A review of influence of nanoparticle synthesis and geometrical parameters on thermophysical properties and stability of nanofluids

After the advent of nanofluids, researchers across the world are actively engaged in carrying out experimental research works on nanofluids for heat transfer applications such as heat exchangers, electronic cooling, etc. Nanofluids are also used as working fluid in the renewable energy systems such as solar collectors, solar still, solar cells and solar ponds to harvest the solar energy to the maximum extent. Application of nanofluid in heat transfer systems is proved to enhance the heat transfer characteristics of base working fluid, which led to the reduction of area, materials and size of heat transfer systems. Existence of nanoparticle in nanofluid enhances the thermo-physical properties of the base fluid and hence higher rate of heat transfer as compared to base fluid. This research review article provides as much as comparative researches done on preparation, the effect of size and shape on thermo-physical properties, and the characterization techniques and stability of nanofluids. From the extensive review of comparative studies, first of its kind, it is found that among the several parameters, the size and shape of nanoparticle and the sonication process highly influence the enhancement in both thermo-physical properties and stability of the nanofluid. But the size and shape of nanoparticle depends mainly on synthesis of the nanoparticle. Further, the stability of the nanofluid is highly influenced by the surface charge of the nanoparticle, which depends on sonication process. Hence, the synthesis of nanoparticle and the sonication process are the key parameters to enhance thermophysical properties and stability of the nanofluid. This review would enable the researchers to understand the key parameters and their effects on the thermophysical properties and stability of nanofluids and to prepare effective and stable nanofluids for maximizing the heat transfer rate and effectiveness of thermal energy conversion systems such as heat exchangers, solar thermal collectors, etc.