Prediction of single-phase turbulent mixing rate between subchannels using subchannel geometry factor

We present a method for calculating the single-phase turbulent mixing rate between subchannels in nuclear fuel rod bundles. In this method, the mixing rate is calculated using a newly defined subchannel geometry factor, which depends only on the geometry of the subchannel cross section, and the mean turbulent diffusivity computed from Elder's correlation. In order to confirm the validity of the method, experimental data of the turbulent mixing rate were obtained by a tracer technique for single-phase flows of air or water in several multiple channels consisting of two subchannels. The flows were fully developed turbulent flows with a Reynolds number range from 5000 to 66000. The predictions by the proposed method were in good agreement with the experimental data for several subchannel geometries. (author)