اندازه گيري خواص حرارتي سوسپانسيون هاي نانوذرات اكسيد آلومينيوم و اكسيد مس درروغن موتور﴿نانوسيال﴾

چكيده انگليسي :

Abstract Nanofluid or suspension of nanoparticles in a base fluid is name of a new kind of engineeringmaterial that is believed to have higher thermal conductivity comparing to that of the base fluid Base fluids such as water ethylene glycol or anti freezant and different types of oils have lowthermal conductivity These fluids can be found in industrial applications as heat conveyers Wide range of nanoparticles such as metallic oxide metallic and nonmetallic like carbon nanotubes CNT have been used to prepare nanofluids and their thermal conductivity have beenreported to be higher than the base fluid but the reported numbers are different In the present investigation thermal conductivity and heat capacity of suspensions of aluminaand copper oxide nanoparticles in engine oil were measured for different temperatures rangingfrom to degrees centigrade and for different nanoparticle concentration up to volumepercent The effects of temperature and concentration of nanoparticles on thermal conductivityand heat capacity have been investigated Comparing to other attempts this project have two new aspects first the engine oil that hasbeen used as base fluid and second measuring heat capacity of prepared nanofluids There aresome reports about measuring thermal conductivity of engine oil based carbon nanotubesuspensions but there is no report about using metallic oxide nanoparticles Heat capacity isalso another important thermal property that has not been under consideration of researchers Thermal conductivity was measured by hot wire transient method The basis of this method ison the radial distribution of heat in an infinite media Thus thermal conductivity is determinedby measuring temperature in the center of wire in various time intervals during an unsteadyprocess Name of the used device was KD a product of Decagon Device Inc By adding volume percent alumina nanoparticles thermal conductivity of engine oil increased about percent Adding copper oxide nanoparticles to engine oil by volume percent it s thermalconductivity enhanced about percent A linear relationship was seen between thermalconductivity enhancement of nanofluids and the volume percent of used nanoparticles Thermalconductivity of nanofluids decreased with increasing temperature and the behavior was like thatoccurred for pure engine oil Also enhancement of thermal conductivity was lower in uppertemperatures Uncertainty of measurements was lower than percent and was measured bydifferent approaches and reported Measuring heat capacity of prepared nanofluids was done using an adiabatic calorimeter Thecalorimeter was designed and constructed according to the required uncertainty Transferring ofheat to sample and measuring corresponding temperature gradient in an adiabatic environmeatis the base of measurement with this method Adding volume percent alumina nanoparticlesand volume percent copper oxide nanoparticles to engine oil caused its heat capacity toreduce about and percent respectively Heat capacity of prepared nanofluids increasedwith temperature which is similar to the trend occurs for pure engine oil Important point whichwas seen in these measurements is the sharp rate of reduction of heat capacity in lowconcentration of nanoparticles but with increasing concentration this rate gets linear it sinterpretation may be lied in the fact of clustering nanoparticles in high nanoparticleconcentration and thus reduction of their molecular effects Uncertainty of measurements wasless than percent and measured and reported with different approaches

خان محمدي، سهراب

اندازه گيري خواص حرارتي سوسپانسيون هاي نانوذرات اكسيد آلومينيوم و اكسيد مس درروغن موتور﴿نانوسيال﴾

فناور نانو , هدايت حرارتي , محيط ايزوتروپيك , DSC