A numerical study of the enhancement of chip cooling via a flow-disturbing obstruction block

Two-dimensional convection heat transfer on a chip with a flow-disturbing obstruction block above it, as induced by natural coupling between flow and structure, was investigated numerically. The effects of various induced trajectories of the obstruction block on chip cooling were investigated. A numerical algorithm PISO, a conjugate heat transfer scheme for fluid-solid thermal interactions with moving grids was used to solve a coupled system of governing equations. The study shows that the induced trajectories of the obstruction block, as a result of natural coupling between the block and the flow, have a noticeable impact on chip cooling. The present study successfully simulated the motion of an obstruction block on a heated chip and the associated "lock-in" phenomenon due to natural coupling. When lock-in occurs, the trajectory of the block movement follows the shape of an oval. If this occurs, the cross-stream movement is much larger than the stream-wise movement. Passively induced disturbance of the flow field for the case with a large oval trajectory yields an enhancement of heat dissipation from the chip. In general, the vibration of the block as induced by an unbalanced pressure field around the chip would disturb the thermal boundary above the chip. Hence, the induced vibration enhances heat dissipation from the chip. It is concluded in this study that a vibrating obstruction block with a lock-in mode of oscillation is a vital condition for achieving an enhancement of heat dissipation as can be observed by an increase of Nusselt number on the chip top surface.