Document Type : Special Issue Manuscripts
University of Valenciennes / TEMPO
Polytechnic University Hauts-de-France of Valenciennes, LAMIH UMR CNRS 8201, France
Nowdays, we face important energy challenges. These ones are making scientist all over the world reconsider the way they look into problem and find innovative solutions to improve industrial processes efficiency. One of many original ideas is the use of “not-regular” fluids over regular applications. Aqueous Foam Flow present several unusual rheological properties when put inside a horizontal channel: low density, visco-elasto-plastic behaviour, and high wall shear stress. These ones give this type of fluid interesting capacities and uses: Assisted oil extraction, heat exchange, lubrication. In this study we undertake the causes of these interesting properties, which are directly related to the liquid slip-layer located between the flowing bubbles and the walls. For different velocities (2 cm/s, 4 cm/s and 6 cm/s) and void fractions (from 55% to 85%) we will study the influence of the liquid film thickness over the wall shear stress, using innovative measurement techniques: conductimetry and polarographic methods. An interesting relationship is seen between the limit diffusion current, required to accurately utilize the polarographic method, the wall shear stress and the liquid film thickness. The bubbles passage over the walls generates an oscillation of the slip-layer thickness which directly affects the polarographic results. However, as we increase the foams velocity this influence diminish and the wall shear stress calculations are more accurate.