Experimental study of the gas flows through channels with circular cross sections

Hadj-Nacer, Mustafa; Perrier, Pierre; Méolans, J. Gilbert; Graur, Irina; Wüest, M.

doi:10.1088/1742-6596/362/1/012025

Cited by 6 publications

(4 citation statements)

References 20 publications

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“…The experimental apparatus uses the “constant volume technique” − and is shown in Figure a. Two test chambers of constant volume constructed from stainless steel are connected by the microchannels under test.…”

Section: Methodsmentioning

confidence: 99%

Enhanced Water Vapor Flow in Silica Microchannels: The Effect of Adsorbed Water on Tangential Momentum Accommodation

Lei

McKenzie

2015

J. Phys. Chem. C

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Maxwell introduced the tangential momentum accommodation coefficient (TMAC) in 1879 to describe boundary conditions in fluid flow. Recent findings of anomalously high gas flow rates in carbon nanotubes have been attributed to smooth hydrophobic walls that reduce TMAC. Here we report the first measurements of water vapor flows in microchannels over a wide humidity range and show that for silica there is a range of humidity over which an adsorbed water layer reduces the TMAC in a way that depends on the surface conditions. We develop a model that unifies Maxwell's ideas on TMAC with Langmuir's ideas on adsorption. We fit TMAC data with the model using two stages of Langmuir adsorption and derive total adsorption isotherms for water on silica. The first adsorption stage reduces TMAC by smoothing the surface. The second stage is bulk liquid that imparts large TMAC. We find that leak testing of moisture barriers with an ideal gas such as helium may not be accurate for critical applications and recommend direct measurements of the water leak rate.

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Section: Methodsmentioning

confidence: 99%

Enhanced Water Vapor Flow in Silica Microchannels: The Effect of Adsorbed Water on Tangential Momentum Accommodation

Lei

McKenzie

2015

J. Phys. Chem. C

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“…In the following year, Smoluchowski [4] extended Knudsen's equation by using Maxwell's definition for the tangential momentum accommodation coefficient (TMAC) which describes the fraction of molecules which suffer fully diffuse reflections at the walls in which tangential momentum is lost, with the remainder having fully specular reflections in which tangential momentum is preserved. Up to the present time, the goal of obtaining increasingly accurate and convenient methods for predicting gas flow in cylindrical channels is still being pursued [20,46,53,55,56]. Here we outline the Poiseuille law for the continuum flow regime [21], the modified Poiseuille law for the slip flow regime [56] and introduce the extended Navier-Stokes equation (theory of Cha and McCoy [46]) for the transition and molecular flow regimes.…”

Section: Gas Flow In a Uniform Cylindrical Channelmentioning

confidence: 99%

“…Up to the present time, the goal of obtaining increasingly accurate and convenient methods for predicting gas flow in cylindrical channels is still being pursued [20,46,53,55,56]. Here we outline the Poiseuille law for the continuum flow regime [21], the modified Poiseuille law for the slip flow regime [56] and introduce the extended Navier-Stokes equation (theory of Cha and McCoy [46]) for the transition and molecular flow regimes.…”

Section: Gas Flow In a Uniform Cylindrical Channelmentioning

confidence: 99%

The physics of confined flow and its application to water leaks, water permeation and water nanoflows: a review

2016

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This review assesses the current state of understanding of the calculation of the rate of flow of gases, vapours and liquids confined in channels, in porous media and in permeable materials with an emphasis on the flow of water and its vapour. One motivation is to investigate the relation between the permeation rate of moisture and that of a noncondensable test gas such as helium, another is to assist in unifying theory and experiment across disparate fields. Available theories of single component ideal gas flows in channels of defined geometry (cylindrical, rectangular and elliptical) are described and their predictions compared with measurement over a wide range of conditions defined by the Knudsen number. Theory for two phase flows is assembled in order to understand the behaviour of four standard water leak configurations: vapour, slug, Washburn and liquid flow, distinguished by the number and location of phase boundaries (menisci). Air may or may not be present as a background gas. Slip length is an important parameter that greatly affects leak rates. Measurements of water vapour flows confirm that water vapour shows ideal gas behaviour. Results on carbon nanotubes show that smooth walls may lead to anomalously high slip lengths arising from the properties of 'confined' water. In porous media, behaviour can be matched to the four standard leaks. Traditional membrane permeation models consider that the permeant dissolves, diffuses and evaporates at the outlet side, ideas we align with those from channel flow. Recent results on graphite oxide membranes show examples where helium which does not permeate while at the same time moisture is almost unimpeded, again a result of confined water. We conclude that while there is no a priori relation between a noncondensable gas flow and a moisture flow, measurements using helium will give results within two orders of magnitude of the moisture flow rate, except in the case where there is anomalous slip or confined water, when moisture specific measurements are essential.

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“…This apparatus uses the technique known in the literature as the constant-volume technique − and is shown in Figure (a). Two test chambers of constant volume constructed from stainless steel are connected by the microchannels under test at room temperature.…”

Section: Experimental Sectionmentioning

confidence: 99%

Science of Water Leaks: Validated Theory for Moisture Flow in Microchannels and Nanochannels

et al. 2015

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Water is ubiquitous; the science of its transport in micro- and nanochannels has applications in electronics, medicine, filtration, packaging, and earth and planetary science. Validated theory for water vapor and two-phase water flows is a "missing link"; completing it enables us to define and quantify flow in a set of four standard leak configurations with dimensions from the nanoscale to the microscale. Here we report the first measurements of water vapor flow rates through four silica microchannels as a function of humidity, including under conditions when air is present as a background gas. An important finding is that the tangential momentum accommodation coefficient (TMAC) is strongly modified by surface layers of adsorbed water molecules, in agreement with previous work on the TMAC for nitrogen molecules impacting a silica surface in the presence of moisture. We measure enhanced flow rates for two-phase flows in silica microchannels driven by capillary filling. For the measurement of flows in nanochannels we use heavy water mass spectrometry. We construct the theory for the flow rates of the dominant modes of water transport through each of the four standard configurations and benchmark it against our new measurements in silica and against previously reported measurements for nanochannels in carbon nanotubes, carbon nanopipes, and porous alumina. The findings show that all behavior can be described by the four standard leak configurations and that measurements of leak behavior made using other molecules, such as helium, are not reliable. Single-phase water vapor flow is overestimated by a helium measurement, while two-phase flows are greatly underestimated for channels larger than 100 nm or for all channels when boundary slip applies, to an extent that depends on the slip length for the liquid-phase flows.

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Experimental study of the gas flows through channels with circular cross sections

Cited by 6 publications

References 20 publications

Enhanced Water Vapor Flow in Silica Microchannels: The Effect of Adsorbed Water on Tangential Momentum Accommodation

Enhanced Water Vapor Flow in Silica Microchannels: The Effect of Adsorbed Water on Tangential Momentum Accommodation

The physics of confined flow and its application to water leaks, water permeation and water nanoflows: a review

Science of Water Leaks: Validated Theory for Moisture Flow in Microchannels and Nanochannels

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