1016/j.ijthermalsci.2025.109928","DOIUrl":"10.1016/j.ijthermalsci.2025.109928","url":null,"abstract":"<div><div>Laser-line lock-in thermography consists in illuminating the sample surface with a modulated and focused laser beam and recording the spatial distribution of the temperature oscillations with an infrared camera. In this work we show that it is possible to measure the thermal diffusivity and conductivity of thin films. When the sample is in vacuum, both amplitude and phase of the temperature oscillations behave as a linear functions of the distance to the center of the illumination, and the thermal diffusivity can be obtained from their slopes. When the thin film is surrounded by air, the linearity of amplitude and phase is lost due to the influence of heat conduction to the air. In this case, the thermal conductivity of the material can be obtained by fitting the complete theoretical model (which includes all the heat transfer mechanisms) to the recorded experimental temperature profiles. Validation is performed on two thin films of different thermal transport properties.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109928"},"PeriodicalIF":4.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808304","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 : 2025-04-09DOI: 10.1016/j.ijthermalsci.2025.109912
Ahmad Obeidat , Hafiz Muhammad Ali
This study investigates the Marangoni condensation of steam-ethanol mixtures on wire-wrapped tubes at atmospheric pressure, with a constant vapor velocity of 0.48 m/s. Experiments were conducted using various mass ethanol concentrations (0.0125 %, 0.05 %, 0.1 %, and 0.3 %) with a 0.5 mm copper wire diameter, and wire pitches of (1.6 mm, 2 mm, 2.4 mm, and 2.9 mm). Special precautions were taken to eliminate air from the vapor phase and minimize experimental errors. Visual observations revealed distinct condensation modes, transitioning from film-wise condensation for the case of pure steam into pseudo-dropwise condensation with the addition of ethanol. The presence of ethanol improved heat transfer by reducing the film thickness, forming small droplets between the wire windings. Additionally, the wire wrapping increased the surface area, sliced film thickness, and minimized retention, thereby expanding the active surface area and significantly enhancing heat transfer. Both factors were thoroughly investigated to understand their combined effects. The results demonstrate significant improvements in heat transfer performance compared to pure steam, with notable increases in heat flux and heat transfer coefficients. The most significant enhancement ratio, defined as the ratio of observed heat transfer values to those predicted by Nusselt's theory (1916), was 9.9, occurring at an ethanol concentration of 0.1 % and a pitch of 2.9 mm.
{"title":"Marangoni condensation of steam-ethanol mixture on wire-wrapped tube: effect of wire pitch on heat transfer augmentation","authors":"Ahmad Obeidat , Hafiz Muhammad Ali","doi":"10.1016/j.ijthermalsci.2025.109912","DOIUrl":"10.1016/j.ijthermalsci.2025.109912","url":null,"abstract":"<div><div>This study investigates the Marangoni condensation of steam-ethanol mixtures on wire-wrapped tubes at atmospheric pressure, with a constant vapor velocity of 0.48 m/s. Experiments were conducted using various mass ethanol concentrations (0.0125 %, 0.05 %, 0.1 %, and 0.3 %) with a 0.5 mm copper wire diameter, and wire pitches of (1.6 mm, 2 mm, 2.4 mm, and 2.9 mm). Special precautions were taken to eliminate air from the vapor phase and minimize experimental errors. Visual observations revealed distinct condensation modes, transitioning from film-wise condensation for the case of pure steam into pseudo-dropwise condensation with the addition of ethanol. The presence of ethanol improved heat transfer by reducing the film thickness, forming small droplets between the wire windings. Additionally, the wire wrapping increased the surface area, sliced film thickness, and minimized retention, thereby expanding the active surface area and significantly enhancing heat transfer. Both factors were thoroughly investigated to understand their combined effects. The results demonstrate significant improvements in heat transfer performance compared to pure steam, with notable increases in heat flux and heat transfer coefficients. The most significant enhancement ratio, defined as the ratio of observed heat transfer values to those predicted by Nusselt's theory (1916), was 9.9, occurring at an ethanol concentration of 0.1 % and a pitch of 2.9 mm.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109912"},"PeriodicalIF":4.9,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808305","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}