Numerical investigation of free convection around a pair of vertically-aligned isothermally-heated vertical hollow cylinders

Abstract

Efforts are made to delineate the free convection analysis numerically from a pair of vertically attached vertical hollow isothermally heated cylinders with negligible wall thickness immersed in the air within the laminar flow regimes. Thermofluidic behavior around the cylinders is characterized in detail by employing the influence of several relevant dimensionless parameters such as, Rayleigh number (103 ≤ ≤ 107), spacing-to-length ratio and upper to lower cylinder diameter ratio Importantly, heat transfer and fluid flow patterns around the upper cylinder due to the presence of a lower cylinder are thoroughly elucidated, which is not fully understood in the existing literature. It is seen that the enhancement of heat transfer rate from the inner surface is greatly influenced at for lower value of and A linear growth and non-linear reduction patterns against are observed for Nusselt numbers for inner and outer walls, respectively, for fixed value of and Lastly, a suitable correlation has been proposed for net average Nusselt number as a function of relevant input dimensionless parameters. The correlation shows an excellent agreement with the computed data points within ±6%. This correlation is also expected to be helpful for the relevant engineering calculations and provide values for various academic and industrial purposes.