A Correlation for the Second Interaction Virial Coefficients and Enhancement Factors for Moist Air.

Experimental measurements of the enhancement factors for mixtures of water vapor and CO2-free air have been made at -20, -10, and +70 °C. The results, coupled with previous experimental enhancement data, have been used to calculate the second interaction virial coefficients, B aw , for water vapor air mixtures from -50 to +90 °C. Within this temperature range, an error analysis shows that the uncertainties in B aw are between 6 and 10 percent. The calculated B aw · values are used in deriving enhancement factors at 10 °C intervals for -50<t<90 °C, at varying pressure intervals from 0.25 to 100 bar. The associated uncertainties are shown as a function of pressure and temperature. The enhancement factors are extrapolated to -80 °C.