International Journal of Heat and Fluid Flow最新文献

A MOPSO-based design optimization on molten salt steam generator forced circulation system under off-design conditions 非设计条件下基于 MOPSO 的熔盐蒸汽发生器强制循环系统优化设计

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-17 DOI: 10.1016/j.ijheatfluidflow.2024.109659

Jiaming Tian, Biao Li, Bo Ren, Yueshe Wang

The concentrating solar power (CSP) technologies have been demonstrated their effectiveness in providing ancillary services for peak regulation in power systems with high penetration of renewable energy. Investigating control mechanisms of a forced circulation mode applied in the steam generator, which a shell-and-tube heat exchanger, in the CSP plant is imperative for swift adaptation to its off-design operating conditions. This study aims to develop a predictive model for the hydrodynamics of a molten salt steam generator in a forced circulation mode, integrating heat transfer and phase change through the lumped parameter method. Additionally, a solution approach is proposed based on multi-objective particle swarm optimization (MOPSO) to achieve thermal-economic optimization designs of the steam generator under varying off-design conditions. Optimization analyses are conducted separately for the constant load and the off-design conditions, considering variables such as molten salt flow rate, steam-water circulation flow rate, number of baffles, and tube diameter of the heat exchanger. The results reveal that during the prolonged operation at low evaporation rates, employing an evaporator with more baffles and a larger tube diameter of 20 mm leads to favorable outcomes. Conversely, meticulous design considerations are imperative when planning for sustained high evaporation rates due to the significant impact of the number of baffles on both efficiency and economic costs. At a load of 215 t/h, the adding of two baffles results in an approximate increase of $20 million in operational costs by nearly and an improvement in efficiency by 0.01. Additionally, a fitting formula is provided to offer recommendations on optimal mass flow rates that maximize effectiveness and minimize economic costs for varying evaporation demands under off-design conditions, thereby assisting engineers in optimizing peak regulation operations.

聚光太阳能发电（CSP）技术在为可再生能源渗透率较高的电力系统提供调峰辅助服务方面的有效性已得到证实。为了迅速适应非设计运行条件，研究 CSP 电站蒸汽发生器（管壳式热交换器）强制循环模式的控制机制势在必行。本研究旨在为强制循环模式下的熔盐蒸汽发生器建立流体力学预测模型，通过集合参数法整合传热和相变。此外，还提出了一种基于多目标粒子群优化（MOPSO）的求解方法，以实现蒸汽发生器在不同非设计条件下的热经济优化设计。考虑到熔盐流速、蒸汽-水循环流速、挡板数量和换热器管径等变量，分别对恒定负荷和非设计工况进行了优化分析。结果表明，在低蒸发率的长时间运行中，采用具有更多挡板和更大管径（20 毫米）的蒸发器会带来有利的结果。相反，由于挡板数量对效率和经济成本都有显著影响，因此在规划持续高蒸发率时，必须进行细致的设计考虑。在负荷为 215 吨/小时的情况下，增加两块挡板可使运营成本增加近 2000 万美元，效率提高 0.01。此外，还提供了一个拟合公式，针对非设计条件下的不同蒸发需求，提出了最佳质量流量的建议，以实现效率最大化和经济成本最小化，从而帮助工程师优化调峰操作。

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引用次数: 0

Detached eddy simulation of large scale wind turbine wake in offshore environment 离岸环境中大型风力涡轮机尾流的分离涡模拟

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109637

Filippo De Girolamo , Alessio Castorrini , Valerio F. Barnabei , Vincenzo Morici , Lorenzo Tieghi , Aldo Bonfiglioli , Alessandro Corsini

The rapid growth of the global offshore wind market underscores the need for accurate numerical simulations to support the development and design of offshore wind farms, especially in regions like the Mediterranean where measured data on marine-weather conditions for use in offshore wind farm design are rare. This paper addresses the challenge of proposing a reliable simulation framework to assess the impact of resolving sea waves on wind turbine wake simulations. A case study is defined using reanalysis data to derive possible met-ocean conditions for a 15 MW offshore wind turbine in operation at a Mediterranean site. The simulation framework employs a one-way coupling between waves and aerodynamics, an aeroelastic actuator line model to compute the wind turbine rotor dynamics and its integration into a hybrid LES-URANS turbulent flow simulation of the surrounding wind field based on the

k - ω

SST Improved Delayed Detached Eddy Simulation. Atmospheric turbulence is accounted for by using a stochastic wind inflow generator based on the Kaimal velocity spectrum. Wave motion is resolved using a dynamic mesh solver. Results are provided and discussed in terms of the investigation of the effects of resolving the wave motion interaction on wind shear, rotor wake, turbine loads, and performance.

