An electrical detector of condensation in high-velocity steam

Abstract

A new method has been developed for finding where condensation in a convergent-divergent steam nozzle commences. When a short length of fine wire, mounted on a rod, was traversed axially through the nozzle, it was found that its resistance altered sharply at a certain point. The position of this point agreed closely with that of a small sudden pressure rise in the nozzle, which an earlier investigation has shown to indicate the beginning of condensation of the supersaturated steam. The mean temperature of the wire upstream from this point was found (as predicted by Griffith's theory) to be nearly the same as that of the steam at entrance to the nozzle; it was greatly in excess of the temperature of the high-velocity steam passing the wire. The wire was heated electrically, and the Nusselt number of heat transfer to the steam was measured under the prevailing supersonic conditions. The Wilson line, showing the position of condensation on the Mollier diagram, was determined, and is compared with the line previously obtained for another nozzle of different shape.