Computational radiative heat transfer in homogeneous and nonhomogeneous nonscattering media.

摘要

A computational methodology was developed for calculating radiative heat transfer is gaseous nonhomogeneous nonscattering media with complex emission and absorption spectra. The technique can be used in both equilibrium and nonequilibrium situations.; Test cases applied to an Aeroassisted Orbital Transfer Vehicle (AOTV) were investigated, and results are presented herein. Nonequilibrium compositions and temperatures were taken from NASA-Langley three-dimensional hypersonic flowfield calculations that include real-gas effects and finite-rate chemical kinetics. This output was used as input to the NASA-Ames NEQAIR code to compute local values of spectral emission and absorption coefficients. For each spatial point considered, total (spectrally integrated) properties were computed, and these total properties were used to make the radiation calculations.; Use of total properties was found to yield remarkably accurate values of total intensity when compared to exact results for the cases examined in the AOTV flowfield. Results are presented for three markedly different lines of sight along with heat flux calculations for six receiver locations. Also an examination of using the technique in a differential formulation for the calculation of the gradient of intensity at a point is conducted. A more accurate intensity and gradient of intensity calculation is made assuming linear spatial variations of spectral emission and absorption coefficients.; The method is also compared to exact integration over the line structure of the 2143 cm{dollar}sp{lcub}-1{rcub}{dollar} band of CO for nonhomogeneous paths. These results are compared to calculations using the exponential wide-band model along with either the nonhomogeneous wide-band scaling or the transmission-path-adjustment algorithm.; Finally, three nonhomogeneous lines of sight in water vapor were investigated using the exponential wide-band model. Water vapor was chosen due to its five bands which are spread throughout the spectrum. Comparison is made between wide-band scaling and the transmission-path-adjustment method.