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Sample records for cycle gas core

  1. Open cycle gas core nuclear rockets

    NASA Technical Reports Server (NTRS)

    Ragsdale, Robert

    1991-01-01

    The open cycle gas core engine is a nuclear propulsion device. Propulsion is provided by hot hydrogen which is heated directly by thermal radiation from the nuclear fuel. Critical mass is sustained in the uranium plasma in the center. It has typically 30 to 50 kg of fuel. It is a thermal reactor in the sense that fissions are caused by absorption of thermal neutrons. The fast neutrons go out to an external moderator/reflector material and, by collision, slow down to thermal energy levels, and then come back in and cause fission. The hydrogen propellant is stored in a tank. The advantage of the concept is very high specific impulse because you can take the plasma to any temperature desired by increasing the fission level by withdrawing or turning control rods or control drums.

  2. Energetic closed-cycle gas core reactors for orbit raising

    NASA Technical Reports Server (NTRS)

    Rosa, R. J.; Myrabo, L. N.

    1983-01-01

    Closed-cycle gas core reactor power plants can be of two types. In the 'mixed flow' type, the gaseous nuclear fuel is intimately mixed with the working gas in the cavity. In the 'light bulb' type the fissioning plasma is enclosed in a transparent tube, and energy transfer to the separate working gas occurs by thermal radiation. The potentials of high temperature gas core reactors in terrestrial electric power generator applications have been considered, and a number of civilian power-beaming applications for gaseous fuel nuclear-MHD power plants in space have been suggested. Major conclusions of investigations related to the design of space power systems are discussed. Attention is given to options for conversion cycles, the power system specific mass, and research and technology issues.

  3. Gas Core Reactor with Magnetohydrodynamic Power System and Cascading Power Cycle

    SciTech Connect

    Smith, Blair M.; Anghaie, Samim

    2004-03-15

    The U.S. Department of Energy initiative Generation IV aim is to produce an entire nuclear energy production system with next-generation features for certification before 2030. A Generation IV-capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors (LWRs). A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and cascading power cycle forms the basis for a Generation IV concept that is expected to set the upper performance limits in sustainability and power conversion efficiency among all existing and proposed fission powered systems. A gaseous core reactor delivering thousands of megawatt fission power acts as the heat source for a high-temperature MHD power converter. A uranium tetrafluoride fuel mix, with {approx}95% mol fraction helium gas, provides a stable working fluid for the primary MHD Brayton cycle. The hot working fluid exiting a topping cycle MHD generator has sufficient heat to drive a conventional helium Brayton cycle with 35% thermal efficiency as well as a superheated steam Rankine cycle, with up to 40% efficiency, which recovers the waste heat from the intermediate Brayton cycle. A combined cycle efficiency of close to 70% can be achieved with only a modest MHD topping cycle efficiency. The high-temperature direct-energy conversion capability of an MHD dynamo combined with an already sophisticated steam-powered turbine industry knowledge base allows the cascading cycle design to achieve breakthrough first-law energy efficiencies previously unheard of in the nuclear power industry. Although simple in concept, the gas core reactor design has not achieved the state of technological maturity that established high-temperature gas-cooled reactors and high-temperature molten salt core reactors have pioneered. However, the GCR-MHD concept has considerable promise; for example, like molten salt reactors the fuel is continuously cycled

  4. Gas Core Reactor-MHD Power System with Cascading Power Cycle

    SciTech Connect

    Smith, Blair M.; Anghaie, Samim; Knight, Travis W.

    2002-07-01

    The US Department of Energy initiative Gen-IV aim is to produce an entire nuclear energy production system with next generation features for certification before 2030. A Generation 4 capable system must have superior sustainability, safety and reliability, and economic cost advantages in comparison with third generation light water reactors. A gas core reactor (GCR) with magnetohydrodynamic (MHD) power converter and cascading power cycle forms the basis for a Generation IV concept that is expected to set the upper performance limits in sustainability and power conversion efficiency among all existing and proposed fission powered systems. A gaseous core reactor delivering 1000's MW fission power acts as the heat source for a high temperature magnetohydrodynamic power converter. A uranium tetrafluoride fuel mix, with {approx}95% mole fraction helium gas, provides a stable working fluid for the primary MHD-Brayton cycle. A helium Brayton cycle extracts waste heat from the MHD generator with about 20% energy efficiency, but the low temperature side is still hot enough ({approx}1600 K) to drive a second conventional helium Brayton cycle with about 35% efficiency. There is enough heat at the low temperature side of the He-Brayton cycle to generate steam, and so another heat recovery cycle can be added, this time a Rankine steam cycle with up to 40% efficiency. The proof of concept does not require a tremendously efficient (first law) MHD cycle, the high temperature direct energy conversion capability of an MHD dynamo, combined with already sophisticated steam powered turbine industry knowledge base allows the cascading cycle design to achieve break-through first law energy efficiencies previously unheard of in the nuclear power industry. Although simple in concept, the gas core reactor design has not achieved the state of technological maturity that, say, molten salt or high-temperature gas-cooled reactors have pioneered. However, even on paper the GCR-MHD concept holds

  5. The open-cycle gas-core nuclear rocket engine - Some engineering considerations.

    NASA Technical Reports Server (NTRS)

    Taylor, M. F.; Whitmarsh, C. L., Jr.; Sirocky, P. J., Jr.; Iwanczyk, L. C.

    1971-01-01

    A preliminary design study of a conceptual 6000-MW open-cycle gas-core nuclear rocket engine system was made. The engine has a thrust of 44,200 lb and a specific impulse of 4400 sec. The nuclear fuel is uranium-235 and the propellant is hydrogen. Critical fuel mass was calculated for several reactor configurations. Major components of the reactor (reflector, pressure vessel) and the waste heat rejection system were considered conceptually and were sized.

  6. Dynamic analysis of an open-cycle gas-core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Turney, G. E.; Kieffer, A. W.

    1973-01-01

    Reactivity and flow disturbances were used to investigate the transient response of a conceptual open cycle gas core nuclear rocket engine. The disturbances were made with the system initially operating at its steady state design point. Results of the study show that the feedbacks associated with the propellant density and propellant temperature have a dominant effect on the response of the system. Furthermore, there appears to be a rather limited range of values of these propellant feedback coefficients for which the gas core nuclear rocket has a stable response. The system was rather insensitive to a fuel flow rate disturbance, whereas a similar disturbance in the propellant flow rate caused large changes in reactor power. For a similar disturbance in the propellant flow rate caused large changes in reactor power. For most reactivity and flow rate disturbances, the response showed oscillations of various intensity.

  7. Bleed cycle propellant pumping in a gas-core nuclear rocket engine system

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.; Easley, A. J.

    1972-01-01

    The performance of ideal and real staged primary propellant pumps and bleed-powered turbines was calculated for gas-core nuclear rocket engines over a range of operating pressures from 500 to 5000 atm. This study showed that for a required engine operating pressure of 1000 atm the pump work was about 0.8 hp/(lb/sec), the specific impulse penalty resulting from the turbine propellant bleed flow as about 10 percent; and the heat required to preheat the propellant was about 7.8 MN/(lb/sec). For a specific impulse above 2400 sec, there is an excess of energy available in the moderator due to the gamma and neutron heating that occurs there. Possible alternative pumping cycles are the Rankine or Brayton cycles.

  8. Fuel/propellant mixing in an open-cycle gas core nuclear rocket engine

    SciTech Connect

    Guo, X.; Wehrmeyer, J.A.

    1997-01-01

    A numerical investigation of the mixing of gaseous uranium and hydrogen inside an open-cycle gas core nuclear rocket engine (spherical geometry) is presented. The gaseous uranium fuel is injected near the centerline of the spherical engine cavity at a constant mass flow rate, and the hydrogen propellant is injected around the periphery of the engine at a five degree angle to the wall, at a constant mass flow rate. The main objective is to seek ways to minimize the mixing of uranium and hydrogen by choosing a suitable injector geometry for the mixing of light and heavy gas streams. Three different uranium inlet areas are presented, and also three different turbulent models (k-{var_epsilon} model, RNG k-{var_epsilon} model, and RSM model) are investigated. The commercial CFD code, FLUENT, is used to model the flow field. Uranium mole fraction, axial mass flux, and radial mass flux contours are obtained. {copyright} {ital 1997 American Institute of Physics.}

  9. Fuel/propellant mixing in an open-cycle gas core nuclear rocket engine

    NASA Astrophysics Data System (ADS)

    Guo, Xu; Wehrmeyer, Joseph A.

    1997-01-01

    A numerical investigation of the mixing of gaseous uranium and hydrogen inside an open-cycle gas core nuclear rocket engine (spherical geometry) is presented. The gaseous uranium fuel is injected near the centerline of the spherical engine cavity at a constant mass flow rate, and the hydrogen propellant is injected around the periphery of the engine at a five degree angle to the wall, at a constant mass flow rate. The main objective is to seek ways to minimize the mixing of uranium and hydrogen by choosing a suitable injector geometry for the mixing of light and heavy gas streams. Three different uranium inlet areas are presented, and also three different turbulent models (k-ɛ model, RNG k-V model, and RSM model) are investigated. The commercial CFD code, FLUENT, is used to model the flow field. Uranium mole fraction, axial mass flux, and radial mass flux contours are obtained.

  10. Neutronics analysis of an open-cycle high-impulse gas core reactor concept

    NASA Technical Reports Server (NTRS)

    Whitmarsh, C. L., Jr.

    1972-01-01

    A procedure was developed to calculate the critical fuel mass, including the effects of propellant pressure, for coaxial-flow gas-core reactors operating at 196,600 newtons thrust and 4400 seconds specific impulse. Data were generated for a range of cavity diameter, reflector-moderator thickness, and quantity of structural material. Also presented are such core characteristics as upper limits on cavity pressure, spectral hardening in very-high-temperature hydrogen, and reactivity coefficients.

  11. Reactor moderator, pressure vessel, and heat rejection system of an open-cycle gas core nuclear rocket concept

    NASA Technical Reports Server (NTRS)

    Taylor, M. F.; Whitmarsh, C. L., Jr.; Sirocky, P. J., Jr.; Iwanczyke, L. C.

    1973-01-01

    A preliminary design study of a conceptual 6000-megawatt open-cycle gas-core nuclear rocket engine system was made. The engine has a thrust of 196,600 newtons (44,200 lb) and a specific impulse of 4400 seconds. The nuclear fuel is uranium-235 and the propellant is hydrogen. Critical fuel mass was calculated for several reactor configurations. Major components of the reactor (reflector, pressure vessel, and waste heat rejection system) were considered conceptually and were sized.

  12. Effect of buoyancy on fuel containment in an open-cycle gas-core nuclear rocket engine.

    NASA Technical Reports Server (NTRS)

    Putre, H. A.

    1971-01-01

    Analysis aimed at determining the scaling laws for the buoyancy effect on fuel containment in an open-cycle gas-core nuclear rocket engine, so conducted that experimental conditions can be related to engine conditions. The fuel volume fraction in a short coaxial flow cavity is calculated with a programmed numerical solution of the steady Navier-Stokes equations for isothermal, variable density fluid mixing. A dimensionless parameter B, called the Buoyancy number, was found to correlate the fuel volume fraction for large accelerations and various density ratios. This parameter has the value B = 0 for zero acceleration, and B = 350 for typical engine conditions.

  13. Photoionization-Induced Emission of Tunable Few-Cycle Midinfrared Dispersive Waves in Gas-Filled Hollow-Core Photonic Crystal Fibers.

