Begell House Inc.
Multiphase Science and Technology
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0276-1459
28
2
2016
AN ASSESSMENT OF THE CORRELATIONS FOR ENTRAINMENT AND DEPOSITION RATES IN ANNULAR FLOW FOR DRYOUT PREDICTION
99-133
10.1615/MultScienTechn.2017015681
Arnab
Dasgupta
Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai-400085, India
D. K.
Chandraker
Reactor Engineering Division, Bhabha Atomic Research Centre (BARC), Mumbai-400085, India; Homi Bhabha National Institute, Mumbai, India
S. P.
Walker
Department of Mechanical Engineering, Imperial College of Science Technology and Medicine, London, SW7 2AZ, United Kingdom
P. K.
Vijayan
Reactor Engineering Division, Bhabha Atomic Research Centre, Mumbai-400085, India
deposition
entrainment
correlations
dryout
The use of phenomenological modeling for the prediction of dryout is very attractive because it offers considerable flexibility and the ability to address a wide range of operating conditions. The approach requires knowledge of the rates of the droplet deposition and entrainment as its basic constituents. These rates are determined experimentally, with the experimental observations gathered and used in the form of correlations. Over the considerable period in which phenomenological modeling has been (and still is) under active development numerous measurements have been made and many correlations, correspondingly, have been developed. This presents the analyst or phenomenological code developer with the requirement to choose from among these many possibilities. The difficulty in this choice is compounded by the fact that it is desirable to choose correlations as a logically matched set rather than as independent entities in order to ensure that conditions associated with the correlations are as internally consistent as possible. We present here an attempt to identify suitable groupings of correlations and we compare their performance in predicting dryout against annular flow observations. The correlations are also compared to each other based on theoretical considerations and a framework is proposed through which the appropriateness of the parameters in a correlation can be judged. Finally, a preferred set of entrainment-deposition correlations among those studied is identified.
EXPERIMENTAL INVESTIGATION OF FLOW REGIME AND EFFICIENCY OF AIRLIFT PUMPS WITH TAPERED UPRISER PIPE
135-152
10.1615/MultScienTechn.2017018723
Hessam Eisazadeh
Zaraki
Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, P.O. Box: 11155-9567,
Azadi Avenue, Tehran, Iran
Mahdi
Majidniya
Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, P.O. Box: 11155-9567, Azadi Avenue, Tehran, Iran
Mehdi Hosseini
Abadshapoori
Center of Excellence in Energy Conversion, School of Mechanical Engineering, Sharif University of Technology, P.O. Box: 11155-9567, Azadi Avenue, Tehran, Iran
Mohammad Hassan
Saidi
Center of Excellence in Energy Conversion (CEEC), School of Mechanical Engineering, Sharif
University of Technology, P.O. Box 11155-9567, Tehran, Iran
flow regime
airlift pump
tapered upriser pipe
submergence ratio
pumping efficiency
Airlift pumps are simple devices using injected gas flow as the driving force for pumping liquids or a mixture of liquid and solid to higher levels. The pipe diameter, tapering angle of the upriser pipe, and submergence ratio are the most prominent parameters influencing the performance of airlift
pumps. In this study, the performance of an air–water two-phase flow airlift pump with a tapered upriser pipe of 6 m height and tapering angle of 0.67° with inlet and outlet diameters of 60 mm and 200 mm is investigated experimentally. Experimental measurements for different submergence ratios ranging from 0.55 to 0.82 are utilized to investigate the effect of using a tapered upriser on the airlift pumping efficiency and void fraction. The results show that pumping efficiency of a tapered airlift pump is up to 40% higher than a constant diameter upriser airlift pump. In addition, it is found that
the optimum level of submergence ratio for the tapered airlift pump is lower than the ordinary airlift pumps. The obtained improvement in pumping efficiency is described by illustrating the flow pattern map of the experimented airlift pump. It shows that the tapered upriser tends to keep the flow regime
in the slug flow region which is assumed to be the best flow regime for airlift pumps. The behavior of void fraction in three different cross-sectional areas of the tapered upriser is represented using a drift flux model. The results show the reduction of void fraction as the cross-sectional area increases along the tapered upriser length.
2D NUMERICAL SIMULATION OF SURFACE FLOW VELOCITY AND INTERNAL FLOW STRUCTURE GENERATED BY BUBBLES
153-171
10.1615/MultScienTechn.2017018926
Hassan
Abdulmouti
Department of Mechanical Engineering Division, Sharjah Men's College, Higher Colleges of Technology, P.O. Box 7946, Sharjah, United Arab Emirates
numerical simulation
Eulerian–Lagrangian model
surface flow
multiphase flow
bubble plume
The method of using a surface flow generated by a bubble plume is one of the effective ways to gather
materials floating on the surface in naval systems, lakes, seas, rivers, oceans, as well as in various
kinds of engineering processes handling a free surface. However, the generation process of the surface
flow has not been measured. The purpose of this research is to determine the horizontal velocity of the
free surface, which depends on the gas flow rate, bubble size, and internal two-phase flow structure
of the bubble plume. In this research, a two-dimensional (2D) numerical simulation based on the
Eulerian–Lagrangian model of the interaction between a vertical air bubble plume and a horizontal
free surface flow of water is performed. The results presented explore if the surface velocity profile can
be predicted by the Eulerian–Lagrangian model in good agreement with the results of experiments in
our previous paper. The maximum velocity of the surface flow increases as the bubble size supplied
increases. The surface flow is effectively generated in the case of the bubble plume compared to liquid
jet flow because the deflection (deviation) point appears in the vicinity of the surface.
COLLAPSE OF A TAYLOR BUBBLE AT A FREE SURFACE
173-191
10.1615/MultScienTechn.2017019092
Basanta Kumar
Rana
Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur 721302, India; School of Mechanical Engineering, KIIT Deemed to be University, Bhubaneswar-751024, India
Arup Kumar
Das
Department of Mechanical and Industrial Engineering, Indian Institute of
Technology, Roorkee,
Uttarakhand-247667, India
Prasanta Kumar
Das
Department of Mechanical Engineering, Indian Institute of Technology
Kharagpur, Kharagpur 721302, India
Taylor bubble
free surface
vertical film
total collapse time
cap film
Numerical simulations were performed to investigate the bursting of a Taylor bubble at a free surface
and the film drainage around the bubble for both vertical and inclined liquid columns. A wide range
of tube inclinations and variations of different fluid properties, such as the viscosity, density, and
surface tension, are used to establish the theory behind bubble bursting phenomenon. The volume
of fluid–based finite-volume formulation is used for the mass and momentum balance of the domain
and interface tracking. It was observed that film drainage around the bursting bubble increases for
fluids having high Morton numbers. In case of vertical tube, phenomenon is axisymmetric, but with
inclination of the tube, thickness increases in lower film than the liquid above the bubble. This gives
rise to an altogether different mechanism of bubble bursting inside the inclined tube and subsequently
affects the film drainage time. Finally, it was observed that in the case of an inclined tube the bubble
collapse takes more time at higher Morton numbers due to the formation of a spherical cap-type
envelope at the advancing front of the bubble.