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表面特性对棘齿型Knudsen泵气体分离特性影响的模拟研究
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作者 韩峰 张志军 +1 位作者 张世伟 王晓伟 《真空》 CAS 2024年第3期13-19,共7页
Knudsen泵作为一种微型泵,在微机电系统(MEMS)中具有广泛应用。本文提出了一种具有不同表面反射系数的棘齿型Knudsen泵,通过直接模拟蒙特卡罗(DSMC)方法对该泵内He-Xe混合气体流动特性进行了数值模拟研究。结果表明:表面反射特性对Knud... Knudsen泵作为一种微型泵,在微机电系统(MEMS)中具有广泛应用。本文提出了一种具有不同表面反射系数的棘齿型Knudsen泵,通过直接模拟蒙特卡罗(DSMC)方法对该泵内He-Xe混合气体流动特性进行了数值模拟研究。结果表明:表面反射特性对Knudsen泵内的流场特性和气体分离特性影响巨大,不同的表面反射特性导致了Knudsen泵内不同的热驱流动机理;三角形倾斜边的α_(n)=σ_(t)=0时Knudsen泵内主要热驱流动为辐射流,有利于气体分离,而α_(n)=σ_(t)=1时Knudsen泵内主要热驱流动为热边缘流,对气体分离没有明显有利作用;三角形倾斜边的α_(n)=σ_(t)=0时He和Xe的速度和扩散速度在三角形棘齿上顶点附近差异最大,而α_(n)=σ_(t)=1时在三角形棘齿左侧顶点附近差异最大;越轻的气体流动速度和扩散速度越快。本文可为实际工程应用中微型气体分离装置的设计和生产提供理论依据。 展开更多
关键词 knudsen 气体分离 表面特性 热驱流动 棘齿型微通道 DSMC方法 微机电系统(MEMS)
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四边形阵列的微通道型Knudsen泵内热驱流动的DSMC数值模拟优化 被引量:1
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作者 韩峰 王晓伟 +2 位作者 张文青 张世伟 张志军 《真空科学与技术学报》 EI CAS CSCD 北大核心 2023年第3期238-244,共7页
Knudsen泵是可应用于微机电系统(MEMS)的一种微型气体输送装置。本文提出一种带有不同温度四边形的微通道构型,通过直接模拟蒙特卡罗(DSMC)方法对该微通道内气体流动特性进行了数值模拟研究,并针对其气体泵送特性进行了优化研究,给出了... Knudsen泵是可应用于微机电系统(MEMS)的一种微型气体输送装置。本文提出一种带有不同温度四边形的微通道构型,通过直接模拟蒙特卡罗(DSMC)方法对该微通道内气体流动特性进行了数值模拟研究,并针对其气体泵送特性进行了优化研究,给出了泵送气体的最佳参数。研究发现,微通道内温差在75~1200 K范围内时,质量流量随着温差的升高几乎呈线性增大,且温差在1200 K时质量流量是75 K时的10倍。对于不同的Knudsen数,最大气体流速和质量流量均出现在Kn=0.3Knudsen泵的62倍。这些结论可为工业领域内各种微型气体泵送装置的实现和设计提供参考依据。 展开更多
关键词 knudsen 四边形阵列微通道 DSMC方法 微机电系统(MEMS) 参数优化
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考虑Knudsen扩散影响的水泥基材料湿扩散系数 被引量:5
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作者 陈德鹏 钱春香 《建筑材料学报》 EI CAS CSCD 北大核心 2009年第6期635-638,共4页
根据水泥基材料的多孔介质特点和内部孔隙尺寸分布特征,结合多孔介质中的湿传输机理,认为水泥基材料的湿传输研究必须考虑Knudsen扩散的影响.根据中、微孔体积的等效直径理论以及气体分子运动论相关原理,推导建立了Knudsen扩散影响系数... 根据水泥基材料的多孔介质特点和内部孔隙尺寸分布特征,结合多孔介质中的湿传输机理,认为水泥基材料的湿传输研究必须考虑Knudsen扩散的影响.根据中、微孔体积的等效直径理论以及气体分子运动论相关原理,推导建立了Knudsen扩散影响系数的理论计算公式,在此基础上,探讨了水泥基材料湿扩散系数的确定方法,并通过实际问题的分析进行了验证. 展开更多
关键词 水泥基材料 湿传输 knudsen扩散 湿扩散系数
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SO_2气体在微孔CaO脱硫剂颗粒内的Knudsen扩散 被引量:1
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作者 尚建宇 王松岭 王春波 《热能动力工程》 CAS CSCD 北大核心 2009年第3期382-385,共4页
从稀薄气体效应出发,通过对SO2气体分子在CaO脱硫剂颗粒内微尺度孔隙中气体动力学扩散机制的描述,对有效扩散系数进行了修正,建立了基于团聚体概念的Knud-sen扩散数学模型,利用误差函数进行求解和简化,得到其函数关系。模拟分析显示:SO... 从稀薄气体效应出发,通过对SO2气体分子在CaO脱硫剂颗粒内微尺度孔隙中气体动力学扩散机制的描述,对有效扩散系数进行了修正,建立了基于团聚体概念的Knud-sen扩散数学模型,利用误差函数进行求解和简化,得到其函数关系。模拟分析显示:SO2气体分子通过Knudsen扩散向颗粒一级气孔、二级气孔内渗透时,分形孔隙和较大的一级气孔孔隙率都能增大气体向内扩散的阻力,促使径向SO2浓度分布梯度增加。结果表明,分析气体在CaO颗粒内扩散时,忽略气固化学反应等因素而只考虑Knudsen扩散是可行的。 展开更多
关键词 脱硫剂 CAO 团聚体 knudsen扩散 SO2 扩散模型
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高温质谱 Knudsen 池进样装置的设计
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作者 李国勋 曹蓉江 樊启新 《稀有金属》 EI CAS CSCD 北大核心 1993年第2期81-84,共4页
结合 Atlas-CH_4 型质谱仪设计了用于高温质谱技术的 Knudsen 池进样装置。提出了设计原则、设计方案以及相应的理论计算。该装置具有四个试样池,池体可以旋转。采用电阻丝和电子轰击两种加热方式,最高温度可达2500K,适用于高熔点化合... 结合 Atlas-CH_4 型质谱仪设计了用于高温质谱技术的 Knudsen 池进样装置。提出了设计原则、设计方案以及相应的理论计算。该装置具有四个试样池,池体可以旋转。采用电阻丝和电子轰击两种加热方式,最高温度可达2500K,适用于高熔点化合物热力学性质的测定。 展开更多
