Ann modeling of the viscosity and effective thermal. Stability and thermal conductivity enhancement of carbon. A considerable number of studies can be found on the thermal conductivity of nanofluids in which al 2 o 3 nanoparticles are used as additives. The current cuo nanofluid has a higher thermal conductivity than those prepared by the dispersing method. Experimental and theoretical studies of nanofluid thermal conductivity enhancement.
They found out that the effective thermal conductivity and stability of their nanofluid were significantly dependent on the sdbs concentration and ph value of the fluid, where the effective thermal conductivity was increased by 10. The theoretical results on the effective thermal conductivity of nanotubeoil nanofluid and al2o3water nanofluid are in good agreement with the experimental data. The increase in the effective thermal conductivity of nanofluid 0with temperature is clearly seen. Heat sourcesink and thermal conductivity effects on. A nanofluid is a kind of colloidal dispersion achieved by dispersing nanoparticles in a base fluid 4.
The result shows that the nanofluid concentration in the range of 0. This article describes the effect of thermal radiation on the thin film nanofluid flow of a williamson fluid over an unsteady stretching surface with variable fluid properties. Therefore, enhancing nanofluids stability and understanding nanofluid behaviour. Article views are the countercompliant sum of full text article downloads since november 2008 both pdf and html across all institutions and individuals. Nanofluids thermal conductivity enhancement consists of four major mechanisms. They showed that the ph value of the nanofluid strongly affected the thermal performance of the fluid. Accurate measurement of nanofluid thermal conductivity by use of a polysaccharide stabilising agent. Effects of variable viscosity and thermal conductivity on. Nanofluid thermal conductivity a thermomechanical, chemical structure and computational approach by. Since diffusion, directly and indirectly, is considered to be a key mechanism for the nanofluid thermal conductivity in several new theories. A nanofluid is a dilute suspension of nanometersize particles and fibers dispersed in a liquid. Experimental and theoretical studies of nanofluid thermal.
The concentration of particles and added surfactant are responsible for stable fluid, thermal conductivity enhancement, and viscosity of nanofluid with respect to temperature. Thermal conductivity and specific heat capacity of. Aug 16, 2011 experimental and theoretical studies of nanofluid thermal conductivity enhancement. This makes them very attractive as heat transfer fluids in many applications. The effect of thermal conductivity enhancement for brownian. Viscosity and thermal conductivity of copper oxide nanofluid. A comparison of nanofluid thermal conductivity measurements by flash and hot disk techniques to cite this article. Jan 10, 2007 the thermal conductivity of cuo nanofluid was investigated. The effect of thermal conductivity enhancement for.
In the nanofluid model, a gradient of nanoparticles concentration because of brownian motion and thermophoresis forces is taken into account. The user has requested enhancement of the downloaded file. There are a number of advantages of using nanofluid over the conventional fluids, such as long suspension stability, no clogging in systems, and little pressure drop. Covalent nd surface modification gives 2fold greater thermal conductivity enhancement than nd surface modification via hydrogenbonding interactions at similar concentrations. Optimization of thermal conductivity of al o nanofluid 2 3 by.
Nanofluids mit massachusetts institute of technology. Although literature data could be correlated well using the model, the effect of the size of the particles on the effective thermal conductivity of the nanofluid. Pdf thermal conductivity of nanofluids experimental. Numerical modeling of nanofluid thermal conductivity. The resulting nanofluids enhanced thermal conductivity of the base fluids. The success of developing nanofluids of superior conductivity depends thus very much on our understanding and manipulation of the morphology and the coupled transport. In this result particle size is an important parameter on thermal conductivity because the opposite temperature trend was reported by. In this work aims at improving thermal conductivity of the waterbased drilling fluid by using the cuo nanofluid additive. Viscosity and thermal conductivity of copper oxide nanofluid dispersed in ethylene glycol koreaaustralia rheology journal june 2005 vol. Thin film williamson nanofluid flow with varying viscosity and thermal conductivity on a timedependent stretching sheet article pdf available in applied sciences 66. Finally cuo nanofluid was added to the water based drilling fluid and thermal conductivity propertied was mesured. Angelos yiannou university of pretoria february 2015 nanofluid thermal conductivity a thermomechanical, chemical structure and computational approach.
Oct 10, 2005 in this letter, we report an experimental correlation eqs. The brownian dynamics simulations of the nanofluid system during which the. Thermal conductivity and electrical properties of hybrid sio2. Pdf thin film williamson nanofluid flow with varying. In the present study, the aim is to measure the thermal conductivity of very narrow al 2 o 3 nanoparticles with the size of 5 nm suspended in water. The thermal conductivity of cuo nanofluid was investigated. Thermal conductivity and electrical properties of hybrid. Pdf thermal conductivity and viscosity of deionised. The classical nature of thermal conduction in nanofluids. Thermal conductivity of hybrid nanofluid was much greater than base fluid because of copper nanoparticles which had high thermal conductivity. The increasing need in many applications for fluids with more efficient heat transfer has.
