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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Modeling Heat Pipe Startup And Noncondensable Gases In Sockeye

A one-dimensional gas mixture flow model was developed and implemented in the heat pipe code Sockeye to model the effects of non-condensable gases. Additionally a startup model based on the dusty gas model was implemented to model the transition from rarefied gas dynamics to continuum flow, which occurs during the frozen startup of high-temperature heat pipes. Multiple startup models and non-condensable gas models were tested against experimental data for sodium heat pipes, showing excellent agreement. Additionally, the newly developed gas mixture model for modeling non-condensable gas is further tested with a theoretical case study with arbitrary heating configurations. Finally, several recommendations and conclusions are made from the studies in this work to guide future heat pipe modeling efforts.

97 - MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Comprehensive insights into competitive oxidation/sulfidation reactions on binary ferritic alloys at high temperatures

Interpreting high-temperature corrosion induced by mixed-gas atmospheres is challenging due to the different contributions of oxidizing gases. In this work, a comprehensive study on the combined oxidation/sulfidation using label molecules is presented. Fe-Cr model alloys with 2 wt% and 9 wt% Cr were isothermally exposed using a volumetric mixture of 0.5%S 16 O 2 /27%H 2 18 O and 0.5%S 16 O 2 /7%H 2 18 O at 650 °C for 5 h and then characterized by secondary ion mass spectroscopy (SIMS). Additionally, the reactions were followed in-situ utilizing energy dispersive X-ray diffraction. The study showed that both S 16 O 2 and H 2 18 O contribute to the oxidation of the alloys but to different extents depending on the Cr-content.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Refractory-based thermal energy storage for industrial process heat: one-dimensional modeling, control, and optimization

The variable and weather-dependent output of wind and solar power plants present a substantial challenge for planning and operating electricity-systems, particularly in the absence of cost-effective and dispatchable energy storage technologies. This study investigates a high-temperature, electrically heated, refractory-based thermal energy storage (RTES) system that stores electrical energy as sensible heat in dense ceramic bricks over the 950–1800 °C range. The stored heat can be discharged as a controlled hot-gas stream for industrial heating, fuel substitution in high-temperature processes, or electricity generation. The main novelty is a comprehensive modelling, control, mapping, and optimization framework that integrates one-dimensional transient gas–solid heat transfer, fan-assisted discharge, bypass-flow regulation, reheating logic, fan-power evaluation, insulation-loss assessment, and genetic-algorithm-based design optimization. The model uses feedback from outlet temperature and delivered power to regulate discharge, while a two-stage genetic algorithm optimizes brick-channel geometry, gas-flow operation, and multilayer insulation thicknesses. Storage capacities below 50 MWh and discharge powers of 5–30 MW are analyzed to evaluate hold time, thermal delivery, fan-power penalty, heat loss, state-of-charge evolution, and indicative capital cost. Results demonstrate that optimized and well-insulated refractory-based thermal energy storage units can provide stable, efficient, and repeatable heat delivery over multiple discharge cycles. The generated performance and cost maps support modular refractory thermal energy storage as a practical option for large-scale integration of wind and solar generation and for high-temperature industrial process heat.

25 ENERGY STORAGE↗
DOE OSTI2022

Vapor-Phase Aggregation of Cerium Oxide Nanoparticles in a Rapidly Cooling Plasma

