Prediction of critical heat flux in bundles using tube look-up table.

Abstract

An extensive and systematic literature review on the effect of parameters and geometry on the Critical Heat Flux (CHF) is performed. This review covers most of the flow geometries that have been previously investigated such as tubes, concentric annuli and bundles. Each of the above geometries is studied individually. The following parameters are found to have a strong effect on CHF in bundles: (1) exit quality, (2) pressure, (3) hydraulic-equivalent diameter, (4) heated-equivalent diameter, (5) cold wall, (6) element spacing (spacers), (7) enthalpy or quality imbalance, (8) axial heat flux distribution, (9) radial heat flux distribution. It is found that some of the geometric effects on CHF depend on the flow conditions and the CHF type (six types of CHF have been identified for convective boiling). For each geometry the parametric trends are discussed, a review of the available prediction methods, including CHF correlations and models, is conducted, and the mechanism of CHF in each geometry is described. The following trends of CHF in bundles are identified in this study: (i) in general the CHF in bundles is lower than that in tubes, especially for high quality; (ii) the geometry effect is the most important factor in bundles. Based on the observed trends, CHF correction factors are derived for bundles. Finally, a CHF prediction method for bundles based on the correction factors with the AECL-UO lookup table as a reference is proposed.