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Numerical Modeling Of Condensation From Vapor Gas Mixtures For Forced Down Flow Inside A Tube
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Book Synopsis Numerical Modeling of Condensation from Vapor-gas Mixtures for Forced Down Flow Inside a Tube by :
Download or read book Numerical Modeling of Condensation from Vapor-gas Mixtures for Forced Down Flow Inside a Tube written by and published by . This book was released on 1995 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Laminar film condensation is the dominant heat transfer mode inside tubes. In the present paper direct numerical simulation of the detailed transport process within the steam-gas core flow and in the condensate film is carried out. The problem was posed as an axisymmetric two dimensional (r, z) gas phase inside an annular condensate film flow with an assumed smooth interface. The fundamental conservation equations were written for mass, momentum, species concentration and energy in the gaseous phase with effective diffusion parameters characterizing the turbulent region. The low Reynolds number two equation [kappa]-[epsilon] model was employed to determine the eddy diffusion coefficients. The liquid film was described by similar formulation without the gas species equation. An empirical correlation was employed to correct for the effect of film waviness on the interfacial shear. A computer code named COAPIT (Condensation Analysis Program Inside Tube) was developed to implement numerical solution of the fundamental equations. The equations were solved by a marching technique working downstream from the entrance of the condensing section. COAPIT was benchmarked against experimental data and overall reasonable agreement was found for the key parameters such as heat transfer coefficient and tube inner wall temperature. The predicted axial development of radial profiles of velocity, composition and temperature and occurrence of metastable vapor add insight to the physical phenomena.
Book Synopsis Condensation from Vapor-gas Mixture for Forced Downflow Inside a Tube by : Ruey Yng Yuann
Download or read book Condensation from Vapor-gas Mixture for Forced Downflow Inside a Tube written by Ruey Yng Yuann and published by . This book was released on 1993 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Numerical Solution of a Two-phase Model for Laminar Film Condensation of Vapour-gas Mixtures in Channels by :
Download or read book Numerical Solution of a Two-phase Model for Laminar Film Condensation of Vapour-gas Mixtures in Channels written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present analysis deals with steady-state, internal-flow, laminar film condensation of vapour-gas mixtures in horizontal and downward-inclined parallel-plate channels. The cooled lower plate is maintained at a uniform temperature, while the upper plate is insulated. Saturated vapour mixed with a non-condensable gas enters the channel at prescribed pressure, velocity, and gas mass fraction. As a result of condensation on the lower plate, distinct regions of liquid condensate and vapour-gas mixture are formed inside the channel. Each phase is described with a set of complete boundary layer equations governing the conservation of mass, momentum, and energy. These two phases are related at the interface with the continuity of velocity, temperature, mass flux, shear stress, and heat flux. The focus of this thesis is on developing a robust numerical solution for the above model and assessing the effect of each independent parameter on the condensation process. The numerical approach utilized a variable-properties finite-volume method with a marching technique. (Abstract shortened by UMI.).
Book Synopsis Vertical Downflow Condensation Heat Transfer in Gas-steam Mixtures by : Daniel Grant Ogg
Download or read book Vertical Downflow Condensation Heat Transfer in Gas-steam Mixtures written by Daniel Grant Ogg and published by . This book was released on 1991 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Detailed Two-phase Modelling of Film Condensation on a Horizontal Tube by : Esam Saleh
Download or read book Detailed Two-phase Modelling of Film Condensation on a Horizontal Tube written by Esam Saleh and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete two-phase numerical model of film condensation from a mixture of a vapour and a non-condensing gas that is based on the two-dimensional elliptic governing equations with variable physical properties is presented. The model predicts the full viscous flow and heat and mass transfer for the mixture around the tube and in the entire liquid film from the top of the tube to the falling film below the tube. A finite volume method is used with a segregated solution approach and a dynamically moving computational grid that tracks the phase interface sharply. Fundamental balances of mass, energy, and force are enforced accurately at the phase interface. The model was developed in steps and validated against various experimental and theoretical works in the literature for different two-phase flows. The validation tests included stratified flow of liquid and gas in a horizontal channel, falling liquid film over a vertical wall, and condensation of steam from a steam-air mixture in a vertical channel. The model was used to simulate laminar film condensation from a downward flowing steam-air mixture over an isothermal horizontal tube. The validity of this new model is demonstrated by comparisons with previous theoretical and experimental studies. New results are presented on the effects of free-stream-to-tube temperature difference, upstream Reynolds number, free-stream gas mass fraction, and free-stream pressure on the condensate film development, the local and average heat transfer coefficients, and the total condensate mass flow rate. It was found that the temperature difference had the greatest effect on the condensation rate and film thickness. The presence of non-condensing gas in the vapour has a strong negative impact on the condensation process. For the pure steam case, moderate changes in the upstream Reynolds number showed slight increases in condensate mass flow rate with increased Reynolds number. For the mixture case, however, moderate increase in upstream Reynolds number increases significantly the condensate mass flow rate and film thickness. This trend becomes more noticeable as the free-steam gas mass fraction increases. Changing the free-stream pressure demonstrated that property variation had a relatively smaller effect than temperature difference and gas mass fraction changes.