    PubMed

    Novoa, D; Cassataro, M; Travers, J C; Russell, P St J

    2015-07-17

    We propose a scheme for the emission of few-cycle dispersive waves in the midinfrared using hollow-core photonic crystal fibers filled with noble gas. The underlying mechanism is the formation of a plasma cloud by a self-compressed, subcycle pump pulse. The resulting free-electron population modifies the fiber dispersion, allowing phase-matched access to dispersive waves at otherwise inaccessible frequencies, well into the midinfrared. Remarkably, the pulses generated turn out to have durations of the order of two optical cycles. In addition, this ultrafast emission, which occurs even in the absence of a zero dispersion point between pump and midinfrared wavelengths, is tunable over a wide frequency range simply by adjusting the gas pressure. These theoretical results pave the way to a new generation of compact, fiber-based sources of few-cycle midinfrared radiation. PMID:26230794

  14. Variable cycle gas turbine engines

    NASA Technical Reports Server (NTRS)

    Johnson, J. E.; Foster, T. (Inventor)

    1977-01-01

    A technique, method, and apparatus were designed for varying the bypass ratio and modulating the flow of a gas turbine engine in order to achieve improved mixed mission performance. Embodiments include gas flow control system for management of core and bypass stream pressure comprising diverter valve means downstream of the core engine to selectively mix or separate the core and bypass exhaust streams. The flow control system may also include variable geometry means for maintaining the engine inlet airflow at a matched design level at all flight velocities. Earth preferred embodiment thus may be converted from a high specific thrust mixed flow cycle at supersonic velocities to a lower specific thrust separated flow turbofan system at subsonic velocities with a high degree of flow variability in each mode of operation.

  15. Relationship between cycling mechanics and core stability.

    PubMed

    Abt, John P; Smoliga, James M; Brick, Matthew J; Jolly, John T; Lephart, Scott M; Fu, Freddie H

    2007-11-01

    Core stability has received considerable attention with regards to functional training in sports. Core stability provides the foundation from which power is generated in cycling. No research has described the relationship between core stability and cycling mechanics of the lower extremity. The purpose of this study was to determine the relationship between cycling mechanics and core stability. Hip, knee, and ankle joint kinematic and pedal force data were collected on 15 competitive cyclists while cycling untethered on a high-speed treadmill. The exhaustive cycling protocol consisted of cycling at 25.8 km x h(-1) while the grade was increased 1% every 3 minutes. A core fatigue workout was performed before the second treadmill test. Total frontal plane knee motion (test 1: 15.1 +/- 6.0 degrees ; test 2: 23.3 +/- 12.5 degrees), sagittal plane knee motion (test 1: 69.9 +/- 4.9 degrees ; test 2: 79.3 +/- 10.1 degrees), and sagittal plane ankle motion (test 1: 29.0 +/- 8.5 degrees ; test 2: 43.0 +/- 22.9 degrees) increased after the core fatigue protocol. No significant differences were demonstrated for pedaling forces. Core fatigue resulted in altered cycling mechanics that might increase the risk of injury because the knee joint is potentially exposed to greater stress. Improved core stability and endurance could promote greater alignment of the lower extremity when riding for extended durations as the core is more resistant to fatigue. PMID:18076271

  16. Analysis of an open cycle gas core nuclear propulsion system using MHD driven vortices for fuel containment

    NASA Astrophysics Data System (ADS)

    Sedwick, Raymond John

    1998-12-01

    A novel method for containing gaseous uranium vapor in an open cycle nuclear space propulsion system is developed. In an attempt to increase the operating temperature of the nuclear reactor beyond the melting point of solid fuel rods (thus increasing specific impulse), the fuel is instead suspended as a vapor in the propellant using the pressure forces developed in a confined vortex flow. The introduction of the fuel as uranium hexafluoride is found to be effective in maintaining its vapor phase in the feed passages from the tank, but not in the main vortex. A mechanism by which the resulting condensation of the uranium may be tolerated is identified, and the electro- optical properties of the resulting mixture are investigated. Containment is modeled using a 1D- axisymmetric geometry, and radiative heat transfer is found to restrict the maximum specific impulse of the system to 1500 seconds using pumping pressures of 500 atm. The specific impulse is related to this pressure as pm1/4, allowing only marginal increases in Isp at increased pressure levels. Additional 2D- axisymmetric issues, such as non-uniform current distribution and bypass flows through the boundary layers, are investigated, with possible methods of solution cited. A two-group, two-region reactor analysis is performed, estimating the mass of the reactor to be about 10 metric tonnes, and establishing the thrust to weight ratio achievable by the system at about 50. To reduce the mass of the power system, a scheme for using cross-flow heat exchange with the propellant flow to minimize (and possibly eliminate) the need for radiators to reject waste heat is presented. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  17. H gas turbine combined cycle

    SciTech Connect

    Corman, J.

    1995-10-01

    A major step has been taken in the development of the Next Power Generation System - {open_quotes}H{close_quotes} Technology Combined Cycle. This new gas turbine combined-cycle system increases thermal performance to the 60% level by increasing gas turbine operating temperature to 1430 C (2600 F) at a pressure ratio of 23 to 1. Although this represents a significant increase in operating temperature for the gas turbine, the potential for single digit NOx levels (based upon 15% O{sub 2}, in the exhaust) has been retained. The combined effect of performance increase and environmental control is achieved by an innovative closed loop steam cooling system which tightly integrates the gas turbine and steam turbine cycles. The {open_quotes}H{close_quotes} Gas Turbine Combined Cycle System meets the goals and objectives of the DOE Advanced Turbine System Program. The development and demonstration of this new system is being carried out as part of the Industrial/Government cooperative agreement under the ATS Program. This program will achieve first commercial operation of this new system before the end of the century.

  18. Nuclear gas core propulsion research program

    NASA Technical Reports Server (NTRS)

    Diaz, Nils J.; Dugan, Edward T.; Anghaie, Samim

    1993-01-01

    Viewgraphs on the nuclear gas core propulsion research program are presented. The objectives of this research are to develop models and experiments, systems, and fuel elements for advanced nuclear thermal propulsion rockets. The fuel elements under investigation are suitable for gas/vapor and multiphase fuel reactors. Topics covered include advanced nuclear propulsion studies, nuclear vapor thermal rocket (NVTR) studies, and ultrahigh temperature nuclear fuels and materials studies.

  19. Life-cycle analysis of shale gas and natural gas.

    SciTech Connect

    Clark, C.E.; Han, J.; Burnham, A.; Dunn, J.B.; Wang, M.

    2012-01-27

    The technologies and practices that have enabled the recent boom in shale gas production have also brought attention to the environmental impacts of its use. Using the current state of knowledge of the recovery, processing, and distribution of shale gas and conventional natural gas, we have estimated up-to-date, life-cycle greenhouse gas emissions. In addition, we have developed distribution functions for key parameters in each pathway to examine uncertainty and identify data gaps - such as methane emissions from shale gas well completions and conventional natural gas liquid unloadings - that need to be addressed further. Our base case results show that shale gas life-cycle emissions are 6% lower than those of conventional natural gas. However, the range in values for shale and conventional gas overlap, so there is a statistical uncertainty regarding whether shale gas emissions are indeed lower than conventional gas emissions. This life-cycle analysis provides insight into the critical stages in the natural gas industry where emissions occur and where opportunities exist to reduce the greenhouse gas footprint of natural gas.

  20. Gas core reactors for coal gasification

    NASA Technical Reports Server (NTRS)

    Weinstein, H.

    1976-01-01

    The concept of using a gas core reactor to produce hydrogen directly from coal and water is presented. It is shown that the chemical equilibrium of the process is strongly in favor of the production of H2 and CO in the reactor cavity, indicating a 98% conversion of water and coal at only 1500 K. At lower temperatures in the moderator-reflector cooling channels the equilibrium strongly favors the conversion of CO and additional H2O to CO2 and H2. Furthermore, it is shown the H2 obtained per pound of carbon has 23% greater heating value than the carbon so that some nuclear energy is also fixed. Finally, a gas core reactor plant floating in the ocean is conceptualized which produces H2, fresh water and sea salts from coal.

  1. Gas Core Nuclear Rocket Feasibility Project

    NASA Technical Reports Server (NTRS)

    Howe, S. D.; DeVolder, B.; Thode, L.; Zerkle, D.

    1997-01-01

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas core nuclear rocket (GCNR) has the potential to be such a system. The gas core concept relies on the use of fluid dynamic forces to create and maintain a vortex. The vortex is composed of a fissile material which will achieve criticality and produce high power levels. By radiatively coupling to the surrounding fluids, extremely high temperatures in the propellant and, thus, high specific impulses can be generated. The ship velocities enabled by such performance may allow a 9 month round trip, manned Mars mission to be considered. Alternatively, one might consider slightly longer missions in ships that are heavily shielded against the intense Galactic Cosmic Ray flux to further reduce the radiation dose to the crew. The current status of the research program at the Los Alamos National Laboratory into the gas core nuclear rocket feasibility will be discussed.

  2. Gas core nuclear rocket feasibility project

    SciTech Connect

    Howe, S.D.; DeVolder, B.; Thode, L.; Zerkle, D.

    1997-09-01

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas core nuclear rocket (GCNR) has the potential to be such a system. The gas core concept relies on the use of fluid dynamic forces to create and maintain a vortex. The vortex is composed of a fissile material which will achieve criticality and produce high power levels. By radiatively coupling to the surrounding fluids, extremely high temperatures in the propellant and, thus, high specific impulses can be generated. The ship velocities enabled by such performance may allow a 9 month round trip, manned Mars mission to be considered. Alternatively, one might consider slightly longer missions in ships that are heavily shielded against the intense Galactic Cosmic Ray flux to further reduce the radiation dose to the crew. The current status of the research program at the Los Alamos National Laboratory into the gas core nuclear rocket feasibility will be discussed.

  3. The evaporative gas turbine (EGT) cycle

    SciTech Connect

    Horlock, J.H.

    1998-04-01

    Humidification of the flow through a gas turbine has been proposed in a variety of forms. The STIG plant involves the generation of steam by the gas turbine exhaust in a heat recovery steam generator (HRSG), and its injection into or downstream of the combustion chamber. This increases the mass flow through the turbine and the power output from the plant, with a small increase in efficiency. In the evaporative gas turbine (or EGT) cycle, water is injected in the compressor discharge in a regenerative gas turbine cycle (a so-called CBTX plant--compressor [C], burner [B], turbine [T], heat exchanger [X]); the air is evaporatively cooled before it enters the heat exchanger. While the addition of water increases the turbine mass flow and power output, there is also apparent benefit in reducing the temperature drop in the exhaust stack. In one variation of the basic EGT cycle, water is also added downstream of the evaporative aftercooler, even continuously in the heat exchanger. There are several other variations on the basic cycle (e.g., the cascaded humidified advanced turbine [CHAT]). The present paper analyzes the performance of the EGT cycle. The basic thermodynamics are first discussed, and related to the cycle analysis of a dry regenerative gas turbine plant. Subsequently some detailed calculations of EGT cycles are presented. The main purpose of the work is to seek the optimum pressure ratio in the EGT cycle for given constraints (e.g., fixed maximum to minimum temperature). It is argued that this optimum has a relatively low value.

  4. Gas-core reactor power transient analysis.

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.

    1972-01-01

    The nuclear fuel in the gas-core reactor concept is a ball of uranium plasma radiating thermal photons. The photons are met by an inflowing hydrogen stream, which is seeded with submicron size, depleted uranium particles. A 'wall-burnout' condition exists if the thermal photons can reach the cavity liner because of insufficient absorption by the hydrogen. An analysis was conducted in order to determine the time for which the maximum steady state reactor power could be exceeded without damage to the cavity liner due to burnout. Wall-burnout time as a function of the power increase above the initial steady state condition is shown in a graph.