全球近海风电市场的快速增长凸显了对精确数值模拟的需求，以支持近海风电场的开发和设计，尤其是在地中海等地区，用于近海风电场设计的海洋气象条件测量数据非常稀少。本文提出了一个可靠的模拟框架，以评估解析海浪对风力涡轮机尾流模拟的影响。本文利用再分析数据进行了案例研究，以推导出在地中海某地运行的 15 兆瓦海上风力涡轮机可能遇到的海洋条件。模拟框架采用了波浪和空气动力学之间的单向耦合、气动弹性致动器线模型来计算风力涡轮机转子动力学，并将其集成到基于 k-ω SST 改进型延迟分离涡模拟的周围风场 LES-URANS 混合湍流模拟中。大气湍流是通过使用基于 Kaimal 速度频谱的随机风流入发生器来考虑的。使用动态网格求解器解决波浪运动问题。研究结果提供并讨论了解决波浪运动相互作用对风切变、转子尾流、涡轮机负载和性能的影响。

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引用次数: 0

Pore-scale lattice Boltzmann model for heat and mass transfers in frozen soil 冰冻土壤中热量和质量传递的孔隙尺度晶格玻尔兹曼模型

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109634

Zongwei Gan, Zheng Wang, Yaning Zhang, Wenke Zhao, Bingxi Li

The water and thermal characteristics of frozen soil will change during the freezing process, leading to frost heave disasters. Traditional macroscopic numerical methods have some difficulty in dealing with water and heat transport problems in frozen soil. The lattice Boltzmann method (LBM) can overcome these limitations by effectively capturing the complex interactions within porous media. In this study, a pore-scale lattice Boltzmann (LB) model was developed to simulate the coupled heat and mass transfer processes in frozen soil. The developed model incorporates a multicomponent multiphase pseudopotential and an enthalpy-based phase transition model. The relative errors of the model were 0.92 % ∼ 8.01 %, 2.46 % ∼ 14.14 %, and 0.02 % ∼ 13.56 % for the water contents at 12 h, 24 h, and 50 h, respectively, indicating that the current LB model can accurately describe the heat and water transfer characteristics in frozen soil. The inclusion of the freezing suction force in the model can reflect the actual water suction and transport process, resulting in variations of water content at different depths in the frozen soil.

在冻结过程中，冻土的水特性和热特性会发生变化，从而导致冻胀灾害。传统的宏观数值方法在处理冻土中的水和热传输问题时存在一些困难。晶格玻尔兹曼方法（LBM）可以有效地捕捉多孔介质中复杂的相互作用，从而克服这些局限性。本研究开发了一种孔隙尺度的晶格玻尔兹曼（LB）模型，用于模拟冻土中的热量和质量耦合传输过程。该模型包含一个多成分多相伪势和一个基于焓的相变模型。该模型在 12 h、24 h 和 50 h 时的含水量相对误差分别为 0.92 % ∼ 8.01 %、2.46 % ∼ 14.14 % 和 0.02 % ∼ 13.56 %，表明当前的 LB 模型能够准确描述冻土中的传热和传质特性。在模型中加入冻结吸力可以反映实际的吸水和输水过程，从而导致冻土不同深度含水量的变化。

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引用次数: 0

Swirling flow axial injection control in a Francis turbine: An LES study 混流式涡轮机中的漩涡流轴向喷射控制：LES 研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109643

