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  • THERMODYNAMICS AND COMBUSTION  (9)
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  • 1
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    Thermal shielding by subliming volume reflectors in convective and intense radiative environments. (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The behavior of dielectric materials having densely packed internal scattering centers subject to extreme convective and radiative environments is analyzed. Experiments have shown that these materials act as volume reflectors of incident radiation even when the exposed surface is being eroded by thermochemical ablation. The analysis was applied to interpret experiments of subliming Teflon models exposed to combined radiative and convective fluxes up to 1.7 kW/sq cm for several seconds. Results show that, although the exposed surface receded at an apparently steady rate, the internal temperature climbed continually, due to internal absorption of radiation and would have caused failure internally if the test duration were extended a few seconds. Thus, performance is time-limited by the internal absorption coefficient. Results were obtained for larger configurations and other materials. Typically, Teflon shells may withstand radiant fluxes up to 20 kW/sq cm for about 5 sec and fritted quartz up to 50 kW/sq cm for about 8 sec (corresponding to the Jupiter entry).
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA Journal; 11; July 197
    Format: text
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  • 2
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    Unsteady, combined radiation and conduction in an absorbing, scattering, and emitting medium. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The transient cooldown of a gray, absorbing, isotropic scattering, emitting, and conducting medium bounded by gray, diffusely emitting and reflecting parallel plates is considered. Numerical solutions are obtained for the initial boundary-value problem with a discontinuous decrease in temperature at one boundary. The quasi-steady equation of radiative transfer is solved using Gaussian quadrature and a matrix eigenvector technique together with explicit numerical solution of the unsteady energy equation. Temperature and energy flux distributions are presented for variations of optical thickness, boundary emissivity, albedo, and conduction-radiation parameter.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: ASME PAPER 73-HT-J
    Format: text
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  • 3
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    Unsteady temperature distribution in volume reflectors (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The development of unsteady temperature distributions in semitransparent scattering materials under the influence of arbitrary incident radiative flux with other than specified temperature boundary conditions is considered. Specifically, such a problem is considered for an approximate radiative transfer model which allows analytic solutions. The model represents the unsteady, one-dimensional, radiative heating of a weakly absorbing, semitransparent medium with specified conductive heat flux at one boundary. The radiation field is modeled using an approximation to the radiative heat flux obtained by solution of the Kubelka-Munk differential equations.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA Journal; 12; May 1974
    Format: text
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  • 4
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    Reflectance and unsteady temperature distribution of diffuse reflectors (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The applicability of a previously derived solution of the Kubelka-Munk differential equations for the reflectance of an absorbing and scattering material for the case of a zero absorption coefficient to the description of the reflectance of a weakly absorbing, highly scattering material is examined. A solution for the transient heating of a one-dimensional volume reflector is obtained, and the error incurred in the use of the zero absorption coefficient solution is assessed for early times appropriate to the entry heat protection system application. It is found that the small difference in reflectance causes a significant difference in internal temperature.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA Journal; 11; Dec. 197
    Format: text
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  • 5
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    Approximate temperature distribution for a diffuse, highly reflecting material. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The application of a 'two-flux' technique is considered for determining the reflective characteristics and approximate temperature distribution in highly backscattering materials characterized by a very small absorption coefficient. With respect to the transmitted internal radiation fields, the internal radiative emission is assumed to be negligible. A comparison of theory and experiment is presented.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: AIAA Journal; 10; Sept
    Format: text
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  • 6
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    An approximate analysis of the effects of nitrogen injection into the boundary layer on a graphite surface in a high-temperature dissociated airflow (1967)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Nitrogen injection effects on boundary layer of graphite surface in high-temperature dissociated airflow
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-TN-D-4060
    Format: application/pdf
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  • 7
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    Heat shield Patent (1964)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Compact heat shielding for interplanetary space vehicles
    Keywords: THERMODYNAMICS AND COMBUSTION
    Format: application/pdf
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  • 8
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    Energy transfer in volume-reflecting heat shields (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An approximate analytic solution is provided for the unsteady radiative heating of a highly scattering medium under constant heat flux boundary conditions. The accuracy of the method in representing the reflectance, radiative flux, and radiative flux divergence of the materials was also explored, as was the influence of anistropic scattering on these parameters.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-140690
    Format: application/pdf
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  • 9
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    Energy transfer in volume-reflecting heat shields (1974)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An approximate analysis of radiative transfer in highly scattering materials was developed based on the Kubelka-Munk differential equations--a set of two differential equations representing the spatial rate of change of radiative half-fluxes within the scattering media. These approximate solutions of the Kubelka-Munk equations together with analytic solutions for the steady state temperature distribution for two types of boundary conditions are given. These solutions show the influence of back surface reflectance, scattering power, incident radiative flux parameter and boundary conductive flux parameter on overall reflectance and temperature distributions. This radiation field analysis, adapted to spherical geometry, was applied to the evaluation of the thermal performance of teflon and fritted quartz as heat protection materials for entry into the atmosphere of Jupiter.
    Keywords: THERMODYNAMICS AND COMBUSTION
    Type: NASA-CR-139659
    Format: application/pdf
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