RESUMO
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
RESUMO
This note points out errors in the values of the third virial coefficients for pure water vapor which appeared in a 1967 paper by Hyland and Mason. The errors arose while converting from the units of Goff and of Keyes to the desired units of (liter/mole)2. The consequences of the errors are outlined, and it is shown that there is no effect on the primary results of the paper, namely, in the preferred values of the third interaction virial coefficient for air-water vapor mixtures, C aww .
RESUMO
The third interaction virial coefficient C aww for air-water vapor mixtures is estimated in the temperature range 0 to 100 °C, by means of an approximate method based on molecular association. The results are believed accurate to within a factor of two. The value of C aww can be combined with previous estimates of the other interaction coefficient C aaw and the values of the third virial coefficients of pure air and pure water vapor, to give a quantitative description of the equation of state of air-water vapor mixtures through the complete third virial coefficient. It is shown that the maximum total contribution from both C aww and C aaw to the compressibility factor is only of the order of parts in 104 up to 100 °C and 100 atmospheres total pressure. At -50 °C, it can be shown by extrapolation of C aww that the contribution of the C aww term to the compressibility factor is only on the order of parts in 1011.