Characterisation of the Wind Convection Losses in Plain and Ribbed Tubes of Solar Central Receivers via Tube-Resolved CFD Simulations

Convective losses due to wind affect the thermal efficiency of external central receivers of solar power towers (SPT), but their full characterization is still an unresolved question. Furthermore, detailed assessment of these convective losses in new designs, such ribbed tube central receivers, is nearly inexistent. The aim of this study is (a) to parameterize the wind convection coefficient and its local distribution in all the tubes and panels of an external central receiver, and (b) to compare the wind convection coefficients in conventional plain tube receivers and in ribbed tubes receivers designed to enhance heat transfer from the tube wall to the heat transfer fluid (HTF). To gain a detailed understanding of the complex heat transfer phenomena involved, this work is entirely developed through Computational Fluid Dynamics (CFD) simulations in a three-dimensional (3D) domain that describes all the absorber tubes in the receiver. Overall results of the simulations are practically validated against experimental results available in the literature [1].