Numerical simulation on mixed convection in receiver tube of parabolic solar collector

A numerical study on mixed convection of super-heated steam at pressure of 10 MPa in receiver tube of parabolic solar collector under uniform and non-uniform heat flux boundary conditions has been conducted. The numerical results show that, compared with forced convection, the friction factor increases 21%~133% and the Nusselt number increases 48%~261% for mixed laminar flow, while the friction factor increases 7%~236% and the Nusselt number increases 6%~150% for mixed turbulent flow. Especially, the buoyancy effect on the flow and heat transfer is more remarkable under non-uniform heat flux boundary condition. The traditional criterion on mixed convection should be corrected.