Implementation of the Interfacial Area Transport Equation in TRACE for Boiling Two-Phase Flows PDF Download
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Author: Matthew Bernard
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Correctly predicting the interfacial area concentration is vital to the overall accuracy of the two-fluid model because the interfacial area concentration describes the amount of surface area that exists between the two-phases, and is therefore directly related to interfacial mass, momentum and energy transfer. The conventional method for specifying the interfacial area concentration in the two-fluid model is through flow regime-based empirical correlations coupled with regime transition criteria. However, a more physically consistent approach to predicting the interfaciala area concentration is through the interfacial area transport equation (IATE), which can address the deficiencies of the flow regime-based approach. Some previous studies have been performed to demonstrate the feasibility of IATE in developmental versions of the nuclear reactor systems analysis code, TRACE. However, a full TRACE version capable of predicting boiling two-phase flows with the IATE has not been established.Therefore, the current work develops a version of TRACE that is capable of predicting boiling two-phase flows using the IATE. The development is carried out in stages. First, a version of TRACE which employs the two-group IATE for adiabatic, vertical upward, air-water conditions is developed. An in-depth assessment on the existing experimental database is performed to select reliable experimental data for code assessment. Then, the implementation is assessed against the qualified air-water two-phase flow experimental data. Good agreement is observed between the experimental data for and the TRACE code with an average error of 9% for all conditions. Following the initial development, one-group IATE models for vertical downward and horizontal two-phase flows are implemented and assessed against qualified data. Finally, IATE models capable of predicting subcooled boiling two-phase flows are implemented. An assessment of the models shows that TRACE is capable of generating interfacial area concentration in subcooled boiling two-phase flows with the IATE and that heat transfer effects dominate the evolution of in these flows.In parallel to developing a TRACE version with the IATE capability, an extensive study is performed to improve the capabilities of the four-sensor conductivity probe. These include improvements in both the signal processing software and processing schemes. Furthermore, experiments are performed in 14 additional test conditions. These test conditions are strategically chosen to establish database in flow conditions where specific bubble interaction mechanisms in the IATE are highlighted. The data established in the experiments are used to further assess and validate the IATE models available in TRACE.
Author: Matthew Bernard
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Correctly predicting the interfacial area concentration is vital to the overall accuracy of the two-fluid model because the interfacial area concentration describes the amount of surface area that exists between the two-phases, and is therefore directly related to interfacial mass, momentum and energy transfer. The conventional method for specifying the interfacial area concentration in the two-fluid model is through flow regime-based empirical correlations coupled with regime transition criteria. However, a more physically consistent approach to predicting the interfaciala area concentration is through the interfacial area transport equation (IATE), which can address the deficiencies of the flow regime-based approach. Some previous studies have been performed to demonstrate the feasibility of IATE in developmental versions of the nuclear reactor systems analysis code, TRACE. However, a full TRACE version capable of predicting boiling two-phase flows with the IATE has not been established.Therefore, the current work develops a version of TRACE that is capable of predicting boiling two-phase flows using the IATE. The development is carried out in stages. First, a version of TRACE which employs the two-group IATE for adiabatic, vertical upward, air-water conditions is developed. An in-depth assessment on the existing experimental database is performed to select reliable experimental data for code assessment. Then, the implementation is assessed against the qualified air-water two-phase flow experimental data. Good agreement is observed between the experimental data for and the TRACE code with an average error of 9% for all conditions. Following the initial development, one-group IATE models for vertical downward and horizontal two-phase flows are implemented and assessed against qualified data. Finally, IATE models capable of predicting subcooled boiling two-phase flows are implemented. An assessment of the models shows that TRACE is capable of generating interfacial area concentration in subcooled boiling two-phase flows with the IATE and that heat transfer effects dominate the evolution of in these flows.In parallel to developing a TRACE version with the IATE capability, an extensive study is performed to improve the capabilities of the four-sensor conductivity probe. These include improvements in both the signal processing software and processing schemes. Furthermore, experiments are performed in 14 additional test conditions. These test conditions are strategically chosen to establish database in flow conditions where specific bubble interaction mechanisms in the IATE are highlighted. The data established in the experiments are used to further assess and validate the IATE models available in TRACE.
