بررسي تجربي تاثير ميدان الكتريكي بر ضريب انتقال جرم فرآيند جذب گاز CO2 در نانو سيال آب/Fe3O4

چكيده انگليسي :

Experimental Investigation of the Effect of Electric Field on CO2 Absorption in Water Fe3O4 Nanofluid Nasim Hoseini n hoseini@ce iut ac ir Date of Submission 14 03 2012 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisors Mohsen Nasr Esfahany mnasr@cc iut ac ir Nasrin Etesami netesami@cc iut ac irAbstractIn this study a novel strategy for increasing and also controlling mass transfer rate in gas liquid system is reportedand used to the industrially important system of CO2 absorption The strategy makes use of Fe3O4 nanoparticles inthe liquid phase and also exerting external electric field To demonstrate this approach a unique experimental setup has been applied to form falling liquid film which is water to be in contact with gas phase which is purecarbon dioxide Experimental set up consisted of vertical capillary tubes in four different diameters of 6 8 10 14mm and two copper electrodes for exerting electric field Capillary tubes were placed between two electrodes andfilled by liquid while gas was injected in the liquid phase by means of a syringe After injection gas phase in theform of a bubble was rising up through the tube and liquid falling film created on the boundary of the gas bubbleand absorption process happened Length of bubble reduced due to the absorption process Length variation ofbubble was recorded by taking photos at the entrance and exit sections of the tube and mass transfer coefficientwas calculated Gas bubble was being exerted to the electric field by rising up and passing through the electrodes Nanofluid was purchased in stable concentrated suspension and diluted to the specific concentration by addition ofdistillated water The diluted suspension was stable and no sign of sedimentation was observed in stagnantnanofluid Nanofluids with concentrations of 0 001 0 005 0 01 0 025 by volume and field intensities of133 200 266 kV m were used in this study respectively Experimental results showed that external electric fieldis able to remarkably enhance gas absorption rate in the based liquid while deteriorates mass transfer innanofluids The maximum amount of enhancement in mass transfer coefficient was measured to be about 45 andthe maximum amount of reduction in mass transfer coefficient was about 63 5 in nanofluid with 0 005 concentration both at the highest field intensity used in this work 266kV m The ratio of mass transfercoefficient under electric field to that in the absence of field versus Reynolds number reached a peak at 1 45 inbase fluid whereas a minimum at 0 4 was observed in 0 001 concentration nanofluid The diffusion coefficientand viscosity of base fluid and nanofluid were also measured under electric field experimentally It was observedthat viscosity of nanofluid increased under electric field This effect is due to the chain formation of particles in thesuspension induced by their polarization Increasing viscosity leads to increasing resistance for transferringabsorbed component from interface to the bulk of liquid decreasing flow rate increasing falling film thicknessand then decreasing mass transfer coefficient Also it was observed that exerting electric field decreased diffusioncoefficient in nanofluid Decreasing diffusion coefficient leads to decreasing mass flux in the directionperpendicular to the falling liquid film Measured mass transfer and diffusion coefficients were compared withfilm and penetration theories Experimental data was in agreement with penetration theory Key Words mass transfer nanofluid electric field absorption

حسيني، نسيم

بررسي تجربي تاثير ميدان الكتريكي بر ضريب انتقال جرم فرآيند جذب گاز CO2 در نانو سيال آب/Fe3O4

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