Reduced pressure and fluid to fluid scaling laws for two-phase flow loop

Scaling criteria for a natural circulation loop under single-phase and two-phase to two-phase flow conditions are derived. The criteria include the effects of primary fluid properties so one can use for modeling a high-pressure water system by a low-pressure water system or by a different fluid system. In addition to the standard single-phase flow dimensionless groups, it is shown that the phase change, subcooling, drift-flux and Froude numbers are particularly important for a two-phase flow simulation. Based on the results obtained from the rigorous similarity analysis, practical applications for designing a scaled-down model are considered. Special emphasis is given on scaling at reduced pressure levels relative to a prototype system and fluid to fluid scaling. It is a challenging problem to design a scaled-down model with different fluid properties due to a large number of similarity groups to be matched between a model and a prototype. The present study demonstrates a new approach to this classical problem using the two-phase flow scaling criteria. It indicates that a real time scaling is not a practical solution, and a scaled-down model should have an accelerated (shortened) time scale. One of the most important tesults is the new scaling methodology for simulating pressure transients. It is obtained by considering the changes of the fluid property groups which appear within the two-phase similarity parameters and the single-phase to two-phase flow transition parameters. 11 refs., 11 figs