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Thermal management of server with discrete power elements by localized cold plate enhanced single-phase immersion cooling and its orthogonal optimization 离散电源服务器局部冷板增强单相浸没冷却热管理及其正交优化
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-06-01 Epub Date: 2026-01-10 DOI: 10.1016/j.ijthermalsci.2026.110676
Yueting Zhou, Meiyan Xiong, Zhenwei Liu, Boyuan Wang, Feng Cao, Ping Li
The thermal management challenge of modern servers is recognized to arise from highly non-uniform power densities. In this study, a single-phase immersion and cold plate hybrid cooling method is employed to address the cooling of discretely distributed server elements with different power. Three-dimensional steady-state Reynolds-averaged Navier-Stokes simulations with conjugate heat transfer are performed to evaluate the thermal behavior of a complete one-unit server. Five coolant flow configurations are examined and their orientations relative to gravity are evaluated. The effects of coolant temperatures and flow rates as well as immersion liquid conditions are quantified through a systematic parametric analysis and an orthogonal design method. The dual inlet and dual outlet configuration provides the best temperature uniformity for the central processing unit. The inlet temperature of coolant is identified as the dominant factor for the maximum temperature of central processing units, while the overall temperature difference is mainly governed by the cooling configuration arrangement and the coolant flow rate. The temperature of low power elements is controlled primarily by the inlet temperature of the immersion liquid. A maximum temperature difference of 1.34 K is obtained for the platform controller hub. A reduction of 62.98 % compared with related work is demonstrated, and superior temperature uniformity is shown to be achieved by the proposed system. The combined cooling strategy is shown to maintain low temperature gradients across discrete power elements and is expected to provide theoretical support for the design of thermal management systems in modern servers.
现代服务器的热管理挑战被认为是由高度不均匀的功率密度引起的。本研究采用单相浸没和冷板混合冷却的方法来解决不同功率的离散分布服务器元件的冷却问题。采用三维稳态reynolds -average Navier-Stokes共轭传热模拟方法,对一个完整的单单元伺服器的热行为进行了评价。研究了五种冷却剂流动结构,并对其相对于重力的方向进行了评估。通过系统的参数分析和正交设计方法,量化了冷却剂温度、流量和浸泡液条件的影响。双入口双出口配置为中央处理器提供了最佳的温度均匀性。确定冷却剂进口温度是中央处理机组最高温度的主导因素,而整体温差主要受冷却配置布置和冷却剂流量的支配。低功率元件的温度主要由浸入液的入口温度控制。平台控制器集线器最大温差为1.34 K。与相关工作相比,该系统降低了62.98%,并取得了良好的温度均匀性。该组合冷却策略被证明可以保持离散电源元件的低温梯度,并有望为现代服务器热管理系统的设计提供理论支持。
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引用次数: 0
Development of spaceborne blackbody for Advanced Geostationary Radiation Imager (AGRI) 先进地球静止辐射成像仪(AGRI)星载黑体研制
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-06-01 Epub Date: 2026-01-21 DOI: 10.1016/j.ijthermalsci.2026.110705
Jingjing Zhou , Jian Song , Xiuju Li , Chunyuan Xu , Ruiheng Sima , Xin Xu , Changdao Guo , Xiaopeng Hao
To meet the requirements for a spaceborne blackbody with high emissivity, uniformity, and stability under complex thermal conditions, a simulation of cavity blackbody emissivity was performed using the Monte Carlo method. Additionally, an innovative structural design for the blackbody was proposed, incorporating a four-pyramid array, threadline array, and high-emissivity coating. Considering the on-orbit operational conditions of the spaceborne blackbody, finite element analysis was employed to simulate and calculate the thermal uniformity of the blackbody at 300 K and 320 K under three thermal conditions: low, medium, and high temperatures. Experimental validation of the results was also conducted. The spectral emissivity of the spaceborne blackbody was measured in the wavelength range of (3.5–15.0) μm, with an average normal emissivity of 0.9964. The difference between the normal emissivity and the emissivity at a 3° angle was 0.0012. Temperature uniformity and stability tests were conducted on the spaceborne blackbody within a temperature range of (300–320) K. The temperature uniformity at the bottom was 0.145 K, the overall temperature uniformity was 0.156 K, and the temperature stability was 0.012 K. The combined standard uncertainty of the blackbody is 0.135 K @ 300 K, 0.156 K @ 305 K, 0.174 K @ 310 K, 0.189 K @ 315 K, 0.198 K @ 320 K. Compared with the previous blackbody, the blackbody structural design proposed in this paper significantly improves the emissivity and temperature control performance.
