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Takashi Hibiki - One of the best experts on this subject based on the ideXlab platform.
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bubble breakup and coalescence models for bubbly flow simulation using Interfacial Area transport equation
International Journal of Heat and Mass Transfer, 2018Co-Authors: Takashi HibikiAbstract:Abstract This paper provides the state-of-the-art critical review on the modeled source and sink terms of the one-group Interfacial Area transport equation. The reviewed source and sink terms include models developed by Wu et al., Hibiki and Ishii, Hibiki et al., Yao and Morel, Park et al., Hibiki et al., Kataoka et al., Nguyen et al., Shen and Hibiki and Hazuku et al. The present critical review assesses major issues in modeling the one-group source and sink terms. Important conclusions are that the existing source and sink terms are not well-validated for developing and transient flows and the applicability of the source and sink terms to high pressure conditions such as prototypic nuclear reactor conditions has not been well-discussed. In view of these, coefficients of the source and sink terms in Hibiki and Ishii’s model have been modified for their application to prototypic nuclear reactor conditions. In addition, approximated Area-averaged source and sink terms due to turbulent diffusion and lateral migration are derived by Area-averaging local source and sink terms due to turbulent diffusion and lateral migration developed by Kataoka et al. The role of the Area-averaged source and sink terms due to turbulent diffusion and lateral migration on the Interfacial Area transport should be tested in a future study. This paper also overviews important model validation challenges to be addressed in a future study. The challenging model validation should address the model performance for various test sections and flow conditions. They are (1) the effect of channel size (small (or micro/mini)-to-large channels) on the Interfacial Area transport, (2) the scalability of the Interfacial Area transport equation to prototypic nuclear reactor conditions, (3) the effect of covariance due to phase distribution on the Interfacial Area transport, (4) the effect of inlet conditions on the Interfacial Area transport, (5) the applicability of the Interfacial Area transport equation to transient and developing flow conditions, and (6) the applicability of the Interfacial Area transport equation to various flow channels including a rod bundle.
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one dimensional Interfacial Area transport for bubbly two phase flow in vertical 5 5 rod bundle
International Journal of Heat and Fluid Flow, 2018Co-Authors: Hang Liu, Takashi Hibiki, Liangming Pan, Wenxiong Zhou, Quanyao RenAbstract:Abstract For the modeling of the Interfacial structure characteristics, an experiment of vertical adiabatic air-water flow has been conducted under an atmosphere pressure condition. The experimental facility is composed of 5 × 5 rods arranged on a square pitch in a square casing with 9.5 mm outside rod diameter and 12.6 mm pitch, simulating a prototypic rod bundle in nuclear reactors. The miniaturized four-sensor conductivity probe has been developed to allow for the experimental measurement in the small flow channel. Extensive data are acquired for one-dimensional flow parameters including axial development of void fraction, Interfacial Area concentration and gas velocity. The effect of a prototypic spacer grids with mixing vanes on the flow structure has been discussed at various flow conditions based on the experimental data. Two competing effects, “swirling effect” and “bubble breaker effect”, are identified. The effect vanishes out within a short distance from the space grid. A drift-flux correlation is developed for predicting void fraction of adiabatic bubbly two-phase flow in a vertical rod bundle. Existing Interfacial Area correlations are tested and Hibiki-Ishii correlation (2002b) is recommended as most accurate correlation to predict the Interfacial Area concentration. It is expected that the newly obtained data in the 5 × 5 rod bundle is useful for developing the Interfacial Area transport equation and benchmarking a computational code.
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modeling and validation of Interfacial Area transport equation in subcooled boiling flow
Journal of Nuclear Science and Technology, 2016Co-Authors: Caleb S Brooks, Takashi HibikiAbstract:The first comprehensive validation of the Interfacial Area transport equation in subcooled boiling is presented and shown to perform exceptionally when compared with experimental data. The formulation and closure of the bubble layer averaged Interfacial Area transport equation is reviewed along with the treatment of the two-fluid model in subcooled boiling. Interfacial Area concentration source and sink terms in subcooled boiling are presented including the bubble interaction mechanisms (random collision and turbulent impact), as well as phase change terms (wall nucleation and condensation). Additionally, the volume source terms from phase change are described and discussed in terms of their significance to the Interfacial Area transport equation. The validation of the Interfacial Area transport equation with a recently proposed wall nucleation source term is shown to have excellent prediction at low and elevated pressure, as well as a wide range of mass flux. With new confidence in the wall nucleation so...
