Unsteady flow and heat transfer characteristics were studied numerically using the numerical scheme validated in the previous study for an in-line array of fins located in a channel. It is found that there exists at least one peak in the streamwise distribution of the instantaneous local Nusselt number, NuH, on the surfaces of fins located downstream from the destabilized wakes of other fins. The peak of NuH distribution appears at the minimum position of the instantaneous local skin friction. Thus, heat transfer enhancement of fin arrays is accompanied by the local and instantaneous dissimilarity between momentum transfer and heat transfer. The dissimilarity is related to the fluid motion corresponding to the outward and wallward interactions of near-wall turbulence. These fluid motions are caused by the rotating fluid motion induced by intermittently appearing vortices. These vortices are formed from the tips of protruding parts of the interface between the pcsitive and negative vortex layers in the wake. This rotating fluid motion pumps the hot fluid from the fin surface region to the main flow region and entrains the fresh fluid from the main flow region into the near-wall region from its downstream side.