International Journal of Thermal Sciences最新文献_第8页

Design of an air temperature monitoring instrument based on computational fluid dynamics and multi-layer perceptron neural network 基于计算流体力学和多层感知器神经网络的空气温度监测仪设计

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-05 DOI: 10.1016/j.ijthermalsci.2025.110652

Jie Yang , Yuan Chen , Guang You , Qingquan Liu , Jiale Jiang , Renhui Ding

Ground-based air temperature measurements are highly susceptible to solar and environmental long-wave radiation, often leading to temperature deviations of up to approximately 1 °C. This study proposes a low-uncertainty air temperature measurement instrument specifically designed to minimize such radiation-induced temperature deviations. Computational fluid dynamics (CFD) simulations were first performed to optimize the structural design of the instrument, thereby enhancing internal airflow and improving both radiation shielding efficiency and convective heat dissipation. Subsequently, the radiation-induced temperature deviations of the optimized structure were quantitatively analyzed under various environmental conditions. A multi-layer perceptron (MLP) neural network was then employed to develop a temperature deviation correction model using the CFD-generated dataset. Finally, field comparative experiments were conducted using a 076B aspirated temperature measurement instrument as a reference. Experimental results show that, before correction, the proposed instrument exhibited a maximum radiation-induced temperature deviation of 0.43 °C and a mean temperature deviation of 0.31 °C. The root mean square error (RMSE), mean absolute error (MAE), and correlation coefficient (r) between the experimental and predicted radiation-induced temperature deviations were 0.08 °C, 0.07 °C, and 0.99, respectively. After applying the correction model, the maximum radiation-induced temperature deviation decreased to 0.12 °C, and the mean deviation decreased to 0.02 °C, demonstrating excellent consistency. In conclusion, the proposed instrument achieves efficient ventilation and low-uncertainty temperature measurement without relying on mechanical components.

地面空气温度测量极易受到太阳和环境长波辐射的影响，常常导致温度偏差高达约1°C。本研究提出了一种专门设计的低不确定度空气温度测量仪器，以尽量减少这种辐射引起的温度偏差。首先进行了计算流体动力学（CFD）模拟，优化了仪器的结构设计，从而增强了内部气流，提高了辐射屏蔽效率和对流散热。随后，定量分析了优化后的结构在不同环境条件下的辐射温度偏差。然后利用多层感知器（MLP）神经网络利用cfd生成的数据集建立温度偏差校正模型。最后，以076B型吸式测温仪为参考，进行了现场对比实验。实验结果表明，校正前，该仪器的最大辐射温度偏差为0.43°C，平均温度偏差为0.31°C。实验温度偏差与预测温度偏差的均方根误差（RMSE）、平均绝对误差（MAE）和相关系数(r)分别为0.08°C、0.07°C和0.99。应用修正模型后，辐射引起的最大温度偏差减小到0.12°C，平均偏差减小到0.02°C，一致性很好。综上所述，该仪器在不依赖机械部件的情况下实现了高效通风和低不确定度的温度测量。

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引用次数: 0

Ultra-broadband thermal tunable plasmonic metamaterial absorber based on vanadium dioxide (VO2) from ultraviolet to near-infrared regime 基于紫外至近红外波段二氧化钒（VO2）的超宽带热调谐等离子体超材料吸收体

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-05 DOI: 10.1016/j.ijthermalsci.2026.110660

