SEARCH · Engineering Papers

Results for “heat flow”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 883 records · Page 49

All sources NASA NTRS DOE OSTI

NASA NTRS1997

Flow and Crystallization in Two-Layer Liquid Systems with and without a Magnetic Field

Flow, heat and mass transfer in a two-layer liquid system is investigated when the layers are subjected to a static magnetic field. The physical system consists of two immiscible liquids in a layer configuration with a free surface and an interfacial layer simulating two crystal growth configurations, namely, floating zone and horizontal zone melting. Mass transfer effects due to crystallization of one of the layers is also considered. The resulting flows are categorized into three types depending on: (a) the dominance of the free surface effect top layer, (b) a balance between the thermocapillary effect on the free surface and the interface effect between the two layers, or (c) the dominance of interfacial effects, in determining the system thermo-fluid characteristics. The use of an additional liquid layer atop the crystallizing layer leads to a reduction of the radial dopant inhomogeneity in comparison to the one-layer case. The effect an externally imposed magnetic field on dopant distribution in this two-layer configuration is rather ambiguous and depends on its direction and intensity resulting in the necessity of optimizing the applied magnetic field for a specific situation. In case of electrically non-conducting melts, the calculations show that some measure of flow control can be achieved by using an electrically conducting encapsulant layer of the desired thickness.

Feonychev, Alexander I.↗

DOE OSTI2025

MOSCATO Development and Integration in Fiscal Year 2025: Implementation of Multiphase, Multiphysics Modeling Capabilities for Molten Salt Systems

MOSCATO (Molten Salt Chemistry and Transport) is a multiphysics code that provides high-fidelity, coupled simulations of fluid flow, heat transfer, mass transfer, chemistry, electrochemical phenomena, and alloy corrosion for molten salt systems. In FY25, significant developments were made to the code package, enhancing its capabilities for modeling all relevant phenomena within operating moltens salt reactors (MSRs). The developments and activities in FY25 included: 1. Implementation of Level-Set methods to enable modeling of single-bubble behavior in molten salts. In FY25, the Level-Set two-phase flow modeling implementation was improved to simulate single bubble behavior with molten salt media. The large density and viscosity ratios between typical gases and molten salt liquids present challenges for these types of numerical solvers. With enhancements to the pressure projection method, MOSCATO’s Level-Set solver was able to be successfully validated to experiments related to helium bubble rise in stagnant molten salt. The simulated bubble rising velocity showed reasonable good agreement with experimental measurements. The bubble shape and dynamics were also visually compared with experimental snapshots, demonstrating a good qualitative match. 2. Generation of mass transfer correlations for multiphase flow systems. To enable calculations of the tritium transport across the interface between gas bubbles and salt, we modeled high- Schmidt-number mass transfer around a sphere across a broad range of Reynolds numbers. The mesh near the sphere surface was highly refined to resolve steep concentration gradients caused by the low diffusion coefficient. Literature-based mass transfer correlations were compared with the numerical results, and modifications were proposed to improve agreement, particularly at higher Schmidt numbers. These mass transfer correlations were subsequently provided to other national laboratories to help enable high quality mass transfer simulations using lower-order solvers under development within the NEAMS program. 3. Preliminary implementation of a bubbly flow solver. To model bubbly flow in molten salt, we implemented a bubbly flow solver for void fractions less than 5%. To do so, an algebraic relative velocity model that assumes small bubbles with rapid momentum equilibration was added to MOSCATO to compute bubble velocities. Preliminary comparisons with experimental data showed reasonable agreement, and further improvements are underway. 4. Generation of mass transfer correlations for MSRE subchannel The Molten-Salt Reactor Experiment (MSRE) was a landmark historical project that demonstrated the feasibility of molten-salt reactor technology. The MSRE campaign also generated a significant body of experimental data and reports that continue to support molten-salt–related research. In this report, the MSRE core subchannel was used as the reference geometry for a mass transfer study performed with MOSCATO. The geometry and computational mesh were adapted from a previous study, providing adequate resolution for the relatively low Reynolds number in this case. Additional mesh refinement was applied to reach higher Schmidt numbers, enabling the derivation of a reliable mass-transfer correlation for the present scenario. 5. Simulations of oxygen ingressions into molten salt. In the previous fiscal year, we initiated a study to simulate oxygen ingression in stagnant salt. As oxygen enters the salt through its surface, it reacts with Ce 3+ to form solid CeO 2 and other reaction products. To more fully capture the complex diffusion-convection-reaction mechanisms, capabilities for modeling natural convection in the salt vessel were added. These were needed as the flow of the ingressed gas induced flow in the salt caused by surface shear and non-isothermal effects. With these updated physics in place, we were able to successfully reproduce the experimental results for the rate of change of CeCl 3 concentrations versus time. 6. Flow corrosion model validation. In FY24, MOSCATO’s corrosion model was validated against static corrosion experiments. In FY25, this work was extended to a flow corrosion experiment, where FLiNaK salt was driven by natural convection, with initial salt impurities to initiate corrosion. Despite uncertainties in parameters such as elemental diffusion coefficients in the alloy and unknown H + concentrations, the simulations achieved good agreement with experimental results, especially in predicting sample mass losses.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

