Critical heat flux for uniformly heated rod bundle under high-pressure, low-flow and mixed inlet conditions.

Abstract

Dryout experiments have been conducted in a 5×5 rod bundle 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) of a nuclear reactor. The experimental conditions cover ranges of pressure from 3 to 12 MPa, mass flux from 20 to 410 kg/m2.s and inlet quality from 0 4 to 0 9 The dryout data have been compared with several empirical critical heat flux (CHF) correlations that are commonly used to predict CHF behavior and with an equation derived on basis of a simple assumption. The Biasi correlation overpredicts considerably the CHF; in some cases, it overpredicts the CHF by a factor of 10 or 100. The Bowring correlation underpredicts the CHF to approximately 1/2. The Katto correlation performs relatively well in correlating the present dryout data. An equation derived on basis of a simple assumption that dryout occurs due to complete vaporization of liquid in a subchannel performs best among the correlat...