  5. VERA Core Simulator Methodology for PWR Cycle Depletion

    SciTech Connect

    Kochunas, Brendan; Collins, Benjamin S; Jabaay, Daniel; Kim, Kang Seog; Graham, Aaron; Stimpson, Shane; Wieselquist, William A; Clarno, Kevin T; Palmtag, Scott; Downar, Thomas; Gehin, Jess C

    2015-01-01

    This paper describes the methodology developed and implemented in MPACT for performing high-fidelity pressurized water reactor (PWR) multi-cycle core physics calculations. MPACT is being developed primarily for application within the Consortium for the Advanced Simulation of Light Water Reactors (CASL) as one of the main components of the VERA Core Simulator, the others being COBRA-TF and ORIGEN. The methods summarized in this paper include a methodology for performing resonance self-shielding and computing macroscopic cross sections, 2-D/1-D transport, nuclide depletion, thermal-hydraulic feedback, and other supporting methods. These methods represent a minimal set needed to simulate high-fidelity models of a realistic nuclear reactor. Results demonstrating this are presented from the simulation of a realistic model of the first cycle of Watts Bar Unit 1. The simulation, which approximates the cycle operation, is observed to be within 50 ppm boron (ppmB) reactivity for all simulated points in the cycle and approximately 15 ppmB for a consistent statepoint. The verification and validation of the PWR cycle depletion capability in MPACT is the focus of two companion papers.

  6. Growth of Gas-giant Cores in Protoplanetary Discs

    NASA Astrophysics Data System (ADS)

    Lambrechts, Michiel

    2011-09-01

    The core accretion scenario is the most successful theoretical model for gas-giant formation. However, the initial growth of the core depends on arbitrary assumptions on planetesimal sizes. Growing the solid core before gas dissipation is problematic due to the long time-scale for run-away accretion, especially in the outer distant regions of a protoplanetary disc. We have studied the dynamics of gas-coupled cm-sized pebbles, gravitationally interacting with larger than km-sized cores. The Pencil Code is used to correctly model the gas drag hydrodynamics. Interestingly, the presence of pebbles in the gaseous disc influences both the dynamics (through dynamical friction) and growth rate of the gas-giant core. Under favourable conditions, i.e. unity mid-plane dust-to-gas ratio and particle growth to mm and cm sizes, pebble accretion turns out to be significantly faster than run-away accretion of planetesimals.

  7. Gas Hydrate Research Coring and Downhole Logging Operational Protocol

    NASA Astrophysics Data System (ADS)

    Collett, T. S.; Riedel, M.; Malone, M.

    2006-12-01

    Recent gas hydrate deep coring and downhole logging projects, including ODP Leg 204, IODP Expedition 311, and the India NGHP-01 effort have contributed greatly to our understanding of the geologic controls on the occurrence of gas hydrate. These projects have also built on the relatively sparse history of gas hydrate drilling experience to collectively develop a unique operational protocol to examine and sample gas hydrate in nature. The ideal gas hydrate research drill site in recent history, consists of at least three drill holes, with the first hole dedicated to LWD/MWD downhole logging in order to identify intervals to be pressurized cored and to collect critical petrophysical data. The second hole is usually dedicated for continuous coring operations. The third hole is used for special downhole tool measurements such as pressure coring and wire line logging. There is a strong scientific need to obtain LWD/MWD data prior to coring. The coring operations are complemented by frequent deployment of the PCS/HYACINTH pressure core systems. It is essential to know what the gas hydrate concentrations and vertical distribution are before deploying the available pressure core systems in order to choose the optimum depths for pressure coring operations. The coring operations are also complemented by frequent sampling for interstitial water, headspace gas, and microbiological analyses. Although those samples will be taken at relatively regular depths, the sampling frequency can be adjusted if gas hydrate concentrations and distribution can be forward predicted through the analysis of the LWD/MWD pre-core logging surveys. After completing the LWD/MWD logging program, usually as a dedicated drilling leg, field efforts will switch to conventional and pressure-controlled coring operations at each of the sites drilled during the LWD/MWD campaign. The standard continuous core hole will usually include APC coring to an expected refusal depth of ~100 mbsf; each hole is usually

  8. Gas-core reactor power transient analysis

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.

    1972-01-01

    The gas core reactor is a proposed device which features high temperatures. It has applications in high specific impulse space missions, and possibly in low thermal pollution MHD power plants. The nuclear fuel is a ball of uranium plasma radiating thermal photons as opposed to gamma rays. This thermal energy is picked up before it reaches the solid cavity liner by an inflowing seeded propellant stream and convected out through a rocket nozzle. A wall-burnout condition will exist if there is not enough flow of propellant to convect the energy back into the cavity. A reactor must therefore operate with a certain amount of excess propellant flow. Due to the thermal inertia of the flowing propellant, the reactor can undergo power transients in excess of the steady-state wall burnout power for short periods of time. The objective of this study was to determine how long the wall burnout power could be exceeded without burning out the cavity liner. The model used in the heat-transfer calculation was one-dimensional, and thermal radiation was assumed to be a diffusion process.

  9. Indirect-fired gas turbine dual fuel cell power cycle

    SciTech Connect

    Micheli, P.L.; Williams, M.C.; Sudhoff, F.A.

    1998-04-01

    The present invention relates generally to an integrated fuel cell power plant, and more specifically to a combination of cycles wherein a first fuel cell cycle tops an indirect-fired gas turbine cycle and a second fuel cell cycle bottoms the gas turbine cycle so that the cycles are thermally integrated in a tandem operating arrangement. The United States Government has rights in this invention pursuant to the employer-employee relationship between the United States Department of Energy and the inventors.

  10. Core-in-shell sorbent for hot coal gas desulfurization

    DOEpatents

    Wheelock, Thomas D.; Akiti, Jr., Tetteh T.

    2004-02-10

    A core-in-shell sorbent is described herein. The core is reactive to the compounds of interest, and is preferably calcium-based, such as limestone for hot gas desulfurization. The shell is a porous protective layer, preferably inert, which allows the reactive core to remove the desired compounds while maintaining the desired physical characteristics to withstand the conditions of use.

  11. Life-cycle greenhouse gas emissions of shale gas, natural gas, coal, and petroleum.

    PubMed

    Burnham, Andrew; Han, Jeongwoo; Clark, Corrie E; Wang, Michael; Dunn, Jennifer B; Palou-Rivera, Ignasi

    2012-01-17

    The technologies and practices that have enabled the recent boom in shale gas production have also brought attention to the environmental impacts of its use. It has been debated whether the fugitive methane emissions during natural gas production and transmission outweigh the lower carbon dioxide emissions during combustion when compared to coal and petroleum. Using the current state of knowledge of methane emissions from shale gas, conventional natural gas, coal, and petroleum, we estimated up-to-date life-cycle greenhouse gas emissions. In addition, we developed distribution functions for key parameters in each pathway to examine uncertainty and identify data gaps such as methane emissions from shale gas well completions and conventional natural gas liquid unloadings that need to be further addressed. Our base case results show that shale gas life-cycle emissions are 6% lower than conventional natural gas, 23% lower than gasoline, and 33% lower than coal. However, the range in values for shale and conventional gas overlap, so there is a statistical uncertainty whether shale gas emissions are indeed lower than conventional gas. Moreover, this life-cycle analysis, among other work in this area, provides insight on critical stages that the natural gas industry and government agencies can work together on to reduce the greenhouse gas footprint of natural gas. PMID:22107036

  12. Novel functions of core cell cycle regulators in neuronal migration.

    PubMed

    Godin, Juliette D; Nguyen, Laurent

    2014-01-01

    The cerebral cortex is one of the most intricate regions of the brain, which required elaborated cell migration patterns for its development. Experimental observations show that projection neurons migrate radially within the cortical wall, whereas interneurons migrate along multiple tangential paths to reach the developing cortex. Tight regulation of the cell migration processes ensures proper positioning and functional integration of neurons to specific cerebral cortical circuits. Disruption of neuronal migration often lead to cortical dysfunction and/or malformation associated with neurological disorders. Unveiling the molecular control of neuronal migration is thus fundamental to understand the physiological or pathological development of the cerebral cortex. Generation of functional cortical neurons is a complex and stratified process that relies on decision of neural progenitors to leave the cell cycle and generate neurons that migrate and differentiate to reach their final position in the cortical wall. Although accumulating work shed some light on the molecular control of neuronal migration, we currently do not have a comprehensive understanding of how cell cycle exit and migration/differentiation are coordinated at the molecular level. The current chapter tends to lift the veil on this issue by discussing how core cell cycle regulators, and in particular p27(Kip1) acts as a multifunctional protein to control critical steps of neuronal migration through activities that go far beyond cell cycle regulation. PMID:24243100

  13. Feasibility study of full-reactor gas core demonstration test

    NASA Technical Reports Server (NTRS)

    Kunze, J. F.; Lofthouse, J. H.; Shaffer, C. J.; Macbeth, P. J.

    1973-01-01

    Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved.

  14. Integrated vacuum absorption steam cycle gas separation

    SciTech Connect

    Chen, Shiaguo; Lu, Yonggi; Rostam-Abadi, Massoud

    2011-11-22

    Methods and systems for separating a targeted gas from a gas stream emitted from a power plant. The gas stream is brought into contact with an absorption solution to preferentially absorb the targeted gas to be separated from the gas stream so that an absorbed gas is present within the absorption solution. This provides a gas-rich solution, which is introduced into a stripper. Low pressure exhaust steam from a low pressure steam turbine of the power plant is injected into the stripper with the gas-rich solution. The absorbed gas from the gas-rich solution is stripped in the stripper using the injected low pressure steam to provide a gas stream containing the targeted gas. The stripper is at or near vacuum. Water vapor in a gas stream from the stripper is condensed in a condenser operating at a pressure lower than the stripper to concentrate the targeted gas. Condensed water is separated from the concentrated targeted gas.

  15. A Burst Mode, Ultrahigh Temperature UF4 Vapor Core Reactor Rankine Cycle Space Power System Concept

    NASA Technical Reports Server (NTRS)

    Dugan, E. T.; Kahook, S. D.; Diaz, N. J.

    1996-01-01

    Static and dynamic neutronic analyses have been performed on an innovative burst mode (100's of MW output for a few thousand seconds) Ulvahigh Temperature Vapor Core Reactor (UTVR) space nuclear power system. The NVTR employs multiple, neutronically-coupled fissioning cores and operates on a direct, closed Rankine cycle using a disk Magnetohydrodynamic (MHD) generater for energy conversion. The UTVR includes two types of fissioning core regions: (1) the central Ultrahigh Temperature Vapor Core (UTVC) which contains a vapor mixture of highly enriched UF4 fuel and a metal fluoride working fluid and (2) the UF4 boiler column cores located in the BeO moderator/reflector region. The gaseous nature of the fuel the fact that the fuel is circulating, the multiple coupled fissioning cores, and the use of a two phase fissioning fuel lead to unique static and dynamic neutronic characteristics. Static neutronic analysis was conducted using two-dimensional S sub n, transport theory calculations and three-dimensional Monte Carlo transport theory calculations. Circulating-fuel, coupled-core point reactor kinetics equations were used for analyzing the dynamic behavior of the UTVR. In addition to including reactivity feedback phenomena associated with the individual fissioning cores, the effects of core-to-core neutronic and mass flow coupling between the UTVC and the surrounding boiler cores were also included in the dynamic model The dynamic analysis of the UTVR reveals the existence of some very effectlve inherent reactivity feedback effects that are capable of quickly stabilizing this system, within a few seconds, even when large positive reactivity insertions are imposed. If the UTVC vapor fuel density feedback is suppressed, the UTVR is still inherently stable because of the boiler core liquid-fuel volume feedback; in contrast, suppression of the vapor fuel density feedback in 'conventional" gas core cavity reactors causes them to become inherently unstable. Due to the

  16. Numerical evaluation of gas core length in free surface vortices

    NASA Astrophysics Data System (ADS)

    Cristofano, L.; Nobili, M.; Caruso, G.