为了满足星载黑体在复杂热条件下具有高发射率、均匀性和稳定性的要求,采用蒙特卡罗方法对空腔黑体发射率进行了模拟。此外,提出了一种创新的黑体结构设计,包括四金字塔阵列、线阵和高发射率涂层。考虑星载黑体在轨运行条件,采用有限元分析方法模拟计算了低、中、高温三种热工况下黑体在300 K和320 K时的热均匀性。并对实验结果进行了验证。测量了星载黑体在(3.5 ~ 15.0)μm波长范围内的光谱发射率,平均法向发射率为0.9964。法向发射率与3°角发射率之差为0.0012。对星载黑体在(300-320)K温度范围内进行温度均匀性和稳定性试验,底部温度均匀性为0.145 K,整体温度均匀性为0.156 K,温度稳定性为0.012 K。黑体的综合标准不确定度分别为0.135 K @ 300 K、0.156 K @ 305 K、0.174 K @ 310 K、0.189 K @ 315 K、0.198 K @ 320 K。与以往的黑体相比,本文提出的黑体结构设计显著提高了发射率和温度控制性能。
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引用次数: 0
Experimental and numerical study of flow and heat transfer of non-Newtonian power-law drilling fluids in helical tubes 非牛顿幂律钻井液在螺旋管内流动与传热的实验与数值研究
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-06-01 Epub Date: 2026-01-28 DOI: 10.1016/j.ijthermalsci.2026.110726
Yixuan Yuwen , Jingzhi Zhou , Yuzhe He , Kai Zhang , Xunfeng Li
The flow and heat transfer characteristics of non-Newtonian power-law drilling fluids in helical tubes were investigated through combined experimental and numerical methods. The effects of fluid density, rheological parameters (consistency index K and power-law index n), and helical tube curvature ratio were systematically analyzed. The results indicate that lower fluid density and higher inlet temperature both enhance heat transfer performance. Reductions in K and n synergistically enhance convective heat transfer while simultaneously lowering flow resistance. Moreover, increasing the curvature ratio not only improves thermal-hydraulic performance but also amplifies the effect of K and n. Based on the experimental and numerical data, a friction factor correlation incorporating the effects of the Dean number, curvature ratio, and power-law index was developed, along with a corresponding predictive model for the Nusselt number. These findings provide valuable theoretical guidance for the engineering application and optimized design of power-law fluids in helical tube heat exchangers.
