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 60 for “"Critical Heat Flux (CHF)"”.
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Critical heat flux enhancement via surface modification using colloidal dispersions of nanoparticles (Nanofluids)
… nanofluids include higher thermal conductivity, heat transfer coefficients (HTC) and boiling critical heat flux (CHF) than that of the respective base fluid. Nanofluids have been found to exhibit a very significant enhancement up to 200% of the boiling CHF at low nanoparticle concentrations. In …
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ENHANCEMENT OF SATURATION BOILING OF PF-5060 DIELECTRIC LIQUID ON MICROPOROUS SURFACES
… enhancing nucleate boiling and increasing the Critical Heat Flux (CHF) of PF-5060 dielectric liquid and the potential application of the results to immersion cooling of high power computer chips. MPC surfaces of different thicknesses (80—230 \uf06dm), fabricated using conventional …
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A Percolation Model for Boiling and Predicting CHF
… in numerous applications, characterized by the heat transfer coefficient (HTC) and critical heat flux (CHF). Exceeding CHF can result in catastrophic failure of a system, making it an important value to understand; however, there is no universal model for predicting it. A recently investigated …
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Wettability of candidate Accident Tolerant Fuel (ATF) cladding materials in LWR conditions
… as it affects the dynamics of the boiling heat transfer process, and consequently, the critical heat flux (CHF) and rewetting temperatures, which are important thermal limits for LWRs. Surface wettability determines nucleation site density, bubble departure diameter, and bubble departure …
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Multiphase CFD benchmark of experimental critical heat flux data at PWR operating conditions
Critical Heat Flux (CHF) in flow boiling represents the fundamental upper limit for thermal hydraulic performance of PWR fuel. Currently, the nuclear industry relies on expensive, prototypical experiments using electrically heated, full-height rod assemblies to determine the limit of the boiling …
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Synthesis of CRUD and its effects on pool and subcooled flow boiling
… such, CRUD deposition may have large effects on critical heat flux (CHF) and heat transfer coefficient (HTC). An investigation of such effects was conducted as part of the CASL project by creating well-defined and characterized synthetic CRUD with parameters representative of reactor CRUD on …
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Impact of self-rewetting aqueous solutions on boiling with advanced heat transfer applications
… and pentanol solution to study the boiling heat transfer enhancement at pressures of 1 ~ 4 bars. Although self-rewetting fluids have been used to enhance the performance of heat pipes, boiling heat transfer characteristics are yet to be fully understood especially at pressures above …
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Two-phase CFD analyses in fuel assembly sub-channels of Pressurized Water Reactors under swirl conditions
… FAs, including a realistic description of the critical heat flux (CHF)-phenomena and identification of two-phase indicators characterizing CHF-phenomena. The numerical simulations were conducted with a 3-D CFD code (STAR CD) for various types of swirl generating components in FA. New insights …
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Determination of pool boiling Critical Heat Flux enhancement in nanofluids
… Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina and Silica water-based nanofluids of concentration less than or equal to 0.1 percent by volume were measured. Silica nanofluids showed CHF enhancement up to 68% and there seems to be a …
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Measurement of near-surface void fraction and macrolayer thickness in boiling water and silica-based nanofluid
… or ceramics. They have been shown to increase heat transfer properties such as thermal conductivity, convective heat transfer, and critical heat flux(CHF). An optical probe used to detect phase was used to measure the void fraction during boiling, from which the macrolayer thickness can be …
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Direct Measurement of Boiling Water Heat Flux for Predicting and Controlling Near Critical Heat Flux
A novel method for measuring heat flux of boiling water is designed and built to study critical heat flux (CHF) and observe the response of a heat flux sensor when CHF occurs. A high temperature heat flux sensor is embedded in the wall of a pipe to get a direct measurement of the surface heat flux …
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Subcooled flow boiling heat transfer and critical heat flux in water-based nanofluids at low pressure
… have shown that nanofluids can improve the critical heat flux (CHF) by as much as 200%. In this study, subcooled flow boiling heat transfer and CHF experiments were performed with low concentrations of alumina, zinc oxide, and diamond nanoparticles in water (< 0.1 % by volume) at atmospheric …
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An inverted hydride-fueled pressurized water reactor concept
… by three main constraints: core pressure drop, critical heat flux (CHF) and fretting phenomena of the fuel rods against grid spacers. The present work investigates the possibility to reduce the limiting effect exerted by these constraints by radically changing the core geometry, rather than by …
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Effect of combined nanoparticle and polymeric dispersions on critical heat flux, nucleate boiling heat transfer coefficient, and coating adhesion
… and polymeric dispersion coating. The critical heat flux (CHF) values and nucleate boiling heat transfer coefficients (HTC) of nickel wires pre-coated using 1.0% alumina, 0.1% alumina, 500ppm polyallylamine hydrochloride (PAH), and 0.1% alumina combined with 500ppm PAH dispersions were …
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Hydrophobic coatings for film boiling based drag reduction on a torpedo model
… surfaces exhibit a dramatic reduction in critical heat flux (CHF), the amount of heat over a surface area required to initiate film boiling. Film boiling is characterized by the presence of a vapor layer which remains as long as the surface temperature stays above the Leidenfrost point. …
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Pool Boiling of FC 770 on Graphene Oxide Coatings: A Study of Critical Heat Flux and Boiling Heat Transfer Enhancement Mechanisms
This thesis investigates pool boiling heat transfer from bare and graphene-coated NiCr wires in a saturated liquid of FC 770, a fluorocarbon fluid. Of particular interest was the effect of graphene-oxide platelets, dip-coated onto the heater surface, in enhancing the nucleate boiling heat transfer …
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Pool and flow boiling of novel heat transfer fluids from nanostructured surfaces
Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints …
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An Experimental Investigation of Electrowetting Modulated Nucleate Boiling
… application of EW in enhancing nucleate boiling heat transfer. The working approach capitalizes on the complimentary roles of hydrophobicity and hydrophilicity in the fundamental processes of nucleate boiling, and takes advantage of the ability of EW to dynamically alter the surface wettability …
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The fabrication of nano-scale engineered surfaces to investigate the enhancement of boiling heat transfer and CHF in nuclear reactors
… oxide fuel, the project aims to increase the heat flux limit, i.e., the critical heat flux (CHF), resulting in a boiling crisis. That allows for improvement on the safety margins and operation at higher power. The exact procedure for growing the nanowires will be delineated such that the …
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Pool boiling heat transfer characteristics of nanofluids
… enhancement (up to 200%) of the boiling Critical Heat Flux (CHF) at modest nanoparticle concentrations (50.1% by volume). Since CHF is the upper limit of nucleate boiling, such enhancement offers the potential for major performance improvement in many practical applications that use …
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