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纳米孔内液体蒸发建模及不凝气影响研究

中国科学：物理学、力学、天文学 2024年第2期54卷 52-61页

作者：李冉夏国栋北京工业大学环境与生命学部北京100124

纳米多孔介质内的液体蒸发过程及不凝气的影响机制是能源化工等工程领域中的关键科学问题,基于气体动理论分析了蒸气在纳米孔道内的流动阻力特征,结合Boltzmann方程矩方法建立了单组分蒸发的理论模型,采用直接蒙特卡罗方法模拟了含不凝... 详细信息

纳米多孔介质内的液体蒸发过程及不凝气的影响机制是能源化工等工程领域中的关键科学问题,基于气体动理论分析了蒸气在纳米孔道内的流动阻力特征,结合Boltzmann方程矩方法建立了单组分蒸发的理论模型,采用直接蒙特卡罗方法模拟了含不凝气条件下的纳米孔蒸发过程,基于模拟数据构建了蒸发速率的预测关联式.结果表明:纳米孔的蒸发过程可分为孔内蒸气流动、孔外动力学运动和对流-扩散流动3个部分,孔隙率和蒸气所占孔道长径比对蒸发速率具有显著影响,孔隙率越大则不凝气对蒸发速率的影响程度越大,当气体段孔道长径比为2.5时液体蒸发速率可降低约50%.基于单组分模型和无量纲关联式的蒸发速率预测结果与直接蒙特卡罗模拟结果的相对误差基本为±10%.

关键词：纳米孔蒸发不凝气直接蒙特卡罗模拟气体动理论

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近壁球形颗粒的曳力特性研究

工程热物理学报 2024年第3期45卷 755-763页

作者：霍晓昱王军夏国栋北京工业大学强化传热与过程节能教育部重点实验室暨传热与能源利用北京市重点实验室北京100124

本文研究了球形颗粒在近壁区域内的曳力特性,基于气体动理论方法推导得到了自由分子区内近壁颗粒沿垂直于平壁方向运动时所受曳力的表达式,其计算结果与直接蒙特卡洛模拟结果一致。计算并分析了动量适应系数、壁面温度等参数对近壁颗粒... 详细信息

本文研究了球形颗粒在近壁区域内的曳力特性,基于气体动理论方法推导得到了自由分子区内近壁颗粒沿垂直于平壁方向运动时所受曳力的表达式,其计算结果与直接蒙特卡洛模拟结果一致。计算并分析了动量适应系数、壁面温度等参数对近壁颗粒所受曳力的影响规律和机制。当壁面动量适应系数为零时,近壁效应消失;当壁面温度高于气体温度时,近壁效应使得颗粒所受曳力增大;当壁面温度低于气体温度且颗粒速度较小时,可能出现曳力方向与颗粒运动方向相同的情况。

关键词：自由分子区曳力近壁效应气体动理论

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固液界面热阻的温度依赖特性模拟研究

北京工业大学学报 2024年第7期50卷 864-871页

作者：王军李海洋夏国栋北京工业大学传热强化与过程节能教育部重点实验室暨传热与能源利用北京市重点实验室北京100124

基于非平衡态分子动力学模拟方法,研究了系统温度及固液结合强度对固液界面传热的影响规律。模拟结果表明,固液界面热阻随着系统温度的升高而降低,并且亲水性界面的界面热阻温度依赖性较弱。基于微观热流密度计算式的分析表明,随着系统... 详细信息

基于非平衡态分子动力学模拟方法,研究了系统温度及固液结合强度对固液界面传热的影响规律。模拟结果表明,固液界面热阻随着系统温度的升高而降低,并且亲水性界面的界面热阻温度依赖性较弱。基于微观热流密度计算式的分析表明,随着系统温度升高,动能项和维里项的贡献均逐渐增大,因而固液界面传热增强,但是动能项占比逐渐增大,维里项占比逐渐降低;随着固液结合强度逐渐增大,界面吸附效应增强,维里项贡献明显增大,这是较强的固液相互作用能够强化界面传热的主要原因。