采用实验与数值相结合的方法,研究了非牛顿幂律钻井液在螺旋管内的流动与传热特性。系统分析了流体密度、流变参数(稠度指数K和幂律指数n)和螺旋管曲率比的影响。结果表明,较低的流体密度和较高的进口温度均能提高换热性能。K和n的减少协同增强对流换热,同时降低流动阻力。此外,增加曲率比不仅可以改善热压性能,还可以放大K和n的影响。基于实验和数值数据,建立了考虑Dean数、曲率比和幂律指数影响的摩擦系数相关性,并建立了相应的努塞尔数预测模型。这些研究结果为幂律流体在螺旋管换热器中的工程应用和优化设计提供了有价值的理论指导。
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引用次数: 0
Spreading thermal transport in GaN nanostructures: Impact of interface and size induced anisotropy on effective thermal conductivity 氮化镓纳米结构中的扩散热输运:界面和尺寸诱导的各向异性对有效导热系数的影响
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-06-01 Epub Date: 2026-01-16 DOI: 10.1016/j.ijthermalsci.2026.110695
Xingji Chen , Xuqi Sheng , Daosheng Tang
Thermal spreading in GaN nanostructures is governed by the coupled effects of ballistic-diffusive phonon transport, interfacial mismatch, and mismatch-induced stress, yet these mechanisms are seldom treated in an integrated manner. Here, we develop a unified molecular-dynamics framework, combined with a PSO-based inverse method, to quantify the effective thermal conductivity of GaN under spreading heat flow. We uncover a key finding that the spreading thermal conductivity can exceed that of a single-layer GaN because introducing a heterogeneous interface transforms the bottom boundary from fully absorbing to partially transmitting, allowing ballistic phonons to bypass the dissipation bottleneck. Spreading transport also induces strong anisotropy that differs from 1-D BTE predictions due to multidimensional flux divergence. By introducing stress-relieved reference cases through substrate lattice-constant adjustment, we assess the relative contributions of interfacial structure and mismatch-induced stress, showing that structural mismatch governs GaN/Si, stress dominates GaN/SiC, and both contributions are comparable in GaN/AlN. Vibrational density of states and stress-mapping analyses reveal that interfaces generate nonuniform phonon environments inside GaN, offering an internal mechanism for conductivity reduction. These results clarify interface-modulated thermal transport in GaN and provide guidance for co-optimizing interface structure and strain in high-power GaN devices.
氮化镓纳米结构中的热扩散是由弹道扩散声子输运、界面失配和失配引起的应力的耦合效应控制的,但这些机制很少以综合的方式处理。在这里,我们开发了一个统一的分子动力学框架,结合基于粒子群算法的逆方法,来量化氮化镓在扩散热流下的有效导热系数。我们发现了一个关键的发现,即扩散热导率可以超过单层氮化镓的热导率,因为引入异质界面将底部边界从完全吸收转变为部分透射,允许弹道声子绕过耗散瓶颈。由于多维通量散度,扩散输运还会引起与一维BTE预测不同的强各向异性。通过引入衬底晶格常数调整的应力消除参考案例,我们评估了界面结构和错配引起的应力的相对贡献,表明结构错配支配GaN/Si,应力支配GaN/SiC,两者的贡献在GaN/AlN中具有可比性。态的振动密度和应力映射分析表明,界面在GaN内部产生非均匀声子环境,提供了电导率降低的内部机制。这些结果阐明了氮化镓中的界面调制热输运,并为高功率氮化镓器件中界面结构和应变的协同优化提供了指导。
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引用次数: 0
Study on the performance of thermoelectric generator with topology-optimized heat sinks 具有拓扑优化散热器的热电发电机性能研究
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-22 DOI: 10.1016/j.ijthermalsci.2025.110621
Liyao Xie , Zhaowei He , Aleksi Mankonen , Wei Wang , Yulong Zhao
This study proposes a three-dimensional topology optimization strategy for the structural design of passive cooling heat sinks in thermoelectric generator (TEG)-based waste heat recovery systems. The optimization objective focuses on minimizing the average temperature on the cold side of the TEG, thereby enhancing natural convection cooling and improving the power output and conversion efficiency of the system. The results demonstrate that the topology-optimized heat sink enhances natural convection by promoting interaction between the fins and airflow, significantly reducing the average temperature on the cold side of the TEG and improving the system's thermoelectric performance. Quantitatively, the 3D topology-optimized heat sink outperforms conventional straight-fin designs, increasing output power by 27.9 % and thermoelectric conversion efficiency by 14.5 %. Furthermore, flow field analysis using the Q-criterion reveals enhanced vortex structures and airflow mixing, contributing to superior convective heat dissipation. These findings confirm the effectiveness of 3D topology optimization in improving both the cooling performance and energy conversion efficiency of TEG-based waste heat recovery systems.
