ABSTRACT
Nanofluids represent a class of heat transfer materials that can potentially be “tailored” to meet the heat dissipation requirements of many different commercial applications, including solar heating and cooling systems, heat exchangers, single-phase and two-phase thermal management systems for electronics packaging, domestic refrigeration, nuclear reactor cooling systems, and defense applications. Such extraordinary applicability might ordinarily indicate rapid commercial adoption of these novel technologies. However, scientists have been unable to produce nanofluids with the extraordinary thermal properties that are predicted with the use of effective medium theory. Moreover, their thermal performance in engineering applications is often difficult to predict, largely due to inconsistent thermal property predictions and nanoparticle settling. In this chapter, a review of thermal transport theory will first be provided within the context of nanofluids such that the reader has a fundamental understanding of the physical mechanisms responsible for enhancing and/or limiting heat flow within them. A subsequent survey of thermal property enhancements of water and ethylene glycol–based nanofluids will then be evaluated in order to provide the reader with the current state-of-the-art performance enhancements. In that vein, an analysis of actual versus predicted 202performance enhancement is provided to motivate scientists to pursue further study in this field. Finally, recommendations for improvements in the thermal properties of nanofluids by way of surface functionalization are given in order to allow engineers to develop nanofluids that achieve a status of “Technology Readiness Level 4” as defined by the U.S. Department of Defense.
