Download or read book Investigation of Heat Transfer Efficiency of Dropwise Condensation with Surface Modification by Coating and Structuring Mathematical Model and Experimental Validation written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Heat Transfer Efficiency of Dropwise Condensation with Surface Modification by Coating and Structuring written by and published by . This book was released on 2015 with total page 151 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 21st Century Surface Science written by Phuong Pham and published by BoD – Books on Demand. This book was released on 2020-11-26 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface sciences elucidate the physical and chemical aspects of the surfaces and interfaces of materials. Of great interest in this field are nanomaterials, which have recently experienced breakthroughs in synthesis and application. As such, this book presents some recent representative achievements in the field of surface science, including synthesis techniques, surface modifications, nanoparticle-based smart coatings, wettability of different surfaces, physics/chemistry characterizations, and growth kinetics of thin films. In addition, the book illustrates some of the important applications related to silicon, CVD graphene, graphene oxide, transition metal dichalcogenides, carbon nanotubes, carbon nanoparticles, transparent conducting oxide, and metal oxides.
Download or read book Investigation of Heat Transfer Effiency of Dropwise Condensation with Surface Modification by Coating and Structuring Mathematical Model and Experimental Validation written by Chien-Hung Lu and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Factories of the Future written by Tullio Tolio and published by Springer. This book was released on 2019-02-14 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is open access under a CC BY 4.0 license.This book presents results relevant in the manufacturing research field, that are mainly aimed at closing the gap between the academic investigation and the industrial application, in collaboration with manufacturing companies. Several hardware and software prototypes represent the key outcome of the scientific contributions that can be grouped into five main areas, representing different perspectives of the factory domain:1) Evolutionary and reconfigurable factories to cope with dynamic production contexts characterized by evolving demand and technologies, products and processes.2) Factories for sustainable production, asking for energy efficiency, low environmental impact products and processes, new de-production logics, sustainable logistics.3) Factories for the People who need new kinds of interactions between production processes, machines, and human beings to offer a more comfortable and stimulating working environment.4) Factories for customized products that will be more and more tailored to the final user’s needs and sold at cost-effective prices.5) High performance factories to yield the due production while minimizing the inefficiencies caused by failures, management problems, maintenance.This books is primarily targeted to academic researchers and industrial practitioners in the manufacturing domain.
Download or read book Scalable Micro nanostructured Surfaces for Thin film Condensation Heat Transfer Enhancement in Steam Power Plants written by Yajing Zhao (Mechanical engineer) and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Steam power plants, which contribute to over 50% of energy production globally, rely on condensers to control system-level energy efficiency. Due to the high surface energy of common heat exchanger materials, the vapor condenses by forming a continuous liquid film with low thermal conductivity (filmwise condensation), hindering heat transfer from the vapor side to the condenser surface. Hydrophobic surfaces achieved by either chemical methods (e.g., coating treatment) or physical methods (e.g. structures design) have shown great promise in enhancing condensation heat transfer by promoting dropwise condensation. However, the short lifetime and high fabrication cost of most of these hydrophobic surfaces remain a challenge for long-term and large-scale industrial applications. A promising solution to enhancing condensation heat transfer in a robust and scalable manner is to control the thickness and thermal conductivity of the condensate film, which we term thin-film condensation. This can be achieved by sandwiching a thin layer of porous metal wick between a hydrophobic membrane and the condenser surface to confine the condensed liquid, forming a thin liquid-metal composite film that significantly improves the effective thermal conductivity of the condensate-filled porous media. In this work, we designed, fabricated, tested, and demonstrated thin-film condensation heat transfer using commercially available materials and scalable approaches. First, we proved the concept using biphilic, microchannel-assisted hierarchical copper surfaces made of commercially available copper foams and copper meshes. Condensation heat transfer on the hierarchical copper surfaces was characterized to be up to 2x as compared to the conventional filmwise condensation, even with flooding on the surface due to the defects on the mesh and the coating. Then, we investigated electrospinning as a potential approach to customize hydrophobic membranes for the thin-film condenser surfaces. The key benefit of the hydrophobic membrane in the surface design is to generate capillary pressure through micro/nanoscale pores, which acts as the driving force for the condensate flow in the metal wick. We conducted a parametric study on the effects of several key fabrication parameters on the pore size of the electrospun membrane, with the help of the fractional factorial design. Solution feeding rate was found to be the most impactful parameter on the membrane pore size and should be considered the most during membrane optimization. A heat and mass transfer model was developed to predict the heat transfer performance of the thin-film condenser surfaces made of electrospun membranes and porous copper wicks. Upon careful design of the surface structures, an over 5x heat transfer enhancement is expected on these thin-film condensers, which is comparable to the state-of-the-art dropwise condensation. Finally, a techno-economic analysis was conducted on the thin-film condensers. The result shows that the additional material for the condenser tube modification costs less than 10% of the condenser cost. However, with the expected 5x steam-side condensation heat transfer performance, thin-film condensers will be able to increase power plants' output by 2-6%, which is equivalent to over $10B of the value proposition for steam power plants across the globe.
