A. Montillet

Nantes université

A systematic experimental investigation of the dynamics of a Newtonian drop in microscopic cross-slot of a shear thinning and inelastic fluid (aqueous solutions of xanthan) is presented. The flows are driven at large Reynolds numbers and are relevant to efficient high-throughput emulsification in microchannels. Depending on the initial size of the...

This work is part of a study aiming to design a high-throughput foaming microsystem. The main focused field of application is the food industry. With the objective of improving the design of the microdevice, the effects of the geometry and the nature of the liquid base are presently investigated through visualizations of the flow typology of bubble...

The Liquid–liquid dispersion process is experimentally investigated to manufacture oil-in-water emulsion working at high flowrates in the cross-slot type of microfluidics. Two cross layouts, namely symmetric and asymmetric configurations, are compared via characterizing the droplet size and size distribution. Automated granulometry is implemented o...

The viscosities of solutions formulated with xanthan gum and xanthan gum with whey protein isolates are experimentally characterized and modeled over a wide range of shear rates [10−3 to 105 s−1]. As shown by numerous studies [1, 2], the generation of vortices in the cone-plate geometry is making viscosity measurements beyond a certain shear rate u...

This work investigates the quality of emulsions obtained from fast emulsification in a microsystem implemented at high throughput. The aim is to manufacture oil in water (O/W) emulsions in which bioactive ingredients could be encapsulated. These emulsions may be of interest for cosmetic, nutraceutical and/or pharmaceutical applications. A microsyst...

Experimental study on drop breakage is carried out in the microchannels utilizing head-on impingement configuration by observing a single drop breakup process. In this study, the breakage of oil drops with a diameter ranging from 30 to 200 μm is investigated in the vicinity of flows impingement region by using high-speed photography at varied flow...

The Front Cover illustrates the fabrication of highly concentrated dispersions of fluorescent organic nanoparticles (FONs) using a microfluidic chamber with high impacting flows, allowing for fine size control (picture courtesy of Jules Bellettre alias PRBLMS). More information can be found in the Article by E. Ishow and co‐workers.

Highly concentrated dispersions of fluorescent organic nanoparticles (FONs), broadly used for optical tracking, bioimaging and drug delivery monitoring, are obtained using a newly designed micromixer chamber involving high impacting flows. Fine size tuning and narrow size distributions are easily obtained by varying independently the flow rates of...

Liquid-liquid dispersion by head-on impingement in a cross-slot microfluidic device to form oil-in-water emulsion is experimentally investigated at broad range of flow rate conditions. Reynolds number based on the continuous aqueous phase flow is changed from 1000 to 7000 and the oil dispersed volume fraction varies between 3% and 30%. The flow pat...

The adsorption process in liquid phase is a topic which is thoroughly studied experimentally, and attracts an increasing attention in the modeling field. Attempts of describing the breakthrough curves, which show the saturation of the adsorbing material, go back to Bohart's and Adams' works in 1920. Other equations with less restrictive assumptions...

The context of this work is to explore the possibility of making bio-sourced foams at high throughput in microsystems. A fundamental element for the development of new technologies based on biphasic flows in microchannels is a good characterization and knowledge of hydrodynamics. In this contribution, cross slot microsystems are tested as a promote...

This work is focused on the development of a compact continuous process for the production of food foams with controlled properties. Cross-shaped channels of infra millimeter size are used and the two-phase flow pattern is analyzed in order to identify the mechanisms of bubble deformation and breakup at very high velocities [~2–20 m s⁻¹]. Two diffe...

Water in diesel emulsion (WiDE) is a viable solution for lowering both NOx and Soot emissions from compression ignition (CI) engines. In this paper, the effect of WiDE on the combustion process and exhaust emissions of a prototype optically accessible CI engine was investigated through conventional in-cylinder pressure measurements and optical diag...

In this investigation, puffing and micro-explosion occurrence in emulsified fuels are studied. The emulsified fuels are formulated using a micro-channel emulsifier, a blend of rapeseed oil in diesel fuel as continuous phase, water as dispersed phase and Sorbitan Sesquioleate as surfactant. Several stable dispersed systems are obtained, classified a...

The selection of a geotextile to prevent the soil suffusion in a civil engineering work is a classical problem. The internal erosion is a key factor as the migration of fine particles damages the integrity of the soil structure. This work deals with the problem of using a draining system consisting of a layer of soil and a geotextile sheet in order...