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a correlation for Interfacial Area concentration in high void fraction flows in large diameter channels
Chemical Engineering Science, 2015Co-Authors: Joshua P Schlegel, Takashi HibikiAbstract:Abstract Two phase flows exist as a part of many industrial processes, including chemical processes, nuclear reactor systems, and heat exchangers. In all of these applications the Interfacial Area concentration is an important parameter for evaluating the interactions between the phases, including drag forces, heat transfer or chemical reaction rates. Many models for Interfacial Area concentration exist for dispersed bubbly flows; however this type of flow only exists at relatively low void fractions. Very few correlations exist for the prediction of cap-turbulent, slug, or churn-turbulent flows. In this paper a new correlation for predicting the Interfacial Area concentration beyond bubbly flows in large diameter pipes is derived using a two-bubble-group method (spherical and distorted bubbles as Group-1 bubbles and cap and churn-turbulent bubbles as Group-2 bubbles) and the two-group Interfacial Area transport equation. The derivation assumes steady state and fully developed flow, and is based on Interfacial Area transport source and sink terms for large diameter pipes developed by Smith et al., 2012a . Int. J. Heat Fluid Flow 33, 156–167. The resulting equations can be used to predict the void fraction for each group of bubbles and the Sauter mean diameter for each group of bubbles in addition to the total Interfacial Area concentration. The model is then benchmarked based on the data collected by Schlegel et al., 2012. Exp. Therm. Fluid Sci. 41, 12–22; Schlegel et al., 2014. Int. J. Heat Fluid Flow 47, 42–56. It is found that the correlation predicts the data for Sauter mean diameter of Group 1 bubbles with RMS error of 23.3% and bias of +1.83%. For Group 2 bubbles the RMS error is 24.0% and the bias is +5.35%. This indicates that the correlation somewhat over-predicts the bubble sizes. In spite of this the prediction error remains reasonable compared to the accuracy of previous correlations, and given that the experimental uncertainty can be as high as 15% for some flow conditions. The RMS error and bias in the total Interfacial Area concentration are 22.6% and −4.29%, respectively. This is consistent with the over-prediction of the Sauter mean diameters, but again is reasonable considering the experimental uncertainty and the prediction error of previous correlations. The model is also able to predict the trends found in the experimental data with varied liquid and gas velocities, representing a large improvement over previous modeling efforts. An expanded database of accurate Interfacial Area concentration measurements at higher pressures would allow further improvement of the model benchmark and expansion of the range of applicability of the model.
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databases of Interfacial Area concentration in gas liquid two phase flow
Progress in Nuclear Energy, 2014Co-Authors: Chihhung Lin, Takashi HibikiAbstract:Abstract Extensive literature review has been performed to provide the most updated information on local Interfacial Area measurements. The review begins with a brief introduction of various available experimental techniques which have been utilized for Interfacial Area measurement. Since the local sensor probe method is the most widely utilized technique, the basic concepts of this method are discussed. A deficiency in the mathematical formulation converting Interfacial velocity information into Interfacial Area concentration information is pointed out. The correct mathematical formulation is properly introduced and some pre-cautions are recommended for when measured Interfacial Area concentration is utilized for benchmarking the Interfacial Area transport equations and 1D and 3D thermo-fluid dynamic simulation codes. Extensive literature review has been conducted to identify available Interfacial Area data. The flow conditions of the available data include adiabatic and diabatic conditions, various channel geometries such as round channel, annulus channel, rectangular channel, subchannel, and rod bundles, elevated pressure conditions, various channel size conditions, wide-range flow regime conditions, and normal gravity and microgravity conditions. In spite of tremendous efforts devoted in the past 30 years, further systematic experimental effort is essential to establish solid experimental databases for benchmarking the Interfacial Area transport equations and 1D and 3D thermo-fluid dynamic codes.
