Experimental and numerical investigation on natural convection heat transfer characteristics of vertical 3-D externally finned tubes

Abstract

Tubular heat exchangers for natural convection can be found in many industrial applications. In order to develop the high-efficiency natural convection radiator, the heat dissipation characteristics of vertically oriented 3-dimensional (3-D) finned tubes under the condition of non-forced convection were studied experimentally. The airflow and temperature distribution outside the tubes were analyzed by computational fluid dynamics. Results showed that the 3-D finned tube with fin height of 7 mm achieved the highest Nusselt number, which was up to 207% higher than that of a smooth tube. Nusselt numbers increased with the increasing of the fin height and the decreasing of the axial fin pitch, but were minimally affected by fin width and circular fin pitch. For comparison, the most important fin geometric parameter that affects the heat dissipation is the fin height. Finally, an empirical correlation for predicting Nusselt number was obtained based on the experimental data, which can be used in practical design.