An Improved Theoretical Critical Heat Flux Model for Low-Quality Flow

Abstract

Based on the Helmholtz instability at the microlayer/vapor interface as a trigger condition for microlayer dryout, Lee and Mudawwar developed a mechanistic critical heat flux (CHF) model for subcooled flow boiling. An improved CHF model is implemented with more solid theoretical bases for subcooled and low-quality flow boiling under pressurized water reactor conditions. Comparisons between the predictions and experimental data show that the present model is more accurate than the well-known theoretical CHF model of Weisman and Pei and the empirical CHF correlations of W-3, Bowring, and Katto and Ohno for water flowing through uniformly heated round tubes within the applicable ranges. The applicability of the present model to rod bundles is also under investigation. Highly satisfactory results are obtained from the comparisons of predicted to observed bundle critical power.