Computations were performed to study three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with 45° V-shaped ribs. The channel aspect ratio (AR) is 4:1, the rib height-to-hydraulic diameter ratio (e/Dh) is 0.078 and the rib-pitch-to-height ratio (P/e) is 10. A total of eight calculations have been performed with various combinations of rotation number, Reynolds number, coolant-to-wall density ratio, and channel orientation. The rotation number and inlet coolant-to-wall density ratio varied from 0.0 to 0.28 and from 0.122 to 0.40, respectively, while the Reynolds number varied from 10,000 to 500,000. Three channel orientations (90°, −135°, and 135° from the rotation direction) were also investigated. A multi-block Reynolds-Averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure for detailed predictions of mean velocity, mean temperature, turbulent Reynolds stresses, and heat fluxes and heat transfer coefficients.