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 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.

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

Detailed Characterization of Two-Phase Annular Flow in a Horizontal Tube

Volume 3 ◽  
2004 ◽  
Author(s):  
DuWayne Schubring ◽  
Timothy A. Shedd
Keyword(s):  
Pressure Drop ◽  
Film Thickness ◽  
Wave Velocity ◽  
Liquid Flow ◽  
Annular Flow ◽  
Flow Regimes ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Dependence ◽  
Annular Regime

In this study, non-intrusive pressure drop, liquid film thickness distribution and wave behavior measurements have been obtained for 140 and 220 two-phase flow conditions in horizontal 8.8 mm I.D and 15.1 mm I.D. tubes, respectively. Horizontal flow regimes ranging from stratified-wavy to annular were studied in long clear test sections. Pressure drop data appeared to show different trends for the wavy, wavy-annular and annular flow regimes, suggesting that a unique model may be required for each. In addition, wave frequency showed clearly different behavior for these regimes, with only minor liquid flow dependence in the wavy and wavy-annular flows and strong liquid flow dependence in annular flow. Interestingly, disturbance wave velocity could be correlated to within 10% by the gas friction velocity in the annular regime and within 20% in the wavy-annular regime, leading to a simple correlation between pressure drop and wave velocity. Base film thickness data (between waves) show that the film is relatively insensitive to gas flow at the side and top of the tube and that the film thickness around the tube becomes nearly independent of liquid flow rate at high gas flows. Empirical correlations of the various data sets are presented with the goal of aiding general horizontal two-phase flow modeling efforts.

Two-Phase Flow Induced Force Fluctuations on Pipe Bend

2014 ◽  
Author(s):  
Shuichiro Miwa ◽  
Yang Liu ◽  
Takashi Hibiki ◽  
Mamoru Ishii ◽  
Yoshiyuki Kondo ◽  
...  
Keyword(s):  
Flow Regime ◽  
Slug Flow ◽  
Two Phase Flow ◽  
Pressure Fluctuations ◽  
Flow Regimes ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Pipe Bend ◽  
Force Fluctuation

In this study, fluctuating force induced by both upward and horizontal gas-liquid two-phase flow on 90 degree pipe bend at atmospheric condition was investigated. First, the database comprised of dynamic force signals and two-phase flow parameters such as volumetric fluxes, area averaged void fraction and pressure fluctuations covering entire two-phase flow regimes was developed for both flow orientations. Then, study was conducted to develop a model which is capable of predicting the force fluctuation frequency and magnitudes particularly for the slug flow regime. The model was fundamentally developed from the local instantaneous two-fluid model which was applied to the control volume around the elbow test section. Main contribution of the force fluctuation of two-phase flow is from the momentum and pressure fluctuations for most of the flow regimes. For slug flow regime, however, water-hammer like impact was produced by the collision of liquid slug against the structure surface. In order to consider that effect, the liquid slug impact force model was developed. The model utilizes two-group interfacial area concentration correlation to treat the flow regime transition without an abrupt discontinuity. It was found that the newly developed model is capable of predicting two-phase flow induced force fluctuation and dominant frequency range with satisfactory accuracy for flow regimes up to churn-turbulent.

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.

Numerical investigations of gas–liquid two-phase flows in microchannels

2017 ◽  
Vol 232 (3) ◽  
pp. 466-476 ◽  
Author(s):  
Qin Lou ◽  
Mo Yang ◽  
Hongtao Xu
Keyword(s):  
Surface Tension ◽  
Steady State ◽  
Mass Exchange ◽  
Slug Flow ◽  
Inertial Force ◽  
Flow Regimes ◽  
Channel Width ◽  
Viscous Force ◽  
Two Phase Flows ◽  
Two Phase

Immiscible gas–liquid two-phase flows with an initial stochastically distribution, which are driven by a constant body force in a period microchannel of [Formula: see text] in width, are studied using the lattice Boltzmann method under various conditions. Continuous dynamic behaviors of bubbles and droplets including breaking up, coalescence, deformation, and mass exchange between them are observed. The flows reach to their steady state when the rate of breaking up and coalescence are in balance, and no mass exchange occurs. The simulation results show that the steady-state flow regimes depend strongly on the viscous force, surface tension, inertial force, channel width, and wettability of the solid surface. Specially, it is found that slug flow is more probable to occur for the small channel width at the same volume fraction. And the shape of bubble in the slug flow is determined by the wettability of the solid wall. Furthermore, the shape and number of bubbles at steady state are related to surface tension, viscous force, and inertial force. It is also found that the initial bubble distributions have slight effects on the flow regimes at steady state.

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