Characteristics of turbulent flow and heat transfers which develop in a heated duct are studied through Large Eddy Simulation (LES) technics . Cooling channels of rocket engines constitute one of the industrial applications. We here consider a simplified geometry consisting of a curved duct of rectangular cross section. The unsteady filtered Navier-Stokes equations are solved by means of a compact numerical scheme, predictor-corrector, second order in time, fourth in space. The subgrid scale model used is the selective structure function model. The results bring to light the development of a strong secondary flow linked with the radial pressure gradient which develops in the curved part. This secondary flow takes the shape of two counter rotating cells of Ekman type close to the convex wall. Close to the concave wall, unsteady vortices of Görtler type arise. This complex flow is thus characterised by sweeps and ejections directly linked with the heat transfer between the flow and the heated curved walls. The Nusselt number undergoes strong transverse variations which might yield material alterations of the heated wall. We evaluate the influence of the geometrical and physical parameters on the flow and the heat exchanges before proposing a solution to homogenize the heat transfers by means of passive control.