Numerical and experimental investigation on labyrinth seal mechanism for bypass flow reduction in prismatic VHTR core

Numerical and experimental investigation on labyrinth seal mechanism for bypass flow reduction in prismatic VHTR core
Issue Date
Series/Report no.
NUCLEAR ENGINEERING AND DESIGN; vol.262 startpage 525 endpage 534
Core bypass flow in block type very high temperature reactor (VHTR) occurs due to the inevitable gapsbetween the hexagonal core blocks for the block installation and refueling. Since the core bypass flowaffects the reactor safety and efficiency, it should be minimized to enhance the core thermal margin. Inthis regard, the core bypass flow reduction method applying the labyrinth seal mechanism was developedand optimized by using the single-objective shape optimization method. Response surface approximation(RSA) method was adopted as the optimization method. Side wall of the replaceable reflector block wasredesigned and response surface approximate model was adopted to optimize the shape of the reflectorwall. Computational fluid dynamics (CFD) analyses were carried out not only to assess the limitation ofexisting method of bypass flow reduction, but also to optimize the design of a newly developed reductionmethod. The experiment with Seoul National University (SNU) multi-block experimental facility wasperformed to demonstrate the performance of the reduction method. It was found that the effect of theexisting bypass flow reduction method by sealing the bypass gap exit was restricted nearby the lowerregion of the core. However, the flow resistance factor of the bypass gap increased from 18.04 to 26.24by the optimized reduction method. The results of the performance test showed that the bypass flowdistribution was reduced throughout the entire core regions. The bypass flow ratios at the inlet and theoutlet were reduced by 36.19% and 14.66%, respectively. In conclusion, it is expected that the core thermalmargin and efficiency of VHTR reactor cooling can be enhanced by applying the developed bypass flowreduction method.
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College of Engineering(공과대학) > Mechanical Engineering(기계공학) > Journal Papers, Reports(기계공학 논문, 보고서)
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