In this context,a detailed review of nanofluid research works assumes a great significance as it would facilitate there searchers to update the recent developments and realize the potential research gap in the field of nanofluid. This paper focuses on the existing knowledge and research gap in all fields of nanofluids from synthesis of metallic and nonmetallic nanofluids and hybrid nanofluids to the application of nanofluid. An exclusive review section on characterization techniques,improved and recent theoretical models for thermal conductivity,viscosity and specific heat developed by different researchers are presented and major applications areas of nanofluids are discussed in this review paper.
Nanofluid is found to be a potential candidate for many applications. However,there are still many challenges that need to be overcome. These challenges include the long term stability of nanoparticle dispersions,increased pressure drop,pumping power requirements,nanofluid thermal performance in turbulent flow and in fully developed flow regions,higher viscosity,lower specific heat, thermal conductivity,high production cost,and difficulties in
production processes. Especially,nanofluid stability and production costs are obstacles for the commercialization of nanofluids. A discussion on challenges of nanofluids is included in this review paper.