A comprehensive and fully predictive discrete methodology for volumetric solar receivers: application to a functional parabolic dish solar collector system

Abstract

A comprehensive modeling approach is herein presented for accurate and reliable numerical predictions of the optical, hydrodynamic, and thermal performance of concentrating solar collector systems. The methodology is applied to investigate the performance of a particular and fully functional parabolic dish solar collector system fitted with a volumetric absorber (open-cell foam). At the receiver level, the methodology establishes a full and consistent coupling between the three-dimensional discrete hydrothermal model and the three-dimensional discrete solar flux model – the same receiver geometrical fidelity can be considered for both simulation stages. The receiver hydrothermal model relies on pore-scale numerical simulations of the heat transfer fluid flow, conjugate heat transfer, and radiative heat transfer. The collector solar flux model is based on the Monte Carlo ray tracing technique taking into account the solar insolation characteristics, the role of the concentrator device, and the detailed geometrical representation of the intricate absorber structure. Best practice guidelines for applying the current methodology are provided. The models comprising the overall methodology are validated against benchmark data. The results from the methodology application show specific absorber regions – namely, near the absorber front (irradiated) section – with relatively higher temperatures that are promoted by local geometric features of the absorber structure and are responsible to increase emission losses. This evidence could not be realized through the volume-averaging modeling approach. The results also support the inability of local thermal equilibrium models and the surface approach for the incoming concentrated solar radiation to accurately predict the receiver hydrothermal performance.