Local conditions, such as temperature and oxygen availability, have a pronounced effect on the formation and evolution of fallout following a nuclear explosion. While the behavior of nuclear-relevant materials such as uranium has begun to be explored under a wider range of environments, little is known about the behavior of plutonium. Here, using cerium as a surrogate, we track the vapor-phase aggregation of cerium oxide nanoparticles created in a plasma flow reactor under conditions of controlled temperature at two different oxygen fugacities. In situ optical emission spectroscopy is used to measure the variations in the spectral intensity of atomic and molecular species with temperature and oxygen content. We find that the relative rate of gas-phase oxidation of cerium is highly dependent on both temperature and local redox conditions within the flow reactor, to the extent that doubling the oxygen availability effectively doubles the amount of vapor-phase cerium monoxide at high temperatures (>2000 K). Condensed cerium oxide nanoparticles are also collected and analyzed ex situ via transmission electron microscopy and grazing-incidence small-angle X-ray scattering to determine their elemental composition, crystal structure, and size distribution. The size and morphology of the condensed nanoparticles are independent of local redox conditions, forming the same crystal type with the same size distribution regardless of oxygen availability. Postcondensation particle evolution, however, is found to be predominantly driven by temperature, with the average particle size increasing as particles cool and subsequently aggregate. These results expand our understanding of the chemical and physical behavior of refractory oxides that form during the early stages of fallout formation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power

Pumped thermal energy storage (PTES) systems are grid batteries that use heat pumps to create both hot and cold thermal energy stores when there is excess electricity and then use a power cycle to convert the thermal energy into electricity when there is demand for electricity. In normal operation, Joule–Brayton PTES discharges low-grade heat at temperatures useful for thermal energy consumers like district and industrial heating. Furthermore, PTES designs, like conventional combined heat and power (CHP) technology, can be modified to sacrifice some round-trip efficiency (RTE) to increase the temperature of heat rejection. Here, this paper uses design-point performance and cost models that provide a detailed understanding of the efficiency and cost tradeoffs of rejecting heat at various temperatures in ideal-gas Brayton PTES configurations. First, we keep the heat rejection in its nominal location in the PTES system: in the discharge cycle after the low-pressure exit of the recuperator before the cold-storage heat exchanger. Next, we move the heat rejection to the discharge turbine exit. We define design-point metrics that isolate both the cost and performance penalty associated with the hotter heat rejection and attribute it exclusively to the heat economic metrics. Finally, we estimate the performance of electric heater technology to generate heat at equivalent temperatures. We find that the levelized cost of heat (LCOH), including the cost of thermal energy storage (TES) buffering the PTES and heat off-taker, compares favorably versus electric technologies and is less than the cost of natural gas for low temperature scenarios and competitive with the cost of natural gas in some regions of the contiguous U.S. in high temperature scenarios.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2024

Sintering Mechanism of Pt/Al 2 O 3 in Complex Emission Gases Elucidated via In Situ Environmental STEM

Emission control catalysts are crucial for protecting human health by preventing the release of harmful gases and unburnt fuel into the atmosphere. These catalysts often face deactivation through sintering processes in high-temperature, chemically reactive environments containing multiple gas species. Here, we use in situ environmental scanning transmission electron microscopy to monitor the sintering behavior and transient morphologies of Pt/Al 2 O 3 in various relevant gas environments through controlled experiments. Our results reveal the particle migration and atomic ripening behavior of Pt/Al 2 O 3 at the atomic scale in the presence of water vapor and oxygen, which differs from behaviors observed in single gas environments. We identify an atomic ripening mechanism involving the dissociation and migration of Pt adatom chains from Pt nanoparticles, observed only in combinational gases. Finally, these findings provide valuable insights into catalyst degradation behavior in complex gas environments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Thermodynamic Modeling of Complex Solid Solutions in the Lu-H-N System via Graph Neural Network Accelerated Monte Carlo Simulations

