Numerical Investigation on Flow Pattern and Pressure Drop Characteristics of Slug Flow in a Micro Tube

2008 ◽  
Author(s):  
Qunwe He ◽  
Nobuhide Kasagi
Keyword(s):  
Surface Tension ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Thin Liquid Film ◽  
Surface Tension Force ◽  
Tension Force ◽  
Flow Profile ◽  
Liquid Slug ◽  
Two Phase

In the present study, numerical simulation of adiabatic air-water slug flow in a micro tube is carried out. The focus is laid upon the pressure drop characteristics and its modeling. The Phase-Field method is employed to capture the interface between the phases, while the surface tension force is represented by the chemical potential formulation. The numerical results agree fairly well with available experimental results in terms of bubble shape and flow pattern. Simulation is repeated under different conditions of pressure gradient, void fraction and bubble frequency. It is found that the total pressure drop of a slug flow can be decomposed into two parts, i.e., the frictional pressure drop associated with a liquid slug sandwiched by bubbles, and the pressure drop over a bubble itself. For the former, when the liquid slug is longer than one tube diameter, the cross-sectional velocity distribution resembles a Poiseuille flow profile, so that the corresponding pressure drop can be predicted by the theoretical solution of single-phase liquid flow, i.e., fReTP = 64. For the latter, if it is assumed that the surface tension force is strong enough to sustain a thin liquid film between the interface and the tube wall, the pressure drop in this region is negligible. The pressure drop over a bubble is solely dependent on the two-phase superficial Reynolds number ReTP, which can be correlated as: Δpbubb′ = 0.07 + 42.4 / ReTP. This correlation predicts well the two-phase pressure drop in the form of the two-phase multiplier correlation as a function of the Lockhart-Martinelli parameter.

Surface Tension Effects on Liquid Flow in Small Plastic Tubes When Gas Bubbles are Present

2005 ◽  
Vol 219 (8) ◽  
pp. 853-857 ◽  
Author(s):  
M. R. Myers ◽  
H. M. Cave ◽  
S. P. Krumdieck
Keyword(s):  
Surface Tension ◽  
High Pressure ◽  
Pressure Drop ◽  
Liquid Flow ◽  
Slug Flow ◽  
Small Diameter ◽  
Gas Bubbles ◽  
Flow Regimes ◽  
Liquid Slug ◽  
Two Phase

Two-phase intermittent gas and liquid slug flow in small diameter glass and plastic tubes was studied. Two distinct flow regimes and the transition phenomena were identified. A modified Hagen-Poiseuille relation was derived to describe the extremely high pressure drop due to the surface tension effects of pinned slug flow.

Numerical Simulation of Two-Phase Slug Flows in Microchannels

2009 ◽  
Author(s):  
A. Mehdizadeh ◽  
S. A. Sherif ◽  
W. E. Lear
Keyword(s):  
Surface Tension ◽  
Slug Flow ◽  
Stokes Equations ◽  
Pressure Fluctuations ◽  
Water Interface ◽  
Liquid Slug ◽  
Complex Flow ◽  
Two Phase ◽  
Air Water Interface ◽  
Slug Flows

In this paper the Navier-stokes equations for a single liquid slug have been solved in order to predict the circulation patterns within the slug. Surface tension effects on the air-water interface have been investigated by solving the Young–Laplace equation. The calculated interface shape has been utilized to define the liquid slug geometry at the front and tail interfaces of the slug. Then the effects of the surface tension on the hydrodynamics of the two-phase slug flow have been compared to those where no surface tension forces exist. The importance of the complex flow field features in the vicinity of the two interfaces has been investigated by defining a non-dimensional form of the wall shear stress. The latter quantity has been formulated based on non-dimensional parameters in order to define a general Moody friction factor for typical two-phase slug flows in microchannels. Moreover, the hydrodynamics of slug flow formation has been examined using computational fluid dynamics (CFD). The volume-of-fluid (VOF) method has been applied to monitor the growth of the instability at the air-water interface. The lengths of the slugs have been correlated to the pressure fluctuations in the mixing region of the air and water streams at an axisymmetric T-junction. The main frequencies of the pressure fluctuations have been investigated using the Fast Fourier Transform (FFT) method.

