Numerical simulation of the descendent liquid film in a vertical tube

Abstract

Nowadays, it is impossible to have doubts that technology advances have been involved on the development of the humanity, including development of chemical engineering. For example, the computer invention and their increasing calculation power gave us the opportunity to solve more easily and quickly Transport Phenomena equations. These equations, which are the basis of Computational Fluid Dynamics (CFD), had been defined by Bird many years ago (1960), but during these days their solution required an computation power out the capabilities of the computers available at that time and it depended on the ability of the human. However, now we can use them easily to simulate fluid flow and to understand it better. In this project, the Mathematica 12.0 programming skill and the transport phenomena knowledge acquired during the degree is used to solve the mass and momentum conservation equations. With this knowledge, a recent article published by Hogxia Gao in the AlChE journal on 2018 has been reproduced. This article simulates the drop of a liquid film along a vertical tube of known dimensions. To reproduce it different models are implemented, for example a CFD model has been used to simulate the liquid film flow, by this way the film thickness and the hydrodynamics at the entry length have been predicted. The simulations are done using different liquids (distilled water / 40% water-sugar solution / 30% MEA-water solution) and different flowrates. Besides, its results have been compared with different symbolical models (two models based on Navier-Stokes equations and one based on an expression given by Bird to predict liquid film thickness along a vertical wall). and with experimental data from this reference. Hence, a total of four model has been implemented, each one of them has been applied in three mixtures to different flow rates, it means that more than 250 simulation have been done. The results of this project compared with the available experimental data show that the implemented CFD model programmed in Mathematica 12.0 predicts quite well the film thickness but not the hydrodynamics at the entry. Moreover, they are useful to understand and get an insight about how change the film flow depending on the liquid and on the flowrate used. In consequence, models to predict the hydrodynamics at the entry could be proposed on a future project