Book Synopsis Numerical Solution of a Two-phase Model for Laminar Film Condensation of Vapour-gas Mixtures in Channels by :
Download or read book Numerical Solution of a Two-phase Model for Laminar Film Condensation of Vapour-gas Mixtures in Channels written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Buoyancy-Thermocapillary Convection of Volatile Fluids in Confined and Sealed Geometries by : Tongran Qin
Download or read book Buoyancy-Thermocapillary Convection of Volatile Fluids in Confined and Sealed Geometries written by Tongran Qin and published by Springer. This book was released on 2017-07-25 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis represents the first systematic description of the two-phase flow problem. Two-phase flows of volatile fluids in confined geometries driven by an applied temperature gradient play an important role in a range of applications, including thermal management, such as heat pipes, thermosyphons, capillary pumped loops and other evaporative cooling devices. Previously, this problem has been addressed using a piecemeal approach that relied heavily on correlations and unproven assumptions, and the science and technology behind heat pipes have barely evolved in recent decades. The model introduced in this thesis, however, presents a comprehensive physically based description of both the liquid and the gas phase. The model has been implemented numerically and successfully validated against the available experimental data, and the numerical results are used to determine the key physical processes that control the heat and mass flow and describe the flow stability. One of the key contributions of this thesis work is the description of the role of noncondensables, such as air, on transport. In particular, it is shown that many of the assumptions used by current engineering models of evaporative cooling devices are based on experiments conducted at atmospheric pressures, and these assumptions break down partially or completely when most of the noncondensables are removed, requiring a new modeling approach presented in the thesis. Moreover, Numerical solutions are used to motivate and justify a simplified analytical description of transport in both the liquid and the gas layer, which can be used to describe flow stability and determine the critical Marangoni number and wavelength describing the onset of the convective pattern. As a result, the results presented in the thesis should be of interest both to engineers working in heat transfer and researchers interested in fluid dynamics and pattern formation.
Book Synopsis An Investigation of Condensation from Steam-gas Mixtures Flowing Downward Inside a Vertical Tube by :
Download or read book An Investigation of Condensation from Steam-gas Mixtures Flowing Downward Inside a Vertical Tube written by and published by . This book was released on 1995 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Previous experiments have been carried out by Vierow, Ogg, Kageyama and Siddique for condensation from steam/gas mixtures in vertical tubes. In each case the data scatter relative to the correlation was large and there was not close agreement among the three investigations. A new apparatus has been designed and built using the lessons learned from the earlier studies. Using the new apparatus, an extensive new data base has been obtained for pure steam, steam-air mixtures and steam-helium mixtures. Three different correlations, one implementing the degradation method initially proposed by Vierow and Schrock, a second diffusion layer theory initially proposed by Peterson, and third mass transfer conductance model are presented in this paper. The correlation using the simple degradation factor method has been shown, with some modification, to give satisfactory engineering accuracy when applied to the new data. However, this method is based on very simplified arguments that do not fully represent the complex physical phenomena involved. Better representation of the data has been found possible using modifications of the more complex and phenomenologically based method which treats the heat transfer conductance of the liquid film in series with the conductance on the vapor-gas side with the latter comprised of mass transfer and sensible heat transfer conductance acting in parallel. The mechanistic models, based on the modified diffusion layer theory or classical mass transfer theory for mass transfer conductance with transpiration successfully correlate the data for the heat transfer of vapor-gas side. Combined with the heat transfer of liquid film model proposed by Blangetti, the overall heat transfer coefficients predicted by the correlations from mechanistic models are in close agreement with experimental values.
Book Synopsis Modeling of Mixed-convection Laminar Film Condensation from Mixtures of a Vapor and a Lighter Noncondensable Gas by : Vlajko Srzić
Download or read book Modeling of Mixed-convection Laminar Film Condensation from Mixtures of a Vapor and a Lighter Noncondensable Gas written by Vlajko Srzić and published by . This book was released on 1997 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Modeling of Mixed-convection Laminar Film Condensation from Mixtures of a Vapor and a Lighter Noncondensable Gas by :
Download or read book Modeling of Mixed-convection Laminar Film Condensation from Mixtures of a Vapor and a Lighter Noncondensable Gas written by and published by . This book was released on 1907 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The effects of a lighter noncondensable gas on laminar film condensation from moving vapor-gas mixtures was investigated. Condensation occurred on the top of an isothermal flat plate with an arbitrary inclination. The liquid film and the mixture boundary layers were described with the conservation equations for mass, momentum, energy, and gas species (for the mixture boundary layer only). A finite volume method was applied on a staggered grid in the numerical solution domain. The properties for both liquid and mixture were evaluated at the local temperature. The solution procedure was terminated either when the separation criteria were met or when the flow reached the transition to turbulence. The main objectives of the study were to investigate the mixture boundary layer separation distance and the reduction in heat transfer to the wall due to the presence of a lighter noncondensable gas. Three vapor-gas combinations were studied: steam-hydrogen, Freon12-air, and mercury-air. Applying two simple collapsing procedures, a set of graphs is presented for each vapor-gas combination which can be used to estimate the separation length for a given set of input parameters. For each mixture and for a given free stream temperature, the variation of Nusselt number (normalized by the square root of the local Reynolds number) along the plate is also presented for different values of gas concentration and wall temperature. (Abstract shortened by UMI.).