本研究提出了一种基于热电发电机(TEG)的废热回收系统被动冷却散热器结构设计的三维拓扑优化策略。优化目标是使TEG冷侧平均温度最小,从而增强自然对流冷却,提高系统的功率输出和转换效率。结果表明,拓扑优化后的散热片通过促进散热片与气流的相互作用增强了自然对流,显著降低了散热片冷侧的平均温度,提高了系统的热电性能。在数量上,3D拓扑优化的散热器优于传统的直鳍设计,输出功率提高27.9%,热电转换效率提高14.5%。此外,使用q准则的流场分析表明,涡流结构和气流混合增强,有助于更好的对流散热。这些发现证实了三维拓扑优化在提高基于teg的余热回收系统的冷却性能和能量转换效率方面的有效性。
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引用次数: 0
Determination of physical and thermal properties of nano silica core - based VIPs using experimental and RSM methods, optimization of unit costs 采用实验和RSM方法测定纳米二氧化硅核基vip的物理和热性能,优化单位成本
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-29 DOI: 10.1016/j.ijthermalsci.2025.110595
Ali Ekrem Akdağ , Murat Koru , Nuri Işıldar , Hilmi Cenk Bayrakçı , Metin Davraz
In building applications, growing energy conservation goals have increased the demand for high-performance thermal insulation materials. The main objective of this study was to develop and optimize high-performance vacuum insulation panels (VIPs) with reduced thermal conductivity through composition and density control. In this study, the thermal behavior of vacuum insulation panels (VIPs) containing fumed silica (FS) was investigated and optimized using experimental design and a Response Surface Methodology (RSM). A total of 32 VIP samples with different core compositions and densities were fabricated and characterized. The core mixtures consisted of FS, glass fiber (GF), and silicon carbide (SiC), combined in various proportions and compacted under controlled compression forces. The cores were vacuum sealed below 1 Pa using a seven-layer metallized ALUPET barrier film to ensure long-term vacuum stability. Subsequently, the VIPs were fabricated by vacuum sealing the cores, and their thermal conductivities were experimentally measured to validate the proposed design approach.
The effects of FS, GF, SiC, and density (D) on thermal resistance (R) were modeled and statistically evaluated using a combined mixture–process design. Statistical analysis confirmed the significance of the model (p < 0.001), showing a strong correlation between the predicted and experimental results (R2 = 0.958, adjusted R2 = 0.944, predicted R2 = 0.890). Increasing density significantly reduced R, while higher FS and SiC contents improved the overall insulation capability. GF primarily contributed to enhancing the structural integrity of the panels.
A cost analysis based on current raw material prices revealed that panels with balanced FS-GF-SiC ratios achieved competitive unit costs of approximately 40–45 $·m−2, indicating that high insulation efficiency can be achieved without substantial cost increase. The VIP produced with 80 % FS, 10 % SiC, and 10 % GF under a compression force of 14 kN showed the lowest thermal conductivity (0.00394 W·m⁻¹·K⁻¹) and the highest R (7.65 m²·K·W⁻¹. This configuration represents an optimal balance between thermal performance and economic feasibility, demonstrating the practical potential of the proposed design.
