Deposition Velocity onto an Inverted Flat Surface in a Laminar Parallel Flow

Wafers and photomasks in the cleanroom are exposed to airflows not only vertical but also parallel to the surfaces. In this study, Gaussian Diffusion Sphere Model (GDSM) was adjusted to predict deposition velocity onto an inverted flat surface in a laminar parallel flow by considering Brownian diffusion and gravitational settling of aerosol particles. The GDSM was validated by comparing with the simulation of solving flow and aerosol-concentration fields for an inverted flat surface and also with the mass transfer correlation for a finite flat surface of circular or rectangular areal shape. The GDSM was proven to correctly predict the deposition velocities onto the inverted flat surfaces, by taking one hour with a 2.66-GHz-CPU personal computer to obtain deposition velocities for 20 particle sizes, which is a very much shorter time compared with the time for simulating the flow and aerosol-concentration fields. Deposition velocities onto the inverted 45-cm-wafer and 15.2-cm-photomask in parallel airflows were predicted using the GDSM, for the particle size ranging from 0.003 to 1.5 μ m and the airflow velocity varying from 5 to 500 cm/s. The deposition velocity decreased with increasing particle size, with a steep declination especially for particles larger than approximately 0.1 μ m. From the qualitative comparison of the deposition velocities onto the inverted square flat surfaces, representing the photomasks with different orientations in the parallel flow, it was suggested to transport the EUVL photomask with its side facing the airflow rather than with its corner confronting the airflow, in order to minimize particulate contamination.     

Deposition of Particles by a Confined Impinging Jet onto a Flat Surface at Re = 10 4

An axisymmetric turbulent air jet flow (with vertical and downward orientation) laden with fluorescent solid particles was impinged normally onto a flat surface. The particle deposition efficiency and distribution on the flat surface were measured experimentally using fluorometry and imaging techniques. The fluorescent particles (5.0 μm diameter) were dispersed by a nebulizer and injected in a stream of compressed air, resulting in a steady flow (Q = 111 L/min). A round nozzle was used to generate a jet characterized by a Reynolds number of Re = 10 ⁴ , based on the nozzle diameter (D = 15.0 mm) and nozzle exit velocity (u = 10.5 m/s). Three dimensionless distances from the nozzle's exit to the impaction surface, L/D = 2, 4, and 6, were investigated. It was observed that although having similar total deposition efficiencies (16.5–17.8%), shorter nozzle to surface distances (L/D = 2 and 4) show a more pronounced ring-like radial deposition pattern around the stagnation point. These shorter distances also exhibit significantly lower particle deposition near the stagnation point when compared to the longer distance (L/D = 6). Indeed, in moving through L/D = 2, 4, and 6, peak deposition density values of 254, 347, and 685 particles/mm ² shift through radii of 2.1 D, 0.8 D, and 0.1 D, respectively. In addition to the experiments, numerical simulation was also performed, which showed that the particle deposition was dominated by a turbulent dispersion mechanism for L/D = 2, with inertial impaction becoming more important for the L/D = 4 and 6 cases.     

Airflow and Deposition of Nano-Particles in a Human Nasal Cavity

A 3D computational model was developed to study the flow and the transport and deposition of nano-size particle in a realistic human nasal passage. The nasal cavity was constructed from a series of MRI images of coronal sections of a nose of a live human subject. For several breathing rates associated with low or moderate activities, the steady state flows in the nasal passage were simulated numerically. The airflow simulation results were compared with the available experimental data for the nasal passage. Despite the anatomical differences of the human subjects used in the experiments and computer model, the simulation results were in qualitative agreement with the experimental data.

Deposition and transport of ultrafine particles (1 to 100 nm) in the nasal cavity for different breathing rates were also simulated using an Eulerian-Lagrangian approach. The simulation results for the nasal capture efficiency were found to be in reasonable agreement with the available experimental data for a number of human subjects given typical anatomical differences. The computational results for the nasal capture efficiency for nano-particles and various breathing rates in the laminar regime were found to correlate well with the ratio of particle diffusivity to the breathing rate especially for the particles smaller than 20 nm. Based on the simulated results, a semi-empirical equation for the capture efficiency of the nasal passage for nano-size particles was fitted in terms of Peclet number.     

