International Journal of Heat and Fluid Flow最新文献_第7页

Study on the flow boiling characteristics of two-phase cooling loop with mechanically pumped circulation 机械泵送循环两相冷却回路流动沸腾特性研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-18 DOI: 10.1016/j.ijheatfluidflow.2025.110191

Maojin Zeng , Qian Lyu , Dan Zhu , Jiapeng Chang , Haolei Han , Yan Dou , Jinjie Feng , Botao Xia , Xiaoling Yu

With the rapid development of the new energy industry, the increasing power demands higher requirements for thermal management. The phase change system of the mechanically pumped cooling loop (MPCL) has gained widespread attention for its ability to achieve effective flow boiling by precisely regulating the dryness in response to power variations. In this paper, using the R134a as the refrigerant, the flow boiling characteristics of cold plate are experimentally investigated under the MPCL. The flow rate and power intervals are 0.5–1.5 L/min and 180–1690 W, respectively. Meanwhile, the optimal dryness is calculated by visualizing the flow, temperature, and phase fields using the Ansys Fluent. The results show that the higher flow rate weakens latent heat transfer. The heat transfer coefficient (HTC) is increased and then decreased with flow rate. The optimal flow boiling regime is achieved at the inflection point, which is shifted to higher flow rate as power is increased. When the power is too high, the bubble generation rate exceeds the detachment rate, causing massive bubbles to cover the wall and degrade thermal performance. As the flow rate is increased, the critical heat flux (CHF) is also increased, but the maximum value of HTC is decreased. To ensure safe operation of MPCL, the dryness should be controlled within 0.6. The dryness for optimum boiling heat transfer is in the range of 0.2 to 0.3.The pressure drop is increased with both flow rate and power. This study can provide valuable guidance for the design of MPCL systems for high-power chips.

随着新能源产业的快速发展，日益增长的电力对热管理提出了更高的要求。机械泵浦冷却回路相变系统由于能够根据功率变化精确调节干燥度，从而实现有效的流动沸腾而受到广泛关注。本文以R134a为制冷剂，在MPCL条件下对冷板的流动沸腾特性进行了实验研究。流量为0.5 ~ 1.5 L/min，功率间隔为180 ~ 1690 W。同时，通过使用Ansys Fluent可视化流动、温度和相场来计算最佳干燥度。结果表明，较高的流量会减弱潜热传递。传热系数（HTC）随流量先增大后减小。在拐点处达到最佳流动沸腾状态，随着功率的增加，该拐点向更高的流量转移。当功率过高时，气泡产生速率超过分离速率，导致大量气泡覆盖壁面，降低热性能。随着流量的增加，临界热通量（CHF）也增加，但HTC的最大值减小。为保证MPCL的安全操作，干燥度应控制在0.6以内。最佳沸腾传热的干燥度在0.2到0.3之间。压降随流量和功率的增大而增大。本研究可为大功率芯片的MPCL系统设计提供有价值的指导。

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引用次数: 0

Effect of surface gradient wettability distribution in microchannel on flow boiling heat transfer by numerical simulation 微通道表面梯度润湿性分布对流动沸腾换热的影响

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-18 DOI: 10.1016/j.ijheatfluidflow.2025.110200