    2014-11-01

    The formation and evolution of free surface vortices represent an important topic in many hydraulic intakes, since strong whirlpools introduce swirl flow at the intake, and could cause entrainment of floating matters and gas. In particular, gas entrainment phenomena are an important safety issue for Sodium cooled Fast Reactors, because the introduction of gas bubbles within the core causes dangerous reactivity fluctuation. In this paper, a numerical evaluation of the gas core length in free surface vortices is presented, according to two different approaches. In the first one, a prediction method, developed by the Japanese researcher Sakai and his team, has been applied. This method is based on the Burgers vortex model, and it is able to estimate the gas core length of a free surface vortex starting from two parameters calculated with single-phase CFD simulations. The two parameters are the circulation and the downward velocity gradient. The other approach consists in performing a two-phase CFD simulation of a free surface vortex, in order to numerically reproduce the gas- liquid interface deformation. Mapped convergent mesh is used to reduce numerical error and a VOF (Volume Of Fluid) method was selected to track the gas-liquid interface. Two different turbulence models have been tested and analyzed. Experimental measurements of free surface vortices gas core length have been executed, using optical methods, and numerical results have been compared with experimental measurements. The computational domain and the boundary conditions of the CFD simulations were set consistently with the experimental test conditions.

  17. Life cycle greenhouse gas emissions from bioenergy crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Life cycle greenhouse gas emissions from bioenergy crops Bioenergy cropping systems could help offset greenhouse gas emissions from energy use, but quantifying that offset is complex. We conducted a life cycle assessment of a range of bioenergy cropping systems to determine the impact on net greenho...

  18. Comparison of the filamentation and the hollow-core fibercharacteristics for pulse compression into the few-cycle regime

    SciTech Connect

    Gallmann, L.; Pfeifer, T.; Nagel, P.M.; Abel, M.J.; Neumark,D.M.; Leone, S.R.

    2006-10-23

    The gas-filled hollow-core fiber compression and the opticalfilamentation technique are compared experimentally in a parameter regimesuitable for intense few-cycle pulse generation. In particular, pointingstability, spectral properties, and spatial chirp are investigated. It isfound that in the case of filamentation, the critical parameter forpointing stability is gas pressure inside the generation cell whereas forthe hollow-core fiber it is alignment that plays this role. Thehollow-core fiber technique yields spectra that are better suited forchirped-mirror pulse compression whereas filamentation offers higherthroughput and prospects for easy-to-implement self-compression. Wepresent spectral phase interferometry for direct electric-fieldreconstruction (SPIDER) measurements that directly show the transition inthe spectral phase of the output continua into the self-compressionregime as the gas pressure is increased.

  19. Probing the Physics of Gas in Cool Core Clusters: Virgo

    NASA Astrophysics Data System (ADS)

    Sparks, William

    2010-09-01

    We recently detected high temperature gas at 10^5K associated with the low excitation 10^4K line emission filaments of M87. This is a profoundly important observation bearing on the physics of transport processes in cool core clusters. We propose to delve deeper into the physics of cool core clusters. We propose to use ACS to compare the spatial extent and morphology of the low and high temperature gas, to use the timely presence of COS to obtain a sensitive FUV spectrum of the hot gas, and, by introducing the notion of emission line polarimetry, seek a a potentially revolutionary new plasma diagnostic. The spatial distributions will reveal whether the hotter material is more spatially extended than the cooler; the FUV spectrum will permit derivation of the emission measure {essentially amount of gas} at each temperature between the 10^4K Halpha filaments and coronal gas at 10^7K. Together these strongly constrain plausible transport processes relating the hot and cool gas phases in this cool core cluster region, and hence the dominant physical processes at work. A novel ingredient is to obtain the optical images in polarimetric mode to probe emission line polarization levels, a diagnostic used in Solar physics to determine the relevance of collisional excitation processes such as electron impact polarization in thermal conduction or shocks. With this suite of straightforward, uniquely HST observations we may dramatically change the landscape of our understanding of the physics of cool core clusters

  20. Portable tester for determining gas content within a core sample

    DOEpatents

    Garcia, F. Jr.; Schatzel, S.J.

    1998-04-21

    A portable tester is provided for reading and displaying the pressure of a gas released from a rock core sample stored within a sealed container and for taking a sample of the released pressurized gas for chemical analysis thereof for subsequent use in a modified direct method test which determines the volume of gas and specific type of gas contained within the core sample. The portable tester includes a pair of low and high range electrical pressure transducers for detecting a gas pressure; a pair of low and high range display units for displaying the pressure of the detected gas; a selector valve connected to the low and high range pressure transducers and a selector knob for selecting gas flow to one of the flow paths; control valve having an inlet connection to the sealed container; and outlets connected to: a sample gas canister, a second outlet port connected to the selector valve means for reading the pressure of the gas from the sealed container to either the low range or high range pressure transducers, and a connection for venting gas contained within the sealed container to the atmosphere. A battery is electrically connected to and supplies the power for operating the unit. The pressure transducers, display units, selector and control valve means and the battery is mounted to and housed within a protective casing for portable transport and use. 5 figs.

  1. Portable tester for determining gas content within a core sample

    DOEpatents

    Garcia, Jr., Fred; Schatzel, Steven J.

    1998-01-01

    A portable tester is provided for reading and displaying the pressure of a gas released from a rock core sample stored within a sealed container and for taking a sample of the released pressurized gas for chemical analysis thereof for subsequent use in a modified direct method test which determines the volume of gas and specific type of gas contained within the core sample. The portable tester includes a pair of low and high range electrical pressure transducers for detecting a gas pressure; a pair of low and high range display units for displaying the pressure of the detected gas- a selector valve connected to the low and high range pressure transducers, a selector knob for selecting gas flow to one of the flow paths; control valve having an inlet connection to the sealed container, and outlets connected to: a sample gas canister, a second outlet port connected to the selector valve means for reading the pressure of the gas from the sealed container to either the low range or high range pressure transducers, and a connection for venting gas contained within the sealed container to the atmosphere. A battery is electrically connected to and supplies the power for operating the unit. The pressure transducers, display units, selector and control valve means and the battery is mounted to and housed within a protective casing for portable transport and use.

  2. Brayton cycle solarized advanced gas turbine

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Described is the development of a Brayton Engine/Generator Set for solar thermal to electrical power conversion, authorized under DOE/NASA Contract DEN3-181. The objective was to design, fabricate, assemble, and test a small, hybrid, 20-kW Brayton-engine-powered generator set. The latter, called a power conversion assembly (PCA), is designed to operate with solar energy obtained from a parobolic dish concentrator, 11 meters in diameter, or with fossil energy supplied by burning fuels in a combustor, or by a combination of both (hybrid model). The CPA consists of the Brayton cycle engine, a solar collector, a belt-driven 20-kW generator, and the necessary control systems for automatic operation in solar-only, fuel-only, and hybrid modes to supply electrical power to a utility grid. The original configuration of the generator set used the GTEC Model GTP36-51 gas turbine engine for the PCA prime mover. However, subsequent development of the GTEC Model AGT101 led to its selection as the powersource for the PCA. Performance characteristics of the latter, thermally coupled to a solar collector for operation in the solar mode, are presented. The PCA was successfully demonstrated in the fuel-only mode at the GTEC Phoenix, Arizona, facilities prior to its shipment to Sandia National Laboratory in Albuquerque, New Mexico, for installation and testing on a test bed concentractor (parabolic dish). Considerations relative to Brayton-engine development using the all-ceramic AGT101 when it becomes available, which would satisfy the DOE heat engine efficiency goal of 35 to 41 percent, are also discussed in the report.

  3. Thermodynamic design of natural gas liquefaction cycles for offshore application

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Lim, Hye Su; Choe, Kun Hyung

    2014-09-01

    A thermodynamic study is carried out for natural gas liquefaction cycles applicable to offshore floating plants, as partial efforts of an ongoing governmental project in Korea. For offshore liquefaction, the most suitable cycle may be different from the on-land LNG processes under operation, because compactness and simple operation are important as well as thermodynamic efficiency. As a turbine-based cycle, closed Claude cycle is proposed to use NG (natural gas) itself as refrigerant. The optimal condition for NG Claude cycle is determined with a process simulator (Aspen HYSYS), and the results are compared with fully-developed C3-MR (propane pre-cooled mixed refrigerant) JT cycles and various N2 (nitrogen) Brayton cycles in terms of efficiency and compactness. The newly proposed NG Claude cycle could be a good candidate for offshore LNG processes.

  4. Antiproton Powered Gas Core Fission Rocket

    NASA Astrophysics Data System (ADS)

    Kammash, T.

    Extensive research in recent years has demonstrated that “at rest” annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

  5. Antiproton Powered Gas Core Fission Rocket

    NASA Astrophysics Data System (ADS)

    Kammash, Terry

    2005-02-01

    Extensive research in recent years has demonstrated that "at rest" annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas — inserted into the chamber just prior to the release of the antiproton — to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

  6. Antiproton Powered Gas Core Fission Rocket

    SciTech Connect

    Kammash, Terry

    2005-02-06

    Extensive research in recent years has demonstrated that 'at rest' annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

  7. Single pressure steam bottoming cycle for gas turbines combined cycle

    SciTech Connect

    Zervos, N.

    1990-01-30

    This patent describes a process for recapturing waste heat from the exhaust of a gas turbine to drive a high pressure-high temperature steam turbine and a low pressure steam turbine. It comprises: delivering the exhaust of the gas turbine to the hot side of an economizer-reheater apparatus; delivering a heated stream of feedwater and recycled condensate through the cold side of the economizer-reheater apparatus in an indirect heat exchange relationship with the gas turbine exhaust on the hot side of the economizer-reheater apparatus to elevate the temperature below the pinch point of the boiler; delivering the discharge from the high pressure-high temperature steam turbine through the economizer-reheater apparatus in an indirect heat exchange relationship with the gas turbine exhaust on the hot side of the economizer-reheater apparatus; driving the high pressure-high temperature steam turbine with the discharge stream of feedwater and recycled condensate which is heated to a temperature below the pinch point of the boiler by the economizer-reheater apparatus; and driving the low pressure steam turbine with the discharged stream of the high pressure-high temperature steam turbine reheated below the pinch point of the boiler by the economizer-reheater apparatus.

  8. Students' Understanding of Analogy after a Core (Chemical Observations, Representations, Experimentation) Learning Cycle, General Chemistry Experiment

    ERIC Educational Resources Information Center

    Avargil, Shirly; Bruce, Mitchell R. M.; Amar, Franc¸ois G.; Bruce, Alice E.

    2015-01-01

    Students' understanding about analogy was investigated after a CORE learning cycle general chemistry experiment. CORE (Chemical Observations, Representations, Experimentation) is a new three-phase learning cycle that involves (phase 1) guiding students through chemical observations while they consider a series of open-ended questions, (phase 2)…

  9. Open cycle gas fired MHD power plants

    SciTech Connect

    Medin, S.A. ); Negrini, F. )

    1991-01-01

    In this paper, the main objectives for the present development of gas fired MHD power generation are considered. The state of the world-wide natural gas consumption and its utilization for electricity production is analyzed. The experimental efforts in gas-fired MHD studies are briefly described. The essential features of the two major world gas-fired MHD project - the Ryazan MHDES-580 (U-500) power plant and the Italian 230 MWt retrofit are presented. New suggestions for improving the efficiency of MHD systems and the theoretical and experimental aspects of MHD development are discussed.

  10. Indirect-fired gas turbine dual fuel cell power cycle

    DOEpatents

    Micheli, Paul L.; Williams, Mark C.; Sudhoff, Frederick A.

