Galinstan-Based Microgap Cooling Enhancement Using Superlyophobic Surfaces
12 February 2013
Analyses of conventional microchannel and microgap cooling show that galinstan, a recently developed non-toxic liquid metal that melts at -19 C, may be more effective than water for high flux thermal management applications. This is because its thermal conductivity is nearly 30 times that of water. However, since the specific heat per unit volume of galinstan is about half that of water and its viscosity is 2.5 times that of water, caloric, rather than convective, resistance is dominant. Significantly, the high surface tension of galinstan (10 times that of water) implies that it can remain in the hydrophobic state at the requisite pressures for driving flow through microchannels and microgaps. Hence, we analytically investigate the effect of using superlyophobic microgaps in the laminar flow regime to ascertain their efficacy in reducing overall thermal resistance of galinstan-based microgap cooling. Reductions in friction factor, which reduce caloric resistance, and Nusselt number, which increase convective resistance, occur due to a low viscosity fluid layer interposed between the channel walls and galinstan. They are accounted for by recently developed expressions in the literature to calculate hydrodynamic slip lengths and thermal slip lengths and the resulting friction factors and Nusselt numbers.
