Design of Complex Structured Monolithic Heat Sinks for Enhanced Air Cooling

The design and characterization of monolithic heat sinks, which can take the form of complex structures, is reported. The designs were conceived to augment heat transport for enhanced air cooling by exploiting clearly identified physical mechanisms, i.e., by streaming the flow through a 2-D array of polygonal ducts, by introducing flow-obstacle-induced local mixing, and by exploiting hydrodynamic instabilities to sustain flow unsteadiness. Fabrication of these unconventional designs was achieved by 3-D printing plastic patterns and converting them into monolithic copper structures by investment casting. A direct simulation approach aided by analytical solutions and experimental validation was undertaken to quantify fluid flow and heat transfer parameters. This paper concludes by quantifying the performance enhancement of the proposed heat sink geometries relative to a conventional longitudinally finned heat sink. On an equal pumping power basis, finned foam and slotted hexagonal heat sinks outperform conventional parallel plate finned heat sinks. On the other hand, the parallel plate heat sinks are better for pressure drop less than 20 Pa and slotted honeycombs are better for higher pressure drops (>;20 Pa).