关键词：界面热阻分子动力学模拟固液界面温度依赖性润湿性微观热流密度

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自由分子区内的非球形颗粒曳力计算

力学学报 2024年第5期56卷 1251-1260页

作者：常心泉张克学王军夏国栋北京工业大学机械与能源工程学院北京100124

基于气体动理论方法,推导得到非球形颗粒所受曳力的通用表达式,并针对球形颗粒、圆柱体颗粒、椭球体颗粒和圆锥体颗粒等几种常见的非球形颗粒,得到其所受曳力的具体解析计算式.该模型适用于气体分子与颗粒表面仅发生一次碰撞的凸面体,... 详细信息

基于气体动理论方法,推导得到非球形颗粒所受曳力的通用表达式,并针对球形颗粒、圆柱体颗粒、椭球体颗粒和圆锥体颗粒等几种常见的非球形颗粒,得到其所受曳力的具体解析计算式.该模型适用于气体分子与颗粒表面仅发生一次碰撞的凸面体,假设气体分子与颗粒间的相互作用符合Maxwell镜面反射-漫反射模型,计算气体分子与颗粒碰撞过程中的微元动量传递,进而在颗粒表面积分得到非球形颗粒所受曳力的通用表达式.计算结果表明,颗粒所受曳力与其自身的几何形状和在流场中的取向有关.但是,基于非球形颗粒得到的计算式较为复杂,不便于实际应用.考虑到在自由分子区内,当外势场较弱时,颗粒的高速布朗旋转运动会使其取向分布近似为均匀的随机分布,文章推导得到了不同形状颗粒在均向分布下所受均向曳力的计算式,结果表明非球形颗粒所受均向曳力正比于颗粒表面积,且比例系数与颗粒形状无关.此算法避免了求解具体非球形颗粒受力计算的繁琐计算过程,更便于实际应用.

关键词：非球形颗粒曳力自由分子区气体动理论

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纳米凹槽表面结冰的分子动力学模拟研究

河南师范大学学报（自然科学版） 2024年第1期52卷 93-99,F0002页

作者：王军张悦夏国栋北京工业大学传热强化与过程节能教育部重点实验室传热与能源利用北京市重点实验室北京100124

采用分子动力学模拟方法建立了水在金表面结冰的模型,在疏水表面上引入亲水纳米凹槽结构,模拟研究了纳米凹槽表面上的冰成核过程,揭示了凹槽深宽比对冰成核的影响规律和机制.结果表明,在疏水表面引入亲水纳米凹槽结构并改变表面的凹槽宽... 详细信息

采用分子动力学模拟方法建立了水在金表面结冰的模型,在疏水表面上引入亲水纳米凹槽结构,模拟研究了纳米凹槽表面上的冰成核过程,揭示了凹槽深宽比对冰成核的影响规律和机制.结果表明,在疏水表面引入亲水纳米凹槽结构并改变表面的凹槽宽度,可以调节疏水表面的结冰过程.当纳米凹槽与六边形冰结构相匹配时,凹槽内部更容易形成冰核,可以提高疏水表面的冰成核率的效果,其表面成核率接近与亲水表面成核率.当纳米凹槽结构与六边形冰结构不匹配时,凹槽内不易形成冰核,结冰过程受到抑制.为提高疏水表面成核率提供了新方法,为控制疏水表面冰成核位置和冰生长方向提供了新思路.

关键词：冰成核凹槽表面纳米结构

Thermal Transport through Solid-Liquid Interface:Effect of the Interfacial Coupling and Nanostructured Surfaces

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Journal of Thermal Science 2022年第4期31卷 1167-1179页

作者： LI Haiyang WANG Jun xia guodong MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy Conversion Beijing University of TechnologyBeijing 100124China

The solid-liquid interfacial thermal transport depends on the physical properties of the interfaces,which have been studied extensively in open ***,the fundamental understanding on the mechanism of the solid-liquid interfacial thermal transport is far from *** the present paper,heat transfer through solid-liquid interfaces is studied based on the non-equilibrium molecular dynamics *** is shown that the interfacial heat transfer can be enhanced by increasing interfacial coupling strength or introducing the nanostructured *** underlying mechanism of the interfacial thermal transport is analyzed based on the calculation results of the heat flux distribution,potential mean force,and the vibrational density of states at the interfacial *** is found that the interfacial thermal transport is dominated by the kinetic and virial contributions in the interface *** enhancement of the interfacial heat transfer can be attributed to the fluid adsorption on the solid surface under a strong interfacial interaction or by the nanostructured solid surfaces,which reduce the mismatch of the vibrational density of states at the solid-liquid interface region.

