Multiregion Analysis of the Effect of Rod Displacement on Heat Transfer in Slug Flow Through Closely Packed Rod Bundles

The heat transfer characteristics of a rod which is dislocated from its symmetrical position are studied analytically for slug flow through tightly packed rod bundles (P/D ratio down to ≈1.00). Explicit equations describing the temperature fields in the fuel core, the cladding, and the elemental coolant flow area are obtained by assuming uniform fuel power density. Variation of the rod-average Nusselt number, as well as the heat flux distribution at the outer wall of the cladding, is examined for selected values of σ, the P/D ratio, the cladding thickness parameter, λ(=r₁/r₂) and the thermal conductivity ratios, κ and κ_w. The present solutions, when specialized to the case of σ = 0.0 (i.e., no rod displacement) show excellent agreement with the results reported by Axford and by Dwyer and Berry who studied the corresponding three-region and two-region problems, respectively, for symmetrical rod bundles with no rod displacement.