Begell House Inc.
Multiphase Science and Technology
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22
1
2010
ANALYSIS OF PARTICLE INTERACTION WITH COHERENT STRUCTURES IN A TWO-PHASE MIXING JET
1-30
10.1615/MultScienTechn.v22.i1.10
R. K.
Decker
Faculty of Chemical Engineering, State University of Campinas, Cidade Universitaria "Zeferino Vaz," CP 6066, 13083-970, Campinas SP
H. F.
Meier
Department of Chemical Engineering, Regional University of Blumenau, Rua Sao Paulo 3250, 89030-000 Blumenau SC
M.
Mori
Faculty of Chemical Engineering, State University of Campinas, Cidade Universitaria "Zeferino Vaz," CP 6066, 13083-970, Campinas SP
Udo
Fritsching
Particles and Process Engineering Department, Faculty of Production
Engineering, University Bremen, Bibliothekstr. 1, 28359 Bremen, Germany; Leibniz Institute for Materials Engineering IWT, Badgasteiner Str. 3, 28359
Bremen, Germany
coherent structures
two-phase jet
particle cluster formation
interparticle arrival time
turbulence
Mixing processes of particulates such as droplets or solid particles with gases are an essential feature of typical chemical engineering processes. A proper analysis and design of the gas-particle mixing process enhances process qualities and efficiencies. In this contribution, an experimental study of the interaction of gas phase flow coherent structures with particles in a two-phase jet flow is presented. Radial profiles of particle mean velocities, particle sizes, rms velocities, turbulence intensities, and the “interparticle arrival time (IAT)†distribution have been investigated by means of phase Doppler anemometry. The experiments have been executed in a jet at different axial and radial distances from the nozzle. The variation of the initial velocity conditions, particle diameter distributions, and particle loadings yield important information about the local flow structures and their effect on the macroscopic as well as the turbulent particle transport between the jet center and the outer shear layer. The interparticle arrival time distribution proves to be an important tool to identify regions where large-scale coherent structures influence the particle distribution and tend to form particle clusters. The derived extensive experimental data set for the particle behavior in a two-phase jet may serve as a base for the detailed validation of numerical simulations of dispersed two-phase flow behavior, including strong phase interactions between gaseous and particulate phases.
INTRODUCTION TO THE SPECIAL ISSUE ON THE 5TH EUROPEAN-JAPANESE TWO-PHASE FLOW GROUP MEETING
31-32
10.1615/MultScienTechn.v22.i1.20
Gian Piero
Celata
ENEA, Institute of Thermal Fluid Dynamics, ENEA TERM/ISP Heat Transfer Laboratory C.R.E.
EXPERIMENTAL INVESTIGATIONS ON THE CONDENSATION OF STEAM BUBBLES INJECTED INTO SUBCOOLED WATER AT 1 MPA
33-55
10.1615/MultScienTechn.v22.i1.30
Dirk
Lucas
Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics,
Bautzner Landstraße 400, 01328 Dresden, Germany
M.
Beyer
Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, 01314 Dresden
L.
Szalinski
Forschungszentrum Dresden-Rossendorf e.V., Institute of Safety Research, P.O. Box 510 119, 01314 Dresden
bubble condensation
polydispersed flow
bubble size
pipe flow
experiment
CFD grade data
Bubble condensation plays an important role, e.g., in subcooled boiling or steam injection into pools. Since the condensation rate is proportional to the interfacial area density, bubble size distributions have to be considered in an adequate modeling of the condensation process. To develop and validate closure models for computational fluid dynamics codes, new experimental data are required. The effect of bubble sizes is clearly shown in experimental investigations done at the TOPFLOW facility of Forschungszentrum Dresden Rossendorf. Steam bubbles are injected into a subcooled upward pipe flow via orifices in the pipe wall located at different distances from the measuring plane. Injection orifices measuring 1 and 4 mm are used to vary the initial bubble size distribution. Variation of the distance between the location of the gas injection and the measuring plane allows investigation of the evolution of the flow along the pipe. Measurements are done using wire-mesh sensors and thermocouples. Condensation is clearly faster in the case of the injection via the smaller orifices, i.e., in case of smaller bubble sizes. Data on averaged void fraction, radial gas volume fraction profiles, profiles of the gas velocity, and bubble size distributions in dependency of the L/D ratio are presented in the paper.
