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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
DOE OSTI2025

Bayesian inference of nuclear incompressibility from collective flow in mid-central Au+Au collisions at 400–1500 MeV/nucleon

The incompressibility K of symmetric nuclear matter (SNM) is determined through a Bayesian analysis of collective flow data from Au + Au collisions at beam energies $E = 400 -1500$ MeV/nucleon. This analysis utilizes a Gaussian process (GP) emulator applied to the isospin-dependent quantum molecular dynamics (IQMD) model for heavy-ion collisions, both with and without incorporating the momentum dependence of the single-nucleon potentials. Specifically, at the 68% confidence level, using rapidity and transverse velocity dependence of proton elliptic flow data with and without consideration of the momentum dependence, the inferred incompressibility values are $K=188.9^{+2.9}_{-4.5}$ MeV and $256.1^{+8.2}_{-8.7}$ MeV at $E = 400$ MeV/nucleon, respectively. When the transverse momentum dependence of proton-like directed flow data is included, the inferred incompressibility values become $K=222.3^{+9.0}_{-9.9}$ MeV and $K=285.5^{+6.7}_{-7.3}$ MeV, respectively. Furthermore, we found that the value of K derived from observables of proton elliptic flow increases with beam energy. Finally, this indicates that the equation of state (EoS) of nuclear matter hardens at higher densities and temperatures in reactions with higher beam energies.

Bayesian inference↗
DOE OSTI2023

Magnetohydrodynamics in free surface liquid metal flow relevant to plasma-facing components

Abstract While flowing Liquid Metal (LM) Plasma-Facing Components (PFCs) represent a potentially transformative technology to enable long-pulse operation with high-power exhaust for fusion reactors, Magnetohydrodynamic (MHD) drag in the conducting LM will reduce the flow speed. Experiments have been completed in the linear open-channel LMX-U device [Hvasta et al 2018 Nucl. Fusion 58 01602] for validation of MHD drag calculations with either insulating or conducting walls, with codes similar to those used to design flowing LM PFCs for a Fusion Nuclear Science Facility [Kessel et al 2019 Fusion Sci. Technol . 75 886]. We observe that the average channel flow speed decreased with the use of conducting walls and the strength of the applied transverse magnetic field. The MHD drag from the retarding Lorentz force resulted in an increase of the LM depth in the channel that ‘piled up’ near the inlet, but not the outlet. As reproduced by OpenFOAM and ANSYS CFX calculations, the magnitude and characteristics of the pileup in the flow direction increased with the applied traverse magnetic field by up to 120%, as compared to the case without an applied magnetic field, corresponding to an average velocity reduction of ∼45%. Particle tracking measurements confirmed a predicted shear in the flow speed, with the surface velocity increasing by 300%, despite the 45% drop in the average bulk speed. The MHD effect makes the bulk flow laminarized but keeps surface waves aligned along the magnetic field lines due to the anisotropy of MHD drag. The 3D fringe field and high surface velocity generate ripples around the outlet region. It was also confirmed that the MHD drag strongly depends on the conductivity of the channel walls, magnetic field, and volumetric flow rate, in agreement with the simulations and a developed analytical model. These validated models are now available to begin to determine the conditions under which the ideal LM channel design of a constant flow speed and fluid depth could be attained.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Exploring the Feasibility of INCONEL® ALLOY 740H® for Power Plant Headers: Integrating Machine Learning with Computational Fluid Dynamics (CFD)

This keynote presentation explores the behavior of headers—essential components of pipeline systems—using ANSYS simulation software and machine learning techniques. The study aims to predict the thermal and mechanical performance of headers under diverse conditions through both steady-state and transient simulations. We investigate critical parameters such as heat transfer coefficient, fluid velocity, and temperature to optimize header design. Conducted as part of a DOE project led by NCAT in collaboration with UNC Charlotte, this research encompasses multiple key topics. The initial section focuses on the behavior of header systems under steady-state conditions using ANSYS simulation. It underscores the importance of headers in industrial infrastructure, especially in the energy sector, and examines the implications of material selection and flow direction on heat transfer dynamics. Methodologically, we employ Computational Fluid Dynamics (CFD) analysis through ANSYS, detailing the development of models, material properties, geometry specifications, boundary conditions, and meshing strategies. Our simulations explore various operational parameters, including temperature and mass flow rates, crucial for predicting heat transfer coefficients and enhancing header design. Results from the study include parametric investigations into mesh sensitivity, viscosity model evaluations, and the effects of heat transfer locations, all validated against theoretical calculations. We conclude with insights on mesh optimization, the suitability of viscosity models, and recommendations for future research aimed at improving header system efficiency and sustainability in industrial applications.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2024

