Phenomena of flooding with condensation PDF Download

Author: Chi-Kou Fan
Publisher:
ISBN: 9780444860002
Category :
Languages : en
Pages : 0

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Author: Ahmed Husham Mahmood
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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During a loss of coolant accident in a pressurised water reactor, emergency core cooling water is introduced via the downcomer annulus. The water may have to penetrate or overcome steam formed in the vessel due to the depressurisation. A typical counter-current flow situation can be created and dependent on the relative flow rates water may be prevented from reaching the reactor core with serious consequences. This,thesis considers the events leading up to this occurrence in a vertical, 54.75 mm diameter, 1 m long, stainless steel tube, to represent and provide a basic understanding of the situation occurring during a loss of coolant accident. Results are presented for air-water and steam-water flows with emphasis on the experimental and theoretical studies of the steam-water flow situation where direct contact heat transfer occurs. The air-water flooding data are shown to be well represented by a Wallis type flooding correlation. The steam-water flooding data are found to lie above the corresponding air-water data with their characteristic dependent on the water inlet subcooling. The percentage of the air/steam flow extracted with the water flow at the bottom porous sinter was found to exert a negative effect on the flooding phenomena. A theoretical model was developed to predict the liquid film thickness along the tube, and agreement with the experimental results demonstrated. A second theoretical model was developed to evaluate the temperature across the liquid film and along the test tube and from this model, the effective turbulent diffusivity was evaluated, leading to an estimate of the turbulent viscosity of the film under conditions in which substantial condensation took place. A semi-empirical model based on a linear stability analysis of a uniform liquid film and a counter-current flow of steam, was developed and modified for accelerating film flows. This model is shown to be capable of dealing with the steam-water flooding situation since reasonable agreement with the air-water flooding data is obtained. A modified Wallis type flooding correlation based on the experimental data, and accounting for non-equilibrium effect on flooding, is presented and discussed. A visualisation technique was developed and used to determine the flooding location in the section.

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

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Countercurrent two-phase flow and flooding phenomena are of great importance in connection with nuclear reactor safety and also a variety of industrial applications. A number of studies have been performed, both analytically and experimentally, which have generated various useful models and empirical correlations. However, the scatter of the data is rather large, partly because of the different definitions of flooding which have been employed, and partly because of the strong influence of the entrance and exit conditions. In an effort to resolve these discrepancies, the characteristics of the flooding and associated phenomena are derived in this work in a systematic way, and viewpoints on the onset of flooding are classified and examined. In general, flooding models may be roughly classified as surface wave stability theories, static equilibrium theories, envelope or limiting-operation theories and slug formation theories. These models, as well as some empirical correlations are compared on a common basis with a variety of data. Similarities and differences between flooding in flows with and without condensation are discussed. In addition, various parametric effects, such as fluid properties, tube diameter and length, tube end conditions and entrainment, are described. Finally, directions for future research are indicated.

Author:
Publisher: DIANE Publishing
ISBN: 1428914331
Category :
Languages : en
Pages : 59

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Author: G.F. Hewitt
Publisher: Springer Science & Business Media
ISBN: 3662016575
Category : Science
Languages : en
Pages : 495

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This is the second volume of Multiphase Science and TechnoJogy, a new international series of books intended to provide authoritative overviews of im portant areas in multiphase systems. The alm is to have systematic and tutorial presentations of the state of knowledge in various areas. The objective of the chapters is to allow the nonspecialist reader to gain an up-to-date idea of the present state of development in a given subject. The response to Volume 1 of the se ries has been very positive, and we believe that the present volume will be equally weil received. Volume 1 was concerned entirely with gas-liquid systems, and the first four chapters of the present volume also relate to such systems. However, the inten tion of the se ries is to cover a wide range of multiphase systems, and we are, therefore, pleased to include in the present volume chapters that refer to liquid liquid and gas-solid multiphase flows, respectively. The first chapter in the present volume is by Professor A. E. Dukler of the University of Houston, Texas, and Professor Y. Taitel of Tel-Aviv University, Israel.

Author: Institute of Medicine
Publisher: National Academies Press
ISBN: 0309091934
Category : Science
Languages : en
Pages : 369

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Almost all homes, apartments, and commercial buildings will experience leaks, flooding, or other forms of excessive indoor dampness at some point. Not only is excessive dampness a health problem by itself, it also contributes to several other potentially problematic types of situations. Molds and other microbial agents favor damp indoor environments, and excess moisture may initiate the release of chemical emissions from damaged building materials and furnishings. This new book from the Institute of Medicine examines the health impact of exposures resulting from damp indoor environments and offers recommendations for public health interventions. Damp Indoor Spaces and Health covers a broad range of topics. The book not only examines the relationship between damp or moldy indoor environments and adverse health outcomes but also discusses how and where buildings get wet, how dampness influences microbial growth and chemical emissions, ways to prevent and remediate dampness, and elements of a public health response to the issues. A comprehensive literature review finds sufficient evidence of an association between damp indoor environments and some upper respiratory tract symptoms, coughing, wheezing, and asthma symptoms in sensitized persons. This important book will be of interest to a wide-ranging audience of science, health, engineering, and building professionals, government officials, and members of the public.

Author: Sydney Ross
Publisher:
ISBN:
Category : Condensation
Languages : en
Pages : 10

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Author: Cold Regions Research and Engineering Laboratory (U.S.)
Publisher:
ISBN:
Category : Cold regions
Languages : en
Pages : 388

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

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Two flow instabilities which limit the normal condensation processes in countercurrent stratified steam-water flow have been identified experimentally: flooding and condensation-induced waterhammer. In order to initiate condensation-induced waterhammer in nearly horizontal or moderately-inclined steam/subcooled-water flow, two conditions, the appearance of a wavy interface and complete condensation of the incoming steam, are necessary. Analyses of these conditions are performed on a basis of flow stability and heat transfer considerations. Flooding data for several inclinations and channel heights are collected. Effects of condensation, inclination angle and channel height on the flooding characteristics are discussed. An envelope theory for the onset of flooding in inclined stratified flow is developed, which agrees well with the experimental data. Some empirical information on basic flow parameters, such as mean film thickness and interfacial friction factor required for this theory are measured. The previous viewpoints on flooding appear not to conflict with the present experimental data in nearly horizontal flow but the flooding phenomena in nearly vertical flow appear to be more complicated than those described by these viewpoints because of liquid droplet entrainment.

Author: F. B. Cheung
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 80

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