Progress in the enhancement of gas–liquid mass transfer by porous nanoparticle nanofluids

Nanofluids are a new mass transfer enhancement technology can effectively reduce mass transfer resistance, improve gas–liquid mass transfer rate and enhance absorption process. Using nanoparticles to enhance gas–liquid mass transfer could greatly reduce energy consumption, equipment size and industrial production costs. Different from traditional nanoparticles, this paper reviews the research results of gas–liquid mass transfer and the influence of porous nanoparticles for the first time. The gas–liquid mass transfer of nanofluids was related to the amount added, type, scale, morphology and surface functionalization of the nanoparticle. Transfer was also related to the physicochemical properties of base fluids and the strengthening sites. Enhancement mechanisms such as grazing effect, hydrodynamic action and the prevention of bubble coalescence were elaborated upon. Several research methods and related mathematical models were briefly introduced. Nonetheless, current research in this area is still in its infancy, so it is necessary to strengthen microscopic visualization and mathematical model research for future improvements in this area. The molecular mass simulation and collision theory should be used to quantitatively reveal the internal mass and energy transfer processes of nanofluids.