scholarly journals Bounds on Two-Phase Frictional Pressure Gradient and Void Fraction in Circular Pipes

2014 ◽  
Vol 6 ◽  
pp. 438428 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Pressure Gradient ◽  
Void Fraction ◽  
Two Phase ◽  
Circular Pipes

Performance and pressure distribution changes in a centrifugal pump under two-phase flow

1998 ◽  
Vol 212 (3) ◽  
pp. 165-171 ◽  
Author(s):  
E T Pak ◽  
J C Lee
Keyword(s):  
Pressure Gradient ◽  
Pressure Distribution ◽  
Centrifugal Pump ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Positive Pressure ◽  
Phase Flow ◽  
Flow Conditions ◽  
Two Phase ◽  
Pump Performance

Pump performance characteristics change drastically under two-phase flow conditions from those of single-phase flow. This is due to a change in flow characteristics in the impeller. Owing to a positive pressure gradient the air bubble moves more slowly than the water in the impeller channel, but in the suction surface region of the impeller inlet, where a negative pressure gradient prevails, the bubbles move more quickly than the water. Thus, in the space just after this region the distributions of the void fraction obtained are considerably higher and uneven. The change in the pressure distribution owing to air admission is also particularly evident in the inlet region of the impeller. These changes bring about an alteration of the whole flow pattern in the impeller and also cause a drop in pump performance. The Reynolds-averaged Navier-Stokes equations for two-phase flow in a centrifugal pump impeller are solved using a finite volume method to obtain the pressure, velocities and void fraction respectively. Good agreement is achieved when the predicted results are compared with those measured experimentally within the range of bubbly flow conditions.

A Note on Mixture Density Using the Shannak Definition

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
M. M. Awad
Keyword(s):  
Multiphase Flow ◽  
Pressure Gradient ◽  
Froude Number ◽  
Liquid Density ◽  
Dimensionless Numbers ◽  
Two Phase ◽  
Phase Density ◽  
Mixture Density ◽  
Circular Pipes ◽  
Definition Of

In this study, a note on mixture density using the Shannak definition of the Froude number is presented (Shannak, B., 2009, “Dimensionless Numbers for Two-Phase and Multiphase Flow,” Proceedings of the International Conference on Applications and Design in Mechanical Engineering (ICADME), Penang, Malaysia, Oct. 11–13, 2009). From the definition of the two-phase Froude number, an expression of the two-phase density is obtained. The definition of the two-phase density can be used to compute the two-phase frictional pressure gradient using the homogeneous modeling approach in circular pipes, minichannels, and microchannels. We cannot have gas density≤two-phase density≤liquid density for 0≤mass quality≤1. Therefore, attention must be paid when using the obtained expression of the two-phase density in this note at any x value.

Void Fraction during Two-Phase Flow

1973 ◽  
Vol 15 (3) ◽  
pp. 235-236 ◽  
Author(s):  
D. Chisholm
Keyword(s):  
Pressure Gradient ◽  
Void Fraction ◽  
Two Phase Flow ◽  
Homogeneous Equation ◽  
Phase Flow ◽  
Two Phase ◽  
Phase Velocities

From consideration of the homogeneous equation for frictional pressure gradient, and the relation between friction and void fraction, an equation for the ratio of the phase velocities during two-phase flow, is developed which is interesting in form, easy to use, and agrees with experiment.

Bounds on Two-Phase Flow: Part I — Frictional Pressure Gradient in Circular Pipes

2005 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Turbulent Flow ◽  
Pressure Gradient ◽  
Published Data ◽  
Two Phase ◽  
Working Fluids ◽  
Circular Pipes ◽  
Mass Fluxes ◽  
Wide Range ◽  
Flow Part ◽  
Fanning Friction Factor

Simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient. Both the lower and upper bounds are based on the separate cylinders formulation. The lower bound is based on turbulent-turbulent flow that uses the Blasius equation to represent the Fanning friction factor. The upper bound is based on an equation that represents well the Lockhart-Martinelli correlation for turbulent-turbulent flow. The model is verified using published experimental data of two-phase frictional pressure gradient versus mass flux at constant mass quality. The published data include different working fluids such as R-12 and R-22 at different mass qualities, different pipe diameters, and different saturation temperatures. It is shown that the published data can be well bounded for a wide range of mass fluxes, mass qualities, pipe diameters and saturation temperatures. The bounds models are also presented in a dimensionless form as two-phase frictional multiplier (φl and φg) versus Lockhart-Martinelli parameter (X) for different working fluids such as R-12, R-22, air-oil and air-water mixtures.

Numerical and Experimental Investigation of Stratified Gas-Liquid Two-Phase Flow in Horizontal Circular Pipes

2006 ◽  
Author(s):  
J. L. H. Faccini ◽  
P. A. B. De Sampaio ◽  
J. Su
Keyword(s):  
Experimental Investigation ◽  
Pressure Gradient ◽  
Two Phase Flow ◽  
Stokes Equations ◽  
Experimental Results ◽  
Circular Pipe ◽  
Phase Flow ◽  
Two Phase ◽  
Interface Position ◽  
Circular Pipes

This paper reports numerical and experimental investigation of stratified gas-liquid two-phase flow in horizontal circular pipes. The Reynolds averaged Navier Stokes equations (RANS) with the κ-ω model for a fully developed stratified gas-liquid two-phase flow are solved by using the finite element method. A smooth and horizontal interface surface is assumed without considering the interfacial waves. The continuity of the shear stress across the interface is enforced with the continuity of the velocity being automatically satisfied by the variational formulation. For each given interface position and longitudinal pressure gradient, an inner iteration loop runs to solve the nonlinear equations. The Newton-Raphson scheme is used to solve the transcendental equations by an outer iteration to determine the interface position and pressure gradient for a given pair of volumetric flow rates. The interface position in a 51.2 mm ID circular pipe was measured experimentally by the ultrasonic pulse-echo technique. The numerical results were also compared with experimental results in a 21 mm ID circular pipe reported by Masala [1]. The good agreement between the numerical and experimental results indicates that the κ-ω model can be applied for the numerical simulation of stratified gas-liquid two-phase flow.

Modeling of Two-Phase Frictional Pressure Gradient in Circular Pipes

2015 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Pressure Gradient ◽  
Two Phase Flow ◽  
Effective Property ◽  
Theoretical Method ◽  
Phase Flow ◽  
Pressure Gradients ◽  
Two Phase ◽  
Asymptotic Modeling ◽  
Modeling Approach ◽  
Circular Pipes

In this article, three different methods for modeling of twophase frictional pressure gradient in circular pipes are presented. They are effective property models for homogeneous two-phase flows, an asymptotic modeling approach for separated two-phase flow, and bounds on two-phase frictional pressure gradient. In the first method, new definitions for two-phase viscosity are proposed using a one-dimensional transport analogy between thermal conductivity of porous media and viscosity in two-phase flow. These new definitions can be used to compute the two-phase frictional pressure gradient using the homogeneous modeling approach. In the second method, a simple semi-theoretical method for calculating two-phase frictional pressure gradient using asymptotic analysis is presented. Two-phase frictional pressure gradient is expressed in terms of the asymptotic single-phase frictional pressure gradients for liquid and gas flowing alone. In the final method, simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient in circular pipes. In all cases, the proposed modeling approaches are validated using the published experimental data.

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