Cooling of the fusion blanket first wall remains a significant challenge given the adverse conditions of heat and particle flux encountered near the plasma. Helium emerges as an attractive cooling candidate because of...
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Cooling of the fusion blanket first wall remains a significant challenge given the adverse conditions of heat and particle flux encountered near the plasma. Helium emerges as an attractive cooling candidate because of its chemical and neutronic inertness and separability from hydrogenic species (e.g. tritium). Because of the low thermal mass of helium, optimization of these coolant channels is warranted to provide high heat transfer performance at low pumping costs. Increasingly, computational fluid dynamics (CFD) simulations are employed to model and optimize these flow channels, and accompanying experimental data are needed to validate the predictions of these *** provide the aforementioned experimental data, a high-pressure helium flow visualization upgrade has been designed for the Helium flow Loop Experiment facility. This apparatus was built to American Society of Mechanical Engineers boiler and pressure vessel standards to withstand operating pressure of 4 MPa and mated to high-pressure glass windows. Seedless flow visualization is performed via high-speed background oriented schlieren (BOS), with image correlation used for time-resolved two-dimensional velocimetry at frequencies in excess of 60 kHz. Rectangular flow channel test articles are additively manufactured via laser powder bed fusion and installed into this visualization apparatus, with one-sided heating supplied by resistive heaters. The chosen test geometries were informed by prior CFD simulations, and the helium flow structures observed via BOS (detachment, recirculation, etc.) will be used for the validation of these accompanying models, in support of the design and optimization of blanket cooling channel configurations.
A high spatiotemporal resolution technique for instantaneous flow field measurement has been developed, enabling one-dimensional velocimetry and flow field visualization within a converging-diverging nozzle. By employ...
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A high spatiotemporal resolution technique for instantaneous flow field measurement has been developed, enabling one-dimensional velocimetry and flow field visualization within a converging-diverging nozzle. By employing femtosecond laser-induced long-lived, high-intensity plasma emission in a CO2/N2 gas flow, coupled with an ICCD camera, we achieved instantaneous one-dimensional velocity measurements at a frequency of 330 kHz. Spectral analysis indicated that the femtosecond laser-induced plasma emission predominantly originates from the CN (B-X) transition. The intensity and lifetime of the plasma emission were found to be closely dependent on the CO2 concentration, with 1 % CO2 providing optimal performance for velocity measurements. In the CO2/N2 mixture, CO2 undergoes a phase transition to solid nanoparticles under specific temperature and pressure conditions, facilitating high spatiotemporal resolution visualization of flow structures via Rayleigh scattering. The instantaneous images captured the morphology of barrel shocks and normal shocks, as well as the effects of varying release pressures and CO2 concentrations on Rayleigh scattering.
Background-oriented schlieren tomography is a prevalent method for visualizing intricate turbulent flows, appreciated for its ease of implementation and ability to capture three-dimensional distributions of a multitud...
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Background-oriented schlieren tomography is a prevalent method for visualizing intricate turbulent flows, appreciated for its ease of implementation and ability to capture three-dimensional distributions of a multitude of flow parameters. However, the voxel-based meshing scheme leads to significant challenges, such as inadequate spatial resolution, substantial discretization errors, poor noise immunity, and excessive computational costs. This study presents an innovative reconstruction approach termed neural refractive index field (NeRIF), which implicitly represents the flow field using a neural network trained with specialized strategies. Numerical simulations and experimental results on turbulent Bunsen flames demonstrate that this approach can substantially improve the reconstruction accuracy and spatial resolution while concurrently reducing computational expenses. Although showcased in the context of background-oriented schlieren tomography here, the key idea embedded in the NeRIF can be readily adapted to various other tomographic modalities including tomographic absorption spectroscopy and tomographic particle imaging velocimetry, broadening its potential impact across different domains of flow visualization and analysis.
Neutron radiography can visualize heavy oil flows in metallic reactors used to upgrade heavy oils. Thus, we visualized heavy oil flows in a packed bed using real-time neutron radiography to support its capability and ...
