Contribution to report 'Critical flow phenomena in two-phase mixtures and their relationships to reactor safety' (for Geneva conference)

摘要

Normally, in the flow of a flashing liquid through a pipe, it is assumed that the location of the choking phenomenon, if it exists, is at the exist of the pipe. Experiments have indicated that thee are circumstances under which choking can occur at the entrance instead. These experiments were performed to study the flashing of initially-compressed water through short lengths of pipe with length/diameter ratios of up to 20. Entrance configurations considered included sharp and rounded transitions and conical passages of 20- and 45-degree tapers. Upstream pressure ranged from 115 to 1,800 psia and in all instances, the upstream pressures were much greater than the saturation values. In most cases, choking of the flow was incurred when the liquid entering the pipe was required to depressurize to the saturation pressure (or below) when accelerating through the reduction at the entrance. Axial pressure surveys demonstrated that the pressure at the entrance of the pipe during choked conditions was the saturation pressure. It remained at the saturation value regardless of upstream pressure and the pressure distribution along the remainder of the pipe.