INVESTIGATION THE EFFECT OF ASPECT RATIO ON THE FREE HEAT CONVECTIVE INSIDE A HORIZONTAL HEATED TUBE

Abstract

In this work, an experimental investigation has been done for steady-state free heat convection into a heated externally horizontal open ends circular tube with and without internal ring fins. The tests are carried out for five different aluminum tubes in aspect ratios. Another four tubes are used providing internal ring fins with varying fin spacing and constant aspect ratio . Wide levels of the wall heat fluxes (254 - 2267) W/m2 are used. The influence of aspect ratio , heat flux , ring fins , fin spacing on the free-convection through a heated tube are analyzed and discussed. The experimental results indicate that the local Nusselt number increases with decreasing the aspect ratio. Also the results appear that the free heat convection performance through the tube in terms of local Nusselt number improved with internal fins about 25% higher than without fins. An experimental correlations of local and average Nusselt numbers as a function of Rayleigh number for a wide range of aspect ratios under uniform wall heat flux condition are concluded.

Keywords

• horizontal tube
• free-convection
• internal ring fins
• experimental investigation
• aspect ratio