Simulation of nano-fluids convective heat transfer from a spherical surface

Heat transfer from surfaces of the sphere is the most important topics in chemical engineering and industry. In this paper, heat transfer rate from these surfaces were studied by computational fluid dynamics (CFD). The effect of nano-particles concentrations and kinds on the rate of heat transfer was investigated numerically. Different models were used in order to access optimum results in simulations. The results of these simulations were compared with the well-known empirical relationships and showed a good adaptation. Finally, the RNG k-&epsilon model was chosen to simulate the heat transfer from spherical surface in the turbulent regimes. Nano-fluid with different kinds of nano-particle as well as various concentrations was used to improve the heat transfer rate from spherical surfaces. The results showed that heat transfer rate was improved by using nano-fluids. Heat transfer rate increased with increasing nano-particle concentrations. At low Reynolds number, the nano-particles effect was significant. The enhancement in heat transfer rate was negligible when using the nano-particle with lower thermal conductivity. Nusselt numbers were not change with the nano-particles concentrations at constant Reynolds numbers. The Nusselt numbers also increased by Reynolds numbers.