Ling Wu , Xia Cao , Can Cao , Bin Cai , Yongzhi Cheng

In this study, an ultra-broadband thermal tunable plasmonic metamaterial absorber (MMA) is proposed, operating across the ultraviolet to near-infrared spectral range. The unit-cell of the MMA is consisted of a nano-pyramid structure vanadium dioxide (VO₂) adhered on a tungsten (W) substrate. Numerical simulations utilizing the finite element method demonstrate that the proposed MMA achieves an absorbance over 90 % across from 250 nm to 1729.5 nm at room temperature (20 °C), with a relative bandwidth of 149.48 % and an average absorbance of 98.87 % within this wavelength range. In addition, the absorption peak reaches 99.71 %, 99.94 %, 99.98 %, and 99.81 % at 255 nm, 335 nm, 629 nm, and 1384 nm, respectively. The ultra-broadband strong absorption of the MMA at room temperature (20 °C) results from the excitation of waveguide resonances (WGRs), localized surface plasmon resonances (LSPRs), propagation surface plasmon resonances (PSPRs) and cavity resonances (CRs) modes along with coupling effects, and the intrinsic losses of VO₂ and W. The MMA also exhibits polarization insensitivity and supports wide incident angles for both TE and TM modes. The absorption performance of the MMA can be precisely adjusted by modifying the geometrical parameters of its unit-cell, showing some error tolerance during practical fabrication. Furthermore, the 90 % absorbance bandwidth of the MMA can be modulated dynamically by adjusting the external temperature. When the temperature is elevated from 20 °C to 70 °C, VO₂ experiences a phase transition, transforming into a metallic state. This remarkable change enables the MMA to sustain 90 % absorbance from 250 nm to 1152 nm, which corresponds to a relative bandwidth of 128.67 %. Due to its adjustable light absorption properties, the proposed MMA has potential applications in thermal imaging and solar energy harvesting devices.

在这项研究中，提出了一种超宽带热调谐等离子体超材料吸收器（MMA），工作在紫外到近红外光谱范围内。MMA的单元电池是由纳米金字塔结构的二氧化钒（VO2）附着在钨(W)衬底上组成的。利用有限元方法进行的数值模拟表明，在室温（20°C）下，所提出的MMA在250 nm至1729.5 nm范围内的吸光度超过90%，相对带宽为149.48%，平均吸光度为98.87%。在255 nm、335 nm、629 nm和1384 nm处的吸收峰分别达到99.71%、99.94%、99.98%和99.81%。MMA在室温（20°C）下的超宽带强吸收是由波导共振（wgr）、局域表面等离子体共振（LSPRs）、传播表面等离子体共振（PSPRs）和腔共振（CRs）模式的激发以及耦合效应以及VO2和w的本征损耗引起的。MMA还表现出极化不敏感性，支持TE和TM模式的宽入射角。通过改变其单元格的几何参数，可以精确地调整MMA的吸收性能，在实际制造过程中具有一定的误差容忍度。此外，MMA的90%吸光度带宽可以通过调节外部温度来动态调制。当温度从20℃升高到70℃时，VO2发生相变，变为金属态。这种显著的变化使MMA在250 nm至1152 nm范围内保持90%的吸光度，对应于128.67%的相对带宽。由于其可调节的光吸收特性，所提出的MMA在热成像和太阳能收集装置中具有潜在的应用前景。

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引用次数: 0

Comparative assessment of turbulence models for flow and heat transfer prediction in compressor interstage seals 用于压气机级间密封流动和传热预测的湍流模型的比较评估

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-05 DOI: 10.1016/j.ijthermalsci.2026.110663

Hao Liu , Guoqing Li , Chenyang Kang , Yunhong Ruan , Xingen Lu

The accurate prediction of complex flow and heat transfer in interstage labyrinth seals is crucial for safeguarding the performance of the high-pressure compressor in variable cycle engines. This study establishes a large-scale and multifunctional sealing test rig to acquire the overall performance of labyrinth seals under heat transfer conditions. To evaluate the capabilities of Reynolds-Averaged Navier-Stokes (RANS) based on k-ω model, Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), a systematic numerical investigation is conducted, followed by a comparative analysis of vortex dynamics, wall heat transfer, and entropy generation. Results show that DES and LES accurately capture the interaction between centrifugal force and centrifugal buoyancy. The evolution of coherent vortex structures, from shear layer instability at the fin tip to subsequent vortex stretching, interaction, and breakdown, governs the leakage processes. In contrast, RANS provides an overly smoothed flow field, and overestimates the core jet intensity, as it distorts key physical mechanisms and generates overly isotropic turbulence structures. Meanwhile, the peak Nusselt numbers are underestimated by up to 110 % on the rotor surface due to missing unsteady vortex-induced impingement. Entropy generation analysis reveals that RANS overestimates viscous losses while underestimating thermal losses. This study demonstrates that high-fidelity numerical simulation is indispensable for the analysis and design of compressor interstage seals, providing critical insights essential for improving the accuracy of turbulence models in advanced compressor systems.