NASA NTRS1993

A study of the effects of macrosegregation and buoyancy-driven flow in binary mixture solidification

A generalized anisotropic porous medium approach is developed for modelling the flow, heat and mass transport processes during binary mixture solidification. Transient predictions are obtained using FEM, coupled with an implicit time-marching scheme, for solidification inside a two-dimensional rectangular enclosure. A parametric study focusing attention on the effects of solutal buoyancy and thermal buoyancy is presented. It is observed that three parameters, namely the thermal Rayleigh number, the solutal Rayleigh number, and the relative density change parameter, significantly alter the flow fields in the liquid and the mushy regions. Depending upon the nature of these flow fields, the solute enrichment caused by macrosegregation may occur in the top or the bottom region of the enclosure.

Sinha, S. K.↗

DOE OSTI2021

Impact of KOH on the interfacial precipitation rates of C-S-H during the early hydration of C3S

In this work we investigated the influence of alkalis on the hydration of two triclinic samples of C{sub 3}S. One pure C{sub 3}S and one Al-doped C{sub 3}S (0.5 wt.‐% Al{sub 2}O{sub 3}). We added differently concentrated KOH solutions representing alkalis in the pore solution, which lead to an increase of the interfacial precipitation rates of C-S-H during the hydration of C{sub 3}S compared to the hydration without KOH. Isothermal calorimetry was conducted for the determination of the rates of reaction during the hydration process and ICP-OES measurements for the determination of the pore solution composition at certain times of hydration. The increasing effect of KOH solution on the calculated interfacial precipitation rates from pore solution data can explain the enhancement of the rates of reaction recorded by heat flow calorimetry during the early hydration. Therefore, the interfacial precipitation rates of C-S-H can accurately describe the acceleration effect of alkalis on the early hydration of C{sub 3}S.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Extended-magnetohydrodynamics in under-dense plasmas

Extended-magnetohydrodynamics (MHD) transports magnetic flux and electron energy in high-energy-density experiments, but individual transport effects remain unobserved experimentally. Two factors are responsible in defining the transport: electron temperature and electron current. Here, each electron energy transport term has a direct analog in magnetic flux transport. To measure the thermally driven transport of magnetic flux and electron energy, a simple experimental configuration is explored computationally using a laser-heated pre-magnetized under-dense plasma. Changes to the laser heating profile precipitate clear diagnostic signatures from the Nernst, cross-gradient-Nernst, anisotropic conduction, and Righi-Leduc heat-flow. With a wide operating parameter range, this configuration can be used in both small and large scale facilities to benchmark MHD and kinetic transport in collisional/semi-collisional, local/non-local, and magnetized/unmagnetized regimes.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS1990

Space Cryogenic Workshop, 8th, California Institute of Technology, Pasadena, July 31, Aug. 1, 1989, Proceedings

