ANALYSIS OF POST-CHF SWIRL FLOW HEAT-TRANSFER

A thermodynamic nonequilibrium model has been developed for a two-phas e, vapor and liquid-drop, dispersed swirl flow in a vertical tube with a twisted-tape insert. The solution of the nonlinear differential equ ations proceeds from the critical heat flux location downstream throug h the post-CHF region. Wall temperature, superheat vapor temperature, heat transfer rates to the phases, and phase velocity distributions ar e predicted. Results were verified by comparison with experimental dat a from a heat exchanger application with high pressure (16.0 MPa) boil ing 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-degre es of twist. Model predictions are presented for parameters not measur ed experimentally which lend insight into post-CHF heat transfer under swirl flow conditions.