准确预测级间迷宫密封的复杂流动和换热对保证变循环发动机高压压气机的工作性能至关重要。为了获得传热条件下迷宫密封的整体性能，建立了大型多功能密封试验台。为了评估基于k-ω模型、分离涡模拟（DES）和大涡模拟（LES）的reynolds -平均Navier-Stokes （RANS）的能力，进行了系统的数值研究，然后对涡旋动力学、壁面传热和熵生成进行了比较分析。结果表明，DES和LES能够准确地捕捉离心力和离心力之间的相互作用。从翼尖剪切层不稳定到随后的涡拉伸、相互作用和击穿，相干涡结构的演变控制着泄漏过程。相比之下，RANS提供了一个过于平滑的流场，并且高估了核心射流强度，因为它扭曲了关键的物理机制并产生了过度各向同性的湍流结构。同时，由于缺少非定常涡激碰撞，转子表面峰值努塞尔数被低估了110%。熵产分析表明，RANS高估了粘滞损失，而低估了热损失。该研究表明，高保真的数值模拟对于压缩机级间密封的分析和设计是必不可少的，为提高先进压缩机系统湍流模型的准确性提供了至关重要的见解。

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引用次数: 0

Heat transfer enhancement of circular-tube-fin heat exchangers: Optimal positioning and role of curved rectangular vortex generators 圆管翅片换热器的强化传热：弯曲矩形涡发生器的优化定位与作用

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-03 DOI: 10.1016/j.ijthermalsci.2025.110653

Wei Dang , Wenqiang Deng , Jian Song , Kewei Song

A systematic numerical investigation is conducted to examine the influence of curved rectangular vortex generator (CRVG) placement on the thermal performance of circular-tube-fin heat exchangers. Transverse, longitudinal, and circumferential offsets are considered to identify configurations that maximize heat transfer while maintaining acceptable flow resistance. The results show that a transverse offset of Δz = 1 mm achieves the best overall performance in the Reynolds number (Re) range from 400 to 5000, the Nusselt number (Nu) increases by up to 34.2 %, while performance evaluation criterion (JF) first increases and then decreases, reaching its maximum value of 1.32 at Re = 1000. A longitudinal offset of Δx = 2 mm yields a peak JF of 1.30. Circumferential placement exhibits the strongest influence. Here, Δβ represents the circumferential offset angle. The optimal circumferential position for heat transfer enhancement depends on Re, with the highest JF of 1.29 occurring at Δβ = 0° for Re = 1000, whereas Δβ = +15° yields a JF of 1.18 at Re = 2000, reflecting enhanced heat transfer performance at higher Re. A strong dependence of Nu on secondary flow intensity (Se) is also established, confirming that vortex-induced secondary flow is the key mechanism governing heat transfer augmentation. Furthermore, empirical correlations relating Nu, friction factor (f), and JF to Re and CRVG positioning parameters are developed, providing practical tools for preliminary design, performance assessment, and optimization of circular-tube-fin heat exchangers.

本文对矩形弯曲涡发生器（CRVG）的布置对圆管翅片换热器热性能的影响进行了系统的数值研究。横向，纵向和周向偏移被认为是确定最大限度地传热，同时保持可接受的流动阻力的配置。结果表明：当横向偏移Δz = 1 mm时，在雷诺数（Re）为400 ~ 5000的范围内获得了最佳的综合性能，努塞尔数（Nu）增加了34.2%，而性能评价准则（JF）先增大后减小，在Re = 1000时达到最大值1.32。纵向偏移Δx = 2 mm产生1.30的峰值JF。圆周位置的影响最大。这里，Δβ表示周向偏移角。强化换热的最佳周向位置取决于Re， Re = 1000时Δβ = 0°的JF最高，为1.29，而Re = 2000时Δβ = +15°的JF最高，为1.18，反映了高Re下的强化换热性能。Nu对二次流强度（Se）的依赖性也很强，证实了涡诱导二次流是强化换热的关键机制。此外，还建立了Nu、摩擦系数(f)和JF与Re和CRVG定位参数之间的经验相关性，为圆管翅片换热器的初步设计、性能评估和优化提供了实用工具。

