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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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Thermal conductivity measurement of multilayer insulation material used in Gemini extravehicular space suit
Rotational relaxation and the relation between thermal conductivity and viscosity for some nonpolar polyatomic gases
Mutual diffusion coefficients of two gases predicted from temperature derivative obtained by thermal conductivity formula
Thermal conductivity of equimolar water-heavy water mixture considered in reply to comment of Spinner
High temperature insulating cermet seal for thermionic diodes noting high shock resistance and thermal conductance
The microstructure and surface chemistry of eight low thermal conductivity (LTC) PAN-based carbon fibers were determined and compared with PAN-based fibers heat treated to higher temperatures. Based on wide-angle x ray diffraction, the LTC PAN fibers all appear to have a similar turbostratic structure with large 002 d-spacings, small crystallite sizes, and moderate preferred orientation. Limited small-angle x ray scattering (SAXS) results indicate that, with the exception of LTC fibers made by BASF, the LTC fibers do not have well developed pores. Transmission electron microscopy shows that the texture of the two LTC PAN-based fibers studied (Amoco T350/23X and /25X) consists of multiple sets of parallel, wavy, bent layers that interweave with each other forming a complex three dimensional network oriented randomly around the fiber axis. X ray photoelectron spectroscopy (XPS) analysis finds correlations between heat treated temperatures and the surface composition chemistry of the carbon fiber samples.
An accurate estimation of the effective thermal conductivity of various insulation materials is essential in the evaluation of heat leak and boil-off rate from liquid hydrogen storage tanks. In this work, we review the existing experimental data and various proposed correlations for predicting the effective conductivity of insulation systems consisting of powders, foams, fibrous materials, and multilayer systems. We also propose a first principles-based correlation that may be used to estimate the dependence of the effective conductivity as a function of temperature, interstitial gas composition, pressure, and structural properties of the material. We validate the proposed correlation using available experimental data for some common insulation materials. Further improvements and testing of the proposed correlation using laboratory scale data obtained using potential LH 2 tank insulation materials are also discussed.
The key to improving the figure of merit of thermoelectric alloys in the temperature range of 300-1000 C is to reduce the thermal conductivity.
Charting and understanding lattice thermal conductivity of inorganic materials and discovery of REX materials for thermoelectrics.
Apparatus for measurement of thermal conductivity of powders in vacuum from 120 to 350 deg. k.
Ion energy balance equation analyzed in study of thermal conduction and ion temperatures in ionosphere
High thermal conductivity polymeric materials for spacecraft applications using phenyl compounds
Hydrogen, nitrogen and argon electrical and thermal conductivity measured at high temperature using electric arc as plasma source
Thermal conductivity of particulate basalt as function of density in simulated lunar and Martian environments, noting temperature and pressure effects
Closed cell polyurethane foam for cryogenic insulation, determining thermal conductivity and net heat flow by analytical model and test
Anomalous behavior model for prediction of thermal conductivity of fluids in critical region
Construction details, error analysis, and typical data for a rapid comparative device for thermal conductivity measurements are presented. The apparatus consists of a comparative cut-bar arrangement contained in a bell-jar. The cylinder shaped specimen is placed between two ARMCO-iron meter bars of the same diameter. The upper bar is equipped with a heater, while the lower one is terminated in a heat sink. The temperature gradient along the bars is measured with a series of copper/constantan microthermocouples, spot welded to them. The assembly is held together by loading the bars to a desired pressure, via a pneumatic cylinder. Contact resistance at the boundaries between the specimen and the meter bars is minimized by using a Hg/In/Ga alloy film at the interface and sufficient loading force. The gradients determined for the meter bars then may be extrapolated to the boundaries yielding the temperature drop along the specimen. Using two different length specimens, the magnitude of the temperature drop across the interface can be computed, or the true gradient along the specimen can be obtained from the difference in overall temperature drops and lengths.
Thermal conductivity measurements of particulate materials in vacuum are presented in summary. Particulate basalt and soda lime glass beads of various size ranges were used as samples. The differentiated line heat source method was used for the measurements. A comprehensive table is shown giving all pertinent experimental conditions. Least-squares curve fits to the data are presented.