The paper presents the results of numerical modeling of a developed, spatially periodic turbulent flow and heat exchange in a rectangular channel (W/H = 1.5), on a wall of which of width W square cross-section fins with a side e = 0.1H are located with a pitch P = H, inclined relative to the channel axis by 45°. The flows of incompressible media are considered at Prandtl numbers equal to 0.01, 0.7 and 10, and Reynolds numbers in the range 104–106. The mathematical model of the flow is based on the RANS method and the equations of k–ω SST turbulence model. An analysis of heat emission intensification and of increase in the hydraulic resistance compared to flow in a smooth channel is performed. Dimensionless dependences for integral characteristics of heat emission are obtained.