Numerical study of the natural convection of nanofluids based on mineral oil with properties evaluated experimentally

This paper deals with the numerical simulation of natural convection inside a closed cavity of multi-walled carbon nanotubes and diamond nanoparticles dispersed in pure mineral oil. The data of the thermal conductivity and viscosity of the nanofluids were obtained experimentally, while specific heat and density were evaluated by the first law of thermodynamic and mass conservation principle, respectively. The physical model considered is a 2D cavity with adiabatic horizontal walls, where the left vertical wall with high temperature and the right vertical wall with low temperature and all walls with no-slip boundary conditions. The simulations were performed in a numerical code based on the Finite Volume Method-FVM, where second order temporal and spatial schemes were used. The results showed that only the Nusselt number for MWCNT based nanofluids increased in comparison to the mineral oil for the same Grashof number. However, the comparison between the convective coefficient for nanofluids and mineral oil showed that nanofluids presented better convection characteristics, for the same Grashof number. Furthermore, the diamond nanofluid with higher volumetric concentration presented the maximum increase of the convection coefficient, about 23%, though this nanofluid did not presentthe higher Nusselt number in comparison to the other nanofluids analyzed.