Development and analysis of a novel scaling methodology for stability appraisal of supercritical flow channels

The prospect of achieving higher thermal efficiency with a simpler plant design projects a Supercritical water reactor as a better futuristic option compared to its boiling water counterpart. However, performing lab-scale experiments with supercritical water, particularly for appraisal of stability performance, is an arduous task, considering the level of pressure and temperature involved. That necessitates scaling analysis for the development of reduced-scale models to simulate true-scale prototypes under lab-level constraints. The present study, therefore, attempts to develop a scaling methodology focused on stability analysis and to identify a less-restrictive model fluid, while proposing generalized scaling rules preserving the phenomenological physics. US reference design of SCWR is selected as the prototype. Four characterizing dimensionless groups are recognized from the non-dimensional conservation equations under imposed pressure boundary conditions, while the system pressure for the model fluid is identified noting the region of similarity on the plane of non-dimensional density and non-dimensional pressure. A two-zone lumped parameter model is developed encompassing the thermal-hydraulic, fuel dynamics and power dynamics equations, which are subsequently employed for linear stability analysis and also for transient simulations. Both approach produced identical stability maps, leading to a generalized representation. R134a is concluded to be the most suitable model fluid from both the power and pressure points of view.