Nanofluids thermal performance in the horizontal annular passages: a recent comprehensive review

Nanofluids are prepared to enrich thermo-physical and convective heat transfer properties by suspending nanometer particles in a base fluid. For different nanoparticles concentrations, several investigations on heat transfer and flow characteristics were conducted experimentally and numerically for annular passages of various geometrical cross-sections to enhance the convection heat transfer and minimize the friction loss. This paper summarises the preparation methods, functionalization techniques, nanofluids stability and the different methods of characterization and nanofluids thermophysical properties evaluation. Moreover, the current review summarises the experimental and numerical work related to the heat transfer and friction loss in the horizontal annuli of different cross-sectional geometries. The most extensively equations used to predict the effective nanofluids thermophysical properties were presented as well.