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液滴撞击振动壁面传热特性影响的数值研究

工程热物理学报 2024年第8期45卷 2466-2474页

作者：胡定华朱劭恺于坤洋李强南京理工大学能源与动力工程学院南京210094 中国人民解放军93126部队北京100084

随着车载、机载等交通输运系统电子设备散热需求的不断提高,喷雾冷却的应用领域逐渐增加、应用环境逐渐复杂,确定振动对喷雾冷却传热过程的影响有重要意义。基于VOF方法和动网格模型,建立了液滴撞击垂直振动壁面的数值模型,研究了壁面... 详细信息

随着车载、机载等交通输运系统电子设备散热需求的不断提高,喷雾冷却的应用领域逐渐增加、应用环境逐渐复杂,确定振动对喷雾冷却传热过程的影响有重要意义。基于VOF方法和动网格模型,建立了液滴撞击垂直振动壁面的数值模型,研究了壁面振动速度变化形式和振动参数变化对传热过程的影响。结果表明:对于方波、余弦波和三角波三种不同振动速度变化形式,在相同最大速度和周期下,壁面速度余弦波变化在最大速度较小时液滴有最高的传热能力;随着振幅和频率的增加,壁面振动先后通过改变接触面积和接触时间影响传热;振幅和频率较小时,壁面振动对传热有抑制作用,随振幅和频率的增大传热逐渐增强,频率过大时,虽然撞击点处温度降低但总传热能力减小。

关键词：液滴撞击壁面振动传热数值模拟

抗加速度双切线弧流道内气泡动力学行为数值与可视化研究

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化工学报 2024年第9期75卷 3074-3082页

作者：唐昊胡定华李强张轩畅韩俊杰工信部电子设备热控制重点实验室南京理工大学能源与动力工程学院江苏南京210094 航空工业西安航空计算技术研究所陕西西安710068

机载电子设备的散热系统设计对飞行器的长航时安全运行具有重要意义。设计了抗加速度的双切线弧流道,针对流道内的气泡动力学行为,开展了基于VOF多相流模型的数值分析与基于高速相机的可视化研究。仿真分析表明,相比于直流道,双切线弧... 详细信息

机载电子设备的散热系统设计对飞行器的长航时安全运行具有重要意义。设计了抗加速度的双切线弧流道,针对流道内的气泡动力学行为,开展了基于VOF多相流模型的数值分析与基于高速相机的可视化研究。仿真分析表明,相比于直流道,双切线弧流道中的气泡在流经弯管时,由于离心力的作用,会破裂成小气泡并被甩到远离加热面的位置,使得气液分离。30°双切线弧流道分离能力最弱,但残留在壁面的气泡最少;60°双切线弧流道分离能力最强,但壁面处气泡不易流动。对45°双切线弧流道进行了可视化实验研究,可视化结果与仿真分析一致。仿真计算表明,当流速为1 m/s时,45°双切线弧流道可以有效抵抗5g的加速度。

关键词：气泡离心分离两相流流体动力学可视化

Numerical study on flow and heat transfer characteristics of microchannel designed using topological optimizations method

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Science China(Technological Sciences) 2020年第1期63卷 105-115页

作者： hu dinghua ZHANG ZhiWei LI Qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment Nanjing University of Science and Technology

Microchannel has demonstrated advantages in the thermal management of integrated chip. In this study, the topology optimization method is applied for designing a topological microchannel to optimize the performances of both heat dissipation and pressure drop. To validate the performance of the topological structure, the flow and heat transfer characteristics of topological microchannel under non-uniform heating flux are numerically studied. The topological structure is designed to cool a heating area of 10 mm×10 mm with 4 hotspots. Heat flux is 40 W/cm^2 in the hotspot area, while it is only 15 W/cm^2 in the rest heating area. The results of heat dissipation performance and pressure drop are compared with those of conventional straight microchannel. Numerical result shows that, compared to the straight microchannel, the hotspot temperature and pressure drop of topological microchannel can be reduced by 4 and 0.6 k Pa, respectively, under the flow rate of 2.2×10^-4 kg/s. The coefficient of performance(COP) of topological microchannel can be 16.1% better than that of straight microchannel, which can be attributed to the effects of optimized bifurcation and confluence structural of topological microchannel.

