Thermal Analyses of Heated Horizontal Cylinder Mounted in Vertical Circular Duct

Abstract

An experimental study is performed to investigate the heat transfer characteristics of the unsteady natural convection over a horizontal cylinder heated in air. During the heater power-on transient operations, the effect of heat transfer on the circumference of the cylinder is observed. Surface heat transfer distributions around the circumference of the cylinders are presented for Rayleigh numbers of 4.13×10⁴ to 4.35×10⁴ and a range of different angular position of the thermocouple (0\(^{\circ}\), 90\(^{\circ}\), 180\(^{\circ}\)) are investigated. It is documented that the radiation heat transfer contributes 1/3 of the total heat transfer convection heat transfer. The dependence of the average Nusselt number on Rayleigh number is compared favorably with those obtained from the literature. The findings also indicate that the position of the thermocouples has a significant impact on the transient heat transfer around the cylinder. The transient heat transfer obtained at 90\(^{\circ}\) and 180\(^{\circ}\) is greater than the heat transfer obtained at the stagnation point (0\(^{\circ}\)). Finally, correlations are reported to predict the surface heat transfer behavior of the horizontal cylinder.