scholarly journals Boiling Synchronization in Two Parallel Minichannels—Image Analysis

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1409 ◽  
Author(s):  
Gabriela Rafałko ◽  
Iwona Zaborowska ◽  
Hubert Grzybowski ◽  
Romuald Mosdorf
Keyword(s):  
Image Analysis ◽  
Liquid Flow ◽  
Slug Flow ◽  
High Speed ◽  
Annular Flow ◽  
Bubble Flow ◽  
Phase Flow ◽  
High Speed Camera ◽  
Two Phase ◽  
Time Period

In this paper, the boiling synchronization of two-phase flow patterns in two parallel minichannels of 1 mm in diameter with connected compressible volumes was analyzed. The analysis was performed using images recorded with a high-speed camera. The degree of synchronization between channels was evaluated by assessing the presence of liquid flow in the small part of the minichannels. It can be concluded that boiling is synchronized when small bubble flow or wavy annular flow occur in neighboring channels. The occurrence of slug flow in one channel causes the boiling in neighboring channels to become unsynchronized. The result of the image analysis shows that the correlation coefficient based on the evaluation of the presence of liquid flow in the small part of the minichannels over a long enough time period allows for the detection of boiling synchronization.

scholarly journals Application of RQA and SOM for identification of two-phase flow patterns during boiling in horizontal minichannel

2021 ◽  
Vol 321 ◽  
pp. 02008
Author(s):  
Hubert Grzybowski ◽  
Iwona Zaborowska ◽  
Romuald Mosdorf
Keyword(s):  
Pressure Drop ◽  
Liquid Flow ◽  
Slug Flow ◽  
High Speed ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Inner Diameter

In the paper, numerical methods of data analysis recurrence quantification analysis (RQA) and self-organizing map (SOM) have been used to analyse pressure drop oscillations during the flow boiling in minichannel. The performed analysis allows us to identify flow patterns based on the character of the pressure drop oscillations. The following two-phase flow patterns have been identified: liquid flow, liquid flow with small vapour bubble, slug flow, long slug flow and confined bubble flow. In the experiment, the open-loop boiling system in a circular horizontal minichannel with an inner diameter of 1 mm was investigated. The two-phase flow patterns at the outlet of the heated section were observed through the glass tube (with an inner diameter of 1 mm) and recorded by a high-speed camera Phantom v1610.

On Instabilities in Horizontal Two-Phase Flow

1994 ◽  
Vol 59 (12) ◽  
pp. 2595-2603
Author(s):  
Lothar Ebner ◽  
Marie Fialová
Keyword(s):  
Differential Equation ◽  
Flow Regime ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Annular Flows ◽  
Flow Regime Maps

Two regions of instabilities in horizontal two-phase flow were detected. The first was found in the transition from slug to annular flow, the second between stratified and slug flow. The existence of oscillations between the slug and annular flows can explain the differences in the limitation of the slug flow in flow regime maps proposed by different authors. Coexistence of these two regimes is similar to bistable behaviour of some differential equation solutions.

Upward Vertical Two-Phase Flow Through an Annulus—Part II: Modeling Bubble, Slug, and Annular Flow

1992 ◽  
Vol 114 (1) ◽  
pp. 14-30 ◽  
Author(s):  
E. F. Caetano ◽  
O. Shoham ◽  
J. P. Brill
Keyword(s):  
Flow Pattern ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Through ◽  
Physical Phenomena ◽  
Good Agreement

Mechanistic models have been developed for each of the existing two-phase flow patterns in an annulus, namely bubble flow, dispersed bubble flow, slug flow, and annular flow. These models are based on two-phase flow physical phenomena and incorporate annulus characteristics such as casing and tubing diameters and degree of eccentricity. The models also apply the new predictive means for friction factor and Taylor bubble rise velocity presented in Part I. Given a set of flow conditions, the existing flow pattern in the system can be predicted. The developed models are applied next for predicting the flow behavior, including the average volumetric liquid holdup and the average total pressure gradient for the existing flow pattern. In general, good agreement was observed between the experimental data and model predictions.

