Implanting the heat transfer package of COBRA-TF into TRAC

Abstract

The simplified TRAC-PF1 code is modified by replacing the heat transfer package of TRAC-PF1 with that of COBRA-TF. In the heat transfer package of COBRA-TF, the critical heat flux is estimated using Griffith``s modification of the Zuber equation or the Biasi correlation according to the mass flux. COBRA-TF has a strong point in calculating the post-CHF phenomena because it uses droplet information acquired from the field equation. In this heat transfer regime, it uses the correlation of dispersed flow film boiling (DFFB) or inverted annular film boiling (IAFB) according to the void fraction. The validation of the modified code is performed using the experimental data of Lehigh University. The wall temperature and the vapor temperature profile through the whole heat transfer regime are acquired using both the revised code and TRAC-PF1. The predictions of the wall temperature and the vapor temperature are in better agreement with the experimental data than those by TRAC-PF1. It turns out that the droplets play a very essential role in governing post-CHF heat transfer.