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Belaud V.,Ecole Centrale Lyon | Valette S.,Ecole Centrale Lyon | Stremsdoerfer G.,Ecole Centrale Lyon | Bigerelle M.,French National Center for Scientific Research | And 2 more authors.
Tribology International

These authors experimentally investigate the influence of multi-scale roughness on contact angle measurements, and they propose a model combining the Wenzel and Cassie-Baxter equations with the 3D roughness parameters defined by ISO25178. To do this, a generic methodology based on a statistical method (bootstrap and correlation coefficient) is developed and applied to a polypropylene textured femtosecond laser (55 surfaces, ablation depths=5-45 μm and depth/diameter=0.07-0.53). A mixed model is proposed according to the correlations obtained between the contact angle of a plane surface, θ0, and a textured surface, θ, with the roughness parameters as the developed surface, Sdr, closed hills area, Sha and the closed dales area, Sda, with regard to the models of Wenzel and Cassie-Baxter. © 2014 Elsevier Ltd. Source

Deltombe R.,Laboratoire dAutomatique | Bigerelle M.,Laboratoire dAutomatique | Bigerelle M.,Laboratoire Of Thermique | Jourani A.,CNRS Roberval Laboratory (Mechanical Research Unit)
Surface Topography: Metrology and Properties

This study characterizes seal performance using a multiscale analysis of surface topography. The performance of two surface morphologies is compared: the first one is obtained with machining only and leads to leakage while the second one is obtained with machining and superfinishing and prevents leakage. It is shown that conventional roughness analysis does not enable to identify the differences between both surfaces. Only the use of a new parameter, the order parameter, and the use of a multiscale analysis of surfaces enable to distinguish the studied surfaces and to identify leakage causes. These causes are checked using a numerical contact simulation. It is shown that microroughness plays a major role in leakage. © 2016 IOP Publishing Ltd. Source

Dardour H.,University of Monastir | Mazouz S.,University of Monastir | Reneaume J.-M.,Laboratoire Of Thermique | Cezac P.,Laboratoire Of Thermique | And 2 more authors.
Applied Thermal Engineering

The performance of a heat-driven vapor absorption chiller with various alkane mixtures as working pairs was studied. A Thermodynamic analysis showed that under specified operating conditions and with a generator temperature below 130 ° C, temperature achievable with a simple flat plate collector when solar energy is expected as the driving heat source, the application of some of the proposed alkane mixtures is not feasible. Simulations using ASPEN Plus flow sheeting program are then done with the selected working pairs. All simulations were done specifying the Peng-Robinson equation of state as the property method. A parametric study was carried out allowing the investigation of the generator temperature effect on the system performance and the comparison between performances released with each working pair. Results revealed that a water-cooled absorption machine using the C3H8/n-C9H20 pair as working fluid releases the best performances from a heat driving temperature level of about 100 °C. © 2014 Elsevier Ltd. All rights reserved. Source

Saboni A.,Avenue Of Luniversite | Alexandrova S.,Laboratoire Of Thermique | Karsheva M.,University of Chemical Technology and Metallurgy of Sofia | Gourdon C.,ENSIACET
AIChE Journal

The unsteady mass transfer from a contaminated fluid sphere moving in an unbounded fluid is examined numerically for unsteady-state transfer. The effect of the interface contamination and the flow regime on the concentration profiles, inside and outside a fluid sphere, is investigated for different ranges of Reynolds number (0 < Re < 200) and Peclet number (0 < Pe < 105), viscosity ratio between the dispersed phase and the continuous phase (0 < κ < 10), and the stagnant-cap angle (0° < θcap < 180°). It was found that the stagnant-cap angle significantly influences the mass transfer from the sphere to a surrounding medium. For all Peclet and Reynolds numbers and κ, the contamination reduces the mass transfer flux. The average Sherwood number increases with an increase of stagnant-cap angle and reaches a maximum equal to the average one for a clean fluid sphere at low viscosity ratio and large Peclet numbers. A predictive equation for the Sherwood number is derived from these numerical results. © 2010 American Institute of Chemical Engineers (AIChE). Source

Saboni A.,Avenue Of Luniversite | Alexandrova S.,Laboratoire Of Thermique | Karsheva M.,University of Chemical Technology and Metallurgy of Sofia | Gourdon C.,ENSIACET
Chemical Engineering Science

A numerical study has been conducted to investigate the mass transfer inside a spherical bubble at low to moderate Reynolds numbers. The Navier-Stokes and diffusion-convection equations were solved numerically by a finite difference method. The effect of the bubble Schmidt number (over the range 0.1 Source

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