Effect of variable properties on heat transfer in a micro-channel with a synthetic jet

The effect of variable properties on thermal enhancement in a micro-channel due to synthetic jet and cross-flow fluid interaction is examined. Three-dimensional simulation is performed for low Reynolds number flow of water subjected to localized heating at the top surface of the micro-channel when a silicon wafer is etched. The complex conjugate heat transfer between the silicon substrate and water flow is analyzed. Axial conduction introduced by the thermal conductivity, density, and heat capacity temperature dependence of silicon is included. Computational results for the case of variable properties are compared against those of constant properties in both steady-state and transient conditions. The velocity field in the channel is found to be greatly influenced by the temperature distribution when the variable transport properties of water are taken into account. Numerical results of 30 full cycles of the actuator are simulated in order to track the development of the fluid flow and heat transfer. Quasi-steady results, which indicate the maximum cooling potential of a single synthetic jet actuator, are presented. The maximum, minimum, and average temperature profiles show a consistent reducing trend between the solutions of the variable and constant properties.