Effect of cold wall on laminar free convection across a horizontal cylinder with part adiabatic surface

Abstract

The present dissCl1alion deals with the problem of laminar natural convection around a horizontal cylinder. The external surface of tlllS cylinder IS everywhere isothermal, with the exception of a region, which is adiabatic. The effects Ofvcl1ical cold walls arc also determined. The basic boundary layer equations have been reduced to local Ilonsimilarity equations. Solutions arc obtained employing the perturbation method together with the Runge-Kulla imtml value problem solver, the mtcgral solution method and the finite volume method incorporating the SIMPLE algorithm Oll collocated body fitted grids. Perturbation as well as [mite volume solutions are obtained, respectively, for !lIe leading edge and for the entire regimes. The results obtained are presented in terms of local heat transfer, streamlines, isothemlallines, velocity vectors, velOCItymid temperature profiles. On analysing the heat transfer from the cylinder, it has been found that the intensity decreased and increased lmexpectedly. The.explanation can be given after visualization of flow. 11is ohserved that the fluid near the vertical walls aspirated the layers of hot fluid from the honzontal cylinder. The uplift pressure and the tendency of the system to reach balance cause the thud layers of the similar temperature and density to merge. However, this efTect also found to be dependent on the intensity of the heat transfer. Effects of the aforementioned physical quantities for fluid having differenl Grashof number and Prandtl number have been studied. The effects of thc cold wall and adiabatic part of the cylinder on the flow and thermal fields have also been studied.