Characteristics of Two-Phase Flows in a Rectangular Microchannel With a T-Junction Type Gas-Liquid Mixer

In this study, gas-liquid two-phase flows in a horizontal rectangular microchannel have been investigated. The rectangular microchannel has the hydraulic diameter of 0.235 mm, and the width and the depth of 0.24 mm and 0.23 mm, respectively. A T-junction type gas-liquid mixer was used to introduce gas and liquid in the channel. In order to know the effects of liquid properties, distilled water, ethanol and HFE7200 were used as the test liquids, while nitrogen gas as the test gas. The flow pattern, the bubble length, the liquid slug length and the bubble velocity in two-phase flow were measured with a high speed video camera, and the void fraction was determined from the bubble velocity data and the superficial gas velocity data. In addition, the pressure drop was also measured with a calibrated differential pressure transducer. The bubble length data were compared with the calculation by the scaling law proposed by Garstecki et al (2006). The bubble velocity data and/or the void fraction data were well correlated with the well-known drift flux model (Zuber and Findlay, 1965) with a new distribution parameter correlation developed in this study. The frictional pressure drop data were also well correlated with Lockhart-Martinelli method with a correlation of two-phase friction multiplier.

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Investigation of Characteristics of Gas-Liquid Two-Phase Flows in a Rectangular Microchannel With Return Bends

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-10011 ◽

2011 ◽

Cited By ~ 2

Author(s):

Akimaro Kawahara ◽

Michio Sadatomi ◽

Hideki Matsuo ◽

Satoshi Shimokawa

Keyword(s):

Void Fraction ◽

Scaling Law ◽

Bubble Velocity ◽

Liquid Slug ◽

Two Phase Flows ◽

Two Phase ◽

Rectangular Microchannel ◽

Drift Flux Model ◽

Bubble Length ◽

Length Data

Gas-liquid two-phase flows in a horizontal rectangular microchannel with return bends have been investigated. The width and the depth of the microchannel are 240 μm and 230 μm, respectively. T-junction type gas-liquid mixer was used to introduce gas and liquid in the channel. In order to know the effects of liquid properties, distilled water, pure ethanol, 49wt% ethanol aqueous solution and HFE7200 were used as the test liquids, while nitrogen gas as the test gas. The flow pattern, the bubble velocity, the bubble length and the liquid slug length were measured, and the void fraction was determined as the ratio of the gas superficial velocity to the bubble velocity. The bubble velocity at a downstream position from the bend is faster than that at an upstream position, and thus the void fraction is smaller at a downstream position. The bubble velocity data were well correlated with the well-known drift flux model with Kawahara et al.’s distribution parameter correlation. The bubble length data at the upstream and the downstream positions are also correlated with the scaling law proposed by Garstecki et al., irrespective of the test liquids. The liquid slug length data are correlated with an exponential function of the void fraction. The ratio of the bubble length to the bubble pitch is also well correlated with a linear function of the homogeneous void fraction.

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OS8-05 Prediction of Subchannel Void Fraction and Pressure Drop of Two-Phase Flows in a Vertical 2×3 Rod Channel by a Two Fluid Model

The Proceedings of the National Symposium on Power and Energy Systems ◽

10.1299/jsmepes.2005.10.133 ◽

2005 ◽

Vol 2005.10 (0) ◽

pp. 133-134

Author(s):

Michio SADATOMI ◽

Keiko KANO ◽

Akimaro KAWAHARA ◽

Naoki MORI

Keyword(s):

Pressure Drop ◽

Void Fraction ◽

Fluid Model ◽

Two Phase Flows ◽

Two Phase ◽

Two Fluid Model ◽

Two Fluid

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Pressure Drop and Void Fraction in Steam-Water Two-Phase Flow at High Pressure

Journal of Heat Transfer ◽

10.1115/1.4023678 ◽

2013 ◽

Vol 135 (8) ◽

Cited By ~ 5

Author(s):

Wei Liu ◽

Hidesada Tamai ◽

Kazuyuki Takase

Keyword(s):

High Pressure ◽

Pressure Drop ◽

Void Fraction ◽

Two Phase Flow ◽

Water Pressure ◽

Homogeneous Model ◽

Test Fluid ◽

Phase Flow ◽

Two Phase ◽

Drift Flux Model

For a steam generator (SG) in a commercialized sodium-cooled fast breeder reactor (FBR), flow instability in the water side is one of the most important items needing research. As the first step of this research, thermal-hydraulic experiments using water as the test fluid were performed under high pressure conditions at the Japan Atomic Energy Agency (JAEA) by using a circular tube. Void fraction, pressure drop, and heat transfer coefficient data were obtained under 15, 17, and 18 MPa. This paper discusses the steam-water pressure drop and void fraction. Using the obtained data, we evaluated existing correlations for void fraction and two-phase flow multipliers under high pressure. As a result, the drift flux model implemented in the TRAC-BF1 code was confirmed to suitably predict the void fraction well under the present high pressure conditions. For the two-phase flow multiplier, the Chisholm correlation and the homogeneous model were confirmed to be the best under the present high-pressure conditions.

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Pressure Drop for Single- and Two-Phase Flows Through a Return Bend in Horizontal Rectangular Microchannel and Minichannel

ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2015-48721 ◽

2015 ◽

Author(s):

Akimaro Kawahara ◽

Michio Sadatomi ◽

Shinichi Miyagawa ◽

Mohamed H. Mansour

Keyword(s):

Pressure Drop ◽

Pressure Loss ◽

Single Phase ◽

Distribution Data ◽

Micro Channel ◽

Two Phase Flows ◽

Two Phase ◽

Rectangular Microchannel ◽

Frictional Pressure Drop ◽

Mini Channels

In this paper, single-phase liquid and two-phase gas-liquid pressure drop data through 180° return bends have been obtained for horizontal rectangular micro-channel and mini-channel. To investigate the size effects of the test channels, the hydraulic diameters were 0.25 mm and 3 mm respectively as the micro-channel and the mini-channel. The curvature radii of the bends were 0.500 mm and 0.875 mm for the micro-channel, while 6 mm for the mini-channel. To know liquid properties effects, distilled water, surfactant and glycerin aqueous solutions, ethanol and HFE (hydrofluoroether)-7200 were used as the test liquid, while nitrogen gas and air as the test gas. Pressure distributions upstream and downstream tangents of the bend were measured for the single-phase and the two-phase flows. From the pressure distribution data, the bend pressure loss was determined. By analyzing the present data, the bend loss coefficient for single-phase flow in both micro- and mini-channels could be correlated with Dean number. On the other side, the total bend pressure loss for two-phase flows were correlated by using an approach of Padilla et al., in which the total pressure loss is the sum of two pressure drop components, i.e., frictional pressure drop and singular pressure drop. The approach was found to be applicable to the present data for the micro- and the mini-channels if the frictional pressure drop was calculated by Lockhart-Martinelli method with Mishima & Hibiki’s correlation and Kawahara et al.’s correlation and the singular pressure drop was calculated by a newly developed empirical correlation.

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