Characteristics Of Gas-liquid Two-phase Flow Research Articles

The flow characteristics of an upward gas‐liquid two‐phase flow in a vertical tube with a wire coil: Part 2. Effect on void fraction and liquid film thickness

AbstractAn experimental study has been carried out to clarify the characteristics of the void fraction and the liquid film thickness of the air‐water two‐phase flow in vertical tubes of 25‐mm inside diameter with wire coils of varying wire diameter and pitch. The flow pattern in the experiment on the average void fraction and the local void fraction distribution in cross section was a bubble flow, and the liquid film thickness was in the region of semiannular and annular flows. It is clarified from these experiments that the average void fraction in tubes with wire coils is lower than that in a smooth tube and decreases with the wire diameter owing to the centrifugal force of the swirl flow which concentrates bubbles at the center of the tube, that the local liquid film thickness becomes more uniform with a decrease in the pitch of the wire coil, and that the liquid film becomes thicker after the passage through the wire coil with an increase in the wire diameter. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 652–664, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10067

B163 細管内気液二相流の特性を利用した液体輸送における圧力損失の検討

B163 細管内気液二相流の特性を利用した液体輸送における圧力損失の検討

415 垂直細管内気液二相流における液体物性の影響 : 第二報, 摩擦損失と界面摩擦力(O.S.4-4 混相流)(O.S.4 : 高度化に向けた流体関連解析と機器開発)

415 垂直細管内気液二相流における液体物性の影響 : 第二報, 摩擦損失と界面摩擦力(O.S.4-4 混相流)(O.S.4 : 高度化に向けた流体関連解析と機器開発)

437中性子ラジオグラフィによる液体金属-ガス二相流の液相速度計測

In a core melt accident of a fast breeder reactor, a possibility of re-criticality is anticipated in the molten fuel-steel mixture pool. One of the mechanisms to suppress the re-criticality is the boiling of steel in the molten fuel-steel mixture pool because of the negative void reactivity effect. To evaluate the reactivity change due to boiling, it is necessary to know the characteristics of gas-liquid two-phase flow in the molten fuel-steel mixture pool. For this purpose, boiling bubbles in a molten fuel-steel mixture pool were simulated by adiabatic gas bubbles in a liquid metal pool to study the basic characteristics of gas-liquid metal two-phase mixture. Visualization of the two-phase mixture and measurements of liquid phase velocity and void fraction were conducted by using neutron radiography and image processing techniques. From these measurements, the basic characteristics of gas-liquid metal two-phase mixture were clarified.

Flow Characteristics of Upward Gas-Liquid Two-Phase Flow in a Vertical Tube with a Wire Coil. 1st Report. Experimental Results of Flow Pattern, Void Fraction and Pressure Drop.

Experiments were carried out to investigate the flow pattern, average void fraction, and pressure drop of upward air-water two-phase flow in vertical tubes of 25 mm inside diameter with wire coils fo varying wire diameter, pitch and number of coil. Five kinds of flow patterns, i.e., bubble, slug, churn, semi-annular and annular flow, were defined based on the observation of flow behaviors in the experiments. At higher water flow rate, the bubble-slug transition occurred at a lower air flow rate in tubes with wire coil than in the smooth tube. The average void fraction was clarified using the drift flux model. Furthermore, the experimental results of the friction pressure drop were compared with the Lockhart-Martinelli correlation. As a result, a correlation for the constant C in Chisholm's equation was obtained as a function of wire coil pitch-to-diameter ratio.

Flow Characteristics of Upward Gas-Liquid Two-Phase Flow in a Vertical Tube with a Wire Coil. 2nd Report. Effect on Void Fraction and Liquid Film Thickness.

An experimental study has been carried out to clarify the characteristics of the void fraction and liquid film thickness of air-water two-phase flow in vertical tubes of 25 mm inside diameter with wire coil of varying wire diameter and pitch. Flow pattern in the experiment of average void fraction and local void fractrion distribution in a cross section is bubble flow, and liquid film thickness is in the region of semi-annular and annular flow. It is clarified from these experiments that the average void fraction in tubes with a wire coil is lower than that of the smooth tube and decreases with the wire diameter owing to the centrifugal force of swirl flow which concentrates bubbles at the center of the tube, and the liquid film thickness between the wire coil is uniformed with the decrease of the pitch of wire coil and that liquid film becomes thicker after the passage of wire coil with the increase of the wire diameter.

