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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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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Full Facility Shock Frame Simulations of the Electric Arc Shock Tube

Radiative heating computations are performed for high speed lunar return experiments conducted in the Electric Arc Shock Tube (EAST) facility at NASA Ames Research Center. The nonequilibrium radiative transport equations are solved via NASA's in-house radiation code NEQAIR using flow field input from US3D flow solver. The post-shock flow properties for the 10 km/s Earth entry conditions are computed using the stagnation line of a blunt-body and a full facility CFD (Computational Fluid Dynamics) simulation of the EAST shock tube. The shocked gas in the blunt-body flow achieves a thermochemical equilibrium away from the shock front whereas EAST flow exhibits a nonequilibrium behavior due to strong viscous dissipation of the shock by boundary layer. The full-tube flow calculations capture the influence of the boundary layer on the shocked gas state and provide a realistic fluid dynamic input for the radiative predictions. The integrated radiance behind the shock is calculated in NEQAIR for wavelength regimes from Vacuum-UltraViolet (VUV) to InfraRed (IR), which are pertinent to the emission characteristics of high enthalpy shock waves in air. These radiance profiles are validated against corresponding EAST shots. The full-tube simulations successfully predict a sharp radiance peak at the shock front which gets smeared in the test data due to the spatial resolution in the measurements. The full facility based radiance behind the shock shows a slightly better match with the test data in the VUV and Red spectral regions, as compared to that from a blunt-body based predictions. The UV radiance is very similar for both geometries and under-predicts the test behavior. The IR test data matches better with the blunt-body based predictions where the full-tube simulations show a significant over-prediction.

Radiation↗
DOE OSTI2012

Condensation in horizontal heat exchanger tubes

Many innovative reactor concepts for Generation III nuclear power plants use passive safety equipment for residual heat removal. These systems use two phase natural circulation. Heat transfer to the coolant results in a density difference providing the driving head for the required mass flow. By balancing the pressure drop the system finds its operational mode. Therefore the systems depend on a strong link between heat transfer and pressure drop determining the mass flow through the system. In order to be able to analyze these kind of systems with the help of state of the art computer codes the implemented numerical models for heat transfer, pressure drop or two phase flow structure must be able to predict the system performance in a wide parameter range. Goal of the program is to optimize the numerical models and therefore the performance of computer codes analyzing passive systems. Within the project the heat transfer capacity of a heat exchanger tube will be investigated. Therefore the tube will be equipped with detectors, both temperature and pressure, in several directions perpendicular to the tube axis to be able to resolve the angular heat transfer. In parallel the flow structure of a two phase flow inside and along the tube will be detected with the help of x-ray tomography. The water cooling outside of the tube will be realized by forced convection. It will be possible to combine the flow structure measurement with an angular resolved heat transfer for a wide parameter range. The test rig is set up at the TOPLFOW facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), so that it will be possible to vary the pressure between 5 and 70 bar. The steam mass content will be varied between 0 and 100 percent. The results will be compared to the large scaled Emergency Condenser Tests performed at the INKA test facility in Karlstein (Germany). The paper will explain the test setup and the status of the project will be presented. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2017

An expert-systems approach to automatically determining flaw depth within Candu pressure tubes - 221

Delayed Hydride Cracking (DHC) is a crack growth mechanism that occurs in zirconium alloys, including the pressure tubes of CANDU reactors. DHC is caused by hydrogen in solution in zirconium components being diffused to any flaws present, resulting in an increased concentration of hydrogen within these flaws. An increased hydrogen concentration can lead to brittleness, followed by cracking, in high-stress regions of a pressure tube. Regular in-service ultrasonic inspection of CANDU pressure tubes aims to locate and classify any flaws that pose a potential for DHC initiation. A common approach to inspection is the use of a bespoke tool containing multiple ultrasonic transducers to ensure that each point on the pressure tube is inspected from a minimum of three angles during a scan. All flaws from within the inspected pressure tubes must be characterized prior to restarting the reactor, thus the time-consuming analysis process lies on the critical outage path. This process is manually intensive and often requires a significant amount of expert knowledge. A modular system to automatically process outage data to provide decision support to analysts has been developed. This system saves time on the critical outage path while providing repeatable and explicable measurements. Part of the analysis process requires the depth of all flaws to be measured, which is often the most time consuming stage of the analysis process. This paper describes an approach that utilizes captured analysts knowledge to perform automatic flaw depth estimation. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2024