Download or read book Heat transfer Studies of Dropwise Condensation and Thin film Evaporation written by C. Saturnino and published by . This book was released on 1963 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Exploring the Limits of Dropwise Condensation on Nano structured Surfaces written by Hector Mendoza and published by . This book was released on 2013 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Within the types of condensation that can form on a surface, dropwise condensation has been previously shown to produce condensation heat transfer coefficients up to an order of magnitude greater than film condensation. Among dropwise condensation investigations, it has also been shown that smaller droplets result in higher heat transfer coefficients. An area that is currently under investigation within condensation advancements is creating superhydrophobic surfaces that can sustain smaller droplets during condensation. However, as droplet diameters are reduced to sizes comparable to the flow's mean free path, various mechanisms are expected to affect transport as the flow transitions from a continuum to free molecular flow: non-continuum transport effects, curvature effects on surface tension and on saturation conditions, and interactions with nearby droplets. In this dissertation, we investigate the limits of heat transfer performance on surfaces that strive to sustain dropwise condensation for smaller droplets. We explore and compare the limitations of dropwise condensation as mean droplet sizes are reduced to micro and nanoscales using three different models: one that uses an approximation for micro and nanoscale transport on an array of droplets, one that uses the DSMC method to simulate transport on a single droplet, and a third model that uses the DSMC method to simulate transport on an array of droplets. We found the three different models to show similar trends; dropwise condensation heat transfer coefficients increased as droplet sizes were reduced, but only up to a certain point where non-continuum transport and curvature effects became significant. For pure steam condensing on a cold wall at standard atmospheric condition with 3 degrees Celsius of subcooling, drop- wise condensation heat transfer coefficients were found to peak when droplets approached diameters near 200 nm. The effects of varying contact angle, thermal accommodation, pres- sure, amount of subcooling, spacing between droplets, and introduction of noncondensible particles into the system are also explored and discussed in detail.
Download or read book Investigation of Hydrophobic Coatings in Air Cooled Condensers for Heat Transfer Applications written by Kuok Kong Cheng and published by . This book was released on 2012 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, industries are replacing traditional fluoride based refrigerants for different alternative such as hydrocarbons and water based refrigerants in HVAC applications due to environmental concerns. Air cooled condensers are widely used in HVAC applications and there are ongoing researches to improve the thermodynamic efficiencies for these devices and environmental friendly at the same time. For internal condensations, there are several ways to enhance heat transfer performances, such as coil inserts and surface micro structures. Many of the researches focus on condenser surface modifications mainly on internal machined microstructure patterns. It was found that such techniques improve heat transfer performances up to 400 % compared with smooth surfaces due to enhance mixing and drainage. However, such techniques do not work with all geometries such as micro-channels and other complicated shapes. In the field of external condensation studies, dropwise condensations (DWC) are found to enhance heat transfer coefficients about 300 % to 400 % compared to filmwise condensation (FWC) in most researches. In order to promote DWC, hydrophobic coatings are applied to the condensing surface in most cases. Coatings techniques are solution based and could be easily applied to different geometries. Techniques for promoting DWC for external condensations can be applied to internal condensation as well. The objective of this project is to investigate heat transfer enhancements of DWC promoters has on internal condensation via model based on external DWC and FWC heat transfer models; experiments with hydrophobic coatings inside (coatings provided by NEI Corporation) as well as finned non-coated finned copper and aluminum tubes were conducted with water, n -hexane and n -heptane were carried out to investigate the effects of such promoters; experimental results were compared with establish correlations and models developed in this project. Models developed in this project suggest that DWC promoters could potentially enhance heat flux and heat transfer coefficients compared with FWC. It was found that hydrophobic coatings enhance heat flux and internal heat transfer coefficients by 20 % and 50 % for water and such coatings have negligible effects on n -hexane and n -heptane. Also, most established correlations over predict heat transfer coefficients at low mass flow in water, n -hexane and n -heptane
Download or read book Parametric Studies on Dropwise Condensation Heat Transfer written by Kuok Kong Cheng and published by . This book was released on 2014 with total page 236 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wettability of a solid surface with liquids could be tuned based on surface morphologies. This is significant in condensation heat transfer. Condensation is a critical heat transfer mechanism in industrial processes; Dropwise (DWC) and Filmwise (FWC) condensation processes are important and are focus of this study. There are few studies on surface morphology effect on wetting behavior of a solid in relation to condensation heat transfer. We conducted these studies to understand the phenomenon. Condensation heat transfer is affected by condensate droplets properties on the surface. Condensate drop sizes and mobility relationships are important to condensation heat transfer. Droplet sizes and mobility affect population density and condensation heat transfer coefficients directly. The goal of this study is to acquire the fundamental understanding of condensation heat transfer with relation to condensate droplet behavior. In order to achieve this goal, a liquid droplet wetting dynamic model was initially developed for predicting single drop behavior on different surfaces. Heat fluxes were then estimated by combining liquid droplet behavior models and heat transfer model. Condensation experiments were conducted to verify effectiveness of the model. Experimental results coupled with condensation models revealed relationships between wetting behaviors and condensation heat transfer. Contact angle hysteresis (CAH) remains low at both high and low droplet contact angle, i.e. whether the surface is hydrophilic or hydrophobic. CAH increases with degree of wetting, but coating thermal conductance also increases. Details of drop (DWC) and film-wise (FWC) condensation are presented.
