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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Experimental study of the maximum resolution and packing density achievable in sintered and non-sintered binder-jet 3D printed steel microchannels

Developing high resolution 3D printed metallic microchannels is a challenge especially when there is an essential need for high packing density of the primary material. While high packing density could be achieved by heating the structure to the sintering temperature, some heat sensitive applications require other strategies to improve the packing density of primary materials. In this study the goal is to develop high green or pack densities microchannels on the scale of 2-300 microns which have a robust mechanical structure. Binder-jet 3D printing is an additive manufacturing process in which droplets of binder are deposited via inkjet into a bed of powder. By repeatedly spreading thin layers of powder and depositing binder into the appropriate 2D profiles, complex 3D objects can be created one layer at time. Microchannels with features on the order of 500 microns were fabricated via binder jetting of steel powder and then sintered and/or infiltrated with a secondary material. The average particle size of the steel powder was varied along with the droplet volume of the inkjet-deposited binder. The resolution of the process, packing density of the primary material, the subsequent features sizes of the microchannels, and the overall microchannel quality were characterized as a function of particle size distribution, droplet sizes and heat treatment temperatures.

Elliott, Amy M↗
DOE OSTI2024

Test and Validate Distributed Coaxial Cable Sensors for in situ Condition Monitoring of Coal-Fired Boiler Tubes

This project aims to test, validate, and advance the technology readiness level (from TRL5 to TRL7) of a novel low-cost distributed stainless-steel/ceramic coaxial cable sensing (SSC-CCS) technology for in situ monitoring of the boiler tube temperature in existing coal-fired power plants. The novel SSC-CCS sensing technology and associated condition-based monitoring (CBM) software to be demonstrated in this project will lead to an improved understanding of the boiler tube failure mechanisms and a prognostic system to improve the overall performance, reliability, and flexibility of the nation’s coal-fired power plant fleet. A boiler tube monitoring system with distributed coaxial cable temperature sensors and a sensor acquisition system was constructed. The high-temperature coaxial cable sensor with a length of 1.3m was made by using a quartz tube (1mm inner diameter (ID) and 6mm outer diameter (OD)) to concentrically separate a 304 stainless-steel (SS) rod (1mm OD) and SS tube (7.94mm OD and 6.16mm ID). The sensor acquisition system includes a vector network analyzer (VNA), a radio frequency (RF) power amplifier, multiple switches and a USB hub. The distributed stainless-steel quartz coaxial cable sensor (SSQ-CCS) had a linear response to temperature with a resolution uncertainty of σ = 0.77℃. To withstand the harsh conditions of 3,300 steam pressures and 800℃ high temperatures, the sensor was shielded by a protective tube made of the same material as the boiler tube. The protection tube had an OD of 1.5 inches and a thickness of 0.25 inches. In the laboratory tests, the sensor showed good sensitivity and fast response. The drift was bounded between +0.33% and -0.67% during a test at 600℃ for 350 hours, indicating good stability of the sensor. A field test was conducted where four sensors were welded on four superheat tubes (SH-Ts) at a coal-fired power station over 400 days. Conventional thermocouples were welded to the superheater tubes alongside the coaxial cable sensors for the purpose of comparison. Two sensors were capable of distributed sensing, with three multiplexed sensing sections. The other two sensors were single section. During the 400-day test period, the power plant experienced startups and shutdowns. At the steady state operations, the temperature of the boiler tube is about 600℃ (1112°F). The sensors recorded the entire coal-firing processes (start-up, steady state, and shut-down) and the glitch event. A GSM modem and a Watchdog were added to the system to ensure reliable data recording. The GSM modem sent daily messages to plant managers and Clemson team to inform the status of the sensor system. If the system was not normally working, the Watchdog would reboot the system automatically. The new coaxial cable based distributed sensing technology has been proven to be successful in both laboratory and field tests. A comprehensive four-stage multi-physics computational framework has been developed to assist the design, optimization, installation, and operation of SSQ-CCS. With the consideration of various operation conditions, we predict the distributions of flue gas temperatures within coal-fired boilers, the temperature correlation between the boiler tube and SSQ-CCS, and the safety of SSQ-CCS. A conditional-based monitoring system is implemented as well. The computational framework developed in this work can guide the future operation of coal-fired plants and other power plants for the safety prediction of boiler operations.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2019

