International Journal of Thermal Sciences最新文献_第6页

Manufacturing-constrained multi-objective optimization of diamond microchannel heat sinks via interpretable machine learning 基于可解释机器学习的金刚石微通道散热片制造约束多目标优化

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-29 DOI: 10.1016/j.ijthermalsci.2026.110729

Song Yang, Liang Du, Jin Yuan, Xinlong Zhao, Wenbo Hu, Zhaoyang Zhang, Hongxing Wang

Modern electronics are continually evolving toward miniaturization and high performance, posing significant challenges for chip-level thermal management under ultra-high heat flux (>1000 W/cm²). Conventional heat sinks are inadequate for these demands. Diamond microchannel heat sinks, leveraging diamond's exceptional thermal conductivity, offer a promising solution. However, the high hardness and cost of diamond lead to elevated manufacturing costs for such heat sinks. Consequently, the co-optimization of thermal-hydraulic performance and manufacturing costs presents a critical challenge. This study employed a machine-learning-based multi-objective optimization approach to design diamond microchannel heat sinks, simultaneously considering thermal-hydraulic performance and manufacturing objectives. An artificial neural network predicted the thermal-hydraulic performance, and a genetic algorithm then identified Pareto-optimal solutions. First, a thermal-hydraulic dual-objective optimization was conducted to analyze the trade-off between the maximum temperature and pressure drop. Subsequently, two manufacturing objectives (aspect ratio and cross-sectional area) were introduced, thereby formulating a manufacturing-constrained multi-objective optimization problem. The results demonstrated clear trade-offs among these four objectives on the Pareto front. One notable optimal solution achieves a 61.6 % reduction in material cost and an estimated 58 % decrease in fabrication difficulty with only a 20 % compromise in thermal-hydraulic performance. Thus, this work provides a systematic design methodology that successfully balances performance with manufacturability, paving the way for the scalable industrial adoption of diamond microchannel heat sinks.

现代电子产品不断向小型化和高性能发展，对超高热流密度（>1000 W/cm2）下的芯片级热管理提出了重大挑战。传统的散热器不足以满足这些需求。金刚石微通道散热片，利用金刚石卓越的导热性，提供了一个有前途的解决方案。然而，金刚石的高硬度和高成本导致这种散热器的制造成本上升。因此，热液性能和制造成本的协同优化提出了一个关键的挑战。本研究采用基于机器学习的多目标优化方法设计金刚石微通道散热器，同时考虑热工性能和制造目标。人工神经网络预测热工性能，遗传算法识别帕累托最优解。首先，进行了热-液双目标优化，分析了最高温度与压降之间的权衡关系。随后，引入了两个制造目标（纵横比和截面积），从而形成了一个制造约束的多目标优化问题。结果表明，在帕累托前线，这四个目标之间存在明显的权衡。一个值得注意的最佳解决方案实现了材料成本降低61.6%，制造难度降低58%，而热工性能仅降低20%。因此，这项工作提供了一种系统的设计方法，成功地平衡了性能和可制造性，为金刚石微通道散热器的可扩展工业应用铺平了道路。

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引用次数: 0

Experimental investigation on HFE-7100 flow boiling in aluminum open microchannels heat sink HFE-7100在铝开口微通道散热器内流动沸腾的实验研究

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-08 DOI: 10.1016/j.ijthermalsci.2026.110672

Liaofei Yin , Tianjun Qin , Wenhao Ma , Yi Ding , Yawei Xu

For thermal management of large heat-generating devices, aluminum heat sinks exhibit promising application prospects owing to their lightweight and corrosion-resistant properties. This research presents an experimental study of HFE-7100 flow boiling within an aluminum heat sink with large heating area featuring open microchannels. By incorporating visualizations of bubble dynamics and flow regime transitions, the heat transfer mechanisms in large-area open microchannels heat sink were elucidated. The study revealed that increasing the mass flux simultaneously enhanced both the average heat transfer coefficient (HTC) and the critical heat flux (CHF), while elevated inlet temperatures significantly improved heat removal capability under moderate to high heat flux conditions. Notably, a previously unreported two-phase flow regime was identified, characterized by wave-like periodic features, and was termed “surge flow”. The flow boiling regime underwent longitudinally a sequential evolution from bubbly flow to plug flow and finally to surge flow along the flow direction. Examining the localized thermal performance across various regions of the heat sink revealed that the HTC of the surge flow regime exceeded those of bubbly and plug flow patterns by as much as 117.1 % and 58.7 %, respectively. Furthermore, the CHF was observed when the surge flow occupied approximately 65.0 %–70.0 % of the flow passage in the heat sink.