在建筑应用中,日益增长的节能目标增加了对高性能保温材料的需求。本研究的主要目的是通过成分和密度控制来开发和优化具有低导热性的高性能真空隔热板(vip)。本文采用响应面法(RSM)对气相二氧化硅真空绝热板(VIPs)的热性能进行了研究和优化。制备了32个不同岩心组成和密度的VIP样品,并对其进行了表征。芯材混合物由FS、玻璃纤维(GF)和碳化硅(SiC)组成,按不同比例组合,并在控制的压缩力下压实。核心采用七层金属化ALUPET阻隔膜在1pa以下真空密封,以确保长期真空稳定性。随后,采用真空密封的方法制备了vip,并对其热导率进行了实验测量,以验证所提出的设计方法。使用混合工艺设计对FS、GF、SiC和密度(D)对热阻(R)的影响进行了建模和统计评估。统计分析证实了模型的显著性(p < 0.001),预测结果与实验结果具有较强的相关性(R2 = 0.958,调整R2 = 0.944,预测R2 = 0.890)。增加密度可显著降低R,而增加FS和SiC含量可提高整体绝缘性能。GF主要有助于提高面板的结构完整性。基于当前原材料价格的成本分析显示,具有平衡FS-GF-SiC比例的面板具有竞争力的单位成本约为40-45美元·m−2,这表明可以在不大幅增加成本的情况下实现高隔热效率。80% FS, 10% SiC和10% GF在14 kN的压缩力下生产的VIP,其导热系数最低(0.00394 W·m⁻¹·K⁻¹),R最高(7.65 m²·K·W⁻¹)。这种结构代表了热性能和经济可行性之间的最佳平衡,展示了拟议设计的实际潜力。
{"title":"Determination of physical and thermal properties of nano silica core - based VIPs using experimental and RSM methods, optimization of unit costs","authors":"Ali Ekrem Akdağ ,&nbsp;Murat Koru ,&nbsp;Nuri Işıldar ,&nbsp;Hilmi Cenk Bayrakçı ,&nbsp;Metin Davraz","doi":"10.1016/j.ijthermalsci.2025.110595","DOIUrl":"10.1016/j.ijthermalsci.2025.110595","url":null,"abstract":"<div><div>In building applications, growing energy conservation goals have increased the demand for high-performance thermal insulation materials. The main objective of this study was to develop and optimize high-performance vacuum insulation panels (VIPs) with reduced thermal conductivity through composition and density control. In this study, the thermal behavior of vacuum insulation panels (VIPs) containing fumed silica (FS) was investigated and optimized using experimental design and a Response Surface Methodology (RSM). A total of 32 VIP samples with different core compositions and densities were fabricated and characterized. The core mixtures consisted of FS, glass fiber (GF), and silicon carbide (SiC), combined in various proportions and compacted under controlled compression forces. The cores were vacuum sealed below 1 Pa using a seven-layer metallized ALUPET barrier film to ensure long-term vacuum stability. Subsequently, the VIPs were fabricated by vacuum sealing the cores, and their thermal conductivities were experimentally measured to validate the proposed design approach.</div><div>The effects of FS, GF, SiC, and density (D) on thermal resistance (R) were modeled and statistically evaluated using a combined mixture–process design. Statistical analysis confirmed the significance of the model (p &lt; 0.001), showing a strong correlation between the predicted and experimental results (R<sup>2</sup> = 0.958, adjusted R<sup>2</sup> = 0.944, predicted R<sup>2</sup> = 0.890). Increasing density significantly reduced R, while higher FS and SiC contents improved the overall insulation capability. GF primarily contributed to enhancing the structural integrity of the panels.</div><div>A cost analysis based on current raw material prices revealed that panels with balanced FS-GF-SiC ratios achieved competitive unit costs of approximately 40–45 $·m<sup>−2</sup>, indicating that high insulation efficiency can be achieved without substantial cost increase. The VIP produced with 80 % FS, 10 % SiC, and 10 % GF under a compression force of 14 kN showed the lowest thermal conductivity (0.00394 W·m<sup>⁻¹</sup>·K<sup>⁻¹</sup>) and the highest R (7.65 m<sup>²</sup>·K·W<sup>⁻¹</sup>. This configuration represents an optimal balance between thermal performance and economic feasibility, demonstrating the practical potential of the proposed design.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110595"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881215","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
Low-cost infrared cameras for assessing lumbar sympathetic blocks in complex regional pain syndrome: A preliminary study 用于评估复杂局部疼痛综合征腰交感神经阻滞的低成本红外摄像机:初步研究
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-26 DOI: 10.1016/j.ijthermalsci.2025.110627
Andrea Garcia-Tristan , Lucia Carbonell-Jose , Maite Bovaira , Mar Cañada-Soriano , José Ignacio Priego-Quesada