Pair distribution function analysis of neutron-irradiated silicon carbide

We have employed x-ray total scattering to investigate the structure of polycrystalline 3C-silicon carbide following neutron irradiation. Here, the structure as a function of irradiation temperature and dose was quantified by analyzing pair distribution functions. Although the SiC matrix retains its crystal structure after irradiation, a significant increase in the diffuse scattering component is observable indicating that neutron irradiation leads to changes in both the short- and medium-range order. These changes include both an irradiation dose- and temperature-dependent increase in the vacancy concentration leading to an increase in the Si and C atomic displacement parameters. A dose-dependent decrease in the size of defect free material is also quantified from the structural refinements due to an increase in the number of defects and defect clusters. Evidence of additional correlations in the short-range order (up to ~4 Å) from differential pair distribution function analysis indicate that combinations of atomistic defects including anti-site defects, vacancies and defect clusters are present after these irradiation conditions. Such structural information will be valuable for direct comparison of experimental and simulated atomic structures of irradiated silicon carbide.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Methodology for Estimating Thermal and Neutron Embrittlement of Austenitic Stainless Steel Welds During Service in Light Water Reactors

The effect of thermal aging on the degradation of fracture toughness and Charpy-impact properties of austenitic stainless steel (SS) welds has been characterized at reactor temperatures. The solidification behavior and the distribution and morphology of the ferrite phase in SS welds are described. Thermal aging of the welds results in moderate decreases in Charpy-impact strength and fracture toughness. The upper-shelf Charpy-impact energy of aged welds decreases by 50–80 J/cm2. The decrease in fracture toughness J-R curve, or JIc is relatively small. Thermal aging has minimal effect on the tensile strength. The fracture properties of SS welds are insensitive to filler metal; the welding process has a significant effect. The large variability in the data makes it difficult to establish the effect of the welding process on fracture properties of SS welds. Consequently, the approach used for evaluating thermal and neutron embrittlement of austenitic SS welds relies on establishing a lower-bound fracture toughness J-R curve for unaged and aged, and non-irradiated and irradiated, SS welds. The existing fracture toughness J-R curve data for SS welds have been reviewed and evaluated to define lower-bound J-R curve for submerged arc (SA)/shielded metal arc (SMA)/manual metal arc (MMA) welds and gas tungsten arc (GTA)/tungsten inert gas (TIG) welds in the unaged and aged conditions. At reactor temperatures, the fracture toughness of GTA/TIG welds is a factor of about 2.3 higher than that of SA/SMA/MMA welds. Thermal aging decreases the fracture toughness by about 20%. The potential combined effects of thermal and neutron embrittlement of austenitic SS welds are also described. Lower-bound curves are presented that define the change in coefficient C and exponent n of the power-law J-R curve and the JIc value for SS welds as a function of neutron dose. The potential effects of reactor coolant environment on the fracture toughness of austenitic SS welds are also discussed.

Chopra, O. K.↗
DOE OSTI2019

Impact of non-Maxwellian electron velocity distribution functions on inferred plasma parameters in collective Thomson scattering

Optical collective Thomson scattering provides precise density and temperature measurements in numerous plasma-physics experiments. The accuracy of such measurements depends on the core assumption that the underlying electron distribution functions in under-dense laser-produced plasmas are Maxwellian. A statistically based, quantitative analysis of the errors in the measured electron density and temperature is presented when synthetic data calculated using a non-Maxwellian electron distribution function is fit assuming a Maxwellian electron distribution. Such analysis can lead to errors of up to 50% in temperature and 30% in density, in the specific case of super-Gaussian distributions characteristic of inverse bremsstrahlung heating. Furthermore including the proper family of non-Maxwellian electron distribution functions, as a fitting parameter, in Thomson-scattering analysis removes the model-dependent errors in the inferred parameters at a minimal cost to the statistical uncertainty.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