Recent advances in cryogenic technology for space applications are examined in reviews and reports. Topics addressed include very-low-force cooling contacts for the ISO cryostat cover, convective heat flow in space cryogenics plugs, liquid-acquisition devices for superfluid He transfer, and pressure drop in the SHOOT superfluid-He acquisition system. Consideration is given to a liquid-He vibration cryostat for space qualification tests, closed-cycle coolers for temperatures below 30 K, stress analysis down to liquid-He temperature, a cryogenic valve actuator, and a spaceborne He-3 refrigerator. Also discussed are an adiabatic-demagnetization refrigerator for SIRTF, rejection of waste heat from O liquefaction operations at a lunar O production plant, SHOOT flowmeter and pressure transducers, and space qualification of the ISO cryogenic rupture disks.

Source record↗

DOE OSTI2023

Geothermal Play Fairway Analysis, Part 2: GIS methodology

Play Fairway Analysis (PFA) in geothermal exploration originates from a systematic methodology developed within the petroleum industry and is based on a geologic, geophysical, and hydrologic framework of identified geothermal systems. We tailored this methodology to study the geothermal resource potential of the Snake River Plain and surrounding region, but it can be adapted to other geothermal resource settings. We adapted the PFA approach to geothermal resource exploration by cataloging the critical elements controlling exploitable hydrothermal systems, establishing risk matrices that evaluate these elements in terms of both probability of success and level of knowledge, and building a code-based ‘processing model’ to process results. A geographic information system was used to compile a range of different data types, which we refer to as elements (e.g., faults, vents, heat flow, etc.), with distinct characteristics and measures of confidence. Discontinuous discrete data (points, lines, or polygons) for each element were transformed into continuous interpretive 2D grid surfaces called evidence layers. Because different data types have varying uncertainties, most evidence layers have an accompanying confidence layer which reflects spatial variations in these uncertainties. Risk layers, as defined here, are the product of evidence and confidence layers, and are the building blocks used to construct Common Risk Segment (CRS) maps for heat, permeability, and seal, using a weighted sum for permeability and heat, but a different approach with seal. CRS maps quantify the variable risk associated with each of these critical components. In a final step, the three CRS maps were combined into a Composite Common Risk Segment (CCRS) map, using a modified weighted sum, for results that reveal favorable areas for geothermal exploration. Additional maps are also presented that do not mix contributions from evidence and confidence (to allow an isolated view of evidence and confidence), as well as maps that calculate favorability using the product of components instead of a weighted sum (to highlight where all components are present). Our approach helped to identify areas of high geothermal favorability in the western and central Snake River Plain during the first phase of study and helped identify more precise local drilling targets during the second phase of work. By identifying favorable areas, this methodology can help to reduce uncertainty in geothermal energy exploration and development.

15 GEOTHERMAL ENERGY↗

NASA NTRS1981

Internal structures of the Galilean satellites

Models for the interior structures of Io, Ganymede and Callisto are proposed based on recent discoveries of volcanism and high heat flow on Io, a primordial, heavily cratered surface on Callisto, and a surface modified by endogenic processes on Ganymede. The model for Io consists of a thin, high-rigidity outer shell overlying a thin, partially molten or molten layer maintained by tidal dissipation in the outer shell, which in turn surrounds a solid interior. Ganymede is modeled as an ice outer layer surrounding a shell of undifferentiated, primordial ice-silicate mixture and a rock core, with accretional heating responsible for melting the ice in an originally homogeneous ice-silicate interior. Finally, the old, heavily cratered surface of Callisto is interpreted as suggesting a primordial ice-silicate mixture with little, if any, ice-rock differentiation in the interior.

