Three-dimensional CFD modelling and thermal performance analysis of porous volumetric receivers coupled to solar concentration systems

Porous volumetric receivers is a promising technology to improve the thermal performance of a new generation of concentrated solar power (CSP) plants. In this sense, this work addresses the Computational Fluid Dynamics (CFD) modelling and thermal performance analysis of porous volumetric receivers coupled to solar concentration systems. A cylindrical receiver element made of open-cell SiC ceramic foam was considered. The fluid flow and heat transfer processes in the porous media are modelled through volume averaged mass, momentum and energy conservation equations, considering the local thermal non-equilibrium (LTNE) approach, while the thermal radiation transfer is described by the P1 spherical harmonics method, using an open source software (OpenFOAM). An in-house algorithm based on the Monte Carlo Ray Tracing (MCRT) method was developed and coupled to the CFD mesh to model the propagation and absorption of solar radiation. The modelling of the receiver boundary conditions were improved, and a detailed analysis of a reference configuration of the receiver was conducted using a parabolic dish with a concentration ratio of 500 to generate the concentrated solar radiation field and a receiver element with diameter 5 cm, height 5 cm, pore size 3 mm and porosity 0.9. The thermal power output, thermal efficiency, mean fluid temperature at the outlet and pressure drop of this reference configuration are 628.92 W, 85.46%,474.22 K and 103.10 Pa, respectively. The use of receivers with high porosity and pores size increases the thermal efficiency slightly and decreases the pressure drop substantially. The convergent incidence of solar rays at the inlet of the receiver leads to high peaks of temperature in the porous structure and fluid, and a way to decrease these peaks is to design the concentration system or place the receiver in such way to obtain lower incidence angles at the inlet.