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Stefan VAN VAERENBERGH


coordonnées


Ecole polytechnique de Bruxelles
Stefan VAN VAERENBERGH
tel 02 650 31 75, fax 02 650 31 26, Van.Vaerenbergh.Stefan@ulb.ac.be
Campus du Solbosch
CP165/62, avenue F.D. Roosevelt 50, 1050 Bruxelles




unités de recherche


Chimie-physique E.P.- Microgravity Research Center [Physical Chemistry Dept A.S. - Microgravity Research Center] (MRC)



projets


Prodex DCMIX [Prodex DCMIX]
Le projet DCMIX étudie les transports de matière dans les systèmes ternaires au travers d'expériences en microgravité. Il existe plusieurs formalismes et théories dans la littérature pour décrire la thermodiffusion dans un système multicomposant mais un manque de données empêche leur validation. Seul un petit nombre de techniques expérimentales permet d'étudier un système binaire avec des coefficients Soret négatifs. La vision à long terme consiste à comprendre le fonctionnement de la diffusion et de la thermodiffusion dans les systèmes multicomposants.Les méthodes optiques modernes requièrent (N-1) sources de lumière indépendante pour analyser un système à N composantes. Deux longueurs d'ondes lambda son donc nécessaires pour mesurer les coefficients de diffusion dans un mélange ternaire. Le succès de l'expérience dépend non seulement de la variation de l'indice de réfraction en fonction de la concentration (dn/ dc) de chaque composant mais également de la matrice composée des [(d(nlambda),j/d(ci)], i,j=1,2. Deux lasers (, lambda=670 nm et lambda=925) sont installés sur l'instrument SODI à bord de l'ISS. A l'aide de cet instrument La première DCMIX en microgravité a d'ores et déjà analysé le système Tétrahydronaphtalène/ Isobutylbenzène/ Dodécane.La prochaine expérience concerne le système Toluène/ Méthanol/ Cyclohexane. Les études préliminaires révèlent la présence dans ce système de coefficients Soret négatifs.Objectifs: - Mesures de coefficient de diffusion et de thermodiffusion dans des mélanges ternaires qui sont fortement affectée par la présence de convection. - Permettre de comprendre comment les coefficients de thermodiffusion dans les systèmes ternaires sont relies à ceux des systèmes binaires. http://67.199.102.30/mrc/fr/projects.cfm?id=1013 [DCMIX project is focused on the investigation of the mass transport in ternary mixtures including experiment under microgravity conditions. Different formalisms and theories exist in literature to describe the thermodiffusion effect in multicomponent mixtures but there is a lack of experimental data for their validations. There exist only a few experimental techniques which allow studying the binary systems with negative Soret coefficients. The long-term vision is to understand kinetic of thermal diffusion in multicomponent systems.Application of modern optical methods requires (N-1) independent light sources for the mixture with N components. Two wavelengths lambda i are needed for measuring (thermo) diffusion coefficients in ternary mixtures. The success of the experiments depends not only on variation of refractive index with concentration (dn/ dc) of individual components but on the matrix composed by [(d(nlambda),j/d(ci)], i,j=1,2. Two light sources, lambda=670 nm and lambda=925 nm are available inside SODI instrument onboard the ISS. The first microgravity experiment DCMIX analyzed the hydrocarbon mixture (TNH-IBB-C12 ) .The next subject of DCMIX is the mixture Toluene (T) / Methanol (M) / Cyclohexane (CH). The preliminary ground experiment reveals strong instability which indicates at negative Soret coefficients. Objectives :' Measurement of diffusion and thermodiffusion coefficients in ternary mixture which are strongly affected by convection in the presence of gravity. ' Achieve a quantitative understanding of how thermodiffusion coefficients in ternary mixtures are related to those in binary mixtures.http://67.199.102.30/mrc/fr/projects.cfm?id=1013]

Heat Transfer Prodex [Heat Transfer Prodex]
Heat Transfer [Heat Transfer is an ubiquitous phenomena found in many industrial applications. In some applications like electronic cooling it has become the limiting factor dictating further development. Boiling, evaporation and condensation are used in many engineering fields and, particularly, in space applications. Experimental and theoretical study of various physical phenomena in fluids in the vicinity of the contact line on simple and complex substrates is very important in view of space exploration and the micro-cooling, micro-fluidic devices.We at MRC-ULB are performing work on Loop Heat Pipes for terrestrial and aerospace application. Loop Heat Pipes are passive heat transfer devices able to transfer heat over very long distances (up to 10-15m) with small temperature differences. They have been conceived for space application in the late 70's but are being applied to terrestrial application as well.We are also looking at condensation problems on curvilinear surfaces for application inside advanced heat exchangers with enhanced surfaces.The evaporation of self-rewetting fluids is another strand of research at MRC-ULB. Self-rewetting fluids are mixtures that exhibit an increasing surface tension with temperature and concentration. Since in the course of liquid/vapour phase change, self-rewetting fluids behaviour induces a rather strong liquid inflow (caused by both temperature and concentration gradients) from the cold region (where liquid condensates) to the hot evaporator region, several interesting applications may be envisaged, e.g. the development of advanced wickless heat pipes for utilization in reduced gravity environments.]

PRODEX SoDi: (Selectable Optical DIagnostics). Mesure de coefficient de diffusion et Soret. Prévu à la mi-2007 à bord de la Station Spatiale Internationale [PRODEX SoDi: (Selectable Optical DIagnostics) . Diffusion and Soret coefficient measurement to fly onboard ISS in mid-2007]
qui a été développée en partie grâce au soutien des SSTC dans le cadre d'un programme Prodex. [The SODI facility for the MSG is a 2-wavelength Mach Zehnder Interferometer set-up and a thermal conditioner for liquid cells. It is designed to enable measurements diffusion coefficients in liquid mixtures, primarily crude oils. Thermodiffusion (Soret) coefficients will be measured by applying a thermal gradient to the cell; when relaxing the temperature gradient, one can then also measure isothermal diffusion. The set-up is designed to enable exchange of the cell in the conditioner and thereby, other experiments that can make use of the capabilities. The design will enable to mount the cell conditioner on a system generating low frequency vibrations so as to quantify their influence on the diffusion process (project IVIDIL: Influence of VIbration stimuli on DIffusion in Liquids).]



theses


Van Vaerenbergh Stefan (1992), ''Mesure du coefficient Soret et étude de son rôle dans les phénomènes interfaciaux y compris au voisinage d'un front de cristallisation'', Dir. Prof. J.C. Legros, Service de Chimie physique E.P., ULB, Bruxelles., 1992



prix


COSPAR Zeldovich'Award



disciplines et mots clés déclarés


Instrumentation et méthodes en physique Mécanique des fluides Physique de l'état condense [struct., propr. thermiques, etc.] Rayonnement cohérent et holographie Thermodynamique et thermochimie [physique]

agence spatiale européenne (esa) Agence Spatiale Européenne (ESA) coefficient Soret diagnostic optique diagnostics optiques diffusion diffusion ternaire fontainebleau benchmark heat laboratoire de physique des fluides laboratoire orbital microgravité selene thermodiffusion