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2019
DYNAMIC SIMULATION OF PRESSURE DROP OSCILLATION IN GAS–LIQUID TWO-PHASE FLOW SYSTEM
1-16
10.1615/MultScienTechn.2018029467
Takeyuki
Ami
Department of Mechanical Engineering, Kansai University, 3-3-35 Yamate-cho, Suita-shi, Osaka 564-8680, Japan
Mayuho
Kitagawa
Department of Mechanical Engineering, Kansai University, Suita, Osaka
564-8680, Japan
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
pressure drop oscillation
flow mal-distribution
discrete bubble model
Flow instabilities, such as flow excursion, flow maldistribution, and pressure-drop oscillation, are
caused by the negative resistance of the pressure drop vs. flow rate characteristics in two-phase flow system, being rather classical issues in two-phase flow dynamics. Previous investigations were mainly based on lumped-parameter modellings, and thus distributed-parameter analyses were rather few because the occurrences of flow instabilities depend simply on whether the system has negative-resistance
characteristics. The negative-resistance instabilities are not limited in such boiling systems, and are often encountered in isothermal gas–liquid two-phase flow through mini channels. The present article describes such flow instabilities in an isothermal system. In mini- and microchannels, surface tension dominates the flow pattern formation, and the pressure drop characteristics
are affected accordingly so that the negative-resistance characteristics appear. The present investigation
focuses on the extension of the "discrete bubble model" developed by the authors. The present extended version of the model is applied to simulate the negative-resistance characteristics of the pressure drop, the pressure-drop oscillation, and the drastic flow maldistribution in an isothermal two-phase flow system. The static and dynamic behavior of two-phase flow in mini-channels is well
reproduced by the present numerical simulation, and the applicability of the model is verified through the comparison with existing experimental results.
PHASE DETECTION AIDED THERMOMETRY AND ITS APPLICATION TO NATURAL CONVECTIVE SUBCOOLED FLOW BOILING IN A NARROW GAP
17-25
10.1615/MultScienTechn.2018029446
Mao
Takeyama
Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku Kastura,
Nishikyo-Ku, Kyoto, 615-8540 Japan
Tomoaki
Kunugi
Department of Nuclear Engineering, Kyoto University, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto, Japan
Takehiko
Yokomine
Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Science, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580, JAPAN; Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku Kastura, Nishikyo-Ku, Kyoto, 615-8540 Japan
Zensaku
Kawara
Department of Nuclear Engineering, Kyoto University, Kyoto-Daigaku katsura, Nishikyo-ku, Kyoto, 615-8540, Japan
phase detection aided thermometry
miniature-thermocouple
natural convection
subcooled flow boiling
narrow gap
Since temperature and void (or phase) fraction are important parameters to characterize multi-phase flow behaviors, various methods to measure these quantities have been developed. However, these multi-phase flow parameters have not been simultaneously measured at the same time and position until the present because individual sensors, such as an optical fiber void sensor, a conductance probe, and a sheath thermocouple (TC) are needed. This article summarizes the development of the Phase Detection aided Thermometry (PDaT) to detect the phase for two-phase flow and simultaneously measure the liquid/gas temperature with a miniature TC with high temporal-spatial resolutions.
To demonstrate the applicability of PDaT, it was applied to the natural convective subcooled flow boiling in a narrow gap (1 mm) between a cylindrical heater rod and a transparent flat plate. This is a very simple model of a part of the subchannel of fuel rod bundle in a light water reactor core. It was confirmed that the PDaT is able to measure the temperature and void fraction simultaneously
and is a useful tool for two-phase flow characterization.
TWO-WAY COUPLED FLUID-STRUCTURE INTERACTION OF GAS-LIQUID SLUG FLOW IN A FLEXIBLE RISER: SMALL-SCALE EXPERIMENTS AND SIMULATIONS
27-43
10.1615/MultScienTechn.2019029489
Joaquin J.
Vieiro
Department of Energy and Process Engineering, Norwegian University of
Science and Technology, Trondheim, 7491, Norway
Anvar
Akhiiartdinov
School of Petroleum Engineering, The University of Tulsa, Tulsa, Oklahoma
74110, USA
Svein
Sævik
Department of Marine Technology, Norwegian University of Science and
Technology, Trondheim, 7491, Norway
Carl M.
Larsen
Department of Marine Technology, Norwegian University of Science and
Technology, Trondheim, 7491, Norway
Ole J.
Nydal
Department of Energy and Process Engineering, Norwegian University of
Science and Technology, Trondheim, 7491, Norway
slug flow
dynamic response
flexible riser
fluid-structure interaction
Flexible risers might be subjected to large pressure and density fluctuations when transporting multiphase mixtures as different flow patterns may take place. Those fluctuations might induce large forces on the structure, which in turn may modify the global geometry of the riser. In this paper, results from one-way and two-way coupled fluid-structure simulations are compared against small-scale
experiments of a flexible lazy wave riser transporting gas-liquid flow. Different gas flow rates are tested in order to obtain a range of slug frequencies. Predicted values of pipeline pressure, top tension, and riser displacement are compared with experimental data. The numerical prediction of
the coupled behavior shows fairly good agreement with the experiments, having bias from 5% to 25% in slug frequency.