E.V. Palkin, I.I. Lutchenko, M. Yu. Hrebtov, R.I. Mullyadzhanov, S.V. Alekseenko

This study investigates an active control strategy to suppress the precessing vortex core (PVC) and aims to extend the stable operation range of Francis turbine air model. Large-eddy simulation (LES) is used to analyze swirling flow under partial load conditions with axial jet injection within a narrow range of injection flow rates (1 to 5% of the main flow rate). The geometry, flow parameters and control technique are adopted from the experimental work of Litvinovet al. (2023). The effectiveness of the injection is assessed by analyzing the time-averaged velocity and fluctuations, wall pressure pulsations signal and its azimuthal decomposition. Additionally, the influence of axial injection on pressure fluctuations induced by the PVC and instantaneous pressure isosurfaces are examined. The results show that 3% injection flow rate most effectively mitigates the PVC dynamics while not causing other instabilities to occur. On the contrary, jets of 4% and 5% flow rate induce additional perturbations. Proper orthogonal decomposition of the pressure field is applied in this manuscript to reveal coherent structures of the swirling flow in cases without injection and with 3 and 5% jet flow rates.

本研究探讨了一种抑制前冲涡核（PVC）的主动控制策略，旨在扩大混流式涡轮空气模型的稳定运行范围。采用大涡流模拟（LES）分析了部分负荷条件下的漩涡流，并在较窄的喷射流量范围内（主流量的 1% 至 5% ）进行了轴向喷射。几何形状、流动参数和控制技术均采用 Litvinovet 等人（2023 年）的实验结果。通过分析时均速度和波动、壁面压力脉动信号及其方位分解，评估了注入的有效性。此外，还研究了轴向注入对聚氯乙烯引起的压力波动和瞬时压力等值面的影响。结果表明，3% 的喷射流量能最有效地缓解 PVC 动态，同时不会导致其他不稳定性的发生。相反，4% 和 5%的喷射流量会引起额外的扰动。本手稿对压力场进行了适当的正交分解，以揭示在无喷射、喷射流量为 3% 和 5% 的情况下漩涡流的相干结构。

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引用次数: 0

Direct numerical simulation of turbulent heat transfer in a channel with circular-arc ribs mounted on one wall 单壁安装圆弧肋片的通道中湍流传热的直接数值模拟

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109638

Wei-Jian Xiong , Jinglei Xu , Bing-Chen Wang , S.V. Mahmoodi-Jezeh

Turbulent heat convection in a cooling channel roughened with circular-arc ribs of different pitch-to-height ratios (

P / H = 3.0

, 5.0 and 7.5) are studied using direct numerical simulations (DNS). The pitch-to-height ratio effects on turbulent heat transfer are studied through analyses of the first- and second-order statistical moments of the temperature field. It is observed that the local Nusselt number increases remarkably near the rib centre due to the flow impingement on the rib windward side. Furthermore, the overall thermohydraulic efficiency of the whole ribbed channel enhances dramatically as the pitch-to-height ratio

P / H

increases. Meanwhile, the Reynolds analogy factor on the ribbed wall side decreases with an increasing value of

P / H

, indicating that the effect of heat transfer enhancement is counterbalanced by that of increasing hydraulic losses caused by the ribbed wall. It is found that temperature variance

〈 θ^{'} θ^{'} 〉

weakens under the rib effects, and further decreases with an increasing value of

P / H

. From the transport equation of

〈 θ^{'} θ^{'} 〉

, it is seen that both profiles of

〈 θ^{'} θ^{'} 〉

and its production term

P_{θ}

exhibit a dual-peak pattern at the midspan between two adjacent ribs, where the first peak near the wall enhances while the second peak in the internal shear layer weakens as the value of

P / H

increases. The quadrant analysis of heated turbulent motions indicates that hot sweep and cold ejection events dominate turbulent heat fluxes near the ribbed bottom wall. Interestingly, both hot sweep and cold ejection events enhance in the internal shear layer around the rib height. However, this enhancement effect weakens as the value of

P / H

increases.

