Abstract
1-dimensional critical flow model is efficient in nuclear safety analysis, but is not accurate for critical flow in crack, which could be simplified as slit with high length-width ratio. The aerosol source term in LBB monitoring requires precision on mass flux and pressure profile of critical flow in slit. The mass flux and pressure profile are critical for LBB monitoring.
Calculation of Delayed Equilibrium Model is compared with previous experiment on critical flow in rectangular slit. Delayed Equilibrium Model is accurate in calculating the mass flux for critical flow in slit, but the pressure greatly deviates. The maximum relative error of mass flux is lower than 25%, while the maximum relative error of critical pressure is lower than 110%.
By rearranging the empirical equation of metastable phase mass flow rate fraction gradient and two-phase friction coefficient multiplier, the effect of slit shape is added to Delayed Equilibrium Model. The pressure profile of critical flow in rectangular slit approaches the actual pressure profile, while the relative error of mass flux is kept at the level of original model. The maximum relative error of mass flux is lower than 30%, and the maximum relative error of critical pressure is lower than 45%.
Further research on general crack could start from the optimization of Delayed Equilibrium Model for critical flow in slit, with more bends and irregular, changing cross section shape. This may require better understanding of complex phenomena in critical flow.
