Numerical Study of Liquid Metal Turbulent Heat Transfer in Cross-Flow Tube Banks

Abstract

Heavy liquid metals (HLM) are attractive coolants for nuclear fission and fusion applications due to their excellent thermal properties. In these reactors, a high coolant flow rate must be processed in compact heat exchangers, and as such, it may be convenient to have the HLM flowing on the shell side of a helical coil steam generator. Technical knowledge about HLM turbulent heat transfer in cross-flow tube bundles is rather limited, and this paper aims to investigate the suitability of Reynolds Average Navier–Stokes (RANS) models for the simulation of this problem. Staggered and in-line finite tube bundles are considered for compact (a=1.25), medium (a=1.45), and wide (a=1.65) pitch ratios. The lead bismuth eutectic alloy with Pr=2.21×10−2 is considered as the working fluid. A 2D computational domain is used relying on the k−ω Shear Stress Transport (SST) for the turbulent momentum flux and the Prt concept for the turbulent heat flux prediction. The effect of uniform and spatially varying Prt assumptions has been investigated. For the in-line bundle, unsteady k−ω SST/Prt=0.85 has been found to significantly underpredict the integral heat transfer with regard to theory, featuring a good to acceptable agreement for wide bundles and Pe≥1150. For the staggered tube bank, steady k−ω SST and a spatially varying Prt has been the best modeling strategy featuring a good to excellent agreement for medium and wide bundles. A poor agreement for compact bundles has been observed for all the models considered.

The impact of tube bundle layout on the thermal and fluidic behaviour of liquid lead–bismuth eutectic in a helical-coiled once-through steam generator

“…The tube bundles were subjected to a constant heat flux of 20,000 W/m 2 to maintain thermal conditions akin to the experiment conducted by Ref. [ 16 ]. No-slip condition is applied to the walls, excluding the front and back walls where the symmetry boundary condition is proposed.…”

“…They found that due to the intensified turbulence intensity and generation of transverse flow, the highest Nu and friction factor ( f ) is achieved for a helix angle of 45°. The thermal behaviour of LBE in the inline and staggered arrangement was studied by Tassone et al [ 16 ]. They concluded that the steady k −ω SST model combined with the varying turbulent Prandtl number model resulted in the most accurate numerical model.…”