•A lateral fluid transport contributes to the heat transfer enhancement behind the rib.•Vortex structures deteriorating heat transfer are eliminated by modified rib shapes.•Thermal performance is increased for ribs not extended over the total channel width. Delayed Detached Eddy Simulations with the k-ω-SST turbulence model were conducted for 8.0 MPa pressurized helium-gas flow in cooling channels with rib arrays on one wall at a Reynolds number of Re = 1.05 × 105. Turbulent flow and heat transfer were determined for arrays of eight variously configured V-shaped and transverse ribs. The relative roughness was e/Dh = 0.0638 and 0.0652 and the rib pitch was p/e = 10. The results showed that for ribs not extended over the total channel width, form drag was reduced and flow stagnation regions with a low heat transfer at the rib corners on the sides disappeared, whereas heat transfer by forced convection increased. Compared to smooth channel flows, the Nusselt numbers were increased by a factor of 1.6–1.8 and 2.2–2.5 for the transverse and V-shaped ribs, respectively. The corresponding friction factors were enhanced by a factor of 2.4–2.9 and 2.8–3.7, respectively. Evaluation of the thermal performance of structured cooling channels in comparison with smooth cooling channels revealed that thermal performance was best for the upstream directed 60° V-shaped ribs. The results showed that secondary flow motion induced by a V-shaped rib configuration caused an outward convective fluid transport within the recirculation region behind the rib. Vortical structures associated with local heat transfer deterioration behind the rib could be eliminated by appropriate designs of rib cross sections. Both lateral convective fluid transport and the elimination of vortical structures deteriorating heat transfer were found to lead to a significant heat transfer enhancement in the leeward rib region for the V-shaped ribs with modified cross section.