通过直接数值模拟（DNS）研究了使用不同节高比（P/H=3.0、5.0 和 7.5）的圆弧肋条粗化冷却通道中的湍流热对流。通过分析温度场的一阶和二阶统计矩，研究了节高比对湍流传热的影响。结果表明，由于肋骨迎风面的气流冲击，肋骨中心附近的局部努塞尔特数显著增加。此外，随着螺距-高度比 P/H 的增大，整个带肋通道的整体热液压效率也显著提高。同时，肋壁侧的雷诺类比系数随 P/H 值的增大而减小，这表明传热增强的效果被肋壁造成的水力损失增加的效果所抵消。研究发现，温度方差〈θ′θ〉在肋骨效应下会减弱，并随着 P/H 值的增大而进一步减小。从〈θ′θ〉的输运方程可以看出，〈θ′θ〉及其产生项 Pθ 的剖面在两相邻肋片之间的中跨处都呈现出双峰模式，随着 P/H 值的增大，靠近壁面的第一个峰值增强，而内部剪切层的第二个峰值减弱。对加热湍流运动的象限分析表明，热掠和冷喷射事件在肋骨底壁附近的湍流热通量中占主导地位。有趣的是，热掠和冷喷射事件都会增强肋高附近的内部剪切层。不过，随着 P/H 值的增加，这种增强效应会减弱。

{"title":"Direct numerical simulation of turbulent heat transfer in a channel with circular-arc ribs mounted on one wall","authors":"Wei-Jian Xiong , Jinglei Xu , Bing-Chen Wang , S.V. Mahmoodi-Jezeh","doi":"10.1016/j.ijheatfluidflow.2024.109638","DOIUrl":"10.1016/j.ijheatfluidflow.2024.109638","url":null,"abstract":"<div><div>Turbulent heat convection in a cooling channel roughened with circular-arc ribs of different pitch-to-height ratios (<span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi><mo>=</mo><mn>3</mn><mo>.</mo><mn>0</mn></mrow></math></span>, 5.0 and 7.5) are studied using direct numerical simulations (DNS). The pitch-to-height ratio effects on turbulent heat transfer are studied through analyses of the first- and second-order statistical moments of the temperature field. It is observed that the local Nusselt number increases remarkably near the rib centre due to the flow impingement on the rib windward side. Furthermore, the overall thermohydraulic efficiency of the whole ribbed channel enhances dramatically as the pitch-to-height ratio <span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi></mrow></math></span> increases. Meanwhile, the Reynolds analogy factor on the ribbed wall side decreases with an increasing value of <span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi></mrow></math></span>, indicating that the effect of heat transfer enhancement is counterbalanced by that of increasing hydraulic losses caused by the ribbed wall. It is found that temperature variance <span><math><mrow><mo>〈</mo><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>〉</mo></mrow></math></span> weakens under the rib effects, and further decreases with an increasing value of <span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi></mrow></math></span>. From the transport equation of <span><math><mrow><mo>〈</mo><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>〉</mo></mrow></math></span>, it is seen that both profiles of <span><math><mrow><mo>〈</mo><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><msup><mrow><mi>θ</mi></mrow><mrow><mo>′</mo></mrow></msup><mo>〉</mo></mrow></math></span> and its production term <span><math><msub><mrow><mi>P</mi></mrow><mrow><mi>θ</mi></mrow></msub></math></span> exhibit a dual-peak pattern at the midspan between two adjacent ribs, where the first peak near the wall enhances while the second peak in the internal shear layer weakens as the value of <span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi></mrow></math></span> increases. The quadrant analysis of heated turbulent motions indicates that hot sweep and cold ejection events dominate turbulent heat fluxes near the ribbed bottom wall. Interestingly, both hot sweep and cold ejection events enhance in the internal shear layer around the rib height. However, this enhancement effect weakens as the value of <span><math><mrow><mi>P</mi><mo>/</mo><mi>H</mi></mrow></math></span> increases.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"110 ","pages":"Article 109638"},"PeriodicalIF":2.6,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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

Optimizing Trombe Wall performances: The impact of L-shaped fins on solar heating efficiency and building thermal comfort 优化 Trombe 墙的性能：L 型鳍片对太阳能加热效率和建筑热舒适度的影响

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109658

Khaoula Friji , Ons Ghriss , Abdallah Bouabidi , Yashar Aryanfar , Humberto Garcia Castellanos , Ali Keçebaş

