Showing papers on "Nanofluid published in 2016"

A review on preparation, characterization, properties and applications of nanofluids

Abstract: Selection of suitable heat transfer fluid for heat dissipation is an important consideration in the design of heat exchanging systems. Nanofluid, a colloidal mixture made of a base fluid and a nanoparticle, is a new generation of heat transfer fluids becoming a high potential fluid in heat transfer applications due to enhanced thermal conductivity. Research studies about nanofluids are on the rise owing to the mounting interest and demand for nanofluids as heat transfer fluids in a wide variety of applications. Recently, nanofluid technology has a new dimension of impregnating two or more nanoparticles in base fluids, namely hybrid or composite nanofluids. This paper reviews the preparation of metal and metal oxides nanofluids and hybrid nanofluids and the various techniques used to study the physical and chemical characteristics of nanofluids. Thermo-physical and heat transfer properties of nanofluids including the improved thermal conductivity, viscosity and specific heat models for nanofluids are presented. Finally, various application areas of nanofluids, such as transportation, electronic cooling, energy storage, mechanical applications etc. are discussed.

Numerical Investigation of Hydromagnetic Hybrid Cu – Al2O3/Water Nanofluid Flow over a Permeable Stretching Sheet with Suction

Abstract: Abstract An emerging concept of hybrid nanofluid with a new improved model of its thermophysical properties are introduced in the present work. Hybrid nanofluid is an advanced type of conventional heat transfer fluids, which has been employed for the enhancement of heat transfer rate. Two distinct fluids, namely hybrid nanofluid (Cu−Al2O3/water)$({\\rm{Cu - A}}{{\\rm{l}}_{\\rm{2}}}{{\\rm{O}}_{\\rm{3}}}{\\rm{/water}})$ and nanofluid (Cu/water) are used to investigate the parametric features of the flow and heat transfer phenomena over a permeable stretching sheet in the presence of magnetic field. The effects of various physical parameters and effecting physical quantities of interest are analyzed. From this study it is observed that the heat transfer rate of hybrid nanofluid (Cu−Al2O3/water)$({\\rm{Cu - A}}{{\\rm{l}}_{\\rm{2}}}{{\\rm{O}}_{\\rm{3}}}{\\rm{/water}})$ is higher than that of Nanofluid (Cu/water) under magnetic field environment. More combinations of different nanocomposites can be tried so that the desired heat transfer rate can be achieved.

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

Abstract: 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.

Nanofluid convective heat transfer using semi analytical and numerical approaches: A review

Abstract: The use of additives in the base fluid like water or ethylene glycol is one of the techniques applied to augment the heat transfer. Newly an innovative nanometer sized particles have been dispersed in the base fluid in heat transfer fluids. The fluids containing the solid nanometer size particle dispersion are called ‘nanofluids’. Two main categories were discussed in detail as the single-phase modeling which the combination of nanoparticle and base fluid is considered as a single-phase mixture with steady properties and the two-phase modeling in which the nanoparticle properties and behaviors are considered separately from the base fluid properties and behaviors. Both single phase and two phase models have been presented in this paper. This paper intends to provide a brief review of researches on nanofluid flow and heat transfer via semi analytical and numerical methods. It was also found that Nusselt number is an increasing function of nanoparticle volume fraction, Rayleigh number and Reynolds number, while it is a decreasing function of Hartmann number.

Numerical investigation of three-dimensional hybrid Cu–Al2O3/water nanofluid flow over a stretching sheet with effecting Lorentz force subject to Newtonian heating

Abstract: This work compares the heat transfer characteristics of traditional nanofluid with that of emerging hybrid nanofluid. Hybrid nanofluid, a new type of conventional fluid, has been used toward the en...

Melting heat transfer on hydromagnetic flow of a nanofluid over a stretching sheet with radiation and second-order slip

Abstract: The present paper is devoted to the analysis of MHD flow and melting heat transfer of a nanofluid over a stretching surface taking into account a second-order slip model and thermal radiation. Similarity solutions for the transformed governing equations are obtained. The reduced equations are solved numerically by applying a shooting technique using the Runge-Kutta Fehlberg method. The influences of the various involved parameters on velocity profiles, temperature profiles, concentration profiles as well as reduced skin friction coefficient, Nusselt number and Sherwood number are discussed through graphs and tables. These results show that the second-order slip flow model is necessary to predict the flow characteristics accurately in the presence of thermal radiation and melting effect.

