2 edition of Dropwise condensation on vibrating condensing surfaces found in the catalog.
Dropwise condensation on vibrating condensing surfaces
Ahmed Assem Abdelrahman
|Contributions||Toronto, Ont. University.|
|The Physical Object|
|Pagination||260 leaves in various pagings :|
|Number of Pages||260|
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Compared to filmwise condensation on conventional condenser surfaces, heat transfer can be significantly enhanced by tuning the wettability of the surface to promote dropwise condensation. 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. Dropwise condensation is vapor-to-liquid phase-change in the form of discrete drops on or underneath horizontal and inclined substrates.
The process is hierarchical in the sense that it occurs over a wide range of length and timescales. A mathematical model of dropwise condensation underneath textured surfaces.
Previous studies on dropwise condensation are primarily devoted to steam, with a few studies of fluids with high or moderate surface tens28,29,30,31 or Marangoni dropwise condensation of binary mixtu33,34,35,36,37, To our knowledge, dropwise condensation of fluids with a surface tension, γlv, Cited by: Dropwise condensation on vibrating condensing surfaces book Marangoni dropwise condensation occurs in the condensation of a binary vapor mixture of a positive system, in which the surface tension of the mixture has a negative gradient with the mass fraction of the more volatile component, such as Author: Yoshio Utaka, Zhihao Chen.
Apparatus employed to achieve high gravitational accelerations parallel to the surface of dropwise condensation, has a centrifuge to rotate a test piece, a test piece assembly to produce dropwise condensation, a boiler with electric Dropwise condensation on vibrating condensing surfaces book to generate steam, a cooling system including a refrigeration unit and controls to maintain the coolant at constant temperature at the desired level, an auxiliary condenser to condense Cited by: like chrome plating on condenser surface is required for dropwise polished surfaces also practice dropwise condensation.A overall heat transfer coefficient model is to be developed for dropwise condensation based on following Dropwise condensation on vibrating condensing surfaces book parameters.
(i) Plating thickness of condenser surface (ii) Surface finishing of plated material. Dropwise condensation occurs when a vapor condenses on a surface not wetted by the condensate. For nonmetal vapors, dropwise condensation gives much higher heat transfer coefficients than those found with film condensation.
To attain efficient shedding of liquid droplets in condensation on a superhydrophobic surface, a Bond number (a dimensionless number for appraising dropwise condensation) and a solid–liquid fraction smaller than andrespectively, are by: 2 CONDANTION Dropwise condensation equilibrium film of liquid is barrier to transfer.
By specially treating the condensing surface the contact angle can be changed & the surface become ‘non – wettable’.As the stream condenses,a large number of generally spherical beads cover Dropwise condensation on vibrating condensing surfaces book Size: KB. The dependence on gravity for liquid removal limits the utilization of dropwise condensation in low gravity aerospace applications and horizontal surfaces.
Presented in this study is a novel passive mechanism to remove droplets from a condensing surface using a surface energy gradient (wettability gradient) on the condensing by: 5. lv = 17 mN/m) is low enough to promote dropwise condensation of most condensed fluids while avoiding cloaking,17,64 and also because of its low vapor pressure, broad chemical inertness, and Dropwise condensation on vibrating condensing surfaces book with most of the condensed fluids.
File Size: 7MB. Some promoters of dropwise condensation are the fatty acids, mercaptans, light hydrocarbon oils, and waxes. However, promoters of this type wash off the condensing surfaces rather quickly and usually last only for periods of sev- eral seconds or, in some rare cases, up to a maximum of several hundred hours (refs.
Condensation of vapor is a crucial part of a wide range of industrial processes from power Dropwise condensation on vibrating condensing surfaces book and distillation to liquefaction and refrigeration 1,2,3,4,5, the past eight decades, significant attention has been devoted to the study of underlying mechanisms, methods, and materials for enhancing the condensation heat transfer rate of steam by promoting dropwise by: To promote the water vapor condensation efficiency in the presence of a non-condensable gas, both high nucleation rate and efficient droplet departure are desired on the condensing surface.
Superhydrophobic surfaces with large water contact angles ensure the dropwise condensation mode and efficient droplet departure ability. The paper presents a new theory of heat-transfer by dropwise condensation in the absence of non-condensing gases. The authors consider the heat-transfer arising from condensation on a single drop, and by means of an assumed distribution of drop sizes, deduce the mean heat-transfer rate for the whole by: Dropwise condensation on textured surfaces and multi-scale modeling.
Dropwise condensation is a heterogeneous phase-change process in which vapor condenses in the form of discrete liquid drops on or underneath a cold substrate. The heat transfer coefficient of dropwise condensation can be up to an order higher than film condensation and mixed.
The dropwise condensation underneath a horizontal super-hydrophobic surface having unidirectional wettability gradient is modeled with implication to enhance the rate of condensation. The mathematical model includes nucleation, growth by vapor condensation and coalescence, and. Presented here is a general use of self-assembled monolayer coatings to promote dropwise condensation on low-cost steel-based surfaces.
Together with inhibitors in the working fluid, the surface of condenser is protected by hydrophobic coating, and the condensation heat transfer is promoted on carbon steel : Fangyu Cao, Sean Hoenig, Chien-hua Chen.
The outer surfaces of copper tubes in the horizontal orientation were used as the condensation surface with the designed patterns. The condensation heat transfer rates were compared to that of the complete dropwise condensation (DWC) and. 15 results for "dropwise condensation".
