Natural convection heat transfer between two horizontal concentric cylinders with two fins attached to the inner cylinder was numerically investigated using finite element technique together with SIMPLER algorithm. Laminar conditions up to Rayleigh number Rai of 5×10 4 were investigated as well as effects of annulus diameter ratio, fin length and fin inclination angle on this type of flow. A conduction thermal resistance of finned annulus was obtained by means of conduction heat transfer analysis.

Purpose – The aim is to study the effects of fin conductivity ratio, Darcy number, and Rayleigh number on the average Nusselt number for fins made of porous material when attached to the inner cylinder of the annulus between two concentric cylinders. The paper also aims to compare the results with those obtained using solid fins over a range of Rayleigh numbers.

Effect of nanoparticles on natural convection in horizontal cylindrical annuli was investigated numerically using finite volume technique together with SIMPLE algorithm. Annulus geometric configurations of Do/Di = 2 and 1.25 were investigated. The nanofluid used in current simulation is aluminum oxide (Al2O3) nanoparticles in water as base fluid. Laminar conditions up to Rayleigh number R of 109 were investigated 0, 1 and 4% nanoparticle concentration. The data of heat transfer, represented by effective thermal conductivity ratio were presented versus Rayleigh number Ra.

Two dimensional turbulent convective heat transfer behavior of alumina (Al2O3) nanoparticle dispersion in water flow in a horizontal circular pipe at constant wall temperature is investigated numerically.  The computational procedure is based on the finite-volume technique.  Three stream velocities corresponding to 5000 < Re < 4x106 and five different concentrations of nanoparticle (0, 1, 2, 4, and 6%) are studied.  The full range of flow at the entrance length and the fully developed are considered.  The shear stress are observed to increase at any x station along the pipe as the con