Pressure drop of two-phase liquid-liquid slug flow in square microchannels

2018 ◽  
Vol 191 ◽  
pp. 398-409 ◽  
Author(s):  
Agnieszka Ładosz ◽  
Philipp Rudolf von Rohr
Keyword(s):  
Pressure Drop ◽  
Slug Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Phase Liquid

A Flow Model for Two-Phase Slug Flow in Horizontal Tubes

1961 ◽  
Vol 83 (4) ◽  
pp. 613-618 ◽  
Author(s):  
E. S. Kordyban
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Flow Model ◽  
Simplified Model ◽  
Two Phase ◽  
Frictional Pressure Drop ◽  
Horizontal Tubes

The paper presents a construction of a simplified model approximating the actual observed flow pattern. The resulting expressions for frictional pressure drop are found to agree fairly well with the author’s data for steam and water and the data for air and water of other investigators. The similarity with a portion of the Chenoweth-Martin correlation appears to present a logical explanation for the applicability of that correlation to slug flow.

Void Fraction, Pressure Drop, and Flow Pattern Behavior for Two-Phase Non-Newtonian Slug Flow

2021 ◽  
Author(s):  
Faraj Ben Rajeb ◽  
Syed Imtiaz ◽  
Yan Zhang ◽  
Amer Aborig ◽  
Mohamed M. Awad ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Flow Regime ◽  
Void Fraction ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Intermittent Flow ◽  
Phase Flow ◽  
Two Phase

Abstract Slug flow is one of the most common flow patterns in non-Newtonian two-phase flow in pipes. It is a very common occurrence in gas-liquid two-phase flow in the pipe. Usually, it is an unfavorable flow pattern due to its unsteady nature, intermittency as well as high pressure drop. The differences between slug flow and elongated bubble flow are not clear because usually these two types of flow combined under one flow category. In general, these two-phase flow regimes are commonly defined as intermittent flow. In the present study, pressure gradient, and wave behavior in slug flow have been investigated depending on experimental work. In addition, void fraction has been estimated regarding available superficial liquid and gas velocities. The experimental records of superficial velocities of gas and liquid for slug flow and other flow patterns is used to create flow regime map for the gas non-Newtonian flow system. The effect of investigated flow regime velocities for non-Newtonian/gas flow on pressure drop and void fraction is reported. Pressure drop has been discovered to be reduced in slug flow more than other flow patterns due to high shear thinning behavior.

Numerical Studies on Non-Boiling Two-Phase Flows in Microtubes and Microchannels: A Review

2010 ◽  
Author(s):  
V. Talimi ◽  
Y. S. Muzychka
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Pattern ◽  
Research Literature ◽  
Heat Transfer Characteristics ◽  
Liquid Slug ◽  
Two Phase Flows ◽  
Two Phase ◽  
Numerical Studies ◽  
Slug Flows

Numerical studies on the hydrodynamic and heat transfer characteristics of two-phase flows in small tubes and channels are reviewed. These flows are gas-liquid and liquid-liquid slug flows. The review is categorized into two groups of studies: circular and non-circular channels. Different aspects such as slug formation, slug shape, flow pattern, pressure drop and heat transfer are of interest. According to this review, there are some large gaps in the research literature, including pressure drop and heat transfer in liquid-liquid slug flows. Gaps in research are also found in applications of non-circular ducts, pressure drop and heat transfer in meandering microtubes and microchannels for both of gas-liquid and liquid-liquid two-phase flows.