Wenguang Li, Zhanxiu Chen, Shiyi Qin, Ao Ma, Mingchao Chen

The effect of bottom wall wettability on the flow boiling heat transfer is investigated in horizontal microchannel using numerical simulation method. The bottom wall wettability is distributed by a single wettable surface and a composite wettable surface, the single wettable surface being adopt by superhydrophilic, neutral, and superhydrophobic surface, and the composite wettable surface being adopt by transverse gradient wettability distribution (TWGD) and a longitudinal gradient wettability distribution (LWGD), respectively. Variation of heat flux at the bottom wall in the range of 60–120 W/cm². It was found that vortex structures are easier to be triggered on superhydrophilic wall or wall including partly superhydrophilic surface. Bubbles generated on superhydrophilic surface is smaller and detach from wall easily than that on neutral or superhydrophobic surface, bubbles generated on superhydrophobic surface tend to attach on wall and grow up. Both of Vortex structures and bubble flow strength heat transfer between bott0om wall and fluid, improving the bottom surface temperature uniformity, at a heat flow density of 120 W/cm², temperature uniformity of bottom surface with LWGD increased by 7.72 %, while that of bottom surface with TWGD increased by 1.5 % compared with neutral surface, and pressure drop on microchannel with LWGD surface decrease by 4.6 %, pressure drop on microchannel with TWGD surface increased by 5.59 %. Heat transfer coefficient with TWGD surface is the biggest than others surfaces, but pressure drop increase much, comprehensive heat transfer factor ε decrease with heat flux density increase, ε is increased only by 0.61 %, comprehensive heat transfer factor ε in microchannel with LWGD bottom increase with heat flux density increase, ε is increased by 2.39 % compared with that in microchannel with neutral bottom.

采用数值模拟方法研究了水平微通道内底壁润湿性对流动沸腾换热的影响。底壁润湿性分为单一可湿性面和复合可湿性面，其中单一可湿性面采用超亲水性、中性和超疏水性面，复合可湿性面分别采用横向梯度润湿性分布（TWGD）和纵向梯度润湿性分布（LWGD）。底壁热流密度在60 ~ 120w /cm2范围内的变化。研究发现，在超亲水壁面或包含部分超亲水表面的壁面上更容易触发涡结构。在超亲水表面上产生的气泡比在中性或超疏水表面上产生的气泡更小，更容易与壁面分离，在超疏水表面上产生的气泡更容易附着在壁面上并长大。在热流密度为120 W/cm2的情况下，无水脱硫的底表面温度均匀性比中性表面提高了7.72%，无水脱硫的底表面温度均匀性比中性表面提高了1.5%，无水脱硫表面微通道压降降低了4.6%，无水脱硫表面微通道压降提高了5.59%。TWGD表面的换热系数最大，但压降增加较多，综合换热系数ε随热流密度的增加而减小，仅增加0.61%，LWGD底微通道的综合换热系数ε随热流密度的增加而增加，与中性底微通道相比，ε增加了2.39%。

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引用次数: 0

Investigations on heat transfer in turbulated cutback surface with Chevron-shaped rib configurations for trailing-edge 后缘涡形肋形湍流切面传热研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-17 DOI: 10.1016/j.ijheatfluidflow.2025.110201

Mengjiao Han , Lin Ye , Cunliang Liu , Xuyang Ji , Zhuan Liu , Xiyuan Liang

The current research proposes a unique turbulated cutback structure for trailing-edge cooling, which places chevron-shaped ribs on the cutback surface to improve heat transfer. An experimental system is established, and the reliability of the numerical method is verified via pressure-sensitive paint (PSP) and transient thermochromic liquid–crystal (TLC) experiments. The adiabatic film effectiveness (η), heat transfer coefficient, and flow physics of the cutback surface with various angles of chevron-shaped ribs are obtained via numerical simulations and compared with those of the traditional smooth case to further analyse and understand the film cooling characteristics of the turbulated cutback structure. Three chevron-shaped rib angles of 30°, 45°, and 60° for three blowing ratios (M) are investigated. The effect of chevron-shaped ribs on η is not notable because the rib height is relatively small. The low η with the “M-shape” is manifested downstream of the cutback surface. In the downstream region of the cutback surface, η becomes weaker with increasing angle, but the values are still above 0.9. The chevron-shaped ribs significantly enhance the heat transfer on the cutback surface, and the area-averaged heat transfer coefficient is 26.3–41.2 % greater than that in the smooth case. The 45-deg case produces a higher heat transfer intensity than the other two chevron-shaped rib cases at the studied M. In the region far downstream, the heat transfer intensity of the 30-deg case is higher than that of the other two cases, whereas it is lower downstream of the slot exit, in which the difference decreases as M increases. At M = 1.0, the area-averaged heat transfer intensity of the cases with large angles of 45 deg and 60 deg reaches its peak. The net heat-flux reduction (NHFR) values of the ribbed structure are consistently greater than those of the smooth case, with an improvement of 4.1–8.8 % at low M and a sharp increase to 26.5 % when M reaches 2.0, confirming enhanced comprehensive cooling performance. Additionally, aerodynamic analysis revealed that, compared with smooth ribs, chevron-shaped ribs increase the total pressure loss coefficient by only approximately 2.2 % and the thermal loss coefficient by approximately 6.3 %, indicating minimal adverse effects on aerodynamic performance.

