Engineering topics

Conboy, Thomas M.

Publications and source records attributed to Conboy, Thomas M..

4 records

DOE OSTI2013

Scaling considerations for a multi-megawatt class supercritical CO2 brayton cycle and commercialization.

Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

Fleming, Darryn D.↗

DOE OSTI2012

Supercritical CO 2 recompression Brayton cycle: completed assembly description

Through multi-year funding from DOE-NE, Sandia National Labs supercritical carbon dioxide (SCO 2 ) closed Brayton cycle (CBC) research and development team have recently overseen the completion of the SCO 2 CBC recompression test assembly (TA), and delivery from the development contractor’s facility to Sandia, Albuquerque. The primary components of the completed TA include two turbo alternator-compressors and associated motor/controllers, three printed circuit heat exchangers, and six shell-and-tube heaters and associated controllers. Principal supporting components include a cooling tower, electricity-dissipating load bank, and leakage flow management equipment. With this milestone completed, significant increase in CBC R&D is anticipated with the objective of advancing the technology readiness level of components seen by industry as immature. This report presents detailed descriptions of all components and operating software necessary to operate the recompression CBC.

Pasch, James Jay↗

DOE OSTI2012

High-Temperature Split-Flow Recompression Brayton Cycle Initial Test Results

Supercritical CO 2 (S-CO 2 ) power plants offer the potential for better economics because of their small size, use of standard materials, and improved electrical power conversion efficiency at modest temperature (400–750°C). Sandia National Laboratories (SNL or Sandia) and the U.S. Department of Energy Office of Nuclear Energy (DOE-NE) are operating a supercritical CO 2 Brayton cycle power system—the Generation IV (Gen IV) split-flow S-CO 2 compressor test loop—currently located in Arvada Colorado, at Barber Nichols, Inc., under contract to Sandia. A photograph of the upgraded loop is shown in Figure E-1. This system is one of the first S-CO 2 power-producing Brayton cycles operating in the world. This report provides a summary of the newly installed hardware and briefly describes some of the test results that were performed in the upgraded split-flow Brayton loop during June and July of 2011. The Gen IV S-CO 2 split-flow Brayton loop was reconfigured to operate as a simple heated recuperated Brayton loop for the testing in this report period. The test loop had just concluded a phase of construction that substantially increased the capability of the loop by adding heaters, a high-temperature (HT) recuperator, more waste heat removal capability, high-power load banks, larger diameter piping with more bends to reduce thermal stress, and more capable scavenging pumps to reduce windage and friction within the turbomachinery and provide greater cooling capabilities. With these additions, the loop greatly increased its capacity for electrical power generation (30–80 kWe per generator, depending on the loop configuration) and its ability to reach high temperatures (up to 810 K [1000°F]). In recent weeks of testing, the test facility began to realize this potential by achieving new records in turbine inlet temperature (615 K [650°F]), shaft speed (52,000 rpm), pressure ratio (1.65), flow rate (2.7 kg/s), and electrical power generated (20 kWe). These operating conditions still remain short of design conditions for each turbine—an inlet temperature of 810 K (1000°F), a pressure ratio of 1.8, a shaft speed of 75,000 rpm, a flow rate of 3.5 kg/s, and a maximum generator power of 125 kWe—but they are beginning to be approached. Not all planned upgrades were implemented due to the limited funding profile of FY2010. Only 520 kW of heater power were installed—not the total 780 kW. Furthermore, because one of the heater controllers was not functioning, only 390 kW of heater power were available. Similarly, the 3-in. piping was installed only in the high-pressure leg of the loop, not in the low-pressure leg, as was originally planned. We also had to rely on the new load bank capability for rapid shutdown situations, and were not able to install a dedicated shutdown resistor. Nevertheless, in spite of these limitations, we operated the loop at record operating conditions and were largely limited only by the facility and support equipment—not the turbomachinery.

Wright, Steven Alan↗

DOE OSTI2012

Metal Corrosion in a Supercritical Carbon Dioxide - Liquid Sodium Power Cycle

A liquid sodium cooled fast reactor coupled to a supercritical carbon dioxide Brayton power cycle is a promising combination for the next generation nuclear power production process. For optimum efficiency, a microchannel heat exchanger, constructed by diffusion bonding, can be used for heat transfer from the liquid sodium reactor coolant to the supercritical carbon dioxide. In this work, we have reviewed the literature on corrosion of metals in liquid sodium and carbon dioxide. The main conclusions are (1) pure, dry CO 2 is virtually inert but can be highly corrosive in the presence of even ppm concentrations of water, (2) carburization and decarburization are very significant mechanism for corrosion in liquid sodium especially at high temperature and the mechanism is not well understood, and (3) very little information could be located on corrosion of diffusion bonded metals. Significantly more research is needed in all of these areas.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