在大型发热设备的热管理中，铝制散热片具有轻质、耐腐蚀的特点，具有广阔的应用前景。本研究对HFE-7100在具有开放微通道的大加热面积铝散热器内流动沸腾进行了实验研究。结合气泡动力学和流态转变的可视化，阐明了大面积开口微通道散热器的传热机理。研究表明，提高质量通量可以同时提高平均换热系数（HTC）和临界热流密度（CHF），而提高进口温度可以显著提高中高热流密度条件下的换热能力。值得注意的是，研究人员发现了一种以前未报道过的两相流，其特征是波浪状的周期性特征，并被称为“喘振流”。沿流动方向，流动沸腾型经历了从气泡流到塞流再到涌浪流的纵向顺序演化。通过对散热器各区域局部热性能的研究表明，浪涌流模式的HTC分别比气泡流模式和塞流模式高117.1%和58.7%。此外，当喘振流约占散热器流道的65.0% ~ 70.0%时，可以观察到CHF。

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引用次数: 0

Resolving inverse heat conduction problems based on space marching method with Gauss filter - An experimental validation 基于高斯滤波的空间推进法求解热传导逆问题的实验验证

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-22 DOI: 10.1016/j.ijthermalsci.2026.110693

Ruiqin Cheng , Hongchu Chen , Zitao Yu , Changnian Pu

The space marching method (SMM) is an effective approach for solving inverse heat conduction problems (IHCPs). It enables efficient prediction of surface heat flux and temperature using embedded temperature sensors, offering advantages such as computational speed, high effectiveness, and accuracy. However, the in-depth temperature measurements often contain noise, which can be amplified during the prediction process, leading to unstable results due to the ill-posed nature of IHCPs. To stabilize the problem, it is necessary to filter the noisy in-depth temperature data. The Gauss filter has been demonstrated through numerical simulations as a valid method for stabilizing noisy data when using SMM to solve IHCPs. However, the application of the space marching technique with the Gauss filter for solving IHCPs has not been experimentally validated. In this paper, an experimental setup based on electric heating is designed and implemented to validate the effectiveness of the method. Compared with the prediction results with other regularization parameters, the SMM prediction with the optimal regularization parameter significantly reduces the relative root mean square error (RRMSE), demonstrating that SMM with the Gauss filter can be effectively applied in engineering practice.

空间推进法是求解逆热传导问题的有效方法。它可以使用嵌入式温度传感器有效地预测表面热流密度和温度，提供计算速度，高效率和准确性等优势。然而，深度温度测量通常包含噪声，这些噪声在预测过程中会被放大，由于ihcp的不适定性，导致结果不稳定。为了稳定这一问题，有必要对有噪声的深度温度数据进行滤波。数值模拟结果表明，高斯滤波器是一种稳定含噪数据的有效方法。然而，利用高斯滤波的空间推进技术求解IHCPs尚未得到实验验证。本文设计并实现了一个基于电加热的实验装置，以验证该方法的有效性。与使用其他正则化参数的预测结果相比，采用最优正则化参数的SMM预测结果显著降低了相对均方根误差（RRMSE），表明采用高斯滤波器的SMM可以有效地应用于工程实践。

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引用次数: 0

A non-invasive microwave hyperthermia for breast cancer treatment: FEA-based multiphysics approach for optimizing thermal dosage 一种用于乳腺癌治疗的非侵入性微波热疗：基于有限元的多物理场方法优化热剂量

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-19 DOI: 10.1016/j.ijthermalsci.2026.110688

