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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 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Transverse eV Ion Heating by Random Electric Field Fluctuations in the Plasmasphere

Charged particle acceleration in the Earth inner magnetosphere is believed to be mainly due to the local resonant wave-particle interaction or particle transport processes. However, the Van Allen Probes have recently provided interesting evidence of a relatively slow transverse heating of eV ions at distances about 2-3 Earth radii during quiet times. Waves that are able to resonantly interact with such very cold ions are generally rare in this region of space, called the plasmasphere. Thus, non-resonant wave-particle interactions are expected to play an important role in the observed ion heating. We demonstrate that stochastic heating by random transverse electric field fluctuations of whistler (and possibly electromagnetic ion cyclotron) waves could explain this weak and slow transverse heating of H+ and O+ ions in the inner magnetosphere. The essential element of the proposed model of ion heating is the presence of trains of random whistler (hiss) wave packets, with significant amplitude modulations produced by strong wave damping, rapid wave growth, or a superposition of wave packets of different frequencies, phases, and amplitudes. Such characteristics correspond to measured characteristics of hiss waves in this region. Using test particle simulations with typical wave and plasma parameters, we demonstrate that the corresponding stochastic transverse ion heating reaches 0.07-0.2 eV/h for protons and 0.007-0.015 eV/h for O+ ions. This global temperature increase of the Maxwellian ion population from an initial Ti approx. 0.3 eV could potentially explain the observations.

Artemyev, A. V.↗
NASA NTRS1973

Heat conduction errors and time lag in cryogenic thermometer installations

Installation practices are recommended that will increase rate of heat exchange between the thermometric sensing element and the cryogenic fluid, in addition to bringing about a reduction in the rate of undesired heat transfer to higher temperature objects. Formulas and numerical data are given that help to estimate the magnitude of heat conduction errors and of time lag in response.

Warshawsky, I.↗
NASA NTRS1988

Dewar to dewar model for superfluid helium transfer

A model has been developed to predict the flow of He II between a source and a receiving dewar. The model uses a finite difference aproximation to integrate the describing equations. The transfer path may contain porous plugs or mechanical pumps, heater sections, heat leaks, constrictions due to valves, and bends. These line elements may occur in any order and in any quantity. The line elements are easily reconfigured by changing the input data. The input consists of the number of finite element cells, the pressure in each dewar, the heat input to each section and the dimensions of each section. The output is the temperature, pressure, flow rate, velocities and heat flux in each section. An internal reference table provides the properties of He II. The model is programmed for a LOTUS work sheet. It converges rapidly and usually requires 10 to 15 iterations. For most applications an iteration takes 30 s on an AT. The predictions agree well with experimental data.

Snyder, H. A.↗
NASA NTRS1977

Calculations of the moon's thermal history at different concentrations of radioactive elements, taking into account differentiation on melting

Calculations of the thermal history of the moon were done by solving the thermal conductivity equation for the case in which the heat sources are the long lived radioactive elements Th, U, and K-40. The concentrations of these elements were adjusted to give 4 variations of heat flow. Calculations indicated that the moon's interior was heated to melting during the first 0.7 to 2.3 x 10 to the 9th power years. The maximum fusion involved practically the entire moon to a distance from 15 to 45 km beneath the surface, and started 3.5 to 4.0 x 10 to the 9th power years ago, or 2.5 x 3.0 x 10 to the 9th power years ago and continued for 1 to 2 x 10 to the 9th power years. The moon today is cooling. The current thickness of the solid crust is from 150 to 200 km and the heat flow exceeds the stationary value 1.5 fold.

Ornatskaya, O. I.↗
NASA NTRS1972

Structural-Thermal-Optical Program (STOP)

A structural thermal optical computer program is developed which uses a finite element approach and applies the Ritz method for solving heat transfer problems. Temperatures are represented at the vertices of each element and the displacements which yield deformations at any point of the heated surface are interpolated through grid points.