Mamoru Ishii - One of the best experts on this subject based on the ideXlab platform.
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axial Interfacial Area transport and flow structure development in vertical upward bubbly and slug flow
International Journal of Heat and Mass Transfer, 2021Co-Authors: Guanyi Wang, Zhuoran Dang, Muhao Zhang, Mamoru IshiiAbstract:Abstract To improve the Interfacial Area transport equation model in the bubbly to slug transition flow, experiments are performed using the four-sensor conductivity probe for upward bubbly and slug flow in a 25.4 mm ID pipe. A total of 24 flow conditions are measured at 3 different superficial liquid velocities ranging from 0.5 m/s to 2.0 m/s and 8 different void fractions ranging from 0.1 to 0.6. The axial development of flow profiles is analyzed for bubbly flow, bubble-to-slug transition flow, and slug flow. In addition, the velocity effects on fully developed flow structures are also explained and the probe results are verified using the flow visualization. One-dimensional Interfacial Area transport due to bubble coalescence and disintegration is presented and its dependence on void fraction and velocity are discussed. These data provide one of the few quantitative results of the velocity effect on flow structure development at the same void fraction.
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experimental study on Interfacial structure and Interfacial Area transport in downward two phase flow
International Journal of Heat and Mass Transfer, 2017Co-Authors: Guanyi Wang, Mamoru Ishii, Xiaohong Yang, Zhuoran Dang, Andrew Ireland, Stephen M Bajorek, Matthew BernardAbstract:Abstract In view of the importance of two-group Interfacial Area transport equation and lack of corresponding accurate downward flow database that can reveal two-group Interfacial Area transport, a systematic database for adiabatic, air-water, vertical downward two-phase flow in a round pipe with inner diameter of 25.4 mm was collected to gain an insight of Interfacial structure and provide benchmarking data for two-group Interfacial Area transport model. Four-sensor conductivity probes were used to measure the local two phase flow parameters at high data sampling frequency to ensure the accuracy. Axial development of local flow parameter profiles including void fraction, Interfacial Area concentration, and Sauter mean diameter were presented. Drastic inter-group transfer of void fraction and Interfacial Area as well as the wall peaked Interfacial Area concentration profiles were observed and discussed.
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experimental study of Interfacial Area transport in air water two phase flow in a scaled 8 8 bwr rod bundle
International Journal of Multiphase Flow, 2013Co-Authors: Xiaohong Yang, Takashi Hibiki, Sidharth Paranjape, Joshua P Schlegel, Yang Liu, Mamoru IshiiAbstract:Abstract In order to accurately predict nuclear reactor behavior, the ability to predict the transfer of mass, momentum and energy between the phases in two-phase flows, whether in the Reactor Pressure Vessel (RPV) or steam generator, is essential. A significant component of this prediction is the Area available for transfer per unit volume, called the Interfacial Area concentration. Current thermal-hydraulic system analysis code predictions use empirical models to predict the Interfacial Area concentration; however accuracy and reliability can be improved through the use of an Interfacial Area Transport Equation (IATE). The IATE requires rigorously developed models for sources and sinks due to bubble interactions or phase change and an extensive database to validate those models. To provide this database, experiments using electrical conductivity probes to measure the Interfacial Area concentration at several axial positions have been performed in an 8 × 8 rod bundle which was carefully scaled from an actual BWR rod bundle.
