Numerical analysis of heat transfer enhancement by spacers in subchannels at supercritical pressure condition

Takase, Kazuyuki; Misawa, Takeharu; Yoshida, Hiroyuki  

For the thermal design of supercritical water reactors, it is necessary to develop an analysis method to correctly predict turbulent heat transfer characteristics in subchannels of fuel bundles. Spacers are set into the subchannels to keep a distance between adjacent fuel rods. The turbulent heat transfer generally enhances by reduction of cross-sectional area in the subchannels due to the existence of the spacers. However, since thermo-physical properties of supercritical fluids drastically change at the vicinity of the pseudocritical point, the enhancement of the turbulent heat transfer depends on the thermal design. Then, the Japan Atomic Energy Agency is developing the analysis method to predict thermal-hydraulic characteristics of the supercritical fluids. The heat transfer calculations were performed using a newly developed code under the condition of a subchannel with a specer, and the enhancement of the turbulent heat transfer coefficient in subchannels with the spacer was analyzed numerically.