三价铬电解液镀铬沉积速度的影响因素研究

对三价铬电解液镀铬的沉积速度进行了实验研究。对施镀过程中沉积速度的影响因素电镀时间、电流密度、温度做了详细的实验测试,实验结果表明,为了获得较高的沉积速度,施镀过程中应该控制电镀时间为2 m in,电流密度为6 A/dm2,温度为45℃,pH为3.5。     

Developing an Empirical Equation for Modeling Particle Deposition Velocity onto Inclined Surfaces in Indoor Environments

For the purpose of modeling indoor particle dispersion with an Eulerian drift flux model or analyzing indoor particle deposition onto various surfaces accurately, it may take considerable time to calculate the deposition velocity for each surface as numerical integration or calculation is usually needed. In this article, a modified three-layer model is presented to calculate indoor particle deposition velocities for surfaces with different inclinations and for different friction velocities. Then, 1020 cases, covering the common indoor scenarios, were modeled to obtain a database of indoor particle deposition velocities. Based on the results of the 1020 cases, an empirical equation was generated to determine indoor particle deposition velocities. The empirical equation was divided into four parts, named the Fine zone, Coarse zone, Zero zone, and Transition zone. In the Fine zone, the friction velocity decides the particle deposition velocity, while in the Coarse zone, the inclination angle of the surface is the decisive parameter for the deposition velocity. The results show that the average error of the empirical equation to the database was 1.53%, 1.50%, and 21.93% in the Fine zone, Coarse zone, and Transition zone, respectively. The deposition velocities in the Zero zone can all be deemed as zero. Empirical equation predictions agree well with experimental data for a spherical chamber (Cheng 1997 Cheng, Y. S. 1997. Wall Deposition of Radon Progeny and Particles in a Spherical Chamber. Aerosol Sci. Technol., 27: 131–146. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). The empirical equation generated in this study is therefore applicable for easily calculating the boundary conditions for Eulerian drift flux model or analyzing indoor particle deposition onto smooth surfaces with varying inclinations with reasonable accuracy.

Copyright 2012 American Association for Aerosol Research     

平板膜式氧合器中氧传质过程的数学模型

本文对平板膜式氧合器中的传递过程进行了研究,提出了伴有瞬间可逆氧合反应时卡森流体的对流传质模型,并用有限差分方法获得了模型的数值解.当将卡森流体简化为牛顿流体时,其物理吸收的计算结果与文献值完全一致.本文采用猪血进行了氧合实验.实验数据与理论计算的结果相吻合.当血液按牛顿流体和卡森流体处理时,发现两者的计算结果相差甚微,因而认为,在氧合器的研制中可将血液作为牛顿流体处理.     

Eulerian Model for Prediction of Particle Transport and Deposition in Turbulent Duct Flows with Thermophoresis

The Reynolds-averaged equations for turbulent particle population/transport in an Eulerian framework must be closed by specifying models for several terms: a turbophoretic force; a turbulent thermophoretic force; and a turbulent particle-diffusion term. In this article, new models are proposed for the turbophoretic term, as a particle-size dependent extrapolation of the corresponding turbulent fluid-velocity correlation, and for the turbulent thermophoretic term as an eddy-viscosity-scaled multiple of the corresponding mean thermophoretic term, appropriate for small low-inertia particles with τ⁺_p < 10. When the turbophoresis model is incorporated in a system of equations that describes particle motion within the surrounding fluid, it predicts particle deposition velocities that are in good agreement with experimental data over a range of particle sizes. When this equation system is included in a computational model to predict particle transport in turbulent pipe flows, the efficiency of particle deposition in pipes with upstream heating and downstream cooling is found to be in fair agreement with experimental measurements at two different Reynolds numbers, and over a range of particle sizes and temperature differences.

Copyright 2015 American Association for Aerosol Research     

高气速下鼓泡塔中气含率分布的测定

在内径476 mm的鼓泡塔内用压差法测定全塔平均气含率与表观气速的关系,进一步利用响应特性良好的双电导探针,考察了不同气速下局部气含率的分布规律。实验结果表明,利用探针法计算得到的全塔平均气含率值与压差法测定值平均误差仅为4.5%,表明探针法测量局部气含率的可靠性良好。实验还表明在高气速下,除分布板影响区外,局部气含率均类似抛物线型分布;随着气速增加,气含率分布趋于陡峭。以实验为依据,拟合了不同气速下(0.05~1.0 m/s)鼓泡塔中局部气含率的关联式,认为塔内局部气含率与径向位置、表观气速和塔径等因素有关。     

隧道窑冷却带喷嘴喷射速度对窑内气体流动的影响

利用 CFD 软件模拟了隧道窑急冷带内喷嘴喷射速度的改变对窑内气体流动的影响,分析了窑内气体的速度和温度分布情况.在热源项相同和单个喷嘴气体流量不变时,减小喷嘴半径增加喷嘴的喷射速度,窑内气体流速和温度都增加,从而有利于窑内制品的冷却.喷射速度增加到一定值后,窑内气体温度趋于稳定,喷射速度有一上限.     

马来酸对次磷酸钠化学镀铜沉积行为的影响

研究了以次磷酸钠为还原剂,柠檬酸钠为配位剂的化学镀铜体系中,添加剂马来酸对镀层成分、结构、形貌以及对次磷酸钠阳极氧化和铜离子阴极还原的影响.结果表明:加入马来酸后体系仍能保持较高镀速,而镀层颗粒大小逐渐变得均匀,外观颜色也由暗棕色逐渐变为铜色.化学镀铜层为面心立方结构,没有出现Cu-Ni合金晶面衍射峰.     

