Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling Page: 4 of 11
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enlarging the bottleneck by opening the space available for
steam venting in the circumferential locations away from the
shear key positions. According to Cheung et al. (2003), by
enlarging the minimum gap the pressure drop through the
bottleneck could be reduced appreciably. As a result, more flow
could be induced when subjected to the same downward facing
boiling conditions, which in turn leads to a higher CHF limit.
- --
Aluminum Coating
V
Copper Coating
Figure 1. SEM PHOTOS OF ALUMINUM AND
COPPER MICRO-POROUS LAYER
COATINGS
Subscale Boundary Layer Boiling (SBLB) Test Facility
The test facility (see Fig. 3.) employed in this study
consisted of a water tank with a condenser assembly, a heated
hemispherical test vessel surrounded by a scaled insulation
structure, a data acquisition system, a photographic system, and
a power control system. The test vessel, having a diameter of
0.305m, had an interchangeable lower head simulator. Both a
plain vessel and a coated vessel were used in this study. The
water tank was designed to conduct boiling experiments under
simulated ERVC conditions. The size of the water tank was
chosen to accommodate hemispherical vessels of diameters up
to 0.381m and to minimize the effect of recirculation motions
created by the boiling process. The tank contained large viewingwindows for observation, video-taping and photo records, and
was equipped with three immersion heaters with a total power
of 36kW for preheating the water to a desired temperature. The
test vessel comprised two main parts: a heated hemispherical
lower head simulator and a non-heated cylindrical upper
portion. Groups of cartridge heaters were used to deliver power
input to the lower head.
Flow Channel
Enhanced Insulation
Structure
Space Openning
Figure 2. SCHEMATIC DIAGRAM OF THE
REACTOR VESSEL ENHANCED
INSULATION STRUCTUR
The data acquisition system, capable of monitoring 32
thermocouple signals with a sampling rate of up to twenty per
second, was specifically calibrated for use in boiling
experiments. An ACPC-16 board was installed in a computer.
The ACPC-16 board had 16 analog inputs and 16 digital
input/output channels. An additional ACPC-16 board could also
be installed in the PC to give a total of 32 analog inputs. The
ACPC-16 board had resolution capacities in the range of 12 to
16 bits, equivalent to 0.024% and 0.0015% of full scale,
respectively. The board had six voltage ranges that could be set
according to the sensor used.3
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Yang, J.; Cheung, F. B.; Rempe, J. L.; Suh, K. Y. & Kim, S. B. Correlations of Nucleate Boiling Heat Transfer and Critical Heat Flux for External Reactor Vessel Cooling, article, July 1, 2005; [Idaho Falls, Idaho]. (https://digital.library.unt.edu/ark:/67531/metadc880503/m1/4/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.