Choi argonne national laboratory, argonne, illinois 60439 effective thermal conductivity of mixtures of uids and nanometersize particles is measured by a steadystate parallelplate method. Of all the physical properties of nanofluids, the thermal conductivity k nf is the most complex and for many applications the most. Mar 16, 2011 a nanofluid is a dilute suspension of nanometersize particles and fibers dispersed in a liquid. Effect of variable viscosity and thermal conductivity on. Improvement of thermal conductivity properties of drilling. Experimental investigation of thermal conductivity through nanofluids muhammad abid submitted to the institute of graduate studies and research in partial fulfillment of the requirements for the degree of master of science in mechanical engineering eastern mediterranean university january 2012 gazimagusa, north cyprus. Observed thermal conductivity enhancements outperform enhancement effects calculated using maxwells effective medium approximation by 2 to 4fold. Pdf nanofluid thermal conductivity and effective parameters. Uit2014 a comparison of nanofluid thermal conductivity. Of all the physical properties of nanofluids, the thermal conductivity knf is the most complex and for many applications the most important one. Determining the thermal conductivity of nanofluids using. As a result, when compared to the base fluid, changes in physical properties of such mixtures occur, e. Phasetransfer method is also a facile way to obtain monodisperse noble metal colloids.
Thermal conductivity of cnt nanofluids is measured using kd2 prothermal conductivity meter from 25 to 60 c. Effect of particle size on the thermal conductivity of. The effect of nanofluid concentration was investigated on the improvement of thermal conductivity properties of water. The model accounts for the enhancement in effective thermal conductivity of a nanofluid with respect to the suspended nanoparticles size, volume fraction, temperature and thermal conductivities of the nanoparticle and. They have excellent thermosphysical properties, such as thermal conductivity, specific heat capacity, thermal diffusivity, viscosity, and c onvective heat transfer coefficients 5. The effects of variable viscosity and thermal conductivity on the natural convection heat transfer over a vertical plate embedded in a porous medium saturated by a nanofluid are investigated.
In this result particle size is an important parameter on thermal conductivity because the opposite temperature trend was reported by masuda et al. Novel synthesis and thermal conductivity of cuo nanofluid. Experimental studies of nanofluid thermal conductivity enhancement and. Abstract nanofluid is an innovative class of nanotechnologybased thermal fluids and has been proven to improve the energy conversion process efficiency significantly. The basic governing equations of continuity, momentum, energy, and. A nanofluid is composed of a base fluid water, oil, glycol etc. The possible mechanisms are presented for the high thermal conductivity of nanofluids. The impact of nanoparticles on the enhanced thermal conductivity of nanofluids is clearly shown through plotting the thermal conductivities of. This study investigates the synergistic effect of combining multiwalled carbon nanotubes mwnts and fe2o3 nanoparticles on thermal conductivity of nanofluid. Heat sourcesink and thermal conductivity effects on micropolar nanofluid flow over a mhd radiative stretching surface srinivas maripala1 and kishan naikoti2 1department of mathematics, sreenidhi institute of science and technology, ghatkesar, hyd501.
The results demonstrated a strong dependence of nanofluid thermal conductivity on the nanocluster density, where a looser nanonetwork can yield a significantly higher level of thermal conductivity enhancement under the same particle size and concentration conditions. Figures 5 and 6 show the effect of sonication time on stability of cnt nanofluid for cnt concentration of 0. In order to evaluate this enhancement, nanofluid thermal conductivity is required to be. Meanwhile, in viscosity test, the highest temperature of 40 c exhibited lowest viscosity. Thermal property measurement of nanofluid droplets with. Pdf experimental studies of nanofluid thermal conductivity.
Nanodiamond nanofluids for enhanced thermal conductivity. While an intrinsic thermal conductivity exists for the nanofluids, the measured thermal conductivity can include effects of diffusion, chemical reactions and other external fields. Pdf thermal conductivity and viscosity of deionised water. The concentration of particles and added surfactant are responsible for stable fluid, thermal conductivity enhancement, and viscosity of. Thermal conductivity of the nanofluids, the fundamental thermophysical property determining their performance, is a subject of extensive controversies over the years and thereby. The thermal conductivity of nanofluids with concentrations up to 5 % is measured in a. The beauty of nanofluid is that it can improve or enhance thermophysical properties such as thermal conductivity, thermal diffusivity, viscosity and convective heat transfer. Thermal conductivity of nanofluids semantic scholar.