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modeling and measurement of Interfacial Area concentration in two phase flow
Nuclear Engineering and Design, 2010Co-Authors: Sidharth Paranjape, Mamoru Ishii, Takashi HibikiAbstract:Abstract This paper presents experimental and modeling approaches in characterizing Interfacial structures in gas–liquid two-phase flow. For the modeling of the Interfacial structure characterization, the Interfacial Area transport equation proposed earlier has been studied to provide a dynamic and mechanistic prediction tool for two-phase flow analysis. A state-of-the-art four-sensor conductivity probe technique has been developed to obtain detailed local Interfacial structure information in a wide range of flow regimes spanning from bubbly to churn-turbulent flows. Newly obtained Interfacial Area data in 8 × 8 rod-bundle test section are also presented. This paper also reviews available models of the Interfacial Area sink and source terms and existing databases. The Interfacial Area transport equation has been benchmarked using condensation bubbly flow data.
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Interfacial Area transport equation and implementation into two fluid model
Journal of Thermal Science and Engineering Applications, 2009Co-Authors: Mamoru Ishii, Takashi HibikiAbstract:A dynamic treatment of Interfacial Area concentration has been studied over the last decade by employing the Interfacial Area transport equation. When coupled with the two-fluid model, the Interfacial Area transport equation replaces the flow regime dependent correlations for Interfacial Area concentration and eliminates potential artificial bifurcation or numerical oscillations stemming from these static correlations. An extensive database has been established to evaluate the model under various two-phase flow conditions. These include adiabatic and heated conditions, vertical and horizontal flow orientations, round, rectangular, annulus, and 8 X 8 rod-bundle channel geometries, and normal-gravity and reduced-gravity conditions. Currently, a two-group Interfacial Area transport equation is available and applicable to comprehensive two-phase flow conditions spanning from bubbly to churn-turbulent flow regimes. A framework to couple the two-group Interfacial Area transport equation with the modified two-fluid model is established in view of multiphase computational fluid dynamics code applications as well as reactor system analysis code applications. The present study reviews the current state-of-the-art in the development of the Interfacial Area transport equation, available experimental databases, and the analytical methods to incorporate the Interfacial Area transport equation into the two-fluid model.
Mark L Brusseau - One of the best experts on this subject based on the ideXlab platform.
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low concentration tracer tests to measure air water Interfacial Area in porous media
Chemosphere, 2020Co-Authors: Mark L BrusseauAbstract:Abstract The aqueous-based Interfacial tracer method employing miscible-displacement tests is one method available for measuring air-water Interfacial Areas. One potential limitation to the method is the impact of tracer-induced drainage on the system. The objective of this study was to investigate the efficacy of a low-concentration tracer test method for measuring air-water Interfacial Area. Tracer concentrations and analytical methods were selected that allowed the use of tracer input concentrations that were below the threshold of tracer-induced drainage. Multiple tracer tests were conducted at different water saturations. Interfacial Areas increased from 34.8 to 101 cm−1 with the decrease in saturation from 0.86 to 0.62. The method produced relatively robust measurements of air-water Interfacial Area, with coefficients of variation ranging from 6 to 26%. A variably saturated flow and transport model that accounts for the effects of tracer on Interfacial tension, and the retention of tracer at the air-water and solid-water interfaces, was used to test for potential tracer-induced drainage. The simulations showed that the use of low tracer-input concentrations eliminated this phenomenon. This is consistent with the measured data for effluent-sample masses, which exhibited minimal change during the tests, and with the observation that the Interfacial Areas obtained with the low-concentration-tracer method were consistent with values measured with two methods that are not influenced by tracer-induced drainage. These results demonstrate that the low-concentration miscible-displacement tracer test method is an effective approach for measuring air-water Interfacial Areas in porous media.
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Pore-Scale Modeling of Fluid-Fluid Interfacial Area in Variably Saturated Porous Media Containing Microscale Surface Roughness.
