Diffusion coefficients of internal states for the calculation of thermal conductivity

✍ Scribed by John R. Ferron

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 809 KB
• Volume: 166
• Category: Article
• ISSN: 0378-4371
• DOI: 10.1016/0378-4371(90)90019-o

✦ Synopsis

In studies of vibrational relaxation of nitrous oxide and of carbon dioxide, diffusion coefficients of the vibrationally excited species (D,) have been measured as functions of temperature. These results are used here to estimate diffusion coefficients for rotational (D,,,) and vibrational energy (D,,,). The diffusivity of internal states (Dint), frequently applied in the calculation of thermal conductivity as a weighted, hyperbolic mean of D,,, and Dvi,, is compared with the same quantity inferred from experimental thermal conductivities. The mean value is accurate to at least 400 K for N,O and 800 K for CO,.

For other gases we use experimental thermal conductivities, along with D,,, and Dvi, for a correlation of D,. This permits evaluation of internal diffusivities of nonpolar, polyatomic gases for which a collision diameter is available. The potential well depth is not part of the estimate, and it appears that excited-state diffusivity is predominantly influenced by longrange forces.