To investigate the mechanism of heat transfer augmentation, numerical computations of turbulent now and heat transfer in a parallel plate channel, attached transversely with turbulence promoters at regular intervals on the lower surface, have been performed by using a simple turbulence model and the Galerkin finite element method. It has been revealed that, in the optimum case, a vortex of peculiar structure is formed behind each turbulence promoter, and it plays a significant role in enhancing the heat transfer rate; and the maximum augmentation effect reaches about 13% when taking the pumping power into account, while it is 67% when neglecting the pumping power. It also turns out that the optimum interval of turbulence promoters is about 10 times the promoter diameter, and the optimum Reynolds number is about 9000.