Water resources research, 2019Co-Authors: Hao Jiang, Bo Guo, Mark L BrusseauAbstract:A pore-scale model is developed to simulate fluid-fluid Interfacial Area in variably saturated porous media, with a specific focus on incorporating the effects of solid-surface roughness. The model is designed to quantify total (film and meniscus) fluid-fluid Interfacial Area (Anw ) over the full range of wetting-phase fluid saturation (Sw ) based on the inherent properties of the porous medium. The model employs a triangular pore space bundle of cylindrical capillaries (BCC) framework, modified with three surface roughness-related parameters. The first parameter (surface roughness factor) represents the overall magnitude of surface roughness, whereas the other two parameters (interface growth factor and critical adsorptive film thickness) reflect the micro-scale structure of surface roughness. A series of sensitivity analyses was conducted for the controlling variables, and the efficacy of the model was tested using air-water Interfacial Area data measured for three natural porous media. The model produced good simulations of the measured Anw data over the full range of saturation. The results demonstrate that total Interfacial Areas for natural media are typically much larger than those for ideal media comprising smooth surfaces due to the substantial contribution of surface roughness to wetting-film Interfacial Area. The degree to which fluid-fluid Interfacial Area is influenced by roughness is a function of fluid-retention characteristics and the nature of the rough surfaces. The full impact of roughness may be masked to some degree due to the formation of thick wetting films, which is explicitly quantified by the model. Application of the model provides insight into the importance of the interplay between pore-scale distribution and configuration of wetting fluid and the surface properties of solids.
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relationships among air water Interfacial Area capillary pressure and water saturation for a sandy porous medium
Water Resources Research, 2006Co-Authors: Mark L Brusseau, Sheng Peng, G Schnaar, Molly S CostanzarobinsonAbstract:[1] The relationships among air-water Interfacial Area, capillary pressure, and water saturation were investigated for a sandy, natural porous medium. Air-water Interfacial Areas as a function of water saturation were measured using two methods, gas phase partitioning tracer tests and synchrotron X-ray microtomography. The tracer test method provides a measure of effective total (capillary and film) Interfacial Area, whereas microtomography can be used to determine both capillary-associated and total Areas (the latter is the focus of this study). Air-water Interfacial Areas determined with both methods increased continuously with decreasing water saturation. The Areas measured with the tracer test method were significantly larger than those obtained from microtomography. The maximum values measured with the tracer test method approached the N2/BET-measured specific solid surface Area, whereas the maximum values measured by microtomography approached the smooth-sphere-calculated specific solid surface Area. The Interfacial Area-saturation data were combined with capillary pressure-saturation data obtained from water drainage experiments to examine the relationship between total air-water Interfacial Area and capillary pressure. Air-water Interfacial Area was observed to increase monotonically with increasing capillary pressure and then to plateau at values that correspond to Areas associated with residual water saturation. These results are consistent with previously reported theoretically and computationally based analyses of functional relationships between total nonwetting-wetting Interfacial Area and capillary pressure.
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relationships among air water Interfacial Area capillary pressure and water saturation for a sandy porous medium
Water Resources Research, 2006Co-Authors: Mark L Brusseau, Sheng Peng, G Schnaar, Molly S CostanzarobinsonAbstract:[1] The relationships among air-water Interfacial Area, capillary pressure, and water saturation were investigated for a sandy, natural porous medium. Air-water Interfacial Areas as a function of water saturation were measured using two methods, gas phase partitioning tracer tests and synchrotron X-ray microtomography. The tracer test method provides a measure of effective total (capillary and film) Interfacial Area, whereas microtomography can be used to determine both capillary-associated and total Areas (the latter is the focus of this study). Air-water Interfacial Areas determined with both methods increased continuously with decreasing water saturation. The Areas measured with the tracer test method were significantly larger than those obtained from microtomography. The maximum values measured with the tracer test method approached the N2/BET-measured specific solid surface Area, whereas the maximum values measured by microtomography approached the smooth-sphere-calculated specific solid surface Area. The Interfacial Area-saturation data were combined with capillary pressure-saturation data obtained from water drainage experiments to examine the relationship between total air-water Interfacial Area and capillary pressure. Air-water Interfacial Area was observed to increase monotonically with increasing capillary pressure and then to plateau at values that correspond to Areas associated with residual water saturation. These results are consistent with previously reported theoretically and computationally based analyses of functional relationships between total nonwetting-wetting Interfacial Area and capillary pressure.
