scholarly journals Investigation of Flow Pattern and Void Fraction of Air and Low Surface Tension Liquid in A 30° Inclined Small Pipe

2021 ◽  
Vol 83 (2) ◽  
pp. 73-83
Author(s):  
Sudarja ◽  
Sukamta ◽  
Fauzan Saputra
Keyword(s):  
Surface Tension ◽  
Flow Pattern ◽  
Test Section ◽  
High Speed ◽  
Liquid Surface ◽  
Phase Flow ◽  
Distilled Water ◽  
Two Phase ◽  
Liquid Surface Tension ◽  
Churn Flow

Two-phase flow in the mini pipe is applied in wide fields. The most common of two-phase flow is a couple of gas and liquid. The essential properties of the liquid are density, viscosity, and surface tension. There are many variations of the flow direction, horizontal, incline, and vertical, in terms of orientation. The two-phase investigation of flow pattern and void fraction of air and low surface tension liquid in a 30° inclined small pipe has been carried out. Dry air was used as a gas phase, while the liquid was the mixture solution of distilled water and 3% (by volume) of butanol. Butanol addition aimed to decrease the surface tension, which became 42.9 millinewton/meter, instead of 71 mN/m when using distilled water. The test section was a 130 mm length, 1.6 mm inner diameter circular glass pipe. The rig used was equipped with the air compressor, pressure tank, high-speed camera, liquid flow meter, and gas flow meter. The liquid was fed to the test section by the pressurized tank, instead of directly pumped, to avoid pulsation. Ranges of gas and liquid superficial velocities were 0.025 – 66.3 m/s and 0.033 – 4,935 m/s, respectively. Flow patterns were obtained from the captured high-speed video. Meanwhile, the void fractions were acquired by image processing of the video. As a result, five distinctive flow patterns were observed: plug, slug-annular, churn, bubbly, and annular. The separated flow was absent. The change of the liquid surface tension affected the shifting of some transition boundary lines in the flow pattern map. The transition line between slug-annular and annular against churn flow was shifted to the lower side or toward lower JL when the liquid surface tension decreased. In short, the churn flow was easier to be formed when the liquid surface tension was lower.

Effect of Surface Tension on Flow Pattern in Counter-Current Gas-Liquid Two-Phase Flow in an Inclined Pipe

2004 ◽  
Vol 2004.42 (0) ◽  
pp. 369-370
Author(s):  
Deendarlianto ◽  
Masafumi Konishi ◽  
Akiharu Ousaka ◽  
Akira Kariyasaki ◽  
Koji Kusano
Keyword(s):  
Surface Tension ◽  
Flow Pattern ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Inclined Pipe ◽  
Counter Current ◽  
Effect Of Surface

An Experimental Study on Air-Water Two-Phase Flow Patterns in Pebble Beds

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Bai Bofeng ◽  
Liu Maolong ◽  
Su Wang ◽  
Zhang Xiaojie
Keyword(s):  
Experimental Study ◽  
Flow Pattern ◽  
Test Section ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition

An experimental study was conducted on the air-water two-phase flow patterns in the bed of rectangular cross sections containing spheres of regular distribution. Three kinds of glass spheres with different diameters (3 mm, 6 mm, and 8 mm) were used for the establishment of the test section. By means of visual observations of the two-phase flow through the test section, it was discovered that five different flow patterns occurred within the experimental parameter ranges, namely, bubbly flow, bubbly-slug flow, slug flow, slug-annular flow, and annular flow. A correlation for the bubble and slug diameter in the packed beds was proposed, which was an extended expression of the Tung/Dhir model, Jamialahmadi’s model, and Schmidt’s model. Three correlations were proposed to calculate the void friction of the flow pattern transition in bubble flow, slug flow, and annular flow based on the bubble model in the pore region. The experimental result showed that the modified Tung and Dhir model of the flow pattern transition was in better agreement with the experimental data compared with Tung and Dhir’s model.

Flow Pattern, Void Fraction and Pressure Drop During Adiabatic Two-Phase Gas-Liquid Flow in Vertical Micro-Channel

2012 ◽  
Author(s):  
Sira Saisorn ◽  
Somchai Wongwises
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Void Fraction ◽  
Test Section ◽  
Annular Flow ◽  
Fused Silica ◽  
Working Fluid ◽  
Micro Channel ◽  
Two Phase ◽  
Churn Flow

The experimental investigation is performed to study two-phase flow pattern, void fraction and pressure drop characteristics in a vertical micro-channel. The test section is a fused silica tube with a diameter of 0.53 mm and a length of 320 mm. Air and water are used as working fluid which is introduced to the test section in vertical upward direction. The test runs are done at superficial velocities of gas and liquid ranging respectively from 0.375 to 21.187 m/s and 0.004 to 2.436 m/s. Stereozoom microscope mounted together with camera are employed to conduct flow visualization from which slug flow, throat-annular flow, churn flow, annular flow and annular-rivulet flow are observed. Based on image analysis, void fraction data are obtained and found to be linear relationship with volumetric quality. The frictional pressure drop is relatively high when the formation of churn flow is established. Besides, the two-phase frictional multiplier is found to be strongly dependent on both mass flux and flow pattern.

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.

