International journal of micro-nano scale transport最新文献

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Blood flow in non-circular microchannel under pulsating condition 脉动条件下非圆形微通道内的血流

International journal of micro-nano scale transport

Pub Date : 2013-03-01 DOI: 10.1260/1759-3093.4.1-2.33

Nishant Kumar, A. Prabhakar, Mukul D. Tikekar, S. Singh, A. Agrawal

With the advent of point-of-care diagnostics systems, investigation into properties of blood at micron scales is gaining fundamental importance. Past research has shown that blood displays significantly different properties at small scales than at conventional scales. This study investigates properties of blood flow in small non-circular passages (hydraulic diameter: 95-960 μm) under pulsatile condition. The observations are compared with flow of water under otherwise similar conditions. Prominent observation includes a more stable response to abrupt mass flow rate fluctuations as compared to water, which is attributed to the presence of deformable cells in blood. The study also reveals that, the pressure drop for blood flow with pulsations is less than for steady condition with the difference increasing with a reduction in microchannel size and flow rate. Such a comparative study facilitates development of models for blood flow at micro-scales, and will eventually aid in the design of future micro-Total ...

随着即时诊断系统的出现，在微米尺度上对血液特性的研究变得越来越重要。过去的研究表明，血液在小尺度上与在常规尺度上表现出明显不同的特性。本文研究了脉动条件下非圆形小通道(液压直径:95 ~ 960 μm)内的血流特性。将观测结果与其他类似条件下的水流进行比较。突出的观察结果包括，与水相比，它对质量流速突然波动的反应更稳定，这是由于血液中存在可变形细胞。研究还表明，脉动血流时的压降小于稳态血流时的压降，且随微通道尺寸和流速的减小而增大。这样的比较研究促进了微观尺度血流模型的发展，并最终有助于未来微型total…

引用次数: 6

Investigation of the effect of fluid slip on heat transfer in the thin-film region in a micro-channel 流体滑移对微通道薄膜区传热影响的研究

International journal of micro-nano scale transport

Pub Date : 2012-09-01 DOI: 10.1260/1759-3093.3.3-4.103

R. Gorla, D.G.R. Sharma

A theoretical study was undertaken to check the influence of interfacial slip on evaporation of a thin liquid film in a microfluidic channel. The disjoining pressure and the capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted. The evaporating thin film region is an extended meniscus beyond the apparent contact line at a liquid/solid interface. Thin film evaporation plays a key role in a highly efficient heat pipe. Slip length was found to affect the heat transfer in the microchannel by altering the thin film geometry.

对微流控通道中界面滑移对液体薄膜蒸发的影响进行了理论研究。采用分离压力和毛细管力驱动薄膜区液气界面处的液体流动。蒸发薄膜区域是在液/固界面的视接触线以外的一个延长的半月板。薄膜蒸发在高效热管中起着关键作用。发现滑移长度通过改变薄膜的几何形状来影响微通道内的传热。

引用次数: 0

Decreasing of quantity of radiation defects in an implanted-junction rectifiers by using overlayers 利用复盖层减少植入结整流器辐射缺陷的数量

International journal of micro-nano scale transport

Pub Date : 2012-09-01 DOI: 10.1260/1759-3093.3.3-4.119

E. Pankratov, E. Bulaeva

We introduce an approach to decrease quantity of radiation defects in area of implanted-heterojunction rectifier. The approach based on implantation of ions of dopant in a homogenous sample, overgrowth of the damaged area and annealing of radiation defects. In this situation under spatial conditions one can obtain decreasing of quantity of radiation defects.

介绍了一种减小异质结整流器面积辐射缺陷数量的方法。该方法基于均匀样品中掺杂离子的注入、损伤区域的过度生长和辐射缺陷的退火。在这种情况下，在空间条件下，可以得到辐射缺陷数量的减少。

引用次数: 33

Temperature dependence of free-molecular gaseous heat flow in unsealed system open to surrounding ambient 对周围环境开放的非密封系统中自由分子气体热流的温度依赖性

