Determination of turbulent exchange coefficients in a rod bundle

A tracer gas is injected into a single subchannel of a large air flow model of a reactor rod bundle. Axial variations in the tracer flux are determined by sampling at two downstream positions in both the injection subchannel and those adjacent to it. This information, with measured subchannel area changes, is used to calculate crossflows and the turbulent eddy diffusion coefficient. The latter number agrees with the results of other investigators in regular pipe flows. Also determined are distributional factors which would be required for modeling the transport equations, for this particular scalar distribution, with a typical lumped parameter computer code.