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Author: James Larry Morgan Publisher: ISBN: Category : Mechanical engineering Languages : en Pages : 0
Book Description
Using a tiltable steam condenser test section, the parametric effects of heat flux, non-condensable gas, promoter, condenser surface thermal resistance, and surface inclination were studied on a 3.18 mm thick flat copper plate and on 0.051 mm thick foils of copper and titanium. Any non-condensable gas concentration, however small, reduces the heat transfer coefficient significantly during dropwise condensation. Non-condensable gases also cause large surface temperature fluctuations, resulting in difficulties of accurately measuring heat transfer coefficients. The recorded data for the heat transfer coefficient of this experiment is lower than previous investigations, possibly due to a concentration of non-condensable gases which resulted from the low steam velocity past the condenser surface or due to the effects of the thin condenser surfaces used. With a vertical, copper surface, the heat transfer coefficient increases by a factor of five when the condenser surface thickness increases from 0.051 mm to 3.18 mm. The heat transfer coefficient is higher for dropwise condensation on copper than for titanium with mixed condensation. Surface inclination from the vertical position decreases the heat transfer coefficient by as much as 50 percent. (Author).
Author: James Larry Morgan Publisher: ISBN: Category : Mechanical engineering Languages : en Pages : 0
Book Description
Using a tiltable steam condenser test section, the parametric effects of heat flux, non-condensable gas, promoter, condenser surface thermal resistance, and surface inclination were studied on a 3.18 mm thick flat copper plate and on 0.051 mm thick foils of copper and titanium. Any non-condensable gas concentration, however small, reduces the heat transfer coefficient significantly during dropwise condensation. Non-condensable gases also cause large surface temperature fluctuations, resulting in difficulties of accurately measuring heat transfer coefficients. The recorded data for the heat transfer coefficient of this experiment is lower than previous investigations, possibly due to a concentration of non-condensable gases which resulted from the low steam velocity past the condenser surface or due to the effects of the thin condenser surfaces used. With a vertical, copper surface, the heat transfer coefficient increases by a factor of five when the condenser surface thickness increases from 0.051 mm to 3.18 mm. The heat transfer coefficient is higher for dropwise condensation on copper than for titanium with mixed condensation. Surface inclination from the vertical position decreases the heat transfer coefficient by as much as 50 percent. (Author).
Author: J. B. Dolloff Publisher: ISBN: Category : Languages : en Pages : 42
Book Description
The results of a study of the mechanism of dropwise condensation of steam at elevated pressures are presented. Equivalent heat transfer coefficients for dropwise condensation of steam were determined experimentally for pressures ranging from 0 to 142 psig. The results showed that for each Delta-Ts there is a pressure at which the film coefficient is a maximum and that this maximum increases slightly as Delta-Ts decreases. For a Delta-Ts of 10 and 20 F, the maximum heat transfer coefficient is 33,000 and 24,000 Btu/hr-sq. ft.-F respectively and lies in the pressure range 50-60 psig. It is believed that this maximum reflects the formation of a quasi-film of closely packed drops which offers considerable resistance to heat transfer. Photographic analysis of the dropwise condensation phenomena revealed that the combined effects of drop cycle time, free area available for condensation, and overall temperature driving force are the factors which cause a maximum in the equivalent heat transfer coefficient. A theoretical analysis is presented which is consistent with experimental observations. Also, photographs revealed that dropwise condensation was maintained for pressures up to 120 psig. (Author).
Author: W. H. Shafer Publisher: Springer Science & Business Media ISBN: 1468433814 Category : Science Languages : en Pages : 319
Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and dis seminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the ac tivity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volume were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 22 (thesis year 1977) a total of 10,658 theses titles from 28 Canadian and 227 United States universities. We are sure that this broader base for theses titles reported will greatly enhance the value of this important annual reference work. While Volume 22 reports theses submitted in 1977, on occasion, certain universities do report theses submitted in previous years but not reported at the time.
Author: Wade H. Shafer Publisher: Springer Science & Business Media ISBN: 1468436201 Category : Science Languages : en Pages : 306
Book Description
Masters Theses in the Pure and Applied Sciences was first conceived, published, and dis seminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the ac tivity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all concerned if the printing and distribution of the volume were handled by an international publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Corporation of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 23 (thesis year 1978) a total of 10,148 theses titles from 27 Canadian and 220 United States universities. We are sure that this broader base for theses titles reported will greatly enhance the value of this important annual reference work. While Volume 23 reports these submitted in 1978, on occasion, certain universities do report theses submitted in previous years but not reported at the time.
Author: J. T. O'Bara Publisher: ISBN: Category : Languages : en Pages : 27
Book Description
In the first phase of this work equivalent heat transfer coefficients at atmospheric pressure for the dropwise condensation of steam were determined experimentally. The coefficients rangef from 1,140 to 37,200 BTU/hr sq ft deg F for heat fluxes of 167,000 down to 29,900 BTU/hr sq ft deg F with surface temperature differences carying from 2 to 45F. Vapor velocities varied from 1.75 to 7.52 ft/sec. It was observed that the vapor velocity across the condensing surface has a significant effect on the equivalent transfer coefficient with the coefficient exhibiting a maximum with increasing vapor velocity. It is believed that this maximum reflects the transition between dropwise and mixed condensation resulting from the greater vapor-liquid interfacial shear stress developed at high vapor velocities. Visual observations showed that, as the pressure increases, a transition from dropwise to mixed condensation occurs between 25 and 50 psig. This transition is posited to be associated with the decreased surface tension of the condensed phase at the higher saturation temperatures. (Author).
