International Journal of Thermal Sciences最新文献

Effect of louver-perforated V-type baffles on thermal effectiveness and entropy in round tube

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-16 DOI: 10.1016/j.ijthermalsci.2025.109939

Pongjet Promvonge , Somchai Sripattanapipat , Maturose Suchatawat , Mahdi Erfanian Nakhchi , Sompol Skullong

An experimental investigation was conducted to assess the influence of insertion of a louver-perforated V-type baffle (LVB) vortex generator into a consistent heat-fluxed tube on thermal performance. This study aimed to optimize thermal effectiveness to boost energy savings and reduce the heat exchanger size. The experiments focused on investigating the thermal features, as well as estimating the entropy of turbulent flow at Reynolds numbers (Re) varying between 4750 and 29,290. The LVBs were positioned in two different arrays on a supporting tape during the present experiment: "V-down" and "V-up," with the V-apex oriented upstream and downstream, respectively, at a fixed attack angle (

α

= 52°). At one relative baffle height (B_R = 0.3) and pitch (P_R = 1.0), the LVBs dealt with six louver flapped angles (

θ

= 0°, 10°, 20°, 30°, 45°, and 90°) in addition to three louver-hole sizes and locations (θ₁, θ₂ and θ₁₂). Comparative analysis was also conducted on data obtained from the current smooth tube. According to the findings, the louver angle

θ_{1}

= 20°, located on the baffle's trailing end, had the greatest relative Nusselt number (Nu_R), which was 5.9 times for V-down and 6.38 times for V-up. Furthermore, compared to the V-down and V-up solid baffles (

θ

= 0°), their friction losses were lessened. The V-up LVB reached its minimum value at

θ_{1}

= 20°, corresponding to the lowest Re. At

θ_{1}

= 20°, the V-up LVB attained its minimum entropy generation (

{\dot{S}}_{g e n}^{'}

) and maximum reduced entropy factor (S_R) around 20.3. At a comparable

θ_{1}

= 20°, the maximal thermal effectiveness factor (TEF) of V-down and V-up were approximately 2.39 and 2.59, respectively. The estimation and documentation of correlations were also performed for the parameters under consideration, namely Nu, f, and TEF.

{"title":"Effect of louver-perforated V-type baffles on thermal effectiveness and entropy in round tube","authors":"Pongjet Promvonge , Somchai Sripattanapipat , Maturose Suchatawat , Mahdi Erfanian Nakhchi , Sompol Skullong","doi":"10.1016/j.ijthermalsci.2025.109939","DOIUrl":"10.1016/j.ijthermalsci.2025.109939","url":null,"abstract":"<div><div>An experimental investigation was conducted to assess the influence of insertion of a louver-perforated V-type baffle (LVB) vortex generator into a consistent heat-fluxed tube on thermal performance. This study aimed to optimize thermal effectiveness to boost energy savings and reduce the heat exchanger size. The experiments focused on investigating the thermal features, as well as estimating the entropy of turbulent flow at Reynolds numbers (Re) varying between 4750 and 29,290. The LVBs were positioned in two different arrays on a supporting tape during the present experiment: \"V-down\" and \"V-up,\" with the V-apex oriented upstream and downstream, respectively, at a fixed attack angle (<span><math><mrow><mi>α</mi></mrow></math></span> = 52°). At one relative baffle height (B<sub>R</sub> = 0.3) and pitch (P<sub>R</sub> = 1.0), the LVBs dealt with six louver flapped angles (<span><math><mrow><mi>θ</mi></mrow></math></span> = 0°, 10°, 20°, 30°, 45°, and 90°) in addition to three louver-hole sizes and locations (<em>θ</em><sub>1</sub>, <em>θ</em><sub>2</sub> and <em>θ</em><sub>12</sub>). Comparative analysis was also conducted on data obtained from the current smooth tube. According to the findings, the louver angle <span><math><mrow><msub><mi>θ</mi><mn>1</mn></msub></mrow></math></span> = 20°, located on the baffle's trailing end, had the greatest relative Nusselt number (Nu<sub>R</sub>), which was 5.9 times for V-down and 6.38 times for V-up. Furthermore, compared to the V-down and V-up solid baffles (<span><math><mrow><mi>θ</mi></mrow></math></span> = 0°), their friction losses were lessened. The V-up LVB reached its minimum value at <span><math><mrow><msub><mi>θ</mi><mn>1</mn></msub></mrow></math></span> = 20°, corresponding to the lowest Re. At <span><math><mrow><msub><mi>θ</mi><mn>1</mn></msub></mrow></math></span> = 20°, the V-up LVB attained its minimum entropy generation (<span><math><mrow><msubsup><mover><mi>S</mi><mo>˙</mo></mover><mrow><mi>g</mi><mi>e</mi><mi>n</mi></mrow><mo>′</mo></msubsup></mrow></math></span>) and maximum reduced entropy factor (<em>S</em><sub>R</sub>) around 20.3. At a comparable <span><math><mrow><msub><mi>θ</mi><mn>1</mn></msub></mrow></math></span> = 20°, the maximal thermal effectiveness factor (TEF) of V-down and V-up were approximately 2.39 and 2.59, respectively. The estimation and documentation of correlations were also performed for the parameters under consideration, namely <em>Nu</em>, <em>f</em>, and TEF.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109939"},"PeriodicalIF":4.9,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143835200","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