Mechanical degradation of duplex SiC-fiber reinforced SiC matrix composite tubes under a controlled high-temperature steam environment

This paper describes results from the mechanical evaluation of unirradiated SiC fiber–reinforced SiC matrix composite tubes under a controlled high-temperature steam environment. The experiments were aimed at identifying key material degradation behavior under environments relevant to loss-of-coolant accidents of light water reactors. Mechanical tests of the SiC composite tubes at 1000 °C under steam and inert environments were conducted using a unique test capability. Further, the material tested was a duplex tube with a thick monolithic SiC layer on the outer surface. The tubes were subjected to preloading at ~100 MPa in tension before exposure to high-temperature steam with up to 75% of the preload at a constant displacement. In the presence of matrix cracks, the steam exposure caused embrittlement of the SiC composite tubes and failure at a stress level below the pretest stress. The material degradation was explained by a fiber oxidation model, which can be applied to various SiC cladding concepts. The embrittlement could be a limiting factor for using SiC cladding subjected to loss-of-coolant accident conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Maximization of performance in multi-tube latent heat storage – Optimization of fins topology, effect of materials selection and flow arrangements

This paper addresses the need of multi-tube latent heat thermal storage (LHTES) systems with enhanced heat transfer performance. Uniquely, this work draws from topology optimization method for thermal energy storage to search for the optimal configuration of fins in multi-tube LHTES systems with different phase change materials (PCMs), flow arrangements and design constraints. The design freedom of topology optimization allows the discovery of innovative LHTES designs and elucidate the link between design and physical processes occurring during charging/discharging. Three key results of this study are: i) the optimized fin design is tightly connected to the type of storage duty cycle, which demonstrates the necessity to account for realistic operating conditions in the optimization process. ii) The fin material should be chosen in parallel with the layout of the fins and not sequentially as commonly done; this indicates that the optimization of LHTES systems is a co-design challenge. iii) Topology optimized multi-tube LHTES units surpass in performance fins optimized for a single-tube configuration in a multi-tube unit. Finally, this work demonstrates for the first time the manufacturability of topology-optimized LHTES units by using 3D printing.

25 ENERGY STORAGE↗
DOE OSTI2024

Effect of micro-fin tube geometry parameters on evaporator material savings

A Performance Evaluation Criteria (PEC) analysis is presented that explores the influence of the micro-fin tube geometry on the required material volume. The analysis was done using a local flow boiling model, which can quantify the effect of fin parameters and the tube diameter. The PEC was done while requiring that the compared surfaces satisfy the same heat duty and pressure drop. The following tube parameters and ranges were explored: tube diameter (3 mm ≤ D o ≤ 6 mm), fin base thickness (0.12 mm ≤ t bf ≤ 0.29 mm), helix angle (6° ≤ α ≤ 30°), fin apex angle (11° ≤ β ≤ 22°), total number of fins (43 ≤ n f ≤ 70), and the fin height (0.11 mm ≤ e ≤ 0.3 mm). The tube that provided the smallest material requirements within the examined parameter ranges had: D o = 3 mm, t bf = 0.12 mm, α = 6°, β = 11°, n f = 43, and e = 0.3 mm. In general, small D o and t bf and large n f and e provided the best performance and work to minimize the required material volume to provide a given heat duty and pressure drop. The helix and the fin-tip apex angles were found to have very little influence on the performance for the examined range of parameters and angles associated with the lowest production cost should be chosen.

Evaporation↗
DOE OSTI2013

Elastic response of water-filled fiber composite tubes under shock wave loading

We experimentally and numerically investigate the response of fluid-filled filament-wound composite tubes subjected to axial shock wave loading in water. Our study focuses on the fluid structure interaction occurring when the shock wave in the fluid propagates parallel to the axis of the tube, creating pressure waves in the fluid coupled to flexural waves in the shell. The in-house-developed computational scheme couples an Eulerian fluid solver with a Lagrangian shell solver, which includes a new and simple material model to capture the response of fiber composites in finite kinematics. In the experiments and simulations we examine tubes with fiber winding angles equal to 45 and 60 , and we measure the precursor and primary wave speeds, hoop and longitudinal strains, and pressure. The experimental and computational results are in agreement, showing the validity of the computational scheme in complex fluid structure interaction problems involving fiber composite materials subjected to shock waves. The analyses of the measured quantities show the strong coupling of axial and hoop deformations and the significant effect of fiber winding angle on the composite tube response, which differs substantially from that of a metal tube in the same configuration.

