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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Methods for making heat transfer devices include forming a jet plate with a plurality of inclined jets set at an angular deviation from normal. A bottom plate is formed with channel walls that have ribs. The jet plate is attached to the bottom plate to form ribbed channels. The angular deviation of each inclined jet establishes a jet direction perpendicular to a long dimension of the ribbed channels.
This work presents a novel wave energy converter device concept that combines a submerged pressure differential plate with variable geometry modules. The two variable geometry sections, placed at the force and aft locations on the plate, consist of five identical flaps that are opened in ascending order starting with the flaps closest to the edges of the plate and moving inward. The variable geometry modules act as control surfaces that allow for the hull geometry to be adjusted leading to changes in the hydrodynamics. The device geometry is controlled in a quasi-static fashion while the power-take off (PTO) unit would be controlled on a wave-to-wave time scale. The submerged plate is tethered directly to the seabed by integrated mooring and PTO lines eliminating the need for a second reaction body. A linear frequency domain analysis is used to evaluate device performance in terms of absorbed power, PTO force, and absorber body motion. The frequency domain analysis required the linearization of the PTO dynamics to couple the fore and aft PTOs to the motion of the absorber body. The inclusion of the variable geometry modules was shown to be effective at altering the device geometry to provide changes in the absorber hydrodynamics to produce measurable reductions in structural and PTO loading.
An absorber for an absorption refrigeration system for a vertically mounted plate absorber has fins positioned over the plate to promote distribution of a fluid under flow as a nearly continuous thin film. The absorber has rows of fins that are evenly spaced with the fins occupying a portion of the active width of the plate with adjacent rows offset by the width of the plate. A combined evaporator-absorber module is constructed with the absorbing face of the absorber parallel with an evaporating surface of an evaporator where absorber solution and refrigerant fall as parallel falling sheets of liquid. The absorber is covered with a porous hydrophobic membrane to isolate the falling absorber solution from the falling liquid refrigerant.
This paper provides an overview of the base model specifically developed to perform parametric sensitivity studies on the U-10Mo monolithic fuel system. U-Mo monolithic fuels are being considered for the conversion of test reactors into high-performance research reactors that operate using proliferation-resistant, low-enriched uranium (LEU) fuels. These plate-type fuels contain a high-density, low-enrichment fuel sandwiched between zirconium diffusion barriers and encapsulated in aluminum claddings. All U.S. high-performance research reactors have released the designs of their LEU monolithic fuel reactor cores. These designs include nearly 50 distinct fuel plate geometries with different operational parameters. Consequently, a single generic plate geometry representing all the extreme points in this design matrix is unrealistic. To evaluate the performance for various parameters, a set of sensitivity studies was performed. These studies considered various input parameters (i.e., geometric, operational, and material property-related). The results revealed valuable information about plate performance and the sensitivity of this performance to various modeling inputs. To establish a reference state for comparing these result, base model featuring representative irradiation conditions was developed. To capture in-reactor behavior accurately, incorporation of representative constitutive models capable of evolving properties with respect to temperature, irradiation time, and burnup was needed. The behavioral models considered burnup-dependent properties, swelling, creep, and degradation. This paper introduces the base model created for the parametric sensitivity studies. The detailed description of the procedure includes the model geometry, model discretization, thermo-mechanical coupling, material properties and behavioral models. This paper also provides selected results and assesses the performance of the base model.
Radon daughter plate-out may pose a fundamental limitation to realizing large-scale superconducting quantum computers. Radon daughters plated-out on a superconducting qubit can decay, releasing energy into the substrate, producing phonons. Phonon-induced quasiparticles then generate bit-flip errors and reduce coherence times. We seek to increase plate-out on chips to enable future study of the impact of radon on coherence times. In this project, we utilize COMSOL Multiphysics simulations to visualize electric field configuration and model ion transport to finalize design of a device to increase radon plate-out on qubit chips.
Experimental study on cross-flow air-cooled plate heat exchangers (PHEs) was performed. The two prototype PHEs were manufactured in a stack of single-wave plates and double-wave plates in parallel. Cooling air flows through the PHEs in a crosswise direction against internal cooling water. The heat exchanger aims to substitute open-loop cooling towers with closed-loop water circulation, which guarantees cleanliness and compactness. In this study, the prototype PHEs were tested in a laboratory scale experiments. From the tests, double-wave PHE shows approximately 50% enhanced heat transfer performance compared to single-wave PHE. However, double-wave PHE costs 30% additional pressure drop. For commercialization, a wide channel design for air flow would be essential for reliable performance. (author)
A brief review of exact two-dimensional supersonic flow theory and Ackeret's linearized theory are first presented. The lift and drag coefficients of a cascade of flat plates are calculated exactly and compared to those obtained using the linearized theory. The forces on the cascade are determined for unsteady inlet flow. The flat plate cascade theory is extended to compute the efficiency of a supersonic propeller with friction and finite blade thickness.
