Investigation of the influence of Fe3O4-water nanofluids on capillary performance in microgrooves wick

Abstract

Abstract In this work, aqueous nanofluids of Fe3O4 nanoparticles were used to enhance the capillary performance in microgrooves wick in terms of increasing the capillary pressure and the wick permeability. The influence of the nanofluids on the capillary performance was evaluated by the capillary-rise experiment. During the experiment, temperatures of the liquid pool and the wick were separately controlled to test it at ambient temperature and 40 oC. The percentage increase of the Capillary Performance Parameter can be ranged from 8 to 75 %, compared with the base liquid. There exists an optimal concentration to maximize the enhancement. It has been suggested that nanofluids rely on the particles trapped in the evaporating thin-film region of the meniscus to improve surface wetting by forming the structural disjoining pressure and those absorbed on a channel surface to reduce skin friction through inducing slip flow at the boundary. It is found in this work that the elevated temperature can facilitate the nanofluids to improve surface wetting in microgroove but hamper the friction reduction and too high concentration harms both. The fundamental mechanism is analyzed based on the discussions of particle migrations toward the thin-film region and the groove surface as well as the effect of particle aggregation at two temperatures.