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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

A Novel Asymmetric Check Microvalve for Suppressing Flow Boiling Instability in Microchannels

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Journal of Thermal Science 2024年第6期33卷 2336-2347页

作者： ZHOU Fan ZHAO Yang YIN Ershuai hu dinghua LI Qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

Flow boiling in microchannels has attracted wide attention due to its excellent heat transfer capability,but flow boiling instability is a huge challenge limiting its *** can lead to a series of problems,such as uneven flow distribution,temperature and pressure drop *** work proposes a novel asymmetric check microvalve(ACMV)structure,exhibiting high ratio of resistance between the reverse and forward *** results show the reverse pressure drop of the ACMV structure is 2.06 times that of the forward pressure drop,and the forward flow resistance of the ACMV structure is 16%smaller than that of the conventional inlet *** addition,bubble dynamics of an isolated bubble in the generated channel under dual outlet condition was numerically *** is found that the bubble grows symmetrically in the rectangular channel upstream and *** distance of bubble movement downstream in the microchannel with ACMV is three times that of the microchannel with inlet *** microchannel with ACMV can suppress the backflow of isolated bubble better than microchannel with inlet ***,the growth of the bubble downstream extends the effective evaporation domain,which contributes to the enhanced bubble growth *** ACMV is expected to be a potential replacement for the conventional inlet restrictor,which provides a novel and efficient solution for future heat dissipation from high power devices.

关键词： flow boiling instability topology optimization microchannel bubble dynamics

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

氧化铝纳米流体液滴瞬态蒸发速率的演化特性分析

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化工进展 2022年第7期41卷 3493-3501页

作者：李钰璨胡定华刘锦辉南京理工大学电子设备热控制工信部重点实验室江苏南京210094

以氧化铝纳米流体液滴为研究对象,本文建立了基于任意拉格朗日-欧拉(ALE)法的液滴蒸发瞬态模型,对液滴蒸发过程中蒸汽浓度、纳米颗粒浓度、温度等进行多物理场耦合,并考虑了Marangoni流对液滴蒸发的影响,同时研究还结合蒸发实验可视化结... 详细信息

以氧化铝纳米流体液滴为研究对象,本文建立了基于任意拉格朗日-欧拉(ALE)法的液滴蒸发瞬态模型,对液滴蒸发过程中蒸汽浓度、纳米颗粒浓度、温度等进行多物理场耦合,并考虑了Marangoni流对液滴蒸发的影响,同时研究还结合蒸发实验可视化结果,分析了氧化铝纳米流体液滴的瞬态蒸发速率随时间的演化规律,讨论了颗粒体积分数和基板温度对蒸发模式的影响。结果表明,在液滴蒸发过程开始时,纳米流体液滴保持定接触半径蒸发模式,气液界面面积逐渐减小,瞬态蒸发速率也呈逐渐减小的趋势;当颗粒体积分数增大至26%时,瞬态蒸发速率曲线达到驻点;蒸发接近完全时,由于Marangoni流影响了内部流场、强化了内部传热,且液滴在已沉积在基板上的颗粒表面形成液膜,瞬态蒸发速率迅速增大。

关键词：蒸发数值模拟传热纳米流体液滴

石墨/铝合金复合导热板强化石蜡相变蓄热研究

同方期刊数据库博看期刊评论

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工程热物理学报 2023年第12期44卷 3399-3406页

作者：句子涵于坤洋李强胡定华南京理工大学电子设备热管理工信部重点实验室南京210094 中国人民解放军93126部队北京100084

本文对“三明治”结构的石墨/铝合金复合导热板强化石蜡的相变蓄热特性进行了数值研究,探究泡沫金属、平板翅片以及复合导热板三种传热结构对石蜡相变蓄热过程的影响。然后本文在石墨/铝合金复合导热板的结构基础上添加了二级翅片来强... 详细信息

本文对“三明治”结构的石墨/铝合金复合导热板强化石蜡的相变蓄热特性进行了数值研究,探究泡沫金属、平板翅片以及复合导热板三种传热结构对石蜡相变蓄热过程的影响。然后本文在石墨/铝合金复合导热板的结构基础上添加了二级翅片来强化传热。研究表明:石墨/铝合金复合导热板强化石蜡相变蓄热的性能明显优于其他传热结构,呈现出自导热板向垂直于板两侧方向递减的温度分布,使得腔体内融化最为均匀,芯片温升最小。添加二级肋片后热源温升减小了15.87%,有效工作时间延长64.68%。

关键词：石蜡相变蓄热石墨/铝合金复合导热板肋片