M. Ishii - One of the best experts on this subject based on the ideXlab platform.
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investigation of one dimensional Interfacial Area transport for vertical upward air water two phase flow in an annular channel at elevated pressures
Nuclear Engineering and Design, 2013Co-Authors: Basar Ozar, Takashi Hibiki, Caleb S Brooks, Dongjin Euh, M. IshiiAbstract:Abstract The Interfacial Area transport of vertical, upward, air–water two-phase flows in an annular channel has been investigated at different system pressures. The inner and outer diameters of the annular channel were 19.1 mm and 38.1 mm, respectively. Twenty three inlet flow conditions were selected, which covered bubbly, cap-bubbly, and churn-turbulent flows. These flow conditions also overlapped with twelve conditions of a previous study for comparison. The local flow parameters, such as void fractions, Interfacial Area concentrations (IAC), and bubble interface velocities, were measured at nine radial positions for the three axial locations and converted into Area-averaged parameters. The axial evolutions of local flow structure were interpreted in terms of bubble coalescence, breakup, expansion of the gas-phase due to pressure drop and system pressure. An assessment of Interfacial Area transport equation (IATE) was made and compared with the experimental data. A discussion of the comparison between model prediction and the experimental results were made.
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mechanistic modeling of Interfacial Area transport in large diameter pipes
International Journal of Multiphase Flow, 2012Co-Authors: T R Smith, Takashi Hibiki, Joshua P Schlegel, M. IshiiAbstract:Abstract Flow in large pipes is important in a wide variety of applications. In the nuclear industry in particular, understanding of flow in large diameter pipes is essential in predicting the behavior of reactor systems. This is especially true of natural circulation Boiling Water Reactor (BWR) designs, where a large-diameter chimney above the core provides the gravity head to drive circulation of the coolant through the reactor. The behavior of such reactors during transients and during normal operation will be predicted using advanced thermal-hydraulics analysis codes utilizing the two-fluid model. Essential to accurate two-fluid model calculations is reliable and accurate computation of the Interfacial transfer terms. These Interfacial transfer terms can be expressed as the product of one term describing the potential driving the transfer and a second term describing the available surface Area for transfer, or Interfacial Area concentration. Currently, the Interfacial Area is predicted using flow regime-dependent semi-empirical correlations; however the Interfacial Area concentration is best computed through the use of the one-dimensional Interfacial Area transport equation (IATE). To be useful in practical applications the IATE requires mechanistic models for the change in Interfacial Area concentration due to interactions between bubbles. Therefore using previously collected data and proper scaling methods, current models for bubble interactions for the IATE are briefly discussed and new models applicable to large pipes are developed and compared with the existing data.
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Interfacial Area concentration in gas liquid bubbly to churn turbulent flow regime
International Journal of Heat and Fluid Flow, 2012Co-Authors: Basar Ozar, Takashi Hibiki, Abhinav Dixit, S W Chen, M. IshiiAbstract:Abstract There are very few established correlations to predict the Interfacial Area concentration beyond the bubbly flow regime in cap-slug and churn-turbulent flow regimes. Present study shows a systematic approach to estimate the Interfacial Area concentration in bubbly, cap-slug and churn-turbulent flow regimes. Ishii and Mishima’s (1980) formulation and the two group approach for categorizing bubbles (Group-1: spherical or distorted bubble, Group-2: cap bubble) are used to estimate the Interfacial Area concentration. The key parameters in this framework are the estimation of Group-1 bubble size and the amount of void in the liquid slug, which is a function of Group-1 void fraction. Hibiki and Ishii’s (2002) correlation is utilized to predict the size of the Group-1 bubbles. A correlation is developed to estimate the Group-1 void fraction. The developed model for the estimation of Interfacial Area concentration is compared with the three existing datasets. These are data for air–water flow taken in annular geometry and round tube and also for air–NaOH solution taken in round tube. The estimation accuracies for these data sets are ±36.4%, ±26.5% and ±37.4%, respectively. These datasets cover a wide range of flow regimes and different physical properties.
