Numerical Study of Pressure Drop and Thermal Characteristics of Al2O3-Water Nanofluid Flow in Horizontal Annuli

In this paper the results of numerical study of the mixed convection heat transfer of Al2O3-water nanofluid in a horizontal annuli are presented. Steady, laminar flows in symmetric configurations are considered. Single-phase fluid approach is adopted for nanofluid modeling. The governing equations are discretized using the finite-volume method. A SIMPLE-like algorithm has been applied for pressure-velocity coupling on the collocated arrangement. In order to validate the code performance, the numerical results are compared with those available in the literature and good agreement is achieved. The effects of some important parameters such as nanoparticle volume fraction, aspect ratio, Grashof number, and heat flux ratio are studied and discussed in detail. In general, it is observed that the local Nusselt number increases with increase in nanoparticle concentration, Grashof number, and radius ratio. However, when increasing the nanoparticle concentration there are considerable increments in pressure drop and pumping power, which are not desirable. On the other hand, changes in the skin friction coefficient are negligible.