Numerical simulation of a novel composite microchannel for large-scale THz phased array antennas thermal management 用于大规模太赫兹相控阵天线热管理的新型复合微通道的数值模拟

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-15 DOI: 10.1016/j.ijthermalsci.2025.109924

Zhengpeng Chen , Bo Yuan , Jie Yang , Zhuo Zhang , Yuqi Tang , Yang Yang , Hansheng Zheng , Yong Chen

As terahertz (THz) phased arrays antennas (PAA) scale up, the accompanying increase in power density and heat generation poses significant challenges for thermal management. The aim of this work is to explore effective solutions for achieving an ideal uniform temperature distribution and lower peak temperature in the context of large-scale small heat sources. Considering the high-efficiency heat transfer and surface temperature uniformity of microchannel heat sinks, this paper proposes a novel composite microchannel heat sink structure based on traditional microchannel heat sinks. Using peak temperature, pressure drop, temperature uniformity, thermal stress, and thermal deformation as key indicators, a comprehensive numerical simulation analysis of the novel composite microchannel heat sink and traditional microchannel heat sinks under different Reynolds numbers (

R e

) were conducted based on computational fluid dynamics (CFD) and elasticity mechanics. The results show that the novel composite microchannel heat sink exhibits superior fluid flow and heat transfer performance with better temperature uniformity. At

R e = 1500

, it achieves improvements of 11.2 %, 9.2 %, 14.6 %, and 8.2 % compared to the traditional microchannel heat sinks. Moreover, it can achieve the same peak temperature as traditional microchannel heat sinks with lower pumping power. Furthermore, it was found that the novel composite microchannel heat sink can effectively reduce the pressure drop in microfluidic systems. At

R e = 1500

, the pressure drop is reduced by 37.5 %, 39 %, 31.9 %, and 35.6 % compared to the corresponding traditional microchannel heat sink. Overall, the novel composite microchannel heat sink outperforms traditional microchannel heat sinks in both flow characteristics and temperature uniformity.

