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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

The rebound shock model for solar spicules - Dynamics at long times

The spicule model due to Hollweg is extended and developed. The dynamics is emphasized here; radiative and ionization losses, heat conduction, and nonshock heat input, are not included. In the model, a series of rebound shocks results in chromospheric material with spicule-like properties below a raised transition region. The shocks result from a single quasi-impulsive source in the photosphere. It is found that at long times, the model approaches a new hydrostatic equilibrium with the transition region remaining raised, and with a region of shock-heated chromosphere below it. Attention is given to the variation of the properties of the model in response to different values for the magnitude and location of the source, and to different initial transition region heights. It is concluded that the model is capable of generating structures with properties consistent with observations of spicules (with the exception of temperature) when only the dynamics is considered.

Sterling, Alphonse C.↗
NASA NTRS1979

Gap heating with pressure gradients

The heating rate distribution and temperature response on the gap walls of insulating tiles is analyzed to determine significant phenomena and parameters in flows where there is an external surface pressure gradient. Convective heating due to gap flow, modeled as fully developed pipe flow, is coupled with a two-dimensional thermal model of the tiles that includes conduction and radiative heat transfer. To account for geometry and important environmental parameters, scale factors are obtained by curve-fitting measured temperatures to analytical solutions. These scale factors are then used to predict the time-dependent gap heat flux and temperature response of tile gaps on the Space Shuttle Orbiter during entry.

Scott, C. D.↗
NASA NTRS1993

Flow instability in particle-bed nuclear reactors

A three-dimensional model of the stability of the particle-bed reactor is presented, in which the fluid has mobility in three dimensions. The model accurately represents the stability at low Re numbers as well as the effects of the cold and hot frits and of the heat conduction and radiation in the particle bed. The model can be easily extended to apply to the cylindrical geometry of particle-bed reactors. Exemplary calculations are carried out, showing that a particle bed without a cold frit would be subject to instability if operated at the high-temperature ratios used for nuclear rockets and at power densities below about 4 MW/l; since the desired power density for such a reactor is about 40 MW/l, the operation at design exit temperature but at reduced power could be hazardous. Calculations show however that it might be possible to remove the instability problem by appropriate combinations of cold and hot frits.

Kerrebrock, J. L.↗
NASA NTRS2006

Finite Volume Numerical Methods for Aeroheating Rate Calculations from Infrared Thermographic Data

The use of multi-dimensional finite volume heat conduction techniques for calculating aeroheating rates from measured global surface temperatures on hypersonic wind tunnel models was investigated. Both direct and inverse finite volume techniques were investigated and compared with the standard one-dimensional semi-infinite technique. Global transient surface temperatures were measured using an infrared thermographic technique on a 0.333-scale model of the Hyper-X forebody in the NASA Langley Research Center 20-Inch Mach 6 Air tunnel. In these tests the effectiveness of vortices generated via gas injection for initiating hypersonic transition on the Hyper-X forebody was investigated. An array of streamwise-orientated heating striations was generated and visualized downstream of the gas injection sites. In regions without significant spatial temperature gradients, one-dimensional techniques provided accurate aeroheating rates. In regions with sharp temperature gradients caused by striation patterns multi-dimensional heat transfer techniques were necessary to obtain more accurate heating rates. The use of the one-dimensional technique resulted in differences of 20% in the calculated heating rates compared to 2-D analysis because it did not account for lateral heat conduction in the model.

Daryabeigi, Kamran↗
DOE OSTI2022

Coupling subsurface and above-surface models for optimizing the design of borefields and district heating and cooling systems in the presence of varying water-table depth. In: Proceedings, 46th Workshop on Geothermal Reservoir Engineering

