بررسي تجربي تاثير ميدان مغناطيسي ثابت و متناوب بر ويسكوزيته نانو سيال مغناطيسي اتيل گلايكول/ Fe3O4

چكيده انگليسي :

Experimental Investigation of the Effects of Magnetic Field on Viscosity of Magnetic Nanofluid of Fe3O4 EG Hamed Karimi Khuzani hamed karimi@ce iut ac ir March 12 2013 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Nasrin Etesami netesami@cc iut ac ir Abstract Viscosity of Fe3O4 Ethylene glycol magnetic nanofluid with coating of polyvinylpyrrolidone PVP as nanoparticles under DC and AC magnetic field was investigated Viscosity is an important property of fluid that has direct effect on pumping force Beside of that viscosity influences in Prandtl number so it can affect heat transfer of fluid The most of previous studies have considered the heat transfer properties of nanofluids and there are a few works about the rheological behavior of them In this project at the first rheological behavior of this nanofluid in different volume fractions of nanoparticles have been characterized by Brookfield rotational viscometer Results showed a Newtonian behavior for these nanofluids Therefore a capillary tube viscometer could be used confidently for measuring of viscosity of this nanofluid So a handmade capillary tube viscometer was used for measuring the viscosity since the magnetic field could be applied by using this viscometer In order to obtain the accuracy of capillary tube viscometer viscosity of base fluid was measured in different temperatures and compared with source data Fe3O4 nanopaticles were dispersed in Ethylene glycol and nanofluids prepared with volume fractions of 0 005 0 01 0 015 and 0 035 According to results obtained viscosity of nanofluid reduced with concentration of nanoparticles Every experiment has repeated for four times and standard deviations SD of each data were obtained The greatest reduction occurs for volume fraction of 0 035 which was 20 1 respect to base fluid It seems that this viscosity decrement is due to interactions between coatings of nanoparticles PVP with ethylene glycol Applying DC magnetic field on nanofluid in the parallel direction of fluid flow showed that the viscosity of magnetic nanofluid decreases with strength of magnetic field This reduction was maximum for nanofluid with volume fraction of 0 015 Magnetic force make magnetic particles to became dipole and by overcoming the displacement movement of particles make them to organize chains These chains influence the viscosity of magnetic nanofluid With increasing in time of applying magnetic field at first viscosity decreases and after that viscosity approaches to a constant amount due to reach to saturation magnetism status for magnetic nanoparticles The parallel magnetic field was applied by a solenoid Changing the direction of parallel magnetic field didn t have any effect on viscosity since the chains shape and the forces applied to particles are same in both directions Also influence of AC magnetic field on viscosity of nanofluid was investigated The results showed no change in viscosity even with increasing the time in exposure in highest volume fraction since changing poles frequently in alternating magnetic field doesn t let the particles to form chains Keywords magnetic nanofluid Fe3O4 Ethylene glycol nanofluid viscosity magnetic field capillary tube viscometer

كريمي خوزاني، حامد

بررسي تجربي تاثير ميدان مغناطيسي ثابت و متناوب بر ويسكوزيته نانو سيال مغناطيسي اتيل گلايكول/ Fe3O4

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