The very low ratio of kinematic viscosity to thermal diffusivity of liquid metals proves favorable in applications of heat transfer, especially for high thermal loads, and otivates their application as heat transfer medium. Their low Prandtl number leads to a scale separation between the velocity and temperature fi elds with the latter being much smoother than the former. In buoyancy affected fl ows, this scale separation lso affects, both, the velocity fi eld and turbulence due to the buoyancy force term driving the fl ow. To account for these effects in turbulence models, according data is needed or their validation. Such data is presented by this work which investigates the impact of buoyancy on the fl ow of liquid sodium and heat transfer in the confi gurations of a vertical backward-facing step and a square duct. Both, the forced and the mixed convection regime with aiding buoyancy conditions are considered.