Metal hydrides are important across diverse applications, such as hydrogen storage, batteries, gas sensors, nuclear reactions, and high-temperature superconductivity. Previous computational studies of metal hydrides under extreme pressures, e.g., 𝑂⁡(10 2 ) ⁢GPa, usually treat them as stoichiometric compounds without considering interstitial lattice disorder. As pressures become more moderate in the 𝑂⁡(10 0 ) ⁢GPa and below range, hydrogen disorder at interstitial lattice sites becomes prominent, e.g., in the N-doped Lu hydride that was recently claimed superconducting near 1 GPa. Further adding compositional complexity from alloying and/or multielement interstitial occupation makes elucidating pressure- and temperature-dependent observables intractable by first-principles calculations alone. We therefore propose a lattice graph neural-network surrogate modeling approach to predict configuration- and pressure-dependent equation-of-state properties. Their efficiency permits Monte Carlo simulations to calculate Gibbs energies and pressure-dependent phase diagrams, thereby revealing insights into the synthesis conditions required for achieving desired phase equilibria. We demonstrate this concept for the compositionally complex cubic Lu(H,N,Va) 3 system where three constituents (hydrogen, nitrogen and vacancy) have disordered multielement interstitial occupancies and insights into pressure-dependent phase equilibria are critically needed, e.g., N-doping levels can significantly lower dehydrogenation temperatures and provide a new strategy to optimize hydrogen-storage alloys. This work can improve the thermodynamic understanding of the Lu-H-N system and help rational synthesis of N-doped Lu hydrides, but more generally demonstrates an efficient approach to model pressure-dependent thermodynamics of multicomponent solid solutions.

Monte Carlo methods↗
DOE OSTI2020

Characterization of an RF-driven argon plasma at atmospheric pressure using broadband absorption and optical emission spectroscopy

Atmospheric pressure plasmas in argon are of particular interest due to the production of highly excited and reactive species enabling numerous plasma-aided applications. In this contribution, we report on absolute optical emission and absorption spectroscopy of a radio frequency (RF) driven capacitively coupled argon glow discharge operated in a parallel-plate configuration. This enabled the study of all key parameters including electron density and temperature, gas temperature, and absolute densities of atoms in highly electronically excited states. The space and time-averaged electron density and temperature were determined from the measurement of the absolute intensity of the electron-atom bremsstrahlung in the visible range. Considering the non-Maxwellian electron energy distribution function, an electron temperature (T e ) of 2.1 eV and an electron density (n e ) of 1.1 × 10 19 m –3 were obtained. The time-averaged and spatially resolved absolute densities of atoms in the metastable (1s 5 and 1s 3 ) and resonant (1s 4 and 1s 2 ) states of argon in pure Ar and Ar/He mixture were obtained by broadband absorption spectroscopy. The 1s 5 metastable atoms had the largest density near the sheath region with a maximum value of 8 × 10 17 m –3 , while all other 1s states had densities of at most 2 × 10 17 m –3 . Here, the dominant production and loss mechanisms of these atoms were discussed, in particular, the role of radiation trapping. We conclude with a comparison of the plasma properties of the argon RF glow discharges with the more common He equivalent and highlight their differences.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

High spatial resolution temperature profile measurements of solid-oxide fuel cells

Temperature gradients resulting from local electrochemical reactions, current distribution and geometry of gas flow channels in solid oxide fuel cells (SOFCs) create thermal stresses, localized thermophysical property gradients and uneven property evolution, contributing to SOFC degradation. This paper presents a new method to perform temperature measurements (up to 800°C) at high spatial resolutions to monitor the operation of SOFCs. Using femtosecond laser irradiation, distributed fiber sensors were hardened for high temperature environment applications. Distributed fiber sensors were embedded in interconnected plates using an additive manufacturing method to perform temperature measurements with 4-mm spatial resolution during the operation of a planar fuel cell. The measurement revealed the impact of various H 2 fuel concentrations and current loads have on temperature profiles of the SOFC tested. Temperature variation on the anode side was found to be less than 5°C, and 3°C on the cathode side. The measurements were compared to results from a multiphysics fuel cell performance model simulating similar conditions. These simulations predicted similar temperature gradients, indicating the experimental data obtained is reasonable. The model also predicts that the effect of the embedded sensor has on the local temperature will be minimal and that the gradient of temperature in the gas channels will be captured despite the separation between the sensor and the gas flow. Finally, the high spatial resolution data harnessed by these distributed fiber sensors provides experimental support for model-based design and optimization to improve the operational efficiency and longevity of solid oxide fuel cells and fuel cell assemblies.