Dynamic energy simulation is important for the design and sizing of district heating and cooling systems with geothermal heat exchange. Current modeling approaches in building and district energy simulation tools typically consider heat conduction through the ground between boreholes, without flow of groundwater. On the other hand, detailed simulation tools for subsurface heat and mass transfer exist, but these fall short in simulating above-surface energy systems. To support the design and operation of such systems, we have developed a coupled model including a software package for building and district energy simulation, and software for detailed heat and mass transfer in the ground. For the first, we use the open-source Modelica Buildings Library, which includes dynamic simulation models for building and district energy and control systems. For the heat and mass transfer in the soil, we use the TOUGH simulator. TOUGH can model heat and multi-phase, multi-component mass transport for a variety of fluid systems, as well as chemical reactions, in fractured porous media. In previous work, we described the coupling of these software packages, including how time-dependent boundary conditions for the borehole walls are synchronized for use in Modelica and TOUGH. We verified that the coupled Modelica/TOUGH code produced consistent results with the original Modelica code for an idealized problem in which heat transfer was purely by conduction in a uniform geologic medium. Here, we examine less idealized problems for which TOUGH’s advanced capabilities for modeling fluid flow are required. The first problem has a shallow vadose zone, and the second problem has a thicker vadose zone with a water-table depth that varies in time, which requires a fine vertical grid discretization for the TOUGH model.

Doughtry, Christine↗
NASA NTRS1991

A finite element model of conduction, convection, and phase change near a solid/melt interface

Detailed understanding of heat transfer and fluid flow is required for many aerospace thermal systems. These systems often include phase change and operate over a range of accelerations or effective gravitational fields. An approach to analyzing such systems is presented which requires the simultaneous solution of the conservation laws of energy, momentum, and mass, as well as an equation of state. The variable property form of the governing equations are developed in two-dimensional Cartesian coordinates for a Newtonian fluid. A numerical procedure for solving the governing equations is presented and implemented in a computer program. The Galerkin form of the finite element method is used to solve the spatial variation of the field variables, along with the implicit Crank-Nicolson time marching algorithm. Quadratic Langrangian elements are used for the internal energy and the two components of velocity. Linear Lagrangian elements are used for the pressure. The location of the solid/liquid interface as well as the temperatures are determined form the calculated internal energy and pressure. This approach is quite general in that it can describe heat transfer without phase change, phase change with a sharp interface, and phase change without an interface. Analytical results from this model are compared to those of other researchers studying transient conduction, convection, and phase change and are found to be in good agreement. The numerical procedure presented requires significant computer resources, but this is not unusual when compared to similar studies by other researchers. Several methods are suggested to reduce the computational times.

Viterna, Larry A.↗
DOE OSTI2020

FAST-1.0 Software Release Document

The purpose of this document is to detail the release of FAST-1.0 and the documents that accompany the development and testing of FAST-1.0. Design requirements were for FAST-1.0 developed in the NRC Statement of Work (SOW) for NRC Agreement Number NRC-HQ-25-14-D-001 and are transcribed to this document as part of the Software Quality Assurance Plan for the FAST Code System, PNNL-28767. FAST 1.0 represents the merger of the FRAPCON and FRAPTRAN codes and as such FAST-1.0 performs steady state and transient fuel performance calculations described below. FAST-1.0 calculates the steady state response of light-water reactor fuel rods during long-term burnup. The code calculates temperature, pressure, and deformation of a fuel rod as functions of time-dependent fuel rod power and coolant boundary conditions. The phenomena modeled by the code include: 1) heat conduction through fuel and cladding to the coolant; 2) cladding elastic and plastic deformation; 3) fuel-cladding mechanical interaction; 4) fission gas release from the fuel and rod internal pressure; and 5) cladding oxidation. FAST is used to perform independent calculations for regulatory evaluations of fuel performance under normal operation and anticipated operational occurrences (AOOs).