{"title":"Numerical simulation of a novel composite microchannel for large-scale THz phased array antennas thermal management","authors":"Zhengpeng Chen , Bo Yuan , Jie Yang , Zhuo Zhang , Yuqi Tang , Yang Yang , Hansheng Zheng , Yong Chen","doi":"10.1016/j.ijthermalsci.2025.109924","DOIUrl":"10.1016/j.ijthermalsci.2025.109924","url":null,"abstract":"<div><div>As terahertz (THz) phased arrays antennas (PAA) scale up, the accompanying increase in power density and heat generation poses significant challenges for thermal management. The aim of this work is to explore effective solutions for achieving an ideal uniform temperature distribution and lower peak temperature in the context of large-scale small heat sources. Considering the high-efficiency heat transfer and surface temperature uniformity of microchannel heat sinks, this paper proposes a novel composite microchannel heat sink structure based on traditional microchannel heat sinks. Using peak temperature, pressure drop, temperature uniformity, thermal stress, and thermal deformation as key indicators, a comprehensive numerical simulation analysis of the novel composite microchannel heat sink and traditional microchannel heat sinks under different Reynolds numbers (<span><math><mrow><mi>R</mi><mi>e</mi></mrow></math></span>) were conducted based on computational fluid dynamics (CFD) and elasticity mechanics. The results show that the novel composite microchannel heat sink exhibits superior fluid flow and heat transfer performance with better temperature uniformity. At <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>1500</mn></mrow></math></span>, it achieves improvements of 11.2 %, 9.2 %, 14.6 %, and 8.2 % compared to the traditional microchannel heat sinks. Moreover, it can achieve the same peak temperature as traditional microchannel heat sinks with lower pumping power. Furthermore, it was found that the novel composite microchannel heat sink can effectively reduce the pressure drop in microfluidic systems. At <span><math><mrow><mi>R</mi><mi>e</mi><mo>=</mo><mn>1500</mn></mrow></math></span>, the pressure drop is reduced by 37.5 %, 39 %, 31.9 %, and 35.6 % compared to the corresponding traditional microchannel heat sink. Overall, the novel composite microchannel heat sink outperforms traditional microchannel heat sinks in both flow characteristics and temperature uniformity.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109924"},"PeriodicalIF":4.9,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828488","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

Similarity analysis for reorientation and self-pressurization of cryogenic fluids in on-orbit propellant tanks

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-14 DOI: 10.1016/j.ijthermalsci.2025.109910

Zhongqi Zuo , Bin Wang , Rongrong Lv , Lige Tong , Li Wang

Cryogenic propellants are identified as one of the most promising technologies due to their advantages in specific impulses. However, there still exist gaps in the available knowledge of microgravity cryogenic fluid management, particularly on a large scale. In this study, scaling laws for the interface reorientation and self-pressurization conditions are proposed and validated. Accurate scaling for stationary self-pressurization conditions was achieved by adopting

F o

and

B o

as similarity criteria. For interface reorientation conditions, the pressure is influenced mainly by the rapid condensation on the interface. The time-factor is proposed to decouple the evolution of the interface and the characteristic length. A new scaling law,

t \sim L^{1.65}

, is proposed to improve the interface similarity between the subscale and the prototype models. The new scaling law significantly improved the pressure prediction accuracy in the scaled models, with a maximum pressure deviation of less than 5%. The scaling methods for the on-orbit cryogenic propellant fluids were systematically proposed and examined by drop tower and ground-based experiments. The results provide a theoretical basis for further scaling experimental and numerical studies of on-orbit cryogenic storage.

{"title":"Similarity analysis for reorientation and self-pressurization of cryogenic fluids in on-orbit propellant tanks","authors":"Zhongqi Zuo , Bin Wang , Rongrong Lv , Lige Tong , Li Wang","doi":"10.1016/j.ijthermalsci.2025.109910","DOIUrl":"10.1016/j.ijthermalsci.2025.109910","url":null,"abstract":"<div><div>Cryogenic propellants are identified as one of the most promising technologies due to their advantages in specific impulses. However, there still exist gaps in the available knowledge of microgravity cryogenic fluid management, particularly on a large scale. In this study, scaling laws for the interface reorientation and self-pressurization conditions are proposed and validated. Accurate scaling for stationary self-pressurization conditions was achieved by adopting <span><math><mrow><mi>F</mi><mi>o</mi></mrow></math></span> and <span><math><mrow><mi>B</mi><mi>o</mi></mrow></math></span> as similarity criteria. For interface reorientation conditions, the pressure is influenced mainly by the rapid condensation on the interface. The time-factor is proposed to decouple the evolution of the interface and the characteristic length. A new scaling law, <span><math><mrow><mi>t</mi><mo>∼</mo><msup><mrow><mi>L</mi></mrow><mrow><mn>1</mn><mo>.</mo><mn>65</mn></mrow></msup></mrow></math></span>, is proposed to improve the interface similarity between the subscale and the prototype models. The new scaling law significantly improved the pressure prediction accuracy in the scaled models, with a maximum pressure deviation of less than 5%. The scaling methods for the on-orbit cryogenic propellant fluids were systematically proposed and examined by drop tower and ground-based experiments. The results provide a theoretical basis for further scaling experimental and numerical studies of on-orbit cryogenic storage.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828591","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

