Amirkabir University of Technology Amirkabir Journal of Mechanical Engineering 2008-6032 50 6 2019 02 20 Natural Convection of Turbulent Al2O3-Water Nanofluid with Variable Properties in a Cavity with a Heat Source and Heat Sink on Vertical Walls Natural Convection of Turbulent Al2O3-Water Nanofluid with Variable Properties in a Cavity with a Heat Source and Heat Sink on Vertical Walls 1237 1250 1086 10.22060/mej.2017.12256.5291 FA G. A. Sheikhzadeh Department of Mechanical Engineering, University of Kashan, Kashan, Iran 0000-0002-7874-9981 M. Sepehrnia Department of Mechanical Engineering, University of Kashan, Kashan, Iran 0000-0002-2950-1111 M. Rezaie Department of Mechanical Engineering, University of Kashan, Kashan, Iran M. Mollamahdi Department of Mechanical Engineering, University of Kashan, Kashan, Iran Journal Article 2016 12 17 Natural convection heat transfer of Al2O3-water nanofluid with variable properties in the turbulent flow inside a cavity with a heat source and heat sink on the vertical walls is studied numerically. Base fluid viscosity, thermal conductivity, and viscosity of nanofluids, are a function of temperature and volume fraction. The governing equations in the two-dimensional space are discretized using the control volume method. Turbulence computations are performed using the k-w-SST model. The results show that change in the placement of heat source and heat sink and Raleigh number have the effect on streamlines and isotherms. For Rayleigh numbers 107 and 108, the Nusselt number increases with increasing volume fraction of nanoparticles to 1%, and then decreases with increasing volume fraction of nanoparticles. Also, for some cases it is observed that the Nusselt number of nanofluids is less than the base fluid and therefore in these cases using nanofluids for enhanced heat transfer is not proposed. For Rayleigh numbers 107 and 108, the least Nusselt number occurs in top-bottom case, and the most Nusselt number occurs in bottom – bottom case. Natural convection heat transfer of Al2O3-water nanofluid with variable properties in the turbulent flow inside a cavity with a heat source and heat sink on the vertical walls is studied numerically. Base fluid viscosity, thermal conductivity, and viscosity of nanofluids, are a function of temperature and volume fraction. The governing equations in the two-dimensional space are discretized using the control volume method. Turbulence computations are performed using the k-w-SST model. The results show that change in the placement of heat source and heat sink and Raleigh number have the effect on streamlines and isotherms. For Rayleigh numbers 107 and 108, the Nusselt number increases with increasing volume fraction of nanoparticles to 1%, and then decreases with increasing volume fraction of nanoparticles. Also, for some cases it is observed that the Nusselt number of nanofluids is less than the base fluid and therefore in these cases using nanofluids for enhanced heat transfer is not proposed. For Rayleigh numbers 107 and 108, the least Nusselt number occurs in top-bottom case, and the most Nusselt number occurs in bottom – bottom case. https://mej.aut.ac.ir/article_1086_d91d1b4d82419de8a614abce9cc0e6d4.pdf