    1996-01-01

    A fuel cell and gas turbine combined cycle system which includes dual fuel cell cycles combined with a gas turbine cycle wherein a solid oxide fuel cell cycle operated at a pressure of between 6 to 15 atms tops the turbine cycle and is used to produce CO.sub.2 for a molten carbonate fuel cell cycle which bottoms the turbine and is operated at essentially atmospheric pressure. A high pressure combustor is used to combust the excess fuel from the topping fuel cell cycle to further heat the pressurized gas driving the turbine. A low pressure combustor is used to combust the excess fuel from the bottoming fuel cell to reheat the gas stream passing out of the turbine which is used to preheat the pressurized air stream entering the topping fuel cell before passing into the bottoming fuel cell cathode. The CO.sub.2 generated in the solid oxide fuel cell cycle cascades through the system to the molten carbonate fuel cell cycle cathode.

  11. Plant System Design of Supercritical CO{sub 2} Direct Cycle Gas Turbine Fast Reactor

    SciTech Connect

    Katsuhiro, Tozawa; Nobumasa, Tsuji; Yasushi, Muto; Yasuyoshi, Kato

    2006-07-01

    The conceptual plant design and preliminary safety analysis of SCDFR, Supercritical CO{sub 2} Direct Cycle Gas Turbine Fast Reactor, were performed. Plant thermal power is 600 MW. Core outlet/inlet pressure and temperature are 12.5/12.8 MPa and 527/388 deg C respectively. The core height and equivalent diameter are about 1.2 m and about 3.146 m respectively. The core can be burning for 10 years without refueling by adding 6.5% content of {sup 237}Np into the fuel as a burnable poison. Reactor pressure vessel height and inner diameter are about 19.3 m and about 6.55 m respectively. Steel containment vessel contains the reactor system and the gas turbine system. Preliminary analysis of core temperature behavior during the depressurization accident in SCDFR was performed. In the result of the analysis, core temperature is limited under 900 deg C, assumed limit temperature of the fuel clad, at the condition of minimum gas circulation flow rate of 2.0 m{sup 3}/s. On the other hand, gas circulator designed flow rate of the auxiliary core cooling system is over 11.6 m{sup 3}/s. These show that the integrity of the fuel clad during depressurization accident is maintained. We conclude that the plant concept of SCDFR is developed and the plant safety under depressurization accident conditions is confirmed by preliminary analysis. (authors)

  12. Supercritical CO2 direct cycle Gas Fast Reactor (SC-GFR) concept.

    SciTech Connect

    Wright, Steven Alan; Parma, Edward J., Jr.; Suo-Anttila, Ahti Jorma; Al Rashdan, Ahmad; Tsvetkov, Pavel Valeryevich; Vernon, Milton E.; Fleming, Darryn D.; Rochau, Gary Eugene

    2011-05-01

    This report describes the supercritical carbon dioxide (S-CO{sub 2}) direct cycle gas fast reactor (SC-GFR) concept. The SC-GFR reactor concept was developed to determine the feasibility of a right size reactor (RSR) type concept using S-CO{sub 2} as the working fluid in a direct cycle fast reactor. Scoping analyses were performed for a 200 to 400 MWth reactor and an S-CO{sub 2} Brayton cycle. Although a significant amount of work is still required, this type of reactor concept maintains some potentially significant advantages over ideal gas-cooled systems and liquid metal-cooled systems. The analyses presented in this report show that a relatively small long-life reactor core could be developed that maintains decay heat removal by natural circulation. The concept is based largely on the Advanced Gas Reactor (AGR) commercial power plants operated in the United Kingdom and other GFR concepts.

  13. Power Gas and Combined Cycles: Clean Power From Fossil Fuels

    ERIC Educational Resources Information Center

    Metz, William D.

    1973-01-01

    The combined-cycle system is currently regarded as a useful procedure for producing electricity. This system can burn natural gas and oil distillates in addition to coal. In the future when natural gas stocks will be low, coal may become an important fuel for such systems. Considerable effort must be made for research on coal gasification and…

  14. Gas core reactor concepts and technology - Issues and baseline strategy

    NASA Technical Reports Server (NTRS)

    Diaz, Nils J.; Dugan, Edward T.; Kahook, Samer; Maya, Isaac

    1991-01-01

    Results of a research program including phenomenological studies, conceptual design, and systems analysis of a series of gaseous/vapor fissile fuel driven engines for space power platforms and for thermal and electric propulsion are reviewed. It is noted that gas and vapor phase reactors provide the path for minimum mass in orbit and trip times, with a specific impulse from 1020 sec at the lowest technololgical risk to 5200 sec at the highest technological risk. The discussion covers various configurations of gas core reactors and critical technologies and the nuclear vapor thermal rocket engine.

  15. Hollow-core fiber Fabry-Perot photothermal gas sensor.

    PubMed

    Yang, Fan; Tan, Yanzhen; Jin, Wei; Lin, Yuechuan; Qi, Yun; Ho, Hoi Lut

    2016-07-01

    A highly sensitive, compact, and low-cost trace gas sensor based on photothermal effect in a hollow-core fiber Fabry-Perot interferometer (FPI) is described. The Fabry-Perot sensor is fabricated by splicing a piece of hollow-core photonic bandgap fiber (HC-PBF) to single-mode fiber pigtails at both ends. The absorption of a pump beam in the hollow core results in phase modulation of probe beam, which is detected by the FPI. Experiments with a 2 cm long HC-PBF with femtosecond laser drilled side-holes demonstrated a response time of less than 19 s and noise equivalent concentration (NEC) of 440 parts-per-billion (ppb) using a 1 s lock-in time constant, and the NEC goes down to 117 ppb (2.7×10-7 in absorbance) by using 77 s averaging time. PMID:27367092

  16. Gamma heating in reflector heat shield of gas core reactor

    NASA Technical Reports Server (NTRS)

    Lofthouse, J. H.; Kunze, J. F.; Young, T. E.; Young, R. C.

    1972-01-01

    Heating rate measurements made in a mock-up of a BeO heat shield for a gas core nuclear rocket engine yields results nominally a factor of two greater than calculated by two different methods. The disparity is thought to be caused by errors in neutron capture cross sections and gamma spectra from the low cross-section elements, D, O, and Be.

  17. Gas core reactors for actinide transmutation and breeder applications

    NASA Technical Reports Server (NTRS)

    Clement, J. D.; Rust, J. H.

    1978-01-01

    This work consists of design power plant studies for four types of reactor systems: uranium plasma core breeder, uranium plasma core actinide transmuter, UF6 breeder and UF6 actinide transmuter. The plasma core systems can be coupled to MHD generators to obtain high efficiency electrical power generation. A 1074 MWt UF6 breeder reactor was designed with a breeding ratio of 1.002 to guard against diversion of fuel. Using molten salt technology and a superheated steam cycle, an efficiency of 39.2% was obtained for the plant and the U233 inventory in the core and heat exchangers was limited to 105 Kg. It was found that the UF6 reactor can produce high fluxes (10 to the 14th power n/sq cm-sec) necessary for efficient burnup of actinide. However, the buildup of fissile isotopes posed severe heat transfer problems. Therefore, the flux in the actinide region must be decreased with time. Consequently, only beginning-of-life conditions were considered for the power plant design. A 577 MWt UF6 actinide transmutation reactor power plant was designed to operate with 39.3% efficiency and 102 Kg of U233 in the core and heat exchanger for beginning-of-life conditions.

  18. Low-Temperature Multiple-Reheat Closed Gas Power Cycles for the AHTR and LSFR

    SciTech Connect

    Haihua, Zhao; Peterson, Per F.

    2006-07-01

    High Temperature Gas Cooled Reactors (HTGR) such as GT-MHR and PBMR with direct closed gas-turbine Brayton cycle can achieve efficiency between 44% to 48% with core outlet temperatures from 850 deg. C to 900 deg. C. The use of multiple reheat and inter-cooling stages can further improve thermal efficiency. Low-temperature multiple reheat cycles for the AHTR-MI and liquid-salt fast reactors (LSFR), with core outlet temperatures ranging from 620 deg. C to 750 deg. C, can reach similar efficiency as these direct-cycle HTGRs but with reduced technical risk due to lower temperatures. This paper discusses design optimization at these lower temperatures for multiple reheat closed gas cycles and vertical and horizontal arrangement options for power conversion units (PCU). Figures of merit such as specific power density, specific steel input, and specific helium inventory are estimated for different PCU arrangement configurations. With similar components parameters and reasonable arrangement, different configurations such as horizontal or vertical shaft, integrated system or distributed system, were compared. Among those configurations, integrated systems basing on the GT-MHR PCU design result in the highest specific power density and lowest specific steel input. Because the differences in these high-level performance parameters are not large enough to de-select any configurations, further detailed design and comparison must be performed to select optimal system designs. (authors)

  19. Nitrogen expander cycles for large capacity liquefaction of natural gas

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun; Choe, Kun Hyung

    2014-01-01

    Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity.

  20. Nitrogen expander cycles for large capacity liquefaction of natural gas

    SciTech Connect

    Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun; Choe, Kun Hyung

    2014-01-29

    Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity.

  1. Open-Cycle Gas Turbine/Steam Turbine Combined Cycles with synthetic fuels from coal

    NASA Technical Reports Server (NTRS)

    Shah, R. P.; Corman, J. C.

    1977-01-01

    The Open-Cycle Gas Turbine/Steam Turbine Combined Cycle can be an effective energy conversion system for converting coal to electricity. The intermediate step in this energy conversion process is to convert the coal into a fuel acceptable to a gas turbine. This can be accomplished by producing a synthetic gas or liquid, and by removing, in the fuel conversion step, the elements in the fuel that would be harmful to the environment if combusted. In this paper, two open-cycle gas turbine combined systems are evaluated: one employing an integrated low-Btu gasifier, and one utilizing a semi-clean liquid fuel. A consistent technical/economic information base is developed for these two systems, and is compared with a reference steam plant burning coal directly in a conventional furnace.

  2. Analysis of the Gas Core Actinide Transmutation Reactor (GCATR)

    NASA Technical Reports Server (NTRS)

    Clement, J. D.; Rust, J. H.

    1977-01-01

    Design power plant studies were carried out for two applications of the plasma core reactor: (1) As a breeder reactor, (2) As a reactor able to transmute actinides effectively. In addition to the above applications the reactor produced electrical power with a high efficiency. A reactor subsystem was designed for each of the two applications. For the breeder reactor, neutronics calculations were carried out for a U-233 plasma core with a molten salt breeding blanket. A reactor was designed with a low critical mass (less than a few hundred kilograms U-233) and a breeding ratio of 1.01. The plasma core actinide transmutation reactor was designed to transmute the nuclear waste from conventional LWR's. The spent fuel is reprocessed during which 100% of Np, Am, Cm, and higher actinides are separated from the other components. These actinides are then manufactured as oxides into zirconium clad fuel rods and charged as fuel assemblies in the reflector region of the plasma core actinide transmutation reactor. In the equilibrium cycle, about 7% of the actinides are directly fissioned away, while about 31% are removed by reprocessing.

  3. The combined cycle application of aeroderivative gas turbines

    SciTech Connect

    Sheard, A.G.; Raine, M.J.

    1998-07-01

    In recent years aeroderivative gas turbines have become an effective alternative to heavy industrial gas turbines. Marketing of aeroderivatives has focused on their simple cycle efficiency advantage. The use of aeroderivatives in combined cycle, however, has also been demonstrated to be competitive, with high net plant efficiency and moderate cost per installed kW. Aeroderivative gas turbines are also capable of achieving high baseload plant availabilities because of the maintenance philosophy of rapid gas turbine or module exchange on site. In this paper the rationale for choosing an aeroderivative over a conventional industrial gas turbine is discussed. Factors affecting the decision to opt for either a simple or combined cycle facility are considered. The economic case is made for combined cycle plant incorporating aeroderivatives, showing a lower total cost of ownership that the alternatives, including an assessment of the key factors necessary to make them viable. The paper continues with a description of an advanced single string power train concept. Implementation of the power train is presented, and its incorporation into an optimized 40 MW Class power station described. Reduction in cost of electricity and installed cost per kW are considered, as well as reduction in project lead time.

  4. Dynamic analysis of gas-core reactor system

    NASA Technical Reports Server (NTRS)

    Turner, K. H., Jr.