25 ENERGY STORAGE↗
DOE OSTI2020

Negative Charge Confined Amine Carriers within the Nanowire Network for Stable and Efficient Membrane Carbon Capture

Membrane-based carbon dioxide (CO 2 ) capture has attracted great research interest owing to its potential for higher separation efficiency and lower energy consumption. However, it is still a challenging task to capture CO 2 with membrane from flue gas, especially under moderate-temperature and high-humidity conditions. Here, a stable CO 2 -selective membrane that can operate at temperatures up to 90 °C and under high humidity is reported. The positively charged amine carriers for CO 2 are confined within the negatively charged polymer modified carbon nanotube (CNT) network. In this structure, interconnected CNTs act as the framework for the selective layer and provide numerous nanochannels for gas transport. The negatively charged polymer ensures the carrier stability and further regulates the size of nanochannels in the CNT network. By virtue of carrier-facilitated transport, high CO 2 permeance (up to 3300 gas permeation units) and high CO 2 /N 2 selectivity (400) are achieved under simulated flue gas conditions. Moreover, theoretical calculations verify that the stable separation performance is due to the strong electrostatic interaction between the amine carriers and polymer matrix. The high performance and good stability indicate the great potential of this novel membrane structure for practical application in CO 2 capture.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Multigas Adsorption with Single-Site Cooperativity in a Metal-Organic Framework

Cooperative gas adsorption in metal-organic frameworks (MOFs) is a rare phenomenon that generally involves long-range communication between multiple binding sites. We demonstrate a MOF containing cobalt(II)-methyl sites that selectively and reversibly capture two carbon monoxide (CO) molecules per site, leading to record-high adsorption capacities at ambient temperatures and pressures. Gas adsorption and structural, spectroscopic, and computational analyses support a mechanism in which binding of one CO molecule triggers a spin transition, followed by binding of a second CO molecule and migratory insertion of the first CO molecule into the cobalt-methyl bond to form an acetyl. The greater binding affinity associated with the second CO results in sigmoidal adsorption isotherms, a hallmark of cooperativity and phase-change materials, despite the absence of long-range interactions within the framework.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Oxygen Reduction on Platinum-Nickel and Platinum-Cobalt Alloy Based Catalysts for High Temperature Proton Exchange Membrane Fuel Cells

Catalyst layers, with commercial PtNi/TKK (TECNiE52; platinum 46.5 wt%), PtCo/TKK (TEC36E52; platinum 45.8 wt%) catalysts, and an in-house catalyst PtNi-NC (platinum 38.4 wt%), synthesised using acoustic mixer and a tube furnace, are prepared using three different ionomers: 20 wt% Nafion®, 60 wt% polytetrafluoroethylene (PTFE), and an in-house 5 wt% ionomer (‘Ionomer X’). These inks are bar-coated onto carbon paper gas diffusion layers (GDLs), which are cut into 3 cm × 5 cm pieces. The coated layers are tested for oxygen reduction in a commercial gas diffusion electrode (GDE) test cell, FlexCell® (Gaskatel GmbH, Germany), using 85 wt% phosphoric acid at both room temperature and at 155°C. This study evaluates the polynorbornene (PNB)-based in-house ionomer performance as binder and in-house catalyst oxygen reduction reaction (ORR) activity in comparison to commercial products. The catalyst layers are characterised using X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Among the catalyst layers prepared with PTFE ionomer and tested at 155°C, the in-house catalyst demonstrates the highest ORR activity. Ionomer X proves to be a good candidate to be used as a per- and polyfluoroalkyl-free binder for high-temperature (HT) proton exchange membrane fuel cell (PEMFC) applications.

