Analysis of post-CHF swirl flow heat transfer

Abstract

A thermodynamic nonequilibrium model has been developed for a two-phase, vapor and liquid-drop, dispersed swirl flow in a vertical tube with a twisted-tape insert. The solution of the nonlinear differential equations proceeds from the critical heat flux location downstream through the post-CHF region. Wall temperature, superheat vapor temperature, heat transfer rates to the phases, and phase velocity distributions are predicted. Results were verified by comparison with experimental data from a heat exchanger application with high pressure (16.0 MPa) boiling water heated by a flowing liquid. The resulting low wall-superheat data used in this study were in the mass flux range of 910–1878 kg m −2 s −1 with tape-twist ratios of 2.51, 5.02 and 7.53 based on 180° of twist. Model predictions are presented for parameters not measured experimentally which lend insight into post-CHF heat transfer under swirl flow conditions.