    1973-01-01

    A heat transfer analysis was incorporated into a previously developed model CODYN to obtain a model of open-cycle gaseous core reactor dynamics which can predict the heat flux at the cavity wall. The resulting model was used to study the sensitivity of the model to the value of the reactivity coefficients and to determine the system response for twenty specified perturbations. In addition, the model was used to study the effectiveness of several control systems in controlling the reactor. It was concluded that control drums located in the moderator region capable of inserting reactivity quickly provided the best control.

  5. Summary of the development of open-cycle gas turbine-steam cycles

    SciTech Connect

    Lackey, M.E.; Thompson, A.S.

    1980-09-01

    Combined-cycle plants employing gas turbine cycles superimposed on conventional steam plants are well developed. Nearly 200 units are operating in the US on clean fuels (natural gas or distillate fuel oils) and giving overall thermal efficiencies as high as 42%. Future plants will have to use coal or coal-derived fuels, and this presents problems because gas turbines are very sensitive to particulates and contaminants in the fuel such as sulfur, potassium, lead, etc. If clean liquid or high-Btu gaseous fuels are made from coal, it appears that the conversion efficiency will be no more than 67%. Thus, the overall efficiency of utilization of coal would be less than if it were burned in a conventional steam plant unless the permissible gas turbine inlet temperature can be increased to approx. 1500/sup 0/C (2732/sup 0/F). Coupling a combined-cycle power plant directly to a low-Btu coal gasifier increases the fuel conversion efficiency and permits salvaging waste heat from the gasifier for feedwater heating in the steam cycle. By using a gas turbine inlet temperature of 1315/sup 0/C (2400/sup 0/F), well above the current maximum of approx. 1040/sup 0/C (1904/sup 0/F), an overall efficiency of approx. 40% has been estimated for the integrated plant. However, as discussed in companion reports, it is doubtful that operation with gas turbine inlet temperatures above 1100/sup 0/C (2012/sup 0/F) will prove practicable in base-load plants.

  6. Carbon cycling and gas exchange in soils

    SciTech Connect

    Trumbore, S.E.

    1989-01-01

    This thesis summaries three independent projects, each of which describes a method which can be used to study the role of soils in regulating the atmospheric concentrations of CO{sub 2} and other trace gases. The first chapter uses the distribution of natural and bomb produced radiocarbon in fractionated soil organic matter to quantify the turnover of carbon in soils. A comparison of {sup 137}Cs and {sup 14}C in the modern soil profiles indicates that carbon is transported vertically in the soil as dissolved organic material. The remainder of the work reported is concerned with the use of inert trace gases to explore the physical factors which control the seasonal to diel variability in the fluxes of CO{sub 2} and other trace gases from soils. Chapter 2 introduces a method for measuring soil gas exchange rates in situ using sulfur hexafluoride as a purposeful tracer. The measurement method uses standard flux box technology, and includes simultaneous determination of the fluxes and soil atmosphere concentrations of CO{sub 2} and CH{sub 4}. In Chapter 3, the natural tracer {sup 222}Rn is used as an inert analog for exchange both in the soils and forest canopy of the Amazon rain forest.

  7. Externally fired gas turbine cycles for small scale biomass cogeneration

    SciTech Connect

    Anheden, M.; Ahlroth, M.; Martin, A.R.; Svedberg, G.

    1999-07-01

    In this conceptual study, externally fired gas turbine cycles in combination with a biomass-fueled, atmospheric circulating fluidized bed (CFB) furnace are investigated for small scale heat and power production ({approximately} 8 MW fuel input). Three cycle configurations are considered: closed cycle, with nitrogen, helium, and a helium/carbon dioxide mixture as working fluids; open cycle operating in parallel to the CFB system; and open cycle with a series connection to the CFB system. Intercooling, postcooling, and recuperation are employed with the goal of maximizing power output. Aside from a thermodynamic performance analysis, the study also includes an evaluation of the turbomachinery characteristics. Simulation results show that thermodynamic performance varies slightly between the different configurations, with electrical efficiencies approaching 38% (LHV) and power-to-heat ratios as high as 0.80. Equipment size is found to depend primarily upon the type of working fluid.

  8. Cycle 0(CY1991) NLS trade studies and analyses report. Book 1: Structures and core vehicle

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This report (SR-1: Structures, Trades, and Analysis), documents the Core Tankage Trades and analyses performed in support of the National Launch System (NLS) Cycle 0 preliminary design activities. The report covers trades that were conducted on the Vehicle Assembly, Fwd Skirt, LO2 Tank, Intertank, LH2 Tank, and Aft Skirt of the NLS Core Tankage. For each trade study, a two page executive summary and the detail trade study are provided. The trade studies contain study results, recommended changes to the Cycle 0 Baselines, and suggested follow on tasks to be performed during Cycle 1.

  9. Harmonization of Initial Estimates of Shale Gas Life Cycle Greenhouse Gas Emissions for Electric Power Generation

    NASA Astrophysics Data System (ADS)

    Heath, G.; O'Donoughue, P.; Arent, D.; Bazilian, M.

    2014-12-01

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices.

  10. Review of coaxial flow gas core nuclear rocket fluid mechanics

    NASA Technical Reports Server (NTRS)

    Weinstein, H.

    1976-01-01

    Almost all of the fluid mechanics research associated with the coaxial flow gas core reactor ended abruptly with the interruption of NASA's space nuclear program because of policy and budgetary considerations in 1973. An overview of program accomplishments is presented through a review of the experiments conducted and the analyses performed. Areas are indicated where additional research is required for a fuller understanding of cavity flow and of the factors which influence cold and hot flow containment. A bibliography is included with graphic material.

  11. Gas-Generator Augmented Expander Cycle Rocket Engine

    NASA Technical Reports Server (NTRS)

    Greene, William D. (Inventor)

    2011-01-01

    An augmented expander cycle rocket engine includes first and second turbopumps for respectively pumping fuel and oxidizer. A gas-generator receives a first portion of fuel output from the first turbopump and a first portion of oxidizer output from the second turbopump to ignite and discharge heated gas. A heat exchanger close-coupled to the gas-generator receives in a first conduit the discharged heated gas, and transfers heat to an adjacent second conduit carrying fuel exiting the cooling passages of a primary combustion chamber. Heat is transferred to the fuel passing through the cooling passages. The heated fuel enters the second conduit of the heat exchanger to absorb more heat from the first conduit, and then flows to drive a turbine of one or both of the turbopumps. The arrangement prevents the turbopumps exposure to combusted gas that could freeze in the turbomachinery and cause catastrophic failure upon attempted engine restart.

  12. Brayton Cycle for High-Temperature Gas-Cooled Reactors

    SciTech Connect

    Oh, Chang H.; Moore, Richard L.

    2005-03-15

    This paper describes research on improving the Brayton cycle efficiency for a high-temperature gas-cooled reactor (HTGR). In this study, we are investigating the efficiency of an indirect helium Brayton cycle for the power conversion side of an HTGR power plant. A reference case based on a 250-MW(thermal) pebble bed HTGR was developed using helium gas as a working fluid in both the primary and power conversion sides. The commercial computer code HYSYS was used for process optimization. A numerical model using the Visual-Basic (V-B) computer language was also developed to assist in the evaluation of the Brayton cycle efficiency. Results from both the HYSYS simulation and the V-B model were compared with Japanese calculations based on the 300-MW(electric) Gas Turbine High-Temperature Reactor (GTHTR) that was developed by the Japan Atomic Energy Research Institute. After benchmarking our models, parametric investigations were performed to see the effect of important parameters on the cycle efficiency. We also investigated single-shaft versus multiple-shaft arrangements for the turbomachinery. The results from this study are applicable to other reactor concepts such as fast gas-cooled reactors, supercritical water reactors, and others.The ultimate goal of this study is to use other fluids such as supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency over that of the helium Brayton cycle. This study is in progress, and the results will be published in a subsequent paper.

  13. Brayton Cycle for High Temperature Gas-Cooled Reactors

    SciTech Connect

    Chang Oh

    2005-03-01

    This paper describes research on improving the Brayton cycle efficiency for a high-temperature gas-cooled reactor (HTGR). In this study, we are investigating the efficiency of an indirect helium Brayton cycle for the power conversion side of an HTGR power plant. A reference case based on a 250-MW(thermal) pebble bed HTGR was developed using helium gas as a working fluid in both the primary and power conversion sides. The commercial computer code HYSYS was used for process optimization. A numerical model using the Visual-Basic (V-B) computer language was also developed to assist in the evaluation of the Brayton cycle efficiency. Results from both the HYSYS simulation and the V-B model were compared with Japanese calculations based on the 300-MW(electric) Gas Turbine High-Temperature Reactor (GTHTR) that was developed by the Japan Atomic Energy Research Institute. After benchmarking our models, parametric investigations were performed to see the effect of important parameters on the cycle efficiency. We also investigated single-shaft versus multiple-shaft arrangements for the turbomachinery. The results from this study are applicable to other reactor concepts such as fast gas-cooled reactors, supercritical water reactors, and others. The ultimate goal of this study is to use other fluids such as supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency over that of the helium Brayton cycle. This study is in progress, and the results will be published in a subsequent paper.

  14. A Gas-Cooled-Reactor Closed-Brayton-Cycle Demonstration with Nuclear Heating

    SciTech Connect

    Lipinski, Ronald J.; Wright, Steven A.; Dorsey, Daniel J.; Williamson, Joshua; Peters, Curtis D.; Brown, Nicholas; Jablonski, Jennifer

    2005-02-06

    A gas-cooled reactor may be coupled directly to turbomachinery to form a closed-Brayton-cycle (CBC) system in which the CBC working fluid serves as the reactor coolant. Such a system has the potential to be a very simple and robust space-reactor power system. Gas-cooled reactors have been built and operated in the past, but very few have been coupled directly to the turbomachinery in this fashion. In this paper we describe the option for testing such a system with a small reactor and turbomachinery at Sandia National Laboratories. Sandia currently operates the Annular Core Research Reactor (ACRR) at steady-state powers up to 4 MW and has an adjacent facility with heavy shielding in which another reactor recently operated. Sandia also has a closed-Brayton-Cycle test bed with a converted commercial turbomachinery unit that is rated for up to 30 kWe of power. It is proposed to construct a small experimental gas-cooled reactor core and attach this via ducting to the CBC turbomachinery for cooling and electricity production. Calculations suggest that such a unit could produce about 20 kWe, which would be a good power level for initial surface power units on the Moon or Mars. The intent of this experiment is to demonstrate the stable start-up and operation of such a system. Of particular interest is the effect of a negative temperature power coefficient as the initially cold Brayton gas passes through the core during startup or power changes. Sandia's dynamic model for such a system would be compared with the performance data. This paper describes the neutronics, heat transfer, and cycle dynamics of this proposed system. Safety and radiation issues are presented. The views expressed in this document are those of the author and do not necessarily reflect agreement by the government.

