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Numerical simulation of microchannel network with complex geometry

Niklas M., Favre-Marinet M., Asendrych D.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2005

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Vol. 53, nr 4

351-359

EN

The paper presents the results of a numerical study devoted to the hydraulic properties of a network of parallel triangular microchannels (hydraulic diameter Dh = 110 [mi]m). Previous experimental investigations had revealed that pressure drop through the microchannels system dramatically increases for the Reynolds number exceeding value of 10. The disagreement of the experimental findings with the estimations of flow resistance based on the assumption of fully developed flow were suspected to result tram the so-called scale effect. Numerical simulations were performed by using the classical system of flow equations (continuity and Navier-Stokes equations) in order to explain the observed discrepancies. The calculations showed a very good agreement with the experimental results proving that there is no scale effect for !he rnicrochannels considered, i.e. the relevance of the constitutive flow model applied was confirmed. It was also clearly indicated that the excessive pressure losses in the high Reynolds number range are due to the secondary flows and separations appearing in several regions of the microchannel system.

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Numerical modelling of fluid flow and heat transfer in microchannels

Favre-Marinet M., Gamrat G., Asendrych D.

Turbulence : international journal

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2004

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Vol. 10

75-75

EN

The work concerns three-dimensional numerical modelling of fluid flow and heat transfer in large-span rectangular microchannel. Channel height being the key geometrical parameter, was varied hi the range from 0.3 to 1 mm. The width of channel was equal to 250 mm what allowed to treat microchannel as a two-dimensional. The computational domain followed the details of experimental facility used in preceding research step. The numerical model assumed the laminar flow of water (506 < Re < 2023) with temperature-independent properties. The results obtained in experimental trials exhibited strong reduction of Nusselt number in comparison to theoretical law. The motivation of current simulation was to identify the reasons of discrepancies between theoretical predictions and experimental results. Among the explanations the effect of axial conduction resulting from complex geometry was supposed to have the highest significance. Main goal of current work was numerical prediction of coupling conduction-convection effect and its influence on Nusselt number values. Additionally the influence of entrance effects on the deviation of beat transfer results from the macroscale laws was taken into consideration. Comparison between experimental and numerical results was an essential part of current work and allowed to point out the weakness of some simplifications being assumed during interpretation of experimental data (i.e. uniform distribution of heat flux along fluid/solid interface turned out to be the origin of significant errors). Furthermore numerical simulations exhibited that significant part of heat resulting from conduction and insufficient insulation was delivered to water in inlet container. It could lead to false estimation of bulk temperature at channel inlet and to reduction of heat transfer effectiveness at the beginning part of microchannel. Results of current work allowed not only for verification of experimental conclusions, but also pointed out the weakness of already utilised experimental setup and were helpful in a design of a new experimental installation.

3

ERCOFTAC special interest group #38 on microfluidics and micro heat transfer : the report on the kick-off meeting

Favre-Marinet M., Steenhoven van A., Drobniak S., Asendrych D.

Turbulence : international journal

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2004

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Vol. 10

59-65

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Numerical modelling of flow in microchannels

Niklas M., Favre-Marinet M.

Turbulence : international journal

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2002

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Vol. 8-9

149-158

EN

The paper presents numerical study of the flow in the system of microchannels. The computations were based on the classical laws of hydraulics. Comparison of the numerical results with experimental ones showed that is the mjcrocharme! system considered no scale effects were observed.

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Experimental techniques in gas mixtures applications to boundary layers and jets

Favre-Marinet M.

Turbulence : international journal

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1998

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Vol. 4

83-95

EN

The paper presents new experimental techniques measurements in variable density flows. The capabilities of the aspirating and hot-wire/film probes to measure density, velocity and shear stress are described with the special attention attached to the measurements in boundary layers.