Synthesis, stability, thermophysical properties and heat transfer applications of nanofluid – A review

• A systematic review of stability and their influence on thermophysical properties of nanofluids is presented. • The review found that the volume fraction and particle size significantly affects thermophysical properties of nanofluids. • It provides precise instructions for synthesis, characterization, and assessment of nanofluid thermophysical characteristics. Nanofluid has been found exceptionally suitable in several heat transfer applications as a working fluid due to its excellent thermophysical properties. Enhancement in thermophysical properties of nanofluid is strongly influenced by its long-term stability. Several parameters such as base fluid type, nanoparticle type, surfactant type, nanoparticle size and morphology, preparation method, and pH of the synthesized fluid affect nanofluid stability. This article addresses a detailed review of synthesis techniques, stability evaluation, enhancement techniques, and parametric effect on the stability of nanofluid. The article also includes a systematic review of various thermophysical properties of mono, hybrid, and ternary nanofluid and the influence of several parameters on thermophysical properties of nanofluid. Volume fraction and particle size significantly enhanced several thermophysical properties such as thermal conductivity and viscosity. However, results reported by researchers were inconsistent and conflicting, which needs further investigation. The article also reviews nanofluid suitability in various heat transfer applications such as solar collectors, electronic cooling, refrigeration systems, solar distillation system, two-phase heat transfer, and heat exchangers. Nanofluids were found suitable and demonstrated improvement in the performance of the system. A review of the economic analysis of nanofluid has also been included in the article. Stable synthesized nanofluid demonstrates its economic suitability, which ultimately translates nanofluid research from lab scale to commercial utilization. Researchers could benefit from the explicit guidelines provided by the current study for the synthesis, characterization, and assessment of the thermophysical properties of mono and hybrid nanofluids.