Thermal Conductivity of Nanofluids: Review

Conventional heat transfer fluids, such as mineral oil, water, and ethylene glycol, have poor heat transfer properties compared with solids. The methods to enhance the efficacy of heat transfer fluids have been of great interest to scientists and engineers for the past two decades. Recently, nanofluids are being considered as potential heat transfer fluids. A nanofluid is a suspension of nanometer-sized materials, with or without surface-active agents. In general the thermal conductivity of suspended nanometer-sized particles is higher than the base fluids. Oxides, metals, nitrides and nonmetals like carbon nanotubes and graphene are used as nanomaterials in nanofluids, while water, ethylene glycol, oils, and polymer solutions are used as base fluids. This review has two main goals; the first one is to summarize the recent studies of using metal and nonmetal nanoparticle to improve the thermal conductivity of nanofluids. The second goal is to highlight the effect of using magnetic field to enhance the thermal conductivity of the nanofluids.