TESTING an‎d ANALYSIS OF LOW PRESSURE, TRANSPARENT TUBE SOLAR RECEIVER FOR THE SUNSPOT CYCLE

This paper proposes a low pressure tubular solar receiver for a solarized gas turbine. The receiver comprises of concentric tubes with a transparent outer tube, and the annular space is filled with a porous medium. Air is heated by concentrated solar radiation as it flows through the porous medium. To proof our concept, a single 1.5 m long tube was tested on an existing eight mirror linear Fresnel collector, and test data is documented. A temperature increase of about 40 °C was recorder for a concentration ratio of 7:1 and superficial velocity of 1 m/s. Volumetric absorption was a disappointingly low 28 %, mainly due to the low packing factor and reflection of sunlight from the tube’s outer surface. A computational fluid dynamics (CFD) model of the test set-up was used to extract the extinction and absorption coefficients of the porous medium, by fitting a quadratic response surface through the mean square errors between experimental and CFD data. Our analysis indicates that we can increase receiver efficiency significantly through raising the packing factor and applying and anti-reflection coating to the tube surface.