Experimental Investigation of Bubble Formation in Micro-devices

Nicolas Dietrich (1) , Souhila Poncin (1) , Huai-Zhi Li (1)

1 LSGC - Laboratoire des Sciences du Génie Chimique

The multiphase flows (gas-liquid-solid) in Newtonian and non-Newtonian fluids are involved in many industrial processes. Among these processes we can mention polymer devolatization, bubble columns, cosmetics, petrochemical, water treatment and bioprocesses. These systems are generally accompanied by heat and mass transfer as well as chemical reactions. In this context, the effectiveness of the heat and mass transfers is a main parameter that depends primarily on the nature of the gas-liquid or solid-liquid interfaces. In addition, some reactions, such as the fluorination of toluene are very dangerous and difficult to achieve at a large scale. Thus the realization of this kind of reactions in microsystems is much more safe and effective. That is why over the past few years, many studies (van Batten et al., 2004) and Garstecki et al., 2006) focused on the application of these processes at smaller scales, ranging from one hundred micrometers to a millimeter, leading to the emergence of gas-liquid micro-reactors. In the past, several studies have been focused on certain aspects of these flows, particularly the exchange of mass and pressure differences, but most of these studies are numerical and very few experimental studies have been conducted yet. The objective of this study is to compare micromixers of different sizes (channel size of 500, 800 and 1000 7m) and geometries (Y-junction, T-junction, cross section). In order to understand the mechanism of bubble formation, different gas and liquid flow rates, liquid viscosities and surface tensions were used. A High speed camera (10 000 images/second) and also a system of micro-Particle Image Velocimetry (7-PIV) were also used to measure the velocity flow field at micro-scale as shown in Figure 1. A correlation is proposed to estimate the bubble size for the different micromixers. This paper contributes to an original improvement in the domain where a few flow field characterisation and micro mixers comparisons have been published in the literature.

Mots clés: bubble formation; micromixer; flow focusing; correlation; µ-PIV

Domaines: Génie des procédés

Nicolas Dietrich, Souhila Poncin, Huai-Zhi Li. Experimental Investigation of Bubble Formation in Micro-devices. CHISA 2008, 2008, Czech Republic. pp.CHISA 2008. ⟨hal-00366044⟩