Anudev J. , Balakrishnan Shankar , Massimo Donelli , Sreedevi K. Menon

Microwave hyperthermia has emerged as a potential supplement therapy for cancer treatment. The treatment modality elevates the temperature of cancer cells within the therapeutic limit (40 °C–45 °C). This will help to enhance their receptiveness to conventional treatments such as chemotherapy and radiation therapy. Numerical simulation strategies are adopted in this paper to simulate the effects of electromagnetic radiation on cancer cells. Combining electromagnetics and transient thermal analyses through a multiphysics approach, the thermal effects of electromagnetic (EM) radiation on the target cells are studied. A pentagonal patch antenna resonating at 2.45 GHz has been specially designed for this purpose and analysed experimentally. To mimic the breast tissues, a multi-layered simulation model has been designed with various sections such as skin, fat, fibroglandular tissue and tumor, positioned at different depths from the skin. The thickness of each layer is provided based on the average physiological measurements. To assure proper energy concentration at the tumor region, the electric field intensity and specific absorption rate are quantified through electromagnetic simulations. Subsequently, thermal simulations are performed in ANSYS Icepak by varying the input power levels of the antenna from 3 W to 10 W, to examine the therapeutic temperature developed at the tumor region. The effectiveness of thermal dosage is quantified with cumulative equivalent minutes at 43 °C (CEM43). Multiple simulations are performed by assuming varied positions of the tumor from the skin level, providing varied power levels accordingly. The proposed system acquires a rise in temperature to hyperthermia levels from the base temperature at a maximum rate less than 0.32 °C/s. Across the tested power levels, system attains CEM43 = 60 minutes for various tumor depths with tumor SAR≤ 40 W/kg and skin SAR<4 W/kg, falls under exposure limits. The proposed pentagonal patch antenna achieves faster therapeutic heating (<60 s) than prior antenna designs at 2.45 GHz with optimized power for varying tumor depths, keeping the skin temperature within the permissible limits.

微波热疗已成为癌症治疗的潜在补充疗法。治疗方式将癌细胞的温度升高到治疗极限（40°C - 45°C）。这将有助于提高他们对化学疗法和放射疗法等传统疗法的接受能力。本文采用数值模拟策略模拟电磁辐射对癌细胞的影响。采用多物理场方法，结合电磁学和瞬态热分析，研究了电磁辐射对靶细胞的热效应。为此专门设计了一种谐振频率为2.45 GHz的五边形贴片天线，并进行了实验分析。为了模拟乳腺组织，设计了一个多层模拟模型，将皮肤、脂肪、纤维腺组织和肿瘤等不同部分放置在距离皮肤不同深度的位置。每一层的厚度是根据平均生理测量提供的。为了保证肿瘤区域的能量集中，通过电磁模拟对电场强度和比吸收率进行了量化。随后，在ANSYS Icepak中通过将天线的输入功率从3 W变化到10 W进行热模拟，以检测肿瘤区域的治疗温度。热剂量的有效性用43°C （CEM43）的累积等效分钟来量化。通过从皮肤水平假设肿瘤的不同位置，提供相应的不同功率水平，进行了多次模拟。所提出的系统以小于0.32°C/s的最大速率从基础温度获得温度上升到热疗水平。在所有测试功率水平下，系统在不同肿瘤深度下达到CEM43 = 60分钟，肿瘤SAR≤40 W/kg，皮肤SAR≤4 W/kg，均在暴露限值之内。所提出的五边形贴片天线在2.45 GHz下实现了更快的治疗加热（60秒），并针对不同的肿瘤深度优化了功率，使皮肤温度保持在允许的范围内。

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引用次数: 0

Gas transport modeling in confined graphitic nanopores under high pressure 高压条件下石墨纳米孔内气体输运模拟

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-13 DOI: 10.1016/j.ijthermalsci.2026.110671

Deng Yang , Chongwen Jiang , Kaidi Wan , Chun-Hian Lee

Gas transport through nanochannels is widespread in both natural and industrial systems and is critical for the design of advanced porous materials. While Knudsen theory is traditionally used to describe this regime, its assumption of fully diffuse reflections fails for graphite-based nanopores, where atomically smooth surfaces promote specular scattering. High-pressure adsorption layers further alter scattering and flow behavior, yet quantitative models that incorporate both effects remain limited. In this study, molecular dynamics simulations are employed to investigate gas transport in graphitic slit nanopores. Gas-solid collisions follow the Cercignani-Lampis-Lord (CLL) model on smooth surfaces, whereas adsorption layers introduce partial diffuse reflection. To quantify the resulting deviations from ideal CLL behavior, we propose a linear-combination scattering framework and develop a semi-empirical tangential momentum accommodation coefficient (TMAC) model. Building upon this framework, new permeability and mass flow rate models are established that incorporate dense gas behavior and confinement effects. Simulation results reveal that the velocity profile within slit nanopores tends toward a plug-like shape, with flow rates enhanced by one to three orders of magnitude compared to no-slip Poiseuille flow. The presence of adsorption layers impedes molecular motion, and the ability of gas molecules to overcome this resistance is directly related to temperature. Compared with conventional models developed for inorganic porous media, the proposed model accurately captures the distinct gas transport behavior along graphitic surfaces. These findings offer valuable guidance for the development and utilization of carbon aerogels and, more broadly, for understanding mass transport in carbon-based nanoporous materials.