Schubert, G.↗

NASA NTRS2002

Effect of Magnetic Fields on g-jitter Induced Convection and Solute Striation During Space Processing of Single Crystals

A 2-D finite element model is presented for the melt growth of single crystals in a microgravity environment with a superimposed DC magnetic field. The model is developed based on the deforming finite element methodology and is capable of predicting the phenomena of the steady and transient convective flows, heat transfer, solute distribution, and solid-liquid interface morphology associated with the melt growth of single crystals in microgravity with and without an applied magnetic field. Numerical simulations were carried out for a wide range of parameters including idealized microgravity conditions, the synthesized g-jitter and the real g-jitter data taken by on-board accelerometers during space flights. The results reveal that the time varying g-jitter disturbances, although small in magnitude, cause an appreciable convective flow in the liquid pool, which in turn produces detrimental effects during the space processing of single crystal growth. An applied magnetic field of appropriate strength, superimposed on microgravity, can be very effective in suppressing the deleterious effects resulting from the g-jitter disturbances.

deGroh, H. C.↗

DOE OSTI2023

Microscale Imaging of Thermal Conductivity Suppression at Grain Boundaries

Abstract Grain‐boundary engineering is an effective strategy to tune the thermal conductivity of materials, leading to improved performance in thermoelectric, thermal‐barrier coatings, and thermal management applications. Despite the central importance to thermal transport, a clear understanding of how grain boundaries modulate the microscale heat flow is missing, owing to the scarcity of local investigations. Here, thermal imaging of individual grain boundaries is demonstrated in thermoelectric SnTe via spatially resolved frequency‐domain thermoreflectance. Measurements with microscale resolution reveal local suppressions in thermal conductivity at grain boundaries. Also, the grain‐boundary thermal resistance – extracted by employing a Gibbs excess approach – is found to be correlated with the grain‐boundary misorientation angle. Extracting thermal properties, including thermal boundary resistances, from microscale imaging can provide comprehensive understanding of how microstructure affects heat transport, crucially impacting the materials design of high‐performance thermal‐management and energy‐conversion devices.

36 MATERIALS SCIENCE↗

NASA NTRS2017

Heat Loads Due to Small Penetrations in Multilayer Insulation Blankets

The main penetrations (supports and piping) through multilayer insulation systems for cryogenic tanks have been previously addressed by heat flow measurements. Smaller penetrations due to fasteners and attachments are now experimentally investigated. The use of small pins or plastic garment tag fasteners to each the handling and construction of multilayer insulation (MLI) blankets goes back many years. While it has long been understood that penetrations and other discontinuities degrade the performance of the MLI blanket, quantification of this degradation has generally been lumped into gross performance multipliers (often called degradation factors or scale factors). Small penetrations contribute both solid conduction and radiation heat transfer paths through the blanket. The conduction is down the stem of the structural element itself while the radiation is through the hole formed during installation of the pin or fastener. Analytical models were developed in conjunction with MLI perforation theory and Fouriers Law. Results of the analytical models are compared to experimental testing performed on a 10 layer MLI blanket with approximately 50 small plastic pins penetrating the test specimen. The pins were installed at 76-mm spacing inches in both directions to minimize the compounding of thermal effects due to localized compression or lateral heat transfer. The testing was performed using a liquid nitrogen boil-off calorimeter (Cryostat-100) with the standard boundary temperatures of 293 K and 78 K. Results show that the added radiation through the holes is much more significant than the conduction down the fastener. The results are shown to be in agreement with radiation theory for perforated films.

Structural attachments↗

NASA NTRS1978

Heat and moisture flow in concrete as a function of temperature

Due to temperature, reactors in operation cause heat and moisture flows in the thick walled prestressed pressure vessels. These flows were studied in three beams of concrete made with crushed limestone aggregate, and in three beams made of crushed gravel/sand aggregate. The flow phenomena were related to the structural development of the concrete by determining the amount of non-evaporatable water, the total porosity, and the pore size distribution. Local temperature and moisture conditions also influenced the technical properties. Compressive strength, changes in length due to shrinkage and contraction, thermal expansion, and thermal conductivity were determined.

