Chapter 15, Problem 15.9P

Vapor sulfur hexafluoride SF₆ at pressures of about 1600 kPa is used as a dielectric in large primary circuit breakers for electric transmission systems. As liquids. SF₆ and H₂O are essentially immiscible, and one must therefore specify a low enough moisture content in the vapor SF₆ so that if condensation occurs in cold weather, a liquid water phase will not form first in the system. For a preliminary determination, assume the vapor phase can be treated as an ideal gas and prepare the phase diagram [like Fig. 12.18(a)] for $H_{2}O/S{F}_6(2)$ at 1600 kPa in the composition range up to 1000 parts per million of water (mole basis). The following approximate equations for vapor pressure are adequate:

$In{P}_1^{sat}/kPa=19.1478-\frac{5363.70}{T/K}$

$In{P}_2^{sat}/kPa=14.6511-\frac{2048.97}{T/K}$