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Multiphase Flows

Single-Phase and Two-Phase Flow Through Thin and Thick Orifices in Horizontal Pipes

[+] Author and Article Information
Manmatha K. Roul, Sukanta K. Dash

Department of Mechanical Engineering,   Bhadrak Institute of Engineering and Technology, Bhadrak, India 756113 e-mail: mkroul@mech.iitkgp.ernet.inDepartment of Mechanical Engineering,   Indian Institute of Technology, Kharagpur, India 721302

J. Fluids Eng 134(9), 091301 (Aug 21, 2012) (14 pages) doi:10.1115/1.4007267 History: Received January 23, 2012; Revised July 14, 2012; Published August 21, 2012; Online August 21, 2012

Two-phase flow pressure drops through thin and thick orifices have been numerically investigated with air–water flows in horizontal pipes. Two-phase computational fluid dynamics (CFD) calculations, using the Eulerian–Eulerian model have been employed to calculate the pressure drop through orifices. The operating conditions cover the gas and liquid superficial velocity ranges Vsg  = 0.3–4 m/s and Vsl  = 0.6–2 m/s, respectively. The local pressure drops have been obtained by means of extrapolation from the computed upstream and downstream linearized pressure profiles to the orifice section. Simulations for the single-phase flow of water have been carried out for local liquid Reynolds number (Re based on orifice diameter) ranging from 3 × 104 to 2 × 105 to obtain the discharge coefficient and the two-phase local multiplier, which when multiplied with the pressure drop of water (for same mass flow of water and two phase mixture) will reproduce the pressure drop for two phase flow through the orifice. The effect of orifice geometry on two-phase pressure losses has been considered by selecting two pipes of 60 mm and 40 mm inner diameter and eight different orifice plates (for each pipe) with two area ratios (σ = 0.73 and σ = 0.54) and four different thicknesses (s/d = 0.025–0.59). The results obtained from numerical simulations are validated against experimental data from the literature and are found to be in good agreement.

Copyright © 2012 by by ASME
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Figures

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Figure 1

Single-phase flow across (a) thin and (b) thick orifices

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Figure 2

Computational domain for σ = 0.54, s/d = 0.20, D = 40 mm

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Figure 3

Axial pressure drop at the orifice section as a function of grid size. (a) Pressure profile, (b) pressure drop (Re = 100,000, σ = 0.54, s/d = 0.20, D = 40 mm).

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Figure 4

Local pressure drop at the orifice section by extrapolating the upstream and downstream computed pressure profiles to the orifice section

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Figure 5

(a) Velocity vectors and (b) stream lines for single phase water flow through orifice σ = 0.54, s/d = 0.027, and D = 40 mm

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Figure 6

(a) Velocity vectors and (b) stream lines for single phase water flow through orifice σ = 0.54, s/d = 0.2, and D = 40 mm

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Figure 7

(a) Velocity vectors and (b) stream lines for single phase water flow through orifice σ = 0.54, s/d = 0.59, and D = 40 mm

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Figure 10

Normalized axial pressure profile at the orifice section for two different pipes (σ = 0.54, s/d = 0.59, Re = 100,000)

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Figure 11

Pressure profiles for single phase water flow through different orifices (D = 40 mm)

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Figure 12

Contraction coefficient as a function of local Reynolds number for σ = 0.54

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Figure 13

Contraction coefficient as a function of local Reynolds number for σ = 0.73

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Figure 14

Single-phase pressure drop as a function of local Reynolds number for σ = 0.54

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Figure 15

Pressure profiles for two-phase air-water flow through D = 40 mm, s/d = 0.2, (a) σ = 0.54, (b) σ = 0.73 orifice

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Figure 16

Local pressure drop as a function of gas superficial velocity and orifice thickness (a) σ = 0.54, (b) σ = 0.73

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Figure 17

Pressure multiplier versus gas volume fraction for different orifice thickness, σ = 0.54 (a) Vsl  = 0.6 m/s, (b) Vsl  = 2.0 m/s (filled symbols for D = 40 mm, empty symbols for D = 60 mm)

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Figure 18

Pressure multiplier versus gas volume fraction for different orifice thickness, σ = 0.73 (a) Vs l  = 1.1 m/s, (b) Vsl  = 2.0 m/s (filled symbols for D = 40, empty symbols for D = 60 mm)

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Figure 19

Average void fraction along the pipe (D = 40 mm) for different orifice thickness and area ratio

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Figure 20

Slip ratio as a function of gas volume fraction at different location for σ = 0.54 and D = 60 mm (filled symbols Expt. [11], empty symbols computation), (a) Vsl  = 0.6 m/s, (b) Vsl  = 2.0 m/s

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Figure 21

Slip ratio as a function of gas volume fraction at different location for σ = 0.73 and D = 40 mm (filled symbols Expt. [11], empty symbols computation), (a) Vsl  = 1.1 m/s, (b) Vsl  = 2.0 m/s

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Figure 8

Pressure profiles for single phase water flow through D = 40 mm, σ = 0.54, (a) s/d = 0.025, (b) s/d = 0.2, (c) s/d = 0.59 orifice

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Figure 9

Normalized axial pressure profile at the orifice section for different Reynolds number (D = 40 mm, σ = 0.54, s/d = 0.025)

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