大深度エアリフトポンプにおける非定常気液二相流動の数値シミュレーション

It is anticipated that dynamical responses to changes of air supply become more complicated in a large-scale air-lift pump. Then it is inevitable to grasp unsteady flow characteristics in air-lift pumps for safety operations of the systems. Therefore the purposes of this study are to obtain safety operational conditions for air-lift pumps of lifting marine mineral resources such as manganese nodules from deep-sea floor to a mining ship. The numerical method was applied to an air-lift pump of 5,000 m depth. In this paper, we discuss especially the unsteady flow characteristics of gas-liquid two-phase flow in beginning and increasing of air supply, in increasing and reducing of back-pressure, and in stopping of air supply.

Numerical Analysis on Two-Phase Flow Characteristics of Liquid Nitrogen.

Gas liquid two-phase flow characteristics in a pipe flow of liquid nitrogen are numerically investigated. Firstly, the government equations on two-phase flow of liquid nitrogen based on the unsteady drift-flux model are presented and several characteristics are numerically calculated taking into consideration the effect of cryogenic flow state. It is found that phase change of liquid nitrogen occurs in quite short time interval compared with that of pressurized water in high temperature. Next, it is clarified that the pressure wave in two-phase flow forms strongly steep shape with the time progress because of the nonlinearity based on a compressibility of cryogenic two-phase mixture. According to these theoretical results, it seems reasonable to predict the fundamental characteristics of cryogenic two-phase flow, and the obtained numerical results would contribute to advanced cryogenic engineering applications.

Flow Characteristics of Gas-Liquid Two-Phase Annular Flow under Microgravity. (Experimental Results Utilizing a Drop Tower).

In order to predict various phenomena related to flow and heat transfer in space, it is necessary to carry out experiments under microgravity. The present work is concerned with the characteristics of gas-liquid two-phase annular flow under microgravity condition utilizing a drop tower. The experiments were carried out in a vertical transparent acrylic tube of 10.5 mm I.D. and 200 mm length, using a mixture of gaseous nitrogen (GN2) and water as the working fluid, in an annular flow region. The mean void fraction, pressure drop and liquid film thickness under microgravity were obtained and compared with the results of a ground test. It was found that the roughness of the liquid film surface was less and the mean liquid film thickness became greater under microgravity than under normal gravity

Characteristics of Gas-Liquid Two-Phase Flow in Rotating Pipe. 2nd Report. Pressure Characteristics in Downstream of the Entrance of Rotating Pipe.

In the present study, we report experimental results obtained from air-water two-phase flows in the downstream region of a rotating pipe which consists of three independent rotating parts with a total length of 3m. The pressure drop characteristics associated with the change in flow behavior due to effect of the pipe rotation are examined. Particular attention is paid to the length of the rotating pipe on the pressure drop characteristics. From the results of experiment, it is revealed that the effect of the rotating pipe becomes significant in the downstream of the entrance. A correlation based on the consideration of bubble fusion number applied to the bubble fusion model (proposed in the previous report) can be used to estimate the friction multiplication factor φL2 satisfactory in bubble flow and plug flow regimes for the developed rotating two-phase flows.

Flow Characteristics of Gas-Liquid Two-Phase Annular Flow under Microgravity. Experimental Results Utilizing a Drop Tower.

In order to predict various phenomena related to flow and heat transfer in space, it is necessary to carry out experiments under microgravity. The present work is concerned with the characteristics of gas-liquid two-phase annular flow under microgravity condition utilizing a drop tower. The experiments were carried out in a vertical transparent acrylic tube of 10.5 mm I.D. and 200 mm length, using a mixture of gaseous nitrogen (GN2) and water as the working fluid, in an annular flow region. The mean void fraction, pressure drop and liquid film thickness under microgravity were obtained and compared with the results of a ground test. It was found that the roughness of the liquid film surface was less and the mean liquid film thickness became greater under microgravity than under normal gravity.

Flow Characteristics of Gas-Liquid Two-Phase Flow under Microgravity. Experimental Results Utilizing Parabolic Trajectory Flights.