Perotti, Luigi E.↗
DOE OSTI2014

Superior Corrosion Resistance Properties of TiN-Based Coatings on Zircaloy Tubes in Supercritical Water

Thin films of TiN and Ti0.35Al0.65N nanocomposite were deposited on polished Zircaloy-4 tubes. After exposure to supercritical water for 48 h, the coated tubes are remarkably intact, while the bare uncoated tube shows severe oxidation and breakaway corrosion. X-ray diffraction patterns, secondary electron images, backscattered electron images, and energy dispersive X-ray spectroscopy data from the tube surfaces and cross-sections show that a protective oxide, formed on the film surface, effectively prevents further oxidation and corrosion to the Zircaloy-4 tubes. This result demonstrates the effectiveness of thin film ceramics as protective coatings under extreme environments.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Thermal diffusivity and thermal conductivity of SiC composite tubes: the effects of microstructure and irradiation

Cladding thermal conductivity is an important physical property in assessing the performance of silicon carbide (SiC)-cladded fuels for nuclear reactors. However, there is a significant lack of reliable data, particularly for irradiated materials, because the geometry complicates the measurement. This study investigates the thermal diffusivity of coupons with a curvature, machined from SiC fiber–reinforced SiC matrix composite tubes, with and without neutron irradiation under light water reactor–relevant temperature and dose conditions. The tested materials included full composite and duplex SiC composite tubes. The measurements were conducted using a modern flash diffusivity apparatus. The analyzed area on the specimen during diffusivity testing was reduced for improved measurement accuracy due to sample curvature. Post-irradiation measurements showed that the effects of neutron irradiation on thermal conductivity (e.g. thermal defect resistivity) are different between SiC composite plates versus tubes. The difference was explained by higher matrix density of the tube than the plate. This study provides reliable thermal properties of prototypic SiC composite tubes useful for fuel performance modeling of SiC-based cladding.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Formation and characterization of hydride rim structures in Zircaloy-4 nuclear fuel cladding tubes

Zirconium alloy tubes used as nuclear fuel cladding are subject to oxidation and subsequent hydrogen pickup during their long service in commercial light water reactors. The hydrogen picked up in the cladding can precipitate as a brittle hydride rim feature on the cladding outer surface. Here, to better understand the effect of hydride rims on the fracture behavior of stress-relieved zirconium alloy cladding tubes, a procedure to produce these rim-like structures has been developed and is described herein. Extensive characterization of the ‘as hydrided’ tubes is performed. The hydrogen charging apparatus consists of a tube furnace with a quartz chamber that is connected to a vacuum pump as well as a bottle of pure hydrogen gas. The charging station uses a static charge of hydrogen as opposed to a flowing gas. The chief advantage of this approach is the ability to monitor the pressure drop in the hydriding chamber and correlate this pressure drop to a known rate of hydrogen pickup in the cladding tube. It was found that the hydrogen partial pressure, metal temperature, and surface treatment all clearly played a role in whether a hydride rim was formed. Extensive characterization of the hydride rims shows they consist of needle like platelets of δ phase hydrides (ZrH1.66) oriented in the circumferential direction with a radial spacing of several microns in a sandwich-like structure.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2025

Entanglement entropy of a color flux tube in (1+1)D Yang–Mills theory

In recent work Amorosso et al. (2024), we computed a novel flux tube entanglement entropy (FTE) of the color flux tube stretched between a heavy quark-antiquark pair on a Euclidean lattice in (2+1)D Yang–Mills theory. Our numerical results suggested that FTE can be partitioned into an internal color entanglement entropy and a vibrational entropy corresponding to the transverse excitations of a QCD string, with the latter described by a thin string model. Since the color flux tube does not have transverse excitations in (1+1)D Yang–Mills theory, we use this simpler framework to perform an exact analytical computation of the contribution of the internal color degrees of freedom to FTE. For the multipartite partitioning of the color flux tube, we find the remarkable result that FTE depends only on the dimension of the color group representation and the number of times the flux tube crosses the boundary between the traced and untraced spatial regions but not on the string length. Our proof is independent of whether the replica and region boundaries on the lattice are placed on vertices or in plaquette centers.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2018

Chemical vapor deposition of Mo tubes for fuel cladding applications

In this study, chemical vapor deposition (CVD) techniques have been evaluated for fabrication of free-standing 0.25 mm thick molybdenum tubes with the end goal of nuclear fuel cladding applications. In order to produce tubes with the wall thickness and microstructures desirable for this application, long deposition durations on the order of 50 h with slow deposition rates were employed. A standard CVD method, involving molybdenum pentachloride reduction by hydrogen, as well as a fluidized-bed CVD (FBCVD) method was applied towards these objectives. Characterization of the tubes produced in this manner revealed regions of material with fine grain microstructure and wall thickness suitable for fuel cladding applications, but lacking necessary uniformity across the length of the tubes. Finally, a path forward for the production of freestanding molybdenum tubes that possess the desired properties across their entire length has been identified and can be accomplished by future optimization of the deposition system.