通过纳米通道的气体传输在自然和工业系统中都很普遍，对于设计先进的多孔材料至关重要。虽然Knudsen理论传统上用于描述这种情况，但其完全漫反射的假设对于石墨基纳米孔来说是失败的，因为石墨基纳米孔的原子光滑表面促进了镜面散射。高压吸附层进一步改变了散射和流动行为，但结合这两种影响的定量模型仍然有限。在本研究中，采用分子动力学模拟方法研究了石墨狭缝纳米孔中的气体输运。在光滑表面上，气固碰撞遵循Cercignani-Lampis-Lord （CLL）模型，而吸附层则引入部分漫反射。为了量化与理想CLL行为的偏差，我们提出了一个线性组合散射框架，并建立了一个半经验切向动量调节系数（TMAC）模型。在此基础上，建立了考虑致密气体行为和约束效应的新型渗透率和质量流量模型。模拟结果表明，狭缝纳米孔内的速度分布倾向于柱塞形状，与无滑移泊泽维尔流动相比，流速提高了1 ~ 3个数量级。吸附层的存在阻碍了分子的运动，气体分子克服这种阻力的能力与温度直接相关。与传统的无机多孔介质模型相比，该模型准确地捕捉了石墨表面独特的气体输运行为。这些发现为碳气凝胶的开发和利用提供了有价值的指导，更广泛地说，为理解碳基纳米多孔材料的质量传输提供了指导。

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引用次数: 0

Enhanced heat transfer using CuO+ZnO-water hybrid nanofluid with helical coil inserts in double pipe heat exchanger: Performance analysis and correlation development CuO+ zno -水混合纳米流体在双管换热器中的强化传热：性能分析及相关研究进展

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-13 DOI: 10.1016/j.ijthermalsci.2025.110650

Brajesh Kumar Ahirwar , Arvind Kumar

The growing need for efficient thermal management has spurred extensive research into enhancing heat exchanger performance. Among emerging methods, nanofluids—especially hybrid variants—have shown significant potential due to their superior thermal properties. This study explores the thermal performance of CuO + ZnO-water hybrid nanofluids in a double-pipe heat exchanger (DPHE) equipped with wire coil inserts as a passive enhancement technique. Hybrid nanofluids were prepared using CuO and ZnO nanoparticles at three volume concentrations: 1.0 % (80:20), 0.5 % (60:40), and 0.1 % (40:60). These fluids were tested over a Reynolds number range of 5500–15000 with wire coil inserts of varying diameters (1.0 mm, 1.5 mm, 2.0 mm) and pitch ratios (0.625–3.125). Results demonstrated that the highest heat transfer performance was achieved using 1.0 % CuO: ZnO (80:20) with a 2.0 mm wire diameter and tightest pitch ratio (0.625), yielding a Nusselt number increase of up to 281.87 % over water. While the friction factor also rose—leading to a maximum pressure drop penalty of 600.72 %—the thermal performance factor (TPF) remained favourable, ranging from 1.61 to 1.74. Lower concentrations and alternate compositions showed moderate performance improvements. Empirical correlations for Nusselt number and friction factor were developed, with predictive deviations within ±10 % of experimental values, confirming their reliability. This comprehensive analysis highlights the synergistic benefits of hybrid nanofluids and optimized wire coil geometries, offering valuable insights for the design of high-efficiency, compact heat exchangers in advanced thermal systems.