The aim of this preliminary study was to evaluate the applicability of low-cost infrared thermography cameras for assessing lumbar sympathetic blocks (LSBs) in patients diagnosed with lower limb Complex Regional Pain Syndrome. Skin temperature was monitored in 7 patients (8 LSBs) over 220 s following the injection of a local anesthetic (10 ml of 0.25 % levobupivacaine together with 80 mg of triamcinolone) aimed at inducing vasodilation in the affected foot. Two infrared cameras, FLIR E60 (high-performance) and HIKMICRO Mini-X (low-cost), and a black body calibrator (BX-500 IR) were used. For both feet, mean, maximum, and corrected mean skin temperatures (adjusted using the black body) were recorded. Based on these, variations (relative to baseline) and temperature asymmetries were calculated. In most cases, effect sizes between camera measurements were negligible or small. However, moderate effect sizes were found in some mid-test variation parameters (e.g., ES = 0.7 for mean skin temperature variation). Reliability between cameras was acceptable for most parameters (ICC>0.40), and excellent for corrected mean temperature (ICC = 0.89) and asymmetry metrics (ICC>0.83). In conclusion, low-cost infrared thermography cameras may be suitable for evaluating LSB performance when focusing on skin temperature asymmetry, and the use of a black body reference to correct mean temperature measurements.
本初步研究的目的是评估低成本红外热像仪在诊断为下肢复杂区域疼痛综合征的患者中评估腰交感神经阻滞(LSBs)的适用性。7例患者(8例lbs)在注射局麻药(10ml 0.25%左布比卡因和80mg曲安奈德)后220 s内监测皮肤温度,目的是诱导患足血管舒张。两台红外摄像机,FLIR E60(高性能)和HIKMICRO Mini-X(低成本),以及一个黑体校准器(BX-500 IR)。记录两只脚的平均、最高和校正后的平均皮肤温度(使用黑体进行调整)。在此基础上,计算了变化(相对于基线)和温度不对称。在大多数情况下,相机测量之间的效应大小可以忽略不计或很小。然而,在一些中间测试变量参数中发现了中等效应量(例如,平均皮肤温度变化的ES = 0.7)。对于大多数参数(ICC>0.40),相机之间的可靠性是可以接受的,并且对于校正后的平均温度(ICC = 0.89)和不对称度量(ICC>0.83)具有出色的可靠性。综上所述,低成本红外热像仪可能适合评估LSB的性能,当关注皮肤温度的不对称性,并使用黑体参考来校正平均温度测量。
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引用次数: 0
Stochasticity of single-cavity heterogeneous bubble growth in saturated pool boiling 饱和池沸腾中单腔非均相气泡生长的随机性
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-25 DOI: 10.1016/j.ijthermalsci.2025.110634
Run-Sheng Qi, Ya-Nan Li, Zeng-Yao Li
The heterogeneous bubble growth dynamics is a fundamental aspect of nucleate boiling. Attentions have focused more on the generality in the “typical” bubble cycle in most previous studies, but less on the stochasticity of the bubble growth process. In this study, successive heterogeneous bubble nucleation-growth-departure cycles from a fixed single cavity on a horizontal surface with the static contact angle of 59.5° in saturated nucleate pool boiling of deionized water are experimentally investigated, covering the wall superheat of 6.1–15.5 K and the system pressure of 18–99.2 kPa. Distinct stochasticity for both the growth time and the departure radius of the successive bubbles is manifested under the same system conditions, which is responsible for the discrepancies of the bubble growth coefficient under the classical theoretical framework. It is revealed that the instability of the surrounding fluid-thermal environment has a prominent influence on the stochasticity of the bubble growth coefficient, which is governed by the competition between the natural convection induced by the temperature difference and the rewetting convection induced by the bubble departure. The stochasticity of the bubble growth coefficient increases versus the Richardson Number, Ri, with a mutation occurring at about Ri = 10, while the stochasticity of the bubble departure radius closely depends on that of the bubble growth coefficient with a growing relevance versus the Jacob number. Furthermore, a method to predict the heterogeneous bubble growth is proposed in consideration of the effect of the stochasticity. This new insight captures the general characteristics of bubble growth through a dimensionless correlation, while the stochasticity is controlled in a separate dimensional correlation involving only the departure parameters. Within the Jacob number range of 18.9–141.4, the dimensionless correlation demonstrates good overall performance, with the deviations from experiments remaining low at a MAPE of 1.72–3.88 %.
