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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 20 of 91 for “"void fraction"”.
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The void fraction in headers of microchannel heat exchangers
… to other traditional heat exchangers. The void fraction in the headers affects the thermal performance, refrigerant charge, and total pressure drop of MCHEs. However, due to the complex geometry of headers, measurements of void fraction in headers are challenging. A model that predicts the …
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Modeling the pultrusion process to obtain low void fraction composites
… target area for improving composites is the fraction of voids in the final product. The presence of voids in a composite decreases the Interlaminar Shear Strength, provides a site for the formation of fractures, and increases the susceptibility of the part to outside contaminants.;In this …
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Development of capacitive sensor to determine void fraction in horizontal and vertical tubes
This study first presents flow regimes and void fraction in horizontal and vertical tubes with R134a in the adiabatic condition and low mass flux range. Visualization results of horizontal flow patterns are compared to Wojtan-Ursenbacher-Thome flow regime map and have a good agreement. Both void …
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Flow pattern mapping of horizontal evaporating refrigerant flow based on capacitive void fraction measurements
… designed and constructed. Secondly, a capacitive void fraction sensor was developed to study the dynamic behavior of two-phase flows. The capacitance transducer can measure dynamic signals of fluids with the capacitance of the liquid smaller than 1pF and still achieve a SNR greater than 300. …
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Assessment of Multi-Phase-CFD Frameworks for High Void Fraction Flow in Large Diameter Systems
Multi-phase CFD is widely applied to low void fraction bubbly flows in small geometry applications. At high void fraction flows, complex interactions occur that make their modeling challenging. Hybrid models have been proposed for application to such conditions as they resolve large structures …
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Measurement of near-surface void fraction and macrolayer thickness in boiling water and silica-based nanofluid
… 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 water and R-123, respectively, and an error of 5.2% and 7.1% for …
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Void fraction measurements in large (0.3 m) diameter bubble column using Wire Mesh Sensor and Pressure transducers- Effect of sparger
… is to report the spatial measurements of the void fraction distribution in a 30 cm diameter cylindrical bubble column using Wire Mesh Sensor (WMS) tomography and Pressure Transducers. Pair of WMS sensors, with a 64×64 wire configuration of each sensor, were installed which are separated by a …
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Void fraction measurements in a large (0.3 m) diameter bubble column using Wire Mesh Sensors and Pressure Transducers: Effect of Spargers
… is to report the spatial measurements of the void fraction distribution in a 30 cm diameter cylindrical bubble column using Wire Mesh Sensor (WMS) tomography and Pressure Transducers. Pair of WMS sensors, with a 64×64 wire configuration of each sensor, were installed which are separated by a …
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Sensitivity of the Two-Fluid Model to Constitutive Correlations for Large Diameter Pipes
… the nuclear industry, simulations predicting the void development in the core are required to be highly accurate. This work evaluated the sensitivity of the void fraction and interfacial area concentration predictions to changes in correlations used to calculate three parameters that are used to …
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Two-Phase Flow Measurement using Fast X-ray Line Detector System
Void fraction is an essential parameter for understanding the interfacial structure, and heat and mass transfer mechanisms in various gas-liquid flow systems. It becomes critically important to accurately measure void fraction as advanced high fidelity two-phase flow models require high-quality …
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Characterization of Two -Phase Flow in Microchannels
… performance: heat transfer, pressure drop, and void fraction. The purpose of this investigation is the experimental investigation of void fraction and frictional pressure drop in microchannels. A flow visualization analysis is another important goal for two-phase flow behavior understanding and …
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An experimental study of air entrainment by breaking waves
… volumetric concentrations of air (0.3% to 100% void-fraction) found immediately beneath breaking waves. Instrumentation based on the change of electrical impedance of the bubbly mixture with change in void-fraction is developed. Laboratory measurements are conducted in a wave channel and in a …
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Developing Adiabatic Two-Phase Flow
… to evaporators. A method for determining the void fraction from the visualization results was developed and presented. This method allows for a local, instantaneous or time averaged, void fraction determination in Stratified, Intermittent, and Annular flows and could conceivably be implemented …
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A study of two-phase flow in a large diameter horizontal pipeline and the measurement of interfacial level gradient in smooth stratified flow conditions
… diameter pipeline, where the pressure drop and void fraction were measured. The pressure drop was measured using 23 bottom tapping points along a 34 m test section. The results were compared with six well known pressure drop models; these models did not allow for diameter size effect, it was …
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Numerical study of vertical subcooled boiling flow with new wall nucleation models
… was found that significant under-predictions of void fraction resulted from implementing new wall nucleation models. Reasonable prediction of gas velocity could only be obtained at Port 3 at high pressures. With a specific combination of built-in models, reasonable results of void fraction …
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Probabilistic Flow Regime Map Modeling of Two -Phase Flow
… to develop models for two-phase heat transfer, void fraction, and pressure drop, three key design parameters, in single, smooth, horizontal tubes using a common probabilistic two-phase flow regime basis. Probabilistic two-phase flow maps are experimentally developed for R134a at 25°C, …
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STUDY OF THREE-PHASE AIR-BRINE-SALT COUNTERFLOW IN AN INCLINED PIPE
… (length, velocity, depth, frequency), void fraction, and solid particle velocity. This study introduces a novel flow-regime map combining concurrent and countercurrent flow regimes. Empirical equations were developed to predict average bubble length, depth, velocity, and cross-sectional …
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Non-intrusive two-phase flow regime identification and transport characterization in microchannels subject to uniform and non-uniform heat input
… regime. Development of sensors that detect local void fraction and flow regimes may enable better understanding of the fundamental flow phenomena. ^ The void fraction in air-water two-phase adiabatic flow in a microchannel is measured in this work using a custom-designed impedance-based sensor …
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Steam condensation in flattened-tube air-cooled condensers
… plants away from large water sources and to avoid a lengthy environmental permitting process. In addition, the environmental benefits of reducing power-plant water consumption are significant. However, the lower thermal performance of air-cooling in comparison to water-cooling makes the cost …
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Inverse uncertainty quantification of trace physical model parameters using Bayesian analysis
… or two-phase pressure drop, axial and radial void fraction distributions, and critical power for a wide range of system conditions. In this thesis, the steady-state cross-sectional averaged void fraction distribution from BFBT experiments is used as the input for inverse uncertainty algorithm, …
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