ON-SUN TESTING OF A HIGH TEMPERATURE BLADED SOLAR RECEIVER AND TRANSIENT EFFICIENCY EVALUATION USING AIR

Prior research at Sandia National Laboratories showed the potential advantages of using light-trapping features which are not currently used in direct tubular receivers. A horizontal bladed receiver arrangement showed the best potential for increasing the effective solar absorptance by increasing the ratio of effective surface area to the aperture footprint. Previous test results and models of the bladed receiver showed a receiver efficiency increase over a flat receiver panel of 5-7% over a range of average irradiances, while showing that the receiver tubes can withstand temperatures > 800 degrees C with no issues. The bladed receiver is being tested at various peak heat fluxes ranging 75-150 kW/m(2) under transient conditions using Air as a heat transfer fluid at inlet pressure 250 kPa (-36 psi) using a regulating flow loop. The flow loop was designed and tested to maintain a steady mass flow rate for 15 minutes using pressurized bottles as gas supply. Due to the limited flow -time available, a novel transient methodology to evaluate the thermal efficiencies is presented in this work. Computational fluid dynamics (CFD) models are used to predict the temperature distribution and the resulting transient receiver efficiencies. The CFD simulations results using air as heat transfer fluid have been validated experimentally at the National Solar Thermal Test Facility in Sandia National Labs.