This study delves into optimizing the thermal efficiency of Trombe Wall (TW) systems through the strategic integration of L-shaped fins, offering a novel approach to enhancing solar heating capabilities in buildings. By meticulously examining the effects of fin geometry-including thickness, length, and number-on the system’s performance, the research provides valuable insights into the design and operational optimization of TW systems. Using CFD simulations, the investigation reveals that specific fin configurations significantly improve heat transfer and air circulation within the TW, thereby augmenting the system’s thermal efficiency. Main results suggest that a fin thickness of 0.01 m and a fin length of 0.2 m, combined with an optimal number of fins, can achieve the most effective thermal performance, enhancing room temperature homogeneity while adhering to comfort standards. This comprehensive analysis underscores the critical role of fin geometry in solar heating technologies and paves the way for future innovations in sustainable building designs. The study’s implications extend beyond immediate energy savings, suggesting avenues for further research into material efficiencies and architectural integration, ultimately contributing to the broader adoption of renewable energy solutions in the construction sector.

本研究通过对 L 型鳍片的战略性集成，深入探讨了如何优化特洛姆贝墙（TW）系统的热效率，为提高建筑物的太阳能加热能力提供了一种新方法。通过细致研究翅片几何形状（包括厚度、长度和数量）对系统性能的影响，该研究为 TW 系统的设计和运行优化提供了宝贵的见解。通过 CFD 模拟，研究发现特定的翅片配置可以显著改善 TW 内部的热传递和空气循环，从而提高系统的热效率。主要结果表明，0.01 米的鳍片厚度和 0.2 米的鳍片长度，再加上最佳的鳍片数量，可以实现最有效的热性能，在提高室温均匀性的同时符合舒适标准。这项综合分析强调了翅片几何形状在太阳能加热技术中的关键作用，并为未来可持续建筑设计的创新铺平了道路。这项研究的意义不仅在于直接节约能源，还为进一步研究材料效率和建筑一体化提出了建议，最终有助于在建筑领域更广泛地采用可再生能源解决方案。

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引用次数: 0

A pressure-based unified solver for low Mach compressible two-phase flows 基于压力的低马赫可压缩两相流统一求解器

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109657

Rohit Rana, Nikhil Kumar Singh

In this study, a low Mach, pressure-based solver is developed for simulation of compressible two-phase flows. The two-dimensional solver developed on collocated grids in a finite volume framework adopts a unified formulation to efficiently handle different combinations of the two phases, including the cases where compressible and incompressible phases coexist. The pressure-based solver is coupled to a sharp interface capturing approach based on the coupled level set and volume of fluid method, which can accurately account for surface tension. The energy equation considered in the framework also accounts for dissipative effects due to viscosity and heat conduction. A variety of representative test cases of increasing complexity are considered to evaluate the performance of the solver in simulating compressibility effects while accurately resolving the interface. The results for Rayleigh-Taylor instability exhibit equivalent performance in both incompressible and low Mach regimes, while accounting for thermal effects arising due to compressibility. An isothermal bubble compression case due to a velocity field shows excellent agreement with existing results. The numerical results of bubble oscillations immersed in an incompressible liquid validated with one-dimensional and two-dimensional Rayleigh-Plesset model at different density ratios depict the ability of the unified approach to handle pressure waves effectively. This is further demonstrated by simulating bubble expansion inside an incompressible fluid due to decaying pressure.

本研究开发了一种基于压力的低马赫求解器，用于模拟可压缩两相流。该二维求解器是在有限体积框架内的拼接网格上开发的，采用了统一的表述方式，可有效处理两相的不同组合，包括可压缩相和不可压缩相共存的情况。基于压力的求解器与基于水平集和流体体积耦合方法的尖锐界面捕捉方法相耦合，可以准确地考虑表面张力。框架中考虑的能量方程还考虑了粘度和热传导引起的耗散效应。我们考虑了各种复杂程度不断增加的代表性测试案例，以评估求解器在模拟可压缩性效应的同时准确解决界面问题的性能。雷利-泰勒不稳定性的结果表明，在不可压缩和低马赫状态下都具有同等性能，同时考虑到了可压缩性引起的热效应。由速度场引起的等温气泡压缩情况与现有结果非常吻合。浸泡在不可压缩液体中的气泡振荡的数值结果，在不同密度比下通过一维和二维瑞利-普莱塞特模型验证，说明统一方法能够有效处理压力波。通过模拟气泡在不可压缩液体中因压力衰减而产生的膨胀，进一步证明了这一点。