非均相气泡生长动力学是核沸腾的一个基本方面。以往的研究多关注“典型”气泡周期的普遍性,而较少关注气泡生长过程的随机性。实验研究了饱和核池去离子水沸腾过程中,在静止接触角为59.5°的水平表面上的固定单腔内,在壁面过温为6.1 ~ 15.5 K,系统压力为18 ~ 99.2 kPa的条件下,非均质气泡成核-生长-离开连续循环过程。在相同的系统条件下,连续气泡的生长时间和离开半径都表现出明显的随机性,这是经典理论框架下气泡生长系数存在差异的原因。结果表明,气泡生长系数的随机性主要受周围流热环境的不稳定性影响,而气泡生长系数的随机性主要受温差引起的自然对流与气泡离开引起的再润湿对流的竞争支配。气泡生长系数的随机性随理查德森数Ri而增加,在Ri = 10左右发生突变,而气泡离开半径的随机性与气泡生长系数的随机性密切相关,且与Jacob数的相关性越来越强。在此基础上,提出了一种考虑随机影响的非均质气泡生长预测方法。这种新见解通过无量纲相关性捕获了气泡生长的一般特征,而随机性在仅涉及偏离参数的单独量纲相关性中得到控制。在雅各布数18.9 ~ 141.4的范围内,无量纲相关总体表现良好,与实验的偏差保持在1.72 ~ 3.88%的MAPE范围内。
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引用次数: 0
Study on steady-state temperature field distribution of spur gear considering angular misalignment error 考虑角对中误差的直齿齿轮稳态温度场分布研究
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-29 DOI: 10.1016/j.ijthermalsci.2025.110628
Peng Dong , Desheng Zou , Chang Xiong , Shumiao Zuo , Junbin Lai , Xiangyang Xu , Shuhan Wang , Yanfang Liu
Angular misalignment error, a common defect arising from manufacturing and assembly processes in gear transmission systems, leads to non-uniform load distribution on tooth surfaces and consequently causes uneven steady-state temperature fields. To accurately and efficiently compute the tooth surface temperature distribution under angular misalignment error, this study proposes a novel computational method for determining the steady-state temperature field of gear teeth. The approach employs Loaded Tooth Contact Analysis (LTCA) to evaluate load distribution across tooth surfaces incorporating angular misalignment error. Subsequently, the transient friction coefficient of the tooth surface is calculated based on Thermo-Elastohydrodynamic Lubrication (TEHL) theory. Building upon this foundation, the meshing heat flux of the gear teeth is quantified, and the convective heat transfer coefficient of the tooth surface was determined. Based on thermal equilibrium theory, the steady-state temperature field of gears is subsequently obtained. Utilizing this model, a systematic analysis is carried out to investigate the effect of misalignment direction and magnitude on tooth surface load distribution, lubrication characteristics, and temperature field evolution. The results indicate that angular misalignment error in the y-direction exhibit significant sensitivity in both load distribution and lubrication-induced temperature variations. Finally, the validity of the proposed model was verified through finite element method (FEM) and experiment. This study provides theoretical support for elucidating the temperature field distribution characteristics of gears under angular misalignment error.