关键词 质谱仪 knudsen 进样装置 设计
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矩形微通道Knudsen泵中的气体传输特性研究 被引量:2
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作者 王晓伟 张志军 +2 位作者 张文青 苏天一 张世伟 《真空与低温》 2020年第1期73-81,共9页
Knudsen泵是一种基于微尺度条件下的热蠕流效应诱导气体从低温侧向高温侧流动的微型泵。为探究气体种类和分子模型对气体在Knudsen泵通道中传输特性的影响,运用直接模拟蒙特卡罗(DSMC)方法,针对经典的矩形微通道开展了研究。文中分别考... Knudsen泵是一种基于微尺度条件下的热蠕流效应诱导气体从低温侧向高温侧流动的微型泵。为探究气体种类和分子模型对气体在Knudsen泵通道中传输特性的影响,运用直接模拟蒙特卡罗(DSMC)方法,针对经典的矩形微通道开展了研究。文中分别考虑了三种气体(Ar、N2和O2)和三种分子模型(HS、VHS和VSS)在不同工况压力下的变化情况。研究发现,不同种类气体和分子模型不会引起通道中宏观流场的明显变化。对于分子质量较轻的气体,其具有更强的热蠕流效应,且其最强热蠕流效应所对应的压力越大。对于分子模型,VHS模型的热蠕流效应最强,HS模型的热蠕流效应最弱。因此,相比于更能反映真实气体分子运动规律的VSS模型而言,当采用VHS模型时会高估泵的性能,反之,采用HS模型时会低估泵的性能。 展开更多
关键词 气体种类 分子模型 热蠕流 knudsen 矩形微通道 DSMC
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Rarefaction and Temperature Gradient Effect on the Performance of the Knudsen Pump 被引量:6
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作者 YE Jianjun YANG Jian +4 位作者 ZHENG Jinyang DING Xianting WONG Ieong LI Weizhong CHEN Cong 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2012年第4期745-752,共8页
The prediction of the multiscale flow in the Knudsen pump is important for understanding its pumping mechanism.However,there is little research on such interesting multiscale phenomenon in the Knudsen pumps.In this pa... The prediction of the multiscale flow in the Knudsen pump is important for understanding its pumping mechanism.However,there is little research on such interesting multiscale phenomenon in the Knudsen pumps.In this paper,a novel numerical analysis method combining the direct simulation Monte Carlo(DSMC) method with the smoothed particle hydrodynamics(SPH) method is presented for simulating the multiscale flow,which is often encountered in the application of the Knudsen pumps.Validity and accuracy of the new method are given by comparing its results with that of the previous research.Using the coupled multiscale approach,the rarefaction and the temperature drive are studied,which are two main factors on the performance of the Knudsen pumps.To investigate the effect of rarefaction on the performance of the Knudsen pump,various pump operation pressures are compared.The flow characteristics and pumping ability at different rarefaction are analyzed,and the phenomenon of the multiscale flow is also discussed.Several cases with different linear or nonlinear temperature gradients are set to investigate the effect of temperature gradient on the performance of the Knudsen pump.The flow characteristics of the Knudsen pump such as the velocity,pressure increase,and the mass flowrate are presented.A unique phenomenon,the reverse transpiration effect caused by the nonlinear temperature gradient is studied,and the reason of the significant pressure increase in the pump channel is also analyzed.Since the multiscale gas flow is widely encountered in the microflow systems,the above method and its results can also be greatly beneficial and provide significant insights for the design of the MEMS devices. 展开更多