85 wt% phosphoric acid↗
DOE OSTI2021

Quantifying Temperature Dependence of Electronic Band Gaps and Optical Properties in SnO 2 and SnO via First-Principles Simulations

Tin metal oxides SnO x ( x = 1, 2) have gained interest as gas-sensing materials. For their applications as high-temperature sensors, however, a better understanding of their temperature dependence sensing responses is needed. Here, we comparatively quantify the temperature-dependent electronic band gaps and optical properties of SnO 2 and SnO using first-principles calculations. Without considering the temperature effect, SnO 2 and SnO are predicted to have direct and indirect band gaps of 2.18 and 1.66 eV, respectively, at the PBE + U -GGA level that we employed. The temperature effect on the electronic and optical properties is captured by taking account of the electron–phonon interaction. Band gap renormalization with temperature is calculated via the Allen–Heine–Cardona theory. For both oxides, we find a monotonic decrease in the electronic band gap such that renormalization at zero point (0 K) is ~–0.17 and ~–0.52 eV at 1000 K. These results are also analyzed by employing an analytical equation that helps characterize the band gap shift with temperature. In addition, the optical properties at finite temperatures are simulated using the frozen-phonon method that combines electron–phonon coupling with the momentum matrix. As temperature increases, the optical property spectra are smoothed because of the smearing effect, which diminishes optical constants at shorter wavelengths. Our results are of interest for high-temperature functional materials in applications of optical detection.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power

Pumped thermal energy storage (PTES) systems are grid batteries that use heat pumps to create both hot and cold thermal energy stores when there is excess electricity and then use a power cycle to convert the thermal energy into electricity when there is demand for electricity. In normal operation, Joule-Brayton PTES discharges low-grade heat at temperatures useful for thermal energy consumers like district and industrial heating. Furthermore, PTES designs, like conventional combined heat and power (CHP) technology, can be modified to sacrifice some round-trip efficiency RTE to increase the temperature of heat rejection. This paper uses design-point performance and cost models that provide a detailed understanding of the efficiency and cost trade-offs of rejecting heat at various temperatures in ideal-gas Brayton PTES configurations. First, we keep the heat rejection in its nominal location in the PTES system: in the discharge cycle after the low-pressure exit of the recuperator before the cold-storage heat exchanger. Next, we move the heat rejection to the discharge turbine exit. We define design-point metrics that isolate both the cost and performance penalty associated with the hotter heat rejection and attribute it exclusively to the heat economic metrics. Finally, we estimate the performance of electric heater technology to generate heat at equivalent temperatures. We find that the levelized cost of heat, including the cost of thermal energy storage (TES) buffering the PTES and heat off-taker, compares favorable versus electric technologies and is less than the cost of natural gas for low temperature scenarios and competitive with the cost of natural gas in some regions of the contiguous United States in high temperature scenarios.

CHP↗
DOE OSTI2025

Development of an In Situ Fission Gas Release Instrument for Fuel Sample Irradiations in the High Flux Isotope Reactor

Experimental measurement of gaseous fission product release with respect to temperature and burnup is a critical aspect of understanding nuclear fuel performance, validating predictive models, and qualifying new fuels. To measure this phenomenon in real-time, Oak Ridge National Laboratory has developed an instrument for measuring in situ fission gas release from small-scale fuel samples irradiated in the High Flux Isotope Reactor (HFIR). The instrument uses a continuous flow of Heover the fuel samples to sweep gaseous fission products from a sealed capsule in the HFIR Be reflector to an instrument station adjacent to the reactor. The instrument station houses two high-purity germanium (HPGe) detectors that measure decay gamma rays from fission products passing through a room temperature dwell chamber placed over the detector crystal. The sealed capsules in the reactor are designed to modulate fuel sample temperatures between 700 and 1,100°C by changing the Ar/He gas mixture surrounding the capsules during irradiation. N-type thermocouples are incorporated into the capsule housing to record real-time fuel temperatures. The capsules are heated primarily by prompt gamma rays emitted from the HFIR core with minimal heat contributions from fission in the fuel samples to minimize temperature gradients in the specimens for separate-effects characterization of the material. This paper describes modeling of time-dependent nuclear heating and fission product formation in fuel samples, thermal characteristics of the in-core capsules, and expected gaseous fission product gamma spectra at the HPGe instrument station.

