Three-dimensional Numerical Study on Turbulent Mixed Convection in Parabolic Trough Solar Receiver Tube

The present work focuses on the fully developed mixed turbulent flow and heat transfer in receiver tube heated by non-uniform heat flux, especially the effect of local buoyancy force induced by the non-uniform heat flux at Reynolds number of 2×104-105, Prandtl number of 1.5 and Grashof number of 0-1012. The friction factor and Nusselt number between forced convection and mixed convection under uniform heat flux and non-uniform heat flux are analyzed quantitatively. The effect of solar elevation angel on the fluid flow and heat transfer is also investigated. We found that it is not feasible to perform the heat transfer design and prediction for parabolic trough solar collector based on the experimental correlations for forced convection or traditional mixed convention.