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引用次数: 0

Experimental and numerical study on the turbulent natural convection in a large-scale vertical closed-duct heatsink 大型垂直闭式散热器湍流自然对流的实验与数值研究

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-03 DOI: 10.1016/j.ijthermalsci.2025.110656

Cheng-Pu Yang , Shwin-Chung Wong

This study pioneers the experimental measurement and numerical analysis for the turbulence-enhanced natural convection in a large-scale vertical closed-duct heatsink. Numerically, an 1800 mm tall square 60 × 60 mm² aluminum-alloy closed duct of an infinite-channel heatsink is examined using various Reynolds-averaged Navier-Stokes (RANS) turbulence models. These results are validated through comparison with the benchmark, the large-eddy simulation (LES) data and corresponding experimental data. In the LES results, a distinct vertical recirculation zone forms along the inner surface of the end plate when external cold air enters the closed duct inlet. This vertical recirculating flow region locally suppresses heat transfer, resulting in reduced airflow velocity and elevated temperatures near the wall and surrounding air. Conversely, the flow adjacent to the vertical recirculation zone experiences localized acceleration. At the upper part (y > 800 mm), air near the four corners is surprisingly accelerated due to the hotter walls. Near the outlet, the airflow accelerates due to buoyancy and results in a significant increase in the convective heat transfer coefficients. Furthermore, the closed-duct heatsink (CDHS) first exhibits a strong turbulent intensity associated with the inlet vertical recirculation zone. As the flow rises with buoyancy, the turbulent intensity first decreases due to viscosity but expands to a wider region with a similar value. All the above phenomena do not appear in studies on tall vertical flat plates, for which laminar flow first appears and the transition occurs at about Ra_H ∼10⁹. The simulation results indicate that the k-kl-ω model demonstrates the highest reliability among the evaluated turbulence models. Also, the LES model deviates from experimental data by −2.0 %. The k-kl-ω model not only closely aligns with the LES benchmark in both velocity and temperature profiles but also differs from the LES model by only −2.1 %. The k-kl-ω model effectively simulates the flow characteristics in the CDHS and reliably reflects the virtual chimney effect beyond the CDHS outlet. This study indicates that a computationally-efficient and time-saving RANS k-kl-ω model can be utilized for optimizing natural-convection heatsink design for large-scale devices, such as electric vehicle charging poles.

本研究首次对大型垂直闭式散热器湍流增强自然对流进行了实验测量和数值分析。在数值上，使用各种reynolds -平均Navier-Stokes （RANS）湍流模型对无限通道散热器的1800 mm高方形60 × 60 mm2铝合金封闭管道进行了研究。通过与基准、大涡模拟（LES）数据和相应的实验数据的对比，验证了上述结果。在LES结果中，当外部冷空气进入封闭管道入口时，沿端板内表面形成明显的垂直再循环区。这种垂直的再循环流动区域局部抑制了传热，导致气流速度降低，壁面附近和周围空气温度升高。相反，垂直再循环带附近的流体经历局部加速度。在上部（y >； 800毫米），由于热壁，四角附近的空气令人惊讶地加速。在出口附近，由于浮力的作用，气流加速，导致对流换热系数显著增加。此外，闭式管道散热器（CDHS）首先表现出与入口垂直再循环区相关的强湍流强度。当气流随浮力上升时，湍流强度首先由于黏性的作用而减小，然后扩展到更宽的区域，其数值相近。在高垂直平板上的研究中没有出现上述现象，在高垂直平板上首先出现层流，并且在RaH ~ 109左右发生转变。仿真结果表明，k-kl-ω模型在所评估的湍流模型中具有最高的可靠性。此外，LES模型与实验数据偏差为- 2.0%。k-kl-ω模型不仅在速度和温度曲线上与LES基准非常接近，而且与LES模型的差异仅为- 2.1%。k-kl-ω模型有效地模拟了CDHS内的流动特性，可靠地反映了CDHS出口外的虚拟烟囱效应。该研究表明，一种计算效率高且节省时间的RANS k-kl-ω模型可用于优化大型设备（如电动汽车充电杆）的自然对流散热器设计。

