Effect of gas release and condensation on characteristics of two-phase gas-and vapor-liquid slug flow

1996 ◽  
Vol 31 (6) ◽  
pp. 387-391 ◽  
Author(s):  
T. Elperin ◽  
A. Fominykh
Keyword(s):  
Slug Flow ◽  
Gas Release ◽  
Liquid Slug ◽  
Two Phase ◽  
Vapor Liquid

Quantitative Visualization of Vapor Bubble Growth in Diabatic Vapor-Liquid Microchannel Slug Flow

2015 ◽  
Author(s):  
Todd A. Kingston ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Flow Regime ◽  
Vapor Bubble ◽  
Slug Flow ◽  
Flow Boiling ◽  
Flow Behavior ◽  
Circular Cross Section ◽  
Vapor Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Vapor Liquid

Slug flow is a commonly encountered flow regime in microchannels due to the influence of surface tension and vapor confinement at small length scales. Few experimental studies have considered diabatic vapor-liquid slug flow, owing to difficulties in generating a well-controlled and repeatable slug flow regime; generation of vapor by wall heating typically leads to large, stochastic variations in the vapor bubble characteristics. To facilitate the study of flow behavior and vapor-liquid interfaces under precisely controlled conditions, a diabatic, one-component, two-phase microchannel flow was generated by separately injecting HFE-7100 vapor and liquid into a T-junction. Injection at independently controllable liquid and vapor flow rates allows the creation of vapor-liquid slug flow patterns in a downstream borosilicate microchannel of circular cross-section with a 500 μm inside diameter. The outside surface of the microchannel was coated with a 100 nm-thick layer of indium tin oxide (ITO) to generate a uniform wall heat flux via Joule heating while allowing full optical access for flow visualization. The growth of individual vapor bubbles was quantitatively visualized at different imposed heat fluxes, in terms of the percentage change in vapor bubble length along the heated microchannel. The results demonstrate the ability of the T-junction to generate diabatic, one-component, two-phase microchannel slug flow that is suitable for generating results for the validation of flow boiling models.

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

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.

Modelling of Pressure Fluctuation With Cross Flow in a Tight-Lattice Rod Bundle

2008 ◽  
Author(s):  
Weizhong Zhang ◽  
Hiroyuki Yoshida ◽  
Kazuyuki Takase
Keyword(s):  
Numerical Simulation ◽  
Pressure Gradient ◽  
Pressure Fluctuation ◽  
Slug Flow ◽  
Reactor Core ◽  
Approximate Model ◽  
Differential Pressure ◽  
Liquid Slug ◽  
Two Phase ◽  
Simulation Code

An approximate model is presented which permits the prediction in detail of the unsteady differential pressure fluctuation behavior between subchannels in the nuclear reactor core. The instantaneous fluctuation of differential pressure between two subchannels in gas-liquid slug flow regime is deemed as a result of the intermittent nature slug flow in each subchannel. The model is based on the detailed numerical simulation result of two-phase flow that pressure drop occurs mainly in liquid slug region and in the bubble region it is negligibly small. The instantaneous fluctuation of differential pressure between the two subchannels is associated with pressure gradient in the liquid slug for each channel. In addition to a hydrostatic gradient, acceleration and frictional gradients are taken into account to predict pressure gradient in the liquid slug. This model temporarily used in conjunction with the numerical simulation code works satisfactorily to reproduce numerical simulation results for instantaneous fluctuation of differential pressure between two modeled subchannels.

Use of Two-Phase CFD Simulations to Develop a Boiling Heat Transfer Prediction Method for Slug Flow Within Microchannels

2015 ◽  
Author(s):  
Mirco Magnini ◽  
John R. Thome
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Prediction Method ◽  
Liquid Slug ◽  
Modeling Framework ◽  
Cfd Simulations ◽  
Two Phase ◽  
Elongated Bubble

This work presents a new boiling heat transfer prediction method for slug flow within microchannels, which is developed and benchmarked against the results of two-phase CFD simulations. The proposed method adopts a two-zone decomposition of the flow for the sequential passage of a liquid slug and an evaporating elongated bubble. The heat transfer is modeled by assuming transient heat conduction across the liquid film surrounding an elongated bubble and sequential conduction/convection within the liquid slug. Embedded submodels for estimating important flow parameters, e.g. bubble velocity and liquid film thickness, are implemented as “building blocks”, thus making the entire modeling framework totally stand-alone. The CFD simulations are performed by utilizing ANSYS Fluent v. 14.5 and the interface between the vapor and liquid phases is captured by the built-in Volume Of Fluid algorithm. Improved schemes to compute the surface tension force and the phase change due to evaporation are implemented by means of self-developed functions. The comparison with the CFD results shows that the proposed method emulates well the bubble dynamics during evaporation, and predicts accurately the time-averaged heat transfer coefficients during the initial transient regime and the terminal steady-periodic stages of the flow.

EXPERIMENTAL STUDY OF TWO-PHASE GAS-LIQUID SLUG FLOW WITH A SLIGHT DIRECTION CHANGE

2015 ◽  
Author(s):  
Rafael Fabricio Alves ◽  
Andressa Carolinne Del Monego ◽  
Cristiane Cozin ◽  
Fausto Arinos de Almeida Barbuto ◽  
Fábio Alencar Schneider ◽  
...  
Keyword(s):  
Experimental Study ◽  
Slug Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Direction Change
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