(An) experimental and theoretical investigation of hydraulic characteristics of helical wire spacers in fuel rod bundles

Abstract

An experimental and theoretical investigation of hydraulic characteristics of spiral wire spacer in rod bundles has been carried out to predict the pressure drop through wire wrapped rod bundles. Under assumption that the universal velocity profile for circular tube can be applied to non-circular channel, a theoretical and general friction factor model for infinite triangular array bare rod bundle in turbulent flow region for small P/D, i.e., P/D≤1.2 has been introduced from the normalized wall shear stress profile. The model has been extended to be applicable to large P/D conditions, i.e., P/D>1.2, under assumption of uniform wall shear stress and the equivalent annular zone concept for large rod distance. The turbulent friction factor for triangular array bare rod bundle in a duct has been developed based on the developed friction factor model for the infinite triangular array bare rod bundle by considering the effects of the wetted perimeter and the number of rods. The present friction factor model shows good agreement with the friction factor data for overall P/D ranges. To investigate the friction factor, the pressure drop, and the hydraulic characteristics of wire spacer, a series of experiment were performed over 19-pin wire-wrapped rod bundle. The experiments were performed with water as a working fluid under atmospheric pressure. Since the friction factor for wire-wrapped rod bundle depends to a large degree on the geometric parameters, i.e., P/D, H/D, the number of rod number, and the Reynolds number, the focus was given to determine the effect of these parameters. Four different test sections were manufactured in combinations of two different ratios of the wire diameter to the rod diameter (P/D) and two different ratios of the wire lead length to the rod diameter (H/D). A total of 293 experimental pressure drop measurement data have been obtained from the test sections varying the flow rate in the range of Reynolds number from 100 to 30,000. Various ...