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Abstract
This paper reports an experimental and numerical investigation of stratified gas–liquid two-phase flow in downward-inclined circular pipes. Reynolds averaged Navier–Stokes equations with the κ–ω turbulence model were solved by using the least-square finite-element method to simulate the stratified gas–liquid flow. Experiments were carried out in an air–water two-phase flow loop with a test section of 7.8-m-long circular pipe with 1 inch inner diameter for 3 downward-inclined angles, −2.5°, −5.0°, and −10.0°. The height of the liquid layer was measured by using a pulse–echo ultrasonic technique with a single fast transducer and a visualization technique with a high-speed digital camera. Numerical results for the liquid height and hold-up as a function of inclination angles were compared favorably with experimental results of the present study and literature data.
NOMENCLATURE
| A | = | area, m2 |
| Ai | = | coefficients |
| Bi | = | coefficients |
| cw | = | water sound velocity, m/s |
| Ci | = | coefficients |
| d | = | inner diameter of the pipe, m |
| e | = | unit vector |
| g | = | gravity, m/s2 |
| hL | = | water film height, m |
| n | = | normal unit vector |
| N | = | finite element shape function |
| p | = | pressure, Pa |
| Q | = | volumetric flow rate, m3/s |
| Re | = | Reynolds number |
| s | = | experimental standard deviation |
| Si | = | source terms |
| t | = | time, s |
| u | = | velocity, m/s |
| x | = | horizontal coordinate |
| y | = | vertical coordinate |
| z | = | longitudinal coordinate |
Greek Symbols
| α | = | void fraction |
| αL | = | model parameter |
| αG | = | model parameter |
| β | = | volumetric fraction |
| βL | = | model parameter |
| βG | = | model parameter |
| γ | = | angle, degrees |
| Γ | = | boundary |
| ϵ | = | dissipation rate, m2/s3 |
| ΦG | = | gas multiplier |
| κ | = | turbulent kinetic energy, m2/s2 |
| μ | = | fluid viscosity, kg/m-s |
| μt | = | eddy viscosity, kg/m-s |
| ρ | = | density, kg/m3 |
| σL | = | model parameter |
| σG | = | model parameter |
| ω | = | specific dissipation rate, s−1 |
| Ω | = | domain |
Subscripts
| 2P | = | two-phase |
| c | = | wall |
| G | = | gas phase |
| L | = | liquid phase |
| i | = | index |
| int | = | interface |
| s | = | symmetry boundary, superficial |
Additional information
Notes on contributors
José L. H. Faccini
José L. H. Faccini is a senior researcher of the Nuclear Engineering Institute (IEN) of the Brazilian Nuclear Energy Commission (CNEN). He received his bachelor in mechanical engineering degree from the Federal University Fluminense, Brazil, in 1980, and his D.Sc. degree in nuclear engineering from the Federal University of Rio de Janeiro, Brazil, in 2008. His research topics includes multiphase flow, natural circulation, experimental reactor thermal hydraulics, and reactor technology.
Jurandyr S. Cunha Filho
Jurandyr S. Cunha Filho works at Fundação de Apoio as Escolas Técnicas do Rio de Janeiro (FAETEC/RJ) as Technical Coordinator. He received his bachelor in mechanical engineering degree from the Fundação Técnico Educacional Souza Marques, Brazil, in 1986, and his D.Sc. degree in nuclear engineering from the Federal University of Rio de Janeiro, Brazil, in 2010. He conducts research in two-phase gas–liquid flow in horizontal and inclined tubes in reactor technology.
Paulo A. B. De Sampaio
Paulo A. B. De Sampaio is the director of the Nuclear Engineering Institute (IEN) of the Brazilian Nuclear Energy Commission (CNEN). He received his B.Sc. in mechanical engineering from the Rio de Janeiro Federal University, Brazil, in 1983, his M.Sc. in nuclear engineering from the Rio de Janeiro Federal University, Brazil, in 1985, and his Ph.D. degree in civil engineering from the University of Wales (Swansea), United Kingdom, in 1991. His research topics include computational fluid-dynamics (CFD), reactor thermal hydraulics, reactor technology, and the finite-element method.
Jian Su
Jian Su is an associate professor of Nuclear Engineering at Alberto Luiz Coimbra Institute of Graduate School and Research in Engineering, Federal University of Rio de Janeiro (COPPE/UFRJ). He holds a B.Sc. degree in engineering thermophysics from University of Science and Technology of China, Hefei, an M.Sc. degree from Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing, and a D.Sc. degree in mechanical engineering from Federal University of Rio de Janeiro. His research interests include fluid mechanics, heat transfer, multiphase, nuclear reactor thermohydraulics, turbomachinery aerodynamics, fluid-structure interaction, and environmental impact assessment.