NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Combined Heat Transfer in High-Porosity High-Temperature Fibrous Insulations: Theory and Experimental ValidationCombined radiation and conduction heat transfer through various high-temperature, high-porosity, unbonded (loose) fibrous insulations was modeled based on first principles. The diffusion approximation was used for modeling the radiation component of heat transfer in the optically thick insulations. The relevant parameters needed for the heat transfer model were derived from experimental data. Semi-empirical formulations were used to model the solid conduction contribution of heat transfer in fibrous insulations with the relevant parameters inferred from thermal conductivity measurements at cryogenic temperatures in a vacuum. The specific extinction coefficient for radiation heat transfer was obtained from high-temperature steady-state thermal measurements with large temperature gradients maintained across the sample thickness in a vacuum. Standard gas conduction modeling was used in the heat transfer formulation. This heat transfer modeling methodology was applied to silica, two types of alumina, and a zirconia-based fibrous insulation, and to a variation of opacified fibrous insulation (OFI). OFI is a class of insulations manufactured by embedding efficient ceramic opacifiers in various unbonded fibrous insulations to significantly attenuate the radiation component of heat transfer. The heat transfer modeling methodology was validated by comparison with more rigorous analytical solutions and with standard thermal conductivity measurements. The validated heat transfer model is applicable to various densities of these high-porosity insulations as long as the fiber properties are the same (index of refraction, size distribution, orientation, and length). Furthermore, the heat transfer data for these insulations can be obtained at any static pressure in any working gas environment without the need to perform tests in various gases at various pressures.
Document ID
20100024499
Acquisition Source
Langley Research Center
Document Type
Conference Paper
Authors
Daryabeigi, Kamran
(NASA Langley Research Center Hampton, VA, United States)
Cunnington, George R.
(Cunnington and Associates Palo Alto, CA, United States)
Miller, Steve D.
(Miller (S. D.) and Associates Flagstaff, AZ, United States)
Knutson, Jeffry R.
(NASA Langley Research Center Hampton, VA, United States)
Date Acquired
August 24, 2013
Publication Date
June 28, 2010
Subject Category
Mechanical Engineering
Report/Patent Number
AIAA Paper 2010-4660
NF1676L-9673
Meeting Information
Meeting: 10th AIAA/ASME Joint Thermophysics and Heat Transfer Conference
Location: Chicago, IL
Country: United States
Start Date: June 28, 2010
End Date: July 1, 2010
Sponsors: American Inst. of Aeronautics and Astronautics
Funding Number(s)
WBS: WBS 599489.02.07.07.02.12.01
Distribution Limits
Public
Copyright
Public Use Permitted.
No Preview Available