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引用次数: 0

Three-layer metamaterial solar absorber based on tungsten metal for broadband high absorption and high-temperature thermal radiation stability 基于钨金属的三层超材料太阳能吸收体，具有宽带高吸收和高温热辐射稳定性

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-01-01 DOI: 10.1016/j.ijthermalsci.2025.110648

Zhuocheng Xue , Shubo Cheng , Huafeng Zhang , Jun Zhu , Zao Yi

This study presents a novel three-layer metamaterial solar absorber design. The objective of this design is to overcome the technological limitations that currently exist and to encourage the practical application of photothermal conversion technology. The design utilizes titanium (Ti) cubes as the bottom substrate, leveraging its high hardness and corrosion resistance to provide structural support and long-term stability; the middle layer employs silicon dioxide (SiO₂) cubes, which augment multiple reflections and trapping of light within the structure by virtue of their low refractive indices and excellent thermal insulating properties. The uppermost layer is constituted by a hollow, symmetrical, pentagonal tungsten (W) structure. This structure, in conjunction with tungsten's elevated melting point and plasma resonance characteristics, facilitates high-efficiency absorption within the 200–2300 nm band. The hollow design reduces the amount of material used, thereby optimizing the cost. This study used finite difference method (FDTD) simulations to verify that the absorber exhibits an absorption rate exceeding 90 % in the 200–2300 nm wavelength range and maintains superior performance under various climatic conditions with incident angles from 0° to 60° and TM/TE polarization. Furthermore, its thermal properties were evaluated through simulations (573–1073 K), and cost-effective preparation methods were explored to promote its industrial application. This study offers novel concepts for the development of highly efficient, stable, and economically viable solar absorbers, thereby facilitating the large-scale promotion and industrialization of solar thermal technology.

提出了一种新型的三层超材料太阳能吸收体设计。本设计的目的是克服目前存在的技术限制，并鼓励光热转换技术的实际应用。该设计采用钛（Ti）立方体作为底部基材，利用其高硬度和耐腐蚀性提供结构支撑和长期稳定性；中间层采用二氧化硅（SiO2）立方体，凭借其低折射率和优异的隔热性能，增强了结构内的多次反射和光捕获。最上层由中空对称的五角形钨(W)结构构成。这种结构与钨的高熔点和等离子体共振特性相结合，促进了200-2300 nm波段内的高效吸收。中空的设计减少了材料的使用量，从而优化了成本。本研究利用有限差分法（FDTD）模拟验证了该吸收体在200 ~ 2300 nm波长范围内的吸收率超过90%，并且在入射角为0°~ 60°和TM/TE极化的各种气候条件下保持优异的性能。在573-1073 K范围内对其热性能进行了模拟评价，探索了经济高效的制备方法，促进了其工业应用。本研究为开发高效、稳定、经济可行的太阳能吸收剂提供了新概念，从而促进了太阳能热技术的大规模推广和产业化。

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引用次数: 0

Thermal-hydraulic performance and heat transfer modelling of partially filled periodic octet foam heat sinks 部分填充周期泡沫散热器的热工性能和传热模型

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.ijthermalsci.2025.110632

Nitin Hanuman Roge, Shankar Krishnan, S.V. Prabhu

The present study investigates the thermal and hydrodynamic performance of a heat sink channel partially filled with open-cell AlSi10Mg metal foam. Three configurations are considered

: H_{f} = 0.5 H

,

H_{f} = 0.75 H

and

H_{f} = H

, where

H_{f}

is the foam height and

H

is the height of the channel, and they are referred to as Cases 1, 2 and 3, respectively. The study examined over a Reynolds number range of 5000–25,000. The metal foam has a thickness of 12.5 mm and a porosity of 0.706. Wall temperature distributions are captured using a thin stainless steel foil coated with high-emissivity paint and measured through infrared thermography. Results show that reducing the foam height significantly decreases pressure drop, with the

0.5 H

configuration exhibiting a 10–12 times lower pressure drop than the fully filled case. However, there is a corresponding reduction in heat transfer. Thermal performance evaluation indicates that each configuration achieves a favourable

