ABSTRACT
Heat transfer enhancement is critically important in improving the efficiency of energy system. Many technologies have been developed, aiming at high heat transfer rate as well as at low cost. One of the most important techniques is to improve the thermal properties of heat transfer fluids. The traditional heat transfer fluids, such as water, oil, and ethylene glycol (EG), have relatively poor heat transfer performance due to their lower thermal conductivities compared with those of solid materials, and it is an innovative idea to enhance the thermal conductivity of heat transfer fluid by adding solid metallic or nonmetallic particles. However, when the micrometer or even millimeter particles were added into the base fluid, they caused abrasion of surface, clogging the microchannels, eroding the pipeline, and increasing the pressure drop, thus limited the practical applications. With the advances in nanotechnology, both metallic and nonmetallic nanosized particles are produced. The nanoparticles have unique mechanical and thermal properties compared with their bulk counterparts. The heat transfer fluids dispersed with nanoparticles are more stable under static conditions, thus are promising for practical applications without causing the problems mentioned before.
