Conjugate steady natural convection analysis around thick tapered vertical pipe suspended in the air

A computational study has been performed in order to characterize the free convection heat transfer around the thick tapered vertical tube (decreasing or increasing or uniform cross-section) with a constant inner surface temperature. Simulations are carried out by varying Rayleigh number ( Ra ) within the laminar range (10 4 ≤ Ra ≤ 10 8 ). Moreover, the geometrical and thermal parametric variations, namely, slant height to thickness ratio (5 ≤ L/B ≤ 20), diameter ratio (0.25 ≤ d 1 /d 2 ≤ 1.75) and thermal conductivity of the tube material ( K s ) are employed to obtain the pattern of the heat removal rate and flow field around thick pipe. Mass flow rate through the pipe is also estimated for different diameter ratio. Velocity vectors are shown to predict the flow behavior around the tapered pipe. It is found that the low value of velocity at core of the pipe for low d 1 /d 2 in comparison to high d 1 /d 2 . A correlation has been developed in order to predict the average Nusselt number in terms of geometrical and thermal parameters based on the computed data points which would be useful for the industrial purposes.