Local Heat Transfer Measurements in Cooler for sCO2 Power Cycles with Dilute Nitrogen and Argon Impurities

An experimental investigation of heat transfer in CO2 and CO2/N2 and CO2/argon mixtures undergoing cooling near the pseudocritical temperature has been conducted. The conditions are representative of direct sCO2 cycle coolers. Three tubing test articles were tested: conventional drawn tubing, an additively manufactured tube with a square cross section, and an additively manufactured tube with a square cross section and ribs angled 60° relative to the flow direction. The axial heat transfer coefficient distribution was determined with local wall temperature measurements. This work concludes that dilute concentrations (< 2%) of nitrogen and argon have a negligible impact on heat transfer coefficient and on friction factor.

Searle, Matthew↗
DOE OSTI2021

Performance of a Hybrid HVAC-Integrated Thermal Storage Device

Thermal equipment in buildings is a primary contributor to peak loads on the electrical grid. Thermal energy storage is a cost-effective strategy to decouple electric use from thermal loads, thus reducing grid peak costs for building owners. One method for storing thermal energy in a building is to integrate a phase change material (PCM) directly into the heating, ventilation, and air conditioning system. These systems often require additional glycol loops, pumps, valves, and heat exchangers to couple the storage to the cooling system and building space, which increases the complexity and cost. This work will discuss an alternate approach where the storage is added directly into the heat pump evaporator. A detailed two-dimensional finite difference heat transfer model of a PCM-refrigerant-glycol heat exchanger was developed to simulate the performance of this component. The fluid stream was discretized along the flow direction to capture changes in the fluid properties and local heat transfer rates, and the phase change material was discretized in both the x and y directions to capture the movement of the melt front. The model was used to understand the impact of different material and geometric properties on the charge and discharge characteristics of the device. Finally, a Ragone framework analogous to that used for electrochemical batteries was used to maximize the energy density and round-trip efficiency of the device while supplying loads appropriate for space cooling in buildings.

buildings↗
NASA NTRS1985

Effect of flow oscillations on cavity drag and a technique for their control

Experiments to relate the state of the shear layer to cavity drag have been performed in a water channel using a 4" axisymmetric cavity model. Detailed flow measurements in various cavity flow oscillation phases, amplitude amplification along the flow direction, distribution of shear stress, and other momentum flux obtained by laser Doppler velocimeter are presented. Measurements show exponential dependence of cavity drag on the length of the cavity. A jump in the cavity drag coefficient is observed as the cavity flow shows a bluff body wake type behavior. Natural and forced oscillations are introduced by a sinusoidally heated thin-film strip which excites the Tollmein-Schlichting waves in the boundary layer upstream of the gap. For a large gap, self-sustained periodic oscillations are observed, while for smaller gaps, which do not oscillate naturally, periodical oscillations can be obtained by external forcing through the strip heater. The drag of the cavity can be increased by one order of magnitude in the non-oscillating case through external forcing. Also, it is possible to completely eliminate mode switching by external forcing. For the first time, it is demonstrated that amplitude of cavity flow Kelvin-Helmholtz wave is dampened or cancelled by introduction of external perturbation of natural flow frequency but different phase.

Gharib, M.↗
DOE OSTI2023

Hierarchical Control and Stability Analysis for a Nonisolated Grid-Tied DC Energy Router Integrating Energy Storage and Partial Distributed Generation

This article proposes a nonisolated dc converter-based energy router (dc-ER) and its operating strategy. Here, the intent is to integrate energy storage (ES), distributed generation (DG), local load, and dc power grid in an autonomous and more efficient way. The ES/DG power ports are coupled with each other in partial-type connections, which obtains higher voltage supply gain and direct input–output power transmission. High-voltage supply gain allows a wide solar power tracking range and the possibility of optimal battery charging/discharging. Direct input–output power transmission improves the energy conversion efficiency. In this article, the operating modes of dc-ER are first analyzed, followed by the optimal hardware design counting the DG current ripple minimization and the limitation caused by the power flow direction. Second, the mathematical model of dc-ER is deduced. The hierarchical control is then proposed to manage port energy in a flexible manner. The stability is analyzed by using impedance modeling. Finally, experimental and simulation results verify the superiorities of the proposed topology in terms of flexible operating mode transition and high-power conversion efficiency.

