بررسي ويسكوزيته نانو سيالات و عوامل موثر بر آن

چكيده انگليسي :

Viscosity of Nanofluids Yalda Shoja Email yalda shoja1981@yahoo com 29 2 2009 Department of Chemistry Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiE Keshavarzi E mail keshavrz@cc iut ac ir Y Ghayeb E mail ghayeb@cc iut ac ir AbstractThise work focuses on the viscosity of nanofluids related to the nanocluster size of dispersed nanoparticles particles concentration temprature and shear rate Nanofluidsarediluteliquid suspensions of nanoparticleswith at least one of their critical dimensions smaller than about 100 nm Much attention has been paid inthe past decade to this new type of heat transfer materials because of their enhanced properties andbehaviour associated with heat transfer mass transfer wetting and spreading and antibacterial activity These enhanced properties and behaviour imply an enormous potential of nanofluids in deviceminiaturization and process intensification which could have an impact on many industrial sectorsincluding chemical and process transportation electronics medical and energy and environment Mostpublished studies on nanofluids deal with the heat transfer behaviour including thermal conduction phasechange boiling heat transfer and convective heat transfer which have been reviewed recently Very fewstudies however have been reported on the rheological behaviour of nanofluids Key requirements fornanofluids include low solids loading but with high thermal properties favourable rheologocial propertiesand flow behaviour and great stability over a wide range of temperature to meet the industrial needs Clearly there is a gap in the current rheological literature for this type of fluids This forms the primarymotivation of this work Recent work has shown evidence of a relationship between the thermal andrheological behaviour of nanofluids Given the recent surge in nanofluids research there is an urgent needto answer these questions This forms the second motivation of carrying out this work This work aims atunderstanding the rheological behaviour of nanofluids through both experimental work and theoreticalanalyses The focus will be on nanofluids containing spherical particles The experimental work uses titania TiO2 based the propylene glycol PG nanofluids whereas the theoretical analyses is based on our currentunderstanding of the rheology of colloid suspensions The reasons for the use of PG based TiO2 nanofluidsare i TiO2 is generally regarded as a safe material for humans and animals although it is recognized thatthis may change in the future with more fundamental research on nano toxicology ii TiO2 nanoparticlesare produced on large industrial scales so are easy to obtain iii metal oxides such TiO2 nanoparticles arechemically more stable than their metallic counterparts although it is recognized that the photocatalyticeffect of TiO2 may impose restrictions in selecting the base liquid iv PG known also by the systematicname propane 1 2 diol is an organic compound usually sweet odorless and colorless clear viscous liquidthat is hydroscopic and miscible with water acetone and chloroform and it can be used over a fairly widerange of temperature PG does not cause sensitization and it shows no evidence of being a carcinogen or ofbeing genotoxic experiments analyses are carried out with the experimental work on propylene glycol PG based nanofluids containing 0 5 5 Vol spherical TiO2 nanoparticles at 25 55 C The experimentalresults show that the PG based nanofluids are Newtonian under the conditions of this work with the shearviscosity as a strong function of temperature and particle concentration The relative viscosity of thenanofluids is however independent of temperature Having established confidence with the base liquid therheological behaviour of the formulated nanofluids were measured over a temperature range of 25 55 C 293 15 328 15 K with an interval of 5 K The relative viscosity depends on particle concentration in anonlinear manner but is independent of temperature K

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بررسي ويسكوزيته نانو سيالات و عوامل موثر بر آن

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