Simulation of an innovative internal design of a plate solar receiver: Comparison between RANS and LES results

• An innovative concept for internal geometry of asymmetric heat exchanger is studied.
• It is composed of vortex generators followed by longitudinal riblets.
• A LES simulation is carried out to study the flow and thermal behaviour.
• A comparison with a RANS simulation is carried out.
• It shows its limits for predicting the hydraulic and thermal behaviour of this flow.

This work focuses on the simulation of the internal structure of a plate solar receiver with asymmetrical heating. The receiver examined in this paper is irradiated by concentrated sunlight and heats up pressurised air to high temperature. Solar receivers, in the same way as some other industrial heat exchangers, are heated asymmetrically due to one-sided solar irradiation. A previous paper studied a plate solar receiver designed with fins. In this paper, the forced internal convective heat transfer and friction loss behaviours inside the receiver are studied for turbulent flows generated by a combination of delta-winglet vortex generators and longitudinal riblets. Steady-state Reynolds Averaged Navier Stokes (RANS) simulations were first carried out for this kind of geometry. Subsequently, the fluctuations and the thin structures of the flow field were studied with a Large Eddy Scale simulation (LES). LES results allow for a better understanding of the behaviour of the generated vortices and thermal exchanges are modelled more accurately. A comparison between LES and RANS results shows that RANS simulation misrepresents the behaviour of the vortices generated by the vortex generators, which leads to an overestimation of pressure loss and thermal exchanges.