Rarefaction Effects on Gas Mixing in Micro- and Nanoscales

Darbandi, Masoud; Sabouri, Moslem

doi:10.1115/mnhmt2016-6604

Cited by 3 publications

(3 citation statements)

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“…Even, using the rarefaction-dependent effective diffusion coefficients presented in Ref. [14] would not be reasonable because it would result in negative values for the effective diffusion coefficient. It seems that using the higher-order constitutive laws is inevitable if one is going to use Eqs.…”

Section: Gas Mixing and Species Distributionmentioning

confidence: 99%

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A Comparative Study on the Molecular- and Continuum-Based Simulation Methods for Gas Flow and Mixing in Micro/Nanochannels

Darbandi¹,

Sabouri²,

Schneider³

2016

International Conference of Fluid Flow, Heat and Mass Transfer

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A comparative study is conducted between the molecular and continuum approaches to treat the gas flow as well as the mixing problem in micro/nanoscale channels. The molecular-based simulations are performed using the direct simulation Monte Carlo DSMC method; however, the continuum-based simulations are accomplished using the finite-volume FV method incorporating suitable slip/jump boundary conditions for the gas mixture flows. Employing these two methods, we simulate the mixing process of two gases in mixers with different micro and nano scale sizes working in both slip and transitional flow regimes. The comparisons are provided for the corresponding results of these two methods including their flow velocities, mass flow rates, species mass fractions, and diffusion fluxes. Using the outcome of the performed comparisons, we eventually describe the effects of rarefaction on the achieved accuracy of the continuum-based method.

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Section: Gas Mixing and Species Distributionmentioning

confidence: 99%

“…Detail discussions on these local effects are presented in Ref. [14]. It can be described briefly as follows.…”

Section: Diffusion Mass Fluxesmentioning

confidence: 99%

A Comparative Study on the Molecular- and Continuum-Based Simulation Methods for Gas Flow and Mixing in Micro/Nanochannels

Darbandi¹,

Sabouri²,

Schneider³

2016

International Conference of Fluid Flow, Heat and Mass Transfer

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“…In the same work, the effect of replacing a “larger” micro-mixer with many “smaller” ones was also studied. Finally, the influence of gas rarefaction on the diffusive mass transfer in slip and transitional regimes has been examined [20]. All the works related to gas mixing employ the DSMC method.…”

Section: Introductionmentioning

confidence: 99%

Gas Mixing and Final Mixture Composition Control in Simple Geometry Micro-mixers via DSMC Analysis

2019

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The mixing process of two pressure driven steady-state rarefied gas streams flowing between two parallel plates was investigated via DSMC (Direct Simulation Monte Carlo) for different combinations of gases. The distance from the inlet, where the associated relative density difference of each species is minimized and the associated mixture homogeneity is optimized, is the so-called mixing length. In general, gas mixing progressed very rapidly. The type of gas surface interaction was clearly the most important parameter affecting gas mixing. As the reflection became more specular, the mixing length significantly increased. The mixing lengths of the HS (hard sphere) and VHS (variable hard sphere) collision models were higher than those of the VSS (variable soft sphere) model, while the corresponding relative density differences were negligible. In addition, the molecular mass ratio of the two components had a minor effect on the mixing length and a more important effect on the relative density difference. The mixture became less homogenous as the molecular mass ratio reduced. Finally, varying the channel length and/or the wall temperature had a minor effect. Furthermore, it was proposed to control the output mixture composition by adding in the mixing zone, the so-called splitter, separating the downstream flow into two outlet mainstreams. Based on intensive simulation data with the splitter, simple approximate expressions were derived, capable of providing, once the desired outlet mixture composition was specified, the correct position of the splitter, without performing time consuming simulations. The mixing analysis performed and the proposed approach for controlling gas mixing may support corresponding experimental work, as well as the design of gas micro-mixers.

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