脉冲式密相气力输送水平管中的料栓行为

探讨了聚丙烯颗粒在脉冲式密相气力输送水平管中的料栓行为. 结果表明在一定操作气速下,料栓的长短变化有规律,料栓的运动速度随其长度而变;栓长为1 m左右的聚丙烯颗粒由栓状流向沙丘流型转变的料气速度之比为0.7~0.8,出现在操作气速5 m/s左右;单个料栓的压力梯度与其长度有关,沿单个料栓的压力梯度和截面固含量随气速而变;料栓压降与操作气速无关.     

Effect of Airflow Direction and Velocity on Smoldering Waves in Combustible Porous Layers

The mechanisms of propagation of smoldering waves in porous layers of pine sawdust were studied experimentally for cocurrent and opposed airflows in closed (with one open butt–end) and semiclosed (with a flat free surface) systems. We investigated the shape of the smoldering front and the effects of the airflow direction and velocity, combustible-layer porosity, and the dispersity of the sawdust layer on the smoldering wave velocity. Maximum temperature in the smoldering wave is established. In a closed system with airflow velocity higher than 5–7 cm/sec, the smoldering rate is an order of magnitude higher in a cocurrent flow than in an opposed flow. For cocurrent flow, the velocity of a smoldering wave is two orders of magnitude higher in a closed system than in a semiclosed system. The experimental dependences are explained. Key words: smoldering, wave processes, porosity.     

Investigation of Apatite Deposition onto Charged Surfaces in Aqueous Solutions Using a Quartz-Crystal Microbalance

Hydroxyapatite (HAp) deposition onto positively charged surfaces (i.e., self-assembled monolayers (SAMs) terminated with NH₂ head groups) and negatively charged surfaces (i.e., OH-SAMs (weak) and COOH-SAMs (strong)) soaked at 50°C in aqueous supersaturated solutions (1.5 SBF, pH 7.0–7.6; SBF = simulated body fluid) was investigated using a quartz-crystal microbalance. The results revealed that the solution conditions greatly influenced the formation of HAp on the charged surfaces. In a stable supersaturated solution of simulated body fluid (1.5 SBF, pH <7.4), more strongly negative surfaces had a more powerful induction capability for the heterogeneous nucleation of HAp (COOH > OH), whereas nucleation was obviously prohibited on a positive surface (NH₂-SAM). On the other hand, after the calcium phosphate particles had nucleated homogeneously in an unstable soaking solution (1.5 SBF, pH ≧7.4), adhesion of the HAp microparticles to the NH₂-SAM was observed. A two-step interaction is conceivable to describe the formation of HAp on the positive NH₂-SAM: At the first stage, electrostatic interaction dominates the adhesion of HAp microparticles; at the second stage, hydrogen bonds possibly form between the HAp microparticles and the amino head groups of the NH₂-SAM, for a firm bonding with the substrate, and the microparticles grow progressively into a thin film. The electrophoretic behaviors of the HAp microparticles confirmed this hypothesis.     

平板型光反应器光催化降解刚果红试验研究

利用自制的平板型光催化反应器,采用草酸铁/过氧化氢为光催化剂,考察了双氧水浓度、流量等因素对刚果红降解效果的影响.实验结果表明,溶液呈酸性有利于降解反应进行,但是和双氧水的投入量一样,存在最佳值问题,铁离子浓度增加和流量变大都有利于染料的降解.     

低密度循环流化床局部颗粒速度的轴径向分布的研究

在高8m,内径186mm的循环流化床中,利用光纤激光多普勒测速仪测量了FCC颗粒的局部速度沿轴径向的分布。实验结果表明:局部颗粒速度沿径向分布是不均匀的,床中心区域分布比较平坦,近壁环形区域分布较陡,颗粒沿轴向运动有较长的加速段。由实验数据回归得到预测低密度循环流化床局部颗粒速度的经验关联式。     

冲刷速度和温度对低碳钢在海水中冲蚀行为的影响

采用失重法研究了冲刷速度和温度对低碳钢在海水中冲刷腐蚀速率的影响,结合对试样表面腐蚀形貌的观察,对低碳钢在海水中冲蚀行为及机理进行了分析探讨。     

Deposition of a thin film of carbon nanotubes onto a glassy carbon electrode by electropolymerization

A novel and easy route for the deposition of a thin film of carbon nanotubes onto an electrode surface by electropolymerization is described. Multi-wall carbon nanotubes (MWNTs) were “dissolved” in aqueous alizarin red S (ARS, 3,4-dihydroxy-9,10-dioxo-2-anthracenesulfonic acid, sodium salt) solution, and a very stable and well-distributed aqueous MWNTs–ARS solution was obtained. A thin film of MWNTs–ARS was successfully deposited onto the electrode surface by an in situ electropolymerization in aqueous MWNTs–ARS solution. The MWNTs–ARS thin film was characterized by scanning electron microscopy, Raman spectroscopy, UV–Vis spectroscopy and electrochemical techniques.