P E C

and

C P P C

values. To isolate the heat transfer mechanisms, complementary resin foam experiments demonstrate that nearly 80 % of the total heat transfer is contributed by the metal foam. A unified two-model analysis framework is introduced to quantify mass flow separation, heat transfer, and pressure drop in partially filled channels using structured foams: a behaviour not previously characterised in the literature. Using combined experimental measurements and analytical modelling, the study develops predictive relations capable of accurately estimating both thermal and hydrodynamic performance across porous bypass configurations. A generalised correlation is further proposed to estimate the Nusselt number for both gap and no-gap configurations, formulated using the Reynolds number based on the strut diameter and effective thermal properties. Together, these contributions provide the comprehensive predictive tools tailored specifically for structured lattice foam channels, enabling more reliable design and optimisation under practical heat-transfer and pressure-drop constraints.

本文研究了部分填充开孔AlSi10Mg金属泡沫的热沉通道的热学和流体力学性能。考虑Hf=0.5H、Hf=0.75H和Hf=H三种构型，其中Hf为泡沫高度，H为通道高度，分别称为情形1、情形2和情形3。该研究检查了5000 - 25000的雷诺数范围。金属泡沫的厚度为12.5 mm，孔隙率为0.706。利用涂有高发射率涂料的薄不锈钢箔捕获壁温分布，并通过红外热成像进行测量。结果表明，降低泡沫高度可显著降低压降，0.5H结构的压降比完全填充情况低10-12倍。然而，传热也有相应的减少。热性能评价表明，每种结构都达到了较好的PEC和CPPC值。为了隔离传热机制，互补树脂泡沫实验表明，近80%的总传热是由金属泡沫贡献的。引入了统一的双模型分析框架，以定量质量流分离，传热和压力降在部分填充的通道使用结构化泡沫：以前没有在文献中描述的行为。通过结合实验测量和分析建模，该研究建立了预测关系，能够准确估计多孔旁通配置的热性能和水动力性能。进一步提出了一个广义的相关性来估计间隙和无间隙构型的努塞尔数，使用基于支柱直径和有效热性能的雷诺数来表示。总之，这些贡献提供了专门为结构化晶格泡沫通道量身定制的综合预测工具，在实际传热和压降限制下实现更可靠的设计和优化。

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引用次数: 0

Entropy generation from a staggered array of surface dimples with heat transfer and a constant heat flux boundary condition 具有传热和恒定热流边界条件的交错表面凹窝阵列的熵生成

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.ijthermalsci.2025.110645

Phillip M. Ligrani, Mason Hancock, Preston McMahan, Mauro Guevara-Ramon, Emily Mecklenburg, Nathan Knox

Utilized within the present study is second law analysis as applied to experimentally-measured and numerically-predicted data within the turbulent boundary layers that develop along a constant heat flux test surface with an array of staggered dimples. Spatially-resolved second law results are provided over flow cross-sectional planes at different streamwise development locations, which are quantified using a characteristic temperature difference and freestream velocity. Considered are variations of entropy generation, as well as mass-averaged overall exergy destruction (both relative to freestream flow), as these quantities are determined using variations of local stagnation temperature only, variations of local flow stagnation pressure only, and stagnation pressure and stagnation temperature variations together. Resulting data provide detailed information on flow loss mechanisms which affect the thermal-fluid performance of surface dimples in augmenting surface heat transfer levels. Significant local variations of entropy generation and overall variations spatially-averaged exergy destruction are observed as spanwise-normal plane location, streamwise development location, freestream velocity, and characteristic temperature difference are altered. Additionally evident are gradients of local entropy generation from flow stagnation temperature, which are present near the surface beneath regions where local generation values are highest. These near-wall regions are associated with decreasing local flow temperatures, which are then locally lowest at the surface at the same locations where Nusselt numbers are locally augmented. Exergy destruction data based upon stagnation pressure consistently increase as freestream velocity becomes larger, with values that are 10–20 times lower relative to values based upon stagnation temperature only. Exergy destruction data values, based upon variations of stagnation temperature, and variations of stagnation temperature and stagnation pressure together, are higher by as much as 82 percent for ΔT = 15^oC, compared to data associated with ΔT = 10^oC. Responsible are a diversity of unsteady flow phenomena which originate due to the presence of individual dimple cavities, including secondary vortex pairs near dimple edges, primary vortex pairs shed from dimple central regions, and the shear layers which form across the top region of each dimple.