A Massive Shell of Supernova-formed Dust in SNR G54.1+0.3

While theoretical models of dust condensation predict that most refractory elements produced in core-collapse supernovae (SNe) efficiently condense into dust, a large quantity of dust has so far only been observed in SN 1987A. We present an analysis of observations from the Spitzer Space Telescope , Herschel Space Observatory , Stratospheric Observatory for Infrared Astronomy, and AKARI of the infrared shell surrounding the pulsar wind nebula in the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at 21 μ m to a magnesium silicate grain species that has been invoked in modeling the ejecta-condensed dust in Cas A, which exhibits the same spectral signature. If this species is responsible for producing the observed spectral feature and accounts for a significant fraction of the observed infrared continuum, we find that it would be the dominant constituent of the dust in G54.1+0.3, with possible secondary contributions from other compositions, such as carbon, silicate, or alumina grains. The total mass of SN-formed dust required by this model is at least 0.3 M {sub ⊙}. We discuss how these results may be affected by varying dust grain properties and self-consistent grain heating models. The spatial distribution of the dust mass and temperature in G54.1+0.3 confirms the scenario in which the SN-formed dust has not yet been processed by the SN reverse shock and is being heated by stars belonging to a cluster in which the SN progenitor exploded. The dust mass and composition suggest a progenitor mass of 16–27 M {sub ⊙} and imply a high dust condensation efficiency, similar to that found for Cas A and SN 1987A. The study provides another example of significant dust formation in a Type IIP SN explosion and sheds light on the properties of pristine SN-condensed dust.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

A Nonlinear Optimal Control Problem Arising from a Sterilization Process for Packaged Foods

In this paper we study an optimization problem arising from a sterilization process for packaged foods by using a microwave heating method. The goal of the optimal control is to find the optimal frequency function such that the temperature profile at the final stage has a relative uniform distribution in the food product. The underlying state variables are electric, magnetic fields and temperature which satisfy the coupled nonlinear Maxwell’s system and a nonlinear heat equation. The control variable for the system is chosen to be the electric frequency function. We show that there exists an optimal frequency which minimizes the cost functional. Moreover, an optimality condition is also derived.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Barrier inhomogeneities and electronic transport of Pt contacts to relatively highly doped n-type 4H-SiC

The barrier characteristics of Pt contacts to relatively highly doped (∼1 × 10{sup 18 }cm{sup −3}) 4H-SiC were investigated using current-voltage (I-V) and capacitance-voltage (C-V) measurements in the temperature range of 160–573 K. The barrier height and ideally factor estimated from the I-V characteristics based on the thermionic emission model are abnormally temperature-dependent, which can be explained by assuming the presence of a double Gaussian distribution (GD) of inhomogeneous barrier heights. However, in the low temperature region (160–323 K), the obtained mean barrier height according to GD is lower than the actual mean value from C-V measurement. The values of barrier height determined from the thermionic field emission model are well consistent with those from the C-V measurements, which suggest that the current transport process could be modified by electron tunneling at low temperatures.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Three-dimensional simulation of microwave-induced helium plasma under atmospheric pressure

A three-dimensional model is presented to investigate helium plasma generated by microwave under atmospheric pressure in this paper, which includes the physical processes of electromagnetic wave propagation, electron and heavy species transport, gas flow, and heat transfer. The model is based on the fluid approximation calculation and local thermodynamic equilibrium assumption. The simulation results demonstrate that the maxima of the electron density and gas temperature are 4.79 × 10{sup 17 }m{sup −3} and 1667 K, respectively, for the operating conditions with microwave power of 500 W, gas flow rate of 20 l/min, and initial gas temperature of 500 K. The electromagnetic field distribution in the plasma source is obtained by solving Helmholtz equation. Electric field strength of 2.97 × 10{sup 4 }V/m is obtained. There is a broad variation on microwave power, gas flow rate, and initial gas temperature to obtain deeper information about the changes of the electron density and gas temperature.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

