Numerical study of laminar flow and heat transfer in microchannel heat sink with offset ribs on sidewalls

A numerical investigation has been carried out to examine the characteristics of laminar flow and heat transfer in microchannel heat sink with offset ribs on sidewalls. The three-dimensional equations considering entrance effect, conjugate heat transfer, viscous heating and temperature-dependent properties are solved for the fluid flow and heat transfer in the microchannel heat sink. Five different shapes of offset ribs are designed, including rectangular, backward triangular, isosceles triangular, forward triangular and semicircular. Results show that the offset ribs result in significant heat transfer enhancement and higher pressure drop. Depending on the different offset ribs and Reynolds number (190 ≤ Re ≤ 838) studied in the present work, Nusselt number and friction factor for the microchannel heat sink with offset ribs are 1.42-1.95 and 1.93-4.57 times higher than those for the smooth one, leading to performance evaluation criteria of 1.02-1.48. Further, as a consequence of significant pressure drop, the microchannel heat sink with offset ribs gradually loses its advantage as an effective heat transfer enhancement method at higher Reynolds number.