Page:Journal of the American Society of Mechanical Engineers, Volume 33.pdf/664

48The specific weight of water vapor may also be given independent of the density as

$S=0.6221+0.001815{\sqrt {e}}+0.0000051{\sqrt {e^{3}}}$

Hence

$G={\frac {7000(0.6221e+0.00182{\sqrt {e^{3}}}+0.0000051{\sqrt {e^{5}}})}{P-e}}$

At atmospheric temperature the term $0.0000051{\sqrt {e^{5}}}$ is negligible. Hence

$G={\frac {7000(0.6221e+0.00182{\sqrt {e^{3}}})}{P-e}}$

Fig. 8.—Specific Weight of Steam.

CONSTRUCTIONS OF ADIABATIC SATURATION LINES

49As shown in Par. 30 any adiabatic change involving moisture content and temperature of air may be expressed by equating the change in total specific heat to the corresponding change in latent heat. It may also be expressed by equating the total heat contained in the air in the state resulting from adiabatic change. By either of these two methods, given in Appendix No. 4, the relations of formula [6] are established.

6

$r'(W'-W)=C_{pa}(t-t')+C_{ps}W(t-t')$

in which

$(t-t')$ = the true wet-bulb depression

$(W'-W)$ = the moisture absorbed per lb. of pure air when it is adiabatically saturated from an initial dry-bulb temperature $t_{o}$ and an initial moisture content $W$