The snake geothermal drilling project. Innovative approaches to geothermal exploration

The goal of our project was to test innovative technologies using existing and new data, and to ground-truth these technologies using slim-hole core technology. The slim-hole core allowed us to understand subsurface stratigraphy and alteration in detail, and to correlate lithologies observed in core with surface based geophysical studies. Compiled data included geologic maps, volcanic vent distribution, structural maps, existing well logs and temperature gradient logs, groundwater temperatures, and geophysical surveys (resistivity, magnetics, gravity). New data included high-resolution gravity and magnetic surveys, high-resolution seismic surveys, three slimhole test wells, borehole wireline logs, lithology logs, water chemistry, alteration mineralogy, fracture distribution, and new thermal gradient measurements.

15 GEOTHERMAL ENERGY↗
DOE OSTI2014

A Total Cost of Ownership Model for Low Temperature PEM Fuel Cells in Combined Heat and Power and Backup Power Applications

A total cost of ownership model is described for low temperature proton exchange membrane stationary fuel cell systems for combined heat and power (CHP) applications from 1-250kW and backup power applications from 1-50kW. System designs and functional specifications for these two applications were developed across the range of system power levels. Bottom-up cost estimates were made for balance of plant costs, and detailed direct cost estimates for key fuel cell stack components were derived using design-for-manufacturing-and-assembly techniques. The development of high throughput, automated processes achieving high yield are projected to reduce the cost for fuel cell stacks to the $300/kW level at an annual production volume of 100 MW. Several promising combinations of building types and geographical location in the U.S. were identified for installation of fuel cell CHP systems based on the LBNL modelling tool DER CAM. Life-cycle modelling and externality assessment were done for hotels and hospitals. Reduced electricity demand charges, heating credits and carbon credits can reduce the effective cost of electricity ($/kWhe) by 26-44percent in locations such as Minneapolis, where high carbon intensity electricity from the grid is displaces by a fuel cell system operating on reformate fuel. This project extends the scope of existing cost studies to include externalities and ancillary financial benefits and thus provides a more comprehensive picture of fuel cell system benefits, consistent with a policy and incentive environment that increasingly values these ancillary benefits. The project provides a critical, new modelling capacity and should aid a broad range of policy makers in assessing the integrated costs and benefits of fuel cell systems versus other distributed generation technologies.

08 HYDROGEN↗
DOE OSTI2017

Effect of Temperature and Fluid Flow on Dendrite Growth During Solidification of Al-3 Wt Pct Cu Alloy by the Two-Dimensional Cellular Automaton Method

A two-dimensional cellular automaton–finite volume model was developed to simulate dendrite growth of Al-3 wt pct Cu alloy during solidification to investigate the effect of temperature and fluid flow on dendrite morphology, solute concentration distribution, and dendrite growth velocity. Different calculation conditions that may influence the results of the simulation, including temperature and flow, were considered. The model was also employed to study the effect of different undercoolings, applied temperature fields, and forced flow velocities on solute segregation and dendrite growth. The initial temperature and fluid flow have a significant impact on the dendrite morphologies and solute profiles during solidification. The release of energy is operated with solidification and results in the increase of temperature. A larger undercooling leads to larger solute concentration near the solid/liquid interface and solute concentration gradient at the same time-step. Solute concentration in the solid region tends to increase with the increase of undercooling. Four vortexes appear under the condition when natural flow exists: the two on the right of the dendrite rotate clockwise, and those on the left of the dendrite rotate counterclockwise. With the increase of forced flow velocity, the rejected solute in the upstream region becomes easier to be washed away and enriched in the downstream region, resulting in acceleration of the growth of the dendrite in the upstream and inhibiting the downstream dendrite growth. The dendrite perpendicular to fluid flow shows a coarser morphology in the upstream region than that of the downstream. Almost no secondary dendrite appears during the calculation process.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Effect of alkali treatment on surface morphology of titanium

