Transformer oil-based nanofluid: The application of nanomaterials on thermal, electrical and physicochemical properties of liquid insulation-A review

Abstract This century is undergoing a wave of knowledge and inventions making use of exceptional properties of nanofluids (NFs) in applications such as manufacturing and process heating, air conditioning and refrigeration systems, solar energy, heat pipes, electrical cooling systems and many others. Research investigations about NFs are on the increase due to growing attention and demand for NFs as heat transfer fluids. This can be observed from the number of articles published. To endorse the field further, the objective of this study is threefold. First, it presents the literature that specifies the preparation of NFs which are developed by the suspending of solid nanoparticles (NPs) in conventional working liquids. Secondly, it offers contemporary research on thermophysical features results of NFs. In this review, which primarily emphasizes research carried out in the last couple of decades, experimental inquiries from the latest developments of NFs applications and performance as a heat transfer system are summarized. Moreover, heat transfer mechanisms, challenges and impeding trends associated with NFs regarding heat transfer improvement are deliberated; which must motivate additional exploration. This analysis also deliberates numerous dynamics affecting the thermophysical features; comprising of synthesis techniques, the stability of NFs, various base fluids, type, size, shape, surface modification and volume fraction of nanoparticles (NPs). Though, there are inconsistent findings have been observed in the literature on the effect of factors on the thermophysical traits of NFs. The study also discovers that appropriate characterization of NFs may result in superior heat transfer fluids compared to conventional base fluids. Nevertheless, more extreme exploration is required towards the suitable selection of NPs, their synthesis, characterization and long-term stability of NF is essential to exploit their full potential along with the application of these innovative fluids on commercial levels. The stability of NFs is likewise a fundamental feature of their sustainability and effectiveness. Both academia and professionals in the industry possibly will find this review valuable, as it summarizes significant outlines of research in the field.