Lee, H. P.↗
DOE OSTI2017

Entrance-length dendritic plate heat exchangers

We explore the idea that the highest heat transfer rate between two fluids in a given volume is achieved when plate channel lengths are given by the thermal entrance length, i.e., when the thermal boundary layers meet at the exit of each channel. The overall design can be thought of an elemental construct of a dendritic heat exchanger, which consists of two tree-shaped streams arranged in cross flow. Every channel is as long as the thermal entrance length of the developing flow that resides in that channel. The results indicate that the overall design will change with the total volume and total number of channels. We found that the lengths of the surfaces swept in cross flow would have to decrease sizably as number of channels increases, while exhibiting mild decreases as total volume increases. The aspect ratio of each surface swept by fluid in cross flow should be approximately square, independent of total number of channels and volume. We also found that the minimum pumping power decreases sensibly as the total number of channels and the volume increase. FurtherThe maximized heat transfer rate per unit volume increases sharply as the total volume decreases, in agreement with the natural evolution toward miniaturization in technology.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2019

MEDLI2 Flight Heat Flux Sensor Environment and Planetary Protection Testing

Mars 2020 will fly the Mars Entry, Descent, and Landing Instrumentation II (MEDLI2) sensor suite consisting of a total of seventeen instrumented thermocouple sensor plugs, eight pressure transducers, two total heat flux sensors, and one radiometer embedded in the thermal protection system (TPS). Of the MEDLI2 instrumentation, eleven instrumented thermocouple plugs and seven pressure transducers will be installed on the heatshield of the Mars 2020 vehicle while the rest will be installed on the backshell. The goal of the MEDLI2 instrumentation is to directly inform the large performance uncertainties that contribute to the design and validation of a Mars entry system. A better understanding of the entry environment and TPS performance could lead to reduced design margins enabling greater payload mass-fraction and smaller landing ellipses. The MEDLI2 total heat flux sensors and radiometer are new instruments that were not flown on the Mars Science Laboratory mission. These sensors directly measure the surface heat flux and radiation at specific backshell locations. The total heat flux sensors use a Schmidt-Boelter sensing element. The radiometer version uses a sapphire window placed over the Schmidt-Boelter sensing element to separate the radiative component of the total heat flux. MEDLI2 recently planned and executed protoflight environmental testing as well planetary protection measures on the flight and flight-spare total heat flux sensors and radiometers. This testing is required to provide confidence in the performance of the flight-lot sensors when exposed to flight-like environments, and to reduce the risk of biological contamination on the planet of Mars with microbes from Earth.

MEDLI2 FLIGHT HEAT FLUX SENSOR ENVIRONMENT AND PLA↗
NASA NTRS2009

Thermal Transport Model for Heat Sink Design

A document discusses the development of a finite element model for describing thermal transport through microcalorimeter arrays in order to assist in heat-sinking design. A fabricated multi-absorber transition edge sensor (PoST) was designed in order to reduce device wiring density by a factor of four. The finite element model consists of breaking the microcalorimeter array into separate elements, including the transition edge sensor (TES) and the silicon substrate on which the sensor is deposited. Each element is then broken up into subelements, whose surface area subtends 10 10 microns. The heat capacity per unit temperature, thermal conductance, and thermal diffusivity of each subelement are the model inputs, as are the temperatures of each subelement. Numerical integration using the Finite in Time Centered in Space algorithm of the thermal diffusion equation is then performed in order to obtain a temporal evolution of the subelement temperature. Thermal transport across interfaces is modeled using a thermal boundary resistance obtained using the acoustic mismatch model. The document concludes with a discussion of the PoST fabrication. PoSTs are novel because they enable incident x-ray position sensitivity with good energy resolution and low wiring density.

Chervenak, James A.↗
NASA NTRS1986

Design of an advanced two-phase capillary cold plate

The functional principles and implementation of capillary pumped loop (CPL) two phase heat transport system for various elements of the Space Station program are described. Circulation of the working fluid by the surface-tension forces in a fine-pore capillary wick is the core principle of CPL systems. The liquid, usually NH3 at the moment, is changed into a vapor by heat absorption at one end of the loop, and the vapor is carrried back along the wick by the surface tension within the wick. NASA specifications and the results of mechanical and thermal tests for prototype cold plate and the capillary pump designs are outlined. The CPL is targeted for installation on free-flying platforms, attached payloads, and power subsystem thermal control systems.