(Fluidized-bed) chemical vapor deposition↗
DOE OSTI2021

Involvement of multiple scavenger receptors in advanced glycation end product-induced vessel tube formation in endothelial cells

Highlights: • Multiple scavenger receptors contribute to AGE-induced angiogenesis. • RAGE contributes to AGE-induced angiogenesis by upregulation of scavenger receptors. • AGE activates mTOR signaling. Toxic advanced glycation end products (toxic AGEs) derived from glycolaldehyde (AGE3) have been implicated in the development of diabetic vascular complications such as retinopathy characterised by excessive angiogenesis. Different receptor types, such as receptor for AGEs (RAGE), Toll like receptor-4 and scavenger receptors, are expressed in endothelial cells and contribute to AGE-elicited alteration of cell function. In the present study, we examined the involvement of AGE-related receptors on AGE-induced angiogenesis in endothelial cells. The effects of pharmacological inhibitors or receptor neutralizing antibodies on AGE3-induced tube formation were investigated using the in vitro Matrigel tube formation assay in b.End5 cells (mouse endothelial cells). AGE3-induced signalling pathways and receptor expression changes were analysed by Western blot analysis and flow cytometry, respectively. Both FPS-ZM1, a RAGE inhibitor, and fucoidan, a ligand for scavenger receptors, suppressed AGE3-induced tube formation. Cocktails of neutralizing antibodies against the scavenger receptors CD36, CD163 and LOX-1 prevented AGE3-induced tube formation. AGE3 activated mTOR signalling, resulting in facilitation of tube formation. Activation of the AGE-RAGE pathway also led to the upregulation of scavenger receptors. Taken together, our findings suggest that the scavenger receptors CD36, CD163 and LOX-1 in conjunction with the RAGE receptor work together to mediate toxic AGE-induced facilitation of angiogenesis.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Development of a novel miniature detonation-driven shock tube assembly that uses in situ generated oxyhydrogen mixture

A novel concept to generate miniature shockwaves in a safe, repeatable, and controllable manner in laboratory confinements using an in situ oxyhydrogen generator has been proposed and demonstrated. This method proves to be more advantageous than existing methods because there is flexibility to vary strength of the shockwave, there is no need for storage of high pressure gases, and there is minimal waste disposal. The required amount of oxyhydrogen mixture is generated using alkaline electrolysis that produces hydrogen and oxygen gases in stoichiometric quantity. The rate of oxyhydrogen mixture production for the newly designed oxyhydrogen generator is found to be around 8 ml/s experimentally. The oxyhydrogen generator is connected to the driver section of a specially designed 10 mm square miniature shock tube assembly. A numerical code that uses CANTERA software package is used to predict the properties of the driver gas in the miniature shock tube. This prediction along with the 1-D shock tube theory is used to calculate the properties of the generated shockwave and matches reasonably well with the experimentally obtained values for oxyhydrogen mixture fill pressures less than 2.5 bars. The miniature shock tube employs a modified tri-clover clamp assembly to facilitate quick changing of diaphragm and replaces the more cumbersome nut and bolt system of fastening components. The versatile nature of oxyhydrogen detonation-driven miniature shock tube opens up new horizons for shockwave-assisted interdisciplinary applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Computational study of instability and fill tube mitigation strategies for double shell implosions

