Nanofluid Properties and Their Effects on Convective Heat Transfer in an Electronics Cooling Application

Abstract

In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate. Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present a self-contained study of the properties and effectiveness of an alumina in water nanofluid. Flow-cooling is studied in an off-the-shelf fluid cooling package for electronics to examine the effects of the particulates in a practical scenario. We measure the thermal conductivity and viscosity of the same suspensions to assure consistent interpretation of our results. We find that, while there is no anomalous enhancement of the thermal properties or transport, there is a benefit to using a low volume fraction alumina nanoparticle suspension over using the base fluid alone. In fact, there is an optimal volume fraction (1%) for this nanofluid and electronics cooling system combination that maximizes the heat dissipated. However, we find that this benefit decreases as the volume fraction, and hence the viscosity, increases. Understanding where the trade-off between viscosity increase and thermal conductivity increase occurs is critical to designing an electronics cooling system using a nanofluid as a coolant.