Numerical investigation of the effect of the T-junction inlet geometry and non-uniform heat flux on the Nusselt numbers and friction factors of the developing flow in a single tube of an evacuated tube collector. The compound effects introduced by the tilt angle and non-uniform heat flux are investigated. A T-junction comprising of the inlet header and a single u-tube leg within the collector, is numerically modelled. To determine the non-uniform heat flux distribution along the circumference of the u-tube, the discrete ordinates model is employed in a 2D:3D phased approach to perform a 2D optical study and 3D thermal study of the collector. The results provide insights into the effects of inlet geometries on the performance of various mechanical systems like solar thermal collectors and heat exchangers.-->-->