Chalmers, D. R.↗
NASA NTRS1950

Instrument for measuring the wall shearing stress of turbulent boundary layers

It is shown that at a smooth wall in a turbulent boundary layer the velocity profile next to the wall is dependent, aside from the material constants of the flowing medium, only on the shearing stress transmitted to the wall, even with pressure rise or with pressure drop. Consequently, the heat transfer of a small element that is built into the wall and has a higher temperature than that of the flowing medium is a measure of the wall shearing stress. Theoretical considerations indicate that the wall shearing stress of the boundary layer can be defined by means of a heat-transfer measurement with an instrument mounted in the wall. Such an instrument is described. The calibration curve and its directional sensitivity curve are indicated. It permits the determination of the wall shearing stress in magnitude and direction.

BOUNDARY LAYER, TURBULENT↗
DOE OSTI2018

The Higgs Factory muon collider superconducting magnets and their protection against beam decay radiation

We report a low-energy medium-luminosity Muon Collider (MC) is being studied as a possible Higgs Factory (HF). Electrons from muon decays will deposit more than 300 kW in superconducting (SC) magnets of the HF collider ring. This imposes significant challenges to SC magnets used in the HF storage ring (SR) and interaction regions (IR). Conceptual designs of SC dipole and quadrupole magnets are described which provide high operating gradient and field in a large aperture to accommodate the large size of muon beams (due to low β*), as well as a cooling system to intercept the large heat deposition from the showers induced by decay electrons. The distribution of heat deposition in the main elements of HF SR lattice requires large-aperture magnets to accommodate thick high-Z absorbers to protect the SC coils. Based on the developed MARS15 model and intensive simulations, a sophisticated protection system from radiation was designed for the collider SR and IR to bring the peak power density in the SC coils well below the quench limit and reduce the dynamic heat deposition in the cold mass of SC magnets by a factor of 100. The radiation protection system consists of tight tungsten masks in the magnet interconnect regions and elliptical tungsten liners in the magnet aperture optimized for each magnet. Lastly, these elements reduce also the background particle fluxes in the collider detector.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Evaluation of Additively Manufactured Monolithic SiC and SiC Ceramic Matrix Composites for CSP- Fabrication and Testing of Receiver Design Feature Specimens in a Simulating Lab Test via Laser Heating

Critical to the creation of a multi-component SiC receiver design concept capable of meeting the SETO CST cost goal objectives of <$150/kWth is the optimal utilization of material for solar absorption and heat transfer to transport fluid. This is to maximize the solar-thermal efficiency in the techno-economic analysis of derived use case. As a first step in preparation of sub-component design for on-sun test evaluations we use different proposed SiC absorber element in a customized laser heat flux test to assess an effective heat transfer coefficient characteristic of the design. The test results are analyzed to extract the effective heat transfer coefficient, thus enable optimization of the geometry of receiver components for heat transfer, efficiency attributes and the thermo-structural management of the components. High intensity CO2 laser is used in combination with air flow through the test specimen to assess the effective heat transfer coefficient under heat flux conditions corresponding to high solar concentrations in the range of 1000-2000 suns.

14 SOLAR ENERGY↗
DOE OSTI2018

Estimates of Equivalent Heat Conductivity Coefficients of Carbon Nanotubes

We have obtained estimates of equivalent heat conductivity coefficients of nanostructured elements on the basis of the constructed mathematical model of the thermal energy transfer in a single-layer and a multilayer nanotube surrounded by a homogeneous material in the composite matrix. The values of such coefficients permit conditional replacement of nanotubes by solid anisotropic fibers, which makes it possible, in predicting the effective heat conductivity coefficient of a composite modified by carbon nanotubes, to use the known methods developed in detail to fit fibrous composites.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2017

A novel approach for reducing toxic emissions during high temperature processing of electronic waste

