Ecoulements liquides en microtubes et ébullition convective en minicanaux : étude expérimentale et modélisation

摘要

The present study deals with two aspects of microfluidic: liquid flows in microtubes and flow boiling in minichannels. The experimental set-up and the data treatment method developed in the first part of the manuscript allow to obtain the Poiseuille number of a laminar liquid flows with a low uncertainty mostly below 4 %. The study evidence an increase of the Poiseuille number for tap water, distilled water and KCl solutions flows in microtubes diameters ranging from 540 to 52 µm. We propose an explanation for the observed gap to originate with the electrostatic coupling between the fluid which contains ions and the solid microtube surface which is charged (Electrical Double Layer theory). In the second part of the manuscript, we evidence the influence of confinement on flow boiling in an upward minichannel. Two types of flows are observed: steady ones characterized by classical flow patterns and unsteady ones due to an important vapour generation rate. We distinguish the coupling fluctuations from the confinement ones. A criterion allows proposing a non-dimensioned parameter. Scaling laws for the two phase flow and heat transfer are proposed.