Heat transfer augmentation techniques used to add solid particles as an additive to fluids. This approach is over 100 years old but has fallen out of favor in recent years. While effective, using solid particles as additives created nearly as many problems as they solved: Erosion; Fouling; Pressure Drop; and Sedimentation.
More recent advances in materials and nanotechnology provide a better alternative: nanometer-size particles. Innovative heat transfer fluids suspended by nanometer-sized solid particles are named nanofluids. They are believed to be pioneered by Choi. Although, some credit other voices that were first discovered in China a few years before Choi published its first material on this. 1995 was the year that nanofluids appeared as a pioneering research idea. Since then great efforts have been made to advance the knowledge on heat transfer fluids enhanced with nanoparticles.