本研究提出了一种独特的后缘冷却湍流切口结构，在切口表面放置楔形肋以改善传热。建立了实验系统，并通过压敏涂料（PSP）和瞬态热致变色液晶（TLC）实验验证了数值方法的可靠性。通过数值模拟，得到了不同棱形角切槽表面的绝热膜效率（η）、换热系数和流动物理特性，并与传统光滑情况进行了比较，进一步分析和了解了湍流切槽结构的膜冷却特性。研究了三种吹风比(M)下30°、45°和60°的三种形肋角。字形肋对η的影响不显著，因为肋高度相对较小。切削面下游的η值较低，呈“m”形。在切割面下游区域，η值随着角度的增大而变弱，但仍大于0.9。楔形肋块显著增强了切刀表面的换热，面积平均换热系数比光滑情况提高了26.3 ~ 41.2%。在M处，45度工况的换热强度高于其他两种工况。在较下游区域，30度工况的换热强度高于其他两种工况，而在槽出口下游区域，其差值随着M的增大而减小。在M = 1.0时，45°和60°大角情况下的面积平均换热强度达到峰值。肋结构的净热流密度降低值（NHFR）始终大于光滑结构，在低M时提高了4.1 - 8.8%，当M达到2.0时急剧增加到26.5%，证实了综合冷却性能的提高。此外，气动分析显示，与光滑肋板相比，字形肋板的总压损失系数仅增加了约2.2%，热损失系数增加了约6.3%，表明对气动性能的不利影响最小。

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引用次数: 0

Effects of various cylindrical hole layouts on film cooling effectiveness of a cavity blade tip 不同圆柱孔布置对空腔叶尖气膜冷却效果的影响

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-17 DOI: 10.1016/j.ijheatfluidflow.2025.110211

Kun Du , Fangshun Zhang , Ding Luo , Wenbin Chen , Cunliang Liu , Bengt Sunden

Turbine blade tip clearance exacerbates aerodynamic losses and raises thermal load on the blade tip, detrimentally affecting blade lifespan and reliability. Arranging the film hole is a prevalent approach for blade tip cooling. A rational hole layout is crucial for improving the film cooling effectiveness and minimizing losses. Based on the conventional nine-hole tip layout along the camber line, this study presents a design concept involving moving one, two, or three film holes from the trailing edge region to the leading edge and adjusting the mid-chord holes downward. Five novel film hole layouts are given rise to by this concept. Numerical simulations are carried out to analyze the film cooling effectiveness and the streamline distribution on different film hole layouts. The results show that moving the trailing edge holes forward can enhance coolant flow on the leading edge and on the suction side. As more trailing edge holes are relocated forward, overall film cooling effectiveness is improved. Specifically, the layout with three trailing edge holes relocated to the leading edge has an 11.47% higher area-average film cooling effectiveness than the nine-hole tip layout along the camber line. The layout with three mid-chord holes shifted downward, with a 2.83% increase, enhances the cooling of the suction side on the mid-chord region and overall cooling uniformity. The structure that integrates both methods described above shows a 14.49% increase over the nine-hole tip layout along the camber line. In addition, changes in the positions of the film holes on the blade tip surface will also affect the aerodynamic losses. These findings provide valuable guidance for designing high-efficiency cooling tip structure.

