Hysteresis Phenomenon on Water-Based Nanofluid Viscosity
نویسندگان
چکیده
Dynamic viscosity values for three particular water-based nanofluids have been experimental determined using a commercial ‘piston-type’ viscometer. Viscosity data, expressed as a function of temperature and particle volume fraction, are presented for 29nm particle-size CuO-water and Al2O3-water with 36nm and 47nm particle-sizes, temperatures up to 75°C and particle volume fraction up to 9%. In general, the nanofluid viscosity increases considerably with an increase of particle volume fraction but decreases with increasing temperature. The existence of a critical temperature has been clearly established, beyond which the hysteresis behaviour on viscosity has been observed. Such a critical temperature has been found strongly dependent on both particle volume fraction and size. This hysteresis phenomenon has raised major concerns regarding the use of nanofluids for the heat transfer enhancement purposes. Key-Words: Water-based nanofluids, Al2O3-Water, CuO-Water, Alumina nanoparticles, Copper-oxide nanoparticles, Experimental study, Dynamic viscosity, Hysteresis.
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