Effect of the number of periodic module on flow and heat transfer in a periodic array of cubic pin-fins inside a channel

An unsteady three-dimensional numerical study is carried out to investigate the flow and heat transfer in a periodic array of cubic pin-fins placed inside a channel. The pin-fins arranged in an in-line pattern having both streamwise and transverse periodicity equal to 2.5 times the pin-fin dimension are inserted into the channel. Computations are carried out in the turbulent flow regime for a Reynolds number of 7125. The unsteady spatially filtered-averaged Navier-Stokes and energy equations are solved using higher-order temporal and spatial dis-cretization schemes. A large eddy simulation (LES) turbulence model is employed to model the unresolved turbulence fluctuations. The effect of the number of inter-rib periodic modules on both instantaneous and time-averaged flow and heat transfer is studied in the present study. Total of four different cases with a varying number of inter-rib periodic modules are considered. The time-averaged Nusselt number in all cases matches quite closely with experiments. The instantaneous flow and temperature fields do not show any flow periodicity over the chosen inter-rib modules. However, the time-averaged flow and temperature field reveal the flow and geometric periodicity to be equal.