Michel Favre-Marinet
Centre national de la recherche scientifique
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Featured researches published by Michel Favre-Marinet.
International Journal of Thermal Sciences | 2002
Puzhen Gao; Stéphane Le Person; Michel Favre-Marinet
The present paper is devoted to experimental investigations of the flow and the associated heat transfer in two-dimensional microchannels. Scaling laws pertaining to the hydrodynamics and heat transfer in microchannels are not yet clearly established. The published results are affected by a significant scatter, owing to the various conditions used in the experiments, and, most likely, owing to the difficulty of measurements at micronic scales. The present facility was designed to modify easily the channel height e. It was then possible to investigate hydrodynamics and heat transfer in channels of height ranging from 1 mm, which corresponds to conventional size, up to 0.1 mm, where size effects are expected. Size effects were therefore tested in the same set-up and with the same channel walls for all the experiments, which were carried out with demineralized water. Measurements of the overall friction coefficient and of local Nusselt numbers show that the classical laws of hydrodynamics and heat transfer are verified for e>0.4 mm. For lower values of e, a significant decrease of the Nusselt number is observed whereas the Poiseuille number keeps the conventional value of laminar developed flow. The transition to turbulence is not affected by the channel size.
Journal of Fluid Mechanics | 2008
Gabriel Gamrat; Michel Favre-Marinet; S. Le Person; Roland Baviere; Frédéric Ayela
Three different approaches were used in the present study to predict the influence of roughness on laminar flow in microchannels. Experimental investigations were conducted with rough microchannels 100 to 300μm in height ( H ). The pressure drop was measured in test-sections prepared with well-controlled wall roughness (periodically distributed blocks, relative roughness k * = k /0.5 H ≈0.15) and in test-sections with randomly distributed particles anchored on the channel walls ( k * ≈0.04–0.13). Three-dimensional numerical simulations were conducted with the same geometry as in the test-section with periodical roughness (wavelength L ). A one-dimensional model (RLM model) was also developed on the basis of a discrete-element approach and the volume-averaging technique. The numerical simulations, the rough layer model and the experiments agree to show that the Poiseuille number Po increases with the relative roughness and is independent of Re in the laminar regime ( Re Po observed during the experiments is predicted well both by the three-dimensional simulations and the rough layer model. The RLM model shows that the roughness effect may be interpreted by using an effective roughness height k eff . k eff / k depends on two dimensionless local parameters: the porosity at the bottom wall; and the roughness height normalized with the distance between the rough elements. The RLM model shows that k eff / k is independent of the relative roughness k * at given k / L and may be simply approximated by the law: k eff / k = 1 − ( c (ϵ)/2π)( L / k ) for k eff / k >0.2, where c decreases with the porosity ϵ.
Physics of Fluids | 2005
Roland Baviere; Frédéric Ayela; S. Le Person; Michel Favre-Marinet
This article presents experimental results obtained in water flows through smooth rectangular microchannels. The experimental setup used in the present study enabled the investigation of both very small length scales (21–4.5μm) and a wide range of Reynolds numbers (0.1–300). The evolution of the friction coefficient was inferred from pressure drop versus flow-rate measurements for two types of water with different electrical conductivities. The channels were made of a silicon engraved substrate anodically bonded to a Pyrex cover. In these structures, pressure losses were measured internally with micromachined Cu–Ni strain gauges. When compared to macroscale correlations, the results demonstrate that in smooth silicon-Pyrex microchannels larger than 4μm in height, the friction law is correctly predicted by the Navier-Stokes equations with the classical no-slip boundary conditions, regardless of the water electrical conductivity (>0.1μScm−1).
ASME 2004 2nd International Conference on Microchannels and Minichannels | 2004
Roland Baviere; Frédéric Ayela; S. Le Person; Michel Favre-Marinet
This paper presents experimental results concerning water flow in smooth and rough rectangular micro-channels. It is part of a work intended to test the classical fluid mechanics laws when the characteristic length scale of inner liquid flows falls below 500μm. The method consists in determining experimental friction coefficients as a function of the Reynolds number. This implies simultaneous measurements of pressure drop and flow rates in microstructures. The two experimental apparatus used in this study enabled us to explore a wide range of length scales (7μm to 300μm) and of Reynolds number (0.01 to 8,000). Classical machining technologies were used to make micro-channels of various heights down to a scale of 100μm. Smaller silicon-Pyrex micro-channels were also made by means of silicon-based micro technologies. In these structures, friction coefficients have been measured locally with Cu -Ni strain gauges. For every height tested, both smooth and rough walls were successively used. When compared to macro-scale correlation the results demonstrate that i) In the smooth case, friction is correctly predicted by the Navier-Stokes equations with the classical kinematic boundary conditions, ii) For 200μm high channels, visualizations show transition to turbulence at Reynolds number of about 3,000. The presence of roughness elements did not significantly influence this result and iii) Roughness considerably increases the friction coefficient in the laminar regime. However, the Poiseuille number remains independent of the Reynolds number.Copyright
International Journal of Heat and Mass Transfer | 2001
Michel Favre-Marinet; E.B. Camano Schettini
Abstract This paper describes an experimental investigation of the density field of coaxial jets with large density differences. These flows are characterised by a low velocity–high density inner jet surrounded by a high velocity–low density annular jet. The density field was determined by a thermo-anemometric method based on a new version of an aspirating probe. Measurements show that mixing is directly dependent upon the flow dynamics in the near-field region. As a result, density effects on mixing as well as on the flow dynamics are rather well taken into account by considering the specific outer to inner jet momentum flux ratio M and not separately the density and the velocity ratios. For a given value of M , however, a slight enhancement of mixing is found for density ratios much smaller than one (≈0.14).