涡轮叶片叶尖间隙加剧了气动损失，增加了叶尖上的热负荷，对叶片的寿命和可靠性产生不利影响。布置膜孔是一种常用的叶尖冷却方法。合理的孔布局是提高气膜冷却效果和减少损失的关键。在传统的九孔叶顶沿弧度线布置的基础上，本研究提出了一种设计理念，将一个、两个或三个膜孔从后缘区域移动到前缘，并将中弦孔向下调整。这一概念产生了五种新颖的膜孔布局。通过数值模拟分析了不同膜孔布置下的膜冷却效果和流线分布。结果表明，将尾缘孔向前移动可以增强前缘和吸力侧冷却剂的流动。随着更多尾缘孔向前移动，整体气膜冷却效果得到提高。具体而言，将3个尾缘孔重新布置到前缘的布置比沿弧度线布置的9个孔布置的面积平均气膜冷却效率高11.47%。三个中弦孔下移的布置增强了中弦区吸力侧的冷却效果，整体冷却均匀性提高了2.83%。结合上述两种方法的结构比沿弧度线的九孔尖端布局增加了14.49%。此外，叶尖表面膜孔位置的变化也会影响气动损失。这些研究结果为设计高效的冷却尖端结构提供了有价值的指导。

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引用次数: 0

Parametric investigation of a solid-porous fin design for microchannel thermal performance improvement 改善微通道热性能的固体多孔翅片设计参数化研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-17 DOI: 10.1016/j.ijheatfluidflow.2025.110210

Hanieh Asgharpouri Moghadam , Farid Dolati , Fatemeh Bagherighajari , Morteza Momeni Taromsari

Cooling and thermal management in micro-scale systems are critically important in various applications, as they minimize equipment size and extend its lifespan. Although conventional solid-fin heat sinks have boosted the efficiency of cooling systems, they face a fundamental trade-off between heat dissipation efficiency, energy consumption, and the mechanical power required for pumping. To overcome this, porous fins are applicable; however, their performance is often limited by low effective thermal conductivity and a lack of geometric design refinement. Therefore, this study introduces a novel hybrid porous-solid fin design that strategically combines the high conductivity of solid fins with the superior surface area and flow mixing of porous materials. This numerical investigation analyzes the thermal–hydraulic performance of the hybrid microchannel, focusing on the effects of porous layer thickness (t_p), height (h_p), Reynolds number (Re), and porosity (ε). Simulations identify that a porous thickness of t_p = 0.3 mm yields the best performance, which reduces pressure drop by 21.96 % while simultaneously enhancing heat transfer by 31.21 %, culminating in a 42.51 % improvement in the Performance Evaluation Factor (PEF) compared to conventional solid fins. The analysis further reveals that increasing Re decreases thermal resistance at the expense of a higher pressure drop, while lower porosity enhances heat transfer at the cost of increased flow resistance. Crucially, the favorable porous height for PEF decreases with higher Re, emphasizing the necessity for a flow-condition-specific design to maximize the benefits of this hybrid approach.

微尺度系统的冷却和热管理在各种应用中至关重要，因为它们可以最小化设备尺寸并延长其使用寿命。尽管传统的固体翅片散热器提高了冷却系统的效率，但它们面临着散热效率、能量消耗和泵送所需的机械功率之间的基本权衡。为了克服这个问题，多孔翅片是适用的；然而，它们的性能往往受到低有效导热率和缺乏几何设计精细的限制。因此，本研究引入了一种新型的多孔-固体混合翅片设计，将固体翅片的高导电性与多孔材料的优越表面积和流动混合巧妙地结合在一起。该数值研究分析了混合微通道的热工性能，重点研究了多孔层厚度（tp）、高度（hp）、雷诺数（Re）和孔隙度（ε）对混合微通道热工性能的影响。仿真结果表明，多孔厚度tp = 0.3 mm可获得最佳性能，与传统的固体翅片相比，可将压降降低21.96%，同时传热能力提高31.21%，最终性能评估因子（PEF）提高42.51%。进一步分析表明，增加Re会以增加压降为代价降低热阻，而降低孔隙率会以增加流动阻力为代价增强传热。至关重要的是，PEF的有利孔隙高度随着Re的升高而降低，这强调了针对流动条件进行特定设计的必要性，以最大限度地提高这种混合方法的效益。

