Mathematical Model of Critical Heat Flux in Forced Convective Subcooled Boiling PDF Download

Author: Yung-Ji Tarng
Publisher:
ISBN:
Category : Critical flux
Languages : en
Pages : 132

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 19

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Book Description
Because of its practical importance and various industrial applications, the process of subcooled flow boiling has attracted a lot of attention in the research community in the past. However, the existing models are primarily phenomenological and are based on correlating experimental data rather than on a first-principle analysis of the governing physical phenomena. Even though the mechanisms leading to critical heat flux (CHF) are very complex, the recent progress in the understanding of local phenomena of multiphase flow and heat transfer, combined with the development of mathematical models and advanced Computational Fluid Dynamics (CFD) methods, makes analytical predictions of CHF quite feasible. Various mechanisms leading to CHF in subcooled boiling have been investigated. A new model for the predictions of the onset of CHF has been developed. This new model has been coupled with the overall boiling channel model, numerically implemented in the CFX 4 computer code, tested and validated against the experimental data of Hino and Ueda. The predicted critical heat flux for various channel operating conditions shows good agreement with the measurements using the aforementioned closure laws for the various local phenomena governing nucleation and bubble departure from the wall. The observed differences are consistent with typical uncertainties associated with CHF data.

Author: Ying T. Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 552

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Author: John Gordon Collier
Publisher: McGraw-Hill International Book Company
ISBN:
Category : Science
Languages : en
Pages : 474

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Book Description
On its original publication in 1973, this book was the first reference for engineers to fully present the science of boiling and condensation. It dealt especially with the problems of estimating heat transfer rates and pressure drops, with particular attention to the occurrence of boiling and condensation in the presence of forced flows within pipes. The new third edition was written primarily for design and development engineers in the chemical process, power generation, and refrigeration industries, and is meant to be an aid in the design of heat exchangers. It covers recent advances and significantly broadens coverage to flows over tube bundles, with extensive new treatment of two-phase heat transfer regarding refrigerants and petrochemicals. Many new problems have been added at the end of each chapter to enhance the book's use as a text in advanced courses on two-phase flow and heat transfer. Instructors using the book as a course text may obtain full solutions to the end-of-chapter problems by writing to: Science Marketing Dept., Oxford University Press, 198 Madison Avenue, New York, NY 10016 (please include school name and course identification), or by faxing (212) 726-6442.

Author: John C. Chen
Publisher: CRC Press
ISBN: 1000716031
Category : Science
Languages : en
Pages : 402

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Book Description
This book comprises selected papers from the First International Conference on Convective Flow Boiling. The purpose of the conference is to examine state-of-science and recent developments in technology of flow boiling, i.e., boiling systems which are affected by convective flows.

Author: Guan Heng Yeoh
Publisher:
ISBN: 9781604569438
Category : Fluid dynamics
Languages : en
Pages : 0

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Book Description
In the context of computational fluid dynamics (CFD), modelling low-pressure subcooled boiling flow is of particular significance. A review is provided in this book of the various numerical modelling approaches that have been adopted to handle subcooled boiling flow. The main focus in the analysis of such a challenging problem can be broadly classified according into two important categories: (i) Heat transfer and wall heat flux partitioning during subcooled boiling flow at the heated wall and (ii) Two-phase flow and bubble behaviours in the bulk subcooled flow away from the heated wall. For the first category, details of both empirical and mechanistic models that have been proposed in the literature are given. The enhancement in heat transfer during forced convective boiling attributed by the presence of both sliding and stationary bubbles, force balance model for bubble departure and bubble lift-off as well as the evaluation of bubble frequency based on fundamental theory depict the many improvements that have been introduced to the current mechanistic model of heat transfer and wall heat flux partitioning. For the second category, details of applications of various empirical relationships and mechanistic model such as population balance model to determine the local bubble diameter in the bulk subcooled liquid that have been employed in the literature are also given. A comparison of the predictions with experimental data is demonstrated. For the local case, the model considering population balance and improved wall heat partition shows good agreement with the experimentally measured radial distributions of the Sauter mean bubble diameter, void fraction, interfacial area concentration and liquid velocity profiles. Significant weakness prevails however over the vapor velocity distribution. For the axial case, good agreement is also achieved for the axial distributions of the Sauter mean bubble diameter, void fraction and interfacial area concentration profiles. The present model correctly represents the plateau at the initial boiling stages at upstream, typically found in low-pressure subcooled boiling flows, followed by the significant rise of the void fraction at downstream.

Author: Matthew Joseph Brusstar
Publisher:
ISBN:
Category :
Languages : en
Pages : 638

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Author: Bruce R. Springsteen
Publisher:
ISBN:
Category :
Languages : en
Pages : 498

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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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In this paper, a theoretical prediction of critical heat flux (CHF) during power transients in forced convective boiling is presented. The analysis is restricted to the departure from nucleate boiling (DNB) type of CHF at low qualities. The developed theory is compared with the experimental data available in the literature. The agreement is favorable. The results are discussed in terms of the various parameters affecting the transient CHF. This new model also is compared with the semi-empirical transient CHF model in the literature.

Author: S. Stephen Papell
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 28

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