Numerical Evaluation of the Effectiveness of Micro Pulsating Water Jets for Cooling of Microchips

In this study the effects of having multiple synthetic jet actuators and multiple orifices in a single jet actuator on creating better flow mixing and improving heat transfer in micro-channels have been investigated numerically. Unsteady computations of laminar flow have been performed for two dimensional configurations of micro-channel open at either end. A constant heat flux of 1 MWm⁻² at the top of the silicon wafer represented the heat generated by the microchip. Synthetic jet actuators were attached to the bottom wall of the channel, with the 50 μm wide orifice. It is shown that by using double orifices single synthetic jet actuator, the heat transfer enhancement in micro-channels can be greatly improved. At the end of 30 cycles of actuation, the maximum temperature in the wafer has been reduced by approximately 27 K and the minimum temperature on the bottom of the wafer has been reduced by approximately 19 K in comparison with the steady flow values. In comparison with a single orifice synthetic jet actuator, double orifices synthetic jet actuator led to an additional 10 K reduction of the maximum temperature in wafer and 4 K reduction of minimum temperature on the interface of the wafer and water. It was demonstrated that the number of synthetic jet actuators is not the main factor influencing the thermal performance. The crucial factor is the number of impinging jets generated from the orifice which encourages better mixing in the flow. However, there is a distinct advantage associated with having multiple jet actuators in that out of phase flow could be generated which led to even lower temperatures than the in-phase jets.