Similarities and differences in the flow patterns and void fraction in vertical upward and downward two phase flow

Bhagwat, Swanand M.; Ghajar, Afshin J.

doi:10.1016/j.expthermflusci.2012.01.026

Cited by 105 publications

(58 citation statements)

References 29 publications

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“…However, a close observation reveals some differences in the shape of the nose and tail region of the slug in addition to the effect of pipe orientation on slug flow direction. The slug in vertical upward orientation appears as a bullet shaped elongated gas bubble pointing in upward direction (due to buoyancy acting in flow Bhagwat and Ghajar [13] have identified that the slug flow in vertical downward orientation initially shows a blunt bubble nose pointing in upward direction for the low values of gas and liquid flow rates. As shown in Fig.…”

Section: Flow Patterns and Flow Patterns Mapmentioning

confidence: 97%

“…The horizontal flow direction allows existence of bubbly, slug, stratified, wavy and annular flow patterns. Bhagwat and Ghajar [13] illustrated that the two extreme opposite flow directions namely, vertical up and vertical down pipe orientations significantly influence the general appearance of the flow patterns and their transition from one to another. The flow visualization of the bubbly and slug flow show a significant influence of the flow direction on the alignment of one phase with respect to another.…”

Section: Flow Patterns and Flow Patterns Mapmentioning

confidence: 99%

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Flow Patterns, Void Fraction and Pressure Drop in Gas-Liquid Two Phase Flow at Different Pipe Orientations

Ghajar

Bhagwat

2014

Frontiers and Progress in Multiphase Flow I

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This chapter presents an insightful discussion on flow patterns, void fraction and phenomenon of two phase frictional pressure drop in gas-liquid two phase flow. The flow structure of different flow patterns observed in gas-liquid two phase flow at various pipe orientations are described with the aid of flow visualization. This chapter is helpful in understanding the impact of varying flow patterns, pipe diameter and pipe orientation on the void fraction and two phase pressure drop. Additionally, a brief overview of the void fraction, its dependency on the flow patterns and its influence on the hydrostatic pressure drop is presented. A brief synopsis of the two phase void fraction and frictional pressure drop correlations available in the literature is presented. The performance of these correlations is assessed against a comprehensive database for air-water and refrigerant two phase flow conditions. Based on this detailed analysis, the top performing void fraction and pressure drop correlations are identified and recommended for use for these fluid combinations in different two phase flow situations. Finally, application of the recommended correlations is presented in the form of solved problems. It is expected that these solved problems will give readers an idea of selection and implementation of appropriate correlations for different two phase flow conditions.

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Section: Flow Patterns and Flow Patterns Mapmentioning

confidence: 97%

Section: Flow Patterns and Flow Patterns Mapmentioning

confidence: 99%

Flow Patterns, Void Fraction and Pressure Drop in Gas-Liquid Two Phase Flow at Different Pipe Orientations

Ghajar

Bhagwat

2014

Frontiers and Progress in Multiphase Flow I

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“…Hibiki et al [17] recommended a set of correlations applicable to the predictions of one-dimensional void fractions and interfacial area concentrations for a downward bubbly flow. Bhagwat and Ghajar [18] analyzed 1208 and 909 experimental data points for upflow and downflow, respectively, and demonstrated definite variations in the void fractions with varying phase flow rates. Many researchers [19][20][21][22][23][24] have investigated the flow patterns of the twophase upflow and downflow.…”

Section: Introductionmentioning

confidence: 99%

Gas‐water energy conversion efficiency in two‐phase vertical downflow

Sun

Yao

Fan

et al. 2018

Energy Science & Engineering

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An automatic pump is developed using low water-head hydropower. The energy conversion efficiency η of the gas-water energy conversion equipment is the focus. In this equipment, low-head water normally drains to the vertical downcomer. When water particles separate via gravity, a vacuum is generated, and air is mixed into the water spontaneously. High-pressure gas is ultimately produced at the end of the pipe. To discuss the effects of the air intake pipe diameter, river drop and water flow rate on η, a full-scale experiment is conducted, and an analytical solution based on the separation of water particles is derived. The air intake pipe diameter has almost no effect on η, but η changes dramatically as the water flow rate varies. Meanwhile, η initially increases and then decreases as the river drop increases. These findings enable the development of a method for low water-head hydropower utilization. 307

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“…This limits the applicability of the available void fraction correlations to the experimental data they are derived from. The flow patterns and the void fraction appearing in the vertical upward, downward and horizontal two phase flow were studied in detail by [4][5][6]. The flow patterns and the void fraction for upward inclined and downward inclined pipes were studied by [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Flow Pattern and Pipe Orientation Independent Semi-Empirical Void Fraction Correlation for a Gas-Liquid Two Phase Flow Based on the Concept of Drift Flux Model

Bhagwat

Ghajar

2012

Volume 2: Heat Transfer Enhancement for Practical Applications; Fire and Combustion; Multi-Phase Systems; Heat Transfer in Elec

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A flow pattern and pipe orientation independent void fraction correlation is proposed in the present study. The correlation is based on the concept of drift flux model and proposes two separate expressions to model distribution parameter and drift velocity. The distribution parameter is expressed as a function of pipe orientation, phase superficial velocities and the void fraction in implicit form, while the drift velocity parameter is modeled as a function of fluid thermo physical properties, pipe orientation and void fraction. The drift velocity equation proposed by Zukoski [1] is extended for downward inclined pipe orientations. The performance of the proposed void fraction correlation is verified against void fraction data set of 5928 data points including the data for fifteen pipe diameters and eight different fluid combinations. The superiority of the proposed correlation is also illustrated by comparing it against the top performing correlations in horizontal, vertical upward and vertical downward pipe orientations and the predictions of the Woldesemayat and Ghajar [2] and Chexal et al. [3] correlations for incline pipe orientations.

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Similarities and differences in the flow patterns and void fraction in vertical upward and downward two phase flow

Cited by 105 publications

References 29 publications

Flow Patterns, Void Fraction and Pressure Drop in Gas-Liquid Two Phase Flow at Different Pipe Orientations

Flow Patterns, Void Fraction and Pressure Drop in Gas-Liquid Two Phase Flow at Different Pipe Orientations

Gas‐water energy conversion efficiency in two‐phase vertical downflow

Flow Pattern and Pipe Orientation Independent Semi-Empirical Void Fraction Correlation for a Gas-Liquid Two Phase Flow Based on the Concept of Drift Flux Model

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