International journal of micro-nano scale transport

Pub Date : 2012-09-01 DOI: 10.1260/1759-3093.3.3-4.113

A. Pandhari, D. Hasselman

Equipment designed for manufacturing or testing of materials at elevated temperatures is often open to and at the pressure of the surrounding ambient. Since, it is an open system, with an increase in temperature the gas phase is expected to expand. This causes reduction in the density of the gas phase within the components or samples contained within the equipment. This reduction in density is linearly proportional to an increase in the temperature. As a consequence, because of its direct dependence on gas density, the rate of gaseous heat flow in the free-molecular regime within these components or samples should exhibit a corresponding decrease with increasing temperature as well. An analysis of this effect conducted by incorporating the effect of temperature on density at constant pressure in the original Knudsen-Kennard formulation, showed that the rate of gaseous heat transfer in the free-molecular regime in an open system at constant pressure is expected to exhibit a reciprocal square root dependenc...

设计用于在高温下制造或测试材料的设备通常对周围环境的压力是开放的。由于它是一个开放系统，随着温度的升高，气相预计会膨胀。这会导致设备中包含的组件或样品内的气相密度降低。密度的降低与温度的升高成线性比例。因此，由于其直接依赖于气体密度，这些组分或样品中自由分子状态下的气体热流速率也应随着温度的升高而相应降低。通过在原来的Knudsen-Kennard公式中加入恒压下温度对密度的影响，对这种效应进行了分析，结果表明，在恒压下，开放系统中自由分子状态下的气体传热速率预计会呈现出倒数的平方根依赖关系。

引用次数: 0

Simulation of droplet impact on super hydrophobic surface 液滴撞击超疏水表面的模拟

International journal of micro-nano scale transport

Pub Date : 2012-09-01 DOI: 10.1260/1759-3093.3.3-4.131

Douglas F. Johnson, Sarit K. Das

Super hydrophobic surfaces find uses in many applications; therefore proper design of super hydrophobic surfaces is very crucial. A lot of work has already been done for static droplets and super hydrophobic surface interactions. There have also been some significant experiments carried out for dynamic droplet impact on super hydrophobic surfaces. The present work focuses on the super hydrophobic surface under dynamic conditions, with the study predominantly carried out through numerical simulation. Various parameters during impact and time variance after impact (typically up to 10 μs) were considered. The transition from water hammer pressure (order of ρCV) to flow pressure (order of 1/2 ρV2) is taken as the main parameter of analysis. During water hammer pressure domain, a strong tendency to cause wetting (Wenzel state) is seen. During flow pressure domain, wetting tendency is significantly reduced (Cassie-Baxter state). These states and the transition from one to the other are very crucial to the desig...

超疏水表面在许多应用中都有应用;因此，超疏水表面的合理设计至关重要。对于静态液滴和超疏水表面的相互作用已经做了大量的研究。对于液滴在超疏水表面上的动态撞击也进行了一些有意义的实验。目前的工作主要集中在动态条件下的超疏水表面，主要通过数值模拟进行研究。考虑了冲击过程中的各种参数和冲击后的时间变化(通常为10 μs)。以水锤压力(ρCV阶数)到流动压力(1/2 ρV2阶数)的过渡作为分析的主要参数。在水锤压力域中，有强烈的润湿倾向(温泽尔态)。在流动压力域中，润湿倾向显著降低(Cassie-Baxter状态)。这些状态以及从一种状态到另一种状态的转换对设计来说非常关键……

引用次数: 0

Fluctuating Hydrodynamics Approach for the Simulation of Nanoparticle Brownian Motion in a Newtonian Fluid. 牛顿流体中纳米粒子布朗运动模拟的波动流体力学方法。

International journal of micro-nano scale transport

Pub Date : 2012-06-01 DOI: 10.1260/1759-3093.3.1-2.13

B Uma, P S Ayyaswamy, R Radhakrishnan, D M Eckmann

The Brownian motion of a nanoparticle in an incompressible Newtonian fluid (quiescent or fully developed Poiseuille flow) has been investigated with an arbitrary Lagrangian-Eulerian based finite element method. Results for the motion in a compressible fluid medium are estimated. Thermal fluctuations from the fluid are implemented using a fluctuating hydrodynamics approach. The instantaneous flow around the particle and the particle motion are fully resolved. Carriers of two different sizes with three different densities have been investigated (nearly neutrally buoyant). The numerical results show that (a) the calculated temperature of the nearly neutrally buoyant Brownian particle in a quiescent fluid satisfies the equipartition theorem; (b) the translational and rotational decay of the velocity autocorrelation functions result in algebraic tails, over long time; (c) the translational and rotational mean square displacements of the particle obeys Stokes-Einstein and Stokes-Einstein-Debye relations, respectively. Larger the particle, longer the time taken to attain this limit; and (d) the parallel and perpendicular diffusivities of the particle closer to the wall are consistent with the analytical results, where available.