Dispersion relation and frequency-dependent thermal conductivity of the two-temperature systems 双温系统的频散关系和随频率变化的热导率

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-14 DOI: 10.1016/j.ijthermalsci.2025.109937

S.L. Sobolev , I.V. Kudinov

We investigate analytically the complex-valued dispersion relation for two-temperature systems with coupling. Based on this dispersion relation, we obtain and analyze the real and imaginary parts of the wave number as well as phase velocity and penetration depth. Furthermore, an effective apparent thermal conductivity is introduced, which depends on the frequency of external thermal disturbances due to coupling effects. It is shown that values of thermal conductivity at high frequencies are drastically reduced compared to low frequencies. The onset of the decrease occurs at a frequency threshold of the order of inverse of characteristic time for energy exchange between subsystems (coupling time). At this frequency, the energy exchange between the subsystems reaches its maximum value and the local nonequilibrium (non-Fourier) effects play the most important role. This work establishes a theoretical basis and opens possibilities for controlling and manipulating heat transfer in heterogeneous systems including composite and thermal metamaterials.

我们对具有耦合的双温系统的复值频散关系进行了分析研究。根据这一频散关系，我们得到并分析了波数的实部和虚部以及相速度和穿透深度。此外，我们还引入了有效表观热导率，它取决于耦合效应导致的外部热干扰频率。研究表明，与低频相比，高频下的热导率值会急剧下降。下降开始于子系统间能量交换特征时间（耦合时间）的倒数的频率阈值。在这个频率上，子系统之间的能量交换达到最大值，局部非平衡（非傅里叶）效应发挥了最重要的作用。这项研究为控制和操纵异质系统（包括复合材料和热超材料）中的热传递奠定了理论基础，提供了可能性。

引用次数: 0

Effect of porous structure on the thermal and hydraulic features of combined heat sinks with open microchannels and pin-fins

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-14 DOI: 10.1016/j.ijthermalsci.2025.109933

Yifan Li , Tianyu Wang , Congzhe Zhu , Zhipeng Wang , Junlan Yang , Bin Yang

The rapid development of the computing power of data centers, has resulted in a sharp increase of heat generation on electronic chips. The traditional heat sinks cannot remove the ultra-high heat flux effectively. Novel heat sinks with porous structures are developed to cope with serious overtemperature issues to ensure the safe operation of electronic chips. The effect of the position, porosity, and permeability of porous configurations on the thermal and hydrodynamic features is explored and compared with the traditional smooth microchannel (SM) and the open microchannel with solid pin-fins (OM-SPF). Results manifest that the porous structure is conducive to increasing heat transfer area and enlarging flow space. However, its arrangement significantly influences the temperature control ability and thermal transport rate. For the open microchannel with porous pin-fins (OM-PPF), the friction loss is reduced by 57.1 %, but the perturbance effect is much weaker than the solid counterpart. For the open microchannel with porous sidewall ribs (OM-PSR), the Nusselt number is increased by 2.7, 2.2, and 1.6 times, the peak temperature is reduced by 9.5 °C, 5.6 °C, and 2.5 °C compared to the SM, OM-PPF, and OM-SPF at Re = 631. The friction factor of OM-PSR is 55.1 % smaller than the OM-SPF at Re = 131. The synergy effect of the heat transport enhancement by central solid fins and the drag reduction by porous sidewalls in OM-PSR brings a superior overall capability with a total performance index (TPI) of 2.0 at Re = 329. The small porosity and large permeability of porous sidewalls result in a higher Nusselt number, lower friction factor, and better overall efficiency. The OM-PSR with porosity of 0.2 and permeability of 1 × 10⁻⁸ m² obtains the highest TPI of 4.63 at Re = 131, which helps to balance the heat dissipation and pump consumption, demonstrates a great potential for improving the energy efficiency of the cooling system in high-power data centers.

