INFORMATIVO ABCM Nº 042/08 –– Pós-Doutorado na Universidade de Delft, Holanda

Department of Multi-Scale Physics
Two-phase flow with low liquid loading
Post-doc Vacancy (12 to 24 months)

Job Profile

For this Post-doc position we are looking for an enthusiastic team player. The candidate should have a PhD degree in Multiphase Flow, with a strong drive for performing research involving both experiments and modelling.

The candidate should have a keen eye for technology transfer of his results to practice. He must be capable to present the progress of his work to a user committee of engineers from industry.

The monthly starting salary is € 2,852 (based on a full-time employment and depending on experience). Benefits and other employment conditions are in accordance with the Collective Labour Agreement for Dutch Universities.

Contact

Candidates are advised to contact the supervisors, Profs. René V.A. Oliemans and Rob F. Mudde via Applicants-MSP-TNW@TUDelft.nl for more information or for sending their application.

Background

Two-phase gas/liquid flow with low liquid loading in both vertical and horizontal pipes is characterized by a wavy liquid film at the pipe wall and droplets in the gas core, called mist-annular flow in a vertical pipe and mist-stratified flow in horizontal pipes. The transport of the liquid mass comes mainly from the droplet mass flux due to the high droplet velocity. The droplet generation is governed by entrainment at the gas-liquid interface, which is related to the interface behaviour. In steady-state flow, entrainment and droplet deposition are in equilibrium, resulting in an entrained fraction in the gas phase, as droplets. The fluid dynamics of liquid film flow is also of importance in determining the frictional pressure gradient in the pipeline. In particular, the interfacial transfer of momentum may result from both interfacial shear stress (as in stratified flow) and momentum transfer related to mass transfer associated with droplets impinging on and accelerating from the film. The correct prediction of liquid holdup and pressure gradient in the low liquid loading system is crucial for the operation of long-distance gas pipeline.

In a vertical pipe orientation, the flow may experience co-current or counter-current two-phase flow, depending on the gas flow rate. In both cases, the liquid film is thin and wavy, and the wave movement may be the main contribution to the mass flow rate in the liquid film, while the wave dynamics determines the droplet entrainment. The wall friction is a complicated function of the wave characteristics and the mean film thickness. Traditionally, the wall friction is calculated on the basis of the mean liquid velocity and the film thickness, which may not be valid in this case. Especially, when the liquid film flow experiences back-flow (counter-current two-phase flow), the local circulation of the liquid mass makes the flow pattern complicated and difficult to describe in a simple way.

A similar picture can be observed in slightly-inclined upward flow with low liquid loadings, the correct description of both wall friction of liquid film and droplet entrainment rate needs the understanding of the wavy liquid flow. The characteristics of the liquid wavy film flow are crucial to develop the physical models which respect the scale and the effect of physical properties on the flow dynamics. These physics will be the basis for the development of the closure law for one-dimensional simulation widely used in the industry.

The project is sponsored by TOTAL (contact person: Alexandre Goldszal) and will receive technical support from SINTEF (Zhi Lin Yang), TOTAL (Dominique Larrey, Erich Zakarian), and INSA-Toulouse (Prof. Alain Liné, consultant for TOTAL for the LEDA project). TU Delft supervision by Prof. René Oliemans and Prof. Rob Mudde.

Research Scope

The objectives of the project is to explore the physical mechanism of droplet entrainment and deposition in the flow of low liquid loading where back flow may exist, and to develop the physical models describing the liquid film flow. The project involves both experiments and modelling.

The measurement should include: frictional pressure gradient, average liquid hold-up, droplet concentration, size and spatial distribution, liquid film thickness and its dynamics, local turbulence and mean velocity.

The modelling work will be based on an adapted two-fluid approach, and will focus on the development of models for the wavy liquid film. From the theoretical studies, one should be able to describe the flow in a one dimensional framework, including droplet entrainment, hold-up and wall and interfacial frictions. The physical models developed from the theoretical work should be validated by the experimental data

The methodology used in the theoretical models should be generic, so that they can apply for both vertical and inclined pipes