Download or read book The Numerical Study of a Dropwise Condensation Mode when Cooling Heat Transfer Surfaces written by and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study on Condensation Heat Transfer of Trapezoid Grooved Surfaces written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Drop Dynamics and Dropwise Condensation on Textured Surfaces written by Sameer Khandekar and published by Springer Nature. This book was released on 2020-09-11 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Dropwise Condensation of Water and Low Surface Tension Fluids on Structured Surfaces written by Yajing Zhao (S.M.) and published by . This book was released on 2018 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Condensation is a ubiquitous process often observed in nature and our daily lives. The large amount of latent heat released during the condensation process has been harnessed in many industrial processes such as power generation, building heating and cooling, desalination, dew harvesting, thermal management, and refrigeration. Condensation has two modes: dropwise mode and filmwise mode. Although it has been known for decades that dropwise condensation outperforms filmwise condensation in heat transfer owing to the droplet shedding effects which can efficiently reduce thermal resistance, filmwise condensation still dominates industrial applications currently due to the high costs, low robustness and technical challenges of manufacturing dropwise coatings. During water condensation, dropwise mode can be readily promoted with thin hydrophobic coatings. Superhydrophobic surfaces made out of hydrophobic coatings on micro-or-nano-engineered surfaces have shown further heat transfer enhancement in dropwise condensation of water; however, the applications of these micro- or nanoscale structured surface designs have been restricted by the high manufacturing expenses and short range of subcooling limit. Recent studies have shown that the combination of millimeter sized geometric features and plain hydrophobic coatings can effectively manipulate droplet distribution of water condensate, which provides opportunities to locally facilitate dropwise condensation at relatively low manufacturing expenses as compared to those delicate micro- and nano-structured hydrophobic surfaces. Low surface tension fluids such as hydrocarbons pose a unique challenge to achieving dropwise condensation, because common hydrophobic coatings are not capable of repelling low surface tension fluids. Recent development in lubricant infused surfaces (LIS) offers promising solutions to achieving dropwise condensation of low surface tension fluids by replacing the solid-condensate interface in conventional hydrophobic coatings with a smooth lubricant-condensate interface. However, only a few experimental studies have applied LIS to promoting dropwise condensation of low surface tension fluids (y as low as 15 mN/m). In this work, we investigated dropwise condensation of both water (y ~ 72 mN/m) and a low surface tension fluid, namely butane (y - 13 mN/m) on structured surfaces. For water condensation, we studied the effects of millimeter sized geometric structures on dropwise condensation heat transfer under two different environments: pure vapor and an air-vapor mixture. Our experimental results show that, although convex structures enable faster droplet growth in an air-vapor mixture, the same structures impose the opposite effect during pure vapor condensation, hindering droplet growth. We developed a numerical model for each case to predict the heat flux distribution along the structured surface, and the model shows good agreement with experimental results. This work demonstrates that the effects of geometric features on dropwise condensation are not invariable but rather dependent on the scenario of resistances to heat and mass transfer in the system. For butane condensation, based on a design guideline we recently developed for lubricant infused surfaces, we successfully designed an energy-favorable combination of lubricant and structured solid substrate, which was further demonstrated to promote dropwise condensation of butane. The fundamental understanding of dropwise condensation of water and low surface tension fluids on structured surfaces developed in this study provides useful guidelines for condensation applications including power generation, desalination, dew harvesting, and thermal management.
Download or read book Numerical Study of Transient Heat and Mass Transfer on a Moving Droplet with Condensation written by Zheng Jiang Tang and published by . This book was released on 1991 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory of Laminar Film Condensation written by Tetsu Fujii and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 225 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the petroleum crisis in the 1970s, a lot of effort to save energy was made in industry, and remarkable achievements have been made. In the research and development concerning thermal energy, however, it was clar ified that one of the most important problems was manufacturing con densing systems with smaller size and higher performance. To solve this problem we need a method which synthesizes selections_ of the type of con denser, cooling tube and its arrangement, assessment of fouling on the cooling surfaces, consideration of transient characteristics of a condenser, etc. The majority of effort, however, has been to devise a surface element which enhances the heat transfer coefficient in condensation of a single or multicomponent vapor. Condensation phenomena are complexly affected by a lot of physical property values, and accordingly the results of theo retical research are expressed with several dimensionless parameters. On the other hand, the experimental research is limited to those with some specified cooling surfaces and some specified working fluids. Hence, the basic research of condensation is necessary for criticizing the enhancement effect as well as for an academic interest.
