A new calorimetric facility to investigate radiative-convective heat exchangers for concentrated solar power applications

Abstract

A new calorimetric facility for the aerothermal assessment of radiative-convective heat exchangers in concentrating solar power applications has been developed and is described in this paper. The configuration of volumetric solar receivers enables concentrated sunlight to be absorbed and conducted within their solid volume, from where it is gradually transferred by forced convection to a heat transfer fluid flowing through their structure. Current design trends towards higher thermal conversion efficiencies have led to the use of complex intricate geometries to maximise temperatures deep inside the structure. The work presented aims to aid these objectives by commissioning a new experimental facility for the fully integrated evaluation of such components. The facility is composed of a high-flux solar simulator that provides 1.2 kW of radiative power, a radiation homogeniser, inlet and outlet collector modules, and a working section that can accommodate volumetric receivers up to 80 mm × 80 mm in aperture. Irradiance levels and flow field nondimensional governing parameters are highly representative of on-sun experiments at larger scales. Results from experiments with a siliconised silicon carbide monolithic honeycomb are presented, conducted at realistic conditions of incident radiative power per unit mass flow rate to validate its design point operation. Measurements conducted include absorber solid temperature distributions, air inlet and outlet temperatures, pressure drop, incident heat flux, and overall thermal efficiency. The relative influence of different sources of thermal loss is analysed and discussed.