Visualization of natural convection heat transfer inside an inclined circular pipe

Natural convection heat transfer inside an inclined pipe was visualized. Based on the analogy, mass transfer experiments were conducted instead of heat transfer ones using an electroplating system. The inclination (θ), diameter (D), and the length (L) of the pipe were varied 0° ~ 90°, 0.026 m ~ 0.063 m and 0.1 m ~ 0.3 m, respectively. The Ra_D ranged from 2.98 × 10⁹ to 4.22 × 10¹⁰ and the Sc was 2094. The circumferential and axial flows interact with each other, which causes the complex internal flows inside the inclined pipe. The different copper plating patterns were appeared depending on the inclination (θ), diameter (D), and the length (L) and their influences on heat transfer inside the pipe were analyzed.