Author: Sameer Khandekar Publisher: Springer Nature ISBN: 3030484610 Category : Science Languages : en Pages : 462
Book Description
This book is an expanded form of the monograph, Dropwise Condensation on Inclined Textured Surfaces, Springer, 2013, published earlier by the authors, wherein a mathematical model for dropwise condensation of pure vapor over inclined textured surfaces was presented, followed by simulations and comparison with experiments. The model factored in several details of the overall quasi-cyclic process but approximated those at the scale of individual drops. In the last five years, drop level dynamics over hydrophobic surfaces have been extensively studied. These results can now be incorporated in the dropwise condensation model. Dropwise condensation is an efficient route to heat transfer and is often encountered in major power generation applications. Drops are also formed during condensation in distillation devices that work with diverse fluids ranging from water to liquid metals. Design of such equipment requires careful understanding of the condensation cycle, starting from the birth of nuclei, followed by molecular clusters, direct growth of droplets, their coalescence, all the way to instability and fall-off of condensed drops. The model described here considers these individual steps of the condensation cycle. Additional discussions include drop shape determination under static conditions, a fundamental study of drop spreading in sessile and pendant configurations, and the details of the drop coalescence phenomena. These are subsequently incorporated in the condensation model and their consequences are examined. As the mathematical model is spread over multiple scales of length and time, a parallelization approach to simulation is presented. Special topics include three-phase contact line modeling, surface preparation techniques, fundamentals of evaporation and evaporation rates of a single liquid drop, and measurement of heat transfer coefficient during large-scale condensation of water vapor. We hope that this significantly expanded text meets the expectations of design engineers, analysts, and researchers working in areas related to phase-change phenomena and heat transfer.
Author: Publisher: Springer ISBN: 9783319266947 Category : Science Languages : en Pages : 0
Book Description
This Handbook provides researchers, faculty, design engineers in industrial R&D, and practicing engineers in the field concise treatments of advanced and more-recently established topics in thermal science and engineering, with an important emphasis on micro- and nanosystems, not covered in earlier references on applied thermal science, heat transfer or relevant aspects of mechanical/chemical engineering. Major sections address new developments in heat transfer, transport phenomena, single- and multiphase flows with energy transfer, thermal-bioengineering, thermal radiation, combined mode heat transfer, coupled heat and mass transfer, and energy systems. Energy transport at the macro-scale and micro/nano-scales is also included. The internationally recognized team of authors adopt a consistent and systematic approach and writing style, including ample cross reference among topics, offering readers a user-friendly knowledgebase greater than the sum of its parts, perfect for frequent consultation. The Handbook of Thermal Science and Engineering is ideal for academic and professional readers in the traditional and emerging areas of mechanical engineering, chemical engineering, aerospace engineering, bioengineering, electronics fabrication, energy, and manufacturing concerned with the influence thermal phenomena.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Abstract : The objective of this work is to identify the fundamental mechanism of dropwise condensation on a smooth solid surface by probing the solid-vapor interface during phase-change to evaluate the existence and structure of the thin film and the initial nucleus that develop during condensation. In this work, an automated Surface Plasmon Resonance imaging (SPRi) instrument with the ability to perform imaging in intensity modulation and angular modulation is developed. The SPRi instrument is used to probe (in three dimensions) the adsorbed film that forms on the substrate during dropwise condensation. SPRi with a lateral resolution of ~ 4-10 μm, thickness resolution of 0.1-1nm, and temporal resolution of 200-10,000 frames per second can measure water films that are monolayer to multilayer in thickness. The governing mechanism of dropwise condensation is investigated in detail for stable dropwise condensation on a smooth hydrophilic substrate. The study shows nucleation is the first step in dropwise condensation and no film greater than a monolayer exists between droplets during stable dropwise condensation. Our result confirms previous experimental works in support of nucleation theory as the mechanism of dropwise condensation. Our observation of unstable dropwise condensation of steam on a smooth hydrophilic surface shows presence of a several nanometers thick water film between droplets during dropwise condensation. This data matches with previous experimental work in support of film rupture theory. In summary, our results indicate nucleation theory or film rupture theory may be valid for special experimental settings. And, neither of these two theories are a comprehensive theory than can explain the physics of dropwise condensation.
Author: Mirza Mohammed Shah Publisher: John Wiley & Sons ISBN: 1119618673 Category : Science Languages : en Pages : 388
Book Description
A guide to two-phase heat transfer theory, practice, and applications Designed primarily as a practical resource for design and development engineers, Two-Phase Heat Transfer contains the theories and methods of two-phase heat transfer that are solution oriented. Written in a clear and concise manner, the book includes information on physical phenomena, experimental data, theoretical solutions, and empirical correlations. A very wide range of real-world applications and formulas/correlations for them are presented. The two-phase heat transfer systems covered in the book include boiling, condensation, gas-liquid mixtures, and gas-solid mixtures. The authora noted expert in this fieldalso reviews the numerous applications of two-phase heat transfer such as heat exchangers in refrigeration and air conditioning, conventional and nuclear power generation, solar power plants, aeronautics, chemical processes, petroleum industry, and more. Special attention is given to heat exchangers using mini-channels which are being increasingly used in a variety of applications. This important book: Offers a practical guide to two-phase heat transfer Includes clear guidance for design professionals by identifying the best available predictive techniques Reviews the extensive literature on heat transfer in two-phase systems Presents information to aid in the design and analysis of heat exchangers. Written for students and research, design, and development engineers, Two-Phase Heat Transfer is a comprehensive volume that covers the theory, methods, and applications of two-phase heat transfer.
Author: James Larry Morgan
Author: James Larry Morgan
Author: J. B. Dolloff
Author: W. H. Shafer
Author: Wade H. Shafer
Author: J. T. O'Bara
Author: Sameer Khandekar
Author: 
Author: 
Author: Salil Kumar Banerjee
Author: Mirza Mohammed Shah