Mulligan, Padhraic L [ORNL] (ORCID:000000025826540↗
DOE OSTI2026

The Use of Machine Learning Models for Predicting the Dielectric Strength of Gases

Technological advancements in high voltage systems have pushed sulfur hexafluoride (SF6) to its operational limits. Furthermore, this gas has other drawbacks including a high liquefaction temperature and a high global warming potential. Therefore, there has been an urgent need to find alternative gases with high dielectric strength (DS). In this work, density functional theory (DFT) is used to calculate molecular descriptors that are fed into an artificial neural network (ANN) and a random forest (RF). These machine learning (ML) models are then used to predict the DS for hundreds of molecules. A finite element model (FEM) is also used to calculate the electric field profile of multiple simple electrode geometries as the applied voltage to the system is increased. Results indicate that the random forest model has better generalization to unseen data than the neural network. The highest DS value predicted by the RF was 2.16 relative to the experimental DS of SF6. The results also demonstrate how choosing a gas with a higher DS and a geometry with minimal edges and corners can significantly increase the operating voltage of an electrical system. Due to its superior generalization, the RF represents the most promising path toward an accurate DS predictor once sufficient experimental data are available.

Mileski, Matthew [AFIT]↗
DOE OSTI2023

Toward local core outlet temperature monitoring in gas-cooled nuclear reactors using distributed fiber-optic temperature sensors

Gas-cooled nuclear reactors operate at temperatures up to 950 °C with significant spatial variations in power generation and coolant flow through hundreds of parallel flow channels, resulting in complex mixing at the core outlet. The high temperatures and complex mixing can damage downstream components, challenge reactor calorimetry for power determination, and result in significant conservatism in calculated peak fuel temperatures, which ultimately limits the total power output. Directly measuring each gas stream individually is unrealistic using single point thermocouples, requiring more robust sensing techniques. Fiber-optic sensors are resilient to high temperatures (up to 1,000 °C) and radiation damage. Moreover, distributed measurements can be made along the length of one fiber, making them potential candidates for monitoring local core outlet temperatures to improve core calorimetry and identify hot channels. Here, to the authors’ knowledge, this manuscript is the first to report spatially distributed fiber optic temperature measurements to quantify mixing at the outlet of a relevant orifice plate under prototypic temperature and flow regimes to assess the feasibility of using fiber-optic sensors for distributed measurements of coolant temperature in gas-cooled reactors. A single optical fiber captured dynamic changes in local temperatures, whereas the mixed outlet temperature exhibited a muted response and could not identify which channels were responsible for the change in the mixed outlet temperature. The discussion focuses on potential challenges for deploying distributed optical fibers in gas-cooled reactors, including the effects of vibrations, radiation-induced signal attenuation and drift, and routing of the fiber while minimizing flow obstructions.

42 ENGINEERING↗
DOE OSTI2021

Impact of humidity on gas transport in polybenzimidazole membranes

Polybenzimidazoles (PBIs) are promising materials for high temperature H 2 /CO 2 separation in applications such as steam reforming and pre-combustion carbon capture where significant amounts of water are often present. However, PBIs are hydrophilic, and the impact of humidity on PBI gas separation properties is relatively unexplored. Furthermore, opportunity exists to elucidate the interplay between plasticization, free volume, and gas transport in glassy polymer membranes such as PBIs. Here, this study investigates the effect of humidity on H 2 , O 2 , and CO 2 permeabilities at 35 °C in a commercial PBI and two sulfone-containing PBIs. Water uptake significantly reduces PBI gas permeabilities at low humidities due to competitive sorption and antiplasticization. At high humidities, plasticization increases the permeabilities of larger gases in more hydrophilic PBIs. Effective fractional free volumes evaluated from gas permeation data and previously reported water sorption and dilation data suggest water plasticizes PBIs by increasing accessible free volume via enhanced molecular dynamics rather than by creating new free volume cavities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