6977

6519

كارشناسي ارشد

تبديل انرژي

اصفهان: دانشگاه صنعتي اصفهان، دانشكده مكانيك

1390

ده، 155ص.: مصور، جدول، نمودار

ص.ع. به فارسي وانگليسي

ابراهيم شيراني

محسن دوازده امامي

15/6/91

احمد صابونچي، علي اكبر عالم رجبي

1396/09/18

كتابنامه

مكانيك

مهندسي مكانيك

ID6519

به فارسي وانگليسي:قابل رويت در نسخه ديجيتالي

Numerical investigation of the effects of nanofluid variable properties on natural convection in enclosures Vahid Goodarzi v goodarzi@me iut ac ir Date of Submission Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Prof Ebrahim shirani eshirani@cc iut ac irAbstract A nanofluid is the suspension of nanoparticles in a base fluid Nanofluids are promising fluids for heattransfer enhancement due to their anomalously high thermal conductivity At present there is significantdiscrepancy in nanofluid thermal conductivity and viscosity data in the literature On the other hand thermal conductivity enhancement mechanisms of nanofluids have not been fully understood yet In thefirst part of this study a detailed literature review about thermo physical properties of nanofluids isperformed Experimental studies are discussed in terms of the effects of some parameters such as particlevolume fraction particle size and temperature on the thermal conductivity and viscosity of nanofluids inliteratures In the second part of the present study an empirical expression for the effective thermalconductivity of nanofluids based on interfacial shells and Brownian motion is derived Comparing withconventional models the expression is not only depended on the thermal conductivity of the solid andliquid and their volume fraction but also depended on the particle size temperature and interfacialproperties A new empirical correlations for predicting dynamic viscosity of nanofluids based on the effectsof temperature particle size and volume fraction are proposed too The results of current models on theeffective thermal conductivity and viscosity of CuO water Al2O3 water and TiO2 water nanofluids are ingood agreement with the experimental data Research about the natural convection of nanofluids isimportant for the practical application of nanofluids in heat transfer devices The objective of the presentstudy is to investigate numerically the effects of variable properties on natural convection heat transfer ofaqueous nanofluids On this regard thermophoresis of nanoparticles and the Dufour effects on naturalconvective heat transfer in nanofluids are investigated simultaneously By using double diffusiveformulation the combined effects of Brownian Motion thermophoresis and the Dufour on the variation ofheat transfer and Nusselt number of natural convection in rectangular enclosures under constant walltemperature is computed In order to numerically solve the governing equations a control volume approachis used Central differences are used to approximate the advection diffusion terms i e The sheme isImplicite and second order accurate in space and the SIMPLE algorithm is employed to solve the equations Numerical results are compared with experimental and numerical data in the literature and good agreementis observed especially with experimental data The agreement can be considered as an indication of thevalidity of the new double diffusive model for explaining nanofluid heat transfer Keywords Nanofluids natural convection Brownian motion thermophoresis Dufour effect

ابراهيم شيراني

محسن دوازده امامي

احمد صابونچي، علي اكبر عالم رجبي