Begell House Inc.
Multiphase Science and Technology
MST
0276-1459
27
1
2015
VISCOUS OIL-WATER FLOW THROUGH AN INCLINED PIPELINE: EXPERIMENTATION AND PREDICTION OF FLOW PATTERNS
1-26
10.1615/MultScienTechn.v27.i1.10
Anjali
Dasari
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
Bharath Kumar
Goshika
Department of Chemical Engineering, Indian Institute of Technology Guwahati,
Guwahati-781039, Assam, India
Subrata Kumar
Majumder
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, PIN-781039, Assam, India
Tapas K
Mandal
Department of Chemical Engineering, Indian Institute of Technology Guwahati, Guwahati, Assam, India
viscous oil-water
inclined pipe
flow pattern prediction
probabilistic neural network (PNN)
transition boundaries
We identify and predict the flow patterns observed during concurrent flow of viscous oil (viscosity 107 m Pa s, density 889 kg/m3) and water through a +5 deg inclined circular Perspex pipe with internal diameter of 0.025 m. Flow patterns have been identified with the help of visual and photographic techniques in a wide range of superficial velocities of both the fluids (USO = 0.052−1.38 m/s and USW = 0.068−1.23 m/s). Seven different flow patterns (namely, plug, slug, wavy stratified, stratified mixed, annular, dispersion of oil in water, and dispersion of water in oil flow) have been identified and a flow pattern map has been developed for the present system. Flow pattern transition boundaries have been predicted by analytical models and probabilistic neural network (PNN) technique. Transition of wavy stratified to stratified mixed flow pattern has been predicted following the drop formation mechanism at interface proposed by Al-wahibi, Smith, and Angeli, (Transition between Stratified and Non-Stratified Horizontal Oil-Water Flows: Part II. Mechanism of Drop Formation, Chem. Eng. Sci., vol. 62, pp. 2929−2940, 2007). During the development of PNN, superficial velocities of oil and water, pipe diameter, viscosity ratio, density ratio, interfacial tension, and pipe inclination have been considered as governing parameters of the flow patterns. The trained PNN
gives a better prediction over the analytical models with accuracy of ∼90%.
BUBBLE TRACKING IN BUBBLY GAS-LIQUID TWO-PHASE FLOW IN POROUS STRUCTURES
27-49
10.1615/MultScienTechn.v27.i1.20
Marco
Altheimer
Institute of Process Engineering, Swiss Federal Institute of Technology (ETH), Zürich, Sonneggstrasse 3, 8092 Zürich, Switzerland
Carmen
Wälchli
Institute of Process Engineering, Swiss Federal Institute of Technology (ETH), Zürich, Sonneggstrasse 3, 8092 Zürich, Switzerland
Philipp Rudolf
von Rohr
Institute of Process Engineering, Swiss Federal Institute of Technology (ETH), Zürich, Sonneggstrasse 3, 8092 Zürich, Switzerland
bubbly flow
gas-liquid two-phase
refractive index matching
shadowgraphy
Bubble motion in a gas-liquid co-current flow through a porous structure is investigated. Bubble residence time, influence of the structure on the bubble motion, and influence of the buoyancy force acting on the bubble are determined to obtain a better understanding of the existing fluid dynamics in the porous structure. A variety of liquid flow rates (Re = 114-285) and volumetric transport fractions (? = 2.4, 3.2, and 4.1%) are taken into account. Measurements inside and at the outlet of the
structure are conducted and compared. The bubble motion is captured in a shadow imaging process, and overlapping bubble shadows are obtained. Therefore, a bubble-tracking algorithm is presented for the tracking of overlapping bubble shadows obtained by shadow imaging. The algorithm's matching criterion is based on similitude and proximity, and validated by running synthetic images. Errors
are estimated for varying gas holdup (bubble density) and bubble displacement between consecutive images. The influence of the frame rate on the tracking capability (matching of bubbles in consecutive images) and the underestimation of the bubble track by low temporal resolution are investigated.
