Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 20 for “"Filmwise condensation"”.
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Design of an apparatus to experimentally verify filmwise condensation theory on small diameter horizontal tubes
… to experimentally verify the accuracy of filmwise condensation heat transfer theories for small diameter horizontal tubes was developed. The apparatus was designed so that the condensation pattern was visible at all locations, all of the parameters necessary to calculate the average heat …
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Enhanced condensation heat transfer for water and low surface tension fluids
Vapor condensation is routinely used as an effective means of transferring heat or separating fluids for applications ranging from personal electronic device thermal management to natural gas processing and electric power generation. Filmwise condensation, where the condensed fluid forms a liquid …
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Dropwise condensation on hydrophilic surfaces
Droplet nucleation and condensation are ubiquitous phenomena in nature and industry. Over the past century, research has shown dropwise condensation heat transfer on non-wetting surfaces to be an order of magnitude higher than filmwise condensation heat transfer on wetting substrates. However, the …
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Hydrophobicity of rare-earth oxide ceramics and their application in promoting sustained drop-wise condensation
… hydrophobic materials promote dropwise condensation, which results in heat transfer coefficients that can be an order of magnitude higher than those seen in conventional filmwise condensation. Existing durable materials such as metals and ceramics are generally hydrophilic and require …
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Fabrication, characterization, and wettability analysis of a microstructured hybrid hydrophobic/hydrophilic surface
… The surfaces are designed with stable dropwise condensation in mind, which can increase heat fluxes by an order of magnitude over those of filmwise condensation. Based on the literature and technical constraints on fabrication, four Hybrid Surfaces are designed, fabricated, characterized and …
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The determination of a water film coefficient and a condensing steam film coefficient for a single tube heat exchanger
… an average condensing steam film coefficient for filmwise condensation was 2000 Btu/hr-ft²-F. It was discovered that this coefficient is much higher if the condensing surface is highly polished.
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Enhanced condensation with active methods
Condensation of low surface tension fluids is important in liquefied natural gas processing and refrigeration systems. Current state of the art low surface energy low hysteresis coatings are not able to achieve dropwise condensation below 10 mN/m. Surface acoustic waves are proposed as an active …
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Enhanced phase change heat transfer through advanced fabrication techniques
… transfer during vapor to liquid phase change or condensation is a critical industrial operation, determining the efficiency and costs of several processes. It is well established that dropwise condensation of water vapor has 10 – 20 times higher heat transfer compared to filmwise condensation. …
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Capillary-Driven Condensation for Heat Transfer Enhancement in Steam Power Plants
Condensation is a phenomenon that is ubiquitous in nature and used to effectively transfer heat in many important industrial applications including thermal management of electronics, steam power generation, and natural gas processing. Industry relies mainly on filmwise condensation, where the …
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Design and construction of rigs for studying surface condensation and creating anodized metal oxide surfaces
… and construction of a rig for studying surface condensation and a rig for creating anodized metal oxides (AMOs). The condensation rig characterizes condensation for different surfaces; this is done with the use of known heat transfer principles to calculate characteristic heat fluxes and heat …
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Heat transfer rates for filmwise, dropwise, and superhydrophobic condensation on silicon substrates
Condensation, a two-phase heat transfer processes, is commonly utilized in industrial systems. Condensation heat transfer can be optimized by using surfaces in which dropwise condensation (DWC) occurs, and even further optimized using superhydrophobic surfaces. For superhydrophobic condensation, a …
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Scalable Micro/Nanostructured Surfaces for Thin-Film Condensation Heat Transfer Enhancement in Steam Power Plants
… 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 …
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Dropwise condensation of water and low surface tension fluids on structured surfaces
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 …
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Heat transfer and visualization in large flattened-tube condensers with variable inclination
An experimental study of convective condensation of steam in a large, inclined, finned tube is presented. This study extends previous work in the field on inclined, convective condensation in small, round tubes to large, non-circular tubes with low inlet mass flux of vapor. The steel condenser tube …
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Liquid-vapor phase change phenomena for heat exchangers and electronics cooling
… change of water is widely observed. Water vapor condensation is vital to many natural and industrial processes such as building environmental control, power generation, and water desalination. Jumping-droplet condensation of water has recently been shown to have a 10X heat transfer enhancement …
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From adsorption to condensation: The Zeta adsorption isotherm approach
… and heptane vapours adsorbing on Si. Dropwise condensation is observed experimentally for toluene vapour while filmwise condensation is observed for the other two vapours. From the distribution of the clusters in the adsorbate, the conditions for the initiation of the liquid phase are predicted …
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Influence of Surface Wettability on Drop Dynamics and Condensation
… in the interrelated areas of coalescence, condensation heat transfer, and inertial-capillary (rapid) spreading. In the first part of this dissertation, experiments and numerical simulations are employed to examine how changing the surface wettability, via modification of _ & __, influences …
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Wetting and phase-change phenomena on micro/nanostructures for enhanced heat transfer
… superhydrophobic surfaces with dropwise condensation promises higher heat transfer coefficients than typical filmwise condensation. My thesis work aims at improving fundamental understanding as well as demonstrating practical enhancements in these two areas. A key challenge to realizing …
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Effects of air-side surface wettability on the performance of dehumidifying heat exchangers
… treatment (up to 43.5% lower). Due to more filmwise manner of retention and a reduced possibility of bridging, a super-hydrophilic surface shows improved drainage performance for these tested heat exchangers, over the entire range of fin spacing (more than 30% mass reduction for all cases of …
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Impact of heat exchanger surface wettability on condensation, frosting, and defrosting performance under practical testing conditions
Condensation and frost accumulation on aluminum heat exchangers present major challenges for heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems. Both phenomena increase thermal resistance and airflow restriction, which diminish heat transfer, lower system capacity, and drive …