A comparison and assessment of approaches for modelling flow over in-line tube banks

• We present wall-resolved LES and URANS simulations of periodic flow in heated in-line tube banks.
• Simulations of flow in a confined in-line tube-bank are compared with experimental data.
• When pitch-to-diameter (P/D) ratio becomes less than 1.6, the periodic flow becomes skewed.
• URANS tested here unable to mimic the periodic flow at P/D = 1.6.
• In confined tube banks URANS suggest alternate, in the axial direction, flow deflection.

The paper reports experiences from applying alternative strategies for modelling turbulent flow and local heat-transfer coefficients around in-line tube banks. The motivation is the simulation of conditions in the closely packed cross-flow heat exchangers used in advanced gas-cooled nuclear reactors (AGRs). The main objective is the flow simulation in large-scale tube banks with confining walls. The suitability and accuracy of wall-resolved large-eddy simulation (LES) and Unsteady Reynolds-Averaged Navier–Stokes (URANS) approaches are examined for generic, square, in-line tube banks, where experimental data are limited but available. Within the latter approach, both eddy-viscosity and Reynolds-stress-transport models have been tested. The assumption of flow periodicity in all three directions is investigated by varying the domain size. It is found that the path taken by the fluid through the tube-bank configuration differs according to the treatment of turbulence and whether the flow is treated as two- or three-dimensional. Finally, the important effect of confining walls has been examined by making direct comparison with the experiments of the complete test rig of Aiba et al. (1982).