Experimental characterization of a halogen solar simulator and performance evaluation of a cavity receiver

This thesis reports the experimental characterisation of an indoor solar simulator and an open volumetric cavity receiver developed at the DESTeC laboratory of the University of Pisa. The simulator is based on a 1000 W tungsten-halogen lamp and an elliptical reflector, and the receiver is a 3D-printed stainless-steel honeycomb matrix housed in a small cavity. A flat-plate copper calorimeter was used both to characterise the radiant output of the lamp and to measure the optical efficiency of four reflector configurations. The reference incident power at the receiver aperture is 172 W and is used as the basis for all receiver efficiencies reported. The most significant experimental result is that reversing the direction of the airflow through the honeycomb matrix increases the receiver efficiency from 42.0 % to 46.7 % at 5 Nm³/h and produces a temperature signature (T_core > T_out) that is the direct fingerprint of a volumetric absorber. A single-channel CFD analysis of the honeycomb was carried out in ANSYS CFX to test whether this signature could be reproduced from first principles. The model reproduces the normal-flow outlet temperature within 3 °C at every flow rate above 4 Nm³/h and qualitatively reproduces the volumetric signature under reversed flow at four of the five flow rates studied. The remaining quantitative gap is attributed to radiation transport inside the honeycomb that the current model does not resolve.