关键词 thermal transpiration knudsen pump mass flowrate RAREFACTION temperature gradient-driven
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Correction of source-rock permeability measurements owing to slip flow and Knudsen diffusion: a method and its evaluation 被引量:2
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作者 Hui-Hai Liu Dan Georgi Jinhong Chen 《Petroleum Science》 SCIE CAS CSCD 2018年第1期116-125,共10页
Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sa... Source-rock permeability is a key parameter that controls the gas production rate from unconventional reservoirs. Measured source-rock permeability in the laboratory, however, is not an intrinsic property of a rock sample, but depends on pore pressure and temperature as a result of the relative importance of slip flow and diffusion in gas flow in lowpermeability media. To estimate the intrinsic permeability which is required to determine effective permeability values for the reservoir conditions, this study presents a simple approach to correct the laboratory permeability measurements based on the theory of gas flow in a micro/nano-tube that includes effects of viscous flow, slip flow and Knudsen diffusion under different pore pressure and temperature conditions. The approach has been verified using published shale laboratory data.The ''corrected''(or intrinsic) permeability is considerably smaller than the measured permeability. A larger measured permeability generally corresponds to a smaller relative difference between measured and corrected permeability values. A plot based on our approach is presented to describe the relationships between measured and corrected permeability for typical Gas Research Institute permeability test conditions. The developed approach also allows estimating the effective permeability in reservoir conditions from a laboratory permeability measurement. 展开更多
关键词 Shale gas PERMEABILITY knudsen diffusion Unconventional reservoir Source rock
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Knudsen隙透法测定有机物极微蒸气压数据的研究 被引量:1
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作者 衣守志 马沛生 阮永嗣 《吉林化工学院学报》 CAS 1993年第3期22-26,共5页
建立了一套极微蒸气压数据的测定装置,用正十六烷作为标准物对设备进行了校验。采用Knudsen称重隙透法测定了正十八烷、1—十八烯、邻苯二甲酸二乙酯、对苯二甲酸二甲酯、二异丙基萘、芘六种物质在298~373K范围内的极微蒸气压数据,并用... 建立了一套极微蒸气压数据的测定装置,用正十六烷作为标准物对设备进行了校验。采用Knudsen称重隙透法测定了正十八烷、1—十八烯、邻苯二甲酸二乙酯、对苯二甲酸二甲酯、二异丙基萘、芘六种物质在298~373K范围内的极微蒸气压数据,并用Antoine方程进行了关联。本文提供的绝大多数实验数据是首次发表的。 展开更多
关键词 蒸气压 测定 Kundsen隙透 有机物
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页岩气渗流机制数学表征及Knudsen扩散影响分析 被引量:2
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作者 刘骞 《重庆科技学院学报(自然科学版)》 CAS 2018年第2期35-38,共4页
基于双重介质,建立基质和裂缝的运动方程。考虑基质和裂缝的黏性流及Knudsen扩散作用,采用Langmuir等温吸附方程表征气体分子在基质孔隙的吸附与解吸附作用。同时,通过Knudsen扩散的质量流量公式,分析孔隙半径、压力和温度变化对质量流... 基于双重介质,建立基质和裂缝的运动方程。考虑基质和裂缝的黏性流及Knudsen扩散作用,采用Langmuir等温吸附方程表征气体分子在基质孔隙的吸附与解吸附作用。同时,通过Knudsen扩散的质量流量公式,分析孔隙半径、压力和温度变化对质量流量的影响。 展开更多