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引用次数: 0

Synergistic enhancement of heat transfer in tubular heat exchangers using twisted tape inserts and nanofluids: An integrated numerical and experimental review 使用扭曲带插入和纳米流体的管式换热器中传热的协同增强：综合数值和实验回顾

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-17 DOI: 10.1016/j.ijheatfluidflow.2025.110180

Deepak Kumar Rathaur, R.M. Sarviya, S.P.S. Rajput

The rising global demand for compact, energy-efficient heat exchangers has driven interest in passive heat transfer enhancement techniques. Among these, the combination of twisted tape inserts with nanofluids is particularly promising, as twisted tapes generate swirl flows that enhance heat transfer, while nanofluids improve thermal conductivity without requiring extra energy. This review systematically synthesizes experimental and numerical studies on single, hybrid, and tri-hybrid nanofluids combined with classical and modified twisted tape inserts, including perforated, wavy, jagged, wing-cut, V-cut, W-cut, and compound designs. Performance is evaluated in terms of Nusselt number, friction factor, and thermal performance factor. Classical twisted tape inserts with single nanofluid enhance heat transfer by 15–40 %, whereas advanced geometries with hybrid nanofluids achieve 50–95 % gains. The maximum reported Nusselt number enhancement is approximately 72% for hybrid nanofluids with modified twisted tape inserts at higher Reynolds numbers, accompanied by a 20–60 % increase in friction factor. Thermal performance factors generally exceed unity, peaking at around 2.5 for a helical coil–twisted tape insert configuration with graphene/water nanofluid. Comparisons indicate that plain twisted tape inserts with Al₂O₃/water nanofluid improve heat transfer by about 40%, while perforated twisted tape inserts with Al₂O₃-Cu/water hybrid nanofluids achieve approximately 85%. Overall, geometry modification combined with advanced nanofluids can nearly double heat exchanger performance, although challenges related to pumping power, nanofluid stability, and techno-economic feasibility remain key areas for future research.

全球对紧凑型、高能效热交换器的需求不断增长，推动了人们对被动传热增强技术的兴趣。其中，扭曲带与纳米流体的结合尤其有前景，因为扭曲带产生漩涡流动，加强传热，而纳米流体在不需要额外能量的情况下提高导热性。本文系统地综合了单一、混合和三混合纳米流体与经典和改进的扭曲带插入物结合的实验和数值研究，包括穿孔、波浪、锯齿、翼形切割、v形切割、w形切割和复合设计。性能是根据努塞尔数、摩擦系数和热性能系数来评估的。传统的扭曲带插入与单一纳米流体提高传热15 - 40%，而先进的几何形状与混合纳米流体实现50 - 95%的增益。据报道，在较高雷诺数下，混合纳米流体的最大努塞尔数增强约为72%，同时摩擦系数增加20 - 60%。热性能系数通常超过1，对于带有石墨烯/水纳米流体的螺旋线圈扭曲带插入配置，热性能系数在2.5左右达到峰值。对比表明，普通的扭曲带插入Al2O3/水纳米流体可以提高约40%的换热率，而穿孔扭曲带插入Al2O3- cu /水混合纳米流体可以提高约85%的换热率。总体而言，尽管泵送功率、纳米流体稳定性和技术经济可行性仍是未来研究的关键领域，但与先进纳米流体相结合的几何形状改变可以使热交换器的性能几乎翻倍。

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引用次数: 0

Taguchi analysis on convective heat transfer of a Prandtl-Eyring hybrid nanofluid over a Riga plate: Entropy optimization Prandtl-Eyring混合纳米流体在Riga板上对流换热的田口分析：熵优化

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-15 DOI: 10.1016/j.ijheatfluidflow.2025.110203

