Convection in nanofluids with a particle-concentration-dependent thermal conductivity

This paper reports an experimental study of thermal conductivity of room temperature ionic liquids (RTILs) based magnetic nanofluids. Various magnetic nanoparticles of metal oxides with high thermal conductivity, such as CuO, Al2O3, Fe3O4 and Carbon Nano Tubes (CNTs), were used to prepare magnetic nanofluids, while RTIL, trihexyl (tetradecyl) posphonium dicyanamide was used as the base fluid. Two major parameters that affect to the thermal conductivity enhancement of fluids were investigated. The effect of particle concentration and external magnetic fields were tested. It was observed that the magnetic nanofluids thermal conductivities increase with increment of particle concentration and external magnetic field parallel to the temperature gradient. Besides, it was observed that under higher magnetic fields, thermal conductivity enhancement tends to approach a saturation state. Surfactant was used to disperse magnetic nanoparticles within the RTILs. The transient hot wire method was used for this investigation.

Download Full-text

Influence of particle concentration and temperature on thermal conductivity and viscosity of Al2O3/R141b nanorefrigerant

International Communications in Heat and Mass Transfer ◽

10.1016/j.icheatmasstransfer.2013.02.004 ◽

2013 ◽

Vol 43 ◽

pp. 100-104 ◽

Cited By ~ 84

Author(s):

I.M. Mahbubul ◽

R. Saidur ◽

M.A. Amalina

Keyword(s):

Thermal Conductivity ◽

Particle Concentration

Download Full-text

Statistical analysis of thermal conductivity experimentally measured in water-based nanofluids

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2021.0222 ◽

2021 ◽

Vol 477 (2250) ◽

pp. 20210222

Author(s):

J. Tielke ◽

M. Maas ◽

M. Castillo ◽

K. Rezwan ◽

M. Avila

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Particle Size ◽

Particle Concentration ◽

Statistical Correlation ◽

Large Scatter ◽

Water Based ◽

Homogeneous Media ◽

Measured Thermal Conductivity ◽

Specific Particle

Nanofluids are suspensions of nanoparticles in a base heat-transfer liquid. They have been widely investigated to boost heat transfer since they were proposed in the 1990s. We present a statistical correlation analysis of experimentally measured thermal conductivity of water-based nanofluids available in the literature. The influences of particle concentration, particle size, temperature and surfactants are investigated. For specific particle materials (alumina, titania, copper oxide, copper, silica and silicon carbide), separate analyses are performed. The conductivity increases with the concentration in qualitative agreement with Maxwell’s theory of homogeneous media. The conductivity also increases with the temperature (in addition to the improvement due to the increased conductivity of water). Surprisingly, only silica nanofluids exhibit a statistically significant effect of the particle size, whereby smaller particles lead to faster heat transfer. Overall, the large scatter in the experimental data prevents a compelling, unambiguous assessment of these effects. Taken together, the results of our analysis suggest that more comprehensive experimental characterizations of nanofluids are necessary to estimate their practical potential.

Download Full-text

Investigation of Thermal Conductivity and Viscosity of Al2O3/Water Nanofluids Using Full Factorial Design and Utility Concept

NANO ◽

10.1142/s1793292016500934 ◽

2016 ◽

Vol 11 (08) ◽

pp. 1650093 ◽

Cited By ~ 8

Author(s):

Deepak Khurana ◽

Rajesh Choudhary ◽

Sudhakar Subudhi

Keyword(s):

Thermal Conductivity ◽

Factorial Design ◽

Particle Concentration ◽

Heat Transfer Performance ◽

Particle Diameter ◽

Full Factorial Design ◽

Utility Concept ◽

Low Viscosity ◽

Design Variables ◽

Full Factorial

In the present study, the effect of particle concentration, particle diameter and temperature on the thermal conductivity and viscosity of Al2O3/water nanofluids was investigated experimentally using design of experiment approach (full factorial design). Variables were selected at two levels each: particle concentration (0.1–1%), particle diameter (20–40[Formula: see text]nm) and temperature (10–40[Formula: see text]C). It was observed that the thermal conductivity of the Al2O3/water nanofluids increases with increasing concentration and temperature and decreases with increase in particle diameter, while viscosity increases with increasing particle diameter. Results showed that the interaction effect of concentration and temperature also has significant effect on the thermal conductivity of Al2O3/water nanofluids. For viscosity, the interaction of particle diameter and temperature was important. Utility concept was used to optimize the properties collectively for better heat transfer performance. The optimal combination for high thermal conductivity and low viscosity was obtained at higher level of particle concentration (1%), lower level of particle diameter (20[Formula: see text]nm) and higher level of temperature (40[Formula: see text]C). At this condition the increment in thermal conductivity and viscosity compared to base fluid was 11.51% and 6.37%, respectively.

Download Full-text