关键词 页岩气 渗流 knudsen扩散 双重介质
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SUPERSONIC DUSTY-GAS FLOWS WITH KNUDSEN EFFECT IN INTERPHASE MOMENTUM EXCHANGE
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作者 王柏懿 A.N.OSIPTSOV +1 位作者 L.A.EGOROVA V.I.SAKHAROV 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2004年第5期465-470,共6页
On the basis of the two-continuum model of dilute gas-solid suspensions,the dynamic behavior of inertial particles in supersonic dusty-gas flows past a blunt body is studied for moderate Reynolds numbers,when the Knud... On the basis of the two-continuum model of dilute gas-solid suspensions,the dynamic behavior of inertial particles in supersonic dusty-gas flows past a blunt body is studied for moderate Reynolds numbers,when the Knudsen effect in the interphase momentum exchange is significant. The limits of the inertial particle deposition regime in the space of governing parameters are found numerically under the assumption of the slip and free-molecule flow regimes around particles.As a model problem,the flow structure is obtained for a supersonic dusty-gas point-source flow colliding with a hypersonic flow of pure gas.The calculations performed using the full Lagrangian approach for the near-symmetry-axis region and the free-molecular flow regime around the particles reveal a multi-layer structure of the dispersed-phase density with a sharp accumulation of the particles in some thin regions between the bow and termination shock waves. 展开更多
关键词 gas-solid suspension supersonic flow knudsen effect particle inertia
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Development of a new correlation to calculate permeability for flows with high Knudsen number
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作者 Esmaeil Dehdashti 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第2期271-277,共7页
Flows with high Knudsen number play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow with high Knudsen number using modified lattice Boltzmann method (LB... Flows with high Knudsen number play a prominent role in many engineering applications. The present study is an effort toward the simulation of flow with high Knudsen number using modified lattice Boltzmann method (LBM) through a porous medium in a channel. The effect of collision between molecules and solid walls, which is required to accurately simulate transition flow regime, is taken into account using a modified relaxation time. Slip velocity on the wall, which is another significant difficulty in simulating transition flow regime, is captured using the slip reflection boundary condition (SRBC). The geometry of porous medium is considered as in-line and staggered. The results are in good agreement with previous works. A new correlation is obtained between permeability, Knudsen number and porosity for flows in transition flow regimes. 展开更多
关键词 flow in porous micro-channel lattice Boltzmann method high knudsen number PERMEABILITY
