Nanofluid

About: Nanofluid is a research topic. Over the lifetime, 23986 publications have been published within this topic receiving 677384 citations.

Free Convection in a Square Cavity Filled with a Porous Medium Saturated by Nanofluid Using Tiwari and Das’ Nanofluid Model

Abstract: Free convection in a square differentially heated porous cavity filled with a nanofluid is numerically investigated. The mathematical model has been formulated in dimensionless stream function and temperature taking into account the Darcy–Boussinesq approximation. The Tiwari and Das’ nanofluid model with new more realistic empirical correlations for the physical properties of the nanofluids has been used for numerical analysis. The governing equations have been solved numerically on the basis of a second-order accurate finite difference method. The developed algorithm has been validated by direct comparisons with previously published papers and the results have been found to be in good agreement. The results have been presented in terms of the streamlines, isotherms, local, and average Nusselt numbers at left vertical wall at a wide range of key parameters.

Application of hybrid sphere/carbon nanotube particles in nanofluids

Abstract: Previous studies on nanofluids have focused on spherical or long-fibre particles. In this work, a new type of complex nanoparticle—a hybrid sphere/carbon nanotube(CNT) particle, consisting of numerous CNTs attached to an alumina/iron oxide sphere—is proposed for applications in nanofluids. In such hybrid nanoparticles, heat is expected to transport rapidly from one CNT to another through the centre sphere and thus leading to less thermal contact resistance between CNTs when compared to simple CNTs dispersed in fluids. CNTs have an extremely high thermal conductivity, but thermal resistance between the CNTs and the fluid has limited their performance in nanofluids. The proposed hybrid sphere/CNT particles are synthesized by spray pyrolysis followed by catalytic growth of CNTs. The spheres are about 70 nm in diameter on average, and the attached CNTs have a length up to 2 µm. These hybrid nanoparticles are dispersed to poly-alpha-olefin with sonication and a small amount of surfactants to form stable nanofluids. The thermal conductivity of the fluids has been measured by a 3ω-wire method over a temperature range 10–90 °C. The results indicate that the effective thermal conductivity of the fluids is increased by about 21% at room temperature for particle volume fractions of 0.2%.

Model for the effective thermal conductivity of carbon nanotube composites.

Abstract: We present a novel model of the effective thermal conductivity for carbon nanotube composites by incorporating the interface thermal resistance with an average polarization theory. The dependence of the effective thermal conductivity on nanotube length, diameter, concentration, and interface thermal resistance has been taken care of simultaneously in our treatment. The model predicts that the large length of the carbon nanotubes embedded plays a key role in the thermal conductivity enhancement, while the large interface thermal resistance across the nanotube-matrix interface causes a significant degradation. Interestingly, the model predicts that the nanotube diameter has a very small effect on the thermal conductivity enhancement of the nanotube composites. In addition, the model predicts that the thermal conductivity enhancement of nanotube composites increases rapidly with decreasing the thermal conductivity of the matrix and increases with increasing the thermal conductivity of the carbon nanotube. Predictions from the novel model are in excellent agreement with the experimentally observed values of the effective thermal conductivity of carbon nanotube nanofluids which the classical models have not been able to explain.