A Review of Heat Transfer in Nanofluids

Publisher Summary This chapter focuses on nanofluids, highlighting its uses and various mechanisms involved in its working. Modern nanotechnology has enabled the production of metallic or nonmetallic nanoparticles with average crystallite sizes below 100 nm. The mechanical, optical, electrical, magnetic, and thermal properties of nanoparticles are superior to those of conventional bulk materials with coarse grain structures. Nanofluids are a new class of nanotechnology-based heat transfer fluids engineered by dispersing nanometer-sized particles with typical length scales on the order of 1–100 nm in traditional heat transfer fluids. Due to their large surface area, less particle momentum, and high mobility, nanoparticles emerged as suitable candidates for suspending in fluids. Nanofluid are used in cooling and related technology overcoming the usual problems with common slurries such as sedimentation, clogging, increased pressure drop, erosion, and applicability to micro-channels. Nanofluids of ceramic and pure metallic particles have been produced by the conventional two-step method where the particles are first produced by methods such as IGC or chemical vapor deposition and then the particles are dispersed in the fluid using various methods such as physical dispersion and chemical dispersion methods where various techniques such as ultrasonic vibration, use of surfactants, or control of pH can be used. For measuring thermal conductivity of nanofluids, the very first need is to standardize the measurement techniques. The observed enhancement of effective thermal conductivity over that of the base fluid is often few times for nanofluid compared to what would have been given by usual micrometer-sized suspensions. The chapter also discusses issues, such as convection in nanofluids, boiling in nanofluids, studies on critical heat flux in pool boiling, and applications of nanofluids.