Optical Measurement of Void Fraction and Bubble Size Distributions in a Microchannel

2006 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Optical Fibers ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Interface Velocity ◽  
Gas Velocity ◽  
Two Phase ◽  
Liquid Plug ◽  
Circular Microchannel ◽  
Superficial Gas Velocity

An optical measurement system was developed to investigate gas-liquid two-phase flow characteristics in a circular microchannel of 100 μm diameter. By using multiple optical fibers and infrared photodiodes, void fraction and gas plug and liquid plug lengths, and their velocities were measured successfully. The probes responded to the passage of gas and liquid phases through the microchannel adequately so that the time-average void fraction could be obtained from the time fraction for each phase. Also, by cross-correlating the signals from two neighboring probes, the interface velocity representing gas plug velocity or ring-film propagation velocity depending on the flow pattern could be computed. Within the ranges of superficial gas and liquid velocities covered in the experiments (jL = 0.2∼0.4 m/s and jG = 0 ∼ 5 m/s), the gas plug length was found to increase with the increasing superficial gas velocity, but the liquid plug length was found to decrease sharply as the superficial gas velocity was increased, so that the total length of the gas-liquid plug unit decreased with the superficial gas velocity.

Effect of Channel Length on the Gas-Liquid Two-Phase Flow Phenomena in a Microchannel

2009 ◽  
Author(s):  
Ryuji Kimura ◽  
Hideo Ide ◽  
Hiroshi Hashiguchi ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Test Section ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Liquid Velocity ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Plug ◽  
The Mean

An optical measurement system was used to investigate the effect of microchannel length on adiabatic gas-liquid two-phase flow characteristics. Experiments were conducted with 146 mm and 1,571 mm long, circular microchannels of 100 micron diameter. Two-phase flow patterns, void fraction, gas and liquid plug lengths and their velocities were measured for two inlet configurations and gas-liquid mixing, i.e., (a) reducer and (b) T-junction. The test section length was found to have a significant effect on the two-phase flow characteristics measured at the same axial location in the microchannel test section typified by the void fraction data. The mean void fraction data obtained in the shorter (146 mm) microchannel with the reducer inlet agreed well with the equation by Kawahara and Kawaji which was previously proposed. On the other hand, the mean void fraction obtained at 36 mm from the inlet in the longer (1,571 mm) microchannel corresponded well with the homogeneous flow model and Armand’s equation for both reducer and T-junction inlet configurations. In the present experimental ranges of superficial gas velocity, jG = 0.03 ∼ 14 m/s, and superficial liquid velocity, jL = 0.04∼0.7 m/s, the gas and liquid plugs obtained in the longer microchannel had relatively shorter lengths and higher velocities than those in the shorter channel. Thus, both the microchannel length and inlet geometry were found to affect the two-phase flow characteristics in a microchannel.

Effect of Void Fraction on Pressure Drop in Upward Vertical Two-Phase Gas-Liquid Pipe Flow

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Clement C. Tang ◽  
Sanjib Tiwari ◽  
Afshin J. Ghajar
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Void Fraction ◽  
Gas Velocity ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Fraction Increase ◽  
Superficial Gas Velocity ◽  
Two Parameters

Experimental data for the void fraction and two-phase frictional pressure drop from various sources has been compiled and analyzed. The experimental data revealed that at the lower range of superficial gas velocity and void fraction, the variations of the two-phase frictional pressure drop with superficial gas velocity and void fraction are relatively flat. However, as the superficial gas velocity and void fraction increase to higher values, the frictional pressure drop became significantly sensitive to the two parameters. In a situation when the two-phase pressure drop is sensitive to the variation of the void fraction, it is then that the proper and accurate characterization of the void fraction becomes significant. From the experimental data, regions where the pressure drop is sensitive to the variation of the void fraction are identified and evaluated.

Effect of Void Fraction on Pressure Drop in Upward Vertical Two-Phase Gas-Liquid Pipe Flow

2012 ◽  
Author(s):  
Clement C. Tang ◽  
Sanjib Tiwari ◽  
Afshin J. Ghajar
Keyword(s):  
Experimental Data ◽  
Pressure Drop ◽  
Void Fraction ◽  
Gas Velocity ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Fraction Increase ◽  
Superficial Gas Velocity ◽  
Two Parameters

Experimental data for void fraction and two-phase frictional pressure drop from various sources has been compiled and analyzed. The experimental data revealed that at lower range of superficial gas velocity and void fraction, the variations of two-phase frictional pressure drop with superficial gas velocity and void fraction are relatively flat. However, as superficial gas velocity and void fraction increase to higher values, the frictional pressure drop became significantly sensitive to the two parameters. In a situation when two-phase pressure drop is sensitive to the variation of void fraction, it is then that proper and accurate characterization of void fraction becomes significant. From the experimental data, regions where pressure drop is sensitive to the variation of void fraction are identified and evaluated.