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
NASA NTRS1972

A numerical study of a three dimensional spherical thermospheric density and wind model

Numerical calculations of the generation and propagation of the two important fundamental symmetric tidal wave modes - the diurnal mode (1, 1, 1,) and the semidiurnal mode (2, 2, 2) - were performed applying a realistic model thermosphere and taking into account heat conduction and the temporally and spatially varying ion-neutral collision number. Both wave modes are predominantly generated by the solar EUV heat input. It is shown that the latitude structure of the (1, 1, 1)-mode which is identical with the Hough function(1, -1) within the lower non-dissipative atmosphere degenerates into the spherical function P sub 1, 1 at thermospheric heights. The pressure field of this mode constitutes the observed pressure bulge of the thermosphere, the diurnal component of which peaks at 15 h L. T. The electric polarization field of the geomagnetic Sq current generates a significant fraction of this wave mode at F layer heights. This wave component shifts the total horizontal wind system to earlier times by about 1 hour in agreement with ionospheric observations. The latitude structure of the (2, 2, 2) mode is identical with the Hough function (2, 2) within the lower non-dissipative atmosphere. It degenerates to the spherical function P sub 2, 2 at thermospheric heights.

Volland, H.↗
NASA NTRS1985

A mixed pseudospectral/finite difference method for a thermally driven fluid in a nonuniform gravitational field

A numerical study of the steady, axisymmetric flow in a heated, rotating spherical shell is conducted to model the Atmospheric General Circulation Experiment (AGCE) proposed to run aboard a later shuttle mission. The AGCE will consist of concentric rotating spheres confining a dielectric fluid. By imposing a dielectric field across the fluid a radial body force will be created. The numerical solution technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is used in the latitudinal direction, and a second-order accurate finite difference scheme discretizes time and radial derivatives. This paper discusses the development and performance of this numerical scheme for the AGCE which has been modelled in the past only by pure FD formulations. In addition, previous models have not investigated the effect of using a dielectric force to simulate terrestrial gravity. The effect of this dielectric force on the flow field is investigated as well as a parameter study of varying rotation rates and boundary temperatures. Among the effects noted are the production of larger velocities and enhanced reversals of radial temperature gradients for a body force generated by the electric field.

Macaraeg, M. G.↗
NASA NTRS1985

A mixed pseudospectral/finite difference method for a thermally driven fluid in a nonuniform gravitational field

A numerical study of the steady, axisymmetric flow in a heated, rotating spherical shell is conducted to model the Atmospheric General Circulation Experiment (AGCE) proposed to run aboard a later Shuttle mission. The AGCE will consist of concentric rotating spheres confining a dielectric fluid. By imposing a dielectric field across the fluid a radial body force will be created. The numerical solution technique is based on the incompressible Navier-Stokes equations. In the method a pseudospectral technique is used in the latitudinal direction, and a second-order accurate finite difference scheme discretizes time and radial derivatives. This paper discusses the development and performance of this numerical scheme for the AGCE which has been modeled in the past only by pure FD formulations. In addition, previous models have not investigated the effect of using a dielectric force to simulate terrestrial gravity. The effect of this dielectric force on the flow field is investigated as well as a parameter study of varying rotation rates and boundary temperatures. Among the effects noted are the production of larger velocities and enhanced reversals of radial temperature gradients for a body force generated by the electric field.

Macaraeg, M. G.↗
NASA NTRS1988

Modeling of combustion processes of stick propellants via combined Eulerian-Lagrangian approach

This research is motivated by the improved ballistic performance of large-caliber guns using stick propellant charges. A comprehensive theoretical model for predicting the flame spreading, combustion, and grain deformation phenomena of long, unslotted stick propellants is presented. The formulation is based upon a combined Eulerian-Lagrangian approach to simulate special characteristics of the two phase combustion process in a cartridge loaded with a bundle of sticks. The model considers five separate regions consisting of the internal perforation, the solid phase, the external interstitial gas phase, and two lumped parameter regions at either end of the stick bundle. For the external gas phase region, a set of transient one-dimensional fluid-dynamic equations using the Eulerian approach is obtained; governing equations for the stick propellants are formulated using the Lagrangian approach. The motion of a representative stick is derived by considering the forces acting on the entire propellant stick. The instantaneous temperature and stress fields in the stick propellant are modeled by considering the transient axisymmetric heat conduction equation and dynamic structural analysis.