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A Diffusion Equation for Gas Permeation though an Inorganic Porous Membrane in the Knudsen Regime
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作者 Pei Huang Nanping Xu Jun Shi(Nanjing Institute of Chemical. Technology, Nanjing 210009, P.R.China) 《高校化学工程学报》 EI CAS CSCD 1994年第S1期111-114,共4页
ADiffusionEquationforGasPermeationthoughanInorganicPorousMembraneintheKnudsenRegimePeiHuang;NanpingXu;JunShi... ADiffusionEquationforGasPermeationthoughanInorganicPorousMembraneintheKnudsenRegimePeiHuang;NanpingXu;JunShi(NanjingInstitute... 展开更多
关键词 MEMBRANE EQUATION Gas INORGANIC knudsen Diffusion PERMEATION POROUS REGIME an
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Boosting Cu(In,Ga)Se_(2)Thin Film Growth in Low-Temperature Rapid-Deposition Processes:An Improved Design for the Single-Heating Knudsen Effusion Cell
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作者 Yunxiang Zhang Shuping Lin +5 位作者 Shiqing Cheng Zhichao He Zhaojing Hu Zhiqiang Zhou Wei Liu Yun Sun 《Engineering》 SCIE EI 2021年第4期534-541,共8页
The Knudsen effusion cell is often used to grow high-quality Cu(In,Ga)Se_(2)(CIGS)thin film in coevaporation processes.However,the traditional single-heating Knudsen effusion cell cannot deliver complete metal selenid... The Knudsen effusion cell is often used to grow high-quality Cu(In,Ga)Se_(2)(CIGS)thin film in coevaporation processes.However,the traditional single-heating Knudsen effusion cell cannot deliver complete metal selenides during the whole deposition process,particularly for a low-temperature deposition process,which is probably due to the condensation and droplet ejection at the nozzle of the crucible.In this study,thermodynamics analysis is conducted to decipher the reason for this phenomenon.Furthermore,a new single-heating Knudsen effusion is proposed to solve this difficult problem,which leads to an improvement in the quality of CIGS film and a relative increase in conversion efficiency of 29%at a growth rate of about 230 nmmin1,compared with the traditional efficiency in a lowtemperature rapid-deposition process. 展开更多
关键词 Cu(In Ga)Se_(2) knudsen effusion cell CONDENSATION Droplet ejection Low temperature
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考虑气体滑脱及Knudsen扩散的低渗致密砂岩微观流动模拟 被引量:4
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作者 曹廷宽 刘成川 +3 位作者 卜淘 段永刚 方全堂 孙连浦 《石油与天然气地质》 EI CAS CSCD 北大核心 2017年第6期1165-1171,共7页
低渗致密砂岩纳米-微米尺度孔喉发育,微观非均质性强,渗流机理复杂,现有物理实验方法难以准确评价。采用基于数字岩心理论的微观流动模拟方法来分析低渗致密砂岩中天然气的渗流规律。以川西地区沙溪庙组砂岩样品为基础,利用CT扫描建立... 低渗致密砂岩纳米-微米尺度孔喉发育,微观非均质性强,渗流机理复杂,现有物理实验方法难以准确评价。采用基于数字岩心理论的微观流动模拟方法来分析低渗致密砂岩中天然气的渗流规律。以川西地区沙溪庙组砂岩样品为基础,利用CT扫描建立目标岩样三维数字岩心,通过孔喉识别、形态简化及喉道调整,构建了包含不同孔喉分布的低渗致密砂岩三维孔隙模型;考虑天然气在纳米-微米孔喉中输运机制的复杂性,建立了耦合Darcy渗流、气体滑脱和Knudsen扩散的流动控制方程,并结合孔隙模型对其进行离散求解。开展流动模拟,评价不同孔隙压力下各输运机制对天然气产出运移的影响。结果表明:低渗致密砂岩中喉道越小、孔隙压力越低,气体流动非线性越强;在孔隙压力高于10 MPa范围,天然气在平均喉道半径大于0.1μm的砂岩孔隙空间中的流动基本满足Darcy渗流;而对于平均喉道半径小于0.1μm的致密砂岩,孔隙压力低于10 MPa后气体滑脱和Knudsen扩散是气体运移中重要机制,对天然气生产的影响不可忽略。 展开更多