采用基于任意拉格朗日-欧拉的有限元方法研究了纳米粒子在不可压缩牛顿流体(静止或完全发育的泊泽维尔流)中的布朗运动。估计了在可压缩流体介质中运动的结果。流体的热波动采用波动流体力学方法来实现。粒子周围的瞬时流动和粒子运动被完全分解。研究了两种不同尺寸、三种不同密度的载体(几乎是中性浮力)。数值结果表明:(a)静态流体中近似中性浮力布朗粒子的温度满足均分定理;(b)速度自相关函数的平移和旋转衰减导致长时间的代数尾;(c)粒子的平动和旋转均方位移分别服从Stokes-Einstein和Stokes-Einstein- debye关系。粒子越大，达到这个极限所需的时间就越长;(d)靠近壁面的粒子的平行和垂直扩散系数与分析结果一致(如果有的话)。

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引用次数: 2

Performance of a Conceptual Counter-flow MCHE operated on CuO-Water Nanofluid: Influence of Geometry 概念逆流MCHE在CuO-Water纳米流体上的性能:几何形状的影响

International journal of micro-nano scale transport

Pub Date : 2012-06-01 DOI: 10.1260/1759-3093.3.1-2.1

Avdhesh Sharma

Microchannel heat exchangers (MCHE) can be designed with different channel geometry such as circular, triangular, rectangular, square, trapezoidal and hexagonal. In this article, the influence of channel geometry on thermal, hydraulic and overall performance of counter flow MCHE operated on CuO-water nanofluid flow has been highlighted. Herein, Nusselt and Poiseuille number for different channel shapes and thermo-physical properties of CuO-water nanofluid (viz., thermal conductivity, viscosity…) have been designed either empirically or adopted from literature. Results of pumping power with trapezoidal geometry MCHE is found to be highly sensitive with nanofluid flow. Rectangular shape counter flow MCHE gives highest thermal effectiveness, while iso-triangular geometry gives best overall performance by converting the pressure energy into thermal energy.

微通道换热器(MCHE)可以设计成不同的通道几何形状，如圆形、三角形、矩形、正方形、梯形和六边形。本文重点研究了沟道几何形状对逆流动MCHE热工、水力和综合性能的影响。本文设计了不同通道形状和纳米流体热物理性质(即导热系数、粘度等)的Nusselt和Poiseuille数。结果表明，梯形泵浦功率对纳米流体流动非常敏感。矩形逆流MCHE具有最高的热效率，而等三角形几何形状通过将压力能转换为热能而具有最佳的整体性能。

引用次数: 0

Assessment of Aviation Turbine Fuel-TiO2 Nanofluid for Heat Transfer Augmentation in Rocket Engines 航空涡轮燃料- tio2纳米流体对火箭发动机增热性能的评价

International journal of micro-nano scale transport

Pub Date : 2012-06-01 DOI: 10.1260/1759-3093.3.1-2.35

Sandipkumar Sonawane, U. Bhandarkar, B. Puranik, Sanjay Kumar

Nanofluids are suspensions of high thermal conductivity nanoparticles in a base fluid, and offer potential to enhance the thermal conductivity and heat transfer performance of the base fluid. The present work measures the thermo-physical properties, heat transfer performance and pressure loss characteristics of Aviation Turbine Fuel (ATF)-titanium oxide (TiO2) nanofluid. The experimental results show that the enhancement in the thermal conductivity is approximately 15% at a particle volume concentration of 0.3%, whereas the viscosity of the nanofluid increases upto 35% at the same particle volume concentration. Comparing the heat transfer coefficients with those of pure ATF at the same pressure drop, a maximum enhancement of 18% is observed at 0.3% particle volume concentration.

