Axial Development of Two-phase Flow Parameters in a Vertical Column

Axial Development of Two-phase Flow Parameters in a Vertical Column
Author: Kent C. Abel
Publisher:
Total Pages: 232
Release: 2002
Genre: Two-phase flow
ISBN:
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The next generation of nuclear safety analysis computer codes will include detailed modeling of the interfacial area concentration. The interfacial area concentration is the essence of the two-fluid model. It is the most accurate of the two-phase models since it considers each phase independently and links the two phases together with six conservation equations. The interfacial area concentration, along with a driving potential, determines the energy, momentum and mass transfer between the two phases. The importance of this research lies in obtaining a greater understanding of the developing nature of two-phase flows and the application of the two-fluid model. With proper characterization of two-phase flow, the next generation of nuclear safety analysis computer codes will be able to incorporate this information to predict parameters during an accident scenario with greater precision. This research will provide a first order look into the developing nature of two-phase flow. As part of this research, the development of two-phase flow in a vertical column was analyzed using double sensor impedance probes. The resident vapor and liquid times were recorded along with the velocity of the vapor phase. By creating distributions of the bubble residence times, liquid residence times, velocities, and sizes, one can characterize the developing nature of the two-phase flow. Data was taken at four different axial locations for six different flow rates. The resulting data show clear trends in how the standard deviation and mean values for the measured parameters change as a function of flow rate and axial position. The void fraction contribution from the spherical/distorted bubble group as well as the cap/slug bubble group was also recorded to determine the net transfer rate of vapor between the two bubble groups. Interfacial area concentration was not included in the measurement since the probes that were used can only determine interfacial area concentration for spherical bubbles. Further research will be conducted with the inclusion of interfacial area concentration at a later time.

Interfacial Area and Two-phase Flow Structure Development Measured by a Double-sensor Probe

Interfacial Area and Two-phase Flow Structure Development Measured by a Double-sensor Probe
Author:
Publisher:
Total Pages: 126
Release: 1992
Genre:
ISBN:
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In this report, we studied the local phasic characters of dispersed flow regime both at the entrance and at the fully developed regions. Since the dispersed phase is distributed randomly in the medium and enclosed in relatively small interfaces, the phasic measurement becomes difficult to obtain. Local probe must be made with a miniaturized sensor in order to reduce the interface distortion. The double-sensor resistivity probe has been widely used in local void fraction and interface velocity measurements because the are small in comparison with the interfaces. It has been tested and proved to be an accurate local phasic measurement tool. In these experiments, a double-sensor probe was employed to measure the local void fraction and interface velocity in an air-water system. The test section was flow regime can be determined by visualization. Furthermore, local phasic measurements can be verified by photographic studies. We concentrated our study on the bubbly flow regime only. The local measurements were conducted at two axial locations, L/D = 8 and 60, in which the first measurement represents the entrance region where the flow develops, and the second measurement represents the fully developed flow region where the radial profile does not change as the flow moves along the axial direction. Four liquid flow rates were chosen in combination with four different gas injection rates. The superficial liquid velocities were j{sub t} = 1.0, 0.6,0.4, and 0.1 m/s and superficial gas velocities were j{sub g} = 0.0965, 0.0696, 0.0384, and 0.0192 m/s. These combinations put the two-phase flow well in the bubbly flow regime. In this sequence of phenomenological studies, the local void fraction, interface area concentration, sauter mean diameter, bubble velocity and bubble frequency were measured.

Annular Two-Phase Flow

Annular Two-Phase Flow
Author: Geoffrey Hewitt
Publisher: Elsevier
Total Pages: 327
Release: 2013-10-22
Genre: Technology & Engineering
ISBN: 1483285235
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Annular Two-Phase Flow presents the wide range of industrial applications of annular two-phase flow regimes. This book discusses the fluid dynamics and heat transfer aspects of the flow pattern. Organized into 12 chapters, this book begins with an overview of the classification of the various types of interface distribution observed in practice. This text then examines the various regimes of two-phase flow with emphasis on the regions of occurrence of the annular flow regime. Other chapters consider the single momentum and energy balances, which illustrate the differences and analogies between single- and two-phase flows. This book discusses as well the simple modes for annular flow with consideration to the calculation of the profile of shear stress in the liquid film. The final chapter deals with the techniques that are developed for the measurement of flow pattern, entrainment, and film thickness. This book is a valuable resource for chemical engineers.

