Abstract
Nanofluids (NFs) synthesized via the suspension of diverse nanoparticles into conventional thermal fluids are known to exhibit better thermal, optical, tribological, and convective properties, photothermal conversion, and heat transfer performance in comparison with traditional thermal fluids. Stability is pivotal to NF preparation, properties, performance, and application. NF preparation is not as easy as it appears, but complex in that obtaining a stable NF comes with the harnessing of different preparation parameters. These parameters include stirring duration and speed, volume, density, base fluid type, weight/volume concentration, density, nano-size, type of mono or hybrid nanoparticles used, type and quantity of surfactant used, and sonication time, temperature, mode, frequency, and amplitude. The effect of these preparation parameters on the stability of mono and hybrid NFs consequently affects the thermal, optical, rheological, and convective properties, and photothermal conversion and heat transfer performances of NFs in various applications. A comprehensive overview of the influence of these preparation characteristics on the thermal, optical, rheological, and properties, photothermal conversion, and heat transfer performance is presented in this paper. This is imperative due to the extensive study on mono and hybrid NFs and their acceptance as advanced thermal fluids along with the critical importance of stability to their properties and performance. The various preparation, characterization, and stability methods deployed in NF studies have been compiled and discussed herein. In addition, the effect of the various preparation characteristics on the properties (thermal, optical, rheological, and convective), photothermal conversion, and heat transfer performances of mono and hybrid NFs have been reviewed. The need to achieve optimum stability of NFs by optimizing the preparation characteristics is observed to be critical to the obtained results for the properties, photothermal conversion, and heat transfer performance studies. As noticed that the preparation characteristics data are not detailed in most of the published works and thus making it mostly impossible to reproduce NF experimental studies, stability, and results; future research is expected to address this gap. In addition, the research community should be concerned about the aging and reusability of NFs (mono and hybrid) in the nearest future.