25 ENERGY STORAGE↗
NASA NTRS1984

Three-dimensional viscous flows with large secondary velocity

A new system of approximation equations is derived for three-dimensional steady viscous compressible flows in which a primary-flow direction is present, but in which both transverse velocity components can be large. Previous approaches which address simplification of the steady Navier-Stokes equations are discussed, and a new approach is proposed. The transverse velocity vector which corrects a given potential flow has been decomposed into potential and rotational components. It is found that the potential-velocity vector may be assumed small, whereas the rotational-velocity vector may be assumed small, whereas the rotational velocity vector and hence the composite secondary flow can be of order unity. This assumption leads to a system of governing equations whose characteristic polynomial has a non-elliptic form for arbitrary Mach numbers. The resulting non-elliptic approximation equations can be solved as an initial/boundary-value problem. Computed results confirm the small scalar-potential approximation.

Briley, W. R.↗
NASA NTRS2013

Deleterious Thermal Effects due to Randomized Flow Paths in Pebble Bed, and Particle Bed Style Reactors

Reactor fuel rod surface area that is perpendicular to coolant flow direction (+S) i.e. perpendicular to the P creates areas of coolant stagnation leading to increased coolant temperatures resulting in localized changes in fluid properties. Changes in coolant fluid properties caused by minor increases in temperature lead to localized reductions in coolant mass flow rates leading to localized thermal instabilities. Reductions in coolant mass flow rates result in further increases in local temperatures exacerbating changes to coolant fluid properties leading to localized thermal runaway. Unchecked localized thermal runaway leads to localized fuel melting. Reactor designs with randomized flow paths are vulnerable to localized thermal instabilities, localized thermal runaway, and localized fuel melting.

Moran, Robert P.↗
NASA NTRS1981

Effects of free-stream turbulence on diffuser performance

An experimental evaluation of the effects of free-stream turbulence on the performance of a subsonic two-dimensional diffuser has been made. Increases of the diffuser's static pressure recovery coefficient of 11.3 and 23.9 percent at total included divergence angles of 12 and 20 degrees respectively were obtained when the value of the inlet integral free-stream scale of turbulence in the flow direction was at least 7.2 times larger than the inlet boundary layer displacement thickness, when the inlet total free-stream turbulence intensity was at least 3.5 percent, and when the axes of upstream rods used to generate turbulence were perpendicular to the flow and parallel to the diverging walls of the diffuser. It is hypothesized that a larger scale of turbulence with the specified eddy axis orientation transmits the free-stream energy to the walls more effectively and, when coupled with large turbulence intensities, are mechanisms which act to decrease the distortion and delay separation within the diffuser.

Hoffmann, J. A.↗
NASA NTRS1978

Energetic plasma ions within the earth's magnetosheath

Observations in the dawn magnetosheath with the LASL/MPI fast plasma experiment on ISEE 1 and 2 reveal the existence of two distinct states of plasma flow within the sheath: a quiet state and a disturbed state. Energetic ions in the range of 3-40 keV are the distinguishing feature of the disturbed state. Long period (about 1 min) fluctuations in plasma density, temperature, flow speed, and flow direction occur simultaneously with the appearance of these high-energy particles. The most likely explanation of these observations is that the energetic ions are produced in the vicinity of the bow shock under certain (unspecified) interplanetary conditions, and that the fluctuations in plasma flow are produced locally by the interaction of the energetic ions with the ambient plasma.

Asbridge, J. R.↗
NASA NTRS1983

Aerothermodynamic design considerations of an aerobraked spacecraft

The major aerothermodynamic design issues that influenced the VOIR (Venus Orbiting Image Radar) airbrake and mission design are discussed. In the discussion of aerobrake heating, it is pointed out that the heat transfer to the deployed aerobrake is a function of the flow regime encountered during the periapsis pass, the perapsis altitude, and the brake surface geometry. The discussion of spacecraft thermal protection encompasses separated flow heating, aerobrake backface radiation, total solar cell heating, and undeployed aerobrake effects. The aerobrake is designed to protect the spacecraft thermally by limiting the integrated entry heating to the critical solar cell arrays (located on three sides of the spacecraft) due to flow impingement heating, separated flow heating, and backface radiation heating. It is explained that these design considerations led to the selection of a flat-faced aerobrake design located on the front of the spacecraft to provide maximum spacecraft thermal protection. The 8.4-m equivalent diameter aerobrake eliminates direct flow impingement heating and lowers separated flow heating on the spacecraft.

