Normal Spectral Emission From Nonhomogeneous Mixtures of CO₂ Gas and Al₂O₃ Particulate

Measurements of spectral, normal intensity, accounting for nongray banded emission from CO₂ gas and the influence of a highly scattering particulate, Al₂O₃, are presented. Detailed specifications of the temperatures, particle and gas properties, optical depths, and experimental uncertainties are given. The average temperatures are in the range 445 K to 600 K, pressures are approximately 1 atm, the layer depth is 0.5 cm, and particle optical depths are in the range 0 to 3. The intensity emitted from the medium is reported over a wavelength range of about 4.0 μm to 4.7 μm. Since the particle is virtually nonemitting, no continuum emission outside the 4.3 μm CO₂ band is detected. The effect of the particle is seen in the spectrally dependent and extinction coefficient dependent changes in the band structure when scattering is present. Modeling of the nonisothermal temperature distribution of the layer emerges as a critical factor in determining the magnitude of the emitted intensity. Uncertainty in the magnitude of the temperature accounts for most of the estimated uncertainty in the spectral intensity. A comparison of the experimental band intensities with values computed using a nonhomogeneous scattering model (which rigorously incorporates wide-band modeling) indicates excellent agreement for most runs.