بررسي عددي انتقال حرارت و افت فشار در جريان آرام نانو سيال آب- اكسيد آلومينيوم در ميكرو كانال

چكيده انگليسي :

Numerical Investigation of AL2O3 Water Nano Fluid Heat Transfer Pressure Drop in Microchannel s Laminar Flow Mohammad Sadegh Salehi MS salehi@me iut ac ir parsa 3h@gmail com Date of Submission 2012 03 05 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Ahmad Sedaghat Sedaghat@cc iut ac irAbstract Nano fluids are a new division for heat transfer enhancement But Nano fluid Flows and heat transferanalyses are more complicated than their base fluids Nonlinear variation of thermo physical properties ofNano fluids with variation of temperature and volume fraction of nanoparticle the shape and size effects onproperties and effective mechanism in thermal properties of Nano fluids must be concern in analyses TheReynolds number in Nano fluid studies depends on the inlet and the kinematic viscosity of Nano fluid TheNano fluid kinematic viscosity increases with an increasing in nanoparticles volume fraction while the inletvelocity should be increased to keep the Reynolds number constant Therefore it is not clear that eitherincreasing the nanoparticles volume fraction or increasing the inlet velocity has major role on heat transferenhancement in Nano fluids flow studies which are done at constant Reynolds numbers In this study forcedconvection AL2O3 Water Nano fluid laminar flows in two dimensional rectangular micro channels havebeen investigated to study thermal efficiency and heat transfer enhancement due to addition of thenanoparticles to the base fluid and analyses the effects and sensitivity of variational proprieties of Nano fluidwith temperature especially in micro channels at low Reynolds number Two different cases are examined toevaluate proportion impact of increasing nanoparticles volume fraction and the inlet velocity on theheat transfer enhancement and in third case the slip velocity and temperature jump with constant temperaturecondition at the wall for a Nano channel have been investigated Two dimensional Navier stokes and energyequations accompany with the slip velocity and the jump temperature boundary conditions expression havebeen discretized using the central finite difference method The constant and variational properties of Nanofluid have been considered to determine the thermal conductivity and kinematic viscosity of Nano fluids Thecalculated results show good agreement with the previous numerical and analytical data It is found that at agiven Reynolds number the major enhancement in thermal efficiency is not due to increasing the Nanoparticle concentrations but it is due to the increasing the inlet velocity to reach a constant Reynolds number Constant Reynolds number studies of Nano fluids are not sufficient approach to evaluate the heat transfer andthe skin friction factor due to nanoparticle usage The Nuselt number in thermal studies depends on the heattransfer conductivity coefficient and the heat transfer convective coefficient Hence the heat transferconvective coefficient is depends on the fluid and flows properties The result shows heat transferenhancement hence the Nuselt number is decrease in variational properties Nano fluid analyses and it isbecause of the velocity profile change in Nano fluid analyses with variational properties So Nuselt numberstudies of Nano fluids with variational properties are not sufficient approach to evaluate the heat transfer andthe skin friction factor due to nanoparticle usage Result shows good enhancement in nano fluids heat transferefficiency in front of their base fluid with using little volume fraction of nanoparticle but this ThermalEfficiency decrease with increasing volume fraction of nanoparticle Keywords Nano fluid Micro channel Thermal Efficiency Vibrational Properties

صالحي، محمدصادق

بررسي عددي انتقال حرارت و افت فشار در جريان آرام نانو سيال آب- اكسيد آلومينيوم در ميكرو كانال

راندمان حرارتي , خواص متغير , كسر حجمي