Derivation of mechanistic critical heat flux model for water based on flow instabilities

Abstract

The critical heat flux (CHF) is a major parameter which determines the cooling performance and therefore the prediction of CHF with accuracy is of importance for the design and safety analysis of nuclear power plant (NPP). In this study, the mechanistic CHF model and correlation for water are derived based on flow excursion (or Ledinegg instability) criterion and the simplified two-phase homogeneous model. The relationship between CHF for the water and the principal parameters such as mass flux, heat of vaporization, heated length-to-diameter ratio, vapor-liquid density ratio and inlet subcooling is derived on the developed correlation. The developed CHF correlation predicts very well at the applicable ranges, 1 < P < 40 bar, 1,300 < G 27,00 kg/m 2s and inlet quality is less than −0.1. The overall mean ratio of predicted to experimental CHF value is 0.988 with standard deviation of 0.046.