在本研究中，第二定律分析应用于实验测量和数值预测的湍流边界层数据，这些数据沿着具有交错凹窝阵列的恒定热通量测试表面发展。在不同流向发展位置的流动截面上提供了空间分辨的第二定律结果，并使用特征温差和自由流速度对其进行了量化。考虑到熵生成的变化，以及质量平均的总火能破坏（都相对于自由流），因为这些量仅使用局部停滞温度的变化，局部流动停滞压力的变化，以及停滞压力和停滞温度的变化来确定。所得数据提供了流动损失机制的详细信息，流动损失机制影响表面凹窝在增加表面传热水平时的热流体性能。熵产的局部变化显著，空间平均火能破坏的总体变化显著，如展向法向面位置、流向发育位置、自由流速度和特征温差发生变化。另外，流动停滞温度引起的局部熵产生的梯度也很明显，这种梯度在局部熵产生值最高的区域的地表附近。这些近壁区域与局部流动温度的降低有关，因此在努塞尔数局部增加的同一位置，表面的局部流动温度是最低的。随着自由流速度的增大，基于停滞压力的火能破坏数据持续增加，其值比仅基于停滞温度的值低10-20倍。与ΔT = 10℃的数据相比，基于停滞温度变化、停滞温度和停滞压力变化的火能破坏数据值在ΔT = 15℃时高出82%。不同的非定常流动现象是由单个凹窝腔的存在引起的，包括靠近凹窝边缘的二次涡对，从凹窝中心区域脱落的初级涡对，以及在每个凹窝顶部区域形成的剪切层。

{"title":"Entropy generation from a staggered array of surface dimples with heat transfer and a constant heat flux boundary condition","authors":"Phillip M. Ligrani, Mason Hancock, Preston McMahan, Mauro Guevara-Ramon, Emily Mecklenburg, Nathan Knox","doi":"10.1016/j.ijthermalsci.2025.110645","DOIUrl":"10.1016/j.ijthermalsci.2025.110645","url":null,"abstract":"<div><div>Utilized within the present study is second law analysis as applied to experimentally-measured and numerically-predicted data within the turbulent boundary layers that develop along a constant heat flux test surface with an array of staggered dimples. Spatially-resolved second law results are provided over flow cross-sectional planes at different streamwise development locations, which are quantified using a characteristic temperature difference and freestream velocity. Considered are variations of entropy generation, as well as mass-averaged overall exergy destruction (both relative to freestream flow), as these quantities are determined using variations of local stagnation temperature only, variations of local flow stagnation pressure only, and stagnation pressure and stagnation temperature variations together. Resulting data provide detailed information on flow loss mechanisms which affect the thermal-fluid performance of surface dimples in augmenting surface heat transfer levels. Significant local variations of entropy generation and overall variations spatially-averaged exergy destruction are observed as spanwise-normal plane location, streamwise development location, freestream velocity, and characteristic temperature difference are altered. Additionally evident are gradients of local entropy generation from flow stagnation temperature, which are present near the surface beneath regions where local generation values are highest. These near-wall regions are associated with decreasing local flow temperatures, which are then locally lowest at the surface at the same locations where Nusselt numbers are locally augmented. Exergy destruction data based upon stagnation pressure consistently increase as freestream velocity becomes larger, with values that are 10–20 times lower relative to values based upon stagnation temperature only. Exergy destruction data values, based upon variations of stagnation temperature, and variations of stagnation temperature and stagnation pressure together, are higher by as much as 82 percent for ΔT = 15<sup>o</sup>C, compared to data associated with ΔT = 10<sup>o</sup>C. Responsible are a diversity of unsteady flow phenomena which originate due to the presence of individual dimple cavities, including secondary vortex pairs near dimple edges, primary vortex pairs shed from dimple central regions, and the shear layers which form across the top region of each dimple.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110645"},"PeriodicalIF":5.0,"publicationDate":"2025-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881179","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

Analysis on microscopic characteristics of cathode spot ablation of vacuum contact under different interruption modes 不同中断方式下真空触点阴极点烧蚀的微观特征分析

