Stability of Nanofluids: Fundamentals, State-of-the-Art, and Potential Applications

Nanofluids as defined by Choi and Eastman [1] are an “innovative new class of heat transfer fluids, " which “can be engineered by suspending metallic nanoparticles in conventional heat transfer fluids.” Generally speaking, nanofluids are colloidal dispersions of differently shaped (e.g., spherical, cylindrical, rod-like, etc.) nanoparticles (e.g., Al, Al2O3, Cu, CuO, Au, Ag, SiO2, TiO2, and carbon nanotubes [CNTs]) within base fluids (conventional coolants such as deionized water, engine oil, since 1990s, mainly due to their improved thermophysical properties, such as thermal conductivity, and specific heat. It is critical to sustain the improved characteristics, in order to utilize nanofluids reliably in all potential applications, including heat transfer enhancement.