بررسي تجربي تاثير ميدان هاي خارجي ﴿الكتريكي و مغناطيسي﴾ بر ويسكوزيته نانو سيال مغناطيسي Fe3o4/EG

چكيده انگليسي :

Experimental Investigation of the Effects of External Fields on Viscosity of Fe3O4 EG Nanofluid Elaheh Monajjemi Rarani e monajjemirarani@ce iut ac ir February 29 2012 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc language FarsiAssist Prof Nasrin Etesami netesami@cc iut ac irAssoc Prof Mohsen Nasr Esfahany mnasr@cc iut ac irAbstract There are few previous researches on the effect of external field on thermal and rheological characteristics ofnanofluids and nanomagnetic fluids Increase in nanofluid viscosity compared to base fluid has negative effectson heat transfer and transport properties of nanofluids and therefore trying to improve these properties bymaking excess motions in nanofluid would be of desire Applying external field magnetic or electric on specially magnetic nanofluid would enhance these properties In this study viscosity changes of magneticnanofluid Fe3O4 Ethylene glycol in the presence of external field electric and magnetic field wereinvestigated experimentally The effects of volume fraction of the suspended nanoparticles the external electricand magnetic field intensity the type of electric field AC or DC and temperature on the viscosity of thenanofluids were analyzed The capillary tube viscometer was used for measuring the viscosity and Brookfieldrotational viscometer was used characterizing the rheological behavior of base fluid and nanofluid Fe3O4nanoparticles were dispersed in pure Ethylene glycol as base fluid in 0 01 0 015 0 02 0 035 and 0 05 volumefraction concentrations The viscosity of the magnetic nanofluids was measured in either the absence or thepresence of the external fields The accuracy of capillary viscometer was examined by comparing ofexperimental data in different temperature to reference data The obtained results from rotational viscometerindicated that the base fluid and nanofluid have Newtonian behavior in the experimental conditions Addition ofnanoparticles in to the base fluid decreases its viscosity The viscosity reduces from 6 3 to 10 1 withincreasing nanoparticle concentration from 0 01 to 0 05Vol Changes of base fluid viscosity and nanofluidsviscosity were investigated under different intensities of DC and AC electric fields Results showed that theviscosity decreases with application of DC and AC electric fields The effect of DC electric field on decreasingthe viscosity of the magnetic nanofluids is greater than AC electric field but about the base fluid the effect ofAC electric field is greater Also the effect of magnetic field perpendicular to the direction of flow on theviscosity of magnetic nanofluids was investigated The magnetic field was applied by two strong magnets onboth sides of the capillary tube and magnetic field intensity was controlled by changing in the distance ofmagnet segments Increase in the magnetic field intensity cause viscosity reduction Also the viscositydecreases with exposure time increase of nanofluids in the magnetic field No effect was observed on viscosityof base fluid under magnetic field Increase in concentration of nanoparticles leads to increase in the effect ofelectric and magnetic fields Key words Viscosity nanofluid ethylene glycol Fe3O4 nanoparticles capillary tube viscometer electricfield magnetic field

منجمي راراني، الهه

بررسي تجربي تاثير ميدان هاي خارجي ﴿الكتريكي و مغناطيسي﴾ بر ويسكوزيته نانو سيال مغناطيسي Fe3o4/EG

اتيلن گليكول , ويسكومتر لوله موئين , ميدان الكتريكي