Turbulence structure in triangular subchannels of a reactor bundle model

Abstract

Presented is a study of turbulence structure in two triangular subchannels of a reactor bundle at both design condition and a case when one of the outermost rods is in contact with the wall. Measured parameters include rms velocities, autocorrelation coefficients, Eulerian integral length scales, energy budget and eddy viscosities. Most data were compared with pipe flow data and the similarity between the two subchannels was also discussed. The Reynolds number of the experiment based on either subchannel's hydraulic diameter and bulk velocity was 74000 and the pitch to diameter ratio at design condition was 1.14. The magnitudes of rms velocities, Eulerian integral length scales, Taylor microscales and kinetic energy dissipation rate at rod-wall contact condition were lower than those at design condition in respective subchannels. The radial eddy viscosities at design in both subchannels were identical and nearly constant, while at rod-wall contact, they depended on the radial distance from the rod surface.