Florence, D.↗
NASA NTRS1984

Heat transfer enhancement in channels with turbulence promoters

Repeated rib-roughness elements have been used in advanced turbine cooling designs to enhance the internal heat transfer. Often the ribs are perpendicular to the main flow direction so that they have an angle-of-attack of 90 degrees. The objective of this investigation was to determine the effect of rib angle-of-attack on the pressure drop and the average heat-transfer coefficients in the fully developed turbulent air flow in a square duct with two opposite rib-roughened walls for Reynolds numbers varied from 7,000 to 90,000. The rib height-to-equivalent diameter ratio was kept at a constant value of 0.063, the rib pitch-to-height ratio was varied from 10 to 20, and the rib angle-of-attack (alpha) was varied from 90 to 60 deg to 45 to 30 deg, respectively. The thermal-performance comparison indicated that the increased heat conductance for the rib with an oblique angle to the flow (alpha = 45 deg - 30 deg) was about 10-20 percent higher than the rib with a 90 deg angle to the flow, and the pumping power requirement for the angled rib was about 20-50 percent lower than the transverse rib. Semi-empirical correlations for friction factor and heat-transfer coefficients were developed to account for rib spacing and rib angle. The correlations can be used in the design of turbine-blade cooling passages.

Han, J. C.↗
DOE OSTI2022

Fluid – Fluid Interfacial Area and Its Impact on Relative Permeability - A Pore Network Modeling Study

Abstract Relative permeability (kr) is commonly modeled as an empirical function of phase saturation. Although current empirical models can provide a good match of one or two measured relative permeabilities using saturation alone, they are unable to predict relative permeabilities well when there is hysteresis or when physical properties such as wettability change. Further, current models often result in relative permeability discontinuities that can cause convergence and accuracy problems in simulation. To overcome these problems, recent research has modeled relative permeability as a state function of both saturation (S) and phase connectivity (X). Pore network modeling (PNM) data, however, shows small differences in relative permeability for the same S-X value when approached from a different flow direction. This paper examines the impact of one additional Minkowski parameter (Mecke and Arns, 2005), the fluid-fluid interfacial area, on relative permeability to identify if that satisfactorily explains this discrepancy. We calculate the total fluid-fluid interfacial areas (IA) during two-phase (oil/water) flow in porous media using pore network modeling. The area is calculated from PNM simulations using the areas associated with corners and throats in pore elements of different shapes. The pore network is modeled after a Bentheimer sandstone, using square, triangular, and circular pore shapes. Simulations were conducted for numerous primary drainage and imbibition cycles at a constant contact angle of 0° for the wetting phase. Simultaneous measurements of capillary pressure, relative permeability, saturation, and phase connectivity are made for each displacement. Fluid-fluid interfacial area is calculated from the PNM capillary pressure, the fluid location in the pore elements, and the pore element dimensional data. The results show that differences in the relative permeability at the same (S,X) point is explained well by differences in the fluid-fluid interfacial area (IA). That is, for a larger change in IA at these intersection points, the permeability difference is greater. That difference in relative permeability approaches zero as the difference in IA approaches zero. This confirms that relative permeability can be modeled better as a unique function of S, X, and IA. The results also show that an increase in IA restricts flow decreasing the nonwetting (oil) phase permeability. This decrease is caused by an increase in the throat area fraction compared to the corner area as the total area IA increases. The wetting phase relative permeability, however, shows the inverse trend, in that its relative permeability is greater when IA becomes larger owing to a greater fraction of the total area associated with the corners. The area IA, however, impacts the nonwetting phase relative permeability more than the wetting phase relative permeability. Corner flow improves the wetting phase relative permeability because the wetting phase is continuous there. Finally, a sensitivity analysis shows that relative permeability a is more sensitive to change in S than they are for IA for the case studied implying that if only two parameters are used to model relative permeability it is better to choose S and X.