Alkali and heat treatments were first introduced by Kim et al. to prepare a bioactive surface on titanium. This method has been proven very effective and widely used in other studies to promote titanium osteointegration. This study aims to investigate further the effect of alkali treatment on surface morphology of high purity titanium. High purity titanium foils were immersed in NaOH aqueous solutions of 0.5 M, 5 M and 15 M at 60°C and 80 °C for 1, 3 and 7 days. The surface morphology was examined using Field Emission Scanning Electron Microscope (FESEM). The obtained phases were analysed using Fourier Transform Infrared Spectroscopy (FTIR) in the spectra range of 4000-600 cm{sup −1} at 4 cm{sup −1} resolution and 50 scans. At the same soaking temperature and soaking time, a thicker porous network was observed with increasing concentration of NaOH. At the same soaking temperature, a much porous structure was observed with increasing soaking time. At constant alkali concentration, more homogenously distributed porous surface structure was observed with increasing soaking temperature.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Distribution of Vacancies in a Hybrid M{sub (5–11/18)}X{sub (5–11/18)} Superstructure of a High-Temperature Ordered β-TiO Phase

A new structural model of the high-temperature ordered β-TiO phase of titanium monoxide with vacancies in metallic and nonmetallic sublattices has been proposed. The model suggests that the vacancies are simultaneously distributed over sites of two partially disordered superstructures: monoclinic M{sub 5}X{sub 5(mon)} (space group C2/m (A2/m)) and cubic M{sub 5}X{sub 5(cub)} (space group Pm3̄m). The hybrid superstructure belongs to space group P1m1 of the monoclinic system. The proposed notation M{sub (5–11/18)}X{sub (5–11/18)} of the hybrid superstructure takes into account an expansion of the vacancy sublattice due to the superposition of initial M{sub 5}X{sub 5{sup −}} type superstructures. It is shown that the arrangements of the superstructure reflections in the diffraction spectra of the M{sub (5–11/18)}X{sub (5–11/18)} and M{sub 5}X{sub 5(cub)} superstructures are identical.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Experimental study on thermal characteristics of positive leader discharges using Mach-Zehnder interferometry

Leader discharge is one of the main phases in long air gap breakdown, which is characterized by high temperature and high conductivity. It is of great importance to determine thermal characteristics of leader discharges. In this paper, a long-optical-path Mach-Zehnder interferometer was set up to measure the thermal parameters (thermal diameter, gas density, and gas temperature) of positive leader discharges in atmospheric air. IEC standard positive switching impulse voltages were applied to a near-one-meter point-plane air gap. Filamentary channels with high gas temperature and low density corresponding to leader discharges were observed as significant distortions in the interference fringe images. Typical diameters of the entire heated channel range from 1.5 mm to 3.5 mm with an average expansion velocity of 6.7 m/s. In contrast, typical diameters of the intensely heated region with a sharp gas density reduction range from 0.4 mm to 1.1 mm, about one third of the entire heated channel. The radial distribution of the gas density is calculated from the fringe displacements by performing an Abel inverse transform. The typical calculated gas density reduction in the center of a propagating leader channel is 80% to 90%, corresponding to a gas temperature of 1500 K to 3000 K based on the ideal gas law. Leaders tend to terminate if the central temperature is below 1500 K.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

