ABSTRACT
A stable dispersion of nanometer-sized materials in base fluids have been termed as “nanofluids” by S. U. S. Choi in 1995. This chapter discusses the progress in the methods for preparing stable nanofluids. Nanofluids have been found to possess enhanced thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity, and convective heat transfer coefficients compared to those of pristine base fluids like oil or water. High pressure/shear homogenization method is more efficient to break the agglomerates of nanoparticles in the nanofluid due to the combined effects of cavitation and high shear force than ultrasonication. Since the repulsive force between nanoparticle (NP) is strongly influenced by the concentration of surface charge, electrostatic stabilization is a facile way to enhance the stability of nanofluids. Chemical and mechanical treatments have been shown to be effective to disentangle the NP aggregates and to enhance the dispersibility of NPs for preparing homogeneous and stable nanofluids.
