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RESEARCH PAPERS

# Modeling Two-Phase Flow in Pipe Bends

[+] Author and Article Information
Savalaxs Supa-Amornkul

Department of Chemical Engineering,  University of New Brunswick Fredericton, N.B. E3B5A3, Canada h796e@unb.ca

Frank R. Steward

Centre for Nuclear Energy Research, Enterprise UNB Building,  University of New Brunswick, Fredericton, N.B. E3B6C2, Canada fsteward@unb.ca

Derek H. Lister

Department of Chemical Engineering,  University of New Brunswick Fredericton, N.B. E3B5A3, Canada dlister@unb.ca

J. Pressure Vessel Technol 127(2), 204-209 (Dec 08, 2004) (6 pages) doi:10.1115/1.1904063 History: Received November 04, 2004; Revised December 08, 2004

## Abstract

In order to have a better understanding of the interaction between the two-phase steam-water coolant in the outlet feeder pipes of the primary heat transport system of some CANDU reactors and the piping material, themalhydraulic modelling is being performed with a commercial computational fluid dynamics (CFD) code—FLUENT 6.1. The modeling has attempted to describe the results of flow visualization experiments performed in a transparent feeder pipe with air-water mixtures at temperatures below $55°C$. The CFD code solves two sets of transport equations—one for each phase. Both phases are first treated separately as homogeneous. Coupling is achieved through pressure and interphase exchange coefficients. A symmetric drag model is employed to describe the interaction between the phases. The geometry and flow regime of interest are a 73 deg bend in a $5.9cm$ diameter pipe containing water with a Reynolds number of $∼1E5$-1E6. The modeling predicted single-phase pressure drop and flow accurately. For two-phase flow with an air voidage of 5–50%, the pressure drop measurements were less well predicted. Furthermore, the observation that an air-water mixture tended to flow toward the outside of the bend while a single-phase liquid layer developed at the inside of the bend was not predicted. The CFD modeling requires further development for this type of geometry with two-phase flow of high voidage.

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## Figures

Figure 1

(a) End fitting and feeder pipe geometry, (b) end view of end fitting and feeder pipe, showing actual orientation, and (c) grid system

Figure 2

Pressure distribution along tube bend, experiment, and prediction (single-phase, flow rate=0.019m3∕s, temperature=25°C)

Figure 3

Predicted velocity distribution along the pipe bend

Figure 4

Oil pattern from flow visualization experiment

Figure 5

Pressure distribution along tube bend, experiment, and prediction (volume fraction of air=14%, liquid flow rate=0.0312m3∕s, temperature=25°C)

Figure 6

Pressure distribution along tube bend, experiment and prediction (volume fraction of air=49%, liquid flow rate=0.0224m3∕s, temperature=25°C)

Figure 7

(a,b) Phase distribution at the bend (volume fraction of air=15%, Re=7.0E5, temperature=25°C)

Figure 8

(a,b) Phase distribution at the bend (volume fraction of air=52%, Re=12.0E5, temperature=40°C)

Figure 9

(a) Air distribution at the middle plane of the feeder pipe (volume fraction of air=49%, Re=9.3E5, temperature=25°C), and (b) water distribution around the wall (volume fraction of air=49%, Re=9.3E5, temperature=25°C)

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