UNSTEADY SIMULATION OF TURBULENT FLOW AND HEAT TRANSFER IN A CHANNEL WITH PERIODIC ARRAY OF CUBIC PIN‐FINS

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An unsteady three-dimensional numerical study is performed to explore flow and heat transfer in a periodic array of cubic pin‐fins housed inside a channel. The pin‐fins are arranged in an in-line pattern with both streamwise and transverse periodicity set to 2.5 times the pin-fin dimension. Calculations are done in the turbulent flow regime for Reynolds numbers in the range of 7,090–13,280. The unsteady Reynolds-averaged Navier–Stokes (URANS) and energy equations are solved using higher-order temporal and spatial discretization schemes. An unsteady k – ϵ turbulence model is employed to model the unresolved turbulence fluctuations. Large eddy simulations (LES) are also performed for a Reynolds number of 7,090 for validation purposes. The URANS results are able to resolve the discrete large-scale spatial and temporal fluctuations in the flow, and the time-averaged predictions with URANS match the LES results very well. The large-scale fluctuations in the flow appear primarily in the region between the cubic fins, but are linked to low-amplitude oscillations in the outer flow.Three thermal boundary conditions are studied: (1) only channel wall heated (2) only pin‐fins heated, and (3) both channel wall and pin‐fins heated. The overall heat transfer enhancement is about 1.8–2.0 times the heat transfer from a smooth duct flow. The heat transfer from pin‐fins is found to be 5–9% higher than that from the top wall at low Reynolds numbers (7,090 and 8,900), while it is of comparable magnitude at higher Reynolds number (13,280).