The objective of this experimental work is to design an original microfluidic mixer for continuous emulsification of small fractions of water in a lipid phase. This system is aimed to be integrated on-line in the process so as to avoid the use of a surfactant. The currently targeted application is a better combustion of water-supplemented alternati...

The invention relates to a device (1) for carrying out continuous emulsion of two immiscible fluids. Said device has: a first microsystem (2) including at least two micro-channels (23, 24) for intake of each fluid, of different respective cross sections S1 and S2, which are offset and face each other along a central intake axis A; at least two micr...

The scope of this investigation is to formulate and characterize emulsified fuels using a micro-channel emulsifier and compare this against emulsions produced using a magnetic stirrer. The emulsified fuels are formulated using a blend of rapeseed oil in diesel fuel as continuous phase and water as dispersed phase, as well as Sorbitan Sesquioleate a...

The objective of this work is to design an original microfluidic mixer for continuous emulsification of small fractions of water in a lipid phase. This system is aimed to be integrated on-line in the process so as to avoid the use of a surfactant. The targeted application is a better combustion of alternative biofuels in boilers, turbines or intern...

Sand beds are commonly used in many industrial applications, mainly as a filtering medium, and in civil engineering. However, predicting the pressure drop of liquid flow through sand beds with simple models remains elusive. Among the many factors that explain this failure is the difficulty of determining tortuosity and effective bed porosity. This...

An extensional flow involving water-in-oil emulsification is created in an impinging micro-channel. A focalised beam of laser light is polarised in the direction of the channel, and its amount of collected light through the emulsion is measured. Polarized light is expected tointeract with spherical, stretched and elongated droplets. The obtained ma...

An extensional flow involving water-in-oil emulsification is created in an impinging micro-channel. A focalised beam of laser light is polarised in the direction of the channel, and its amount of collected light through the emulsion is measured. Polarized light is expected tointeract with spherical, stretched and elongated droplets. The obtained ma...

The emulsification is well known for being considered as a solution for improving biodiesel combustion. In this extent, the size of the dispersed droplets is crucial to favour micro-explosions and optimising the combustion. The present mini-channel operates liquid/liquid dispersion at higher flow rates than with usual implementations of minichannel...

In this book, the authors discuss the processes, new technology and current applications of emulsification. Topics include ultrasound-assisted emulsification microextraction; microbial emulsifiers and their environmental applications potential; alternative methods for emulsification; the physical and chemical modifications on emulsifying properties...

The emulsification is well known for being considered as a solution for improving biodiesel combustion. In this extent, the size of the dispersed droplets is crucial to favour micro-explosions and optimising the combustion. The present mini-channel operates liquid/liquid dispersion at higher flow rates than with usual implementations of mini-channe...

The understanding of physical phenomena such as flow behavior is essential in order to develop appropriate micromixers for industrial or biomedical applications. In this paper, the relevance of an electrochemical method is demonstrated for a microfluidic diagnostic in the case of high fluctuating flow, over a wide range of Reynolds numbers (300 < R...

Mass transfer within the T-shaped and cross-shaped micromixers has been studied using CFD and confocal laser scanning microscopy methods. The concentration profiles, based on flow regimes, were used to compare the T- and cross-geometries. The cross-shaped micromixer tends to intensify the mixing and this is occurring for lower flow rates in compari...

Micro-electrodes made of platinum have been used to measure the local shear rate on the surface of a cylinder (length-to-diameter ratio of 11–12) exposed to the fully developed laminar flow of power-law fluids in a vertical pipe. Two Newtonian and two shear-thinning solutions are used as model test fluids to ascertain the influence of shear-thinnin...

The particular benefits of microfluidic systems, in terms of heat and mass transfer enhancement, require conducting local flow diagnostics, especially when unsteady properties of the microflow can play a critical role at the reaction interface, as currently observed in the fields of bioengineering and chemical engineering. The present paper focuses...

The understanding of physical phenomena such as flow behaviour and mass transfer performance is needed in order to develop appropriate micromixers for industrial or biomedical applications. In this article, the flow behaviour of the T-shaped and the cross-shaped micromixers with square cross-section are studied through numerical and experimental in...

The present paper reports a study conducted to examine several sands with a large spread of particle size in order to validate the modelling of both Darcy's and Forchheimer's law parameters, which could be applied to any kind of sand. An experimental set-up has been specially conceived to generate hydraulic gradients within fine sands higher than 6...

