Dynamic film thickness between bubbles and wall in a narrow channel

Abstract

The present paper describes a novel technique to characterize the behavior of the liquid film between gas bubbles and the wall in a narrow channel. The method is based on the electrical conductance. Two liquid film sensors are installed on both opposite walls in a narrow rectangular channel. The liquid film thickness underneath the gas bubbles is recorded by the first sensor, while the void fraction information is obtained by measuring the conductance between the pair of opposite sensors. Both measurements are taken on a large two-dimensional domain and with a high speed. This makes it possible to obtain the two-dimensional distribution of the dynamic liquid film between the bubbles and the wall. In this study, this method was applied to an air-water flow ranging from bubbly to churn regimes in the narrow channel with a gap width of 1.5 mm.

Catalytic Hydrogenation of Nitrate over Immobilized Nanocatalysts in a Multi-Phase Continuous Reaction System: System Performance, Characterization and Optimization

“…Several aspects of the Taylor flow regime inside the macrostructured catalyst channels are significantly affected by the variations in the operating conditions of the system, namely the liquid and gas flow rates. There are different parameters that are responsible for the mass transfer rate inside the structured catalyst channels, such as liquid slug length, shape, and velocity, the gas bubble length, shape, and velocity (which is conditioned by the liquid velocity), the gas hold-up, pressure drop, recirculation of the liquid and gas inside the slugs, and the film thickness between the gas bubbles and the catalyst wall [65][66][67][68]. For the specific case of the present work, the mass transfer inside the monolith channels may be promoted by a higher total gas flow rate, which is why, even for lower H 2 flow rates, there is a slight increase in NO 3 − conversion when the CO 2 flow rate increases.…”