Investigation of the liquid film thickness in an open-channel falling film micro-reactor by a stereo digital microscopy

Abstract

Abstract The film thickness is a vital parameter for the falling film micro-reactor (FFMR) as a characteristic value representing both the surface to volume ratio and the distance of mass and heat transfer. In this paper, a method and procedure using a stereo digital microscopy to study the flow pattern and liquid film thickness in the FFMR were developed. The hydrodynamic behaviors of three liquids (deionized water, ethanol and isopropanol) have been investigated in a customer designed FFMR. Studies suggest that the film thickness increases with increasing flowrate and viscosity. The viscous force plays a dominant role in the falling film process. The falling film behaviors were also analyzed by computational fluid dynamics (CFD) simulation. A new correlation for the film thickness prediction has been proposed, and its predictions are consistent with the experimental data from this work and public literatures with an accuracy of 7% and 20%, respectively. As a result, stereo digital microscopy has been proved to be an effective device for investigating the hydrodynamic behaviors in FFMR, and the proposed model can accurately predict the film thickness in falling film micro-system within a wide flow regime.