The hybrid nanofluids are novel nanofluids and can be prepared by suspending various kinds of nanoparticles in base fluid. In this paper, an experimental investigation on the effects of temperature and nanoparticles concentration on the thermal conductivity of ZnO–TiO2/EG hybrid nanofluids is presented. The experiments were implemented at temperature ranging from 25 to 50 °C and solid volume fraction range of 0–3.5 %. Experiments indicate that the thermal conductivity enhances with increasing the solid volume fraction and temperature. It was found that the variation of thermal conductivity enhancement of nanofluids with solid volume fraction at higher temperatures is greater than that at lower temperature. Moreover, it can be also seen that the variation of thermal conductivity enhancement of nanofluids with temperature at higher solid volume fraction is more than that at lower solid volume fraction. Finally, based on experimental data, in order to predict the thermal conductivity ratio of ZnO–TiO2/EG hybrid nanofluids, a correlation was proposed. Deviation analysis of the thermal conductivity ratio was also performed. Comparison between experimental data and the proposed correlation outputs revealed that this correlation has a good accuracy.

Measurement of thermal conductivity of ZnO–TiO 2 /EG hybrid nanofluid

A review of recent advances in thermophysical properties at the nanoscale: From solid state to colloids

A comprehensive review of research and development on rheological characteristics of nanofluids for their advanced heat transfer applications is performed and reported in this paper. It identifies the research anomaly and importance on this topic besides analysing rheology of nanofluids. Various classical and recently developed viscosity models for nanofluids are presented and discussed. Nanofluids are classified as metallic and nonmetallic types and research findings on this key property of available nanofluids are analyzed. Effects of several important factors such as concentration of nanoparticles and temperature on viscosity of each type of nanofluids have been explicitly reviewed. Results from various research groups and predictions from viscosity models are also compared and discussed in detail. Role and importance of the viscosity in connection with other thermal properties and parameters for their thermal management applications are highlighted. Furthermore, the research challenges and needs in this important area of nanofluids are also revealed.

A state of the art review on viscosity of nanofluids

Experimental study on thermal conductivity of ethylene glycol containing hybrid nano-additives and development of a new correlation

Viscosity of nanofluids: A review of recent experimental studies

The viscosity and thermal conductivity of ZnO nanofluids with nanoparticle shapes of nearly rectangular and of sphere, were experimentally investigated under various volume concentrations of the nanoparticles, ranging from 0.05 to 5.0 vol.%. The viscosity of the nanofluids increased with increases in the volume concentration by up to 69%. In addition, the enhancement of the viscosity of the nearly rectangular shape nanoparticles was found to be greater by 7.7%, than that of the spherical nanoparticles. The thermal conductivity of the ZnO nanofluids increased by up to 12% and 18% at 5.0 vol.% for the spherical and the nearly rectangular shape nanoparticles, respectively, compared to that of the base fluid (water). The shape of the particles is found to have a significant effect on the viscosity and thermal conductivity enhancements.

Particle shape effect on the viscosity and thermal conductivity of ZnO nanofluids

A standard cooling rate has not been established for glazing; therefore, the effects of the cooling rate on the properties of zirconia need to be evaluated to predict outcomes in clinical practice. 4Y-TZP glazed at three different cooling rates was analyzed to estimate the effect of cooling rate during glazing on the mechanical and optical properties. Hardness tests, field-emission scanning electron microscopy analysis, X-ray diffraction analysis, flexural strength measurement, and optical property evaluations were performed. When 4Y-TZP was glazed at a higher cooling rate (Cooling-1) than the normal cooling rate (Cooling-2), there was no significant difference in grain size, flexural strength, average transmittance, and translucency parameters. The hardness was slightly reduced. The opalescence parameter was reduced for the 2.03 mm thick specimens. When 4Y-TZP was glazed at a lower cooling rate (Cooling-3) than the normal cooling rate, there was no significant difference in hardness, grain size, flexural strength, and translucency parameters. In addition, the average transmittance and opalescence parameters were slightly reduced for the 0.52 and 2.03 mm specimens, respectively. The effects of the cooling rate during glazing on the mechanical and optical properties of 4Y-TZP appear to be minimal and clinically insignificant. Therefore, even if the cooling rate cannot be strictly controlled during glazing, the clinical outcomes will not be significantly affected.

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Jisun Jeong

Papers

Particle shape effect on the viscosity and thermal conductivity of ZnO nanofluids

Effect of Cooling Rate on Mechanical Properties, Translucency, Opalescence, and Light Transmission Properties of Monolithic 4Y-TZP during Glazing