Author: Xia Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 196
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Book Description
Abstract: The current study focuses on providing a reliable computational fluid dynamics (CFD) tool for two-phase flow simulations, which is capable of capturing dynamic changes of interfacial structures and achieving accurate predictions of flow behaviors. A set of interfacial area transport equations (IATEs), which dynamically evaluates the interfacial area concentration, was successfully implemented into a CFD software package, namely, Fluent. The interfacial area concentration is a key parameter in modeling the interfacial transfer terms in the two-fluid model due to mechanical and thermal non-equilibrium between the two phases. Given the various flow regimes in two-phase flows, one-group IATE and two-group IATE developed in the literature were separately incorporated into the two-fluid model and subsequently validated under different flow conditions: liquid-liquid two-component bubbly; air-water bubbly, cap-bubbly, and churn-turbulent flows. Numerical results obtained from the two-fluid model incorporated with the IATE models were generally in good agreement with the experimental data. A set of adjustable model coefficients was also established for three-dimensional simulations when the influence of the lateral phase distribution in a circular flow channel on the one-group IATE model was considered. In addition, contributions of the bubble interaction mechanisms and interfacial forces to the phase distributions of two-phase flow were numerically investigated. It was observed that the lift force was significant for the phase distributions in gas-liquid two-phase flows; however it might cause convergence issues when large bubbles exist in the flow field of interest. Furthermore, a mathematical property, i.e., the well-posedness of the proposed one-dimensional three-field model with the two-group IATE model, was studied. The necessary condition to ensure well-posedness was obtained using characteristic analysis. The momentum flux parameters were introduced to help stabilize the proposed model.
Author: Yih-Yun Hsu
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 618
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Book Description
This book presents concise views of current theories on boiling and two-phase flow and on supercritical heat transfer. The mechanisms of these two modes of heat transfer are compared and contrasted. The theories propose to interpret the observed phenomena from a mechanistic viewpoint, with supporting correlations and equations. Each subsection includes a summary and reference list, and nomenclatures are provided for each major section.
Author: Justin D. Talley
Publisher:
ISBN:
Category :
Languages : en
Pages : 394
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Book Description
Author: S. Mostafa Ghiaasiaan
Publisher: Cambridge University Press
ISBN: 1316785300
Category : Technology & Engineering
Languages : en
Pages : 1322
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Book Description
Providing a comprehensive introduction to the fundamentals and applications of flow and heat transfer in conventional and miniature systems, this fully enhanced and updated edition covers all the topics essential for graduate courses on two-phase flow, boiling, and condensation. Beginning with a concise review of single-phase flow fundamentals and interfacial phenomena, detailed and clear discussion is provided on a range of topics, including two-phase hydrodynamics and flow regimes, mathematical modeling of gas-liquid two-phase flows, pool and flow boiling, flow and boiling in mini and microchannels, external and internal-flow condensation with and without noncondensables, condensation in small flow passages, and two-phase choked flow. Numerous solved examples and end-of-chapter problems that include many common design problems likely to be encountered by students, make this an essential text for graduate students. With up-to-date detail on the most recent research trends and practical applications, it is also an ideal reference for professionals and researchers in mechanical, nuclear, and chemical engineering.
Author: Kennard Callender
Publisher:
ISBN:
Category : Nuclear reactors
Languages : en
Pages : 368
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Book Description
"The two-fluid model is used in the current thermal-hydraulic system analysis codes to perform detailed assessment of nuclear reactor safety. One of the major shortcomings of the two-fluid model has been the lack of an accurate and dynamic closure relation for interfacial area concentration. The interfacial area transport equation has been successfully used to resolve this problem by dynamically predicting the evolution of the interfacial area concentration. However, only models applicable to vertical two-phase flow are currently available. The present study develops a one-dimensional interfacial area transport equation applicable to horizontal bubbly flow with a 90-degree bend"--Abstract, leaf iii.