Download or read book A Study of Dropwise Condensation written by Ronald Luther Reisbig and published by . This book was released on 1966 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study on Heat Transfer in Dropwise Condensation written by Sanjay Adhikari and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Dropwise condensation (DWC) is a high intensity heat transfer phenomenon, with heat fluxes up to an order of magnitude higher than in filmwise condensation. Many industrial applications like desalination, thermal management, power generation and fog water harvesting may benefit from employing DWC. Considerable work has been done in this field and yet there are some challenges which remain open for research and further investigation. High resolution numerical studies that capture the complex hydrodynamics of larger droplets as they coalesce and move on the surface, effectively refreshing it for renucleation, have still not been realized as the drop size distribution spans six orders of magnitude. A new Volume of Fluid (VOF) based multi-scale approach, which resolves the grid scale larger droplets O(50 [mu]m) and models the heat transfer for the subgrid scale smaller droplets, is proposed in this dissertation. To supplement this approach, heat transfer models for individual droplets (Chapter 1) and droplet interaction (Chapter 2) are presented. Modeling work described in chapter 2 also solves many challenges associated with resolving grid scale droplets in VOF simulations. The proposed multi-scale approach also requires a transient heat transfer closure model for the subgrid scale droplets. Experimental studies have so far focused only on the steady state behavior of DWC. The startup period is still not well understood. Transient phenomena in DWC startup may significantly affect the performance of proposed applications like vapor chambers subjected to pulsed heat fluxes, or refrigeration cycles operating intermittently. This dissertation provides first characterization of fast transients during startup (chapter 4). A unique experimental facility and instrumentation are developed for measurements. Inverse numerical methods are employed to extract data (q" and HTC) from these measurements. Three distinct phases during DWC startup have been identified, which further highlight the importance of characterizing this period. The experimental data can be coupled with the numerical work described in this dissertation to formulate a robust, widely applicable simulation framework.
Download or read book Dropwise Condensation on Inclined Textured Surfaces written by Sameer Khandekar and published by Springer Science & Business Media. This book was released on 2013-09-06 with total page 155 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dropwise Condensation on Textured Surfaces presents a holistic framework for understanding dropwise condensation through mathematical modeling and meaningful experiments. The book presents a review of the subject required to build up models as well as to design experiments. Emphasis is placed on the effect of physical and chemical texturing and their effect on the bulk transport phenomena. Application of the model to metal vapor condensation is of special interest. The unique behavior of liquid metals, with their low Prandtl number and high surface tension, is also discussed. The model predicts instantaneous drop size distribution for a given level of substrate subcooling and derives local as well as spatio-temporally averaged heat transfer rates and wall shear stress.
Download or read book The Physics of Dew Breath Figures and Dropwise Condensation written by Daniel Beysens and published by Springer Nature. This book was released on 2022-01-31 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, the author focuses on the physics behind dew, breaths figures, and dropwise condensation phenomena to introduce scientists, engineers and students to the many original processes involved in condensation. Consisting of 15 Chapters, 18 Appendices and over 500 references, the reader learns the needed theoretical backgrounds and formulae to understand the complexity of dropwise condensation. Heat and mass transfer, nucleation and growth on various substrates are considered (solid, liquid, plastic, undergoing phase change or micro-patterned substrates). The particular role of thermal or geometrical discontinuities where growth can be enhanced or reduced, dynamical aspects of self-diffusion, problems related to drop collection by gravity and the optics of dropwise condensation are all discussed. Although the content mainly deals with condensation from humid air, it can readily be generalized to condensation of any substance. The specificities of pure vapor condensation (e.g. steam) are also examined. Numerous images are provided within the text to illustrate the physics. This book is meant for those studying or researching dew and dropwise condensation, but also for individuals wishing to develop their knowledge on the subject.
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Study of Drop wise Condensation as Related to Normal Alkyl Amines written by Wayne Douglas Erickson and published by . This book was released on 1955 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Overview of Heat Transfer Phenomena written by Salim Newaz Kazi and published by BoD – Books on Demand. This book was released on 2012-10-31 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the wake of energy crisis due to rapid growth of industries, urbanization, transportation, and human habit, the efficient transfer of heat could play a vital role in energy saving. Industries, household requirements, offices, transportation are all dependent on heat exchanging equipment. Considering these, the present book has incorporated different sections related to general aspects of heat transfer phenomena, convective heat transfer mode, boiling and condensation, heat transfer to two phase flow and heat transfer augmentation by different means.
Download or read book Handbook of Thermal Science and Engineering written by and published by Springer. This book was released on 2018-07-31 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1981 with total page 1740 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Handbook of Phase Change written by S.G. Kandlikar and published by Routledge. This book was released on 2019-01-22 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive coverage of the basic phenomena. It contains twenty-five chapters which cover different aspects of boiling and condensation. First the specific topic or phenomenon is described, followed by a brief survey of previous work, a phenomenological model based on current understanding, and finally a set of recommended design equa
Download or read book Transient Droplet Growth During Dropwise Condensation written by Charles Joslin Hurst and published by . This book was released on 1966 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study investigated the possibility of determining high heat-transfer rates during dropwise condensation by analyzing single condensate droplets growing on a convectively-cooled surface. A mathematical model included both the droplet and a portion of the condensing surface. Experiment utilized condensate droplets, growing on a thin copper surface, to verify the analysis. Experimental results agreed closely with predicted results--indicating high heat-transfer rates at droplet perimeters. Both experiment and analysis showed that no single vapor-to-condensing-surface temperature difference may be expected during dropwise condensation. Limitations on the calculation procedure pertaining to the region around the droplet perimeter restricted the accuracy of heat-transfer rate predictions; a separate study of droplet perimeter is suggested. (Author).
