CONTRIBUTION TO THE THEORY OF TWO-PHASE, ONE-COMPONENT CRITICAL FLOW

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Abstract
Equipment was built where critical-flow data above 100 psia were obtained and a theory developed that predicts the experimental values satisfactorily. Theoretical expressions for the specific volume, void fraction, and slip ratio for critical steam-water mixtures have been derived. Therefore, the first complete analytical solution was made possible for estimating the critical two-phase flow rate, including slip between the two phases. The pressure profiles for runs at critical flow were all characterized by extremely steep pressure gradients near the throat; however, the pressure gradients are definitely finite and approach absolute maximum values, these depending only upon critical flow rate and quality. Sonic velocities are not achieved in critical two-phase flow of steam--water mixtures. Therefore, the phenomenon of two-phase critical flow differs significantly from that of single-phase critical flow. A new theory has been postulated in an effort to explain the mechanism of two-phase critical flow. The geometry of the system to be investigated has apparently no effect on the critical-flow phenomenon for the diameters and lengths of pipes used in this work. The experimental data obtained compare favorably with previous investigations in the range of variables where such a comparison is possible. The Homogeneous Flow Model'' is found to bemore » unsatisfactory for all critical throat pressures and qualities examined. The assumption of no slip between the phases, therefore, can be said to be definitely incorrect. Since the theory presented describes the critical phenomenon satisfactorily for all pressures and qualities examined so far, and no parameters depending on experimental values are needed, the theory is believed to be highly valuable in determining the maximum discharge of steam--water mixtures from conduits and breaks'' in vessels and pipes. The applications are subjects of considerable concern in the evaluation of nuclear reactor accidents and containmen among others. (auth) « less

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