Numerical and experimental investigation on the baffle design in secondary side of the PRHR HX in AP1000

The effective and reliable operation of the Passive Residual Heat Removal System (PRHRS) is very significant for the safety of the reactor. However, the passive heat sink tank IRWST in PRHRS is vulnerable to get stratified, which has deleterious impacts on the heat transfer effect of the Passive Residual Heat Removal Heat Exchanger (PRHR HX). In the present work, both the numerical simulations and experiments are conducted to investigate the passive baffles designs of the PRHR HX&IRWST. An overall scaled-down separate-effects PRHR HX&IRWST experimental test bench has been built, and the experimental data are used to validate the numerical methods in the prototype PRHR HX model. Different passive baffles Designs A-D are tested employing the commercial CFD software CFX, and then validated by the baffles experiment. The influencing factors of baffles number, thermal conductivity, and baffles shape are investigated. Both the numerical and experimental temperature distributions, natural convection velocity, thermal stratification extent, as well as the Heat Transfer Coefficient are analyzed. The complicated factors combine to determine the overall HTC in baffle design. The numerical and experimental results provide possible improvement ways for the optimization of the PRHR HX baffles design, which have practical engineering application significance in the optimum design of the passive safe system in AP1000 plant.