| Abstract: | Natural convection heat transfer between concentric rectangular pipes was studied numerically. It has been found that rolls of even numbers form in the region on the top surface of the inner pipe. The number of rolls depends on both the Rayleigh number and the aspect ratio. An oblong circulation of flow forms in the region between the side surface of the inner pipe and the surface of the outer pipe. The aspect ratio does not have much effect on the average Nusselt number at the side surface of the inner pipe. The relation between the Nusselt and Rayleigh numbers at the top surface resembles that of the Rayleigh-Bénard convection obtained by Silveston (Chandrasekhar, S. 1961. Hydrodynamic and Hydromagnetic Stability, Oxford University Press, 68). The average Nusselt number at the bottom surface of the inner pipe decreases with increasing aspect ratio because the region where heat transfer is affected significantly by convection is limited. © 1998 Scripta Technica, Heat Trans Jpn Res, 27(4): 271–283, 1998 |