EXPERIMENTAL INVESTIGATION OF HYDRODYNAMICS BEHAVIOR OF A SUBMERGED VENTURI SCRUBBER
45-59
10.1615/MultScienTechn.2019029434
Paridhi
Goel
Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094, Maharashtra, India; Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai 400085, Maharashtra, India
Avinash
Moharana
Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai
400085, Maharashtra, India
Arun Kumar
Nayak
Department of Engineering Sciences, Homi Bhabha National Institute, Anushakti Nagar, Mumbai 400094, Maharashtra, India; Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai-400085, India
FCVS
Venturi scrubber
hydrodynamics
pressure drop
throat gas velocity
An experimental study was conducted in a submerged Venturi scrubber having full-scale geometrical dimensions as the prototype reactor. The experiments were carried out at various pressure conditions, air flow rate, and submergence heights to simulate the hydrodynamics of a Venturi scrubber.
Measurements of two-phase axial pressure drop in the Venturi scrubber were made across a wide range of operating all the conditions. In all conditions, the pressure drop increased with increase in flow rate in the converging section and in the throat section after the entrainment of liquid in the
nozzles. However, in low pressure conditions in the diverging section was not recovered, unlike the high pressure conditions in previous measurements. The Venturi scrubber performance depends on the radial pressure difference across the nozzles located between the scrubbing pool and the throat of the Venturi, which creates liquid entrainment. The sizes and numbers of these droplets influence the scrubbing. The radial pressure difference between the Venturi throat and the scrubber tank at
the nozzles across the throat was more for higher submergence height (4.5 m) as compared to lower submergence height (4 m), and it decreased with increase in gas flow rate in the Venturi scrubber. A theoretical estimation of the liquid loading to the Venturi scrubber was made from the radial pressure difference measured across nozzles. From the calculated liquid loading and the gas flow rate as input,
the pressure drop across the Venturi scrubber was calculated using the models proposed by Calvert, Boll, and Hesketh. These calculated values did not correlate well with the experimental results.
HYDRODYNAMIC SOUND GENERATED BY COLLAPSE OF VAPOR BUBBLES IN SUBCOOLED LIQUID FLOW
61-71
10.1615/MultScienTechn.2019029476
Kosuke
Hayashi
Department of Mechanical Engineering, Graduate School Engineering, Kobe
University, 1-1 Rokkodai, Nada, Kobe, Hyogo, 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
noise
condensation
vapor bubble
microbubble
Sound generated by collapse of vapor bubbles injected into a subcooled water pipe flow was measured to investigate the effects of temperature gradient forming at the pipe wall on the sound level. The degree, ΔT, of subcooling was 20 K, the water velocity was 1.2 m/s, and the vapor was injected from a circular hole of 1 mm in diameter placed on the pipe wall. Water was heated just upstream of the test section to make ΔT non-uniform. The smaller ΔT due to heating made the noise level smaller. The noise level cannot be correlated in terms of the local ΔT at the bubble collapse event in spite of the rapid condensation, whereas the noise level with temperature gradient agrees with that of uniform ΔT by taking into account the temperature variation in the region from the vapor inlet to the position of collapse event.
MULTIDIMENSIONAL SIMULATION OF THERMAL NONEQUILIBRIUM FLOWS IN A CONVERGENT-DIVERGENT NOZZLE
73-85
10.1615/MultScienTechn.2019028624
Avick
Sinha
Indian Institute of Technology Bombay, Mumbai, India, 400076
Shivasubramanian
Gopalakrishnan
Department of Mechanical Engineering, IIT Bombay, Bombay-400076, India
converging-diverging nozzle
flashing
homogeneous relaxation model
two-phase
geothermal
The aim of this effort is to employ the homogeneous relaxation model to study thermal nonequilibrium in flash boiling flows. The use of convergent-divergent nozzles is prevalent in geothermal total flow systems for power generation, and the understanding of the physics of two-phase flows in such systems is of primary importance to achieve greater efficiencies. Most numerical studies for
such nonequilibrium phase-change models have used one dimensional approaches, but the objective of the present work is to utilize a multidimensional computational fluid dynamics implementation for such complex flows. It was observed that the slip between the vapor and liquid along the divergent section of the nozzle and the maximum nonequilibrium pressure drop at the nozzle throat due
to the thermal nonequilibrium causes an increase in the nozzle efficiency with the decrease in back pressure. The model was validated against experimental measurements and it was observed that the simulations are in good agreement with the multidimensional features observed in the experiments.
EFFECTS OF HEAT GENERATION, THERMAL RADIATION, AND HALL CURRENT ON MHD CASSON FLUID FLOW PAST AN OSCILLATING PLATE IN POROUS MEDIUM
87-107
10.1615/MultScienTechn.2019029514
Harshad R.
Patel
Applied Science and Humanities Department, Sardar Vallabhbhai Patel Institute
of Technology, Vasad, India
magnetohydrodynamic (MHD)
Casson fluid
porous medium
skin friction
Nusselt number
Sherwood number
The present study investigates the natural convection magnetohydrodynamic (MHD) flow of Casson fluid beyond an oscillating vertical plate in a rotating system. The characteristics of the thermal radiation, heat generation, Hall current, and chemical reaction are analyzed with ramped wall temperature. Using the Laplace transform technique, non-dimensional equations are solved. An expression for the velocity, temperature, and concentration profiles is acquired. The results of the isothermal temperature have been compared to find and understand the effect of the ramped wall temperature plate. The numerical values of the velocity, temperature, and concentration profiles are
provided graphically for numerous values of the pertinent parameter. It can be seen that the Hall current, permeability of the porous medium, thermal radiation, and heat generation parameter have a tendency to improve motion in both the x'- and z'-directions. For both the ramped and isothermal thermal plates, expressions for the Nusselt and Sherwood numbers are obtained and presented in
tabular form.