Thermally smart characteristics of nanofluids in parallel microchannel systems to mitigate hot spots in MEMS

Mitigation of hot spots in MEMS employing in situ microchannel systems requires a comprehensive picture of the maldistribution of the working fluid and uniformity of cooling within the same. In this article, detailed simulations employing parallel micro channel systems with specialized manifold-channel configurations i.e. U, I and Z have been performed. Eulerian Lagrangian Discrete Phase Model and Effective Property Model with water and alumina water nanofluid as working fluids have been employed. The distributions of the dispersed particulate phase and continuous phase have been observed to be, in general, different from the flow distribution and this has been found to be strongly dependent on the flow configuration. Particle maldistribution has been conclusively shown to be influenced by various migration and diffusive phenomena like Stokesian drag, Brownian motion, thermophoretic drift, etc. To understand the uniformity of cooling within the device, which is of importance in real time scenario, an appropriate figure of merit has been proposed. It has been observed that uniformity of cooling improved using nanofluid as working fluid as well as enhanced relative cooling in hot zones, providing evidence of the smart nature of such dispersions. To further quantify this smart effect, real time mimicking hot-spot scenarios have been computationally probed with nanofluid as the coolant. A silicon-based microchip emitting non-uniform heat flux (gathered from real-time monitoring of an Intel Core i7 4770 3.40 GHz quad core processor) under various processor load conditions has been studied and evidence of enhanced cooling of hot spots has been obtained from DPM analysis.