The effectt of the separation distance of the external body on natural convection reduction from a horizontal circular cylinder

Abstract

presence of an external body in the way of the air on the heat transfer results. The experimental setup consists of an aluminum cylinder as test section with 28 mm inside diameter and 450 mm heated length, which is subjected to a constant wall heat flux boundary condition. The Rayleigh number in this investigation was ranged from 1.08*105 to 5.8*106. Four external bodies have been used with different separation distances parameter (L/D) 1.155, 1.44, 1.77 and 2.0. The results have shown a considerable percentage of heat transfer reduction when the separation distance (L) is greater than 1/3 of the cylinder diameter while the heat transfer process suffers appreciable reduction as the separation distance (L) is less than 1/3 of the cylinder diameter. It was concluded that there is no an appreciable effect on the heat transfer reduction when the separation distance parameter (L/D) is greater than 1.77. The average Nusselt numbers were correlated with the Rayleigh numbers with empirical correlations. The results were compared with the results of a free horizontal cylinder without external body presence.