  15. A Gas-Cooled-Reactor Closed-Brayton-Cycle Demonstration with Nuclear Heating

    NASA Astrophysics Data System (ADS)

    Lipinski, Ronald J.; Wright, Steven A.; Dorsey, Daniel J.; Peters, Curtis D.; Brown, Nicholas; Williamson, Joshua; Jablonski, Jennifer

    2005-02-01

    A gas-cooled reactor may be coupled directly to turbomachinery to form a closed-Brayton-cycle (CBC) system in which the CBC working fluid serves as the reactor coolant. Such a system has the potential to be a very simple and robust space-reactor power system. Gas-cooled reactors have been built and operated in the past, but very few have been coupled directly to the turbomachinery in this fashion. In this paper we describe the option for testing such a system with a small reactor and turbomachinery at Sandia National Laboratories. Sandia currently operates the Annular Core Research Reactor (ACRR) at steady-state powers up to 4 MW and has an adjacent facility with heavy shielding in which another reactor recently operated. Sandia also has a closed-Brayton-Cycle test bed with a converted commercial turbomachinery unit that is rated for up to 30 kWe of power. It is proposed to construct a small experimental gas-cooled reactor core and attach this via ducting to the CBC turbomachinery for cooling and electricity production. Calculations suggest that such a unit could produce about 20 kWe, which would be a good power level for initial surface power units on the Moon or Mars. The intent of this experiment is to demonstrate the stable start-up and operation of such a system. Of particular interest is the effect of a negative temperature power coefficient as the initially cold Brayton gas passes through the core during startup or power changes. Sandia's dynamic model for such a system would be compared with the performance data. This paper describes the neutronics, heat transfer, and cycle dynamics of this proposed system. Safety and radiation issues are presented. The views expressed in this document are those of the author and do not necessarily reflect agreement by the government.

  16. Gas core reactors for actinide transmutation. [uranium hexafluoride

    NASA Technical Reports Server (NTRS)

    Clement, J. D.; Rust, J. H.; Wan, P. T.; Chow, S.

    1979-01-01

    The preliminary design of a uranium hexafluoride actinide transmutation reactor to convert long-lived actinide wastes to shorter-lived fission product wastes was analyzed. It is shown that externally moderated gas core reactors are ideal radiators. They provide an abundant supply of thermal neutrons and are insensitive to composition changes in the blanket. For the present reactor, an initial load of 6 metric tons of actinides is loaded. This is equivalent to the quantity produced by 300 LWR-years of operation. At the beginning, the core produces 2000 MWt while the blanket generates only 239 MWt. After four years of irradiation, the actinide mass is reduced to 3.9 metric tonnes. During this time, the blanket is becoming more fissile and its power rapidly approaches 1600 MWt. At the end of four years, continuous refueling of actinides is carried out and the actinide mass is held constant. Equilibrium is essentially achieved at the end of eight years. At equilibrium, the core is producing 1400 MWt and the blanket 1600 MWt. At this power level, the actinide destruction rate is equal to the production rate from 32 LWRs.

  17. Microstructure core photonic crystal fiber for gas sensing applications.

    PubMed

    Morshed, Monir; Imran Hassan, Md; Roy, Tusher Kanti; Uddin, Muhammad Shahin; Abdur Razzak, S M

    2015-10-10

    In this paper, a highly sensitive gas sensor based on the microstructure core and cladding photonic crystal fiber (PCF) is presented over the wavelength range from 1.3 to 2.2 μm, which is advantageous for sensor fabrication. The guiding properties of the proposed structure are dependent on geometrical parameters and wavelengths, which are numerically investigated by using a finite element method (FEM). Introducing the microstructure core makes it possible to obtain higher relative sensitivity and achieves low confinement loss. Moreover, it can be shown that increasing the diameter of the air holes in the microstructure core and decreasing the size of hole to hole space (pitch), the relative sensitivity is enhanced. In addition, the confinement loss is reduced by increasing the value of the diameter of the air holes in the cladding. Simulation results reveal that for the optimum design of the proposed PCF it is possible to obtain the highest relative sensitivity of about 42.27% at the wavelength λ=1.33  μm for the absorption line of methane (CH4) and hydrogen fluoride (HF) gases. In this case, the confinement loss of the fiber is 4.78345×10-6  dB/m. PMID:26479798

  18. Closed-cycle gas dynamic laser design investigation

    NASA Technical Reports Server (NTRS)

    Ketch, G. W.; Young, W. E.

    1977-01-01

    A conceptual design study was made of a closed cycle gas-dynamic laser to provide definition of the major components in the laser loop. The system potential application is for long range power transmission by way of high power laser beams to provide satellite propulsion energy for orbit changing or station keeping. A parametric cycle optimization was conducted to establish the thermodynamic requirements for the system components. A conceptual design was conducted of the closed cycle system and the individual components to define physical characteristics and establish the system size and weight. Technology confirmation experimental demonstration programs were outlined to develop, evaluate, and demonstrate the technology base needed for this closed cycle GDL system.

  19. Gas turbine and combined-cycle capacity enhancement

    SciTech Connect

    1995-01-01

    This report presents interim results of a study of capacity enhancement of gas turbines and combined cycles. A portion of the study is based on a tailored collaboration study for Missouri Public Service. The techniques studied include water injection, steam injection, increased firing temperature, supercharging, and inlet cooling for the gas turbines. The inlet cooling approaches cover evaporative cooling with and without media, water cooling, thermal energy storage (TES) systems using ice or water and continuous refrigeration. Results are given for UTC FT4/GG4, GE MS5001, MS7001, W501 and W251 gas turbines. Duct firing of a three-pressure HRSG for peaking capacity is investigated. The GE PG7221(FA) is used as the reference gas turbine for this combined cycle. The results to-date indicate that the utilities have a number of viable options for capacity enhancement that are dependent on the mission of the gas turbine, local climate, and the design of the gas turbine.

  20. Flowing gas, non-nuclear experiments on the gas core reactor

    NASA Technical Reports Server (NTRS)

    Kunze, J. F.; Cooper, C. G.; Macbeth, P. J.

    1973-01-01

    Variations in cavity wall and injection configurations of the gas core reactor were aimed at establishing flow patterns that give a maximum of the nuclear criticality eigenvalue. Correlation with the nuclear effect was made using multigroup diffusion theory normalized by previous benchmark critical experiments. Air was used to simulate the hydrogen propellant in the flow tests, and smoked air, argon, or Freon to simulate the central nuclear fuel gas. Tests were run both in the down-firing and upfiring directions. Results showed that acceptable flow patterns with volume fraction for the simulated nuclear fuel gas and high flow rate ratios of propellant to fuel can be obtained. Using a point injector for the fuel, good flow patterns are obtained by directing the outer gas at high velocity long the cavity wall, using louvered injection schemes. Recirculation patterns were needed to stabilize the heavy central gas when different gases are used.

  1. The combined cycle application of aeroderivative gas turbines

    SciTech Connect

    Sheard, A.G.; Raine, M.J.

    1998-07-01

    In recent years aeroderivative gas turbines have become an effective alternative to heavy industrial gas turbines. Marketing of aeroderivatives has focused on their simple cycle efficiency advantage. The use of aeroderivatives in combined cycle, however, has also been demonstrated to be competitive, with high net plant efficiency and moderate cost per installed kW. In this paper the rationale for choosing an aeroderivative over a conventional industrial gas turbine is discussed. Factors affecting the decision to opt for either a simple or combined cycle facility are considered. The economic case is made for combined cycle plant incorporating aeroderivatives, showing a lower total cost of ownership than the alternatives, including an assessment of the key factors necessary to make them viable. The paper continues with a description of an advanced ``single string'' power train concept. Implementation of the power train is presented, and its incorporation into an optimized 40 MW Class power station described. Reduction in cost of electricity and installed cost per kW are considered, as well as reduction in project lead time.

  2. Gas-solid reaction-rate enhancement by pressure cycling

    NASA Astrophysics Data System (ADS)

    Sohn, H. Y.; Aboukheshem, M. B.

    1992-06-01

    An experimental study and mathematical modeling of the effects of external pressure cycling on gas-solid reactions have been conducted using the reduction of nickel oxide pellets by hy-drogen. Experiments were carried out in two phases: In the first phase, the intrinsic kinetic parameters were measured, and in the second phase, the gas-solid reaction was carried out under a constant or cycling external pressure. The effects of the frequency and amplitude of pressure cycling were studied at various reaction conditions. Pressure cycling substantially increases the overall rate of the reaction. A mathematical model was developed from the first principles to establish the extent of the overall reaction-rate enhancement and subsequently to analyze the experimental observations. The calculated values from the mathematical model are in good agreement with the experimental results. The effects are most pronounced when the overall rate under a constant pressure is controlled by diffusion. Depending on the reaction condition, a very large degree of rate enhancement could be achieved. Furthermore, low-amplitude pressure waves, like acoustic waves, could significantly increase the rates of gas-solid reactions.

  3. Life cycle water consumption for shale gas and conventional natural gas.

    PubMed

    Clark, Corrie E; Horner, Robert M; Harto, Christopher B

    2013-10-15

    Shale gas production represents a large potential source of natural gas for the nation. The scale and rapid growth in shale gas development underscore the need to better understand its environmental implications, including water consumption. This study estimates the water consumed over the life cycle of conventional and shale gas production, accounting for the different stages of production and for flowback water reuse (in the case of shale gas). This study finds that shale gas consumes more water over its life cycle (13-37 L/GJ) than conventional natural gas consumes (9.3-9.6 L/GJ). However, when used as a transportation fuel, shale gas consumes significantly less water than other transportation fuels. When used for electricity generation, the combustion of shale gas adds incrementally to the overall water consumption compared to conventional natural gas. The impact of fuel production, however, is small relative to that of power plant operations. The type of power plant where the natural gas is utilized is far more important than the source of the natural gas. PMID:24004382

  4. PWR core design, neutronics evaluation and fuel cycle analysis for thorium-uranium breeding recycle

    SciTech Connect

    Bi, G.; Liu, C.; Si, S.

    2012-07-01

    This paper was focused on core design, neutronics evaluation and fuel cycle analysis for Thorium-Uranium Breeding Recycle in current PWRs, without any major change to the fuel lattice and the core internals, but substituting the UOX pellet with Thorium-based pellet. The fuel cycle analysis indicates that Thorium-Uranium Breeding Recycle is technically feasible in current PWRs. A 4-loop, 193-assembly PWR core utilizing 17 x 17 fuel assemblies (FAs) was taken as the model core. Two mixed cores were investigated respectively loaded with mixed reactor grade Plutonium-Thorium (PuThOX) FAs and mixed reactor grade {sup 233}U-Thorium (U{sub 3}ThOX) FAs on the basis of reference full Uranium oxide (UOX) equilibrium-cycle core. The UOX/PuThOX mixed core consists of 121 UOX FAs and 72 PuThOX FAs. The reactor grade {sup 233}U extracted from burnt PuThOX fuel was used to fabrication of U{sub 3}ThOX for starting Thorium-. Uranium breeding recycle. In UOX/U{sub 3}ThOX mixed core, the well designed U{sub 3}ThOX FAs with 1.94 w/o fissile uranium (mainly {sup 233}U) were located on the periphery of core as a blanket region. U{sub 3}ThOX FAs remained in-core for 6 cycles with the discharged burnup achieving 28 GWD/tHM. Compared with initially loading, the fissile material inventory in U{sub 3}ThOX fuel has increased by 7% via 1-year cooling after discharge. 157 UOX fuel assemblies were located in the inner of UOX/U{sub 3}ThOX mixed core refueling with 64 FAs at each cycle. The designed UOX/PuThOX and UOX/U{sub 3}ThOX mixed core satisfied related nuclear design criteria. The full core performance analyses have shown that mixed core with PuThOX loading has similar impacts as MOX on several neutronic characteristic parameters, such as reduced differential boron worth, higher critical boron concentration, more negative moderator temperature coefficient, reduced control rod worth, reduced shutdown margin, etc.; while mixed core with U{sub 3}ThOX loading on the periphery of core has no

  5. Are You There Gas? It's Me, Planet: The Effects of Gas on Growth of Gas Giant Cores through Planetesimal Accretion

    NASA Astrophysics Data System (ADS)

    Wolansky, Natania R.

