S0802-2-3 Effect of surface wettability on liquid film dryout in upward annular two-phase flow

This study is concerned with liquid film dynamics and stability of annular flow, which plays an important role in understanding film rupture and dryout in boiling heat transfer. The research work starts from designing and making a test facility which enables the visualization and measurement of liquid film dynamics. A confocal optical sensor is applied to track the evolution of film thickness. A horizontal rectangular channel made of glass is used as the test section. Deionized water and air are supplied into that channel in such a way that an initial stratified flow forms, with the liquid film on the bottom wall. The present study is focused on characterization of liquid film profile and dynamics in term of interfacial wave and shear force induced film rupture under adiabatic condition. Based on the experimental data and analysis, it is found that given a constant water flowrate, the average thickness of water film decreases with increasing air flowrate, while the interfacial wave of the two-phase flow is intensified. As the air flowrate reaches a critical value, a localized rupture of the water film occurs.

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Numerical Investigation of Two-Phase Flow Over Unglazed Plate Collector Covered With Porous Material of Wire Screen for Solar Water Heater Application

Journal of Solar Energy Engineering ◽

10.1115/1.4041737 ◽

2018 ◽

Vol 141 (3) ◽

Cited By ~ 1

Author(s):

T. Salameh ◽

Y. Zurigat ◽

A. Badran ◽

C. Ghenai ◽

M. El Haj Assad ◽

...

Keyword(s):

Surface Tension ◽

Porous Material ◽

Water Flow ◽

Two Phase Flow ◽

Volume Fraction ◽

Phase Flow ◽

Two Phase ◽

Solar Water ◽

Wire Screen ◽

Effect Of Surface

This paper presents three-dimensional numerical simulation results of the effect of surface tension on two-phase flow over unglazed collector covered with a wire screen. The homogenous model is used to simulate the flow with and without the effect of porous material of wire screen and surface tension. The Eulerian-Eulerian multiphase flow approach was used in this study. The phases are completely stratified, the interphase is well defined (free surface flow), and interphase transfer rate is very large. The liquid–solid interface, gas–liquid interface, and the volume fraction for both phases were considered as boundaries for this model. The results show that the use of porous material of wire screen will reduce the velocity of water flow and help the water flow to distribute evenly over unglazed plate collector. The possibility of forming any hot spot region on the surface was reduced. The water velocity with the effect of surface tension was found higher than the one without this effect, due to the extra momentum source added by surface tension in longitudinal direction. The use of porous material of wires assures an evenly distribution flow velocity over the inclined plate, therefore helps a net enhancement of heat transfer mechanism for unglazed solar water collector application.

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