Measurement of Flow Rate of Droplets and Liquid Film in Venturi Scrubber

As one of filtered venting systems which should be installed in light water reactors from viewpoint of protecting a containment vessel and suppressing the diffusion of radioactive materials, there is a system composed of venturi scrubbers. The radioactive materials in the contaminated gas are collected into liquid. By dispersed flow formed in the venturi scrubber, large interfacial area between liquid and gas was obtained, and large decontamination factor is realized. In evaluation for the decontamination performance of the venturi scrubber, interface of droplets and liquid film are important. However, there is a little knowledge about the interfacial area in the venturi scrubber for filtered venting. In this study, to obtain the interfacial area data, amount of the droplets and the liquid film in the venturi scrubber is evaluated by visualizing observation and sampling the liquid film at the outlet of the venturi scrubber. In the venturi scrubber, a pressure drop occurs in the throat part by the inflow of air from the compressor. Water flows from the tank by a pressure difference between a suctioned hole with head pressure and a throat part. An annular spray flow is then formed in the venturi scrubber. Therefore, the liquid flow rate changes according to the gas phase flow rate. To discharge separately the droplets and the liquid film, a rectangular separator is installed at the venturi scrubber outlet. The superficial gas phase flow rate is 25.2–292.3 m/s in the throat. As a result, the liquid film and the droplets through the wall were confirmed to be discharged separately by the separator. The ratio of the liquid film to the total amount of liquid is 80 to 95% and that of the droplets was estimated as 5 to 20%. However, the change of the liquid film thickness caused by the increase of gas phase flow rates was observed. When the liquid film thickness is large, it is possible that some liquid film flowing into the droplet side.

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Measurement of Liquid Film Thickness in Micro Tube Annular Flow

2010 14th International Heat Transfer Conference, Volume 6 ◽

10.1115/ihtc14-23176 ◽

2010 ◽

Cited By ~ 1

Author(s):

Hiroshi Kanno ◽

Youngbae Han ◽

Yusuke Saito ◽

Naoki Shikazono

Keyword(s):

Heat Transfer ◽

Film Thickness ◽

Liquid Film ◽

Annular Flow ◽

Liquid Film Thickness ◽

Phase Flow ◽

Two Phase ◽

Micro Scale ◽

Film Model ◽

Annular Film

Heat transfer in micro scale two-phase flow attracts large attention since it can achieve large heat transfer area per density. At high quality, annular flow becomes one of the major flow regimes in micro two-phase flow. Heat is transferred by evaporation or condensation of the liquid film, which are the dominant mechanisms of micro scale heat transfer. Therefore, liquid film thickness is one of the most important parameters in modeling the phenomena. In macro tubes, large numbers of researches have been conducted to investigate the liquid film thickness. However, in micro tubes, quantitative information for the annular liquid film thickness is still limited. In the present study, annular liquid film thickness is measured using a confocal method, which is used in the previous study [1, 2]. Glass tubes with inner diameters of 0.3, 0.5 and 1.0 mm are used. Degassed water and FC40 are used as working fluids, and the total mass flux is varied from G = 100 to 500 kg/m2s. Liquid film thickness is measured by laser confocal displacement meter (LCDM), and the liquid-gas interface profile is observed by a high-speed camera. Mean liquid film thickness is then plotted against quality for different flow rates and tube diameters. Mean thickness data is compared with the smooth annular film model of Revellin et al. [3]. Annular film model predictions overestimated the experimental values especially at low quality. It is considered that this overestimation is attributed to the disturbances caused by the interface ripples.

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Liquid Film Thickness in Micro-Scale Two-Phase Flow

Two Phase Flow, Phase Change and Numerical Modeling ◽

10.5772/22394 ◽

2011 ◽

Cited By ~ 3

Author(s):

Naoki Shikazono ◽

Youngbae H

Keyword(s):

Film Thickness ◽

Liquid Film ◽

Two Phase Flow ◽

Liquid Film Thickness ◽

Phase Flow ◽

Two Phase ◽

Micro Scale

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ANALYSIS OF INTERFACIAL AND MASS TRANSFER EFFECTS ON FORCED CONVECTION IN GAS-LIQUID ANNULAR TWO-PHASE FLOW

Revista de Engenharia Térmica ◽

10.5380/reterm.v3i1.3483 ◽

2004 ◽

Vol 3 (1) ◽

pp. 45

Author(s):

E. Nogueira ◽

B. D. Dantas ◽

R. M. Cotta

Keyword(s):

Heat Transfer ◽

Mass Transfer ◽

Film Thickness ◽

Liquid Film ◽

Liquid Film Thickness ◽

Phase Flow ◽

Transfer Effects ◽

Two Phase ◽

Transfer Rates ◽

Interface Waves

In a gas-liquid annular two-phase flow one of the main factors influencing the determination of heat transfer rates is the average thickness of the liquid film. A model to accurately represent the heat transfer in such situations has to be able of determining the average liquid film thickness to within a reasonable accuracy. A typical physical aspect in gas-liquid annular flows is the appearance of interface waves, which affect heat, mass and momentum transfers. Existing models implicitly consider the wave effects in the momentum transfer by an empirical correlation for the interfacial friction factor. However, this procedure does not point out the difference between interface waves and the natural turbulent effects of the system. In the present work, the wave and mass transfer effects in the theoretical estimation of average liquid film thickness are analyzed, in comparison to a model that does not explicitly include these effects, as applied to the prediction of heat transfer rates in a thermally developing flow situation.

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