Rheological behaviour of nanofluids: A review

Abstract: A colloidal mixture of nanometre-sized (<100 nm) metallic and non-metallic particles in conventional fluid is called nanofluid. Nanofluids are considered to be potential heat transfer fluids because of their superior thermal and tribological properties. In recent period, nanofluids have been the focus of attention of the researchers. This paper presents a summary of a number of important research works that have been published on rheological behaviour of nanofluids. This review article not only discusses the influence of particle shape and shear rate range on rheological behaviour of nanofluids but also studies other factors affecting the rheological behaviour. These other factors include nanoparticle type, volumetric concentration in different base fluids, addition of surfactant and externally applied magnetic field. From the literature review, it has been found that particle shape, its concentration, shear rate range, surfactant and magnetic field significantly affect the rheological behaviour of any nanofluid. It has been observed that nanofluids containing spherical nanoparticles are more likely to exhibit Newtonian behaviour and those containing nanotubes show non-Newtonian flow behaviour. Furthermore, nanofluids show Newtonian behaviour at low shear rate values while behave as non-Newtonian fluid at high shear rate values. Authors have also identified the inadequacies in the research works so far which require further investigations.

The Enhancement of Effective Thermal Conductivity and Effective Dynamic Viscosity of Nanofluids – A Review

Abstract: The determination of thermo-physical properties and especially thermal conductivity and viscosity were important for evaluating heat transfer coefficients either for single or two phase flow. The thermo-physical properties measurements and heat transfer observations were mostly obtained with nanoparticles above 10 nm. Various researchers measured and modelled for the determination of thermal conductivity and viscosity of nanofluids. Most of the investigators developed equations for the estimation of thermal conductivity and viscosity as a function of percentage volume concentration, temperature and sometimes with the consideration of particle size valid in their experimental range. Nanofluids are considered to have great potential for heat transfer enhancement and are applied in heat transfer processes. Many studies were carried out to investigate this phenomenon. The main aim of this study is to give a comprehensive review on the research progress on the enhancement of effective thermal conductivity and effective dynamic viscosity of nanofluids.

Flow and convective heat transfer of a ferro-nanofluid in a double-sided lid-driven cavity with a wavy wall in the presence of a variable magnetic field

Abstract: In this work, the effect of a variable spatial magnetic field on ferro-nanofluid flow and heat transfer in a double-sided lid-driven enclosure with a sinusoidal hot wall is investigated. The working fluid is a mixture of iron oxide (Fe3O4) nanoparticles and water and is referred to as a ferro-nanofluid. The control volume-based finite element method (CVFEM) is used to solve the governing equations in the stream function–vorticity formulation. In deriving the governing equations for this investigation, the effect of both ferro-hydrodynamics and magneto-hydrodynamics is taken into account. The numerical calculations are performed for different governing parameters namely; the Reynolds number, nanoparticle volume fraction, magnetic number (arising from Ferrohydrodynamics (FHD) consideration), and the Hartmann number (arising from Magnetohydrodynamics (MHD) consideration). The results show that an enhancement in heat transfer has a direct relationship with the Reynolds number and the Hartmann number, ...

Numerical study of convective heat transfer of nanofluids: A review

Abstract: The recent development of nanotechnology led to the concept of using suspended nanoparticles in heat transfer fluids to improve the heat transfer coefficient of the base fluids. Specifically, numerical studies are reviewed in this study to get a clear view and detailed summary of the influence of several parameters such as type of nanoparticle and host liquid, particle volume concentration, particle size, particle shape, Brownian diffusion and thermophoresis effect on hydrodynamic and thermal characteristics of convective heat transfer using nanofluids. In addition, the paper provides detailed information about the most of commonly-used correlations which are utilized to predict the effective thermophysical properties of nanofluids. Finally, the main aim upon which the present work is based is to give a comprehensive review on different CFD approaches employed in numerical simulation of nanofluid flow, address the pros and cons of each approach, and find the suitable technique which gives more credible results as compared to experimental results.