Thermal-Relaxation Absorption in Carbon Dioxide/Water-Vapor Mixtures

Abstract

Sound-absorption and -dispersion measurements have been made using the tube method on CO2-H2O mixtures over the temperature range of 23°–195°C. A single relaxation time was found to describe adequately both the absorption and dispersion curves. The reciprocal of the relaxation time at each temperature was found to be linearly dependent on the concentration of H2O. The relaxation time τAB was calculated at each temperature, and τAB was found to increase as the temperature increased. A significant result is that log τAB exhibited no minimum value when plotted versus T−13, as has been previously reported by Eucken and Numann, but rather log τAB shows a linear decrease versus T−13. The number of collisions Z10(AB) necessary to deexcite the lowest vibrational mode of CO2 has been calculated from the measured relaxation time and is essentially temperature-independent. [This work was supported by the U. S. Office of Naval Research.]