对高效热管理的日益增长的需求刺激了对提高热交换器性能的广泛研究。在新兴的方法中，纳米流体-特别是混合变体-由于其优越的热性能而显示出巨大的潜力。本文研究了CuO + zno -水混合纳米流体在双管换热器（DPHE）中的热性能，该换热器采用线圈插入作为被动增强技术。采用体积浓度分别为1.0%（80:20）、0.5%（60:40）和0.1%（40:60）的氧化铜和氧化锌纳米颗粒制备了杂化纳米流体。在5500-15000的雷诺数范围内对这些流体进行了测试，并使用了不同直径（1.0 mm、1.5 mm、2.0 mm）和节距比（0.625-3.125）的线圈插入。结果表明，当CuO: ZnO比例为1.0%(80:20)，线径为2.0 mm，节距比为0.625时，传热性能最佳，努塞尔数比在水中增加281.87%。虽然摩擦系数也有所上升，导致最大压降损失达到600.72%，但热性能系数（TPF）仍然保持良好，范围在1.61至1.74之间。较低浓度和替代成分表现出适度的性能改善。Nusselt数和摩擦因子的经验相关性得到了发展，预测偏差在实验值的±10%以内，证实了其可靠性。这项综合分析强调了混合纳米流体和优化线圈几何形状的协同效益，为先进热系统中高效、紧凑的热交换器的设计提供了有价值的见解。

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引用次数: 0

Numerical investigation on heat transfer and flow characteristics of triply periodic minimal surface in transpiration cooling 蒸腾冷却中三周期极小面传热与流动特性的数值研究

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-08 DOI: 10.1016/j.ijthermalsci.2026.110666

Zeyu Zhang , Yong Song , Zhi Tao , Liming Song , Jun Li

Transpiration cooling has been proved to act as the next generation cooling technology. The Triply Periodic Minimal Surface (TPMS) structures are the newly developed porous medium with superior mechanical and thermal properties. However, an in-depth understanding of the TPMS applied in the transpiration cooling remains insufficient. In this work, a numerical investigation is established to extract the detailed information of the aerodynamic and thermal mechanisms. Four commonly used TPMS structures, P, W, G and D are compared comprehensively in terms of cooling efficiency, temperature uniformity and pressure cost. The effect of blowing ratios ranging from 0.45 % to 3.3 % and solid porosities from 0.3 to 0.5 on different structures is also investigated. The result turns out that the average cooling efficiency increases monotonously from around 0.43 to 0.96 with blowing ratio with a gradually slowing rate. The cooling behavior usually improves with decreased porosity because of better protection of coolant film. The integrated cooling performance combined with pressure cost is also discussed and found to get good grades with high blowing ratio and porosity. The structure G and D achieves superior cooling performance because of the continuous protective film attachment and highly distorted inner surface. The P structure ensures excellent temperature uniformity attributes to the minimum heat conduction resistance and velocity uniformity. But the intense vortex derived from fluid expansion and contraction causes high pressure cost and dissipation. By integrating these results, this study reveals the underlying thermofluidic mechanisms and establishes performance trends that can inform the preliminary selection of different structures.

蒸腾冷却已被证明是下一代冷却技术。三周期最小表面（TPMS）结构是近年来发展起来的具有优异力学性能和热性能的多孔介质。然而，对TPMS在蒸腾冷却中的应用还缺乏深入的了解。在这项工作中，建立了一个数值研究，以提取空气动力和热机制的详细信息。从冷却效率、温度均匀性和压力成本等方面对P、W、G、D四种常用TPMS结构进行了综合比较。研究了吹气率为0.45% ~ 3.3%，固体孔隙率为0.3 ~ 0.5对不同结构的影响。结果表明：随着吹气比的增加，平均冷却效率从0.43左右单调增加到0.96，且速度逐渐减慢；由于冷却液膜得到更好的保护，孔隙率越低，冷却性能越好。并结合压力成本对综合冷却性能进行了讨论，发现高吹风比、高气孔率可以获得良好的性能。结构G和D由于连续的保护膜附着和高度变形的内表面而具有优越的冷却性能。P结构确保了优异的温度均匀性，这归功于最小的导热电阻和速度均匀性。但由于流体膨胀和收缩而产生的强烈涡流造成了很高的压力代价和耗散。通过整合这些结果，本研究揭示了潜在的热流体机制，并建立了性能趋势，可以为不同结构的初步选择提供信息。

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引用次数: 0

Strategic partial silver nanoparticles coating in enhancement of heat Sink's thermal performance 战略性局部纳米银涂层增强散热器热性能

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-10 DOI: 10.1016/j.ijthermalsci.2026.110679