Effect of Wetting on Adiabatic Gas-Liquid Two-Phase Flow in a Microchannel

2008 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Kazuki Inoue ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Video Camera ◽  
Internal Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Friction Pressure Drop ◽  
Sensor Signals

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in wetting and poorly wetting circular microchannels of 100 μm diameter. By examining the optical sensor signals from which void fraction and the lengths and velocities of gas slugs and liquid slugs were measured, the effects of wetting on the adiabatic two-phase flow characteristics of nitrogen gas and water were investigated. The data were obtained using a T-junction with the same internal diameter as the microchannel, but the T-junction itself was well wetting in both experiments. Besides the flat nose and tail of gas plugs/slugs at low gas and liquid flow rates, poorly wetting microchannel showed higher void fraction and friction pressure drop compared to the well-wetting microchannel. The poorly wetting microchannel also showed the presence of short and fast moving liquid slugs which were absent in well-wetting microchannel.

Effect of Channel Wetting Properties on Flow Characteristics of Gas-Liquid Two-Phase Flow in a Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Video Camera ◽  
Internal Diameter ◽  
Phase Flow ◽  
Two Phase ◽  
Wetting Properties ◽  
Friction Pressure Drop

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in wetting and poorly wetting circular microchannels of 100 μm diameter. By examining the optical sensor signals from which void fraction and the lengths and velocities of gas slugs and liquid slugs were measured, the effects of wetting on the adiabatic two-phase flow characteristics of nitrogen gas and water were investigated. The data were obtained using a T-junction with the same internal diameter as the microchannel, but the T-junction itself was well wetting in both experiments. Besides the flat nose and tail of gas slugs at low gas and liquid flow rates, poorly wetting microchannel showed higher void fraction and friction pressure drop compared to the well wetting microchannel. The poorly wetting microchannel also showed the presence of short and low moving liquid slugs which were absent in well-wetting microchannel.

An Experimental Study of Two-Phase Flow in a Tight Lattice Using Wire-Mesh Sensor

2020 ◽  
Author(s):  
Hengwei Zhang ◽  
Yao Xiao ◽  
Hanyang Gu
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Wire Mesh ◽  
Phase Flow ◽  
Gas Velocity ◽  
Two Phase ◽  
Fuel Bundle ◽  
Fraction Distribution ◽  
Superficial Gas Velocity ◽  
Tight Lattice

Abstract Tight lattice bundle can improve the conversion ratio and the heat transfer coefficient between the fuel bundle and the coolant, which is widely used in the innovative reactor fuel bundle design. The P/D ratio of a tight lattice bundle is usually less than 1.1, which is smaller than that of a conventional rod bundle. In the small-break loss-of-coolant accident (LOCA), the steam-water two-phase flow will occur in the reactor. The investigation of gas-liquid two-phase flow in the tight lattice is very important to the reactor safety analysis. A dual sub-channels tight lattice was designed in this study. The original reference of the channel is the annular fuel bundle, with the fuel diameter of 15.52mm, pitch of 16.51mm, P/D = 1.06. The original reference of working condition is the stream-water two-phase flow under the pressure of 15.5MPa. The experimental condition is the air-water two-phase flow at the normal temperature and pressure. According to the ratio of a critical bubble diameter in the reactor (steam-water) to that in atmospheric conditions (air-water), the channel is zoomed in 2.7 times. The diameter of the rod in the dual sub-channels tight lattice is 42mm and the pitch is 44.6mm. The total length of the dual sub-channels tight lattice is 3m. A self-developed 16 × 32 Wire-mesh sensor (WMS) was used to measure the void fraction distribution of air-water two-phase flow in the dual sub-channels tight lattice channel. The spatial resolution of the WMS is 2.79mm and the temporal resolution is 5000fps. The WMS was installed at a distance of 2.5m from the channel inlet and 0.5m from the outlet, which can avoid the influence of outlet on bubbles. The experimental range of flow condition is 0.921–1.84m/s for the superficial liquid velocity and 0.0884–1.07m/s for the superficial gas velocity. The instantaneous and time-averaged void fraction distributions in the channel was measured. With the increase of superficial gas velocity, the distribution of void fraction distribution changed from the wall peak to the core peak. The characteristics of bubbles in the sub-channel were also discussed in this study.