An Experimental Investigation of Droplet Detachment in High-Speed Microchannel Air Flow

2009 ◽  
Author(s):  
Brian Carroll ◽  
Carlos Hidrovo
Keyword(s):  
Surface Tension ◽  
Pressure Drop ◽  
High Speed ◽  
Air Flow ◽  
Surface Tension Force ◽  
Tension Force ◽  
Spherical Droplet ◽  
Major Mechanism ◽  
Order Of Magnitude ◽  
Droplet Detachment

This paper experimentally investigates the mechanism of water droplet detachment in a confined microchannel under highly inertial air flow. Experimental observations show that as the Reynolds number in the channel is increased, the droplet transitions from a nearly spherical droplet to a high aspect ratio slug. Scaling arguments are then made to address this behavior in an order of magnitude sense. These results show that although shear stress at the droplet-air interface may contribute to droplet elongation, the major mechanism of droplet detachment appears to be the pressure drop across the droplet. This pressure drop is a result of a highly inertial air flow being squeezed through a narrow gap between the droplet and the adjacent microchannel wall. This pressure difference creates a force imbalance across the droplet that overcomes the surface tension force pinning the droplet at the injection site, thereby leading to droplet detachment. A formulation of a nondimensional number is then presented that relates the pressure force acting across the droplet to the surface tension force at the droplet wall interface, which indicates that detachment occurs when this number is of order 1.

Adiabatic Air-Water Two-Phase Flow in Circular Microchannels

2011 ◽  
Author(s):  
Aritra Sur ◽  
Dong Liu
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Flow Patterns ◽  
Phase Flow ◽  
Water Mixture ◽  
Two Phase ◽  
Phase Pressure ◽  
Circular Microchannels

Gas-liquid two-phase flow in microchannels with hydraulic diameters of 100–500 μm exhibits drastically different flow behaviors from its counterpart in conventional macroscopic channels. Two particular issues are how to determine the two-phase flow patterns and how to predict the two-phase pressure drop at given flow conditions in these microchannels. This paper presents an experimental study of adiabatic two-phase flow of air-water mixture in circular microchannels with inner diameters of 100, 180 and 324 μm, respectively, to investigate the effects of channel size and phase velocity on the two-phase flow pattern and pressure drop. The air and water superficial velocities were in the range of 0.01–120 m/s and 0.005–5 m/s. Two-phase flow patterns were visualized using highspeed photographic technique. Four basic flow patterns, namely, bubbly flow, slug flow, ring flow and annular flow, were observed. The two-phase flow maps were then constructed and the transition boundaries between different flow regimes were identified. It was found that the slug flow is the dominant two-phase flow pattern in microchannels, and the transition boundaries generally shift to regions of higher gas superficial velocities as the channel dimension decreases. The experimental measurements of two-phase pressure drop were compared to the predictions from the available two-phase models in the literature. Results show that the flow pattern-based models provide the best prediction of two-phase pressure drop in microchannels.

Determination and Characteristics of the Transition to Two-Phase Slug Flow in Small Horizontal Channels

1994 ◽  
Vol 116 (1) ◽  
pp. 140-146 ◽  
Author(s):  
M. W. Wambsganss ◽  
J. A. Jendrzejczyk ◽  
D. M. France
Keyword(s):  
Pressure Drop ◽  
Flow Pattern ◽  
Slug Flow ◽  
Static Pressure ◽  
Two Phase Flow ◽  
High Mass ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Pattern Transition ◽  
Phase Pressure

Two-phase pressure drop and fluctuating static pressures were measured in a small horizontal rectangular channel (hydraulic diameter = 5.44 mm). The two-phase fluid was an air/water mixture at atmospheric pressure tested over a mass flux range of 50 to 2000 kg/m2˙s. Two-phase flow patterns were identified and an objective method was found for determining the flow pattern transition from bubble or plug flow to slug flow. The method is based on an RMS static pressure measurement. In particular, it is shown that the transition is accompanied by a clear and abrupt increase in the RMS pressure when plotted as a function of mass quality. Use of the RMS pressure as a two-phase flow pattern transition indicator is shown to have advantages over pressure-versus-time trace evaluations reported in the literature. The transition is substantiated by a clear local change in slope in the curve of two-phase pressure drop plotted as a function of either Martinelli parameter or mass quality. For high mass fluxes, the change in slope is distinguished by a local peak. Some degree of substantiation was found in previous work for both of the results (the RMS static pressure change and the local pressure drop change) at the transition to slug flow.

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