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 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 CAPILLARY ASSISTED ENHANCED CONDENSATION HEAT TRANSFER FOR LOW SURFACE TENSION LIQUIDS written by and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Extensive research has been carried out over the course of the last few decades to induce dropwise condensation as it offers 5 - 7 times better heat transfer performance compared to filmwise condensation process. A number of methods such as low surface energy hydrophobic coatings, surface modification of hydrophobic surfaces to fabricate micro, nano and hierarchical structures, and the recent incorporation of jumping droplet phenomenon have provided effective means to further enhance the condensation heat transfer. However, existing methods to enhance condensation heat transfer rate fail in the case of low surface tension, highly wetting liquids such as hydrocarbons, cryogens, and fluorinated dielectrics and refrigerants used in various industrial applications. Due to their extremely wetting behavior, such fluids almost always condense in a filmwise mode and the removal of the condensate other than by gravity has been a challenge. Here, we fabricate a novel capillary surface to decouple the removal of the condensate vapor from the condensing surface. The new surface consists of alternating capillary bridge and plain sections. The liquid condensing in the plain channels and the outer surfaces of the capillary bridge is wicked into the wick bridge, effectively decoupling the condensation surface and the condensate removal paths. We have determined that the condensation performance of the fabricated surfaces is enhanced by a factor of 3 compared to a plain surface, and further enhanced by a factor of 4.5, compared to a plain surface, by bonding an additional cover mesh layer and decreasing the channels widths of the condensation surface. This proves that the concept of employing a capillary bridge greatly enhances the rate of condensation for low surface tension liquids such as dielectric fluids. Hence, the knowledge gained from this thesis will serve as basic guideline for designing new simple, cost effective, and scalable surface technologies with enhanced condensation heat transfer for widely used low surface tension liquids.
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 Bioinspired Engineering of Thermal Materials written by Tao Deng and published by John Wiley & Sons. This book was released on 2018-06-11 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive overview and summary of recent achievements and the latest trends in bioinspired thermal materials. Following an introduction to different thermal materials and their effective heat transfer to other materials, the text discusses heat detection materials that are inspired by biological systems, such as fire beetles and butterflies. There then follow descriptions of materials with thermal management functionality, including those for evaporation and condensation, heat transfer and thermal insulation materials, as modeled on snake skins, polar bears and fire-resistant trees. A discussion of thermoresponsive materials with thermally switchable surfaces and controllable nanochannels as well as those with high thermal conductivity and piezoelectric sensors is rounded off by a look toward future trends in the bioinspired engineering of thermal materials. Straightforward and well structured, this is an essential reference for newcomers as well as experienced researchers in this exciting field.
Download or read book Heat and Mass Transfer written by Hans Dieter Baehr and published by Springer Science & Business Media. This book was released on 2006-08-02 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a solid foundation in the principles of heat and mass transfer and shows how to solve problems by applying modern methods. The basic theory is developed systematically, exploring in detail the solution methods to all important problems. The revised second edition incorporates state-of-the-art findings on heat and mass transfer correlations. The book will be useful not only to upper- and graduate-level students, but also to practicing scientists and engineers. Many worked-out examples and numerous exercises with their solutions will facilitate learning and understanding, and an appendix includes data on key properties of important substances.