Effect of Inlet Geometry on Adiabatic Gas-Liquid Two-Phase Flow in a Microchannel

2007 ◽  
Author(s):  
Hideo Ide ◽  
Ryuji Kimura ◽  
Masahiro Kawaji
Keyword(s):  
Void Fraction ◽  
Two Phase Flow ◽  
Optical Measurement ◽  
Flow Characteristics ◽  
Internal Diameter ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Gas Volume ◽  
Compressible Gas

An optical measurement system and video camera were used to investigate gas-liquid two-phase flow characteristics in a circular microchannel of 100 μm diameter. By cross correlating the signals from two pairs of optical fibers and infrared photodiodes, void fraction and the lengths and velocities of gas slugs and liquid slugs were measured. The data were obtained using a T-junction with the same internal diameter as the microchannel but the lengths of the gas and liquid injection lines between the T-junction and flow control valves were quite different. The presence of a large compressible gas volume upstream of the T-junction had a significant effect on the two-phase flow characteristics in the microchannel, typified by the void fraction data. The two-phase flow characteristics in the absence of a compressible gas volume were analysed to obtain the liquid slug length and velocity data. The liquid slug velocity was found to be dependent on the slug length, since longer slugs experienced greater friction effects and moved with much slower velocities than the shorter liquid slugs.

scholarly journals Frictional Pressure Drop and Liquid Holdup of Churn Flow in Vertical Pipes with Different Viscosities

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Zilong Liu ◽  
Yubin Su ◽  
Ming Lu ◽  
Zilong Zheng ◽  
Ruiquan Liao
Keyword(s):  
Pressure Drop ◽  
Liquid Velocity ◽  
Gas Velocity ◽  
Liquid Holdup ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Viscous Oil ◽  
Predicted Values ◽  
Superficial Gas Velocity ◽  
Churn Flow

Churn flow commonly exists in the pipe of heavy oil, and the characteristics of churn flow should be widely understood. In this paper, we carried out air and viscous oil two-phase flow experiments, and the diameter of the test section is 60 mm. The viscosity range of the oil was 100~480 mPa·s. Based on the measured liquid holdup and pressure drop data of churn flow, it can be concluded that, due to the existence of liquid film backflow, positive and negative frictional pressure drop can be found and the change of frictional pressure drop with the superficial gas velocity is related to superficial liquid velocity. With the increase of viscosity, the change rate of frictional pressure drop increases with the increase of the superficial gas velocity. Combining our previous work and the Taitel model, we proposed a new pressure drop model for viscous oil-air two-phase churn flow in vertical pipes. By comparing the predicted values of existing models with the measured pressure drop data, the proposed model has better performance in predicting the pressure drop.

Flow Characteristics of Adiabatic Gas-Liquid Two-Phase Flow in a Horizontal Flat Rectangular Microchannel

2011 ◽  
Author(s):  
Hideo Ide ◽  
Kentaro Satonaka ◽  
Tohru Fukano
Keyword(s):  
Void Fraction ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Similar Data ◽  
Two Phase ◽  
The Mean

Experiments were performed to obtain, analyze and clarify the mean void fraction, the mean liquid holdup, and the liquid slug velocity and the air-water two-phase flow patterns in horizontal rectangular microchannels, with the dimensions equal to 1.0 mm width × 0.1 mm depth, and 1.0 mm width × 0.2 mm depth, respectively. The flow patterns such as bubble flow, slug flow and annular flow were observed. The microchannel data showed similar data patterns compared to those in minichannels with the width of 1∼10mm and the depth of 1mm which we had previously reported on. However, in a 1.0 × 0.1 mm microchannel, the mean holdup and the base film thickness in annular flow showed larger values because the effects of liquid viscosity and surface tension on the holdup and void fraction dominate. The remarkable flow characteristics of rivulet flow and the flow with a partial dry out of the channel inner wall were observed in slug flow and annular flow patterns in the microchannel of 0.1 mm depth.

Two-Phase Flow Through Square and Circular Microchannels—Effects of Channel Geometry

2004 ◽  
Vol 126 (4) ◽  
pp. 546-552 ◽  
Author(s):  
Peter M.-Y. Chung ◽  
Masahiro Kawaji ◽  
Akimaro Kawahara ◽  
Yuichi Shibata
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Channel Geometry ◽  
Frictional Pressure Drop ◽  
Channel Shape

An adiabatic experiment was conducted to investigate the effect of channel geometry on gas-liquid two-phase flow characteristics in horizontal microchannels. A water-nitrogen gas mixture was pumped through a 96 μm square microchannel and the resulting flow pattern, void fraction and frictional pressure drop data were compared with those previously reported by the authors for a 100 μm circular microchannel. The pressure drop data were best estimated using a separated-flow model and the void fraction increased non-linearly with volumetric quality, regardless of the channel shape. However, the flow maps exhibited transition boundaries that were shifted depending on the channel shape.

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