THERMAL RELAXATION IN HUMID AIR

A theoretical and experimental investigation of the molecular absorption process in air has been carried out with particular reference to the variation of Napier frequency (fmax) with water vapor concentration (hâ2). It turns out that the relationship between these two quantities is a quadratic only at very low humidities and that, over the rest of the humidity range, the general relationship derived here is best approximated by an equation of the form fmax = const hâ2x, where 1 < x < 2. Critical examination of previous theoretical relationships shows that the rate of resonant interchange of energy between oxygen and water vapor has been underestimated because of the quadratic approximation. Reassessment of this quantity on the basis of the analysis herein yields a more realistic value that is more consistent with previous experimental findings in oxygen and closer to what one would expect from theoretical calculations. Details are also given of a numerical method of calculating Napier frequency directly from measured values of molecular absorption. © 1969, Acoustical Society of America. All rights reserved.