Kuo, K. K.↗
NASA NTRS1992

Experimental determination of in situ utilization of lunar regolith for thermal energy storage

A Lunar Thermal Energy from Regolith (LUTHER) experiment has been designed and fabricated at the NASA Lewis Research Center to determine the feasibility of using lunar soil as thermal energy storage media. The experimental apparatus includes an alumina ceramic canister which contains simulated lunar regolith, a heater, nine heat shields, a heat transfer cold jacket, and 19 type-B platinum rhodium thermocouples. The simulated lunar regolith is a basalt that closely resembles the lunar basalt returned to earth by the Apollo missions. The experiment will test the effects of vacuum, particle size, and density on the thermophysical properties of the regolith, which include melt temperature, specific heat thermal conductivity, and latent heat of storage. Two separate tests, using two different heaters, will be performed to study the effect of heating the system using radiative and conductive heat transfer. A finite differencing SINDA model was developed at NASA Lewis Research Center to predict the performance of the LUTHER experiment. The code will predict the effects of vacuum, particle size, and density has on the heat transfer to the simulated regolith.

Richter, Scott W.↗
NASA NTRS1996

Experimental and Computational Investigations of Phase Change Thermal Energy Storage Canisters

Two sets of experimental data are examined in this paper, ground and space experiments, for cylindrical canisters with thermal energy storage applications. A 2-D computational model was developed for unsteady heat transfer (conduction and radiation) with phase-change. The radiation heat transfer employed a finite volume method. The following was found in this study: (1) Ground Experiments: the convection heat transfer is equally important to that of the radiation heat transfer; radiation heat transfer in the liquid is found to be more significant than that in the void; including the radiation heat transfer in the liquid resulted in lower temperatures (about 15 K) and increased the melting time (about 10 min.); generally, most of the heat flow takes place in the radial direction. (2) Space Experiments: radiation heat transfer in the void is found to be more significant than that in the liquid (exactly the opposite to the Ground Experiments); accordingly, the location and size of the void affects the performance considerably; including the radiation heat transfer in the void resulted in lower temperatures (about 40 K).

Ibrahim, Mounir↗
NASA NTRSDate not supplied

Comprehensive 3D Multiphysics Model on Electrochemical Recovery of O 2 from Metabolic CO 2 at the International Space Station (ISS)

The International Space Station (ISS) is presently equipped with an elaborate, heavy, and high-power consuming system that recovers approximately 50% of O 2 from metabolic CO 2 as part of the atmospheric revitalization (AR) at the ISS habitat. Future long-duration missions will require a sustainable and efficient system capable of yielding a minimum of 75% O 2 recovery to reach the self-sufficiency required for long space missions beyond earth’s low orbit. A Macrofluidic Electrochemical Reactor (MFECR) technology development effort is currently underway at NASA Marshall Space Flight Center (MSFC) to not only increase significantly current O 2 recovery efficiency, improving self-sufficiency on AR at the ISS habitat and future long missions, but also reduce the complexity of the system. The authors have developed and deployed a comprehensive 3D multiphysics model that thoroughly replicates the actual configuration and fluid/material domains of the MFECR. The coupled physics in this multiphysics model include multicomponent-multiphase electrochemical-driven reactions, non-ideal mass transport mechanism, free and porous flow, heat transfer, CO 2 solubility on alkaline electrolyte, water condensation on porous medium, and DC electrical current generation along with Joule heating effect. This model is aimed to conduct quantitive benchmark on three different MFECR’s layouts, one without serpentine paths (plain) and two with serpentines leading to four and twelve paths respectively. Once experimental data is generated via a test matrix of 200 tests, the model will be validated to conduct MFECR’s process optimization and revalidate the quantitive benchmark on three different MFECR’s layouts.

Jesus A. Dominguez↗
NASA NTRS1979

Confinement of hot, hard X-ray producing electrons in solar flares

Possible thermal models for solar, hard X-ray emission, consisting of small volumes in which the electrons are rapidly heated to 400 million K, are examined to determine under what conditions such models can be more efficient than nonthermal models. The analysis is restricted to one dimension by supposing that the hot electrons are confined in a flux tube and that conduction and convection act only along the magnetic field. A conduction front, thin in relation to other length scales involved, separates the hot electrons from the relatively cold plasma. The range of conduction-front velocity is studied by systematizing the present knowledge of heat conduction and applying it first to a simple model in which convection is neglected, and then to a detailed numerical model in which convection is included. Convection in which mass motion goes to zero at the conduction front does not lead to a change in the conduction-front velocity compared to conduction alone, but does constitute another nonradiative energy loss which reduces the source efficiency.