Mohanaphriya US, Tanmoy Chakraborty

<div><div>This objective of this study is to investigate the influence of nanoparticles (NPs) shapes — spherical, cylindrical, brick-like, and platelet — on stagnation-point flow and heat transfer in a Prandtl–Eyring hybrid nanofluid over a vertical Riga plate. Prandtl–Eyring fluid is considered as engine oil, with the suspension of <span><math><mrow><mi>C</mi><mi>u</mi></mrow></math></span> and <span><math><mrow><mi>Z</mi><mi>r</mi><msub><mrow><mi>O</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span> nanoparticles. The analysis includes generalized Fourier heat conduction using the Cattaneo–Christov model along with solar radiation, and convective boundary conditions. Numerical solutions are obtained using the MATLAB’s stiff ordinary differential equation solver ode15s and optimized using the Matlab trust-region reflective algorithm. Results reveal that the Prandtl–Eyring parameters reduce the velocity but enhance temperature, while platelet-shaped nanoparticles yield the highest skin friction and heat transfer performance. A marginal 0.027% rise in the skin friction and up to 20.84% reduction in the rate of heat transportation are perceived across all the shapes within the relaxation time parameter (<span><math><mi>ξ</mi></math></span>) ranging between <span><math><mrow><mn>0</mn><mo>.</mo><mn>0</mn><mo>≤</mo><mi>ξ</mi><mo>≤</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>. Furthermore, Entropy generation could be minimized by lowering the unsteadiness parameter and modified Hartmann number. Statistical analysis shows that the solar radiation parameter (<span><math><mi>R</mi></math></span>) has the most significant impact (70.35%) on the heat transfer, while the Prandtl–Eyring parameter 1 (<span><math><msup><mrow><mi>α</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span>) has the least (0.002%) impact. Based on the Taguchi optimization, the optimal parameter levels for maximizing heat transfer for the spherically shaped nanoparticles are: <span><math><msup><mrow><mi>α</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> (Prandtl–Eyring parameter 1) <span><math><mrow><mo>=</mo><mn>1</mn><mo>.</mo><mn>2</mn></mrow></math></span>, <span><math><msup><mrow><mi>β</mi></mrow><mrow><mo>∗</mo></mrow></msup></math></span> (Prandtl–Eyring parameter 2) <span><math><mrow><mo>=</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>, <span><math><mi>Z</mi></math></span> (modified Hartmann number) <span><math><mrow><mo>=</mo><mn>1</mn><mo>.</mo><mn>5</mn></mrow></math></span>, <span><math><mi>ξ</mi></math></span> (relaxation time parameter) <span><math><mrow><mo>=</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span>, <span><math><mi>R</mi></math></span> (Solar Radiation parameter) <span><math><mrow><mo>=</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></math></span>, <span><math><mi>γ</mi></math></span> (surface convection parameter) <span><math><mrow><mo>=</mo><mn>15</mn></mrow></math></span>. Under these conditions, the maximum heat tran

本研究的目的是研究纳米颗粒（NPs）形状（球形、圆柱形、砖状和血小板状）对垂直Riga板上Prandtl-Eyring混合纳米流体中停滞点流动和传热的影响。将Prandtl-Eyring流体视为发动机润滑油，其中悬浮着Cu和ZrO2纳米颗粒。分析包括使用Cattaneo-Christov模型的广义傅里叶热传导以及太阳辐射和对流边界条件。利用MATLAB的刚性常微分方程求解器ode15s获得了数值解，并利用MATLAB的信任域反射算法进行了优化。结果表明，Prandtl-Eyring参数降低了速度，但提高了温度，而血小板形状的纳米颗粒具有最高的皮肤摩擦和传热性能。在松弛时间参数（ξ）范围在0.0≤ξ≤0.2之间的所有形状中，表面摩擦边际增加0.027%，热传递率减少20.84%。此外，通过降低非定常参数和修正哈特曼数，可以最大限度地减少熵的产生。统计分析表明，太阳辐射参数(R)对换热的影响最大（70.35%），Prandtl-Eyring参数1 （α∗）的影响最小（0.002%）。基于田口优化，使球形纳米颗粒传热最大化的最佳参数水平为：α∗(Prandtl-Eyring参数1)=1.2,β∗(Prandtl-Eyring参数2)=0.2，Z（修正哈特曼数）=1.5,ξ（松弛时间参数）=0.2，R（太阳辐射参数）=1.0,γ（表面对流参数）=15。在此条件下，得到的最大换热率为0.910954 W。

