Large eddy simulation is used to investigate the flow structures and enhancing effects on the heat transfer from dimple deployment on the floor in channels. A comparison is carried out on the time-averaged flow structures, Nusselt numbers and heat transfer enhancement at two flow stages as Reynolds number ranges from 5500 to 22,000. And the spatial correlation, which can differentiate the enhancing effect of dimple-induced vortical structures from the background turbulence, is introduced to provide a measure for the enhancing effect of the dimple-induced vortical structures. The results show that the contours of high Nusselt numbers are shaped by the transport of the dimple-induced vortical structures, and the asymmetry in Nusselt number contours are rooted in the asymmetric distribution of vortical structures shed from the dimple.