A COMPARISON OF CRITICAL HEAT-FLUX IN TUBES AND ANNULI

This paper examines the differences in critical heat flux (CHF) between internally heated annuli and tubes, cooled by water, based on an 8 mm tube CHF look-up table as the reference. The quality, gap size and pressure were identified as the most important parameters to account for differences in CHF between concentric annuli and tubes. Eccentricity, void migration parameter gamma and quality caused the main differences in CHF between eccentric and concentric annuli. These parameters were used to develop CHF correlations for both types of annuli. The proposed correlations predict the CHF with an r.m.s. error of 9.26% for concentric annuli (based on 1547 CHF data points), and 11.6% for eccentric annuli (based on 331 CHF data points). These correlations predict the correct parametric and asymptotic trends, and are more accurate than other CHF prediction methods for annuli.