{"title":"Effect of porous structure on the thermal and hydraulic features of combined heat sinks with open microchannels and pin-fins","authors":"Yifan Li , Tianyu Wang , Congzhe Zhu , Zhipeng Wang , Junlan Yang , Bin Yang","doi":"10.1016/j.ijthermalsci.2025.109933","DOIUrl":"10.1016/j.ijthermalsci.2025.109933","url":null,"abstract":"<div><div>The rapid development of the computing power of data centers, has resulted in a sharp increase of heat generation on electronic chips. The traditional heat sinks cannot remove the ultra-high heat flux effectively. Novel heat sinks with porous structures are developed to cope with serious overtemperature issues to ensure the safe operation of electronic chips. The effect of the position, porosity, and permeability of porous configurations on the thermal and hydrodynamic features is explored and compared with the traditional smooth microchannel (SM) and the open microchannel with solid pin-fins (OM-SPF). Results manifest that the porous structure is conducive to increasing heat transfer area and enlarging flow space. However, its arrangement significantly influences the temperature control ability and thermal transport rate. For the open microchannel with porous pin-fins (OM-PPF), the friction loss is reduced by 57.1 %, but the perturbance effect is much weaker than the solid counterpart. For the open microchannel with porous sidewall ribs (OM-PSR), the Nusselt number is increased by 2.7, 2.2, and 1.6 times, the peak temperature is reduced by 9.5 °C, 5.6 °C, and 2.5 °C compared to the SM, OM-PPF, and OM-SPF at Re = 631. The friction factor of OM-PSR is 55.1 % smaller than the OM-SPF at Re = 131. The synergy effect of the heat transport enhancement by central solid fins and the drag reduction by porous sidewalls in OM-PSR brings a superior overall capability with a total performance index (<em>TPI</em>) of 2.0 at Re = 329. The small porosity and large permeability of porous sidewalls result in a higher Nusselt number, lower friction factor, and better overall efficiency. The OM-PSR with porosity of 0.2 and permeability of 1 × 10<sup>−8</sup> m<sup>2</sup> obtains the highest <em>TPI</em> of 4.63 at Re = 131, which helps to balance the heat dissipation and pump consumption, demonstrates a great potential for improving the energy efficiency of the cooling system in high-power data centers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109933"},"PeriodicalIF":4.9,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143826184","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

Numerical investigation of arc and droplet dynamics in local dry underwater welding under varying ambient pressures

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-14 DOI: 10.1016/j.ijthermalsci.2025.109931

Xuefei Cui , Ji Chen , Jingheng Liang , Hao Su , Shengli Li , Chuansong Wu

A comprehensive numerical model was developed to investigate the effects of varying ambient pressures on arc and molten metal behaviors in local dry underwater welding (LDUW). The model accounted for the influence of ambient pressure on the thermophysical properties of plasma (mass density, specific enthalpy, specific heat, electrical conductivity, thermal conductivity, and viscosity), ensuring high accuracy of simulation results. The results revealed that increasing ambient pressure significantly concentrated the arc shape and altered the spatial distribution of metal vapor. This constriction fundamentally modified the arc plasma properties by reducing the effective heat transfer area and intensifying the interactions between plasma and molten metal. Key parameters such as arc temperature, plasma velocity, current density, and electromagnetic force all decreased with increasing ambient pressure, leading to reduced energy input to the weld pool. Furthermore, the increased ambient pressure altered the droplet transfer behavior. Higher ambient pressures reduced the droplet detachment frequency, while increasing droplet size due to the enhanced constriction of the arc and the altered surface tension forces at the plasma-droplet interface. To validate the numerical model, experiments were conducted using high-speed imaging to capture the real-time droplet processes, and the arc temperature distribution wad measured using spectroscopic methods. The experiments results showed excellent agreement with the simulation data, confirming the reliability of the model. This study provides valuable insights into the impact of ambient pressure on LDUW, offering a solid foundation for optimizing welding parameters to improve process efficiency and weld quality under varying high ambient pressure conditions.

