Coupled dielectric and thermodynamic considerations for the design of vaporization-cooled electrical systems

Abstract

This paper develops the formulation of Paschen's law for the case of a 2 component non-isothermal system. In particular we analyze a system in which component separation is possible in that the components form a binary mixture of a condensable vapor and a noncondensable gas. In the present case the extent of component separation, under operating conditions, is such that the noncondensable gas is removed from the stressed zone so that the ultimate dielectric protection is determined not by the sum of the individual sparking potentials, but by one of them at a density determined by thermodynamic considerations. Thermodynamic equations are given which are sufficient for the design of such a system. It is shown that system operating temperature, pressure and ultimate dielectric strength are uniquely determined by system geometry and the amount of noncondensable gas contained. The system discussed permits high dielectric strength at low temperatures while preventing great pressures at high system temperatures. The analysis includes the effect of gas—liquid solubility on final operating pressure and temperature.