Evaluation of Various Correlations for Direct-Contact Heat Transfer in Dispersed Flow Film Boiling Using the DRACCAR Code
Résumé
Following the core uncovery after a hypothetical loss of primary coolant accident (LOCA), a flow of steam
with dispersed droplets forms downstream of the quench front. This flow is crucial for cooling nuclear fuel
rods that are not in direct contact with water, representing a typical Dispersed Flow Film Boiling (DFFB)
scenario. Depending on accident severity, fuel rod deformation may partially block subchannels, diverting
steam towards less deformed areas and potentially impacting cooling. As a result, characterizing heat transfer under such conditions is essential to enhance the nuclear reactor safety during accidents like LOCA.
The COLIBRI experimental loop was designed to assess the heat flux released by steam/droplet flow in
intact and deformed fuel rod subchannels. Experimental results obtained with this facility helped evaluate
various correlations for direct-contact heat transfer calculations in DFFB within the DRACCAR code. In
this article, the DRACCAR code is used to compare different correlations for heat transfer due to droplet
impacts onto the wall calculation. This comparison was made on four COLIBRI experiments, involving
two different droplet mass flow rates (5 kg/h and 11.5 kg/h) and two levels of subchannel deformation
(intact and 90% blocked).
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