角对中误差是齿轮传动系统在制造和装配过程中常见的缺陷,它会导致齿面载荷分布不均匀,从而导致稳态温度场不均匀。为了准确、高效地计算齿面温度分布,提出了一种确定齿轮齿面稳态温度场的计算方法。该方法采用加载齿接触分析(LTCA)来评估包含角不对中误差的齿面负载分布。然后,基于热弹流动力润滑理论计算了齿面瞬态摩擦系数。在此基础上,量化了齿轮齿面啮合热流密度,确定了齿面对流换热系数。基于热平衡理论,得到了齿轮的稳态温度场。利用该模型,系统分析了偏心方向和大小对齿面载荷分布、润滑特性和温度场演化的影响。结果表明,y方向的角不对中误差对载荷分布和润滑引起的温度变化都具有显著的敏感性。最后,通过有限元法和实验验证了所提模型的有效性。该研究为阐明齿轮在角不对中误差下的温度场分布特性提供了理论支持。
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引用次数: 0
Visualization experimental study on two-phase flow boiling characteristics in leaf vein manifold microchannel heat sinks 叶脉流形微通道散热器两相流沸腾特性的可视化实验研究
IF 5 2区 工程技术 Q1 ENGINEERING, MECHANICAL Pub Date : 2026-05-01 Epub Date: 2025-12-19 DOI: 10.1016/j.ijthermalsci.2025.110604
Keyi Huang , Guiping Lin , Yuandong Guo , Kai Tang , Jinyin Huang , Hongxing Zhang , Jianyin Miao
Manifold microchannel (MMC) cooling has emerged as a critical technology for thermal management in high-heat-flux microelectronics. While previous studies focused on thermal-hydraulic performance, mechanistic understanding of two-phase flow regimes remains limited. In this study, visualization experiments were conducted to examine flow boiling characteristics in leaf vein manifold microchannel (LVMMC) heat sinks compared with conventional straight manifold microchannels (SMMC). HFE-7000 was employed under controlled flow rates (20–160 mL/min) and heat fluxes (0–100 W/cm2), with two-phase dynamics being recorded through synchronized thermal measurements and high-speed imaging. Significant temperature reductions exceeding 5 °C were achieved in LVMMC compared to SMMC across all tested flow rates, attributed to the 45° incidence angle that improved flow distribution uniformity and enhanced convective heat transfer. High-speed visualization revealed periodic liquid replenishment in inlet manifolds as CHF conditions were approached. This phenomenon was associated with inlet vapor backflow, which was identified as the primary triggering mechanism of CHF. The symmetric LVMMC-1 reduced the liquid replenishment cycle duration by approximately 30 % compared to SMMC, resulting in a CHF enhancement exceeding 20 %. While the asymmetric LVMMC-2 demonstrated the highest heat transfer coefficient of 13,888 W/(m2·K) due to enhanced nucleation at inlet corners, the LVMMC-1 exhibited superior coefficient of performance reaching 16,320 and better stability under high heat fluxes. This work elucidates the flow regime transitions in MMCs and demonstrates the efficacy of bioinspired LVMMC designs in addressing high-heat-flux cooling challenges.
流形微通道(MMC)冷却已成为高热流密度微电子热管理的关键技术。虽然以前的研究主要集中在热工性能上,但对两相流的机理理解仍然有限。在本研究中,通过可视化实验研究了叶脉流形微通道(LVMMC)散热器与传统直流形微通道(SMMC)的流动沸腾特性。HFE-7000在控制流量(20-160 mL/min)和热通量(0-100 W/cm2)下使用,通过同步热测量和高速成像记录两相动力学。在所有测试流速下,与SMMC相比,LVMMC的温度显著降低了5°C以上,这要归功于45°入射角改善了流动分布均匀性,增强了对流换热。高速可视化显示,当CHF工况接近时,进气歧管有周期性的液体补给。这种现象与进口蒸汽回流有关,这被认为是CHF的主要触发机制。与SMMC相比,对称的LVMMC-1减少了大约30%的液体补充周期,导致CHF增强超过20%。非对称型LVMMC-2的传热系数最高,为13888 W/(m2·K),而非对称型LVMMC-1的传热系数更高,达到16320 W/(m2·K),在高热流密度下稳定性更好。这项工作阐明了mmc中的流动状态转变,并证明了生物启发的LVMMC设计在解决高热流密度冷却挑战方面的有效性。
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International Journal of Thermal Sciences
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