关键词： solid-liquid interface molecular dynamics simulation thermal resistance nanostructure

Thermophoresis of nanoparticles hotter/colder than the surrounding dilute gases

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Particuology 2022年第4期20卷 95-102页

作者： Junjie Su Jie Cui Jun Wang guodong xia MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China

Aerosol particles suspended in a diluted gas with non-uniform temperature distribution are expected to experience a thermophoretic *** theoretical treatment of thermophoresis,it is usually assumed that the particle temperature is equal to the surrounding gas ***,this might not always be the *** some particular applications,the particle temperature can significantly differ from the gas *** the present paper,we theoretically investigate the effect of the particle tempera-ture on the thermophoresis of nanoparticles in the free molecule *** formulas for the thermophoretic force and thermophoretic velocity are obtained based on the gas kinetic *** exam-ples,a spherical Ag nanoparticle suspended in a dilute He gas is considered,and the Rudyak-Krasnolutski potential is employed to model the gas-particle *** is found that the influence of the particle temperature on the thermophoresis of nanoparticles can be *** increasing particle size,the error due to the equal gas-particle temperature assumption can be neglected.

关键词： Thermophoresis Particle temperature Nanoparticles Free molecule regime

Tunable Thermal Rectification and Negative Differential Thermal Resistance in Gas-Filled Nanostructure with Mechanically-Controllable Nanopillars

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Journal of Thermal Science 2022年第4期31卷 1084-1093页

作者： LI Fan LI Haiyang WANG Jun xia guodong HWANG Gisuk MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China Department of Mechanical Engineering Wichita State University Wichita KS 67260USA

In this study,by using the nonequilibrium molecular dynamics and the kinetic theory,we examine the tailored nanoscale thermal transport via a gas-filled nanogap structure with mechanically-controllable nanopillars in one surface only,i.e.,changing nanopillar *** is found that both the thermal rectification and negative differential thermal resistance(NDTR)effects can be substantially enhanced by controlling the nanopillar *** maximum thermal rectification ratio can reach 340%and the△T range with NDTR can be significantly enlarged,which can be attributed to the tailored asymmetric thermal resistance via controlled adsorption in height-changing nanopillars,especially at a large temperature *** tunable thermal rectification and NDTR mechanisms provide insights for the design of thermal management systems.

关键词： thermal rectification negative differential thermal resistance kinetic theory nanopillars

Analysis of flow and heat transfer characteristics of micro-pin fin heat sink using silver nanofluids

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Science China(Technological Sciences) 2012年第1期55卷 155-162页

作者： ZHOU MingZheng xia guodong CHAI Lei LI Jian ZHOU LiJun Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of Education College of Environmental and Energy Engineering Beijing University of Technology Beijing 100124 China

Silver nanofluids with three different volume fractions are prepared by a one-step chemical reduction method(Ultra-sound-assisted Membrane Reaction(UAMR)).The convective heat transfer and friction characteristics of silver nanofluid in micro-pin fin heat sink are investigated *** results indicate that the pressure drops of nanofluids with different volume fractions have little *** to the base fluid(polyvinylpyrrolidone(PVP) solution),the pressure drop of nanofluids increases slightly at the same volume flow *** the flow rate is small,the increment is not *** in-troduction of surfactant increases the fluid viscosity,so the pressure drops of nanofluids are larger than those of pure water,under the same flow ***,the maximum difference is no more than 10%.The volume fraction of silver nanoparticles significantly affects the convection heat transfer coefficient of micro-pin fin heat *** presence of nanoparticles improves significantly the heat transfer ***,high viscosity of the nanofluids hinders the heat transfer strengthening effect of *** the present work,when the volume fraction of silver particles reaches to 0.012%,the thermal resistance of nanofluid gradually becomes lower than that of deionized water,which indicates the integrated heat transfer enhancement of nanofluids.

关键词： nanofluids micro-pin fin heat transfer viscosity volume fraction