Xing Qi Lim , Mohd Sharizal Abdul Aziz , C.Y. Khor

This study investigates the potential of a partially applied silver nanoparticle (AgNP) coating to enhance the thermal dissipation performance of the heat sink. Since the fully coated heat sink only showed marginal enhancement in the previous study, the heat sink is now partially coated on different surfaces. The simulation is completed using the ANSYS FLUENT software, and the accuracy of the setup is verified with an error percentage of less than 4 %. The heat sink with a front face coated (C3-AgNP) records the highest average overall heat transfer coefficient of 6.15379 W m⁻² K⁻¹, which is 1.141 % higher than the uncoated heat sink and 0.944 % better than the fully-coated (C1234-AgNP) heat sink. The C3-AgNP heat sink requires only a 5.4 mm³ AgNP coating, which is 96.655 % less than the 161.44 mm³ coating used by the C1234-AgNP heat sink. Although the presence of AgNP coating has adverse effects on the radiation heat loss of the heat sink, it enhances the heat dissipation process by facilitating heat flow from hotter regions to cooler regions. The AgNP coating promotes temperature uniformity in the heat sink, enabling greater heat loss through convection. This study reveals the possibility of unleashing the full potential of a coated heat sink through partial coating. It also contributes a solution for combining two or more different coatings, thereby optimizing heat sink performance in thermal management applications.

本研究探讨了部分镀银纳米粒子（AgNP）涂层增强散热器散热性能的潜力。由于完全涂覆的散热器在之前的研究中仅表现出边际增强，因此现在将散热器部分涂覆在不同的表面上。利用ANSYS FLUENT软件完成了仿真，验证了该装置的精度，误差小于4%。前表面涂层（C3-AgNP）的平均总换热系数最高，为6.15379 W m−2 K−1，比未涂层的散热器高1.141%，比全涂层（C1234-AgNP）的散热器高0.944%。C3-AgNP散热器只需要5.4 mm3的AgNP涂层，比C1234-AgNP散热器使用的161.44 mm3涂层少96.655%。虽然AgNP涂层的存在对散热器的辐射热损失有不利影响，但它通过促进热量从较热区域流向较冷区域来增强散热过程。AgNP涂层促进了散热器的温度均匀性，通过对流实现了更大的热损失。这项研究揭示了通过部分涂层释放涂层散热器全部潜力的可能性。它还为组合两种或多种不同的涂层提供了解决方案，从而优化了热管理应用中的散热器性能。

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引用次数: 0

Flow and transport characteristics in the entrance region of Poiseuille-Rayleigh-Bénard double diffusive convection of binary fluid in a horizontal channel 水平通道中二元流体poiseuille - rayleigh - bassariard双扩散对流入口区流动输运特征

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-09 DOI: 10.1016/j.ijthermalsci.2026.110675

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

To understand the flow and transport characteristics in the entrance region of Poiseuille-Rayleigh-Bénard (P-R-B) double diffusive convection within horizontal channel, a series of three-dimensional numerical simulations are conducted to assess the impact of aspect ratio (B), Reynolds number (Re), buoyancy ratio (N), and Rayleigh number (Ra), with the following ranges: 1≤B ≤ 10, 0≤Re ≤ 25, −0.3≤N ≤ 0.3, and 40≤Ra≤1.2 × 10⁵. The results indicate that the vertical velocity exhibits periodic sinusoidal fluctuations in both space and time as transverse rolls (TRs) develop. The amplitude of these fluctuations increases with Ra and N, while the fundamental frequency decreases as N rises. In the presence of longitudinal rolls (LRs), the vertical velocity is symmetrically distributed in the spanwise direction. If LRs do not fully develop in the entrance region, the vertical velocity will not form regular periodic fluctuations. When stable TRs occupy the entrance region, both temperature and concentration fields fluctuate sinusoidally over time with identical fundamental frequency. Correspondingly, Nusselt (Nu) and Sherwood (Sh) numbers show sinusoidal variations in the streamwise direction, and their amplitudes increase with Ra and N. Moreover, for LRs, the entrance lengths for the onset of secondary flow (L₁) and for its full development (L₂) decrease with Ra and N, but increase with Re and B. Meanwhile, at high Ra or large positive N, the reductions of L₁ and L₂ become less pronounced. In addition, the overall transport performance is not improved monotonically with increasing B. Based on simulation data, correlations for L₁ and L₂ were proposed. Ultimately, the thermal and solute transport correlations including the entrance region were also derived. These findings provide a theoretical foundation for the dimensional design of chemical reactors, heat and mass transfer equipment, and other systems involving P-R-B double diffusive convection.