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引用次数: 0

Physics-Informed neural network for level set method in vapor condensation 用于蒸汽凝结中水平集法的物理信息神经网络

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-16 DOI: 10.1016/j.ijheatfluidflow.2024.109651

Minghai Tang, Zhiqiang Xin, Lei Wang

Vapor condensation, a common physical phenomenon, is a complex multiphase flow problem involving mass transfer and heat transfer, which presents significant challenges in simulation, particularly regarding accuracy and computational efficiency. Hence, to improve simulation accuracy and achieve rapid prediction of condensation-generated water, this paper introduces an LS-PINN model, combining the precision of the level set method (LS) with the efficiency of the physics-informed neural network (PINN). It comprises two main components: i) a more accurate vapor condensation model is constructed by embedding Lee model as source terms into the two-phase flow model based on the level set method. And then the model is validated through the finite element method (FEM). ii) a dimensionless form suitable for PINN is derived of the governing equations (e.g., continuity equation, Navier-Stokes equations (without considering surface tension), heat equation and level set equation). On this basis, the LS-PINN model is constructed by incorporating the governing equations into the loss function, and trained through adaptive weight algorithm and sequential fixed strategy. Finally, three numerical examples are designed to validate the proposed model. The results show that the LS-PINN model can evaluate the liquid film thickness generated by condensation in one-dimensional and two-dimensional situations effectively. Furthermore, the total training time for the LS-PINN models is no more than 30 h, whereas the finite element calculation time takes approximately 130 h. The prediction time, which is measured in milliseconds, makes the PINN model highly suitable for applications where immediate responses are crucial, such as in digital twin systems.

蒸汽凝结是一种常见的物理现象，是一个涉及传质和传热的复杂多相流问题，给模拟带来了巨大挑战，尤其是在精度和计算效率方面。因此，为了提高模拟精度并实现对凝结水的快速预测，本文介绍了一种 LS-PINN 模型，该模型结合了水平集法（LS）的精度和物理信息神经网络（PINN）的效率。它包括两个主要部分：i) 通过将 Lee 模型作为源项嵌入到基于水平集法的两相流模型中，构建了一个更精确的蒸汽凝结模型。然后通过有限元法（FEM）对模型进行验证。ii）推导出适用于 PINN 的无量纲形式的控制方程（如连续性方程、纳维-斯托克斯方程（不考虑表面张力）、热方程和水平集方程）。在此基础上，通过将控制方程纳入损失函数来构建 LS-PINN 模型，并通过自适应权重算法和顺序固定策略进行训练。最后，设计了三个数值示例来验证所提出的模型。结果表明，LS-PINN 模型能有效评估一维和二维情况下冷凝产生的液膜厚度。此外，LS-PINN 模型的总训练时间不超过 30 小时，而有限元计算时间约为 130 小时。以毫秒为单位的预测时间使 PINN 模型非常适合数字孪生系统等需要即时响应的应用。

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引用次数: 0

Study of flow and heat transfer characteristics and structural optimization of parallel microchannel heat sink 平行微通道散热器的流动和传热特性及结构优化研究

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-15 DOI: 10.1016/j.ijheatfluidflow.2024.109654

Hengchao Li , Chao Dang , Yanming Kang , Hongwei Jia

This study conducted a comprehensive analysis of the flow-boiling heat transfer characteristics and structural optimization for Microchannel Heat Sinks (MCHS). The modified numerical model, based on the extended RPI wall boiling model, was validated against experimental data, showing satisfactory accuracy in predicting heat transfer coefficients and dryout phenomena across a mass flux range of 282 to 1033 kg/(m²s) and heat flux levels up to 116 W/cm². The research findings indicate that microchannel structure significantly influences vapor phase generation and distribution, and elevated heat flux can lead to a decline in heat transfer performance due to complete evaporation within the channels. The trapezoidal structure of the inlet collection tank induced vortices, which increased flow resistance and decreased flow rate in the initial sections of the channels, causing localized heat accumulation. The use of transverse grooves in the microchannels reduced the flow velocity standard deviation by 70 % and enhanced the average heat transfer coefficient by 30.9 %, effectively alleviating localized high temperatures. While the optimized structure improved overall performance, especially at lower flow rates, a performance decline was observed at higher flow rates. These results contribute to the development of a numerical model applicable to a broader range of flow boiling processes and offer a viable structural optimization strategy designed to enhance thermal management within electronic devices.

