Experimental and computational study of gas flow delivered by a rectangular microchannels leak

Bergoglio, M.; Mari, D.; Chen, J.; Mohand, Hacene Si Hadj; Colin, Stéphane; Barrot-Lattes, Christine

doi:10.1016/j.measurement.2015.06.011

Cited by 10 publications

(8 citation statements)

References 15 publications

(13 reference statements)

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“…Experimental techniques described in the literature, however, mainly concern measurement of global data [15]. Most of the publications provide flowrate data through microchannels as a function of the pressure drop and the Knudsen number [16][17][18][19][20][21][22][23][24]. This global information is not sufficient to separately analyze the role of the 3 velocity slip model and the role of the a priori unknown accommodation coefficients.…”

Section: Introductionmentioning

confidence: 99%

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Mohand

Frezzotti

Brandner

et al. 2017

Experimental Thermal and Fluid Science

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Molecular tagging velocimetry is a little-intrusive technique based on the properties of specific molecules able to emit luminescence once properly excited. Several variants of this technique have been successfully developed for analyzing external gas flows or internal gas flows in large systems. There is, however, very few experimental data on molecular tagging velocimetry for gas flows in mini or microsystems, and these data are strongly affected by the molecular diffusion of the tracer molecules. In the present paper, it is demonstrated that the velocity field in gas microflows cannot be directly deduced from the measured displacement field without taking into account Taylor dispersion effects. For that purpose, the benchmark case of a Poiseuille gas flow through a rectangular channel 960 µm in depth is experimentally investigated by micro molecular tagging velocimetry using acetone vapor as a molecular tracer. An appropriate reconstruction method based on the advection diffusion equation is used to process the data and to correctly extract the velocity profiles. The comparison of measured velocities with flowrate data and with theoretical velocity profiles shows a good agreement, whereas when the reconstruction method is not implemented, the extracted velocity field exhibits qualitative and quantitative anomalies, such as a non-physical slip at the walls. The robustness of the reconstruction method is demonstrated on flows with light and heavy molecular species, namely helium and argon, at atmospheric as well as at 2 lower pressure conditions, for which diffusion effects are stronger. The obtained results represent an encouraging step for future analysis of rarefied gas microflows.

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Section: Introductionmentioning

confidence: 99%

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Mohand

Frezzotti

Brandner

et al. 2017

Experimental Thermal and Fluid Science

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“…It results in a two-dimensional flow rather than in a uniform flow in xdirection, as predicted in [13]. is obtained, which is measurable with a good accuracy for pressure driven [22] as well as for temperature driven gas microflows [23,24]. (Fig.…”

Section: Temperature Distribution and Flow Characteristicsmentioning

confidence: 53%

Analysis of flow induced by temperature fields in ratchet-like microchannels by Direct Simulation Monte Carlo

Chen

Stefanov

Baldas

et al. 2016

International Journal of Heat and Mass Transfer

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This paper presents a numerical analysis of a novel configuration of Knudsen pump for rarefied gas flow. The pumping element consists of two facing isothermal ratchet surfaces at different temperatures. The asymmetric saw-tooth-like surfaces in optimal geometrical conditions can create temperature inequalities in the near wall region and finally engender a macroscopic flow. The rarefied gas flow is numerically investigated by Direct Simulation Monte Carlo (DSMC) in the slip and transition regimes. A parametric study reveals the effects of several crucial parameters including temperature difference, Knudsen number, accommodation coefficients as well as main geometrical parameters. In particular, the results indicate that the mass flow rate reaches a maximum value for a Knudsen number around 0.1 and becomes negative for a Knudsen number close to unity.

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“…Nevertheless, the percentage of excited acetone molecules that recombine into diacetyl molecules is very low [39], so it can be considered that the emitting diacetyl molecules still diffuse in a binary background medium only made of acetone and helium. Equation (12) gives, therefore, a good representation of the tagged tracer diffusion, even for the case of acetone excited at 310 nm.…”

Section: Evaluation Of the Diffusion Coefficientmentioning

confidence: 99%

“…However, it can be noticed that Eq. (12) does not depend on the molecular tracer concentration , and only provides a first order approximation of the diffusion coefficient, which is accurate only if  is small enough. By considering that the molecular mass and the molecular diameter of acetone or diacetyl are considerably different from those of helium, the molecular tracer concentration  considered in the numerical experiments is high enough to imply that Eq.…”

Section: Evaluation Of the Diffusion Coefficientmentioning

confidence: 99%

“…Most of the experiments performed on rarefied gas flows in channels indirectly analyze the effects given by the velocity slip and temperature jump at the wall by measuring global quantities, such as mass flow rate, inlet and outlet pressures and temperatures [7][8][9][10][11][12][13][14]. To the best of our knowledge, there are no experimental data in the literature that provide local analysis of the rarefaction effect at the wall.…”

Section: Introductionmentioning

confidence: 99%

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Molecular tagging velocimetry for confined rarefied gas flows: Phosphorescence emission measurements at low pressure

Fratantonio

Rojas-Cárdenas

Mohand

et al. 2018

Experimental Thermal and Fluid Science

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Rarefied gas flows have a central role in microfluidic devices for many applications in various scientific fields. Local thermodynamic non-equilibrium at the wall-gas interface produces macroscopic effects, one of which is a velocity slip between the gas flow and the solid surface. Local experimental data able to shed light on this physical phenomenon are very limited in the literature. The molecular tagging velocimetry (MTV) could be a suitable technique for measuring velocity fields in gas micro flows. However, the implementation of this technique in the case of confined and rarefied gas flows is a difficult task: the reduced number of molecules in the system, which induces high diffusion, and the low concentration of the molecular tracer both drastically reduce the intensity and the duration of the exploitable signal for carrying out the velocity measures. This work demonstrates that the application of the 1D-MTV by direct phosphorescence to gas flows in the slip flow regime and in a rectangular long channel is, actually, possible. New experimental data on phosphorescence emission of acetone and diacetyl vapors at low pressures are presented. An analysis of the optimal excitation wavelength is carried out to maximize the intensity and the lifetime of the tracer emission. The experimental results demonstrate that a little concentration of about 5-10 % of acetone vapor excited at 310 nm or of diacetyl vapor excited at 410 nm in a helium mixture at pressures on the order of 1 kPa provides an intense and durable luminescent signal. In a 1-mm deep channel, a gas flow characterized by these thermodynamic conditions is in the slip flow regime. Moreover, numerical experiments based on DSMC simulations are carried out to demonstrate that an accurate measurement of the velocity profile in a laminar pressure-driven flow is possible for the rarefied conditions of interest.

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Experimental and computational study of gas flow delivered by a rectangular microchannels leak

Cited by 10 publications

References 15 publications

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Molecular tagging velocimetry by direct phosphorescence in gas microflows: Correction of Taylor dispersion

Analysis of flow induced by temperature fields in ratchet-like microchannels by Direct Simulation Monte Carlo

Molecular tagging velocimetry for confined rarefied gas flows: Phosphorescence emission measurements at low pressure

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