关键词： topology optimization microchannel heat dissipation pressure drop hotspot

High-efficiency magnetophoretic separation based on synergy of magnetic force field and flow field in microchannels

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Science China(Technological Sciences) 2011年第12期54卷 3311-3319页

作者： WU XinYu WU huiYing hu dinghua School of Mechanical and Power Engineering Shanghai Jiao Tong University Shanghai 200240 China

Magnetophoresis is one of the most important separation methods in biological and chemical engineering. In this paper,a novel impact parameter on separation efficiency,i.e.,the angle between the vectors of magnetic force and fluid velocity,was derived from the basic equation describing the motion of magnetic beads in microchannels. It is proposed that one of the most important approaches for separation efficiency enhancement is to improve the coordination of magnetic force field and fluid flow field. A T-shaped microchannel magnetophoretic separator was designed based on the angle. And then a two-dimensional dynamic model of magnetic beads moving in microchannels was established to study the separation efficiency of T-shaped microseparator by combined use of finite element method and Runge-Kutta method. The results show that the capture effi-ciency of T-shaped microseparator is much higher than that of the straight microseparator at the same conditions. For small magnetic beads at high fluid velocities,the designed T-shaped microseparator could still keep high separation efficiency whereas the conventional straight microseparator fails to separate the magnetic beads. Further analysis shows that the mechanism of separation efficiency enhancement lies in the synergy of magnetic force field and flow field,which directly leads to large deflected velocity of the magnetic beads from the main stream,and thus increasing the separation efficiency. It is anticipated that the results in this paper are theoretically helpful for the optimum design of highly efficient magnetophoretic separators.

关键词： magnetophoretic separation T-shaped microchannel field synergy separation efficiency

Visualization study on atomization characteristics and heat transfer performance of R1336mzz flash spray cooling

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Science China(Technological Sciences) 2021年第10期64卷 2099-2109页

作者： ZHANG ZhiWei hu dinghua LI Qiang LIU Chao ZHOU Fan MIIT Key Laboratory of Thermal Control of Electronic Equipment Nanjing University of Science and TechnologyNanjing 210094China

Visualization experiments are carried out to investigate the atomization characteristics of R1336mzz flash spray *** influences of superheat,spray distance,and nozzle orifice diameter on spray cooling performance are analyzed *** the superheat increases,finer droplets and thinner liquid film are observed;this is helpful to improve the two-phase heat transfer *** atomization angle under high superheat is also observed for flash spray cooling,and it benefits for reducing the spray *** can be found that when the inlet superheat is 19.8℃ and the spray distance is 6 mm,the critical heat flux(CHF)reaches 251 W/cm^(2) and the maximum heat transfer coefficient(HTC)reaches 37.4 kW/(m^(2)℃),which are 55%and 11.6%higher than those when the inlet subcooling is 6.9℃ and the spray distance is 12 mm,*** flash spray reduces the spray distance,which benefits for designing compact spray cooling *** addition,the nozzle orifice diameter has great influence on the cooling performance of flash spray,and the choice of the nozzle depends on the *** study provides a physical insight into the heat transfer enhancement in flash spray cooling.

关键词： flash spray cooling superheat spray distance nozzle diameter R1336mzz critical heat flux

Microchannel cooling technique for dissipating high heat flux on W/Cu flat-type mock-up for EAST divertor

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Plasma Science and Technology 2022年第9期24卷 134-144页

作者： Mingxiang LU Le HAN Qi ZHAO Juncheng QIU Jianhong ZHOU dinghua hu Nanyu MOU Xuemei CHEN MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094People’s Republic of China Institute of Plasma Physics Hefei Institutes of Physical ScienceChinese Academy of SciencesHefei 230031People’s Republic of China

As an important component of tokamaks,the divertor is mainly responsible for extracting heat and helium ash,and the targets of the divertor need to withstand high heat flux of 10 MW m-2 for steady-state *** this study,we proposed a new strategy,using microchannel cooling technology to remove high heat load on the targets of the *** results demonstrated that the microchannel-based W/Cu flat-type mock-up successfully withstood the thermal fatigue test of 1000 cycles at 10 MW m^(-2)with cooling water of 26 l min^(-1),30°C(inlet),0.8 MPa(inlet),15 s power on and 15 s dwell time;the maximum temperature on the heat-loaded surface(W surface)of the mock-up was 493°C,which is much lower than the recrystallization temperature of W(1200°C).Moreover,no occurrence of macrocrack and‘hot spot’at the W surface,as well as no detachment of W/Cu tiles were observed during the thermal fatigue *** results indicate that microchannel cooling technology is an efflcient method for removing the heat load of the divertor at a low flow *** present study offers a promising solution to replace the monoblock design for the EAST divertor.

