CALCULATION STUDY OF NONEQUILIBRIUM POST-CHF HEAT TRANSFER IN ROD BUNDLE TEST USING MODIFIED RELAP5/MOD2.
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To date there is only very limited data for non-equilibrium convective film boiling in rod bundle geometries. A recent nine (3 multiplied by 3) rod bundle post-critical-heat-flux (CHF) test from the Lehigh University test facility was simulated using RELAP5/MOD2, to assess its capabilities in predicting the overall convective mechanisms in post-CHF heat transfer in rod bundle geometries. The code calculations were compared with experimental data. The code predicted low vapor superheats and void fraction oscillations. A new interfacial heat transfer between the droplet/steam resulted in a reasonable prediction of vapor superheats. A revised dispersed flow film boiling correlation which accounts for the enhancement of steam convective cooling by droplet-induced turbulence was incorporated in the code. Comparison with the data showed a fair agreement.