关键词 CT扫描 Darcy渗流 Knudsn扩散 气体滑脱 三维孔隙模型 低渗致密砂岩 川西地区
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大Knudsen数下气溶胶表面性质和密度比对碰并率的影响
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作者 叶建 张连众 +1 位作者 黄建华 王浩 《南开大学学报(自然科学版)》 CAS CSCD 北大核心 2007年第3期1-3,共3页
大 Knudsen 数条件下,从气溶胶粒子的动力学参数入手,求得了全域 Péclet 数下的碰并率通量结果.讨论了表面性质对气溶胶粒子碰并率的影响,指出只要势力存在,在粒子半径空间总会存在一个 Brown 占优的区域.同时也讨论了密度比对气... 大 Knudsen 数条件下,从气溶胶粒子的动力学参数入手,求得了全域 Péclet 数下的碰并率通量结果.讨论了表面性质对气溶胶粒子碰并率的影响,指出只要势力存在,在粒子半径空间总会存在一个 Brown 占优的区域.同时也讨论了密度比对气溶胶粒子碰并率的影响,指出可以在碰并率极限处使用可加性假设,使用上下游的说法更加适合描述该情况下的碰并率. 展开更多
关键词 Knuden数 气溶胶 碰并率
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Overall Assessment of Heat Transfer for a Rarefied Flow in a Microchannel with Obstacles Using Lattice Boltzmann Method
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作者 Siham Hammid Khatir Naima +7 位作者 Omolayo M.Ikumapayi Cheikh Kezrane Abdelkrim Liazid Jihad Asad Mokdad Hayawi Rahman Farhan Lafta Rashid Naseer Ali Hussien Younes Menni 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第1期273-299,共27页
The objective of this investigation is to assess the effect of obstacles on numerical heat transfer and fluid flow momentum in a rectangular microchannel(MC).Two distinct configurations were studied:one without obstac... The objective of this investigation is to assess the effect of obstacles on numerical heat transfer and fluid flow momentum in a rectangular microchannel(MC).Two distinct configurations were studied:one without obstacles and the other with alternating obstacles placed on the upper and lower walls.The research utilized the thermal lattice Boltzmann method(LBM),which solves the energy and momentum equations of fluids with the BGK approximation,implemented in a Python coding environment.Temperature jump and slip velocity conditions were utilized in the simulation for the MC and extended to all obstacle boundaries.The study aims to analyze the rarefaction effect,with Knudsen numbers(Kn)of 0.012,0.02,and 0.05.The outcomes indicate that rarefaction has a significant impact on the velocity and temperature distribution.The presence of nine obstacles led to slower fluid movement inside the microchannel MC,resulting in faster cooling at the outlet.In MCs with obstacles,the rarefaction effect plays a crucial role in decreasing the Nusselt number(Nu)and skin friction coefficient(Cf).Furthermore,the study demonstrated that the obstacles played a crucial role in boosting fluid flow and heat transfer in the MC.The findings suggest that the examined configurations could have potential applications as cooling technologies in micro-electro-mechanical systems and microdevice applications. 展开更多
关键词 MICROFLUID rarefied flow LBM MICROCHANNEL knudsen number numerical simulation
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考虑虚拟边界与应力耦合的页岩渗透率模型
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作者 叶平平 李波波 +3 位作者 吴学海 宋浩晟 段淑蕾 成巧耘 《大庆石油地质与开发》 CAS 北大核心 2024年第5期166-174,共9页