关键词： microchannel divertor flat-type high heat flux test EAST

Al2O3纳米流体液滴蒸发特性的数值模拟研究

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化工学报 2019年第11期70卷 4199-4206页

作者：金铭胡定华李强范德松南京理工大学电子设备热控制工信部重点实验室

纳米流体液滴蒸发现象在电子设备冷却、喷墨打印以及医学检测等领域都有广泛应用。为了研究水基Al2O3纳米流体液滴的蒸发特性,建立了纳米流体液滴蒸发的二维瞬态模型,考虑了纳米颗粒输运行为以及液滴内部流动的影响,并采用任意拉格朗日... 详细信息

纳米流体液滴蒸发现象在电子设备冷却、喷墨打印以及医学检测等领域都有广泛应用。为了研究水基Al2O3纳米流体液滴的蒸发特性,建立了纳米流体液滴蒸发的二维瞬态模型,考虑了纳米颗粒输运行为以及液滴内部流动的影响,并采用任意拉格朗日-欧拉法(ALE)捕捉气液运动界面。基于所建立的模型,分析了水基Al2O3纳米流体液滴内部Marangoni流、纳米颗粒初始浓度以及基板温度对纳米流体液滴蒸发特性的影响规律。结果表明,液滴内部Marangoni流会影响气液界面温度分布和蒸发速率。由于液滴内部纳米颗粒浓度分布和气液界面温度发生变化,纳米流体液滴的蒸发速率随着纳米颗粒初始浓度和基板温度升高而增加。

关键词：纳米流体氧化铝蒸发数值模拟颗粒浓度

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振动对液滴撞击壁面铺展特性的影响

航空学报 2023年第16期44卷 53-64页

作者：朱劭恺胡定华李强南京理工大学电子设备热控制工信部重点实验室南京210094

在航空航天领域的喷雾冷却过程中,被冷却器件时常处于振动状态,因此确定振动对喷雾冷却液滴撞击壁面动态行为的影响有重要意义。基于VOF方法和动网格模型建立了液滴撞击垂直简谐振动壁面的数值模型,研究了壁面振幅、频率和初始相位角对... 详细信息

在航空航天领域的喷雾冷却过程中,被冷却器件时常处于振动状态,因此确定振动对喷雾冷却液滴撞击壁面动态行为的影响有重要意义。基于VOF方法和动网格模型建立了液滴撞击垂直简谐振动壁面的数值模型,研究了壁面振幅、频率和初始相位角对铺展特性的影响。结果表明,相同撞击条件下,壁面振动不仅影响着最大铺展因子和铺展时间的大小,还会使液膜发生断裂抑制和飞溅行为;初始相位角为0°时,铺展时间随振幅和频率的增加而减小;最大铺展因子随振幅的增加一直增加,振幅较小时,最大铺展因子随频率的增加先增加后减小,在共振频率处取得最大值且减小程度随振幅的增大逐渐降低,振幅较大时,最大铺展因子随频率的增加变为一直增加;铺展时间和最大铺展因子随初始相位角的变化趋势主要与频率有关,频率较小时,初始相位角对铺展时间和最大铺展因子无明显影响,随着频率的增加,铺展时间先后在180°和90°相位最大,最大铺展因子先后在0°和180°相位最大。

关键词：液滴撞击壁面振动铺展特性动态行为铺展因子

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石蜡-膨胀石墨复合相变材料热导率研究

化工学报 2021年第8期72卷 4425-4432页

作者：林肯许肖永李强胡定华南京理工大学能源与动力工程学院江苏南京210094

在石蜡(PA)中复合添加膨胀石墨(EG)是提高石蜡基相变材料导热性能的一种常见方法,准确预测PA-EG复合相变材料的热导率对于其应用十分重要。通过对EG质量分数小于20%的PA-EG复合相变材料微观结构特征的分析,建立了基于EG纤维在PA中均匀... 详细信息

在石蜡(PA)中复合添加膨胀石墨(EG)是提高石蜡基相变材料导热性能的一种常见方法,准确预测PA-EG复合相变材料的热导率对于其应用十分重要。通过对EG质量分数小于20%的PA-EG复合相变材料微观结构特征的分析,建立了基于EG纤维在PA中均匀分散的微观结构几何模型,数值模拟了完全均匀分散PA-EG单元体的相变过程,分析了EG质量分数及其粒径对PA-EG复合相变材料等效热导率的影响规律,并提出了可适用于不同制备方法的PA-EG复合相变材料热导率预测模型。模型预测结果与已报道EG质量分数小于20%的PA-EG复合相变材料实验结果能较好吻合,误差小于15.1%。

关键词：石蜡膨胀石墨复合相变材料传热相变