Characterization of Two-Phase Flow Patterns in Small Round Tubes

2014 ◽  
Vol 525 ◽  
pp. 256-259
Author(s):  
Wen Peng Hong ◽  
Guo Qing Niu ◽  
Ming Liang Jin
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
High Speed Video ◽  
Video Systems ◽  
Small Tube

To investigate flow characteristics by high speed video systems, experimental study was conducted to gas-liquid two-phase flow in horizontal round small tube with diameter of 5.5 and 2.6 mm, the typical flow pattern images were obtained, but stratified flow of the conventional size horizontal channel had not been discovered. Gas and liquid superficial velocities range from 0.1 to 100 ms-1, and 0.01to 10.0 ms-1 respectively. Flow patterns for co-current flow of air-water mixtures in horizontal round tubes are determined by high-speed video analysis to develop flow regime maps and the transitions between these flow regimes. Comparisons with the relevant literatures show that diameter and surface tension effects play an important role in determining the flow patterns and transitions between them.

High Speed Imaging and Two-Phase Flow Patterns During Flow Boiling in a Single Microchannel

2008 ◽  
Author(s):  
Jacqueline Barber ◽  
Khellil Sefiane ◽  
David Brutin ◽  
Lounes Tadrist
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Pressure Sensors ◽  
Flow Patterns ◽  
Bubble Nucleation ◽  
Phase Flow ◽  
Vapour Bubble ◽  
Two Phase ◽  
Over Time

Boiling in microchannels remains elusive due to the lack of full understanding of the mechanisms involved. A powerful tool in achieving better comprehension of the mechanisms is detailed imaging and analysis of the two phase flow at a fundamental level. We induced boiling in a single microchannel geometry (hydraulic diameter 727 μm), using a refrigerant FC-72, to investigate several flow patterns. A transparent, metallic, conductive deposit has been developed on the exterior of rectangular microchannels, allowing simultaneous uniform heating and visualisation to be conducted. The data presented in this paper is for a particular case with a uniform heat flux of 4.26 kW/m2 applied to the microchannel and inlet liquid mass flowrate, held constant at 1.33×10−5 kg/s. In conjunction with obtaining high-speed images and videos, sensitive pressure sensors are used to record the pressure drop profiles across the microchannel over time. Bubble nucleation, growth and coalescence, as well as periodic slug flow, are observed in the test section. Phenomena are noted, such as the aspect ratio and Reynolds number of a vapour bubble, which are in turn correlated to the associated pressure drops over time. From analysis of our results, images and video sequences with the corresponding physical data obtained, it is possible to follow visually the nucleation and subsequent both ‘free’ and ‘confined’ growth of a vapour bubble over time.

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 Characteristics in a Co-Flow Induced Microchannel With Microbubbles Generation

2007 ◽  
Author(s):  
Sujin Yeom ◽  
Seung S. Lee ◽  
Sang Yong Lee
Keyword(s):  
Two Phase Flow ◽  
Flow Characteristics ◽  
Flow Patterns ◽  
Gas Pressure ◽  
Superficial Velocity ◽  
Working Fluid ◽  
Phase Flow ◽  
Two Phase ◽  
Gas Channel ◽  
Micro Bubble

This paper presents a micro-fluidic device which generates micro-bubbles, ranging from 70μm to 160μm in diameter, and two-phase flow characteristics in the device were tested. The device is composed of three sub-channels: a centered gas channel (10μm×50μm) and two liquid channels (both with 85μm×50μm) on each side of the gas channel. Micro-bubbles are generated by co-flow of gas and liquid at the exit of the gas channel when the drag force becomes larger than the surface tension force as bubbles grow. Methanol and a gas mixture of CO2 and N2 were used as the working fluid. Since the flow rate of gas was very small, the gas momentum effect was considered negligible. Thus, in the present case, the controlling parameters were the liquid superficial velocity and the inlet pressure of the gas. A high speed camera was used to record two-phase flow patterns and micro-bubbles of the device. To confine the ranges of the micro-bubbles generation, two-phase flow patterns in the device is observed at first. Four different flow patterns were observed: annular, annular-slug, slug, and bubbly flow. In bubbly flows, uniform-sized micro-bubbles were generated, and the operating ranges of the liquid superficial velocity and the gas pressure were below 0.132 m/s and 0.7 bar, respectively. Diameters of the micro-bubbles appeared smaller with the higher superficial liquid velocity and/or with a lower gas pressure. Experimental results showed that, with the gas pressure lower than a certain level, the sizes of micro-bubbles were almost insensitive to the gas pressure. In such a ranges, the micro-bubble diameters could be estimated from a drag coefficient correlation, CDw = 31330/Re3, which is different from the correlations for macro-channels due to a larger wall effect with the micro-channels. In the latter part of the paper, as a potential of application of the micro-bubble generator to gas analysis, dissolution behavior of the gas components into the liquid flow was examined. The result shows that the micro-bubble generator can be adopted as a component of miniaturized gas analyzers if a proper improvement could be made in controlling the bubble sizes effectively.

