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Abstract
Safety analyses of pressurized water reactors and boiling water reactors in the event of small-break loss-of-coolant accidents strongly depend on leakage rate predictions using two-phase critical flow models. The paper aims to revise the critical flow criterion and consider the nonequilibrium phenomena of critical flows in constructing a modified two-phase critical flow model. The model predictions exhibit strong similarities with the experimental values, with prediction deviations of 14.4% for mass fluxes and 19.3% for outlet pressure. The compiled code, according to the proposed model, can be exploited in pressure pipeline designs, providing the theoretical basis for leak-before-break analyses.
Nomenclature
| A = | = | cross-section area (m2) |
| D = | = | equivalent diameter (m) |
| G = | = | critical flow (kg∙m−2∙s−1) |
| h = | = | enthalpy (kJ∙kg−1) |
| L = | = | channel length (m) |
| N = | = | thermodynamic nonequilibrium constant |
| p = | = | pressure (MPa) |
| S = | = | slip ratio |
| T = | = | temperature (K) |
| u = | = | flow rate (m∙s−1) |
| x = | = | mass quality |
Greek
| α = | = | void fraction |
| ΔT = | = | subcooling (K) |
| ρ = | = | density (kg∙m−3) |
| υ = | = | specific volume (m2∙kg−1) |
Subscript
| c = | = | critical section |
| e = | = | equilibrium |
| g = | = | vapor |
| i = | = | entry |
| l = | = | liquid |
Acknowledgments
The authors appreciate the support from State Key Laboratory of Nuclear Power Safety Monitoring Technology and Equipment (number K-A2018.430) and National Natural Science Foundation (grant number 11675128) of China.