Bubble shape estimation in gas-liquid slug flow using wire-mesh sensor and advanced data processing

The thermosyphon is a type of heat exchanger that has been widely used in many applications. The use of thermosyphons has been intensified in recent years, mainly in the manufacture of solar collectors and various industrial activities. A thermosyphon is a vertical sealed tube filled with a working fluid, consisting of, from bottom to top, by an evaporator, an adiabatic section, and a condenser. The study of geyser-boiling phenomena, which occurs inside the thermosyphon is of extreme importance, therefore the experimental analysis of the parameters related to the two-phase flow (liquid-steam), such as void fraction, bubble frequency, bubble velocity, and bubble length are necessary, since these parameters have a significant influence on heat transfer. In this work, a pair of wire mesh sensors was used, a relative innovative technology to obtain experimental values of the reported quantities for measuring these parameters of slug flow in thermosyphons. An experimental setup is assembled and the sensors are coupled to the thermosyphon enabling the development of the experimental procedure. Here is presented an experimental study of a glass thermosyphon instrumented with two Wire-Mesh Sensors, in which the aforementioned slug flow hydrodynamic parameters inherent to the geyser type boiling process are measured. It was measured successfully, as a function of the heat load (110, 120, 130, 140, and 150W), the void fraction (instantly and average), liquid film thickness, translation velocity of the elongated bubbles, lengths of the bubbles, and the liquid slug (displaced by the bubble rise up). It was observed that the higher the heat load, the lower is the bubble translation velocity. For all heat loads, based on the measured length of liquid slug (consequent displacement of liquid volume), caused by bubbles rise from evaporator to condenser, it could be affirmed to some extent that both boiling regime (pool and film) exist in the evaporator. The measured average void fraction (80%) and liquid film thickness (around 2.5mm) during the elongated bubble passages were approximately constant and independent of the heat load.

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An Experimental Characterization of Horizontal Gas-Liquid Slug Flow

Volume 7B: Fluids Engineering Systems and Technologies ◽

10.1115/imece2015-52064 ◽

2015 ◽

Cited By ~ 2

Author(s):

Fernando E. C. Vicencio ◽

Fábio A. Schneider ◽

Cristiane Cozin ◽

Fausto A. Barbuto ◽

Marco J. Da Silva ◽

...

Keyword(s):

Experimental Data ◽

Slug Flow ◽

Probability Distributions ◽

Theoretical Models ◽

Wire Mesh ◽

Liquid Slug ◽

Two Phase ◽

Gas Phases ◽

Log Normal ◽

Flow Variables

The present work is meant to broaden the knowledge on the fluid mechanics of the two-phase slug flows in horizontal pipes by means of an experimental approach. To accomplish this goal, an experimental facility at the LACIT-UTFPR labs consisting of a 25.8 mm ID, 9-m long transparent pipeline was used. A pair of 12×12-node wire-mesh sensors based on electrical capacitance was used to identify the void fraction in each node of the mesh. Bubble velocities, unit cell frequencies, void fractions and the characteristic lengths of this kind of flow were then obtained after a proper signal processing of the experimental data. To verify the measurements, a methodology to evaluate every measurement done in this work was proposed. Due to the intermittent nature of those flows, their characteristic parameters were identified as probability distributions, and approximated by probability density functions (PDF) such as the normal or log-normal ones. Correlations depending upon the inlet superficial velocities of both liquid and gas phases were fitted for the average values and standard deviation of each parameter. Finally, those correlations were compared to the experimental data, with the aim of accurately predicting the aforementioned parameters as functions of the inlet flow variables, so that those parameters can be used in the development of theoretical models for horizontal gas-liquid slug flow.

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Numerical investigation of bubble shape and flow field of gas–liquid slug flow in circular microchannels

International Journal of Heat and Fluid Flow ◽

10.1016/j.ijheatfluidflow.2018.09.008 ◽

2018 ◽

Vol 74 ◽

pp. 28-35 ◽

Cited By ~ 3

Author(s):

Ryo Kurimoto ◽

Kosuke Hayashi ◽

Hisato Minagawa ◽

Akio Tomiyama

Keyword(s):

Flow Field ◽

Numerical Investigation ◽

Slug Flow ◽

Bubble Shape ◽

Liquid Slug ◽

Circular Microchannels

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Bubble Shape Identification and Calculation in Gas-Liquid Slug Flow Using Semi-automatic Image Segmentation

Image Analysis and Processing - ICIAP 2017 - Lecture Notes in Computer Science ◽

10.1007/978-3-319-68548-9_11 ◽

2017 ◽

pp. 116-126

Author(s):

Mauren Louise Sguario C. Andrade ◽

Lucia Valeria Ramos de Arruda ◽

Eduardo Nunes dos Santos ◽

Daniel Rodrigues Pipa

Keyword(s):

Image Segmentation ◽

Slug Flow ◽

Bubble Shape ◽

Liquid Slug ◽

Shape Identification

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Effect of Inclination on Slug Flow Characteristics

Volume 7: Fluid Flow, Heat Transfer and Thermal Systems, Parts A and B ◽

10.1115/imece2010-38119 ◽

2010 ◽

Cited By ~ 1

Author(s):

Lokman A. AbdulKareem ◽

S. Sharaf ◽

Barry J. Azzopardi ◽

Andrew Hunt

Keyword(s):

Slug Flow ◽

Volume Fraction ◽

Phase Distribution ◽

Silicone Oil ◽

Flow Characteristics ◽

Wire Mesh ◽

Sensor Data ◽

Internal Diameter ◽

Liquid Slug ◽

Taylor Bubble

Modern oil/gas well drilling methods in particular in the offshore industry involve deviated drilling in which the production tubing can be inclined at any angle between the vertical and the horizontal. Riser tubes from the seabed to the surface or to floating production vessels (FPSO) will also rarely be exactly vertical. This work describes a study carried out at the University Of Nottingham on the effects of inclination on gas / liquid slug flow. Two advanced tomography techniques were applied simultaneously to the flow of a mixture of air and silicone oil in a 67 mm internal diameter pipe and the pipe was inclined at various angles. A twin plane Electrical Capacitance Tomography (ECT) electrode system driven by Tomoflow electronics was positioned below a Capacitance Wire Mesh Sensor (WMS) developed at Forschungszentrum Rossendorf-Dresden/Germany M. J. Da Silva et al [2]. This enabled an examination of the flow to be carried out at several levels of complexity. Both measuring sensors provide time and cross-sectionally resolved information about the spatial distribution of the phases. Conditions studied were superficial velocities for air ranged from 0.05 to 5.5 m/s and for silicone oil ranged from 0.0 m/s to 0.5 m/s. In present paper, the effect of inclination on the phase distribution in two phase gas liquid slug flow is presented. The liquid hold up within the slug region and in the elongated bubble zone and the averaged liquid hold up were calculated from the output data of the two measurements techniques. Radial gas volume fraction profiles and bubble size distributions were also processed from the wire-mesh sensor data. The shapes of the large bubbles and waves were compared for different inclination angles. The results indicate that the pipe inclination has a significant effect on the slug flow characteristics. Both Taylor bubble and small bubbles in the slug region tend to flow along the upper pipe wall and causing significant variation of Taylor bubble rise velocity with inclination angle.

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