Modelling the thermal conductivity of nanofluids
The interaction of nano particulates with conventional materials generally has the effect of dramatically changing all the physical parameters of the material, which normally characterize the bulk material. The nanoparticles themselves constitute highly reactive isolated sites, to the extent that the electronic structure of the nano composite is changed, and accordingly all the physical properties, such as thermal, mechanical, electrical, magnetic and optical become different from those of the bulk materials. In fact generally, the smaller the particles, the greater the quantum effects, which means greater changes to the bulk physical properties of the nano-composite, and this phenomenon is widely accepted as not being properly understood. Nanofluids are simply standard fluids such as water, engine oil, ethylene glycol and toluene, but including a small volume percentage, usually less than 5% of evenly dispersed nanoparticles, which are usually metallic. In this paper, we present a survey of some of the attempts to model the enhanced thermal conductivity of such nanofluids, and address issues such as the nanoparticles themselves, the surrounding layer, cluster structure, the fluid environment, and the different heat transport processes at the micro and nano scales.