Author: R.T. Lahey Jr.
Publisher: Elsevier
ISBN: 1483291383
Category : Technology & Engineering
Languages : en
Pages : 629
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Book Description
This volume covers the modern developments in boiling heat transfer and two-phase flow, and is intended to provide industrial, government and academic researchers with state-of-the-art research findings in the area of multiphase flow and heat transfer technology. Special attention is given to technology transfer, indicating how recent significant results may be used for practical applications. The chapters give detailed technical material that will be useful to engineers and scientists who work in the field of multiphase flow and heat transfer. The authors of all chapters are members of the CMR at Rensselaer, a research centre specializing in the state-of-the-art in multiphase science.
Author: L S Tong
Publisher: CRC Press
ISBN: 9781560324850
Category : Science
Languages : en
Pages : 582
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Book Description
Completely updated, this graduate text describes the current state of boiling heat transfer and two-phase flow, in terms through which students can attain a consistent understanding. Prediction of real or potential boiling heat transfer behaviour, both in steady and transient states, is covered to aid engineering design of reliable and effective systems.
Author: Theodore Worosz
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
To fully realize the benefit of the two-group interfacial area transport equation (IATE) as a constitutive model for the interfacial area concentration in the two-fluid model, it is imperative that models be developed to dynamically transition from one-group to two-group flows. With this in mind, the two-group IATE is derived in detail to establish new expansion source terms that correctly account for the effects of intergroup bubble transport. In addition to this theoretical effort, the state-of-the-art four-sensor conductivity probe is used to establish a reliable experimental database of local two-phase flow parameters to characterize one-group to two-group transition flows and to support model development. The experiments are performed in vertical-upward air-water two-phase flow in a 5.08cm pipe. Additionally, the local conductivity probe is improved through systematic studies into: 1) signal "ghosting" electrical interference among probe sensors, 2) sampling frequency sensitivity, 3) measurement duration sensitivity, and 4) probe sensor orientation. Wake-dominated bubble transport characterizes the transition from one-group to two-group flows. Therefore, the necessary intergroup and intragroup wake entrainment source terms that are required for two-group interfacial area transport in transition flows are developed. Furthermore, an approach is developed to initiate the shearing-off source and reduce the one-group interaction mechanisms as an established two-group flow develops. The new interfacial area transport model for one-group to two-group transition flows is evaluated against the experimental database. The model accurately captures the exchange of void fraction and interfacial area concentration between group-I and group-II in transition flows. Overall, the group-I void fraction and interfacial area concentration are predicted within ±6% and ±4%, respectively, of the experimental data. The group-II void fraction and interfacial area concentration are predicted within ±9% and ±11%, respectively, of the experimental data.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 15
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Book Description
In the two-fluid model for two-phase flows, interfacial area concentration is one of the most important closure relations that should be obtained from careful mechanistic modeling. The objective of this study is to develop a one-group interfacial area transport equation together with the modeling of the source and sink terms due to bubble breakage and coalescence. For bubble coalescence, two mechanisms are considered to be dominant in vertical two-phase bubbly flow. These are the random collisions between bubbles due to turbulence in the flow field, and the wake entrainment process due to the relative motion of the bubbles in the wake region of a seeding bubble. For bubble breakup, the impact of turbulent eddies is considered. These phenomena are modeled individually, resulting in a one-group interfacial area concentration transport equation with certain parameters to be determined from experimental data. Compared to the measured axial distribution of the interfacial area concentration under various flow conditions, these parameters are obtained for the reduced one-group, one-dimensional transport equation. The results indicate that the proposed models for bubble breakup and coalescence are appropriate.
