Comparison of calculated and experimental heat transfer coefficients at the surface of circular cylinders placed in a turbulent cross-flow of air

Abstract

Heat transfer coefficients have been calculated using computational fluid dynamics (C.F.D.) at the surface of an infinite circular cylinder (d = 0.1 m) subjected to a turbulent cross-flow of air whose velocity and turbulence intensities ranged from 0.5 to 5.0 m.s −1 and from 1.5 to 40%, respectively. The turbulence was accounted for by a k-ϵ model completed by near-wall treatment based either on a wall function or on Wolfshtein's low-Reynolds number model. Results confirm that the wall function approach leads to great differences between calculated and experimental mean transfer coefficients. However, mean transfer coefficients are described efficiently by Wolfshtein's model providing that the variation of the damping of turbulent viscosity with the boundary sub-layer thickness is considered. Finally this paper shows that the prediction of surface coefficients by C.F.D. calculations alone has to be taken with caution.