Assessment of Critical Heat Flux correlations in narrow rectangular channels

Paper in proceeding, 2016

The aim of the work is to assess different CHF correlations when applied to vertical narrow rectangular channels with upward low-pressure water flow. This is a contribution to the improvement of the thermal-hydraulic modeling of the Jules Horowitz Reactor, which is a research reactor under construction at CEA-Cadarache (France). For this purpose, 46 CHF tests from the SULTAN-JHR experimental database were used. These experiments were performed at CEA-Grenoble in two vertical uniformly heated rectangular channels with gaps of 1.51 (SE3: 20 tests) and 2.16 mm (SE4: 26 tests). The experimental conditions ranged between 0.38 and 0.87 MPa for the outlet pressure, between 1200 and 6600 kg/m2/s for the mass flux, between 56.4 and 156.4 °C for the inlet liquid sub-cooling and between -0.01 and 0.12 for the outlet steam quality. Several models were tested. The Groeneveld look-up tables, which were developed mainly with experiments in pipes, significantly over-estimate the CHF. Furthermore, they fail to predict the decrease of the CHF with the reduction of the gap size. Doerffer’s modification of Groeneveld look-up table for internally heated annuli and the Sudo correlation for nuclear research reactors with plate-type fuel, give better results. In particular, Doerffer’s formula predicts the experimental data with a mean error of -10 % for SE4 and +17 % for SE3, while the Sudo relationship gives mean errors equal to -2.3 % and +32 %.