We have designed and tested a prototype dish/Stirling hybrid-receiver combustion system. The system consists of a pre-mixed natural-gas burner heating a pin-finned sodium heat pipe. The design emphasizes simplicity, low cost, and ruggedness. Our test was on a 1/6th-scale device, with a nominal firing rate of 18kWt, a power throughput of 13kWt, and a sodium vapor temperature of 750°C. The air/fuel mixture was electrically preheated to 640°C to simulate recuperation. The test rig was instrumented for temperatures, pressures, flow rates, overall leak rate, and exhaust emissions. The data verify our burner and heat-transfer models. Performance and post-test examinations validate our choice of materials and fabrication methods.
Based on the 1/6th -scale results, we are designing a full-scale hybrid receiver. This is a fully-integrated system, including burner, pin-fin primary heat exchanger, recuperator (in place of the electrical pre-heater used in the prototype system), solar absorber, and sodium heat pipe. The major challenges of the design are to avoid pre-ignition, achieve robust heat-pipe performance, and attain long life of the burner matrix, recuperator, and flue-gas seals. We have used computational fluid dynamics extensively in designing to avoid pre-ignition and for designing the heat-pipe wick, and we have used individual component tests and results of the 1/6th -scale test to optimize for long life.
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.
In this paper, we present our design philosophy and basic details of our design. We describe the sub-scale test rig and compare test results with predictions. Finally, we outline the evolution of our full-scale design, and present its current status.