The research work presented in this thesis deals with the numerical and experimental characterization of the flow and mass transfer in the T-shape and cross-shape micromixers. The square section of channel is equal to 400 μm. The aim is to intensify the liquid mixing by the flow patterns and channel geometries. In the first part of study, the chara...

Les micromélangeurs constituent une des applications les plus importantes de la microfluidique. L’objectif de notre travail est de caractériser par simulations numériques, par mesures polarographiques et PIV, l’écoulement et le transfert de matière au sein de micromélangeurs de type tés (T) et croix. Il s’agit d’identifier les meilleures conditions...

The understanding of physical phenomena such as flow behaviour and mass transfer performance is needed in order to develop appropriate micromixers for industrial or biomedical applications. In this work, CFD is used to characterize the flow and the liquid mixing quality in a micromixer as a function of the Reynolds number. Two micromixers are studi...

Knowledge of local hydrodynamics inside miniaturized systems is necessary for industrial applications. In this work two techniques are used in order to characterize the flow in a network of crossing minichannels. These techniques are respectively based on the particle image velocimetry and on electrochemical microsensors used in the local diagnosti...

The study of microfluidic systems is an important research challenge related to the design of microdevices for chemical processes. The understanding of physical phenomena, such as flow behaviour and heat and mass transfer performance is needed in order to develop these microsystems for industrial applications as mixers, reactors or heat exchangers....

Computational fluid dynamic simulations are used to characterize the flow and the liquid mixing quality in a micromixer as a function of the Reynolds number. Two micromixers are studied in steady flow conditions; they are based on two geometries, respectively T-shaped and cross-type (⊤ and + shapes). Simulations allow, in the case of ⊤ micromixers,...

This work aims at validating and extending the applicability of an existing correlating equation for predicting pressure drop through packed beds of spheres. A new set of data points out its use for bed geometric aspect ratio D/dpart in the range 3.8–14.5, in the case of dense packings. The case of loose packings is also discussed using literature...

The global mass transfer and the local flow structure inside a set of crossing minichannels were characterized using the electrodiffusion method. The individual square-cross channel sections (a=1.5mm in sides) intersect at right-angles in order to form the flow cell. An array of 39 circular platinum electrodes (0.25mm in diameter) was flush-mounted...

Une étude expérimentale de l’hydrodynamique dans une installation miniaturisée comportant un réseau de mini-canaux croisés a permis la caractérisation des régimes d’écoulement sur une large gamme de nombres de Reynolds. Ce réseau constitué de 10 mini-canaux de section carrée de 1,5 mm de côté se croisant à angle droit est gravé dans une cellule en...

Scale-up and prediction of performance of granular activated carbon (GAC) fixed bed adsorbers require the knowledge of the structural parameters of the particles and of the corresponding beds. A set of suitable and relatively simple methods including alumina and helium pycnometry, image analysis and water permeametry are therefore proposed and vali...

The variation of the pressure drop measured as a function of the fluid velocity through a packed bed of spheres is presented and discussed in the range of panicle Reynolds number 30-1500. Based on previous studies, the observed limit of validity of the so-called Forchheimer law may be attributed to the concomitant effects of the finite character of...

In chemical engineering processes as well as in everyday life situations, porous media are commonly and frequently encountered: packed beds of cylindrical catalysts used in the fine chemical manufacturing sector or in the petroleum industry, packed beds of granular activated carbon or beds of multisized resin beads applied for water treatment, carb...

The aim of this study is to evaluate the external liquid-to-particle mass transfer coefficient in packed beds of extruded activated carbon particles. The coefficient is evaluated by an experimental method based on the electrochemical study of mass transfer for nickel particles presenting an equivalent granulometry to that of the extruded carbonaceo...

The subject of non-Darcy flow spans many engineering disciplines. The Authors have presented the results of interesting research on flow through a fine porous media in which high Reynolds-numbers were induced. A number of issues can be raised: (i) In their Abstract the Authors make the rather definitive assertion that non-Darcy flow begins at a Rey...

A model of liquid-to-particle mass transfer in packed beds with single phase non-Newtonian creeping flow is derived using a coherent approach which associates the Lévêque solution with a capillary-type representation of the porous structure. The model is compared to experimental data obtained with spherical and anisotropic parallelepipedal particle...

Fixed beds of anisotropic particles are commonly involved in chemical engineering processes: beds of cylindrical catalyst pellets or beds of wood shavings in paper industry. The characterization of the spatial variations of their structural properties is of great importance for flow modelling purposes. In this work, we intend to produce new data co...

