Large Eddy Simulation of Liquid Metal Turbulent Mixed Convection in a Vertical Concentric Annulus

Abstract

In the present study, turbulent forced and mixed convection heat transfer to a liquid metal flowing upwards in a concentric annulus is numerically investigated by means of large eddy simulation (LES). The inner-to-outer radius ratio is 0.5. The Reynolds number based on bulk velocity and hydraulic diameter is 8900, while the Prandtl number is set to a value of 0.026. A uniform and equal heat flux is applied on both walls. LES has been chosen to provide sufficiently accurate results for validating Reynolds-averaged turbulence models. Moreover, with the thermal sublayer thickness of liquid metals being much larger than the viscous hydrodynamic one, liquid metals present a separation between the turbulent thermal and hydrodynamic scales. Thus, with the same grid resolution, it is possible to perform a LES for the flow field and a “thermal” direct numerical simulation (DNS) for the temperature field. Comparison of the forced convection results with available DNS simulations shows satisfying agreement. Results for mixed convection are analyzed and the differences with respect to forced convection at the same Reynolds number are thoroughly discussed. Moreover, where possible, a comparison with air is made.

Numerical study on the heat transfer characteristics of a liquid lead–bismuth eutectic in a D-type channel

“…Turbulent heat fluxes were modelled with a simple gradient diffusion hypothesis (Marocco et al, 2017), and the results showed that the turbulent Prandtl number (Pr t ) can be locally evaluated either with a correlation or by solving some additional transport equations. Furthermore, mixed large eddy simulation (LES) and direct numerical simulation (DNS) methods were also used to calculate the mixed convection of a liquid metal (Marocco and Garita, 2018), and the difference between the forced and assisted convection for the liquid metal was assessed at the same Reynolds number in detail. In addition, the flow and heat transfer characteristics of a liquid LBE in circular pipes were extensively studied.…”