The thermal conductivity of heating or cooling fluids is a very important property in the development of energy-efficient heat transfer systems. In all processes involving heat transfer, the thermal conductivity of the fluids is one of the basic properties taken account in designing and controlling the process. However, the traditional pure liquid heat transfer medium has a low thermal conductivity, which limits the heat transfer enhancement. Therefore, it is necessary to prepare a higher thermal conductivity and more efficient heat transfer medium. Scientific breakthrough has been made by Choi in 1995 when for the first time he introduced the term “Nanofluids”. Nanofluids are a new class of heat transfer fluids with substantially higher conductivities. These fluids are developed by suspending nanoscale metallic or nonmetallic particles in the base fluid.