The pore Reynolds number is shown to be a convenient criterion for determining the limit of validity of creeping flow regime for Newtonian and non-Newtonian purely viscous fluid flow through fixed beds of various structures. For a non-Newtonian purely viscous fluid flow, only the limit of Darcy's or creeping flow regime has been determined. A globa...

In this paper, the hydrodynamics in the FM01-LC electrolyzer is studied by flow visualization and residence time distribution (RTD). Divided and undivided modes are studied by direct visualization, with two injection points. The use of foams instead of turbulence promoters as well as that of electrodes without turbulence promoters is tested. In the...

A hydrodynamic study and an ethanol biodegradation were carried out in an experimental biofilter using wood bark as packing material. The Comiti and Renaud model was used in order to determine, from pressure drop measurements, the tortuosity and the dynamic specific surface area of the packing material, and its structural parameters, considering th...

In this work, the flow modelling of a toroidal reactor in batch or continuous operating modes is obtained by the experimental determination of the tracer concentration evolution in batch mode and the residence time distribution in continuous configuration, for mixing Reynolds numbers between 15 and 8×104 with water and glucose solutions. The compar...

This work deals with hydrodynamics in porous media beyond the end of the stable laminar regime, at higher Reynolds numbers. Local measurements of current fluctuations were carried out with electrochemical probes located at different positions in the porous media. Owing to the use of the electrochemical transfer function, the spectrum of velocity gr...

This work is part of a global study of flow regimes in porous media beyond Darcy regime. In view of determining the end of stable laminar regime in various porous media such as beds packed with spheres, stratified media and reticulated media, electrochemical micro-probes are inserted inside the medium and at the wall of test sections. Local instant...

Experimental results for isothermal Newtonian flow through a high porosity anisotropic porous medium are provided. The porous medium is formed by a knitted stainless steel wire mesh rolled up to form a cylindrical plug. This kind of porous medium is generally used as a mist eliminator in the chemical and petroleum industries. Experimental results a...

A study of flow visualization and residence time distribution is provided in order to model the flow between two electrodes in a commercial filter-press reactor, the ElectroSynCell from Electrocell AB. Flow visualization indicates that both axial and lateral dispersion phenomena occur and a global plug flow behaviour is observed. The flow distribut...

This work aims at giving a first insight of non-Newtonian fluid flow through synthetic foams.At first, a review of experimental pressure drops measured with Newtonian fluids through various foams is proposed as well as a recall of a capillary-type flow model used to determine structural parameters. In this particular case of Newtonian fluid flow, a...

The cathodic reduction of ferricyanide ions is used to characterize liquid—solid mass transfer in porous electrodes in the creeping flow regime. Our study deals with packed beds of spheres, long cylinders and plates of low height-to-side ratio. Correlations are proposed and compared with predictive equations based on the association of the capillar...

This article deals with the study of a filter-press type electrolyser (ElectroSynCell of ElectroCell AB) with an undivided configuration obtained by replacing, for the working electrode, the usual inert turbulence promoter by a three-dimensional nickel foam electrode. The mass transfer rates are investigated at the working electrode and at the coun...

Experimental results for isothermal Newtonian flow through metallic foams are analysed in comparison with a theoretical model and the results interpreted. In both the Darcy and non-Darcy regimes the results show promise for the accurate theoretical prediction of fluid dynamic phenomena in foamlike porous materials of very high porosity.

This paper focuses on mass transfer characteristics of classical filter-press electrochemical reactors without membranes. In the tested configuration, the working electrode consists of a lane plate with a sheet of foam and the counter-electrode consists of a plane plate with a turbulence promoter. The global mass transfer coefficients of the two el...

The aim of the present paper is to investigate the application of nickel foam electrodes in classical filter-press type electrochemical cells. For this purpose the ElectroSynCell, commercialized by Electrocell AB, has been used. The interest of using metallic foams linked to a classical plane plate is to improve the performance of the electrochemic...

This paper deals with the experimental study of the axial dispersion phenomenon during flow through and by fixed beds packed with sheets of nickel foams. Its purpose is to characterize the hydrodynamic behaviour of a liquid flowing through different nickel foams according to configurations corresponding to the two working modes of volumic electrode...

An experimental technique, permeametry, is carried out in order to determine the dynamic specific surface area and the tortuosity of three nickel foams. A capillary-type model allows calculation of these structural parameters from pressure-drop measurements. Studying pressure drops of two different flow configurations also allows quantification of...