Application of Metallic Nanoparticle Suspensions in Advanced Cooling Systems

Abstract

One of the authors has proposed that an innovative new class of energy-efficient heat transfer fluids can be engineered by suspending nanometer-sized metallic particles (nanoparticles) in conventional heat transfer fluids. The resulting “nanofluids” are expected to exhibit much higher thermal conductivities than those of currently used heat transfer fluids and represent the best hope for high-performance cooling in next-generation cooling systems. In this study, the advanced cooling technology has been applied to cooling crystal silicon mirrors used in high-intensity X-ray sources such as Argonne’s Advanced Photon Source. Because the X-ray beam creates tremendous heat as it strikes the mirror, cooling rates of 2000–3000 W/cm2 must be achievable with the advanced technology. Analysis has been carried out to estimate the performance of microchannel heat exchangers with water, liquid nitrogen, and nanofluids as the working fluid. The design and optimization procedures for microchannel heat exchangers show the existence of an optimal channel width that minimizes the thermal resistance of a microchannel heat exchanger. For a pressure drop of 210 kPa (30 psi), the optimized channel width and depth are 56 μm and 360 μm for a water-cooled silicon heat sink and 39 μm and 1410 μm for a liquid-nitrogen-cooled silicon heat sink. For the optimized configuration, performance of the nanofluid-cooled microchannel heat exchanger has been compared with that of a water-cooled and liquid-nitrogen-cooled microchannel heat exchanger. The results show the superiority of a nanofluid-cooled microchannel heat exchanger. When nanofluids are used, the thermal resistances are reduced and the power densities are increased. Excellent thermal performance of a silicon microchannel heat exchanger has been demonstrated when nanofluids were used as the room temperature coolant.