Two-Phase Flow Patterns in a Four by Four Rod Bundle

2006 ◽  
Author(s):  
Yoshitaka Mizutani ◽  
Shigeo Hosokawa ◽  
Akio Tomiyama
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Square Lattice ◽  
Phase Flow ◽  
Two Phase ◽  
Local Flow ◽  
Rod Bundle ◽  
Four Square

Air-water two-phase flow patterns in a four by four square lattice rod bundle consisting of an acrylic channel box of 68 mm in width and transparent rods of 12 mm in diameter were observed by utilizing a high speed video camera, FEP (fluorinated ethylene propylene) tubes for rods, and a fiberscope inserted in a rod. The FEP possesses the same refractive index as water, and thereby, whole flow patterns in the bundle and local flow patterns in subchannels were successfully visualized with little optical distortion. The ranges of liquid and gas volume fluxes, <JG> and <JL>, in the present experiments were 0.1 < <JL> < 2.0 m/s and 0.04 < <JG> < 8.85 m/s, which covered typical two-phase flow patterns appearing in a fuel bundle of a boiling water nuclear reactor. As a result, the following conclusions were obtained: (1) the region of slug flow in the <JG> – <JL> flow pattern diagram is so narrow that it can be regarded as a boundary between bubbly and churn flows, (2) the boundary between bubbly and churn flows is close to the boundary between bubbly and slug flows of the Mishima & Ishii’s flow pattern transition model, and (3) the boundary between churn and annular flows is well predicted by the Mishima & Ishii’s model.

Two-Phase Flow Excitation Forces on a Vertical U-Bend Tube

2011 ◽  
Author(s):  
M. Giraudeau ◽  
M. J. Pettigrew ◽  
N. W. Mureithi
Keyword(s):  
Flow Pattern ◽  
Two Phase Flow ◽  
Dominant Frequency ◽  
Tube Diameter ◽  
Curvature Radius ◽  
Phase Flow ◽  
Two Phase ◽  
Void Fractions ◽  
Two Parameters ◽  
Churn Flow

Significant two-phase flow-induced forces were previously measured on a 20 mm diameter U-tubes over a range of homogeneous void fractions. To investigate the effect of tube diameter, new experiments were conducted using vertical 52 mm diameter U-tubes. In the experiments, two parameters were varied, the homogeneous void fraction and the homogeneous velocity. All the results were compared with those for the smaller diameter tubes. The geometrical characteristics of the smaller diameter test sections are similar. L/D = 56 and the ratio of the bend curvature radius to inner diameter: R/D = 4. For all conditions tested, we compared the vertical upward flow-patterns for four different tube diameters. The observed flow regimes agreed relatively well with those predicted from two-phase flow pattern maps, except for the slug/churn transition. A specific two-phase flow pattern map is proposed for the 52 mm diameter tube, using a more accurate transition model from slug to churn flow. The forces comparison confirms the dependency with tube diameter. The RMS forces were found to increase with tube diameter for all void fractions studied. Conversely, the dominant frequency decreases with tube diameter, linearly for void fractions of 50 and 75%. Dimensionless forces and spectra for the smaller diameter tubes show good data collapse using the proposed model. Two-phase flows in the 52 mm diameter tube generate lower dimensionless spectra. Finally, a dimensionless model is proposed for practical application.

Wetting Effects on Two-Phase Flow in a Microchannel

2007 ◽  
Author(s):  
Alexandru Herescu ◽  
Jeffrey S. Allen
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Water Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Contact Angles ◽  
Phase Flow ◽  
Two Phase Flows ◽  
Two Phase ◽  
Number Systems

In the recent years there has been an increasing interest in the study of two-phase flows in low Bond number systems (where capillary forces are important relative to gravitational forces). Such systems include capillary tubes and microchannels as well as the gas flow channels of a PEM fuel cell. At the capillary scale, surface tension forces play an important role in two-phase flow regime transitions, pointing out the need to take into account the geometry of the cross section and the surface properties (wettability). Surface tension is generally considered in flow transitions, but the wetting properties of the fluid-surface material pairs (contact angle) are rarely given any importance. The researchers investigating two-phase flows should take extreme care when choosing the material of the test sections, as the flow morphology and the the pressure drop accordingly can vary widely with contact angle. In order to show these morphological changes high speed visualization experiments of air-water flow through 500 μm square and round microchannels were conducted. For the round channels, contact angles of less than 20° (wetting) and 105° (non-wetting) were investigated. For the square section, things are complicated by the presence of the corners. According to the Concus-Finn criterion, the liquid will wick into (wet) the corner if the contact angle is less then 45°, or will de-wet the corner if the contact angle is above 45°. A new case not previously mentioned in the literature arises for a contact angle of 45° ≤ θ ≤ 90°, for which the liquid is wetting the walls but dewetting the corners. Three contact angles of less than 20°, 80° and 105° are considered to investigate the possible morphologies in the square geometry. Images aquired with a high speed camera depicting the different flow morphologies that exist at the same air-water flow rates for each of the considered contact angle and geometry are presented.

Micro-Scale Flow Pattern Classification Based on the K-Means Clustering Algorithm

2010 ◽  
Author(s):  
Daniel Sempe´rtegui ◽  
Gherhardt Ribastki
Keyword(s):  
Flow Pattern ◽  
High Speed ◽  
Clustering Algorithm ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Flow Patterns ◽  
Statistical Characteristics ◽  
Phase Flow ◽  
Two Phase

In the present work, an objective method to characterize two-phase flow pattern was developed and implemented. The method is based on the characteristics of the signals provided by transducers measuring local temperature and pressure plus the intensity of a laser beam crossing the two-phase flow. The statistical characteristics of these signals were used as input features for the k-means clustering method. In order to implement the method, experimental flow patterns were obtained during flow boiling of R245fa in a 2.32 mm ID tube. Experiments were performed for mass velocities from 100 to 700kg/m2s, saturation temperature of 31 °C and vapor qualities up to 0.99. The cluster classification was compared against flow patterns segregated based on high speed camera images (8000 images/s) and a reasonable agreement was obtained.

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