By using the method of compliance functions and the Hankel transformation of the first order, we propose a procedure for the solution of the problem of torsion of a multilayer plate with elastic links between the layers. Two auxiliary functions connected with the transforms of stresses and displacements at the points of the top boundary of the layer are introduced for each layer. The recurrence relations for the auxiliary functions and the compliance functions of neighboring layers of the plate are constructed. For a two-layer plate, we analyze the influence of the coefficients of elastic links and the geometric and mechanical parameters of layers on the distribution of stresses at points of the common boundary of the layers.
In the present paper, inhomogeneities in the microstructure and mechanical properties of a modified AZ80 plate under industrial production conditions were investigated. The results indicated that the microstructure of the edge and middle region shows more homogeneous and fine recrystallized grains. Additionally, more coarse recrystallized grains existed between the edge and the middle region. The ultimate tensile strength and yield strength of the edge region of the plate are maximal (287 and 162 MPa), and those near the 1/8 W region are minimal (259 and 152 MPa). The grain size increased from 19.5 to 27.2 μm along the center layer to the surface layer. The ultimate tensile stress (yield stress) increases from 258 (121 MPa) to 284 MPa (176 MPa) in the direction from the surface layer to the middle layer. The microhardness decreased from the surface layer (72HV) to the center layer (64HV). The metal strain state and temperature distribution lead to different degrees of dynamic recrystallization, which causes the microstructure and mechanical properties of the plate.
For biomass processing systems, feedstocks with small but equal sizes can improve flowability and thermochemical outputs. The Crumbler rotary shear system was designed to achieve such ideal feedstocks to reduce costs and energy throughout the biomass supply chain. Improving the wear resistance of major components in this system is important to decrease the cost. Accelerating the feedstock flow through the rotary shear machine plays an equivalent role of improving its efficiency. An analytical analysis and a finite-element analysis of the stationary clearing plate are presented in this work. Here, these tools are used to investigate the effect of contact surface curvature on the impact pressure. The optimized new clearing plate design is expected to improve the component’s lifetime and wood chips flowability. The field tests confirm that the trend of the new clearing plate design guided by FEA. The optimization method, model verification, and validation experience applied in this work can also be applied to other static components with similar simple contact wear problems.
An experimental study of the effects of turbulent flow regime on the flame structure is conducted by using perforated-plate-stabilized, hydrogen-piloted, lean premixed methane/air turbulent flames. The underlying turbulent flow field was investigated using two-dimensional three-component particle imaging velocimetry (2D3C-PIV) with two perforated plates of different blockage ratios. The flow data allowed a separation of the turbulent flow regime into axial velocity stream dominated and vortex dominated flows. A plate with 62% blockage ratio was used to establish the stream-dominated flow regime and another with 86% blockage ratio was used to establish the vortex-dominated flow regime. OH laser-induced fluorescence was used to study the effects of the turbulent flow regime on the mean progress variable, flame brush thickness, flame surface density, and global consumption speed. In comparison with the stream-dominated flow, the vortex-dominated flow makes a wider and shorter flame. Also, the vortex-dominated flow has a thicker horizontal flame brush and a thinner longitudinal flame brush. Especially, the spatial variation of the horizontal flame brush thickness for the vortex-dominated flow does not follow the turbulent diffusion theory. The vortex-dominated flow shows a relatively constant flame surface density and the stream-dominated flow shows a decreasing flame surface density along the streamwise direction. The flame surface density for the vortex-dominated flow is higher than the one for the stream-dominated flow. Lastly, the vortex-dominated turbulent flow shows a much higher consumption speed in comparison with that of the stream-dominated turbulent flow with identical velocity fluctuation levels.
Herein, this study, which has been motivated by the recent applications of the cold plate device in aviation thermal management, reports on physics-based mathematical models derived from the conservation laws of mass, momentum, and energy, and empiricism-based models. One of the objectives of the present work is to report on an elaborate and successful experimental work carried out on an additively manufactured device for the purpose of rigorously validating the numerical predictions. The excellent agreement between the numerical predictions and measured performance provides much needed confidence in the implementation, in the software package, of the offset-strip fin passage correlations, as well as in the software implementation of user-defined wavy fin correlations for aerospace heat exchangers and cold plates operating with ram air at Reynolds numbers below 8000. The contributions of this work can also be found in the development of a new and accurate thermal-hydraulic analysis procedure, referred to in this paper as plate-fin analogy. Results from this procedure are compared with those from thermal resistance network. The comparative study in this paper of the bulk and discrete enthalpy flux method is also new, as is the relative assessment of four off-set strip fin thermal-hydraulic models.
An experimental method is introduced that uses microprobe Li/Cu reference electrodes to map "safe" charging regimes to avoid Li metal plating on graphite anodes at rates to 8C. With this method, a Li-ion cell closely approaches the Li plating condition but avoids descending into this regime. This "safe" approach is used to demonstrate effects of the microporous separator on Li plating in cells consisting of a layered nickel-manganese -cobalt oxide cathode and graphite anode. We argue that most of the difference in behaviors for different separators arises from time delayed Li + ion percolation through the membrane. In conclusion, our study suggests that explicitly treating kinetics of phase transitions in the lithiated graphite anode is essential for electrochemical models predicting "safe" lines for fast charging cells.