Book Synopsis Numerical Analysis of Reflux Condensation by : Foad Hassaninejadfarahani
Download or read book Numerical Analysis of Reflux Condensation written by Foad Hassaninejadfarahani and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reflux condensation occurs in a vertical tube when there is an upward core flow of vapour (or gas-vapour mixture) and a downward flow of the liquid film. The understanding of this condensation configuration is crucial in the design of reflux condensers and in loss-of-coolant safety analyses in nuclear power plant steam generators. A range of modelling approaches exists for co-current film condensation from gas-vapour mixtures in parallel-plate channels and tubes. These methods are based on marching from the inlet down the tube and do not apply to the reflux condensation. In this research, however, a two-dimensional two-phase model was developed that solves the steady, full elliptic governing equations in both the film and the gas-vapour core flow on a non-orthogonal mesh that dynamically adapts to the phase interface. Gas-vapour shear and heat and mass transfer at the interface were accounted for fundamentally. This modelling is a big step ahead of current capabilities by removing the limitations of previous reflux condensation models which inherently cannot account for the detailed local balances of shear, mass, and heat transfer at the phase interface. The model was developed and applied for co-current and counter-current flows in vertical parallel-plate channels, followed by vertical tubes. In each stage, the model results were compared against the available experimental and numerical data for validation purposes. A wide range of boundary conditions and geometries have been studied to examine the details of co-current and counter-current condensation phenomena. Velocity, temperature, pressure, and gas mass fraction profiles along with the axial variation of various parameters such as local Nusselt number, film thickness, interface and centre-line temperature and gas mass fraction are presented in parametric studies.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1995 with total page 888 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiannual, with semiannual and annual indexes. References to all scientific and technical literature coming from DOE, its laboratories, energy centers, and contractors. Includes all works deriving from DOE, other related government-sponsored information, and foreign nonnuclear information. Arranged under 39 categories, e.g., Biomedical sciences, basic studies; Biomedical sciences, applied studies; Health and safety; and Fusion energy. Entry gives bibliographical information and abstract. Corporate, author, subject, report number indexes.
Book Synopsis Heat Transfer in Condensation and Boiling by : Karl Stephan
Download or read book Heat Transfer in Condensation and Boiling written by Karl Stephan and published by . This book was released on 1992 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1970 with total page 796 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Non-equilibrium Evaporation and Condensation Processes by : Yuri B. Zudin
Download or read book Non-equilibrium Evaporation and Condensation Processes written by Yuri B. Zudin and published by Springer Nature. This book was released on 2021-02-27 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: This present book is concerned with analytical approaches to statement and solution of problems of non-equilibrium evaporation and condensation. From analytical solutions, one is capable to understand and represent in a transparent form the principal laws, especially in the study of a new phenomenon or a process. This is why analytical methods are always employed on the first stage of mathematical modeling. Analytical solutions are also used as test models for validation of results numerical solutions. Non-equilibrium evaporation and condensation processes play an important role in a number of fundamental and applied problems: laser methods for processing of materials, depressurization of the protection cover of nuclear propulsion units, solar radiation on a comet surface, explosive boiling of superheated liquid, thermodynamic principles of superfluid helium. Analytical relations provide an adequate description of the essence of a physical phenomenon.
Book Synopsis Numerical Solution for Turbulent Film Condensation from Vapor-gas Mixtures in Vertical Tubes by : Meghan K. Groff
Download or read book Numerical Solution for Turbulent Film Condensation from Vapor-gas Mixtures in Vertical Tubes written by Meghan K. Groff and published by . This book was released on 2005 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Desalination and Water Treatment by : Murat Eyvaz
Download or read book Desalination and Water Treatment written by Murat Eyvaz and published by BoD – Books on Demand. This book was released on 2018-09-19 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: The need for fresh water is increasing with the rapid growth of the world's population. In countries and regions with available water resources, it is necessary to ensure the health and safety of the water supply. However, in countries and regions with limited freshwater resources, priority is given to water supply plans and projects, among which the desalination strategy stands out. In the desalination process, membrane and thermal processes are used to obtain fresh water from salty water that is in abundant amounts in the sea. This book will outline valuable scientific contributions to the new desalination and water treatment technologies to obtain high quality water with low negative environmental impacts and cost. The editors would like to record their sincere thanks to the authors for their contributions.