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Neutron radiography can visualize heavy oil flows in metallic reactors used to upgrade heavy oils. Thus, we visualized heavy oil flows in a packed bed using real-time neutron radiography to support its capability and to offer basic experimental data necessary for verification and validation of numerical simulations. Atmospheric residue was used as the heavy oil sample and heavy oil and N-2 gas were concurrently supplied into a packed bed from above a reactor simulating a trickle bed reactor. Reactor temperatures were set at either 100 degrees C or 250 degrees C to change heavy oil viscosity. The heavy oil flow rate was kept constant at 2.5 mL/min and the N-2 gas flow rate was set at either 1 L/min or 3 L/min at 25 degrees C. A series of neutron radiography experiments was conducted at the B-4 neutron imaging facility in the Kyoto University Research Reactor (KUR) with a thermal neutron flux of 5 x 10(7) n/cm(2).s. We performed image processing for the neutron radiographs to calculate neutron beam attenuation and clarify flow behavior. visualization results show differences in flow behavior depending on operating factors. Temperature had a particularly substantial effect on flow behavior because heavy oil viscosity depends strongly on temperature. The flows also showed different behaviors for 1 mm and 3 mm packed particle sizes because the void ratios in the packed bed, which were preliminarily observed by X-ray computational tomography (CT), change with particle size. Channeling flow was observed with 3 mm particles and a temperature of 250 degrees C. Furthermore, this work suggests that neutron radiography can be used to investigate heavy oil flows in metallic reactors. (C) 2018 Elsevier Ltd. All rights reserved.
An experimental model of a vaned diffuser with rectangular flow cross-sections was constructed of clear plastic for flow visualization studies. A swirl generator was used to induce fluid rotation without subjecting th...
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An experimental model of a vaned diffuser with rectangular flow cross-sections was constructed of clear plastic for flow visualization studies. A swirl generator was used to induce fluid rotation without subjecting the diffuser to any unsteady and irregular impeller flow phenomena. The blades were of a thin circular arc shape. The clear plastic construction allowed large-scale flow visualization with tufts attached to the diffuser wall and dye injected into the separation regions. Four conditions were tested: a vaneless, a four-vaned, a six-vaned, and eight-vaned diffuser. Each test was conducted at an average Reynolds number of 20 000, based on passage thickness. In the absence of diffuser blades the flow angle was not radially constant, as a result of the viscous effects, varying as much as 11° from the ideal 16°. With four blades installed, separation began at 23% of the blade length from the leading tip. At the peak development of the separation regions 34% of the flow area was blocked. Separation began at 27% from the leading edge when six blades were used. Finally, with eight blades in place, separation began at 50% of the blade length from the leading tip; at the peak development of the separation regions 64% of the flow area was blocked.
Effusion cooling can be one of the attractive methods of cooling in a current high-efficiency gas turbine which has a very hot gas temperature above 1600 A degrees C. For higher effectiveness of the air cooling for a ...
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Effusion cooling can be one of the attractive methods of cooling in a current high-efficiency gas turbine which has a very hot gas temperature above 1600 A degrees C. For higher effectiveness of the air cooling for a gas turbine vane and blade, the air-cooled flow through effusionholes should not overshoot into the mainstream flow but still remain within the mainstream boundary layer. The present study is intended to examine flow structure of a microscale effusion cooling for gas turbine applications through flow visualization which is highly effective to obtain better understanding of the flow physics. The air flow through effusion-holes can be visualized with an oil atomized droplets, a laser-sheet and a high-speed CCD imaging system. The qualitatively visualized results show their flow patterns and characteristics with different effusion hole size and blowing ratio for effusion cooling. A series of vortical structure can be observed within the boundary layer along the microscale effusion flat plate which provided that the effusion cooling can be a plausible candidate up to the effusion-hole size of 0.7 mm.
This article presents an experimental and numerical study of the water-flooding process with different horizontal and vertical well configurations using flow visualization technique. The effect of horizontal wells on ...
