Stability and rheology of dilute TiO2-water nanofluids

Abstract

The apparent wall slip (AWS) effect, accompanying the flow of colloidal dispersions in confined geometries, can be an important factor for the applications of nanofluids in heat transfer and microfluidics. In this study, a series of dilute TiO2 aqueous dispersions were prepared and tested for the possible presence of the AWS effect by means of a novel viscometric technique. The nanofluids, prepared from TiO2 rutile or anatase nanopowders by ultrasonic dispersing in water, were stabilized by adjusting the pH to the maximum zeta potential. The resulting stable nanofluid samples were dilute, below 0.7 vol.%. All the samples manifest Newtonian behavior with the fluidities almost unaffected by the presence of the dispersed phase. No case of important slip contribution was detected: the Navier slip coefficient of approximately 2 mm Pa-1 s-1 would affect the apparent fluidity data in a 100-μm gap by less than 1%.

Rheological behaviour of nanofluids: A review

“…Richmond et al [62] have found that mixing of TiO 2 in SiO 2 /water nanofluid changes its flow behaviour from Newtonian to non-Newtonian. One can conclude that except for the behaviour as observed by Penkavova et al [71], the TiO 2 /water nanofluid shows shear thinning behaviour [63,64,[67][68]. The TiO 2 /EG nanofluid exhibits Newtonian behaviour even for high shear rate.…”

“…The rheological behaviour can be measured by rheometers [64][65][66][67][68]70,72]. Some researchers [62][63]69,71] have used viscometers to measure the viscosity. Nowadays viscometers are considered inadequate as they are not capable to read the feature of shear dependence, especially for low viscosity liquid-based nanofluids containing non-spherical particles.…”

Mechanism governing nanoparticle flow behaviour in porous media: insight for enhanced oil recovery applications

“…But upon exceeding a shear rate of 100 s −1 , it showed a Newtonian behaviour [103]. Alphonse et al, [107] and Penkavova et al [108] on the other hand reported a Newtonian behaviour for TiO 2 with water at low shear rate and changed to shear thinning when the shear rate exceeded 100 s −1.…”

Influence of the geometry of cylindrical enclosure on natural convection heat transfer of Newtonian nanofluids

“…Highly linear trends achieved in this work confirmed the Newtonian behavior of Al 2 O 3 /water nano-fluid. Newtonian behavior of TiO 2 /water was also approved in a study by Penkavova et al (2011). (5) Data acquisition.…”