In order to predict various phenomena related to flow and heat transfer in space, it is necessary to carry out experiments under microgravity. The present report deals with the characteristics of a gas-liquid two-phase flow under microgravity utilizing parabolic trajectory flights. The experiment was carried out in a horizontal transparent acrylic resin tube of 10.5 mm I. D. and 500 mm length, using gaseous N2 and water as the working fluid, in a superficial gas velocity range of 0.025m/s to 4.6m/s and superficial water velocity range of 0.062m/s to 0.35m/s. The flow pattern, pressure drop and void fraction obtained in the microgravity experiment were compared with the results in the ground test, and also with other experimental results obtained under normal gravity. As a result, the two-phase frictional multiplier could be expressed by correlation of φ2L=1+16/X+1/X2 using the Martinelli parameter X.

Characteristics of gas-liquid two-phase flow in a capillary tube

Gas-liquid two-phase phenomena in capillary tubes were investigated with special attention on the flow patterns, the time varying void fraction and pressure loss. The directions of flow were vertical upward, horizontal and vertical downward. Pipe inner diameters used were 1 mm, 2.4 mm and 4.9 mm. As a result it is made clear that due to the strong effects of surface tension the flow pattern is not severely affected by the direction of flow, the smaller the pipe inner diameter, the easier the formation of liquid slug and the pressure loss in a unit length takes much larger than the estimated value by the Chisholm equation.

BASIC EQUATION OF TURBULENCE AND MODELING OF INTERFACIAL TRANSFER TERMS IN GAS-LIQUID TWO-PHASE FLOW

Abstract Turbulence is one of the most important phenomena in analyzing thermohydrodynamic characteristics of gas-liquid two-phase flow. For the purpose of accurate prediction of the turbulence phenomena, a basic conservation equation of Reynolds stress was derived based on the local instant formulation of mass and momentum conservations of two-phase flow. In this equation, interfacial transfer terms of turbulence appear as source terms. Detailed considerations on these transport terms were carried out. It was shown that they consist of a viscous damping term due to small scale interfacial structures, a drag induced turbulence generation term due to large scale interfacial structures and a term representing the exchange between surface energy and turbulence. Based on the mechanistic modeling and turbulence modulations, carried out were physical interpretations of interfacial area concentrations of small and large scale interfacial structures, a viscous damping term due to small scale interface and turbulence generation term due to large scale interface.

Recent developments of technology in magnetic fluid experiments

A review is presented of experimental studies of fluid mechanics of magnetic fluid conducted in Japan, especially at Tohoku University. The topics treated are pressure and local velocity measurement in a strong magnetic field and techniques for measuring the effect of a magnetic field on the optical and rheological properties of fluids that are closely related to particle aggregation in a fluid. Experimentation is difficult in magnetic fluid research because of the opaqueness of the fluid and the need to make measurements under an applied magnetic field. It is necessary to improve the methods of measuring pressure and local velocity and the visualization of particle behavior in such restricted conditions. Experimental techniques for the investigation of various pipe flow problems of magnetic fluids are also reviewed. First the effect of uniform and nonuniform magnetic fields on steady pipe flow is clarified. Then the gas-liquid two-phase flow and oscillatory flow characteristics in a pipe are investigated in the application of stationary and nonstationary magnetic flieds.

Fluctuation Characteristics of Gas-Liquid Two-Phase Flow and its Modeling.

Fluctuation Characteristics of Gas-Liquid Two-Phase Flow and its Modeling.

Characteristics of Counter current Gas-Liquid Two-Phase Flow in Vertical Tubes

Investigations into the flow pattern and the void fraction for countercurrent air-water flow in vertical tubes of diameter D = 40 and 80 mm were reported. The flow maps were presented and showed slug flow regime occupied larger portion on them. The void fraction was measured by the quick-closing valve technique, in bubbly and slug flow regime. The void fraction data available in the literatures as well as present work for counter- current flow in vertical tubes were correlated in terms of dimensionless groups. The experimental results of the present work were also compared with the drift flux model.

Characteristics of countercurrent gas-liquid two-phase flow in vertical tubes.

Investigations into the flow pattern and the void fraction for countercurrent air-water flow in vertical tubes of diameter D = 40 and 80 mm were reported. The flow maps were presented and showed slug flow regime occupied larger portion on them. The void fraction was measured by the quick-closing valve technique, in bubbly and slug flow regime. The void fraction data available in the literatures as well as present work for counter- current flow in vertical tubes were correlated in terms of dimensionless groups. The experimental results of the present work were also compared with the drift flux model.