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.ijthermalsci.2025.110610

Zhi Zhang , Si Fu , Zhengbo Li , Yundong Cao , Zhengkang Li , Jing Cao

As the primary source of metal vapor particles in vacuum arcs, cathode spots are fundamental to the control and regulation of arcs in vacuum interrupters. This study investigates the influence of contact rotation on the generation and evolution of cathode spots by simulating the formation of craters on a copper cathode surface under a constant current carried by a single basic cathode spot unit. To accurately reflect the impact of the vacuum arc on the contact, optical emission spectroscopy (OES) is employed to diagnose plasma parameters under different rotational speeds, determining electron temperature and electron density. The derived electron heat flux density is used to estimate the energy flux density received by a single cathode spot from the arc column, which serves as a boundary condition for modeling cathode spot formation and evolution at various rotation speeds. The three-dimensional model integrates fluid dynamics equations, heat transfer equations, and a modified level-set equation. The study explores cathode spot surface temperature, molten pool width, erosion volume, and droplet ejection behavior under different rotational interruption scenarios. Results show that direct-pull interruption causes more severe droplet splashing compared to rotational interruption. In the direct-pull case, splashed material at the molten pool edge forms a “serrated” morphology. With the introduction of rotation, surface erosion is alleviated, the velocity of droplet ejection from a single cathode spot increases, but the total droplet volume decreases. The splashed morphology transitions to a “ring-shaped” shape, and the overall erosion mass is reduced.

阴极点作为真空电弧中金属蒸气粒子的主要来源，是真空灭弧器控制和调节电弧的基础。本研究通过模拟一个基本阴极光斑单元在恒流作用下在铜阴极表面形成凹坑，研究了接触旋转对阴极光斑产生和演化的影响。为了准确反映真空电弧对接触的影响，利用发射光谱（OES）诊断不同转速下的等离子体参数，测定电子温度和电子密度。推导出的电子热流密度用于估计单个阴极光斑从电弧柱接收到的能量流密度，作为模拟阴极光斑在不同转速下形成和演化的边界条件。三维模型集成了流体动力学方程、传热方程和修正的水平集方程。研究了不同旋转中断情况下阴极点表面温度、熔池宽度、侵蚀体积和液滴喷射行为。结果表明，与旋转中断相比，直接拉动中断导致的液滴飞溅更为严重。在直接拉动的情况下，在熔池边缘溅落的材料形成“锯齿状”形态。随着旋转的引入，表面侵蚀得到缓解，单个阴极点喷射液滴的速度增加，但总液滴体积减小。溅射形态转变为“环形”形态，整体侵蚀质量减小。

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引用次数: 0

Analytical solution for calculating the three-dimensional transient temperature of a solid half-space heated by a spiral-shaped surface heat source 计算螺旋形表面热源加热固体半空间三维瞬态温度的解析解

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-12-31 DOI: 10.1016/j.ijthermalsci.2025.110654

Najib Laraqi

This article proposes an explicit analytical solution for determining the 3D transient temperature of a semi-infinite medium receiving a surface flux on a spiral-shaped strip. This solution is useful for several applications such as TPS devices or the assembly of cylindrical parts machined on a lathe, among others. The analytical developments are carried out until there is only one integral left to be performed numerically. This integral relates to the angular direction, which has limited integration bounds, and can be calculated very quickly using standard computing software. The results obtained using the proposed solution are in excellent agreement with those obtained from numerical modeling. The analytical calculation times are extremely short and avoid the need for numerical modeling, which requires long calculation times. Temperature plots and thermal maps are presented and analyzed.

本文提出了一种确定半无限介质在螺旋形带材上受表面磁通的三维瞬态温度的显式解析解。该解决方案适用于TPS设备或在车床上加工的圆柱形零件的组装等几种应用。一直进行解析式的发展，直到只剩下一个积分需要进行数值运算。该积分与角方向有关，积分界有限，可以用标准计算软件快速计算。所提出的解与数值模拟的结果吻合得很好。解析计算时间极短，避免了需要长计算时间的数值模拟。给出并分析了温度图和热图。

引用次数: 0