Nanofluid properties for forced convection heat transfer :a review (original) (raw)
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International Journal of Mechanical and Materials Engineering, 2014
Nanofluids are suspension of nanoparticles (less than 100 nm) in the conventional base fluids. The dispersed solid metallic or non-metallic nanoparticles change the thermal properties like thermal conductivity, viscosity, specific heat, and density of the base fluid. Past studies focused on measuring the thermal properties of nanofluids. These suspended nanoparticles effectively improve the transport properties and heat transfer characteristics of the base fluids. Recently, heat transfer augmentation using suspensions of nanometre-sized solid particles in base liquids have been investigated by various research groups across the world. This paper reviews the state-of-the-art nanofluid studies in the area of forced convection heat transfer enhancement. The results for the heat transfer characteristics in internal flow with constant heat flux and constant wall temperature boundary conditions reported by various researchers have been compiled and reviewed. Further, in heat exchangers, the real boundary conditions are different from the constant heat flux and constant wall temperature boundary conditions. Over a span of 2 decades, the literature in this field is widespread; hence, this review would be useful for researchers to have a precise screening of a wide range of investigations in this area.
Comparison of Heat Transfer and Fluid Dynamic Performance of Nanofluids
TechConnect Briefs, 2007
Many recent studies have shown that nanofluids with metallic nanoparticles as suspension increase the thermal conductivity of base fluid by a substantial amount. First, we investigated the rheological properties of SiO 2 , Al 2 O 3 and CuO nanofluids at different volume percentages at varying temperatures. The fluids were tested over temperatures ranging from-35˚C to 50˚C. The viscosity trends showed the great influence of temperature on various nanofluids. Also, we investigated the particle diameter effect (20 nm, 50 nm, 100 nm) on nanofluid viscosity. Subsequent experiments were performed to investigate the convective heat transfer enhancement of nanofluids in a turbulent regime. During analysis of the convection coefficient, the measured viscosity values of the nanofluids were used as well as the thermal conductivity and specific heats were used from the available correlations in the current literature. Heat transfer coefficients of nanofluids increase with volume concentration, for example, a typical enhancement of a heat transfer coefficient of a 6% concentration of 45 nm CuO is about 54% at a Reynolds number of 8,000. Similar results were investigated for aluminum and silicon oxide nanofluids in ethylene glycol/water base fluid. Pressure loss was observed to increase with nanoparticle volume concentration and also with increasing particle diameter. It was observed that an increase in particle diameter increased the heat transfer coefficient. Applications of nanofluids will be in heating building and in automobiles in northern climates.
Heat transfer enhancement by using nanofluids in forced convection flows
International Journal of Heat and Fluid Flow, 2005
In the present paper, the problem of laminar forced convection flow of nanofluids has been thoroughly investigated for two particular geometrical configurations, namely a uniformly heated tube and a system of parallel, coaxial and heated disks. Numerical results, as obtained for water-cAl 2 O 3 and Ethylene Glycol-cAl 2 O 3 mixtures, have clearly shown that the inclusion of nanoparticles into the base fluids has produced a considerable augmentation of the heat transfer coefficient that clearly increases with an increase of the particle concentration. However, the presence of such particles has also induced drastic effects on the wall shear stress that increases appreciably with the particle loading. Among the mixtures studied, the Ethylene Glycol-cAl 2 O 3 nanofluid appears to offer a better heat transfer enhancement than water-cAl 2 O 3 ; it is also the one that has induced more pronounced adverse effects on the wall shear stress. For the case of tube flow, results have also shown that, in general, the heat transfer enhancement also increases considerably with an augmentation of the flow Reynolds number. Correlations have been provided for computing the Nusselt number for the nanofluids considered in terms of the Reynolds and the Prandtl numbers and this for both the thermal boundary conditions considered. For the case of radial flow, results have also shown that both the Reynolds number and the distance separating the disks do not seem to considerably affect in one way or another the heat transfer enhancement of the nanofluids (i.e. when compared to the base fluid at the same Reynolds number and distance).
Review on Nanofluids as Potential Heat Transfer Fluid
An automotive engine cooling system takes out of excess heat produced during engine operation. A vehicle cooling system regulates engine surface temperature for engine most optimal efficiency. Recent advancements and improvements in an engine for power forced engine cooling machine to develop new techniques to improve its overall performance efficiency and also to reduce fuel consumption. Nanofluid is a suspension of nanoparticles that is a promising heat transfer fluid inside the heat transfer enhancement having an excess of applications because of its advanced thermal conductivity and rheological properties. This paper points out the previous studies and recent progress in the field of improvement in heat transfer with the usage of nanofluid. The latest progress on preparation and enhancement of stability had been reviewed. Thermophysical properties, heat transfer characteristics of nanofluid, and various factors together with particle size, form, surfactant, temperature, and many others on thermal conductivity were presented. The present study discloses potential applications by nanofluid which include heat exchanger, transportation cooling, refrigeration, electronic system cooling, transformer oil, commercial cooling, nuclear device, machining operation, solar electricity and desalination, defense, and many others. Few barriers and challenges had been also addressed. The comprehensive review also covers the most recent investigations on the application of nanofluids in heat transfer enhancement of automotive radiators.