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引用次数: 0

A posteriori analysis of flame surface density modelling for combustion noise prediction in premixed flames 预混合火焰燃烧噪声预测火焰表面密度模型的后验分析

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-15 DOI: 10.1016/j.ijheatfluidflow.2025.110204

Pavel Panek , Davy Brouzet , Mohsen Talei

The ability of large-eddy simulation (LES) to capture premixed flame acoustics is studied for a turbulent, premixed, round jet flame. Central finite differencing schemes are used with artificial damping. The flame surface density (FSD) approach is used as the combustion model for the reaction progress variable. The effects of combustion modelling and the spatial discretisation scheme order on the flame shape and the sound pressure level (SPL) spectra are examined. It is shown that the FSD approach does not correctly capture flame annihilation. This is where the progress variable gradient decreases as two flame surfaces approach each other. A significant impact of FSD modelling on the SPL is also observed. Comparing the SPL spectra obtained with FSD modelling with those obtained with single-step, Arrhenius-rate chemistry on a fine grid shows that the SPL is underestimated below

S t \approx 4

and overestimated above

S t \approx 4

, where

S t

is a non-dimensional frequency based on the jet diameter and mean centreline jet velocity known as the Strouhal number. Coarse grid simulations approximately match the fine grid results at frequencies up to

S t \approx 3

but overestimate the SPL even more strongly above this level. It is concluded that FSD modelling needs further adjustments to accurately capture combustion noise.

研究了大涡模拟（LES）对紊流、预混、圆形射流火焰的捕捉能力。中心有限差分格式采用人工阻尼。采用火焰表面密度法作为反应过程变量的燃烧模型。研究了燃烧模型和空间离散方案顺序对火焰形状和声压级（SPL）谱的影响。结果表明，FSD方法不能正确地捕捉火焰的湮灭。这是当两个火焰表面相互接近时，进度变量梯度减小的地方。FSD模型对SPL的显著影响也被观察到。将FSD模拟得到的SPL谱与单步arhenius -rate化学在精细网格上得到的SPL谱进行比较，发现SPL在St≈4以下被低估，而在St≈4以上被高估，其中St是基于射流直径和平均中线射流速度（称为Strouhal数）的无量纲频率。粗网格模拟在St≈3以下的频率与细网格模拟结果大致匹配，但在此水平以上，对声压级的高估更为强烈。结论是消防处模型需要进一步调整以准确捕捉燃烧噪声。

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引用次数: 0

CFD investigation of thermal management and flow behavior in an optimized air-cooled tail rotor propulsion system 优化风冷尾桨推进系统的热管理与流动特性CFD研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-14 DOI: 10.1016/j.ijheatfluidflow.2025.110202

Hyowon Bang , Huichan Lee , Giyoung Park , Sungjae Kim , Seangwock Lee

As aerospace propulsion steadily transitions toward electrification, effectively dissipating heat in compact electric tail rotor motors has become a pressing design challenge. In this study, a high-fidelity computational fluid dynamics (CFD) framework is employed to investigate an air-cooled propulsion system specifically configured for helicopter tail rotor applications. Three passive geometric modifications are examined in detail: widening of lateral duct openings, introducing a 15° inclination to the duct sidewalls, and incorporating rotating blades along the central shaft. The optimized configuration demonstrated substantial thermal gains, reducing peak temperatures by 10.38% in the winding, 8.23% in the magnet, and 19.0% in the shaft. This enhancement was primarily attributed to enhanced airflow penetration, boundary-layer thinning, and the development of favorable secondary recirculation zones. Convective heat transfer performance was also elevated, with Nusselt numbers increasing by up to 11.6% across key components. Importantly, these thermal benefits were achieved while maintaining aerodynamic integrity, as the simulated thrust deviated by only 1.34% from experimental rig measurements. The results highlight how targeted, flow-physics-based passive design strategies can simultaneously improve cooling performance and preserve propulsion efficiency. This approach offers a scalable and integration-friendly pathway for next-generation electric rotorcraft requiring lightweight, thermally resilient tail rotor systems.

