Turbulent flow and heat transfer in helically coiled pipes at Retau=400 was investigated by DNS using finite volume grids with up to 2.36×10E7 nodes. Two curvatures (0.1 and 0.3) and two torsions (0 and 0.3) were considered. The flow was fully developed hydrodynamically and thermally. The central discretization scheme was adopted for diffusion and advection terms, and the second order backward Euler scheme for time advancement. The grid spacing in wall units was ~3 radially, 7.5 circumferentially and 20 axially. The time step was equal to one viscous wall unit and simulations were typically protracted for 8000 time steps, the last 4000 of which were used to compute statistics. The results showed that curvature affects the flow significantly. As it increases from 0.1 to 0.3 the friction coefficient and the Nusselt number increase and the secondary flow becomes stronger; axial velocity fluctuations decrease, but the main Reynolds shear stress increases. Torsion, at least at the moderate level tested (0.3), has only a minor effect on mean and turbulence quantities, yielding only a slight reduction of peak turbulence levels while leaving pressure drop and heat transfer almost unaffected.

Ciofalo, M., Di Liberto, M., & Marotta, G. (2014). On the influence of curvature and torsion on turbulence in helically coiled pipes. In Proceedings of the 31st UIT Heat Transfer Conference (pp. 435-446). Milano.

On the influence of curvature and torsion on turbulence in helically coiled pipes

CIOFALO, Michele;DI LIBERTO, Massimiliano;Marotta, Gaspare
2014

Abstract

Turbulent flow and heat transfer in helically coiled pipes at Retau=400 was investigated by DNS using finite volume grids with up to 2.36×10E7 nodes. Two curvatures (0.1 and 0.3) and two torsions (0 and 0.3) were considered. The flow was fully developed hydrodynamically and thermally. The central discretization scheme was adopted for diffusion and advection terms, and the second order backward Euler scheme for time advancement. The grid spacing in wall units was ~3 radially, 7.5 circumferentially and 20 axially. The time step was equal to one viscous wall unit and simulations were typically protracted for 8000 time steps, the last 4000 of which were used to compute statistics. The results showed that curvature affects the flow significantly. As it increases from 0.1 to 0.3 the friction coefficient and the Nusselt number increase and the secondary flow becomes stronger; axial velocity fluctuations decrease, but the main Reynolds shear stress increases. Torsion, at least at the moderate level tested (0.3), has only a minor effect on mean and turbulence quantities, yielding only a slight reduction of peak turbulence levels while leaving pressure drop and heat transfer almost unaffected.
Settore ING-IND/19 - Impianti Nucleari
97888-6493-017-6
Ciofalo, M., Di Liberto, M., & Marotta, G. (2014). On the influence of curvature and torsion on turbulence in helically coiled pipes. In Proceedings of the 31st UIT Heat Transfer Conference (pp. 435-446). Milano.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/10447/104586
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