Characteristics of Gas-Liquid Two-Phase Flow Patterns in Miniature Channel Having a Gas Permeable Sidewall

2002 ◽  
Author(s):  
H. Yang ◽  
T. S. Zhao ◽  
P. Cheng
Keyword(s):  
Test Section ◽  
High Speed ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Porous Plate ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Configuration ◽  
Blowing Up

Characteristics of gas-liquid two-phase flow patterns in a miniature square cross-section channel having a gas permeable sidewall have been investigated visually using a high-speed motion analyzer. The problem under consideration is encountered in the design of Direct Feed Methanol Fuel Cells (DMFC). The test section was a horizontally oriented rectangular transparent (Lucite material) channel with its lower wall consisting of a porous plate. Liquid was fed into the test section from its entrance, while gas was injected uniformly into the test section along the lower porous sidewall. The visual study shows the typical flow patterns found in the test section include bubbly flow, plug flow, slug flow, and annular flow. However, unlike the conventional co-current two-phase flow in a channel with gas and liquid uniformly entering from one of its ends, for the flow configuration considered in this work, it was found that two or three of the above mentioned flow patterns appeared simultaneously at different locations of the channel. The length of each flow pattern varied with the flow rates of liquid and gas. A distinct feature of annular flow for the present flow configuration is that small bubbles were continuously generated from the porous plate, which grew by blowing up the liquid film, formed a semi-sphere shape, and then ruptured and released gas into the core flow.

scholarly journals Investigating the Characteristics of Two-Phase Flow Using Electrical Capacitance Tomography (ECT) for Three Pipe Orientations

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 51 ◽  
Author(s):  
Zeyad Almutairi ◽  
Fayez M. Al-Alweet ◽  
Yusif A. Alghamdi ◽  
Omar A. Almisned ◽  
Othman Y. Alothman
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Electrical Capacitance Tomography ◽  
Experimental Measurements ◽  
Phase Flow ◽  
Electrical Capacitance ◽  
Liquid Holdup ◽  
Two Phase ◽  
Capacitance Tomography

Experiments of gas–liquid flow in a circular pipe for horizontal and inclined positions (upward/downward) are reported. The characteristics of two-phase flow in terms of liquid holdup (ε(L)) and induced flow patterns are studied using three experimental techniques; time-averaged ε(L) from permittivity profiles using electrical capacitance tomography (ECT), instantaneous ε(L) using two fast-closing valves (TFCV), and high-speed camera images (HSCI) to capture/identify the formed flow patterns. Thus, this experimental setup enables the development of more well-defined flow patterns in gas–liquid two-phase flow and allows for multi-technique verification of the results. Taken from experimental measurements, a model is proposed to predict ε(L) for high and low situations. The correlations are a function of the hydrodynamic dimensionless quantities which provide hydrodynamic similarity. Regarding different pipe orientations, ε(L) predictions are comparable to ε(L) from experimental measurements with accepted accuracy: 88% of the predictions are within ±5–15% and 98% are below ±20%. The correlations also were validated by reported results and against correlations available in the literature and show higher prediction accuracy. It is confirmed that the kinematic similarity which is achieved by the gas–liquid velocity ratios and the inertial forces influence the flow pattern and the liquid holdup.

Numerical and experimental research on the erosion of solid-liquid two-phase flow in transport butterfly valve based on DEM method

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Benliang Xu ◽  
Zuchao Zhu ◽  
Zhe Lin ◽  
Dongrui Wang ◽  
Guangfei Ma
Keyword(s):  
Particle Size ◽  
Turbulence Model ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Characteristics ◽  
Phase Flow ◽  
Butterfly Valve ◽  
Two Phase ◽  
Content Type ◽  
Solid Liquid

Purpose The purpose of this paper is to analyze the mechanism of particle erosion in butterfly valve pipelines under hydraulic transportation conditions. The results will affect the sealing and safety of butterfly valve pipelines and hopefully serve as reference for the anti-erosion design of butterfly valve pipelines. Design/methodology/approach Through the discrete element method (DEM) simulation that considers the force between particles, the detached eddy simulation (DES) turbulence model based on realizable k-epsilon is used to simulate the solid-liquid two-phase flow-induced erosion condition when the butterfly valve is fully opened. The simulation is verified by building an experimental system correctness. The solid-liquid two-phase flow characteristics, particle distribution and erosion characteristics of the butterfly valve pipeline under transportation conditions are studied. Findings The addition of particles may enhance the high-speed area behind the valve. It first increases and then decreases with increasing particle size. With increasing particle size, the low-velocity particles change from being uniformly distributed in flow channel to first gathering in the front of the valve and, then, to gathering in lower part of it. Fluid stagnation at the left arc-shaped flange leads to the appearance of two high-speed belts in the channel. With increasing fluid velocity, high-speed belts gradually cover the entire valve surface by focusing on the upper and lower ends, resulting in the overall aggravation of erosion. Originality/value Considering the complexity of solid-liquid two-phase flow, this is the first time that the DEM method with added inter-particle forces and the DES turbulence model based on realizable k-epsilon has been used to study the flow characteristics and erosion mechanism of butterfly valves under fully open transportation conditions.

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