随着航空航天推进向电气化的稳步过渡，在紧凑型电动尾桨电机中有效散热已成为一个紧迫的设计挑战。在本研究中，采用高保真计算流体动力学（CFD）框架对直升机尾桨专用的气冷推进系统进行了研究。详细检查了三种被动几何修改：拓宽侧管道开口，向管道侧壁引入15°倾角，并沿中央轴合并旋转叶片。优化后的结构显示出显著的热增益，绕组的峰值温度降低了10.38%，磁体的峰值温度降低了8.23%，轴的峰值温度降低了19.0%。这种增强主要是由于气流穿透增强、边界层变薄以及有利的二次再循环区发展。对流换热性能也得到了提升，关键部件的努塞尔数增加了11.6%。重要的是，在保持气动完整性的同时，获得了这些热效益，因为模拟推力与实验装置测量值的偏差仅为1.34%。研究结果强调了有针对性的、基于流动物理的被动设计策略如何在提高冷却性能的同时保持推进效率。这种方法为需要轻型、热弹性尾桨系统的下一代电动旋翼飞机提供了一种可扩展且易于集成的途径。

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引用次数: 0

Effects of the upwind spanwise heterogeneous terrain on the wind resource distribution 逆风向非均质地形对风资源分布的影响

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2025-12-14 DOI: 10.1016/j.ijheatfluidflow.2025.110182

Haosen H.A. Xu , Tianxiang Yu , Raúl Bayoán Cal , Xiaowei Zhu

Wind energy has become increasingly crucial among renewable energy resources, and as the prerequisite for effective wind energy utilization, accurate wind resource assessments are hence prominent. Topography significantly affects near-surface wind fields and is thus an essential factor to be considered for wind resource assessment. However, few studies have addressed the wind resource distribution downwind of spanwise-heterogeneous terrains, which are frequently encountered in both natural and urban environments. To fill this gap, large eddy simulations were performed to investigate wind distributions over a uniform terrain downwind of terrains featuring spanwise-alternating strips of low and high surface roughness, and the high roughness surface coverage ratio

λ

is varied from 12.5% to 100%. The analysis focuses on the wind speed within the turbine blades region, and two dominant mechanisms are identified: the rough-to-smooth transition (RST) and spanwise heterogeneity of momentum (SHM). The dominance of the two mechanisms depends strongly on

λ

, with RST dominating over SHM as

λ

increases. Moreover, RST initially increases the wind speed due to the growth of the internal boundary layer but leads to a decrease of wind speed further downwind as the internal boundary layer rearranges. SHM results from secondary flows induced by the heterogeneous terrain upwind, which decay downwind. As

λ

increases, secondary flow structures transition from asymmetric to symmetric patterns, and lower

λ

leads to asymmetric flows, sustaining momentum heterogeneity farther downwind. Hence, upwind spanwise heterogeneous terrains can significantly impact the wind speed distribution, and suggestions are made for wind farm planning based on the results.

风能在可再生能源中的地位越来越重要，准确的风能资源评价是有效利用风能的前提。地形对近地面风场影响显著，是风资源评价的重要因素。然而，对于在自然和城市环境中经常遇到的跨向异质地形顺风风资源分布，研究较少。为了填补这一空白，进行了大涡模拟，研究了均匀地形下的风分布，地形具有低表面粗糙度和高表面粗糙度沿展向交替带，高粗糙度表面覆盖率λ从12.5%变化到100%。分析了涡轮叶片区域内的风速，确定了两种主要机制：粗糙-平滑过渡（RST）和动量沿展向非均质性（SHM）。这两种机制的优势很大程度上取决于λ，随着λ的增加，RST的优势大于SHM。此外，由于内边界层的增长，RST最初会增加风速，但随着内边界层的重新排列，会导致进一步下风的风速降低。SHM是由上风向非均匀地形引起的二次流引起的，下风减弱。随着λ的增加，二次流结构从非对称模式转变为对称模式，较低的λ导致不对称流动，维持了下风更远的动量非均质性。因此，逆风向非均质地形对风速分布有显著影响，并根据研究结果对风电场规划提出建议。

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引用次数: 0