{"title":"Numerical investigation of arc and droplet dynamics in local dry underwater welding under varying ambient pressures","authors":"Xuefei Cui , Ji Chen , Jingheng Liang , Hao Su , Shengli Li , Chuansong Wu","doi":"10.1016/j.ijthermalsci.2025.109931","DOIUrl":"10.1016/j.ijthermalsci.2025.109931","url":null,"abstract":"<div><div>A comprehensive numerical model was developed to investigate the effects of varying ambient pressures on arc and molten metal behaviors in local dry underwater welding (LDUW). The model accounted for the influence of ambient pressure on the thermophysical properties of plasma (mass density, specific enthalpy, specific heat, electrical conductivity, thermal conductivity, and viscosity), ensuring high accuracy of simulation results. The results revealed that increasing ambient pressure significantly concentrated the arc shape and altered the spatial distribution of metal vapor. This constriction fundamentally modified the arc plasma properties by reducing the effective heat transfer area and intensifying the interactions between plasma and molten metal. Key parameters such as arc temperature, plasma velocity, current density, and electromagnetic force all decreased with increasing ambient pressure, leading to reduced energy input to the weld pool. Furthermore, the increased ambient pressure altered the droplet transfer behavior. Higher ambient pressures reduced the droplet detachment frequency, while increasing droplet size due to the enhanced constriction of the arc and the altered surface tension forces at the plasma-droplet interface. To validate the numerical model, experiments were conducted using high-speed imaging to capture the real-time droplet processes, and the arc temperature distribution wad measured using spectroscopic methods. The experiments results showed excellent agreement with the simulation data, confirming the reliability of the model. This study provides valuable insights into the impact of ambient pressure on LDUW, offering a solid foundation for optimizing welding parameters to improve process efficiency and weld quality under varying high ambient pressure conditions.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109931"},"PeriodicalIF":4.9,"publicationDate":"2025-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143826185","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

Hydrogen diffusion and deflagration characteristics in a closed battery compartment: experimental and numerical simulation investigation

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-14 DOI: 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}

引用次数: 0

Universal temperature model for large-scale outdoor horizontal tubular microalgae photobioreactor plants

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-12 DOI: 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.

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引用次数: 0

Increasing the ultimate elongation of metal shaped-charge jets by their radiation heating in free flight

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-12 DOI: 10.1016/j.ijthermalsci.2025.109930

S.V. Fedorov, A.V. Attetkov, I.A. Bolotina, A.M. Kharisov

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.

引用次数: 0

Investigation on heat transfer and fluid flow of arc-flash phenomenon in DC molded case circuit breakers: Model optimization and structural improvement

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-04-11 DOI: 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.

随着断路器分断能力的提高，在大电流分断情况下发生弧闪现象的频率也大幅上升。然而，对此类设备内部弧闪现象的数值研究仍然有限，大多数研究仍处于早期阶段。由于直流塑壳断路器（DC-MCCB）内部环境的复杂性，高能等离子体电弧的多场耦合模拟面临巨大挑战。本研究进行了实验比较，以研究在恒定驱动磁场和不同分断电流水平下直流塑壳断路器中的电弧运动和弧闪模式演变。利用磁流体力学 (MHD)，开发了一种考虑到阿基米德力（浮力）的改进电弧模型，用于分析弧闪现象中的流体流动、传质和传热机制。针对这一现象提出了若干结构改进建议，并对优化方案进行了实验验证。结果表明，在 DC-MCCB 的电弧室中，气流分散效应会在电弧流道弯曲处产生反向涡流，从而削弱电弧的浮力。此外，强大的洛伦兹力会导致下部的高能电弧被切断，移动速度过快，阻碍散热，从而限制了分流板的利用率。这导致电弧在分流板区域的能量分布不均，是产生弧闪现象的主要原因。改进后的双侧出气口结构可以增加电弧室上方的气体流速，保持前向涡流升力，提高分流板的利用率。改进的绝缘气体发生劈裂板结构可以限制弧能在劈裂板下部区域的积累，增加弧室压力，提高介质的传热系数，从而降低弧闪能量。通过多因素、多层次的正交实验，对抑制弧闪措施的参数进行了综合优化，为直流-多相交流放电管新结构的再设计提供了理论依据和指导价值。

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引用次数: 0