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Showing 1 to 18 of 18 for “"CHF enhancement"”.
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Study of chemistry and irradiation effects on nanofluids to be used in light water reactor accident cooling
… of nanoparticles in a base fluid, have shown enhancements in both pool boiling and flow boiling critical heat flux (CHF) in laboratory tests. The applicability of this aspect to nuclear reactor post-accident cooling is promising. This study investigates various parameters that should be …
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Determination of pool boiling Critical Heat Flux enhancement in nanofluids
… 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 monotonic relationship between nanoparticle …
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Effects of surface parameters on boiling heat transfer phenomena
… have been shown to enhance pool and flow boiling CHF. The CHF enhancement was due to nanoparticle deposited on the heater surface, which was verified in pool boiling. However, no such work has been done for flow boiling. Using a cylindrical tube pre-coated with Alumina nanoparticles coated via …
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Investigation of downward facing critical heat flux with water-based nanofluids for In-Vessel Retention applications
… Westinghouse AP1000 due to critical heat flux ("CHF") at the outer surface of the reactor vessel. Increasing the CHF level by altering the cooling fluid would increase the safety margin of current design power or allow for higher power. The modification to current licensed design to implement a …
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Critical heat flux enhancement via surface modification using colloidal dispersions of nanoparticles (Nanofluids)
… (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 this study, nanofluids were investigated as an agent to modify a …
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Experimental Investigation of Critical Heat Flux Enhancement on Engineered Surfaces with Infrared Thermometry
… science and engineering. The prediction and enhancement of the heat flux at which this boiling crisis occurs (also known as critical heat flux, or CHF) has been the focus of boiling heat transfer research for over a century, as CHF sets an upper limit to the operating heat flux for …
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Boiling on hierarchical nanoengineered surfaces
… and frequency. Ultrahigh critical heat fluxes (CHF) greater than 400 W/cm2 were obtained, corresponding to an enhancement of ≈245% compared to smooth copper surfaces. Our work reveals the existence of a linear relationship between the surface wickability and CHF enhancement. The fabrication …
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Impact of self-rewetting aqueous solutions on boiling with advanced heat transfer applications
… 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 atmospheric. Pool …
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Measurement of near-surface void fraction and macrolayer thickness in boiling water and silica-based nanofluid
… 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 derived. The optical probe was verified to have an error of 11.9% and 10.4% for measuring bubble diameter in …
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Subcooled flow boiling heat transfer and critical heat flux in water-based nanofluids at low pressure
… 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 pressure. It was …
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Pool boiling heat transfer characteristics of nanofluids
… in water, and exhibit a very significant 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 …
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Investigation of the use of nanofluids to enhance the In-Vessel Retention capabilities of Advanced Light Water Reactors
… a substantial increase in Critical Heat Flux (CHF) compared to water. The use of a nanofluid in the In-Vessel Retention (IVR) severe accident management strategy, employed in Advanced Light Water Reactors, was investigated. A model simulating the two-phase flow and heat transfer on the reactor …
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Micro and nanostructures for two-phase fluid and thermal transport
… at high heat fluxes. A critical heat flux (CHF) of 969 W/cm2 was achieved with a structured surface, a 57% enhancement compared to a smooth surface. The trend of CHF enhancement among different geometries of the structures agrees well with the fluid wicking model, which suggests that …
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Departure from nucleate boiling and pressure drop prediction for tubes containing multiple short-length twisted-tape swirl promoters
… to better characterize the critical heat flux (CHF) enhancement caused by the addition of MSLTTs, this study performed a critical analysis of existing CHF correlations and models. Initially a phenomenological model was sought to describe the mechanisms of CHF for tubes containing MSLTTs; …
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Experimental investigation of effects of surface roughness, wettability and boiling-time on steady state and transient CHF for nanofluids
Critical Heat Flux (CHF) is one of the primary design constraints in a nuclear reactor. Increasing the CHF of water can enhance the safety margins of the current fleet of Light Water Reactors (LWRs) and/or increase their power output. It has been shown that a suspension of nanoparticles called …
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Surface structure enhanced microchannel flow boiling of low surface tension fluids
… performance in terms of critical heat flux (CHF) and heat transfer coefficient (HTC) have also benefited from surface modification, without significantly adding to the overall flow pressure drop. For some microelectronic applications, water may not be the ideal fluid for microchannel flow …
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An experimental study of critical heat flux with surface modification and its analytic prediction model development
The critical heat flux (CHF) condition causes a drastic reduction of heat transfer coefficient and sometimes involves physical failure of the heating surface in heat flux-controlled systems. Understanding of CHF phenomena and reliable CHF prediction model development are necessary to design various …
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An Experimental Investigation of Electrowetting Modulated Nucleate Boiling
… thereby delaying the critical heat flux (CHF). In this work, we demonstrate the creation of such tunable adaptive boiling surfaces, and examine the effects of both direct current (DC) EW and alternating current (AC) EW on the overall boiling heat transfer characteristics. A synchronized …