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Experimental study of thermal non-equilibrium convective boiling in post-critical heat-flux region in rod bundles

Thesis/Dissertation ·
OSTI ID:6884585
An experimental investigation of convective heat transfer beyond critical heat flux (CHF) was performed with a full size test setup. Post-CHF experiments with simultaneous measurements of nonequilibrium vapor temperature at two axial locations was successfully performed for a 3 x 3 rod bundle array, under stabilized post-CHF conditions. In addition, some transient (slowly moving CHF) experiments were also conducted. A total of 374 data points, 98 steady-state with fixed CHF point and 276 transient with moving CHF point, were obtained. The range of the data included conditions pertinent to reflood and quench phase of light water reactors. Very high vapor and wall superheats were measured. Typical vapor superheat encountered was 85% of corresponding wall superheat and was in the range of 400 to 600/sup 0/C. The experimental results indicated the existence of two different regions downstream from the CHF point, namely near region and far region. Modeling of the heat transfer process in convective film boiling must account for these two regions of behavior. Significant variations in radial vapor temperature, up to 150/sup 0/C, was found. It showed that use of one dimensional models for prediction of thermal hydraulic conditions in a rod bundle is not proper. Available models, developed from a single tube data base, showed no reasonable prediction of heat transfer for the new rod bundle data.
Research Organization:
Lehigh Univ., Bethlehem, PA (USA)
OSTI ID:
6884585
Country of Publication:
United States
Language:
English