为探讨页岩气开采过程中页岩渗透率的变化情况,基于毛细管层序模型,采用虚拟边界与应力耦合相结合的方法,按照一定权重系数将应力推导黏性流动和克努森扩散相加,建立了页岩纳米孔体相气体传输模型。结果表明:新建渗透率模型计算曲线与... 为探讨页岩气开采过程中页岩渗透率的变化情况,基于毛细管层序模型,采用虚拟边界与应力耦合相结合的方法,按照一定权重系数将应力推导黏性流动和克努森扩散相加,建立了页岩纳米孔体相气体传输模型。结果表明:新建渗透率模型计算曲线与试验实测值吻合较好,可以较好揭示页岩纳米孔体相气体流动情况;与Lu模型和S&D模型相比,新建模型考虑虚拟边界与应力的耦合,表观渗透率模型计算曲线与试验结果更为吻合,且能很好地反映实测值与孔隙压力所呈现的变化规律,具有较好的优越性;页岩力学参数(弹性模量、泊松比)、Langmuir应变常数及裂隙压缩系数对页岩渗透率起抑制作用,主要表现为其值越大,页岩渗透率越小;初始渗透率对页岩渗透率起促进作用,表现为其值越大,页岩渗透率越大。研究成果可为页岩气开发提供理论支撑。 展开更多
关键词 页岩气开采 渗透率 虚拟边界 层序模型 应力/应变 黏性流动 克努森扩散
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Effects of Compressibility and Knudsen Number on the Aero Optics in Hypersonic Flow Fields 被引量:4
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作者 任维 刘洪 《Journal of Shanghai Jiaotong university(Science)》 EI 2016年第3期270-279,共10页
Tsien summarized the similarity in hypersonic flows, and related Knudsen number to Mach number and Reynolds number. Recently, a path-based problem, aero-optical effect, arises in hypersonic flows, and it concerns abou... Tsien summarized the similarity in hypersonic flows, and related Knudsen number to Mach number and Reynolds number. Recently, a path-based problem, aero-optical effect, arises in hypersonic flows, and it concerns about the compressibility and the Knudsen number of the gas flows, which differs from the Tsien's focus to some extent. In this paper, the similarity of hypersonic aero optics is theoretically studied, and both flow fields and induced aero-optical effect after flows pass through a cylinder are predicted by a well-accepted particle-based method, direct simulation Monte-Carlo(DSMC) method. The results show that the optical distortions are inversely proportional to the Knudsen number, while the compressibility plays an important role in the optical degradations.Hence, it is confirmed that the effects of Mach number and Knudsen number on the aero-optical effect induced by hypersonic flows are of great significance. Besides, since the Knudsen number is defined straightforwardly based on the optically active region, the physics is clearer than any other similarity criteria. 展开更多
关键词 aero optics hypersonic flows similarity knudsen number
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多级努森真空泵能效分析
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作者 柯杰坤 蒙仕达 +1 位作者 苏宣合 卢苇 《真空科学与技术学报》 CAS CSCD 北大核心 2024年第1期42-48,共7页
基于热流逸效应工作的努森真空泵相较于传统真空泵,因具有无运动部件且结构简单的优点而倍受关注,其应用通常采用多级串联结构。文章以努森真空泵能耗和效率模型为基础,着重考虑级数与热量传递和压力分配的关系,建立了多级努森真空泵气... 基于热流逸效应工作的努森真空泵相较于传统真空泵,因具有无运动部件且结构简单的优点而倍受关注,其应用通常采用多级串联结构。文章以努森真空泵能耗和效率模型为基础,着重考虑级数与热量传递和压力分配的关系,建立了多级努森真空泵气体工质流态处于过渡流时的能耗(热流比)与运行效率模型,进而研究了影响热流比及运行效率与级数、努森数、压比、温差等参数的关系。结果表明,努森数从0.2增至8,对应的最优级数从118级减少至15级;压比从2增至100,对应的最优级数从12级增加至77级;温差从50 K增至350 K,对应的最优级数从68级减少至15级。努森数(温差)越大、或压比越小,热流比就越低(运行效率就越高)且对应的最优级数就越小,所需的最小级数也越少。若从能效优化的角度来设计多级努森真空泵,需综合考虑努森数、压比和温差的影响,确定最优级数范围。 展开更多
关键词 热流逸效应 多级结构 努森真空泵 热流比 运行效率
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