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 Patterns and Cooling Power of Mixed Refrigerant in Micro Cryogenic Coolers

2012 ◽  
Author(s):  
Ryan Lewis ◽  
Hayley Schneider ◽  
Yunda Wang ◽  
Ray Radebaugh ◽  
Y. C. Lee
Keyword(s):  
Liquid Flow ◽  
High Speed ◽  
Single Phase ◽  
Liquid Fraction ◽  
Cryogenic Cooling ◽  
Cooling Power ◽  
Vapor Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Power Draw

Micro cryogenic coolers (MCCs) operating in the Joule-Thomson cycle with mixed refrigerants offer an attractive way to decrease the size, cost, and power draw required for cryogenic cooling. Recent studies of MCCs with mixed refrigerants have, when employing pre-cooling, shown pulsating flow-rates and oscillating temperatures, which have been linked to the refrigerant flow regime in the MCC. In this study we investigate those flow regimes. Using a high-speed camera and optical microscopy, it is found that the pulsations in flow correspond to an abrupt switch from single-phase vapor flow to single-phase liquid flow, followed by 2-phase flow in the form of bubbles, liquid slugs, and liquid slug-annular rings. After this period of 2-phase flow, the refrigerant transitions back to single-phase vapor flow for the cycle to repeat. Under different pre-cooling temperatures, the mole fraction of the vapor-phase refrigerant, as measured by molar flow-rate, agrees reasonably well with the quality of the refrigerant at that temperature as calculated by an equation of state. The frequency of pulsation increases with liquid fraction in the refrigerant, and the volume of liquid in each pulse only weakly increases with increasing liquid fraction. The cooling power of the liquid-flow is up to a factor of 7 greater than that of the 2-phase flows and single-phase vapor flow.

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.

The Visualization of Flow Boiling in a Uniformly Heated Micro Capillary Tube

2006 ◽  
Author(s):  
X. H. Yan ◽  
J. Z. Xu ◽  
D. W. Tang
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Annular Flow ◽  
Capillary Tube ◽  
Flow Boiling ◽  
Bubbly Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Inner Diameter

This work presents experiments on the visualization of flow boiling of water in a horizontally placed and uniformly heated micro capillary tube. Three micro capillary tubes of quartz glass with inner diameters of 520, 315 and 242 μm are prepared. Experiments are performed with deionized water over a mass flux range from 39.3 to 362.5kg/m2s, and the inlet temperatures of 30, 45, and 60 °C respectively. By a video system with microscope and high-speed camera, the vapor-water two-phase flow’s patterns are recorded and analyzed. It has been found that periodic change of two-phase flow patterns and dramatic fluctuations of pressure drop occur in the micro capillary tubes. A new arch flow pattern, liquid film evaporating, and liquid droplet have been observed firstly. Bubbly flow has not been observed during our visual experiments for the inner diameter of 242 μm, the flow patterns are only made up of single liquid phase flow and two-phase elongate slug flow. The main flow regimes in these micro-tubes are single-liquid flow, slug flow, and annular flow with liquid film surrounded in the micro-tube with inner diameter of 520 and 315μm. Trends of pressure drop and flow patterns’ transition are compared and the results show that the increasing process of pressure drop is approximately in the single-liquid flow and bubbly flow, while the decreasing process of pressure drop is in the state of annular flow.

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.

Effect of Tube Size on Flow Pattern of Air-Water Two-Phase Flow in Horizontal Tubes

2013 ◽  
Vol 746 ◽  
pp. 575-580
Author(s):  
Xue Min Liu ◽  
Zhou Hang Li ◽  
Yu Xin Wu ◽  
Jun Fu Lu
Keyword(s):  
Flow Pattern ◽  
Slug Flow ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Plug Flow ◽  
Tube Diameter ◽  
Superficial Velocity ◽  
Phase Flow ◽  
Transition Line ◽  
Two Phase

Aiming at the diameter range of boiler water wall tubes in practical engineering application, the air-water two phase flow pattern in horizontal tube was experimentally investigated in tubes with different inner diameters of 20mm and 8 mm under atmosphere condition. The stratified flow, wave flow, plug flow, slug flow, annular flow, bubbly flow and mist flow were observed in the tubes. Most of the experimental points agree well with the Baker flow pattern map when they appear in the map. With the experimental results, the range lines between the flow patterns were suggested for the tube of 20mm in inner diameter as well as 8mm. As the water superficial velocity increases, the annular flow transforms into mist flow at a decreasing air superficial velocity. The two phase flow patterns transition line is similar in tendency for different tubes. The slug flow transforms into annular flow at an increasing air superficial velocity as tube diameter decreases. The stratified flow transforms into slug flow at an increasing water superficial velocity as tube diameter decreases. The transition line between plug flow and slug flow is independent of tube diameter.

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