Double shell capsules are an attractive alternative scheme for achieving robust alpha-heating at the National Ignition Facility due to their low convergence ratio and low predicted temperature for achieving volume ignition. Nevertheless, simulations suggest that double shell targets are more susceptible to the fill tube, used to fill the inner shell with liquid DT, than typical single-shell ignition capsule designs, due to the higher density gradient between the shell and the fill tube hole, a lower outer shell velocity, which prevents the implosion from catching up to the initial fill tube jet, and the absence of a rebounding shock through the foam to slow this jet. Double shells are also highly susceptible to the Rayleigh-Taylor instability at both interfaces with the high density inner shell. Combined, these effects are predicted by radiation-hydrodynamics simulations to reduce fuel confinement and temperature, resulting in reduced performance by a factor of ≈20–45, depending on design details, compared to idealized one-dimensional (1D) simulations. We discuss herein a mitigation strategy for both the interfacial instabilities and the fill tube that is predicted by simulations to decrease the yield degradation to a factor of ≈4. The mitigation strategy involves a modification of the capsule geometry as well as the use of a multishock pulse shape. The multishock pulse is required for the fill tube mitigation strategy and has the added benefit of stabilizing perturbations at the foam/pusher interface without decreasing 1D yield. In order to experimentally verify these predictions, we discuss the potential use of a hydrogrowth radiography platform that could be applied to test the proposed mitigation strategies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Mixing in ICF implosions on the National Ignition Facility caused by the fill-tube

The micrometer-scale tube that fills capsules with thermonuclear fuel in inertial confinement fusion experiments at the National Ignition Facility is also one of the implosion's main degradation sources. It seeds a perturbation that injects the ablator material into the center, radiating away some of the hot-spot energy. This paper discusses how the perturbation arises in experiments using high-density carbon ablators and how the ablator mix interacts once it enters the hot-spot. Both modeling and experiments show an in-flight areal-density perturbation and localized x-ray emission at stagnation from the fill-tube. Simulations suggest that the fill-tube is degrading an otherwise 1D implosion by ~2×, but when other degradation sources are present, the yield reduction is closer to 20%. Characteristics of the fill-tube assembly, such as the through-hole size and the glue mass, alter the dynamics and magnitude of the degradation. Overall, these aspects point the way toward improvements in the design, some of which (smaller diameter fill-tube) have already shown improvements.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Fill tube dynamics in inertial confinement fusion implosions with high density carbon ablators

Plasma jets, such as γ-ray burst jets, Herbig–Haro jets, μ-quasar jets, and active galactic nuclei jets, are found throughout the universe [S. Mendoza et al., Rev. Mex. Astron. Astrofis. 41, 453 (2005)]. Plasma jets are also present in indirect drive inertial confinement fusion experiments originating from the capsule's fill tube and occasionally from divots and voids in the capsules, particles on the exterior of the capsule, or from the tent holding the capsule in the target. This paper looks at two different gas-filled capsule implosions containing a plasma jet resulting from a capsule fill tube and fill channel, both of which utilized high density carbon ablators. Two models were developed, a drag and a snowplow model, which use the time-dependent motion of the injected mass through the hotspot to estimate the mass injected into the hotspot from the fill tube and channel, arriving at an average injected mass of ~84.5 ± 25.5 ng for the first experiment and 91 ± 20 ng for the second experiment. Furthermore, unlike previous methods to estimate fill tube injected mass, these techniques do not assume that the mixed mass is in thermal equilibrium with the hotspot or that the x-ray emission is only coming from within the hotspot itself. This paper also discusses the features seen in these experiments which include limb brightening in the shell for undoped ablators and flattening in the ablator from shadowing by the fill tube.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

PROPAGATION AND DISPERSION OF SAUSAGE WAVE TRAINS IN MAGNETIC FLUX TUBES

A localized perturbation of a magnetic flux tube produces wave trains that disperse as they propagate along the tube, where the extent of dispersion depends on the physical properties of the magnetic structure, on the length of the initial excitation, and on its nature (e.g., transverse or axisymmetric). In Oliver et al. we considered a transverse initial perturbation, whereas the temporal evolution of an axisymmetric one is examined here. In both papers we use a method based on Fourier integrals to solve the initial value problem. We find that the propagating wave train undergoes stronger attenuation for longer axisymmetric (or shorter transverse) perturbations, while the internal to external density ratio has a smaller effect on the attenuation. Moreover, for parameter values typical of coronal loops axisymmetric (transverse) wave trains travel at a speed 0.75–1 (1.2) times the Alfvén speed of the magnetic tube. In both cases, the wave train passage at a fixed position of the magnetic tube gives rise to oscillations with periods of the order of seconds, with axisymmetric disturbances causing more oscillations than transverse ones. To test the detectability of propagating transverse or axisymmetric wave packets in magnetic tubes of the solar atmosphere (e.g., coronal loops, spicules, or prominence threads) a forward modeling of the perturbations must be carried out.

79 ASTRONOMY AND ASTROPHYSICS↗