EXPERIMENTAL INVESTIGATION OF THE MOTION OF A PAIR OF BUBBLES AT INTERMEDIATE REYNOLDS NUMBERS
51-66
10.1615/MultScienTechn.v27.i1.30
Hiroaki
Kusuno
Shizuoka University, Graduate School of Engineering, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan
Toshiyoki
Sanada
Shizuoka University, Faculty of Engineering, 3-5-1 Johoku, Naka-ku, Hamamatsu 432-8561, Japan
bubble-bubble interaction
wake
lift force
For the problem of bubble-bubble interaction at intermediate Reynolds numbers, some theoretical
models and direct numerical simulation results are available; however, experimental verifications are lacking. In this study, we observed the motion of a pair of bubbles, produced by an originally developed bubble generator, interacting in-line. The Reynolds numbers of the target bubbles ranged from 50 to 300. The bubble motions were observed using two high-speed video cameras, and their diameters were measured by a high-resolution digital still camera. Initially, the lift force acts on the trailing bubble owing to the wake of the leading bubble; the lift force causes the trailing bubble to
deviate from the vertical line to the leading bubble. The potential interaction then becomes dominant.
Finally, the trailing bubble approaches the leading bubble. This motion is completely different from
the particles motion in which the trailing particle is drafted toward the wake region of the leading
particle. In addition, it is shown that a slight difference in the diameter of the bubbles drastically
changes their interaction.
EFFECTS OF SUBCOOLING ON SOUND GENERATION BY VAPOR BUBBLES IN WATER
67-75
10.1615/MultScienTechn.v27.i1.40
Kosuke
Hayashi
Department of Mechanical Engineering, Graduate School Engineering, Kobe
University, 1-1 Rokkodai, Nada, Kobe, Hyogo, 657-8501 Japan
Masaya
Tateyama
NORITZ, 5 Minami Futami, Futami-cho, Akashi, 674-0093, Japan
Kazutaka
Ikeuchi
Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, 657-8501, Japan
Shigeo
Hosokawa
Faculty of Societal Safety Science, Kansai University, 7-1 Hakubai, Takatsuki,
Osaka 569-1098, Japan
Akio
Tomiyama
Department of Mechanical Engineering, Graduate School Engineering, Kobe
University, 1-1 Rokkodai, Nada, Kobe, Hyogo, 657-8501 Japan
Makoto
Hirotsu
NORITZ, 5 Minami Futami, Futami-cho, Akashi, 674-0093, Japan
Nobuhiro
Takeda
NORITZ, 5 Minami Futami, Futami-cho, Akashi, 674-0093, Japan
hydrodynamic sound
bubble
vapor
condensation
Sound generated by vapor bubbles condensing in subcooled water was measured to investigate effects of the degree, ΔT, of subcooling. Saturated steam from a boiler was injected into a horizontal water pipe flow through an orifice of 1 mm in diameter. The duct diameter was 16 mm and the Reynolds number of water was about 5 × 104. The subcooling was varied from 10 to 40 K. The sound level increased with increasing ΔT for ΔT ≤ 20 K, whereas it was independent of ΔT at higher ΔT. Video images of condensing bubbles revealed that the interfacial velocity of a condensing bubble had the same trend as that of the sound level, and therefore, the interfacial velocity in condensation is the key in the sound level. The rapid condensation at high ΔT induced emission of microbubbles and secondary pressure pulse generation. The latter also contributes to the increase in the sound level.
INFLUENCE OF TUBE DIAMETER ON CRITICAL HEAT FLUX IN DOWNWARD FLOW
77-97
10.1615/MultScienTechn.v27.i1.50
Takeyuki
Ami
Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680, Japan
Takayuki
Harada
Hisashi
Umekawa
Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680, Japan
Mamoru
Ozawa
Department of Safety Science, Kansai University, 7-1 Hakubai-cho, Takatsuki-shi, Osaka 569-1098, Japan
critical heat flux
downward flow
falling liquid film
flooding
hydraulic instability
liquid film dryout
Critical heat flux (CHF) is one of the key design factors for boiling heat transfer equipment. Thus, CHF, especially under upward flow condition, has been widely investigated, but the characteristics of CHF for downward flow are quite different from for upward flow. In downward flow, the complex flow structure is formed due to the counter force between the buoyancy and inertia. In view of thermal-hydraulic characteristics, downward flow should be avoided in boiling equipment. However, in a
research reactor, downward flow is applied as a simplified cooling method of the reactor core. The
objective of this investigation is to grasp the influence of the tube diameter on CHF in downward flow, because CHF in downward flow is closely related to the flow structure, which is influenced by the diameter and the flow velocity. The CHF experiment was carried out with a forced convective boiling system by using various inner diameter tubes in upward and downward flows. On the basis
of the obtained pressure drop of the test section, behavior of inlet fluid temperature, and the location of
CHF, the experimental CHF could be classified into four modes, i.e., complete dryout of falling liquid
film, CHF due to flooding, CHF caused by hydraulic instability, and liquid film dryout in annular
flow. These CHF are discussed by using the CHF model based on the regime-based modelling.