Experimental study of natural convection from vertical cylinders with branched fins

Abstract In this paper, we experimentally investigate natural convection from vertical cylinders with branched plate fins. Various branch angles, fin numbers, and base temperatures are examined. From the experimental data, we propose a correlation for estimating the Nusselt number, which is applicable when the Rayleigh number, branch angle, and fin number are in the ranges 100,000–600,000, 10–40°, and 9–36, respectively. Using the correlation, we prepare a contour map depicting the thermal resistance as a function of the fin number and fin thickness. The contour map shows that the fin number and fin thickness at which the thermal resistance is minimized exist. Finally, we compare the thermal resistances of cylinders with branched fins and conventional plate fins and find that cylinders with branched fins exhibit thermal resistances up to 36% lower than those of cylinders with plate fins.