Engineering↗
NASA NTRS1980

Three dimensional mean flow and turbulence characteristics of the near wake of a compressor rotor blade

The investigation was carried out using the rotating hot wire technique. Measurements were taken inside the end wall boundary layer to discern the effect of annulus and hub wall boundary layer, secondary flow, and tip leakage on the wake structure. Static pressure gradients across the wake were measured using a static stagnation pressure probe insensitive to flow direction changes. The axial and the tangential velocity defects, the radial component of velocity, and turbulence intensities were found to be very large as compared to the near and far wake regions. The radial velocities in the trailing edge region exhibited characteristics prevalent in a trailing vortex system. Flow near the blade tips found to be highly complex due to interaction of the end wall boundary layers, secondary flows, and tip leakage flow with the wake. The streamwise curvature was found to be appreciable near the blade trailing edge. Flow properties in the trailing edge region are quite different compared to that in the near and far wake regions with respect to their decay characteristics, similarity, etc. Fourier decomposition of the rotor wake revealed that for a normalized wake only the first three coefficients are dominant.

Ravindranath, A.↗
NASA NTRSDate not supplied

Numerical Simulations of A Conceptual MSR-EES Shoulder Recession

The present study demonstrates our in-house material response solver, Icarus's capability to simulate the ablative conditions, including pyrolysis effects due to the interaction between hypersonic boundary layers and the thermal protection system (TPS). A conceptual aeroshell shoulder design, which undergoes mission-relevant flow and material conditions, is selected for the demonstration purpose. LAURA, a structured flow solver, is used to solve flow around the shoulder at several trajectory points of a flight path. The aerothermal dataset obtained from LAURA is used to enforce boundary conditions on the aeroshell wall to simulate ablation processes. The two-layered material system is stacked with HEEET (TPS) and Aluminum (actual material). A set of base parameters, such as the angle of material orientation with respect to the flow direction, convective heat-transfer co-efficient, and aerothermal boundary conditions on the rear end of the HEEET material layer, is selected to conduct a base-case simulation. A small amount of recession was observed, indicating that the design should be fine to go through the selected flow and material conditions. Furthermore, the parameters mentioned above are individually altered and are observed to affect the shoulder design's recession compared to the base case. Verification of our Icarus setup was also carried out using a one-dimensional grid and FIAT, a one-dimensional material-response solver, to build credibility for our results. As the current work is an uncoupled fluid-material-response simulation, a local sharp mesh deformation in the recessed surface near the shoulder corner is observed.

Prakash Shrestha↗
NASA NTRS1979

Use of arc-jet hypersonic blunted wedge flows for evaluating performance of Orbiter TPS

Arc-jet tests at NASA/JSC have been conducted recently to evaluate the performance of the Orbiter Thermal Protection System (TPS) on three critical areas of the side and top of the Orbiter fuselage: (1) cargo bay door, (2) crew access door, and (3) LRSI/FRSI joint regions. Test articles corresponding to these three areas on the Orbiter were mounted in an arc-jet test chamber in a blunted-wedge holder and exposed to hypersonic flow at various angles of attack. The effects of flow direction, heating load, and overtemperature were investigated. In addition, the reuse capability of the TPS materials was evaluated, along with the protection of the pressure seals within the test articles. Thermal match model predictions correlated well with primary structure thermocouple data. Heating rate and pressure predictions based on a nonequilibrium flow field computer program showed good agreement with arc-jet test data and existing hypersonic flow theories.

Rochelle, W. C.↗
NASA NTRS1981

A note on the location of the stagnation point in the magnetosheath flow

While observational and theoretical investigations have clearly indicated that the shape of the magnetosphere is very nearly symmetric about the plane determined by the aberrated solar wind flow direction and the earth's magnetic dipole, many processes such as magnetic pulsations and geomagnetic activity which should be shape dependent do not exhibit symmetry about this plane. The present paper proposes a solution to this apparent paradox in terms of the shifting of the stagnation point in the magnetosheath flow. It is shown that the interplanetary magnetic field can act to shift the stagnation point on the order of 15 deg from the nose towards dawn during periods of low Alfven Mach number without an appreciable aberration of the magnetopause, accounting for the observations of pulsation demarcation and magnetic reconnection.

Russell, C. T.↗