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This article presents an experimental and numerical study of the water-flooding process with different horizontal and vertical well configurations using flow visualization technique. The effect of horizontal wells on flood profile has been investigated by using two different well configurations, viz., horizontal injection-vertical production (HI-VP) and vertical injection-horizontal production (VI-HP). The experimental results show that HI-VP configuration recovers more oil than VI-HP configuration. The commercial simulator, ECLIPSE, is used for simulating the flood profiles for these well configurations. A good agreement is observed with the experimental flood profiles. Further simulations are carried out with varied perforation lengths and well positions to find out the optimal well configuration for both HI-VP and VI-HP. Such flow visualization experiments can be used as a validation tool for numerical simulators.
A phenomenon of ac gas-phase needle-plate corona discharge induced electrohydrodynamic (EHD) liquid flow in a stratified fluid has been investigated experimentally. The flow visualization of flow pattern is carried ou...
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A phenomenon of ac gas-phase needle-plate corona discharge induced electrohydrodynamic (EHD) liquid flow in a stratified fluid has been investigated experimentally. The flow visualization of flow pattern is carried out by a fluorescent dielectric liquid tracer, where the steady EHD liquid motion induced by the corona discharge is presented in visual impressions. The results show that the EHD liquid flow direction on an electrode axis is not from needle to plate electrodes axis when the needle position was above the liquid layer. For the case of the needle electrode tip immersed into the dielectric liquid, it is well known that the dielectric liquid flows in anticlockwise rotation by contraries. The flow velocity distribution is experimentally obtained by a particle image velocimetry with image processing, where the measurement system takes sequential digital images of flow field illuminated by a laser light sheet for computed tomography. The mechanistic model based on interfacial momentum transfer effects on liquid-phase fluid motion is discussed in detail.
This research aims to study the internal flow visualization of a miniature loop thermosyphon for several ratios of the internal diameter of the condenser section to the internal diameter of the evaporator section and ...
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This research aims to study the internal flow visualization of a miniature loop thermosyphon for several ratios of the internal diameter of the condenser section to the internal diameter of the evaporator section and temperature. The miniature loop thermosyphon will separate gas and condensed liquid, which flow in opposite directions. This not only prevents flooding and drying out, it also increases heat transfer efficiency. The miniature loop thermosyphon consists of three sections, namely evaporator, adiabatic, and condenser sections. The return liquid channel is connected between the condenser and evaporator to convey the condensed liquid. The miniature loop thermosyphons are designed at three internal diameters of the condenser section to the internal diameters of the evaporator section ratios, which are 1.4, 1.6, and 1.8. The evaporator section consists of a copper tube with an internal diameter of 14 mm and a length of 135 mm. The adiabatic section consists of a glass tube with an internal diameter of 14 mm and a length of 135 mm. The condenser section consists of a copper tube with internal diameters of 19, 22, and 25 mm and a length of 135 mm. The return liquid channel consists of a glass tube with an internal diameter of 2.4 mm and a length of 135 mm. Ethanol was used as the working fluid, filled at 50% of internal volume of the evaporator section. It was found that the miniature loop thermosyphon can separate gas and condensed liquid that flows in the opposite direction at all internal diameter of the condenser section to the internal diameter of the evaporator section ratios. As the internal diameter of the condenser section to the internal diameter of the evaporator section ratio increases, the flow of gas and liquid is changed from a violent bubble flow to a churn flow, the velocity at liquid return channel decreases, and the heat transfer decreases.
The three-dimensional flow dynamics of a cylindrical cyclone with tangential inlet and tangential exit with an aspect ratio of 2 and 4 was studied using flow visualization. Photographs of circular and longitudinal cro...
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The three-dimensional flow dynamics of a cylindrical cyclone with tangential inlet and tangential exit with an aspect ratio of 2 and 4 was studied using flow visualization. Photographs of circular and longitudinal cross sections of the cylinder revealed stable three-dimensional flow structure in the cylinder. The primary flow was observed to follow a helical pattern that surrounded a secondary flow. The secondary flow was characterized by a single vortex that circulated around the cylinder axis and occupied a large fraction of the cylinder diameter. The secondary flow was seen to include two cells of rotation in skewed planes for an aspect ratio of 2 and four cells for an aspect ratio of 4. Qualitatively, no change in flow structure was seen for a Reynolds number of 15,000-60,000.
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