Three research reactors with involute-shaped fuel plates are pursuing conversion from highly enriched uranium to low-enriched uranium fuel. Various core design and safety evaluation studies are essential to assess the feasibility of the conversion. The use of 3D computational multiphysics codes is being explored in these analyses and therefore they must undergo a thorough evaluation and quality assurance process due to their potential impact on nuclear safety. Here, the Cheverton and Kelley physical tests performed in the late 1960s to investigate the deflections of HFIR’s outer plate under uniform pressure and temperature fields are simulated by employing commercially available computational codes, with the goals to (1) verify and validate the models and numerical solvers implemented in the codes for thermomechanical analysis of involute reactor plates and (2) to develop a benchmark computational test to evaluate future versions of existing software or newly developed computational codes. The results of the simulations showed good agreement with each other as well as against the Cheverton–Kelley experimental data. Some minor deviations were observed for a few multiphysics cases and their potential origins and impact on the analysis results is investigated in the paper. The validated models increase the confidence in using multiphysics codes to evaluate existing or new LEU designs.
We report the ability to image light elements in both crystalline and noncrystalline materials at near atomic resolution with an enhanced contrast is highly advantageous to understand the structure and properties of a wide range of beam sensitive materials including biological specimens and molecular hetero-structures. This requires the imaging system to have an efficient phase contrast transfer at both low and high spatial frequencies. Here, we introduce a new phase contrast imaging method in a scanning transmission electron microscope (STEM) using a pre-specimen phase plate in the probe forming aperture, combined with a fast pixelated detector to record diffraction patterns at every probe position, and phase reconstruction using ptychography. The phase plate significantly enhances the contrast transfer of low spatial frequency information, and ptychography maximizes the extraction of the phase information at all spatial frequencies. In addition, the STEM probe with the presence of the phase plate retains its atomic resolution, allowing simultaneous incoherent Z-contrast imaging to be obtained along with the ptychographic phase image. An experimental image of Au nanoparticles on a carbon support shows high contrast for both materials. Multislice image simulations of a DNA molecule shows the capability of imaging soft matter at low dose conditions, which implies potential applications of low dose imaging of a wide range of beam sensitive materials.
We report that Li metal is the preferred anode material for all-solid-state Li batteries. However, a stable plating and stripping of Li metal at the anode–solid electrolyte interface remains a significant challenge particularly at practically feasible current densities. This problem usually relates to high and/or inhomogeneous Li-electrode–electrolyte interfacial impedance and formation and growth of high-aspect-ratio dendritic Li deposits at the electrode–electrolyte interface, which eventually shunt the battery. To better understand details of Li metal plating, we use operando electron microscopy and Auger spectroscopy to probe nucleation, growth, and stripping of Li metal during cycling of a model solid-state Li battery as a function of current density and oxygen pressure. We find a linear correlation between the nucleation density of Li clusters and the charging rate in an ultrahigh vacuum, which agrees with a classical nucleation and growth model. Moreover, the trace amount of oxidizing gas (≈10 –6 Pa of O 2 ) promotes the Li growth in a form of nanowires due to a fine balance between the ion current density and a growth rate of a thin lithium-oxide shell on the surface of the metallic Li. Interestingly, increasing the partial pressure of O 2 to 10 –5 Pa resumes Li plating in a form of 3D particles. In conclusion, our results demonstrate the importance of trace amounts of preexisting or ambient oxidizing species on lithiation processes in solid-state batteries.
Metallic lithium deposition on graphite anodes is a critical degradation mode in lithium-ion batteries, which limits safety and fast charge capability. A conclusive strategy to mitigate lithium deposition under fast charging yet remains elusive. Herein, we examine the role of electrode microstructure in mitigating lithium plating behavior under various operating conditions, including fast charging. The multilength scale characteristics of the electrode microstructure lead to a complex interaction of transport and kinetic limitations that significantly governs the cell performance and the occurrence of Li plating. We demonstrate, based on a comprehensive mesoscale analysis, that the performance and degradation can be significantly modulated via systematic design improvements at the hierarchy of length scales. It is found that the improvement in kinetic and transport characteristics achievable at disparate scales can dramatically affect Li plating propensity.
The saturation stage of a multipactor discharge is considered of interest, since it can guide towards a criterion to assess the multipactor onset. The electron cloud under multipactor regime within a parallel-plate waveguide is modeled by a thin continuous distribution of charge and the equations of motion are calculated taking into account the space charge effects. The saturation is identified by the interaction of the electron cloud with its image charge. The stability of the electron population growth is analyzed and two mechanisms of saturation to explain the steady-state multipactor for voltages near above the threshold onset are identified. The impact energy in the collision against the metal plates decreases during the electron population growth due to the attraction of the electron sheet on the image through the initial plate. When this growth remains stable till the impact energy reaches the first cross-over point, the electron surface density tends to a constant value. When the stability is broken before reaching the first cross-over point the surface charge density oscillates chaotically bounded within a certain range. In this case, an expression to calculate the maximum electron surface charge density is found whose predictions agree with the simulations when the voltage is not too high.