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.
Results
Showing 1 to 20 of 28 for “"Filmwise"”.
-
Heat transfer rates for filmwise, dropwise, and superhydrophobic condensation on silicon substrates
… and SHC were found to be greater than that of filmwise condensation (FWC) by a factor of 2, but indistinguishable from each other. The effect of NCG leads to a 5x reduction in heat transfer rates for both DWC and SHC. DWC heat transfer rates are as much as 50 kW/m 2 less than FWC at the same …
-
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 …
-
Visualization and measurement of filmwise and dropwise air gap membrane distillation at varied module inclination angle and gap spacer Orientation
Improving efficiency is the main target for improving rapidly developing water desalination technologies such as air gap membrane distillation (AGMD). While the system is dominated by heat and mass transfer resistances in the air gap specifically, very little is known about the impact of variations …
-
Enhanced condensation heat transfer for water and low surface tension fluids
… gas processing and electric power generation. Filmwise condensation, where the condensed fluid forms a liquid film, is prevalent in typical industrial-scale systems. Conversely, dropwise condensation, where the condensate forms discrete liquid droplets, results in an improvement in heat …
-
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 …
-
Dropwise condensation of water and low surface tension fluids on structured surfaces
… 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 …
-
Dropwise condensation on hydrophilic surfaces
… surfaces to be an order of magnitude higher than filmwise condensation heat transfer on wetting substrates. However, the necessity for non-wetting to achieve dropwise condensation is unclear. Here we report stable dropwise condensation on a smooth, solid, hydrophilic surface (𝜃a = 38°) having low …
-
Hydrophobicity of rare-earth oxide ceramics and their application in promoting sustained drop-wise condensation
… magnitude higher than those seen in conventional filmwise condensation. Existing durable materials such as metals and ceramics are generally hydrophilic and require polymeric modifiers to render them hydrophobic, but these modifiers deteriorate in harsh environments. Therefore, robust hydrophobic …
-
Fabrication, characterization, and wettability analysis of a microstructured hybrid hydrophobic/hydrophilic surface
… 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 tested for wettability. A model based on energy minimization is referenced and fits well to the …
-
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.
-
Enhanced condensation with active methods
… showed more than 2X improvement over standard filmwise condensation. Further, the effect of refrigerant side heat transfer enhancement in a condenser operating in a vapor compression refrigeration cycle is studied as a potential application.
-
Enhanced phase change heat transfer through advanced fabrication techniques
… 10 – 20 times higher heat transfer compared to filmwise condensation. Dropwise condensation is promoted by hydrophobic surfaces, characterized with intrinsic advancing contact angles (CA) greater than 90° as against filmwise condensation on hydrophilic (CA < 90°) surfaces. With the advancement …
-
Capillary-Driven Condensation for Heat Transfer Enhancement in Steam Power Plants
… gas processing. Industry relies mainly on filmwise condensation, where the condensate forms an insulating, thick liquid film on the condensation surface, posing a large thermal resistance. For almost a century, much work has explored developing surfaces that can promote the nucleation, …
-
Design and construction of rigs for studying surface condensation and creating anodized metal oxide surfaces
… effectiveness of dropwise condensation over filmwise condensation. The AMO rig fabricates anodized metal oxide surface samples by subjecting wafers coated with thin metal layers to voltage in the presence of acidic electrolytes. Initial fabricated anodized aluminum oxide (AAO) samples have …
-
Heat transfer measurements in film condensation of steam on small diameter horizontal tubes
… eliminated by repeated cleaning of the tubes. Filmwise, dropwise, mixed, and streaky condensation patterns of steam on the horizontal tubes were observed and photographed. The flow pattern in film condensation showed definite three-dimensional behaviour and was strongly affected by surface …
-
Condensation on superhydrophobic copper oxide nanostructures
… facilitates improvements over traditional filmwise and dropwise condensation. This work investigates copper oxide nanostructures as a potential substrate for superhydrophobic condensation. We first explored and refined a procedure for creating and functionalizing oxide nanostructures on …
-
Influence of Surface Wettability on Drop Dynamics and Condensation
… transfer coefficient by switching between the filmwise and dropwise modes of condensation, with ultimate relevance to space-based thermal management applications. Theory is also applied to understand how surface wettability affects fundamental drop processes during dropwise condensation, and to …
-
Design and fabrication of an internal condensation loop for effectiveness and robustness testing of nanostructured superhydrophobic steam condenser
… in these systems occurs predominantly via the filmwise mechanism, in which a thin film of water forms upon the condensing surface, adversely affecting its heat transfer abilities. However, forming a nanostructure and adding certain hydrophobic coatings on the heat exchanging surface of the …
-
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 …
-
Parametric studies on dropwise condensation heat transfer
… 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 …
Page 1 of 2