Enhanced heat and mass transfer in solar stills using nanofluids: A review

•Nanofluids benefits in heat engineering applications.•Improving the main mechanisms in solar distillation by means of nanofluids.•Identification of nanofluids key parameters in solar distillation.•Perspectives with nanofluids: challenge in direct desalination systems. The current paper reviews a comprehensive outlook about the role of nanofluids in many fields especially in solar energy desalination technologies. Benefits of using nanofluids were highlighted from the angle of their positive effects on the solar stills (direct solar distillation) thermal performances improvement with acceptable consequences. Undoubtedly, nanofluids showed relevant characteristics and a promising large applicability, based on enhancement of thermal conductivity in comparison to basefluids free from additional metal or metal oxide nanoscaled particles. The behaviors of nanofluids in such configurations were deeply weighed up mainly by means of the experimental investigations issued from the open literature. An attempt based on critical analysis has been carried out to confront the different results. The plan of this review consists of exhibiting the performed researches through several facets, mainly objectivity of the studies and the results, mathematical models and data measurements. It was observed within the foregoing contributions many stagnant issues that should be taken into account, namely few works have analyzed nanofluids in solar still active configurations. Moreover, further investigations are required to examine the effects of nanoparticle size, shape of the nano grain, amount of the nanoparticles, stability of the nanofluids and the dispersion procedure.