Hundt, J.↗

NASA NTRS1981

Automatic thermal switch

An automatic thermal switch to control heat flow includes a first thermally conductive plate, a second thermally conductive plate and a thermal transfer plate pivotally mounted between the first and second plates. A phase change power unit, including a plunger connected to the transfer plate, is in thermal contact with the first thermally conductive plate. A biasing element, connected to the transfer plate, biases the transfer plate in a predetermined position with respect to the first and second plates. When the phase change power unit is actuated by an increase in heat transmitted through the first plate, the plunger extends and pivots the transfer plate to vary the thermal conduction between the first and second plates through the transfer plate. The biasing element, transfer plate and piston can be arranged to provide either a normally closed or normally open thermally conductive path between the first and second plates.

Wing, L. D.↗

DOE OSTI2024

Geothermal play fairway analysis, part 1: Example from the Snake River Plain, Idaho

The Snake River Plain (SRP) volcanic province overlies the track of the Yellowstone hotspot, a thermal anomaly that extends deep into the mantle. Most of the area is underlain by a basaltic volcanic province that overlies a mid-crustal intrusive complex, which in turn provides the long-term heat flux needed to sustain geothermal systems. Previous studies have identified several known geothermal resource areas within the SRP. For the geothermal study presented herein, our goals were to: (1) adapt the methodology of Play Fairway Analysis (PFA) for geothermal exploration to create a formal basis for its application to geothermal systems, (2) assemble relevant data for the SRP from publicly available and private sources, and (3) build a geothermal PFA model for the SRP and identify the most promising plays, using GIS-based software tools that are standard in the petroleum industry. The study focused on identifying three critical resource parameters for exploitable hydrothermal systems in the SRP: heat source, reservoir and recharge permeability, and cap or seal. Data included in the compilation for heat source were heat flow, distribution and ages of volcanic vents, groundwater temperatures, thermal springs and wells, helium isotope anomalies, and reservoir temperatures estimated using geothermometry. Reservoir and recharge permeability was inferred from the analysis of stress orientations and magnitudes, post-Miocene faults, and subsurface structural lineaments based on magnetics and gravity data. Data for cap or seal included the distribution of impermeable lake sediments and clay-seal associated with hydrothermal alteration below the regional aquifer. These data were used to compile Common Risk Segment maps for heat, permeability, and seal, which were combined to create a Composite Common Risk Segment map for all southern Idaho that reflects the risk associated with geothermal resource exploration and identifies favorable resource tracks. Our regional assessment indicated that undiscovered geothermal resources may be located in several areas of the SRP. Two of these areas, the western SRP and Camas Prairie, were selected for more detailed assessment, during which heat, permeability, and seal were evaluated using newly collected field data and smaller grid parameters to refine the location of potential resources. These higher resolution assessments illustrate the flexibility of our approach over a range of scales.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1983

Modified jet noise source model for twin-jet shielding analysis

An analytical method to estimate the influence that a jet of heated flow has on the noise emission from a parallel jet is presented. The shielding jet is modelled as a cylinder of constant cross-section in which the flow speed and temperature are uniform throughout. The jet noise emission is modelled by a point source with directivity imposed. The directivity term consists of: a self-noise term, a shear-noise term, and a convection factor. The self- and shear-noise terms each contain a basic directivity factor multiplying a spectral shape function. The various components are evaluated based on comparison with isothermal jet radiation experimental data. The modified source term is incorporated into the jet shielding model and compared to heated twin jet shielding data. The estimated spectra agree well except further downstream of the nozzle where peak of the noise spectrum estimated by the model lies approximately one octave below the experimental peak. The noise reduction estimated by the model agrees favorably with experiment in the near downstream region. This discrepancy is explained in terms of the shielding mechanism which is dominant far downstream.

