Mixed convection with flow reversal in the entrance region of inclined tubes

Purpose – To determine the axial evolution of the hydrodynamic and the thermal fields for mixed convection in inclined tubes and to investigate the presence of flow reversal.Design/methodology/approach – The elliptical, coupled, steady state, three‐dimensional governing partial differential equations for heated ascending laminar mixed convection in an inclined isothermal tube were solved numerically using a finite volume staggered grid approach.Findings – The axial evolution of the velocity profiles and fluid temperatures show that upstream diffusion has an important effect near the inlet of the heating region. As a result, both the wall shear stress and the Nusselt number are affected upstream of the heating zone. Flow reversal occurs of GF≥9 × 105. The shape and size of the region with negative velocities depends strongly on the value of the Grashof number. The effect of the Grashof number on the axial evolution of the wall shear stress and the Nusselt number is shown to be very important in the region ...