A comprehensive review on advances of oil-based nanofluids for concentrating solar thermal collector application

Nanofluids have exhibited noteworthy advancement as efficient working fluids in the last decade towards the field of solar energy conversion field to deal with escalating global energy demand. Research developments on thermo-physical, long-term stability and rheology are moving ahead to achieve practical deployment in renewable solar photo-thermal conversion sectors (i.e., solar collectors). Nevertheless, researchers and engineers are encountering many difficulties dealing with nearly infinite culpable variables impacting performance of several categories of NFs. This work attempts to offer an up-to-date review on advances and challenges of oil-based nanofluids focusing on formulation, key properties (stability, thermal conductivity, cp, and viscosity) and effective implementation in concentrating solar collector devices. Previous experimental and numerical studies on the topics are compiled and acutely scrutinized providing essential phenomena, mechanisms, shortcomings, responsible parameters to obtain stable and optimized thermal properties integrating with heat transfer performance. It is observed that optimization of the critical factors leads to superior behavior of the nanofluids, which in turns generates enhanced thermal performance of the solar collectors. Lastly, existing challenges are reported along with recommendations to address the issues for further developments in the field which would mobilize rapid innovation and practical engineering practice of nanofluids