Journal of Fluids Engineering-transactions of The Asme | 2006
Roland Baviere; Gabriel Gamrat; Michel Favre-Marinet; S. Le Person
Numerical modeling and analytical approach were used to compute laminar flows in rough-wall microchannels. Both models considered the same arrangements of rectangular prism rough elements in periodical arrays. The numerical results confirmed that the flow is independent of the Reynolds number in the range 1-200. The analytical model needs only one constant for most geometrical arrangements. It compares well with the numerical results. Moreover, both models are consistent with experimental data. They show that the rough elements drag is mainly responsible for the pressure drop across the channel in the upper part of the relative roughness range.
Microscale Thermophysical Engineering | 2004
Michel Favre-Marinet; S. Le Person; Adrian Bejan
The objective of the present article is to compare previous experimental data of Gao et al. [20] to the predictions of Bejan and Sciubbas analysis [7] on the optimal spacing for maximum heat transfer from a package of parallel plates. Experimental investigations of the flow and the associated heat transfer were conducted in two-dimensional microchannels in order to test possible size effects on the laws of hydrodynamics and heat transfer and to infer optimal conditions of use from the measurements. The test section was designed to modify easily the channel height e between 1 mm and 0.1 mm. Measurements of the overall friction factor and local Nusselt numbers show that the classical laws of hydrodynamics and heat transfer are verified for e > 0.4 mm. For lower values of e, a significant decrease of the Nusselt number is observed, whereas the Poiseuille number continues to have the conventional value of laminar developed flow. The transition to turbulence is not affected by the channel size. The experimental data were processed by using the dimensionless parameters of Bejan and Sciubbas analysis [7]. For fixed pressure drop across the channel, a maximum of heat transfer rate density is found for a particular value of e. The corresponding dimensionless optimal spacing and heat transfer rate density are in very good agreement with the predictions of Bejan and Sciubba. This article reports the first time that the optimal spacing between parallel plates is determined experimentally.
Journal of Fluids Engineering-transactions of The Asme | 2003
G. Grégoire; Michel Favre-Marinet; F. Julien Saint Amand
The turbulent flow close to a wall with two-dimensional roughness is computed with a two-layer zonal model. For an impermeable wall, the classical logarithmic law compares well with the numerical results if the location of the fictitious wall modeling the surface is considered at the top of the rough boundary. The model developed by Wilcox for smooth walls is modified to account for the surface roughness and gives satisfactory results, especially for the friction coefficient, for the case of boundary layer suction
ASME 2003 1st International Conference on Microchannels and Minichannels | 2003
Michel Favre-Marinet; S. Le Person; Adrian Bejan
Experimental investigations of the flow and the associated heat transfer were conducted in two-dimensional microchannels in order to test possible size effects on the laws of hydrodynamics and heat transfer and to infer optimal conditions of use from the measurements. The test section was designed to modify easily the channel height e between 1 mm and 0.1 mm. Measurements of the overall friction factor and local Nusselt numbers show that the classical laws of hydrodynamics and heat transfer are verified for e > 0.4 mm. For lower values of e, a significant decrease of the Nusselt number is observed, whereas the Poiseuille number continues to have the conventional value of laminar developed flow. The transition to turbulence is not affected by the channel size. For fixed pressure drop across the channel, a maximum of heat transfer rate density is found for a particular value of e. The corresponding dimensionless optimal spacing and heat transfer rate density are in very good agreement with the predictions of Bejan and Sciubba (1992). This paper is the first time that the optimal spacing between parallel plates is determined experimentally.Copyright
ASME 2004 2nd International Conference on Microchannels and Minichannels | 2004
Gabriel Gamrat; Michel Favre-Marinet; Dariusz Asendrych
The paper presents both three and two-dimensional numerical analysis of convective heat transfer in microchannels. The three-dimensional geometry of the microchannel heat sink followed the details of the experimental facility used during a previous research step. The heat sink consisted of a very high aspect ratio rectangular microchannel. Two channel heights, namely 1mm and 0.3mm (0.1mm), were used for 3D (2D) numerical model respectively. Water was employed as the cooling liquid. The Reynolds number ranged from 200 to 3000. In the paper, the thermal entrance effect is analyzed in terms of heat transfer efficiency. Finally, the comparison between measured and computed heat flux and temperature fields is presented. Contrary to the experimental work, the numerical analysis did not reveal any significant scale effect in heat transfer in microchannel heat sink up to the smallest size considered (0.1 mm).