Large eddy simulation of flow and heat transfer of the flat finned tube in direct air-cooled condensers

The striking phenomenon during the flow past multiple wavy finned flat tubes is the generation of a complex flow structure as a consequence of the nonlinear interactions among the wakes behind the bodies. This study investigates the flow structures, heat transfer and vortex-shedding characteristics behind a single and two side-by-side flat finned-tubes at a gap ratio (spacing to diameter ratio) of 1.95. The three-dimensional numerical simulations are performed with the computational fluid dynamics code ANSYS FLUENT12.0 using large eddy simulation (LES) with the subgrid-scale model-Dynamic Smagorinsky–Lilly model. The instantaneous properties of velocity, temperature, pressure and vorticity are obtained and analyzed. In addition, the time history of drag and lift coefficients, local Nusselt number and skin friction coefficients are determined and discussed at various Reynolds numbers. Special attention is paid to investigate the effect of the Reynolds number on the vortex-shedding characteristics and the mutual interaction of the wakes behind the two side-by-side finned-tubes. A discussion on the mechanism of vortex-shedding and wake interaction behind the flat finned-tube and their effects on the thermal histories are presented.