A study of film thickness and hydrodynamic entrance length in liquid laminar film flow along a vertical tube

Abstract

The liquid film thickness and hydrodynamic entrance length in a vertical tube was studied experimentally and numerically. Measurements using distilled water, 30 wt % MEA and 40 wt % sugar solutions were carried out to investigate the effects of liquid flow rate on the formation of the liquid film. The experimental results validate the new Navier-Stokes based equation in cylindrical coordinates (Eq. 16) and the volume of fluid (VOF) model giving a competitively high prediction of the liquid film thickness especially in the low Reynolds number region. In addition, a new empirical model and an improved minimal surface model have been first proposed for calculation of the hydrodynamic entrance length, with a relatively reasonable average absolute relative deviation (AARD) of 3.03% and 6.83%, respectively. Furthermore, the effects of the hydrodynamic entry length on the gas-liquid interfacial area calculated by the improved minimal surface model were comprehensively studied, and can be ignored if the ratio of the liquid film length (y) and the hydrodynamic entrance length (k E ) is lower than 10. However, it should be noted that the hydrodynamic entrance length cannot be ignored in packed columns in which the liquid flow is very complex due to the packings with different structures and materials.

Tow Deformation Behaviors in Resin-Impregnated Glass Fibers under Different Flow Rates

“…However, the change in tow thickness was not prominent near the inlet. The main reason for this is the hydrodynamic entry length, which is determined by the flow rate [30][31][32]. At different flow rates, flows in different amounts of fully developed regions could be observed.…”

Liquid jet impaction on the single‐layer stainless steel wire mesh in a rotating packed bed reactor

“…By high‐speed photography technology, the macro characters, that is, the liquid flow pattern, liquid disintegration modes, and liquid dispersion were investigated. Numerical simulation can be an supplementary tool to conveniently obtain the micro characters which is difficult to obtain by experiments . For example, Gao et al effectively studied the thickness of liquid film flowing along a vertical tube by CFD simulation.…”

“…Numerical simulation can be an supplementary tool to conveniently obtain the micro characters which is difficult to obtain by experiments. 12,13 For example, Gao et al 13 effectively studied the thickness of liquid film flowing along a vertical tube by CFD simulation. Via 3D numerical simulation, the dynamic liquid film flow and average liquid film thickness on the packing surface were both analyzed after the model validation.…”

Liquid water film on the outer surface of a half-submerged rotating drum

“…The surface in the current investigation is complex compared to a straight planner surface, 9 also here the effect of turbulence is not as simple laminar flow. 10 The absorption modeling 11,12 from the liquid film would be the next step to investigate using CFD. The partially submerged case makes it one-step complicated to model in terms of mixing.…”