Jet impingement onto a solid boundary is of practical interest in a variety of engineering applications. The novelty of the current work is in the comparison of the single and multiple inline jets, the latter being more prevalent in application but less examined in the literature. The study focuses explicitly on the incompressible, hydraulic comparison, by performing experiments near room temperature and low speeds. Three round jets of diameter 22.23 mm are placed inline and 2 diameters apart on the ceiling of the test section. The jets issue vertically downward into a pseudo-unconfined domain whose bottom surface is 9.8 diameters from the jet outlets, acting as the plate. Three distinct flow rates are measured via Stereoscopic Particle Image Velocimetry (S-PIV) for both the single jet and triple jet geometries, where for the latter, each outlet is set to an equivalent flow rate. Several reference parameters further delineate fluid properties in the test section and ambient environment. The investigation begins with evaluation of the single jet, comparing first and second order turbulence statistics with existing literature. The triple jet cases are then presented, showing dramatically different behavior. The results of each configuration, inlet profiles, reference parameters, and uncertainty quantification are provided to embolden future work in computational fluid dynamics (CFD). The investigation concludes with the promotion of several comparisons of the single and triple jet setup and is meant to provide insight into the expected dynamic response of the fluid near and along the solid boundary.
The Thermal-hydraulic Optimization, Analysis, and Scoping Tool (TOAST) is developed to support the thermal-hydraulic aspects for the design of optimal irradiation vehicles for the Nuclear Materials Discovery and Qualification initiative (NMDQi). TOAST is currently a MATLAB-based tool that utilizes a simplified steady-state analytical model where a radial thermal resistance circuit is utilized to account for conduction through up to 2 capsules, a gas gap, a thermal bond, a sample cladding, and a sample, as well as the convection from a water coolant outside the capsules. The geometry is discretized axially along the user-defined height of a basket with a user-defined number of points/nodes, essentially turning TOAST into a semi-2D heat transfer analysis utility for cylindrical irradiation vehicles with practically any configuration, solving for temperatures radially at multiple axial locations. TOAST utilizes a Graphical User Interface (GUI) in-which a user can define the geometrical layout, the materials utilized for each component, the coolant characteristics, and the required solution. The user can define the geometry by inputting the diameters, thicknesses, and heights for each component, whereas the materials are defined via the user-provided constant or variable thermal conductivities. The user can select the coolant's inlet temperature, pressure, and the pressure drop across the height of the problem (which is used to calculate the velocity of the flow). Finally, the user can choose to solve for a sample heat generation rate limit by inputting temperature limits for the sample and capsules or can choose to purely solve for the axial temperature distributions of each component by inputting a pre-selected heat generation rate. Either way, TOAST provides the user with axial temperature distributions of all the components including the coolant, and the heat generation rate limit as well as the maximum outlet coolant temperature. The user can also choose to do one of 6 sensitivity analyses in TOAST. The sensitivity analyses yield plots of the sensitivity of the heat generation rate limit, the maximum coolant temperature, and the pressure limit for the annular components due to perturbations in 1-2 unknown variables based on the selected sensitivity analysis. Benchmarks between computations in TOAST and equivalent 2D axis symmetric ABAQUS models are presented, showing that TOAST results are within less than 3% of ABAQUS results in most cases, and a maximum of 8% difference in some cases. The benchmarks also revealed that this uncertainty is tied to the selection of an appropriate Nusselt number correlation and appropriate thermal conductivities, which the user can do from the GUI. Regardless, TOAST is demonstrated as a computationally efficient, highly accessible, and accurate utility for optimization and scoping s of studies different irradiation vehicles.
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