The flow structures and heat transfer characteristics in fan flows without and with a 90o rectangular-plate turbulator mounted, separately, on the bottom and top walls of a duct were experimentally investigated. The plate to duct height ratio was fixed at 0.429. Eight heated plates, placed along the bottom wall of the duct, were used as the heat transfer surfaces. The studies included three-component mean and fluctuating velocity measurements at duct cross-sections and near the heat transfer surfaces using laser Doppler velocimetry. The near-wall axial vorticities, turbulent kinetic energy and axial mean velocities were obtained from the measured velocity data. The temperatures on the heat transfer surfaces were measured using thermocouples to obtain the Stanton numbers. Results show that both the top-wall and bottom-wall rectangular-plate turbulators in fan flows have the effect to augment the heat transfer and to cause increases in the near-wall axial vorticity, turbulent kinetic energy and averaged axial mean velocity. The strength of the secondary flow (axial vorticity) and the convective effect (axial mean velocity) are the main fluid dynamic factors affecting the heat transfer distribution for the fan flows across the bottom- wall and top-wall rectangular-plate turbulators, respectively.