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Interfacial Area transport of vertical upward air water two phase flow in an annulus channel
International Journal of Heat and Fluid Flow, 2008Co-Authors: Jae Jun Jeong, Takashi Hibiki, Basar Ozar, Abhinav Dixit, J E Julia, M. IshiiAbstract:Abstract An experimental study on the Interfacial Area transport (IAT) of vertical, upward, air–water two-phase flows in an annulus channel has been conducted. The inner and outer diameters of the annular channel were 19.1 mm and 38.1 mm, respectively. Nineteen inlet flow conditions were selected, which cover bubbly, cap–slug, and churn–turbulent flows. The local flow parameters, such as void fraction, Interfacial Area concentration (IAC), and bubble interface velocity, were measured at nine radial positions for the three axial locations ( z / D H = 52, 149 and 230). The radial and axial evolutions of local flow structure were interpreted in terms of bubble coalescence and breakup. The measured data can be used for the development of the bubble coalescence/breakup models for the IAT model and some closure models for computational fluid dynamics.
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Two-Fluid Models and Interfacial Area Transport in Microgravity Condition
2004Co-Authors: M. Ishii, Shilp VasavadaAbstract:The objective of the present study is to develop a two-fluid model formulation with Interfacial Area transport equation applicable for microgravity conditions. The new model is expected to make a leapfrog improvement by furnishing the constitutive relations for the Interfacial interaction terms with the Interfacial Area transport equation, which can dynamically model the changes of the Interfacial structures. In the first year of this three-year project supported by the U.S. NASA, Office of Biological and Physics Research, the primary focus is to design and construct a ground-based, microgravity two-phase flow simulation facility, in which two immiscible fluids with close density will be used. In predicting the two-phase flow behaviors in any two-phase flow system, the Interfacial transfer terms are among the most essential factors in the modeling. These Interfacial transfer terms in a two-fluid model specify the rate of phase change, momentum exchange, and energy transfer at the interface between the two phases. For the two-phase flow under the microgravity condition, the stability of the fluid particle interface and the Interfacial structures are quite different from those under normal gravity condition. The flow structure may not reach an equilibrium condition and the two fluids may be loosely coupled such that the inertia terms of each fluid should be considered separately by use of the two-fluid model. Previous studies indicated that, unless phase-interaction terms are accurately modeled in the two-fluid model, the complex modeling does not necessarily warrant an accurate solution.
Dibyendu Mukherjee - One of the best experts on this subject based on the ideXlab platform.
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bubble size distribution and gas liquid Interfacial Area in a modified downflow bubble column
Chemical Engineering Journal, 2006Co-Authors: Subrata Kumar Majumder, Gautam Kundu, Dibyendu MukherjeeAbstract:Abstract Bubble size distribution and the gas–liquid specific Interfacial Area were measured as a function of axial location, nozzle diameter and superficial liquid and gas velocities in a modified bubble column reactor. The experimental measurements of bubble size and its distribution are analyzed with distribution model to gain insight into the breakup and coalescence mechanisms taking place. Axial profile of bubble number flux was estimated based on size distribution model incorporated with coalescence phenomena. Also correlation for Sauter mean bubble diameter has been developed with operating variables.
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a comparative study of gas holdup bubble size distribution and Interfacial Area in a downflow bubble column
Chemical Engineering Research & Design, 2005Co-Authors: Ajay Mandal, Gautam Kundu, Dibyendu MukherjeeAbstract:Experimental investigations have been carried out in an ejector induced downflow bubble column with special emphasis on gas holdup, bubble size distribution and Interfacial Area. Bubble diameters have been measured by photographic and capillary method at different operating conditions. Bubble sizes are found to have a logarithmic-normal probability distribution for any axial positions of the column. Sauter mean bubble diameters have been used along with overall gas holdup to get the geometric Interfacial Area and the results are compared with the Interfacial Area obtained by chemical method. Experiments are carried out with air–water system in bubbly flow regime. Absorption of carbon dioxide in aqueous sodium hydroxide solution has been adopted to measure Interfacial Area by chemical method. The discrepancies in Interfacial Area obtained by the two methods are found to be consistent with reported works.