为了了解水平通道内poiseuille -Rayleigh- b 运输运输（P-R-B）双扩散对流入口区域的流动和输运特征，对展弦比(B)、雷诺数（Re）、浮力比(N)和瑞利数（Ra）的影响进行了一系列三维数值模拟，范围为：1≤B≤10,0≤Re≤25,- 0.3≤N≤0.3,40≤Ra≤1.2 × 105。结果表明，随着横辊的发展，垂直速度在空间和时间上都表现出周期性的正弦波动。这些波动的幅度随着Ra和N的增大而增大，而基频则随着N的增大而减小。在存在纵辊的情况下，垂直速度沿展向对称分布。如果LRs在入口区域没有充分发育，垂向速度就不会形成规律的周期性波动。当稳定TRs占据入口区域时，温度场和浓度场都以相同的基频随时间呈正弦波动。Nusselt （Nu）和Sherwood （Sh）数值在流向上呈正弦变化，其幅值随Ra和N的增大而增大。对于LRs来说，二次流起始和完全发展的入口长度随Ra和N的增大而减小，而随Re和b的增大而增大。在高Ra或大正N时，L1和L2的减小不明显。此外，整体传输性能并不是随着b的增加而单调提高。基于仿真数据，提出了L1和L2的相关性。最后，导出了包括入口区在内的热输运和溶质输运的相关关系。这些发现为化学反应器、传热传质设备和其他涉及P-R-B双扩散对流的系统的尺寸设计提供了理论基础。

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引用次数: 0

Thermal transport of GaN/substrate heterostructures under non-uniform heat source 非均匀热源下氮化镓/衬底异质结构的热输运

IF 5 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2026-06-01 Epub Date: 2026-01-12 DOI: 10.1016/j.ijthermalsci.2026.110669

Ershuai Yin, Wenzhu Luo, Lei Wang, Enjian Sun, Qiang Li

Heat in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) is typically generated as highly localized nanoscale hot spots and dissipates through GaN/substrate heterostructures, yet the impact of non-uniform heating on heterostructure thermal transport remains unclear. This work aims to elucidate the thermal transport mechanisms of GaN/substrate heterostructures under non-uniform heat sources. A heterostructure thermal transport model is developed by combining first-principles calculations with Monte Carlo simulations. The effects of heterostructure height, heat source width, and heat source height on thermal transport characteristics are analyzed for four typical GaN/substrate heterostructures: GaN/AlN, GaN/Diamond, GaN/Si, and GaN/SiC. The results show that non-uniform heating has only a minor effect on the average interfacial thermal conductance. However, it induces pronounced spatial non-uniformity when the heterostructure height is small, with substantially higher conductance near the hot-spot region. Increasing heat-source non-uniformity substantially elevates the total thermal resistance, reaching several times the value obtained under uniform heating. In contrast, conventional finite-element method significantly underestimates the total thermal resistance because it cannot capture the coupled effects of localized heating and size-dependent thermal transport. The findings can provide theoretical guidance for the thermal design and reliability assessment of GaN semiconductor devices.

氮化镓（GaN）高电子迁移率晶体管（hemt）中的热量通常以高度局域化的纳米级热点产生，并通过GaN/衬底异质结构耗散，但不均匀加热对异质结构热输运的影响尚不清楚。本工作旨在阐明氮化镓/衬底异质结构在非均匀热源下的热输运机制。将第一性原理计算与蒙特卡罗模拟相结合，建立了异质结构热输运模型。分析了GaN/AlN、GaN/Diamond、GaN/Si和GaN/SiC四种典型GaN/衬底异质结构的异质结构高度、热源宽度和热源高度对热输运特性的影响。结果表明，非均匀加热对平均界面导热系数的影响较小。然而，当异质结构高度较小时，热区附近的电导高得多，会引起明显的空间非均匀性。热源不均匀性的增加大大提高了总热阻，达到均匀加热时的数倍。相比之下，传统的有限元方法明显低估了总热阻，因为它不能捕捉局部加热和尺寸相关热输运的耦合效应。研究结果可为GaN半导体器件的热设计和可靠性评估提供理论指导。

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引用次数: 0