Laminar natural convective heat transfer in the enclosed evacuated collector tube with east-west symmetric heat input

Heat transfer in the evacuated collector tube is a three-dimensional laminar natural convection problem driven by buoyancy. Because of its complexity, no effective theoretical model is available despite of limited experimental work which is confined to one aspect. The present work aims to depict the convective heat transfer inside a two-ended inclined tube with East-West symmetric heat input using numerical methods. Based on reasonable assumptions, governing equations of the inside fluid axe established. The corresponding discretizated equations are solved by employing numerical methods. The calculated results are displayed for velocity and temperature profiles on different cross-sectional planes, which present the flow pattern characterized by upflow and downflow along the axial direction and adherent flow along the peripheral direction, and the heat transfer process from the wall to the center. Furthermore, the transient Nusselt number and average temperature level are shown and discussed. Finally, the parametric effects of the tube radius and the heat input on the flow and heat transfer are also given.