Review: Enhancement of heat transfer by using Nano fluids
This paper gives a detailed literature study and scrutiny into the results of the research and development, applications of nanofluids in heat transfer. Nanofluid is a comparatively new technology, the studies on nanofluid are not longer. Experimental data were reviewed in this study related to the enhancement of the thermal conductivity and convective heat transfer of nanofluids relative to conventional heat transfer fluids, and assessments were made as parameters of volume concentration, material, particle size, , base fluid material, temperature, particle shape, additive, and pH were taken into account, experimental results from so many researcher were used together when assessing data. The current state of knowledge is presented as well as areas where the data are presently inconclusive or conflicting. Heat transfer enhancement can be achieved using nanofluids is to be in the 15–40% range, with a few situations resulting in orders of magnitude enhancement
A NUMERICAL FORCED CONVECTION HEAT TRANSFER ANALYSIS OF NANOFLUIDS CONSIDERING PERFORMANCE CRITERIA
A nanofluid is a new heat transfer fluid produced by mixing a base fluid and solid nano sized particles. This fluid has great potential in heat transfer applications, because of its increased thermal conductivity and even increased Nusselt number due to higher thermal conductivity, Brownian motion of nanoparticles, and other various effects on heat transfer phenomenon. In this work, the first aim is to predict convective heat transfer of nanofluids. A numerical code is created and run to obtain results in a pipe with two different boundary conditions, constant wall temperature and constant wall heat flux. The v results for laminar flow for thermally developing region in a pipe are obtained for Al2O3/water nanofluid with different volumetric fraction and particle sizes with local temperature dependent conductivity approach. Various effects that influence nanofluid heat transfer enhancement are investigated. As a result, a better heat transfer performance is obtained for all cases, compared to pure water. The important parameters that have impact on nanofluid heat transfer are particle diameter of the nanoparticles, nanoparticle volumetric fraction, Peclet number, and viscous dissipation. Next, a heat transfer performance evaluation methodology is proposed considering increased pumping power of nanofluids. Two different criteria are selected for two boundary conditions at constant pumping power. These are heat transfer rate ratio of the nanofluid and the base fluid for constant wall temperature boundary condition and difference between wall temperature of the pipe at the exit and inlet mean temperature of the fluid ratio for constant wall heat flux case. Three important parameters that influence the heat transfer performance of nanofluids are extracted from a parametric study. Lastly, optimum particle size and volumetric fraction values are obtained depending on Graetz number, Nusselt number, heat transfer fluid temperature, and nanofluid type.
Nanofluids for Heat Transfer : An Analysis of Thermophysical Properties
2015
Nanofluids have emerged as a new class of fluids with special characteristics of enhanced heat transfer characteristics. It is designed by suspending nanoparticles of dimension ranging from 1nm-100nm into a base fluid like water ,ethylene glycol or oil. The volume fraction of particles under study ranges from 2% to 8%. A higher volume fraction results in the particles agglomerating as well as causing abrations in the walls through which it flows. Nanofluids for heat transfer has managed to overcome both these problems. The suspensions are more stable and cause lesser damage to the walls along with better heat transfer characteristics than the base fluids. It is therefore possible to design lighter and more compact heat exchangers as the quantity of the fluid required is much smaller than the base fluid. The suspension of metal and metal oxides in base fluids which are the conventional heat removing fluids, are the nanofluids under study in this paper. Investigating the thermophysica...
Advanced Heat Transfer Enhancement by using Nanofluids: A Review
The purpose of this review article is to summarize the important published articles on the enhancement of the convection heat transfer with Nanofluids. Over the last 2-3 decades, there has been intensive research into the behavior of substances that contain extremely small particles. Nanotechnology is the science and engineering of working at the Nano-scale, where the individual particles are 1-100 nanometers in size. It's hard to imagine the size of nanoparticles, but there are about 2, 54, 00,000 nanometers in an inch. Nanofluids which are less than even a micron (nearly 10-9 times smaller) in diameter, highly reactive and efficient material which can be used to increase factor like rate of heat transfer, thermal conductivity of any metal or material, they are that much reactive and strong. The thermal conductivity increases with decreasing the grain size of the material. As the thermal conductivity increases the heat transfer rate increases.
TO STUDY THE BEHAVIOR OF NANOFLUIDS IN HEAT TRANSFER APPLICATIONS: A REVIEW
Using nanofluids as an innovative kind of liquid blend including trivial volume fraction (in percent) of millimeter or nanometer size powdered particles with base fluids is fairly a novel arena or idea. The objective of this presented review paper is to inspect the performance of the nanofluid-based solar collector (NBSC). In past few years for a number of experimental and industrial thermal engineering systems solar energy has proven to be the best input energy source. Nanofluids are the fluid that has shown various developments in the thermal properties over the past decade. In the field of nanotechnology, nano fluids have a great potential to enhance the rheological properties like thermal conductivity of base fluid like water, ethanol etc. Nanofluids are the suspension of mainly the base fluid like water in nanoparticles such as alumina (Al 2 O 3) of size micro or milimetre and shows distinctive features than that of conservative fluids used. Because of better rheological properties nanofluids are utilized to build up the performance of conventional solar thermal engineering systems. The presented literature review presents a detailed discussion about the solar collectors, applications of nanofluids in solar collector and their augmentation in thermo physical properties.