Riblets are well known as a passive mean for drag reduction in turbulent flow conditions, but their effectiveness for heat transfer
is quite controversial. In this paper, we report our numerical results for fully developed laminar and turbulent flow and heat transfer in a channel with triangular riblets. Two different ribbed channels are considered, under a constant heat flux boundary condition. In the turbulent regime, the study is performed by means of direct numerical simulation at a Reynolds number, based on the wall-shear velocity, Re = 180, for a fluid with a Prandtl
number Pr = 0.71. The results obtained are in good agreement, for the flow and turbulent quantities, with past experimental and numerical studies, but the predicted heat transfer effciency, in the turbulent regime, is lower than some of the experimental studies.