The measurement of thermal diffusivity and thermal conductivity is based on the energy equation for conduction. Model for effective thermal conductivity of nanofluids digital library. Temperaturedependent thermal conductivity and viscosity. Related content preparation, thermophysical properties and heat transfer enhancement of nanofluids. Review on thermal conductivity of nanofluids sciencedirect. Optimization of thermal conductivity of al o nanofluid 2 3. The results revealed that thermal conductivity was enhanced by about 8. In a recent decade, application of nanofluid as a candidate for heat transfer medium has gaining an increasing attention due to its unique advantages. The assessment of proposed origins for thermal conductivity enhancement in nanofluids signifies the importance of particle morphology and coupled transport in determining nanofluid heat conduction and thermal conductivity. In the light of its unique advantages, it has been utilized in different industries such as oil and gas industries. Experimental investigation of thermal conductivity through.
The model takes into account the decrease in thermal conductivity of metal nanoparticles with decreasing size. Oct 03, 2016 the results revealed that thermal conductivity was enhanced by about 8. The effect of thermal conductivity enhancement for brownian motion of nanofluids. Thermal conductivity of al2o3water nanofluids springerlink. The thermal conductivity of nanofluid has been measured using the transient hotwire method where the temperature increase of the platinum wire referred as hotwire is related to the thermal conductivity k eff of the fluid29, widely employed to measure thermal conductivity of nanofluids 3031. The further the ph value diverged from the isoelectric point of the particles, the more stable the nanoparticles in the suspension and greater the change in the thermal conductivity. Determining the thermal conductivity of nanofluids using the hot disk tps nanofluids are an exciting field of scientific discovery and research. A oneparameter model is presented for the thermal conductivity of nanofluids containing dispersed metallic nanoparticles. The effect of the concentration of the base fluid, nanofluid concentration, temperature, diameter of nanoparticles, and nature thermal conductivity of the material of nanopowder on effective thermal conductivity were investigated.
All intext references underlined in blue are added to the original document and are linked to publications on researchgate, letting you access and read them immediately. Effective thermal conductivity of carbon nanotubebased cryogenic nanofluids. The study of existing literature on nanofluids discloses that the viscosity as well as thermal conductivity of the nanofluid is considered variable properties and are strongly varies with volume fraction of. Oct 24, 2017 thermal conductivity and viscosity are measured for 0.
A nanofluid is generally understood to mean a suspension of nanosized particles having diameter of about 1 nm to 100 nm in a conventional base fluid 24. Of all the physical properties of nanofluids, the thermal conductivity k nf is the most complex and for many applications the most important one. Pdf empirical correlation finding the role of temperature. Thermal conductivity of nanoparticlefluid mixture xinweiwangand xianfan xu purdue university, west lafayette, indiana 47907 and stephen u. Pdf thin filmwilliamson nanofluid flow with varying. The advantage that the thermal conductivity of a magnetic nanofluid can be tuned with the application of an external magnetic field make them suitable for applications in heat transfer 6 78. Determining the thermal conductivity of nanofluids using the. Over the past decade, nanofluids, which are liquids containing suspensions of nanoparticles fig. Enhanced thermal conductivity of nanofluid by synergistic. Feb 28, 2011 an overview of systematic studies that address the complexity of nanofluid systems and advance the understanding of nanoscale contributions to viscosity, thermal conductivity, and cooling efficiency of nanofluids is presented.
The early studies indicating anomalous increases in nanofluid thermal properties over those of the base fluid, particularly the heat transfer coefficient, have been largely discredited. The hotwire apparatus is used to measure the thermal conductivity of nanofluids with suspended copper nanophase powders. Thermal conductivity of nanoparticle fluid mixture. Among the thermo physical properties of the nano fluids thermal conductivity is the key property which depends on the pertinent parameters of nanoparticles. The theoretical study of the thermal conductivity of nanofluids is introduced. The results show that welldispersed cuo nanofluid with high volume fractions can be synthesized using the current method. Results show that low percentage hybrid fillers loading improve thermal conductivity of water based nanofluid, due to the good dispersion and interfacial adhesion, which is confirmed by scanning electron microscope. The thermal conductivity of nanofluid has been measured using the transient hotwire method where the temperature increase of the platinum wire referred as hotwire is related to the thermal conductivity k eff of the fluid29, widely. The ammonium citrate prevents the growth and aggregation of nanoparticles, resulting in a stable cuo aqueous nanofluid with higher thermal conductivity than those prepared by other dispersing methods.
However, it is not very practical when efficiencies of two fluids are compared in the same system geometry i. Nanofluids consist of nanometersized particles or fibers in colloidal suspension within a host fluid. Temperaturedependent thermal conductivity and viscosity of. Nanofluid, which is a suspension of nanoparticles in a fluid, has been found to have better thermal conductivity than the respective base fluid. Toward nanofluids of ultrahigh thermal conductivity. Pdf thermal conductivity of nanofluids experimental and. Viscosity and thermal conductivity of copper oxide. Effect of variable viscosity and thermal conductivity on heat. Mwcnts in the ethylene glycol was calculated to be. Feed forward ann has been used to predict the apparent viscosity and effective thermal conductivity of nanofluid. Thermal conductivity and viscosity are measured for 0.
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