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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 18 of 18 for “"departure from nucleate boiling"”.
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Prediction of departure from nucleate boiling in PWR fast power transients
… between use of steady state versus transient Departure from Nucleate Boiling (DNB) models, for fast power transients under forced convective heat exchange conditions. Theoretical DNB models based on liquid film thickness variation are adapted and modified from existing studies into a …
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Departure from nucleate boiling and pressure drop prediction for tubes containing multiple short-length twisted-tape swirl promoters
… between core pressure drop and the minimum departure from nucleate boiling ratio (MDNBR). In order to increase the power density of the IPWR, Ferroni [231 examined the possibility of inserting multiple short-length twisted-tapes (MSLTTs) in the cooling channels. For a fixed coolant mass flow …
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Design and Construction of a Subcooled Boiling Flow Loop with an Internally Heated Vertical Annulus for Use in Testing Departure from Nucleate Boiling (DNB)
… and testing of an apparatus to use in subcooled boiling flow experiments. A vertical annulus flow loop was design to mimic a rod used in a reactor boiler. The system was tested at different velocities and temperatures to verify it could be used in a range of experiments to try and match real …
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Infrared Thermometry Analysis of Surface Effects in Subcooled and Saturated Boiling of Water
… the dynamics of subcooled and saturated flow boiling are studied, focusing on the influence of surface characteristics, visualized through advanced diagnostics capturing micro-scale phenomena. Utilizing specially crafted thin-film infrared heaters, we measured bubble dynamics parameters and …
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Investigation of the use of nanofluids to enhance the In-Vessel Retention capabilities of Advanced Light Water Reactors
… water to be achieved, while holding the Minimum Departure from Nucleate Boiling Ratio (MDNBR) constant. A nanofluid injection system that would take advantage of the enhanced CHF properties of the nanofluid in order to provide a higher safety margin than the current IVR strategy or, for given …
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Application of Optical Fiber Sensors for Quenching Temperature Measurement
… of meltdown greatly increases. While the nucleate boiling and film boiling regimes have been well-investigated, the transition boiling regime between the point of departure from nucleate boiling (DNB) and the minimum film boiling temperature (T<sub>min</sub>) remains difficult to study. …
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Feasibility and economics of existing PWR transition to a higher power core using annular fuel
… this mixed core is investigated and the Minimum Departure From Nucleate Boiling is found to be either unaffected or even improved by using a mixed core. Consequently, a neutronic model is developped to verify and validate the neutronic feasibility of the transition from solid fuel to annular fuel.
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Investigation and characterization of pressure drop in evenly spaced twisted tapes
… increase the critical heat flux (CHF) at which departure from nucleate boiling occurs. Shortlength twisted tapes were proposed in his study because they offer the benefits of increased heat transfer and CHF, but also introduce a smaller pressure drop than a full-length twisted tape insert. This …
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Influence of wettability on boiling heat transfer and critical heat flux in vertical flow boiling
… of heat transfer systems that utilize two-phase boiling heat transfer. In a heat-flux-controlled system, exceeding the CHF results in rapid temperature excursions which can be catastrophic for system components. In nuclear power generation, the initiation of a CHF event may cause fuel damage …
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Experimental Investigation of Subcooled Flow Boiling and CHF at Prototypical Pressures of Light Water Reactors
Boiling crisis is an important phenomenon that affects the performance and safety of pressurized water reactors (PWRs). Accurate predictions of the boiling crisis are difficult to make because they require a clear understanding of the physical mechanisms leading to the boiling crisis combined with …
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An inverted pressurized water reactor design with twisted-tape swirl promoters
… hydraulics and neutronics design constraints from which it was concluded that the maximum achievable power for the IPWR design was 4078MW, 19 percent higher than the reference PWR (the Seabrook Power Station), limited simultaneously by the core pressure drop and steady state departure from …
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Transient flow boiling CHF under exponentially escalating heat inputs
… as the fuel composition. During such an event, boiling of the water coolant can provide not only an effective way of heat removal, but also a stabilizing, negative reactivity feedback. However, the reactor power could reach extremely high levels and lead to a boiling crisis, e.g. by departure …
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Experimental study of flow boiling under subatmospheric pressures in a vertical square channel
… and Critical Heat Flux (CHF) in subcooled boiling flows under subatmospheric pressure. Forced convection boiling is a widely used and effective means of heat transfer. An understanding of the mechanisms and limitations involved in forced convection boiling is important for the accurate …
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Autonomous Experimentation to Accelerate Boiling Heat Transfer Research
Boiling heat transfer stands out as a highly efficient method for dissipating heat, utilized across a spectrum of engineering systems ranging from nuclear reactors to computer processing units. Over the course of decades, researchers have heavily relied on direct visualization of boiling phenomena …
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High-Resolution Experimental Measurements and Mechanistic Modelling of Saturated Cryogenic Pool Boiling Heat Transfer
… e.g., a fuel depot placed in orbit. The low boiling point of cryogenic fuels (hydrogen, methane, oxygen) makes them prone to boil when transferred through superheated pipes, or simply stored in fuel tanks, resulting in the presence of two-phase mixture. Boil-off gas can lead to pressurization …
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Achievable power uprates in pressurized water reactors using uranium nitride fuel
… limits considered are pressure drop, minimum departure from nucleate boiling ratio, fretting and sliding wear and fuel average and centerline temperatures. These limits were set by the reference design's performance. Two strategies were used to raise the core power while remaining within …
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Application of advanced fuel concepts for use in innovative pressurized water reactors
… water reactor (PWR) environment. In the switch from a UO2 with zirconium-based cladding to any other combination, there is a multitude of questions that need to be answered. This work examines three of these knowledge gaps: (1) the disposition of weapons-grade plutonium in thorium and silicon …
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Development of optimized core design and analysis methods for high power density BWRs
… MPa. The core exit quality is increased to 19% from the ABWR nominal exit quality of 15%. The pin linear heat generation rate is 20% lower, and the core pressure drop and mass of uranium are 30% lower. The BWR-HD's fuel, modelled with FRAPCON 3.4, showed similar performance to the ABWR pin …