Gerhold, C. H.↗

DOE OSTI2020

Geothermal Deep Direct Use for Turbine Inlet Cooling in East Texas

The National Renewable Energy Laboratory (NREL), the Southern Methodist University Geothermal Laboratory (SMU), Eastman Chemical (Longview, TX), and TAS (Houston, TX) evaluated the feasibility of using geothermal heat to improve the performance of a natural-gas power plant in East Texas. The area of interest is the Eastman Chemical plant in Longview, Texas, which is on the northwestern margin of a geologic region known as the Sabine Uplift. The feasibility study focused on determining the potential for accessing a subsurface hot-water geothermal resource within a 10-km radius of the site to provide thermal energy for absorption chillers. Wells within a 20-km radius are included for broader geological comparison to determine the heat flow, temperature-at-depth, field porosity and permeability. The lithologies of most interest are the Lower Cretaceous Trinity Group and Upper Jurassic Cotton Valley Group. The deeper Cotton Valley formations are hotter (averaging 117 to 130°C), yet permeability and porosity are low. The shallower Trinity Group contains more variability in permeability and porosity and lower temperatures averaging about 98 to 117°C. The shallower formations are considered despite the lower temperature because of increased ability to produce larger volumes of water and extract enough heat before reinjection. The complete SMU analysis is available in the National Geothermal Data System (NGDS). Tapping such deep geothermal sources for direct heating (as opposed to power generation) is known as geothermal deep direct use (DDU). Geothermal DDU has potential across a wide swath of the United States but is underutilized due to challenging project economics associated with developing a deep geothermal resource for what are typically small-scale, variable-demand projects. This project examines the feasibility of geothermal energy integration in a natural-gas combined cycle power station in East Texas. The DDU resource is tapped to drive absorption chillers (24/7) for production of chilled water at 5-10°C (41-50°F). This chilled water is stored until needed, which allows for continuous operation with a relatively small-capacity geothermal/absorption chiller system. When conditions are favorable, the chilled water is dispatched to cool the air entering the compressor stage of a gas combustion turbine. This process, known as turbine inlet cooling (TIC), boosts power production during periods of high temperature and high-power demand. Such systems can enhance grid reliability and reduce the cost for peak-demand power. A simulation model of the power plant was developed in IPSEpro software and validated against operational data from the plant. This model allowed the team to estimate the additional power that could be produced by applying TIC under different operating and ambient conditions. Absorption chiller performance was estimated from vendor sources to determine the production rate of chilled water from the geothermal resource. Geothermal drilling and development costs were estimated using NREL's GEOPHIRES 2.0. The expected lower drilling costs in this region led to an estimated cost of geothermal heat of about $4/MMBtu (1.4 cents/kWh t ). The estimated cost for the absorption chillers and TIC hardware were obtained from literature sources and project partners. Hourly data were obtained for weather, natural gas and electricity prices, and plant operating state for 2017, which served as a representative year. NREL estimated the capital cost, operating cost, and additional electricity production and revenue for different combinations of geothermal capacity, chiller capacity, and water storage-tank size. The analysis drove toward smaller geothermal and chiller systems to reduce equipment cost. A relatively low-cost water storage tank accumulated the near-continuous chilled water output for later use when TIC was most valued.

15 GEOTHERMAL ENERGY↗

NASA NTRS1982

Heat Pipe Blocks Return Flow

Metal-foil reed valve in conventional slab-wick heat pipe limits heat flow to one direction only. With sink warmer than source, reed is forced closed and fluid returns to source side through annular transfer wick. When this occurs, wick slab on sink side of valve dries out and heat pipe ceases to conduct heat.

Eninger, J. E.↗

NASA NTRS1977

Crystallization kinetics, viscous flow, and thermal history of lunar breccia 67975

The maximum crystal growth rate for the 67975 matrix composition, about 0.00073 cm/min, was found to occur at about 990 C (undercooling 220 C). The Shaw (1972) model and, to a slightly lesser extent, the Bottinga and Weill (1972) model indicate the variation of viscosity with temperature. Time-temperature-transformation and continuous cooling curves were constructed from the measured crystal growth rates and viscosities and used to estimate the cooling rate required to form bodies with the degree of crystallinity observed in the matrix of the breccia. It is estimated on the basis of kinetic analysis that the 67975 breccia cooled at a rate of about 0.06 C/min over the temperature range below the liquidus. Heat flow analyses indicate that the 67975 breccia did not cool in the size of the lunar sample but as part of a much larger body. Viscous singering as well as cooling of a melt-clast mixture are investigated.

Uhlmann, D. R.↗