Single- and Two-Phase Flow Pressure Drop and Heat Transfer in Tubes

Single- and Two-Phase Flow Pressure Drop and Heat Transfer in Tubes
Author: Afshin J. Ghajar
Publisher: Springer Nature
Total Pages: 280
Release: 2022-01-11
Genre: Science
ISBN: 3030872815
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The book provides design engineers an elemental understanding of the variables that influence pressure drop and heat transfer in plain and micro-fin tubes to thermal systems using liquid single-phase flow in different industrial applications. It also provides design engineers using gas-liquid, two-phase flow in different industrial applications the necessary fundamentals of the two-phase flow variables. The author and his colleagues were the first to determine experimentally the very important relationship between inlet geometry and transition. On the basis of their results, they developed practical and easy to use correlations for the isothermal and non-isothermal friction factor (pressure drop) and heat transfer coefficient (Nusselt number) in the transition region as well as the laminar and turbulent flow regions for different inlet configurations and fin geometry. This work presented herein provides the thermal systems design engineer the necessary design tools. The author further presents a succinct review of the flow patterns, void fraction, pressure drop and non-boiling heat transfer phenomenon and recommends some of the well scrutinized modeling techniques.

Advances in Two-Phase Flow and Heat Transfer

Advances in Two-Phase Flow and Heat Transfer
Author: Sadik Kakaç
Publisher: Springer Science & Business Media
Total Pages: 465
Release: 2012-12-06
Genre: Science
ISBN: 9400968450
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Over the past two decades, two-phase flow and heat transfer problems associated with two-phase phenomena have been a challenge to many investigators. Two-phase flow applications are found in a wide range of engineering systems, such as nuclear and conventional power plants, evaporators of refrigeration systems and a wide vari ety of evaporative and condensive heat exchangers in the chemical industry. This publication is based on the invited lectures presented at the NATO Advanced Research Workshop on the Advances in Two-Phase Flow and Heat Transfer. The Horkshop was attended by more than 50 leading scientists and practicing engineers who work actively on two-phase flow and heat transfer research and applications in dif ferent sectors (academia, government, industry) of member countries of NATO. Some scientific leaders and experts on the subject matter from the non-NATO countries were also invited. They convened to discuss the state-of-the-art in two-phase flow and heat transfer and formulated recommendations for future research directions. To achieve these goals, invited key papers and a limited number of contributions were presented and discussed. The specific aspects of the subject were treated in depth in the panel sessions, and the unresolved problems identified. Suitable as a practical reference, these volumes incorporate a systematic approach to two-phase flow analysis.

Geometric Effects of Flow Restrictions and Configurations on Interfacial Structures in Two-phase Flow

Geometric Effects of Flow Restrictions and Configurations on Interfacial Structures in Two-phase Flow
Author: Mohan Singh Yadav
Publisher:
Total Pages: 193
Release: 2009
Genre:
ISBN:
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This study investigates the geometric effects of flow restrictions and flow configurations on two-phase flow parameters. Experiments are conducted in two distinct experimental setups employing different flow configurations and flow restrictions. In the first experiment, comparison of the effects of 90-degree and 45-degree elbows on interfacial structures and their transport characteristics in horizontal two-phase bubbly flow is investigated. The setup is made out of 50.3 mm inner diameter glass tubes and a double-sensor conductivity probe is used to collect time averaged local data. Experimental results show that both elbows have significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of two elbows. While the effect of the 45-degree elbow is evident immediately after the elbow, the 90-degree elbow effect is propagated further downstream of the elbow. Moreover, it is shown that both the elbows induce oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillation differ. Comparison of the elbow effect on the axial transport of two-phase flow parameters is also investigated. The second set of experiments is performed in combinatorial two-phase flow facility to study the effects of 90-degree vertical elbow and geometric configuration on two-phase bubbly flow. The elbow has a significant effect on two-phase flow regime transition boundaries at measurement locations downstream of the elbow. Modified two-phase flow regime maps based on the extensive flow visualization studies are suggested for both vertical and horizontal test sections. A four-sensor conductivity probe is employed to measure time averaged two-phase local parameters as the flow develops along vertical upward to horizontal section across the 90-degree vertical elbow. The elbow causes the bubbles to align along the horizontal radius of the pipe cross-section, creating a bi-peaked profile in void fraction and interfacial area concentration. One dimensional transport of area averaged two-phase flow parameters shows that the elbow promotes bubble interaction mechanism.