Numerical study of heat transfer of U-shaped enclosure containing nanofluids in a porous medium using two-phase mixture method
Mohammad Hemmat Esfe, Hossein Rostamian, Davood Toghraie, Maboud Hekmatifar, Amir Taghavi Khalil Abad
Abstract
The free convection in a porous U-shaped shield containing Al2O3/H2O nanofluid (NF) was examined using the two-phase (tp) mixture method. The results showed that the heat transfer (HT) rate and average Nusselt number (Nuavg) were amended by increasing the volume fraction (φ) of Al2O3 nanoparticles (NPs). An enhancement in Rayleigh number (Ra number) led to the turbulence of the NF flow; therefore, the Nuavg enhanced. Moreover, adding Al2O3 NPs to the base fluid (water) enhanced the fluid conductivity, resulting in the increase of Nuavg In this study, the results of the tp method were compared with the single-phase (sp) metrhod. It was concluded that the single-phase method is described the effects of the NPs appropriately, but it could not correctly represent the performance of NP. The buoyancy force was weak at a low Ra numbers (such as Ra = 1000). Therefore, the arrangement of isotherms is remained unchanged. However, in large quantities such as Ra = 100000, the buoyancy force is increased; so, the uniform order and arrangement of the isotherms are disturbed.