Mass Flow Rate Measurements: From Hydrodynamic to Free Molecular Regime

Ewart, Timothée; Graour, Irina A.; Perrier, Pierre; ́olans, J. Gilbert Me

doi:10.1115/icnmm2008-62177

Cited by 7 publications

(9 citation statements)

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“…However, in experiments by Ewart et al . [ 166 ], the TMAC for Ar were almost the same for different Kn ranges. Agrawal and Prabhu [ 88 ] recommended 0.926 for monatomic gases for the entire range of Kn in their review, but it was not suitable for diatomic and other gases.…”

Section: Gas-solid Interfacesmentioning

confidence: 94%

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

Cao

Sun

Chen

et al. 2009

IJMS

274

141

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This review is focused on molecular momentum transport at fluid-solid interfaces mainly related to microfluidics and nanofluidics in micro-/nano-electro-mechanical systems (MEMS/NEMS). This broad subject covers molecular dynamics behaviors, boundary conditions, molecular momentum accommodations, theoretical and phenomenological models in terms of gas-solid and liquid-solid interfaces affected by various physical factors, such as fluid and solid species, surface roughness, surface patterns, wettability, temperature, pressure, fluid viscosity and polarity. This review offers an overview of the major achievements, including experiments, theories and molecular dynamics simulations, in the field with particular emphasis on the effects on microfluidics and nanofluidics in nanoscience and nanotechnology. In Section 1 we present a brief introduction on the backgrounds, history and concepts. Sections 2 and 3 are focused on molecular momentum transport at gas-solid and liquid-solid interfaces, respectively. Summary and conclusions are finally presented in Section 4.

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Section: Gas-solid Interfacesmentioning

confidence: 94%

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

Cao

Sun

Chen

et al. 2009

IJMS

274

141

View full text Add to dashboard Cite

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“…Ewart et al [49][50][51][52] recently performed extensive experiments to measure the mass flow rates through precise microscale tubes and channels over wide pressure ranges for various gases. Figure 7 shows plots of their results for the two situations in which they provide tabular data: a circular tube (left plot) and a channel with a rectangular cross section (right plot).…”

Section: Comparison To Experimentsmentioning

confidence: 99%

“…The expressions for the general, continuum, slip, and free-molecular inlet/outlet pressures in terms of these factors and the reservoir pressures are given in Eqs. (45), (47), (51), and (49), respectively, as augmented by Eq. (33).…”

Section: Finite-length Expressionsmentioning

confidence: 99%

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Direct simulation Monte Carlo-based expressions for the gas mass flow rate and pressure profile in a microscale tube

Gallis

Torczynski

2012

Physics of Fluids

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The direct simulation Monte Carlo (DSMC) method of Bird is used to develop simple closed-form expressions for the mass flow rate and the pressure profile for the steady isothermal flow of an ideal gas through a microscale tube connecting two infinite reservoirs at different pressures but at the temperature of the tube wall. Gas molecules reflect from the tube wall according to the Maxwell model (a linear combination of specular and diffuse reflections at the wall temperature) with a unity or sub-unity value of the accommodation coefficient (the probability that molecules reflect diffusely from the wall). The DSMC-based expressions have four parameters. Two parameters are specified so that the mass flow rate reduces to the known expression in the free-molecular regime. One parameter was previously determined by comparison to DSMC simulations in the slip regime. The remaining parameter is determined by comparison to DSMC simulations for pressures spanning the transition regime with several values of the accommodation coefficient. The expressions for the mass flow rate and the pressure profile agree well with the DSMC simulations (rms and maximum differences of 2% and 5% for all cases examined), with other more complicated expressions and with recent experiments involving microscale tubes and channels for all flow regimes.

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“…Over the years, systematic understanding of internal rarefied gas flows has attracted attention in both experimental and theoretical 2 research. [6][7][8][9] So far, gas flows in straight microchannels have been investigated extensively. However, the research work for the flow in channels with bends, to the authors' best knowledge, is very limited.…”

Section: Introductionmentioning

confidence: 99%

Rarefaction throttling effect: Influence of the bend in micro-channel gaseous flow

Liu

Tang

et al. 2018

Physics of Fluids

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Micro-bends are frequently encountered in micro-electro-mechanical systems (MEMS) as a basic unit of complex geometry. It is essential for a deep understanding of the rarefied gas flow through bent channel. In this paper, a two-dimensional pressure-driven gas flow in a micro-channel with two bends is investigated by solving the Bhatnagar-Gross-Krook kinetic equation via the discrete velocity method in the slip and transition flow regimes. The results show that the mass flow rate (MFR) through the bent channel is slightly higher than that in the straight channel in the slip flow regime but drops significantly as the Knudsen number increases further. It is demonstrated that the increase of MFR is not due to the rarefaction effect but to the increase in cross-section of the bent corners. As the rarefaction effect becomes more prominent, the low-velocity zones at the corners expand and the gas flow is "squeezed" into the inner corner. The narrowed flow section is similar to the throttling effect caused by the valve, and both the changes in MFRs and the pressure distribution also confirm this effect. The classical Knudsen minimum changes due to this "rarefaction throttling effect". The Knudsen number at which the minimum MFR occurs gradually increases with the bend angle, and finally disappears in the transition flow regime. In addition, the onset of rarefaction throttling effect shifts to a smaller Knudsen number with a lower tangential momentum accommodation coefficient.

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Mass Flow Rate Measurements: From Hydrodynamic to Free Molecular Regime

Cited by 7 publications

References 0 publications

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

Molecular Momentum Transport at Fluid-Solid Interfaces in MEMS/NEMS: A Review

Direct simulation Monte Carlo-based expressions for the gas mass flow rate and pressure profile in a microscale tube

Rarefaction throttling effect: Influence of the bend in micro-channel gaseous flow

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