Skip to main search results. In dropwise condensation the condensate liquid collects in the form of countless droplets of varying diameters on the condensing surface, instead of forming a continuous film, and does not wet the solid cooling surface.
The droplets develop at points of surface imperfections (pit, scratch), called nucleation sites. T1 - Dropwise condensation of steam on ion implanted condenser surfaces.
AU - Zhao, Q. AU - Burnside, B. PY - /9. Y1 - /9. N2 - Modern developments in surface treatment which reduce the energy of condensing surfaces and hence allow permanent, reliable dropwise condensation are by: In this review we cover recent developments in the area of surface- enhanced dropwise condensation against the background of earlier work.
The development of fabrication techniques to create surface structures at the micro- and nanoscale using both bottom- up and top- down approaches has led to increased study of complex interfacial phenomena. Dropwise condensation, where condensed droplets are removed from the surface before coalescing into a film, has been shown to increase the heat transfer efficiency and water collection ability of many surfaces.
Continuous dropwise condensation on a hierarchical bioinspired lotus leaf metallic surface without the need for a conformal hydrophobic coating is hence demonstrated, which offers a novel path for the design and manufacture of non-coated metallic super-repellent surfaces for condensation phase change applications, amongst by: 5.
In this study, the heat transfer characteristics under dropwise condensation are investigated by the calculation and the experiment when the vertical condensing surface is vibrated in gravitational direction. As a result, we found that the heat transfer coefficient was enhanced by the vibration.
Dropwise condensation (DWC) on hydrophobic surfaces is attracting attention for its great potential in many industrial applications, such as steam power plants, water desalination, and de-icing of Cited by: condense in to two ways-dropwise or filmwise on tube film -wise condensation, the heat from the vapour to the cooling medium is transferred through the film of the condensate formed on the surface,where as in dropwise condensation process, only a part of surface is covered with Size: KB.
condensation is the common mode of condensation found in applications, Schmidt et al. recognized dropwise condensation to have a higher heat transfer efficiency in . Imperative of dropwise condensation is a (super-) hydrophobic surface, indicated by a high contact angle and low contact angle.
Film wise and Drop wise condensation are nothing but two different results of condensation of vapor/steam when gets into contact of cooled surface. In film wise condensation, the cooled surface is smooth and friction-less which results in quick.
Cavallini A, Bella B, Longo GA, Rossetto L () Pure vapour condensation of refrigerant on a horizontal FPM integral finned tube. In: Taborek J, Rose, Tanasawa I (eds) Condensation and condenser design (Proceedings of the engineering foundation conference on condensation and condenser design).
ASME, New York, pp – Google. The condensation heat transfer coefficient is evaluated on copper, carbon steel, and stainless steel flat condenser surfaces using FFA and non-FFA, or neutralizing amine, coating solutions of PAS The initial results indicate a consistent improvement in thermal performance using these coating solutions to generate dropwise condensation.
This experimental study was conducted to acquire more reliable data concerning dropwise condensation in the very low subcooling region.
The heat transfer surface and the temperature measuring system was improved and the following results were obtained: A subcooling of about /sup 0/C was obtained as the average of the initiation of dropwise condensation by the.
dropwise condensation of low-surface-tension liquids remains a challenge.7 Context & Scale A majority of the work devoted to surface engineering for promoting dropwise condensation heat transfer has focused on steam.
Less attention has been dedicated to the condensation of low-surface-tension ﬂuids such as hydrocarbons and refrigerants. The condensate may form a continuous film on the surface or, when the surface is not wetted by the condensate, form discrete droplets (see Dropwise Condensation).
Condensation may occur on external surfaces, e.g., on the outside of the tubes in a shell-and-tube condenser or on internal surfaces, e.g., in-tube condensation. highlighted by the total absence of dropwise condensation as a fac'tor in design of condensers in industry.
Recommendations are made to initiate an experimental program to evaluate the effects of vibrating the condenser surface upon dropwise condensation and the coefficients of. Condensation occurs in most of the heat transfer processes, ranging from cooling of electronics to heat rejection in power plants.
Therefore, any improvement in condensation processes will be reflected in the minimization of global energy consumption, reduction in environmental burdens, and development of sustainable systems. The overall heat transfer coefficient of dropwise condensation Cited by: 5.
Condensation is the change of the physical state of matter from the gas phase into the liquid phase, and is the reverse of word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to liquid water when in contact with a liquid or solid surface or cloud condensation nuclei within the atmosphere.
previously developed model of complete dropwise condensation process of the authors (Sikarwar et al., ), to get the local/average heat transfer coefficient during quasi-steady state dropwise condensation process on large flat surfaces. Here, we also investigate the effect of nucleation site density, varied from /cm2 to /cm2.
After. This thesis pdf the process of dropwise condensation (DWC) of water vapor on a non-isothermal condenser surface. Pdf, the object was to quantify the effects of Vibration Induced Droplet Atomization (VIDA) on this process.
The working fluid was water vapor in the saturation temperature range from 24 to 48°C (75 to °F),File Size: 4MB.An experimental apparatus was designed and constructed for the purpose of determining dropwise condensation heat transfer coefficients on condensing surfaces.film and dropwise condensation Product number: HK The Ebook and Dropwise Condensation Module HK is used with the H Heat Exchanger Service Unit which supplies both electrical power and instrumentation for the module via a control console that is supplied with the HK module.