Numerical Modelling of a Linear-Fresnel-Collector’s Receiver Optimized for Equatorial Regions Using Ansys Fluent

This document outlines the numerical simulation of a Fresnel-type solar receiver developed within a broader project at Escuela Politécnica Nacional (EPN) in Quito, Ecuador, that involves implementing a low-concentration, mid-range-temperature linear Fresnel collector on campus, which is located very close to the equator. Therefore, the receiver was optimized for equatorial regions with input of validated radiation data from the local Typical Meteorological Year. The receiver comprises an absorber and two reflectors in a trapezoidal configuration, all enclosed by a glass cover. The top absorber has a high-selective coating, while the aluminum reflectors offer high reflectivity. Radiative effects were computed using the Discrete-Ordinates model. To emulate the greenhouse effect of the glass, a two-spectral-band model (2500 nm breakpoint) was applied. Absorber and reflectors were modeled as opaque surfaces, while the glass was semi-transparent. For glass absorption and scattering, a non-gray model distinguished properties in the two bands. Likewise, natural convection for air inside the receiver was modeled with an ideal-gas fully-compressible formulation. The analysis found a maximum absorber temperature of 418.2 K at low mass-flow rates and high water-stream temperatures, contrasting with 386.72 K obtained by Ordóñez & Jaramillo [1] under 2 m/s and an inlet of 348 K. Absorber temperature inversely correlated with mass-flow rate and directly with water stream temperature. The angular discretization study revealed no significant differences in the number of angular divisions for the Discrete Ordinates model. A grid sensitivity analysis confirmed stable absorber temperatures with a 40,500-cell mesh, despite minor variations.