Smith, D. F.↗
NASA NTRS1985

The thermal structure of the dayside upper atmosphere of Venus above 125 km

A one-dimensional model of the Venus thermosphere has been constructed which includes computation of the heating efficiency of solar ultraviolet radiation, heat loss by radiation to space of infrared-active species, thermal transport by molecular and eddy conduction, and viscous dissipation. By comparing model predictions with results obtained from the Pioneer Venus Orbiter spacecraft, the results indicate that energy transport parameterized by eddy heat conduction plays a dominant role in determining thermospheric temperature. It is suggested that there exists a feedback mechanism linking heating and thermospheric circulation such that eddy cooling maintains an asymptotic temperature of about 300 K for both solar-maximum and solar-minimum conditions. The variation in thermospheric temperature with solar zenith angle, atomic oxygen-mixing ratio, rate of vibrational excitation of CO2 by ground-state O atoms, and the assumed transfer of O(1D) electronic energy to CO2 vibrational energy are also studied.

Hollenbach, D. J.↗
NASA NTRS1998

Numerical Modeling of Physical Vapor Transport in Contactless Crystal Growth Geometry

Growth from the vapor under conditions of limited contact with the walls of the growth ampoule is beneficial for the quality of the growing crystal due to reduced stress and contamination which may be caused by interactions with the growth container. The technique may be of a particular interest for studies on crystal growth under microgravity conditions: elimination of some factors affecting the crystal quality may make interpretation of space-conducted processes more conclusive and meaningful. For that reason, and as a part of our continuing studies on 'contactless' growth technique, we have developed a computational model of crystal growth process in such system. The theoretical model was built, and simulations were performed using the commercial computational fluid dynamics code, (CFD) ACE. The code uses an implicit finite volume formulation with a gray discrete ordinate method radiation model which accounts for the diffuse absorption and reflection of radiation throughout the furnace. The three-dimensional model computes the heat transfer through the crystal, quartz, and gas both inside and outside the ampoule, and mass transport from the source to the crystal and the sink. The heat transport mechanisms by conduction, natural convection, and radiation, and mass transport by diffusion and convection are modeled simultaneously and include the heat of the phase transition at the solid-vapor interfaces. As the thermal boundary condition, temperature profile along the walls of the furnace is used. For different thermal profiles and furnace and ampoule dimensions, the crystal growth rate and development of the crystal-vapor and source-vapor interfaces (change of the interface shape and location with time) are obtained. Super/under-saturation in the ampoule is determined and critical factors determining the 'contactless' growth conditions are identified and discussed. The relative importance of the ampoule dimensions and geometry, the furnace dimensions and its temperature, and the properties of the grown material are analyzed. The results of the simulations are compared with related experimental results on growth of CdTe, CdZnTe, ZnTe, PbTe, and PbSnTe crystals by this technique.

Palosz, W.↗
NASA NTRS1979

Thermal study of interface between the Orbiter cold plate and typical Shuttle spacecraft payload flight electronics

Spacelab provides a set of Freon line plumbing and cold plates for experiment equipments which are located in the Shuttle pallet and which need active thermal control. The reported study deals with the thermal problem of attaching a Command and Data Handling module with various electronic boxes whose combined footprints on the baseplate are much larger than the cold plate. A description of two modules and the cold plate assembly in the pallet is presented and a thermal model description is provided. The method employed in modeling heat pipes-honey-comb matrix is based upon an effective conductance between the heat pipe vapor and the walls of the heat pipe. The considered thermal models and a computer program are used to perform steady-state thermal analyses. The temperature gradients in the large module baseplate attached to the small cold plate are predicted as a function of the interface plate thickness.

Hwangbo, H.↗