Highlights: • Volatile heavy metals are generally present in electronic waste constituents. • Potentially toxic elements released during e-waste heat treatment. • Metal particulates/fumes in outgoing gases were removed by alumina adsorbent. • Pb, Sn, Cu and Zn particulates were successfully captured by alumina. •Toxicity of emissions from e-waste was reduced significantly in this approach. - Abstract: A novel approach is presented to capture some of the potentially toxic elements (PTEs), other particulates and emissions during the heat treatment of e-waste using alumina adsorbents. Waste PCBs from mobile phones were mechanically crushed to sizes less than 1 mm; their thermal degradation was investigated using thermo-gravimetric analysis. Observed weight loss was attributed to the degradation of polymers and the vaporization of organic constituents and volatile metals. The sample assembly containing PCB powder and adsorbent was heat treated at 600 °C for times ranging between 10 and 30 min with air, nitrogen and argon as carrier gases. Weight gains up to ∼17% were recorded in the adsorbent thereby indicating the capture of significant amounts of particulates. The highest level of adsorption was observed in N{sub 2} atmosphere for small particle sizes of alumina. SEM/EDS results on the adsorbent indicated the presence of Cu, Pb, Si, Mg and C. These studies were supplemented with ICP-OES analysis to determine the extent of various species captured as a function of operating parameters. This innovative, low-cost approach has the potential for utilization in the informal sector and/or developing countries, and could play a significant role in reducing toxic emissions from e-waste processing towards environmentally safe limits.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Hermeticity of SiC/SiC composite and monolithic SiC tubes irradiated under radial high-heat flux

Demonstration of hermetic SiC fiber–reinforced SiC matrix composite cladding under normal operating environments has been identified as one of the most critical feasibility issues for accident-tolerant fuel cladding in light-water reactors. This study provides critical experimental data needed for understanding the effects of irradiation on hermeticity. SiC composite and monolithic tubes were neutron-irradiated to 2 displacements per atom with and without a nominal radial heat flux of 0.6 MW/m2 to produce a simulated in-pile stress state for the normal operation of a light-water reactor. The through-thickness temperature gradient under irradiation results in a gradient in swelling, which causes a significant stress buildup. Such irradiation-induced stress was modeled using a commercial finite element analysis code. The radial heat flux–irradiation synergism was experimentally investigated by constructing a special irradiation capsule and evaluating the helium hermeticity of the specimens. The simulated stress state exhibited a near equi-biaxial tensile axial and hoop stress of ~150 MPa at the inner surface of the SiC composite tube. This stress level is potentially beyond the matrix cracking stress. Degradation of hermeticity of the SiC composite tubes was observed after irradiation, indicating irradiation-induced cracking, whereas the irradiated monolithic SiC tubes remained hermetic. In conclusion, the results indicate that loss of hermeticity caused by radiation-induced microcracking is a potential issue for SiC composite cladding, depending on the magnitude of the temperature gradients. Coating the outer surface of the cladding was identified as a mitigation strategy that might overcome the cracking issue.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Thermostructural Behavior of a Hypersonic Aircraft Sandwich Panel Subjected to Heating on One Side

Thermostructural analysis was performed on a heated titanium honeycomb-core sandwich panel. The sandwich panel was supported at its four edges with spar-like substructures that acted as heat sinks, which are generally not considered in the classical analysis. One side of the panel was heated to high temperature to simulate aerodynamic heating during hypersonic flight. Two types of surface heating were considered: (1) flat-temperature profile, which ignores the effect of edge heat sinks, and (2) dome-shaped-temperature profile, which approximates the actual surface temperature distribution associated with the existence of edge heat sinks. The finite-element method was used to calculate the deformation field and thermal stress distributions in the face sheets and core of the sandwich panel. The detailed thermal stress distributions in the sandwich panel are presented, and critical stress regions are identified. The study shows how the magnitudes of those critical stresses and their locations change with different heating and edge conditions. This technical report presents comprehensive, three-dimensional graphical displays of thermal stress distributions in every part of a titanium honeycomb-core sandwich panel subjected to hypersonic heating on one side. The plots offer quick visualization of the structural response of the panel and are very useful for hot structures designers to identify the critical stress regions.

Ko, William L.↗
DOE OSTI2017

Design and optimization of 3D printed air-cooled heat sinks based on genetic algorithms

Enhancing power density and reliability of powerelectronics is extremely important in power electronicsapplications. One of the key challenges in the design process isto design the optimum heat sink. In this paper, an algorithm isproposed to design air-cooled heat sinks using genetic algorithm(GA) and finite element analysis (FEA) simulations. While theGA generates a population of candidate heat sinks in eachiteration, FEA simulations are used to evaluate the fitnessfunction of each. The fitness function considered in this paper isthe maximum junction temperature of the semiconductordevices. With an approach that prefers “survival of the fittest”,a heat sink providing better performance than the conventionalheat sinks is obtained. The simulation and experimentalevaluations of the optimized air-cooled heat sink are alsoincluded in the paper.

Wu, Tong↗