A Study of Free Convective Heat Transfer in a Horizontal Annulus With a Large Radii Ratio

Abstract

Steady laminar natural convective heat transfer in a horizontal annulus with a large radii ratio (R) of 11.4 (and inner-cylinder diameter Di of 1.27 cm) has been investigated. Experimental data for air, glycerin, and mercury in the ranges of 0.023 ≤ Pr ≤ 10,000 and 0.03 ≤ GrDi ≤ 3 × 106 are reported. The influence of the variation of fluid properties as compared to the usual assumption of constant fluid properties has been explored numerically for air and glycerin. The heat transfer computations for air do not change with variation of fluid properties, whereas for glycerin significant differences in the local heat transfer distributions and flow patterns are observed. The experimental data have been correlated with some other data from the literature for smaller values of R, and it has been shown that the heat transfer from the inner cylinder should be almost the same as that in an infinite medium when R ≥ 10.