Critical Heat Flux for Annulus under High-Pressure, Low-Flow and Mixed Inlet Conditions

摘要

Dryout experiments of water have been conducted in an annulus with inside heating (heat flux from inner wall only) under high-pressure, low-flow and mixed inlet conditions which are of importance in the core thermal-hydraulic behavior during a loss-of-coolant accident (LOCA) and also partially during an anticipated transient without scram (ATWS) of a nuclear reactor. The experimental conditions have covered ranges of pressure of 3 MPa, mass flux from 105 to 320 kg/m2-s and inlet quality from 0.15 to 0.90. The dryout data have been compared with several existing empirical critical heat flux (CHF) correlations and a new correlation. The Katto correlation predicts best the CHF among the existing correlations examined. However, even the Katto correlation overpredicts the CHF by factors up to 2 at about 1/6 data points of the present dryout data. The present dryout data are divided into two groups (regions) according to the value of a non-dimensional number lbo/dhe, where lbo is the assumed boiling length and dhe the heated equivalent diameter. A new correlation covering both the regions has been developed by correlating the present dryout data in terms of two non-dimensional numbers. The new correlation performs best among the correlations examined in predicting the present dryout data.