AN ANOMALOUS COMPOSITION IN SLOW SOLAR WIND AS A SIGNATURE OF MAGNETIC RECONNECTION IN ITS SOURCE REGION

In this paper, we study a subset of slow solar winds characterized by an anomalous charge state composition and ion temperatures compared to average solar wind distributions, and thus referred to as an “Outlier” wind. We find that although this wind is slower and denser than normal slow wind, it is accelerated from the same source regions (active regions and quiet-Sun regions) as the latter and its occurrence rate depends on the solar cycle. The defining property of the Outlier wind is that its charge state composition is the same as that of normal slow wind, with the only exception being a very large decrease in the abundance of fully charged species (He{sup 2+}, C{sup 6+}, N{sup 7+}, O{sup 8+}, Mg{sup 12+}), resulting in a significant depletion of the He and C element abundances. Based on these observations, we suggest three possible scenarios for the origin of this wind: (1) local magnetic waves preferentially accelerating non-fully stripped ions over fully stripped ions from a loop opened by reconnection; (2) depleted fully stripped ions already contained in the corona magnetic loops before they are opened up by reconnection; or (3) fully stripped ions depleted by Coulomb collision after magnetic reconnection in the solar corona. If any one of these three scenarios is confirmed, the Outlier wind represents a direct signature of slow wind release through magnetic reconnection.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Development of a He{sup 3}−He{sup 4} sub Kelvin active magnetic regenerative refrigerator (AMRR) with no moving parts

Current state of the art particle and photon detectors such as Transition Edge Sensors (TES) and Microwave Kinetic Inductance Detectors (MKID) use large arrays of sensors or detectors for space science missions. As the size of these space science detectors increases, future astrophysics missions will require sub-Kelvin cooling over larger areas. This leads to not only increased cooling power requirements, but also a requirement for distributed sub-Kelvin cooling. We propose an active Magnetic Regenerative Refrigerator (AMRR) that uses a Superfluid Magnetic Pump (SMP) to circulate liquid He{sup 3}−He{sup 4} through a magnetic regenerator to provide the necessary cooling at sub-Kelvin temperatures. Such system will be capable of distributing the cooling load to a relatively large array of objects. One advantage of using a fluid for heat transfer in such systems is to isolate components such as the superconducting magnets from detectors that are sensitive to magnetic fields. Another advantage of the proposed tandem AMRR is that it does not need Gas Gap Heat Switches (GGHS) to transfer heat during various stages of the magnetic cooling. Our proposed system consists of four superconducting magnets, one superleak, and three heat exchangers. It will operate continuously with no moving parts and it will be capable of providing the necessary cooling at sub-Kelvin temperatures for future space science applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Proton diffusion and hydrogen/deuterium exchange in amorphous solid water at temperatures from 114 to 134 K

The reaction coefficient for hydrogen/deuterium (H/D) exchange and the diffusion of hydrated excess protons within amorphous solid water (ASW) are characterized as a function of temperature. For these experiments, water films are deposited on a Pt(111) substrate at 108 K, and reactions with pre-adsorbed hydrogen atoms produce hydrated protons. Upon heating, protons diffuse within the water, and H/D exchange occurs when they encounter D2O probe molecules deposited in the films. The time-dependent concentration of D2O is monitored with infrared spectroscopy, and it indicates the protons diffusion from the substrate and establish an equilibrium distribution prior to significant H/D exchange for temperatures 114 K ≤T≤ 134 K. By controlling the distance between the D2O molecules and the substrate, we probe the distribution of protons within the film. It decays as x−2 for the examined range of x (12–52 nm) due to the electric field that develops between the diffusing protons and their image charges in the metal substrate. This agrees with the theoretical distance scaling for the equilibrated proton concentration in a dielectric near a metal boundary. From the proton concentration and the measured D2O decay rate, a lower bound for the proton diffusion coefficient ranging from 10−20 m2/s at 114 K to 10−18 m2/s at 134 K is estimated. The diffusion coefficient has an activation energy of 0.40 eV, which is comparable to energies reported for molecular translations and rotations of H2O, suggesting they may play a critical role in the proton diffusion mechanism within ASW.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

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