VISUALIZATION OF TWO-PHASE FLOW PHENOMENA IN POLYMER ELECTROLYTE MEMBRANE FUEL CELLS BY NEUTRON RADIOGRAPHY
57-78
10.1615/MultScienTechn.v22.i1.40
Hideki
Murakawa
Department of Mechanical Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
Tadanobu
Ueda
Department of Mechanical Engineering, Kobe University
Katsumi
Sugimoto
Department of Mechanical Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
Hitoshi
Asano
Department of Mechanical Engineering, Kobe University, 1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501, Japan
Nobuyuki
Takenaka
Department of Mechanical Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan
polymer electrolyte fuel cell
neutron radiography
water behavior
network modeling
Water behavior in an operating polymer electrolyte fuel cell (PEFC) was visualized by using neu-
tron radiography, and the cell voltage and the pressure drop between the inlet and outlet of air were
simultaneously measured. The PEFC is compliant with Japan Automobile Research Institute (JARI)
standard PEFCs. An electrode area of 50×50 mm2 was visualized, and the cell temperature was kept
at 80°C. The effects of channel geometry, i.e., single- and triple-serpentine, relative humidity of air,
and current density, were investigated. From the experiments, it can be confirmed that fluctuation of
area-average water thickness in a triple-serpentine channel is larger than that in a single-serpentine
channel, and water in the channel is likely to accumulate at corners of the channel in the single-
serpentine channel. Furthermore, movement of condensed water is strongly related to cell voltage
and pressure drop. For a few minutes after the operation, the average thickness of water at the rib is
thicker than that at the channel. Furthermore, a network modeling to predict the gas-velocity distributions was proposed. Based on the water depth in the channel and the gas diffusion layer, gas-velocity
distributions were obtained. The pressure drops in single-phase flow were in good agreement with the
experimental results under low gas-flow rate. The model could predict the pressure drop based on the
water thickness in the PEFC.
DEVELOPMENT OF A NEW LARGE-FLOW-RATE AND EFFICIENT MIST GENERATOR, AND ITS APPLICATION TO AIR COOLING IN GREENHOUSES
79-93
10.1615/MultScienTechn.v22.i1.50
Michio
Sadatomi
Department or Advanced Mechanical System, Graduate School of Science and Technology, Kumamoto University, Kurokami 2-39-1, Chuo-Ku, Kumamoto City, 860-8555, Japan
Akimaro
Kawahara
Advanced Thermal and Fluid Energy System
Division of Industrial Fundamentals
Faculty of Advanced Science and Technology, Graduate School of Science and Technology, Kumamoto University, Chuo-ku,
Kurokami 2-39-1, Kumamoto, Japan
Kentarou
Fukamachi
Dept. of Mechanical System Engineering, Kumamoto University, Kumamoto, 860-8555
Fuminori
Matsuyama
Dept. of Mechanical System Engineering, Kumamoto University, Kumamoto, 860-8555; Dept. of Mechanical Engineering, Sasebo National College of Technology, Sasebo, 857-1193
Naoki
Tanaka
Dept. of Mechanical System Engineering, Kumamoto University, Kumamoto, 860-8555
mist generator
atomizer
large-flow-rate
air cooling
greenhouse
A new large-flow-rate mist generator of less energy consumption has been developed in this study. The mist generator is categorized as two-fluid-type, but no water pump is required if pressurized air alone is supplied because water is automatically suctioned by vacuum pressure arising behind a sphere or an orifice in the mist generator. Several types of mist generators with sphere or different orifice sizes, etc. have been produced and tested in order to find the best specifications. In the tests, mist generation rate, air supply rate, and air pressure at the inlet of the mist generator were measured to evaluate the pneumatic power which is needed to select an air source. From the ratio of the mist generation rate to the pneumatic power and the droplet size, the optimum type was determined. Furthermore, as an example of practical uses for the mist generator, air-cooling tests in a greenhouse were conducted in the daytime and evening, in midsummer as well as late fall. The test results in the daytime in midsummer showed that the room temperature in the house fell from 50 to 30C. These test results and the details of the mist generator are reported in this paper.
TWO-PHASE FLOW MALDISTRIBUTION IN A MINI-MANIFOLD SYSTEM
95-114
10.1615/MultScienTechn.v22.i1.60
Iztok
Zun
Laboratory for Fluid Dynamics and Thermodynamics, Faculty of Mechanical Engineering, University of Ljubljana, Askerceva 6, 1000 Ljubljana, Slovenia
Jurij
Gregorc
Laboratory for Fluid Dynamics and Thermodynamics, Faculty of Mechanical Engineering, University of Ljubljana, Slovenia
Matjaz
Perpar
Laboratory for Fluid Dynamics and Thermodynamics, Faculty of Mechanical Engineering, University of Ljubljana, Slovenia
two-phase flow
mini-manifold
flow regimes
phase separation
The flow distribution of air and water among the parallel vertical tubes of a manifold system was studied over a wide range of air and water flow rates. Data on a semicircle cross-section header of 1.22 mm hydraulic diameter and three T-junctions with the corresponding side arms of 0.61 mm hydraulic diameter are presented. The gas and liquid superficial velocity ranges were 0.02-40.0 and 0.08-6.0 m/s. The following discernible flow regimes were considered: bubbly, bubbly to slug, slug, semi-annular, and churn flow. There are systematic trends on phase separation that depend on flow regime and on the T-junction location.