The state-of-the-art experimental and analytical work on post CHF effects of spacer grids and flow blockage in rod bundles is reviewed and summarized from the point of view of basic heat transfer effects and mechanisms. A perspective is given on what future work is needed to help validate state-of-the-art post CHF grid and blockage heat transfer models.
The hydraulic results of a series of 21-rod bundle water experiments have been analyzed systematically. Models are established for the prediction of the pressure drop over unblocked bundles, grid spacers, coplanar concentric blockage, coplanar concentric blockage with bypass, noncoplanar concentric blockage, and noncoplanar nonconcentric blockage. The models can be extended to other bundles with similar characteristics. The comparisons of these models with the experimental results agree reasonably well.
This report presents data from the Unblocked Bundle, Forced and Gravity Reflood Task of the Full-Length Emergency Core Heat Transfer Separate Effects and Systems Effects Tests (FLECHT SEASET) program. The tests consisted of forced and gravity reflood experiments and steam cooling tests, using electrical heater rods to simulate current nuclear fuel arrays (similar to Westinghouse 17 x 17 assemblies) of PWR and PWR fuel vendors. Data obtained include rod clad temperatures, turnaround and quench times, heat transfer coefficients, inlet flooding rates, overall mass balance, differential pressures and calculated void fractions in the test section, thimble wall and steam temperatures, and exhaust steam and liquid carryover rates.
This report presents data from the Unblocked Bundle, Forced and Gravity Reflood Task of the Full-Length Emergency Core Heat Transfer Separate Effects and Systems Effects Tests (FLECHT SEASET) program. The tests consisted of forced and gravity reflood experiments and steam cooling tests, using electrical heater rods to simulate current nuclear fuel arrays (similar to Westinghouse 17 x 17 assemblies) of PWR and PWR fuel vendors. Data obtained include rod clad temperatures, turnaround and quench times, heat transfer coefficients, inlet flooding rates, overall mass balance, differential pressures and calculated void fractions in the test section, thimble wall and steam temperatures, and exhaust steam and liquid carryover rates.