纳米流体是基液中高导热纳米颗粒的悬浮液，具有增强基液导热性和传热性能的潜力。本文测量了航空涡轮燃料(ATF)-氧化钛(TiO2)纳米流体的热物理性质、传热性能和压力损失特性。实验结果表明，当颗粒体积浓度为0.3%时，纳米流体的导热系数提高了约15%，而在相同颗粒体积浓度下，纳米流体的粘度提高了35%。在相同压降下，与纯ATF相比，当颗粒体积浓度为0.3%时，传热系数最大提高了18%。

引用次数: 1

Bioseparation in a Microfluidic Channel Using Magnetic Field Flow Fractionation 利用磁场流分馏的微流控通道生物分离

International journal of micro-nano scale transport

Pub Date : 2012-06-01 DOI: 10.1260/1759-3093.3.1-2.21

N. Modak, A. Pal, A. Datta, R. Ganguly

Magnetophoretic field flow fractionation (FFF) is a promising technique for bioseparation in microfluidic channels for micro-total analysis systems (μ-TAS) applications. A numerical study of FFF of magnetic microspheres of two different sizes in a micro-channel under a transverse magnetic field is studied. Due to the difference in the particle magnetophoretic mobility, particles develop different transverse velocities leading to their separation through two different outlets of the microchannel. Capture efficiency and separation index for the particles are computed at the two outlets, and their variations under different parametric conditions, viz., particle size and susceptibility, magnetic dipole strengths and positions, fluid viscosity and flow velocity, are characterized. Parametric studies show that the capture efficiency and separation index figures are high within a very narrow zone of operating conditions. Beyond this regime, the particles are either trapped on the wall before or after their desig...

磁电泳场流分馏(FFF)是一种很有前途的微流体通道生物分离技术，可用于微总量分析系统(μ-TAS)。研究了两种不同尺寸的磁性微球在横向磁场作用下在微通道中的FFF。由于颗粒磁泳迁移率的不同，颗粒产生不同的横向速度，导致它们通过微通道的两个不同出口分离。计算了颗粒在两个出口的捕获效率和分离指数，并对其在不同参数条件下的变化进行了表征，即颗粒大小和磁化率、磁偶极子强度和位置、流体粘度和流速。参数研究表明，在很窄的操作条件范围内，捕获效率和分离指数数字很高。超出这个范围，粒子要么在设计之前被困在壁上，要么在设计之后被困在壁上。

引用次数: 2

Experimental and Numerical Investigation of Forced Convection Heat Transfer in an Optimized Microchannel Heat Sink 优化微通道散热器强制对流换热的实验与数值研究

International journal of micro-nano scale transport

Pub Date : 2012-06-01 DOI: 10.1260/1759-3093.3.1-2.69

V. Swami, D. Kamble, Dr. B. S. Gawali

In this study, the experimental and numerical investigation of forced convective heat transfer in an optimized rectangular micro-channel heat sink (MCHS) is analyzed using water as the working fluid. The optimization of MCHS has carried out by using CVM (Constant Volume Method) and VVM (Variable Volume Method). From the optimization, it is clear that aspect ratio three which gives the better heat transfer coefficient and lower pressure drop values as comparing with adjacent aspect ratios. A numerical investigation of MCHS based on the finite volume method. The numerical results are validated by comparing the predictions with analytical solutions and experimental data. High heat flux and high coefficient of heat transfer obtained by reducing the core volume of the channel and changing operating conditions. The Optimized micro-channels geometry has a width of 700 μm and a depth of 2100 μm, and is separated by a 350 μm wall. The microchannels are made on cooper plate by using a wire Electro Discharge Machini...

本文以水为工质，对优化后的矩形微通道散热器(MCHS)的强制对流换热进行了实验和数值研究。采用恒体积法(CVM)和变体积法(VVM)对MCHS进行优化。从优化结果可以看出，与相邻长径比相比，长径比为3的传热系数更好，压降值更低。基于有限体积法的MCHS数值研究。通过与解析解和实验数据的比较，验证了数值计算结果。通过减小通道芯体积和改变操作条件，获得高热流密度和高换热系数。优化后的微通道宽度为700 μm，深度为2100 μm，并被350 μm的壁隔开。微通道是在铜板上用线材电火花加工而成的。

引用次数: 2

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