The effect of inclination angle of finned cylinders upon free convection heat transfer

Abstract

An experimental and theoretical study of the free heat transfer from three cylinders finned with spiral fins arranged in vertical array and fixed between two plates. Three fin cylinders made of (steel iron), of outer diameter (12 mm), inner diameter (10 mm), fins diameter (30 mm). The inclination angle of the cylinders was changed to four angles (0°, 30°, 60° and 90°), four thermal flux levels were tested (121.16, 278.8, 497.9 and 792.5) W / m2. Study was conducted for a range of Rayleigh number (121.16, 278.8, 497.9, and 792.5) in open space to surrounding air where heat is carried by a convection and radiation. Theoretical study was done using ANSYS Fluent 18 to simulate the practical side. Experimental results found that the Nusselt number value of the finned cylinders was maximum value at the angle (30°) with low heat flux levels (121.16, 278.8) ) W / m2, but at the high heat flux levels ( 497.9, 792.5 ) W / m2 the best angle which give the maximum value of Nusselt number was angle (60°). Theoretical results of heat transfer coefficient were convergent with experimental results with a small difference rate does not exceed 8%, due to the difference in the theoretical and experimental working conditions as the theoretical work was in ideal conditions either the experimental work under the natural laboratory conditions.