本研究对微通道散热器（MCHS）的流动沸腾传热特性和结构优化进行了全面分析。基于扩展 RPI 壁沸腾模型的修正数值模型与实验数据进行了验证，结果表明，在 282 至 1033 kg/(m2s) 的质量通量范围和高达 116 W/cm2 的热通量水平上，预测传热系数和干涸现象的准确性令人满意。研究结果表明，微通道结构对气相的生成和分布有显著影响，热通量升高会导致通道内完全蒸发，从而导致传热性能下降。入口收集槽的梯形结构会诱发涡流，增加流动阻力，降低通道初始段的流速，造成局部热量积聚。在微通道中使用横向凹槽可将流速标准偏差降低 70%，并将平均传热系数提高 30.9%，从而有效缓解局部高温问题。虽然优化后的结构提高了整体性能，尤其是在较低流速下，但在较高流速下性能有所下降。这些结果有助于开发一种适用于更广泛的流动沸腾过程的数值模型，并提供了一种可行的结构优化策略，旨在加强电子设备的热管理。

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引用次数: 0

High-fidelity simulation of turbulent mixed convection in pipe flow 管道流中湍流混合对流的高保真模拟

IF 2.6 3区工程技术 Q2 ENGINEERING, MECHANICAL

International Journal of Heat and Fluid Flow

Pub Date : 2024-11-14 DOI: 10.1016/j.ijheatfluidflow.2024.109640

Rodrigo Vicente Cruz , Cédric Flageul , Eric Lamballais , Vladimir Duffal , Erwan Le Coupanec , Sofiane Benhamadouche

Direct Numerical Simulations are performed to provide a fine description of the turbulent mixed convection flow in an upward heated pipe. The introduction of buoyancy forces in this type of flow gives rise to different non-trivial phenomena such as laminarisation and a bi-stable behaviour, capable of modifying the flow characteristics in a deep and non-monotonic way. The present work aims therefore to establish a high-fidelity and publicly accessible database, containing first and second-order accurate turbulence statistics, as well as budgets of various one-point correlations of turbulent quantities, namely the turbulent kinetic energy and its associated dissipation rate, the temperature variance and its associated dissipation rate, the Reynolds stress tensor and the turbulent heat flux vector. Besides, the coexistence of two and very distinct statistically stationary solutions for a same set of flow parameters is also investigated. These two states are referred to as weak- and strong-turbulence regimes. The budget analyses performed here, such as the original ones presented for the budgets of the Reynolds stresses, contribute to gaining further understanding of the physics of mixed convection flows. The results issued from the present study shall also support the validation of lower-fidelity numerical models, such as Large Eddy Simulation, RANS and hybrid RANS/LES approaches.

直接数值模拟对向上加热管道中的湍流混合对流进行了精细描述。在这种流动中引入浮力会产生不同的非难现象，如层流化和双稳态行为，能够以深度和非单调的方式改变流动特性。因此，目前的工作旨在建立一个高保真和可公开访问的数据库，其中包含一阶和二阶精确湍流统计数据，以及各种湍流量的单点相关性预算，即湍流动能及其相关耗散率、温度方差及其相关耗散率、雷诺应力张量和湍流热通量矢量。此外，还研究了同一组流动参数下两种截然不同的统计静止解共存的情况。这两种状态被称为弱湍流和强湍流状态。这里进行的预算分析，如最初提出的雷诺应力预算分析，有助于进一步了解混合对流的物理原理。本研究得出的结果还有助于验证低保真数值模型，如大涡模拟、RANS 和 RANS/LES 混合方法。

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