Experiments have been conducted on countercurrent flow of air and water in tubes of 25, 67 and 99 mm diameter. Measurements of the pressure gradient, film thickness and down flow rate were made for a range of air and water flow rates under pre- and post-flooding conditions. The data showed that the pressure gradient did not increase appreciably until just before the onset of flooding. The mean film thickness under pre-flooding conditions was also predicted well by the falling film correlations. However, both quantities showed significant deviations from this pattern under post-flooding conditions. Existing correlations for predicting the pressure drop under post-flooding conditions gave poor prediction of the present data as well of the data from the literature. New correlations are presented for the pressure gradient and the mean film thickness under post-flooding conditions. © 2001 Published by Elsevier Science Ltd.

Sreenivas Jayanti

Department Of Chemical Engineering

M. Vijayan

Arcot R. Balakrishnan

Correlation methods

Flow patterns

Pressure effects

Water

ANNULAR FLOW

Airflow

COUNTERCURRENT FLOW

Fluid flow

pressure gradient

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Experimental study of air–water countercurrent annular flow under post-flooding conditions

International Journal of Multiphase Flow

AIChE Journal

On axial coherence of interfacial waves in countercurrent flow

This paper describes an experimental study on the effect of tube diameter on the mechanism of flooding in vertical gas-liquid countercurrent annular flow. Flooding experiments were conducted with three different tube inner diameters, namely, 25, 67 and 99 mm with smooth inlet and outlet conditions for air and water. The results indicate that the mechanism of flooding is qualitatively different in the small and the large diameter test sections. While flooding in the 25 mm diameter section occurred essentially by the upward movement of large waves created near the liquid outlet, no such waves could be seen in the 67 and the 99 mm diameter test sections. Here, flooding occurred by droplet carryover or by an unstable, churn-like motion in the liquid film. The results are compared with existing correlations. The effect of test section length on flooding was also investigated. © 2001 Elsevier Science Ltd. All rights reserved.

Effect of tube diameter on flooding

Calculations have been performed using the CFDS-FLOW3D computational fluid dynamics code to determine the force exerted on a standing wave by gas flowing over it. It is found that the drag on the wave is mainly due to the pressure variation around it and that it is a strong function of the channel dimensions. Extension of these results to typical flooding conditions in countercurrent flow in vertical tubes shows that the gas velocity required to transport waves upwards increases significantly as the tube diameter increases. It is suggested therefore that the mechanism of flooding depends on the diameter of the tube and that flooding is induced by upward transport of waves from near the bottom of the tube in small diameter tubes whereas in large diameter tubes, it may occur due to entrainment and carryover of droplets near the liquid entry.

Theoretical investigation of the diameter effect on flooding in countercurrent flow

The hydrodynamics and heat transfer of thin film flow with a wavy interface has been studied using computational fluid dynamics techniques. The velocity and temperature fields are obtained for periodic laminar flow with an assumed interface shape. The effect of sinusoidal and solitary waves on the heat transfer across the film is investigated. It is shown that the overall heat transfer coefficient is determined mainly by conduction through the film, rather than by the recirculation, if any, under the waves. However, the presence of interfacial waves still enhances the heat transfer coefficient due, mainly, to the effective thinning of the film. Copyright © 1996 Elsevier Science Ltd.

International Journal of Heat and Mass Transfer

Hydrodynamics and heat transfer of wavy thin film flow

Electric Power Research Institute, High Sulfur Test Center report to the Steering Committee, March 1994. [Monthly report]

Experimental study of air-water countercurrent annular flow under post-flooding conditions

Journal	International Journal of Multiphase Flow
ISSN	03019322
Open Access	No