    2014-04-01

    Before now, models have not been successful in predicting the rapid growth of rocky cores of gas giant planets at large separations from their host stars. Timescales for growth have far outstripped the lifetime of the gaseous disk surrounding the young star, creating a paradox between the need for the core to accrete material and the depleted supply of gas and dust. I present a model for planetary core accretion taking into account the effect of surrounding gas on the dynamics between the core and the accretable material, thus altering the characteristics of the effective cross section of accretion of the planet. By replacing the Hill radius with a wind shearing (WISH) radius, which tracks the point at which a small particle is not sheared away from a core by differential gas drag force, and by imposing additional energy constraints which determine whether a particle will successfully decouple from the gas during its encounter with the core, I recalculate the timescales of growth of a planetary core under a number of varying parameters. I apply the results to the A-type HR8799 star system, including HR8799b, c, and d, roughly 10MJ planets located at a separation of 68, 38, and 24 AU, respectively. Using the model, I reduce the "last doubling" timescales of growth predicted by classical gravitational focusing models by a factor of 1000, from 107 years to 104 years for HR8799b, c, and d, placing timescales of growth in all three cases within acceptable limits to agree with the lifetime of a gaseous disk and the deduced lifetimes of the planets. These results place within the realm of possibility that these 3 planets are formed by core accretion instead of gravitational instability. In exploring the timescales for growth of planetary cores in systems with varying parameters such as star size, disk density, and dust particle size distributions, I provide a model for predicting the possibility of driftless formation of a gas giant given the protoplanetary system

  6. Gas Foil Bearing Technology Advancements for Closed Brayton Cycle Turbines

    NASA Technical Reports Server (NTRS)

    Howard, Samuel A.; Bruckner, Robert J.; DellaCorte, Christopher; Radil, Kevin C.

    2007-01-01

    Closed Brayton Cycle (CBC) turbine systems are under consideration for future space electric power generation. CBC turbines convert thermal energy from a nuclear reactor, or other heat source, to electrical power using a closed-loop cycle. The operating fluid in the closed-loop is commonly a high pressure inert gas mixture that cannot tolerate contamination. One source of potential contamination in a system such as this is the lubricant used in the turbomachine bearings. Gas Foil Bearings (GFB) represent a bearing technology that eliminates the possibility of contamination by using the working fluid as the lubricant. Thus, foil bearings are well suited to application in space power CBC turbine systems. NASA Glenn Research Center is actively researching GFB technology for use in these CBC power turbines. A power loss model has been developed, and the effects of a very high ambient pressure, start-up torque, and misalignment, have been observed and are reported here.

  7. Reducing the risk to Mars: The gas core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Howe, S. D.; DeVolder, B.; Thode, L.; Zerkle, D.

    1998-01-01

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas-core nuclear rocket (GCNR) has the potential to be such a system. The authors have completed a comparative study of the potential impact that a GCNR could have on a manned Mars mission. The total IMLEO, transit times, and accumulated radiation dose to the crew will be compared with the NASA Design Reference Missions.

  8. Reducing the risk to Mars: The gas core nuclear rocket

    NASA Astrophysics Data System (ADS)

    Howe, S. D.; Devolder, B.; Thode, L.; Zerkle, D.

    1998-01-01

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas-core nuclear rocket (GCNR) has the potential to be such a system. We have completed a comparative study of the potential impact that a GCNR could have on a manned Mars mission. The total IMLEO, transit times, and accumulated radiation dose to the crew will be compared with the NASA Design Reference Missions.

  9. Reducing the risk to Mars: The gas core nuclear rocket

    SciTech Connect

    Howe, S. D.; DeVolder, B.; Thode, L.; Zerkle, D.

    1998-01-15

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas-core nuclear rocket (GCNR) has the potential to be such a system. We have completed a comparative study of the potential impact that a GCNR could have on a manned Mars mission. The total IMLEO, transit times, and accumulated radiation dose to the crew will be compared with the NASA Design Reference Missions.

  10. Reducing the risk to Mars: The gas core nuclear rocket

    SciTech Connect

    Howe, S.D.; DeVolder, B.; Thode, L.; Zerkle, D.

    1998-12-31

    The next giant leap for mankind will be the human exploration of Mars. Almost certainly within the next thirty years, a human crew will brave the isolation, the radiation, and the lack of gravity to walk on and explore the Red planet. However, because the mission distances and duration will be hundreds of times greater than the lunar missions, a human crew will face much greater obstacles and a higher risk than those experienced during the Apollo program. A single solution to many of these obstacles is to dramatically decrease the mission duration by developing a high performance propulsion system. The gas-core nuclear rocket (GCNR) has the potential to be such a system. The authors have completed a comparative study of the potential impact that a GCNR could have on a manned Mars mission. The total IMLEO, transit times, and accumulated radiation dose to the crew will be compared with the NASA Design Reference Missions.

  11. Complete Cycle Experiments Using the Adiabatic Gas Law Apparatus

    NASA Astrophysics Data System (ADS)

    Kutzner, Mickey D.; Plantak, Mateja

    2014-10-01

    The ability of our society to make informed energy-usage decisions in the future depends partly on current science and engineering students retaining a deep understanding of the thermodynamics of heat engines. Teacher imaginations and equipment budgets can both be taxed in the effort to engage students in hands-on heat engine activities. The experiments described in this paper, carried out using the Adiabatic Gas Law Apparatus1 (AGLA), quantitatively explore popular complete cycle heat engine processes.

  12. Estimating Externalities of Natural Gas Fuel Cycles, Report 4

    SciTech Connect

    Barnthouse, L.W.; Cada, G.F.; Cheng, M.-D.; Easterly, C.E.; Kroodsma, R.L.; Lee, R.; Shriner, D.S.; Tolbert, V.R.; Turner, R.S.

    1998-01-01

    This report describes methods for estimating the external costs (and possibly benefits) to human health and the environment that result from natural gas fuel cycles. Although the concept of externalities is far from simple or precise, it generally refers to effects on individuals' well being, that result from a production or market activity in which the individuals do not participate, or are not fully compensated. In the past two years, the methodological approach that this report describes has quickly become a worldwide standard for estimating externalities of fuel cycles. The approach is generally applicable to any fuel cycle in which a resource, such as coal, hydro, or biomass, is used to generate electric power. This particular report focuses on the production activities, pollution, and impacts when natural gas is used to generate electric power. In the 1990s, natural gas technologies have become, in many countries, the least expensive to build and operate. The scope of this report is on how to estimate the value of externalities--where value is defined as individuals' willingness to pay for beneficial effects, or to avoid undesirable ones. This report is about the methodologies to estimate these externalities, not about how to internalize them through regulations or other public policies. Notwithstanding this limit in scope, consideration of externalities can not be done without considering regulatory, insurance, and other considerations because these institutional factors affect whether costs (and benefits) are in fact external, or whether they are already somehow internalized within the electric power market. Although this report considers such factors to some extent, much analysis yet remains to assess the extent to which estimated costs are indeed external. This report is one of a series of reports on estimating the externalities of fuel cycles. The other reports are on the coal, oil, biomass, hydro, and nuclear fuel cycles, and on general methodology.

  13. Comments on the feasibility of developing gas core nuclear reactors. [for manned interplanetary spacecraft propulsion

    NASA Technical Reports Server (NTRS)

    Rom, F. E.

    1969-01-01

    Recent developments in the fields of gas core hydrodynamics, heat transfer, and neutronics indicate that gas core nuclear rockets may be feasible from the point of view of basic principles. Based on performance predictions using these results, mission analyses indicate that gas core nuclear rockets may have the potential for reducing the initial weight in orbit of manned interplanetary vehicles by a factor of 5 when compared to the best chemical rocket systems. In addition, there is a potential for reducing total trip times from 450 to 500 days for chemical systems to 250 to 300 days for gas core systems. The possibility of demonstrating the feasibility of gas core nuclear rocket engines by means of a logical series of experiments of increasing difficulty that ends with ground tests of full scale gas core reactors is considered.

  14. Closed cycle versus open cycle gas turbines. A review of A. D. Little's ICOP report, Vol. III

    SciTech Connect

    Not Available

    1984-08-24

    This report addresses the question how coal fired closed cycle gas turbine cogenerators perform economically in comparison to coal fired open cycle gas turbine configurations. The return on equity (ROE) was selected as a measure of economic performance. The investigations determined attainable ROE's for three industries (Agrichemical Products, Brewery, Kraft Paper Mill) for closed and open configurations as proposed in a report on the Industrial Cogeneration Optimization Program. Life cycle analyses were conducted assessing this impact of various parameters upon the rankordering of ROE's for the four topping configurations (one closed cycle, three open cycle gas turbines).

  15. Variable cycle stirling engine and gas leakage control system therefor

    SciTech Connect

    Otters, J.

    1984-12-25

    An improved thermal engine of the type having a displacer body movable between the hot end and the cold end of a chamber for subjecting a fluid within that chamber to a thermodynamic cycle and having a work piston driven by the fluid for deriving a useful work output. The work piston pumps a hydraulic fluid and a hydraulic control valve is connected in line with the hydraulic output conduit such that the flow of hydraulic fluid may be restricted to any desired degree or stopped altogether. The work piston can therefore be controlled by means of a controller device independently from the movement of the displacer such that a variety of engine cycles can be obtained for optimum engine efficiency under varying load conditions. While a Stirling engine cycle is particularly contemplated, other engine cycles may be obtained by controlling the movement of the displacer and work pistons. Also disclosed are a working gas recovery system for controlling leakage of working gas from the displacer chamber, and a compound work piston arrangement for preventing leakage of hydraulic fluid around the work piston into the displacer chamber.

  16. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation

    PubMed Central

    Heath, Garvin A.; O’Donoughue, Patrick; Arent, Douglas J.; Bazilian, Morgan

    2014-01-01

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378

  17. Harmonization of initial estimates of shale gas life cycle greenhouse gas emissions for electric power generation.

    PubMed

    Heath, Garvin A; O'Donoughue, Patrick; Arent, Douglas J; Bazilian, Morgan

    2014-08-01

    Recent technological advances in the recovery of unconventional natural gas, particularly shale gas, have served to dramatically increase domestic production and reserve estimates for the United States and internationally. This trend has led to lowered prices and increased scrutiny on production practices. Questions have been raised as to how greenhouse gas (GHG) emissions from the life cycle of shale gas production and use compares with that of conventionally produced natural gas or other fuel sources such as coal. Recent literature has come to different conclusions on this point, largely due to differing assumptions, comparison baselines, and system boundaries. Through a meta-analytical procedure we call harmonization, we develop robust, analytically consistent, and updated comparisons of estimates of life cycle GHG emissions for electricity produced from shale gas, conventionally produced natural gas, and coal. On a per-unit electrical output basis, harmonization reveals that median estimates of GHG emissions from shale gas-generated electricity are similar to those for conventional natural gas, with both approximately half that of the central tendency of coal. Sensitivity analysis on the harmonized estimates indicates that assumptions regarding liquids unloading and estimated ultimate recovery (EUR) of wells have the greatest influence on life cycle GHG emissions, whereby shale gas life cycle GHG emissions could approach the range of best-performing coal-fired generation under certain scenarios. Despite clarification of published estimates through harmonization, these initial assessments should be confirmed through methane emissions measurements at components and in the atmosphere and through better characterization of EUR and practices. PMID:25049378

  18. A combined gas cooled nuclear reactor and fuel cell cycle

    NASA Astrophysics Data System (ADS)

    Palmer, David J.

    Rising oil costs, global warming, national security concerns, economic concerns and escalating energy demands are forcing the engineering communities to explore methods to address these concerns. It is the intention of this thesis to offer a proposal for a novel design of a combined cycle, an advanced nuclear helium reactor/solid oxide fuel cell (SOFC) plant that will help to mitigate some of the above concerns. Moreover, the adoption of this proposal may help to reinvigorate the Nuclear Power industry while providing a practical method to foster the development of a hydrogen economy. Specifically, this thesis concentrates on the importance of the U.S. Nuclear Navy adopting this novel design for its nuclear electric vessels of the future with discussion on efficiency and thermodynamic performance characteristics related to the combined cycle. Thus, the goals and objectives are to develop an innovative combined cycle that provides a solution to the stated concerns and show that it provides superior performance. In order to show performance, it is necessary to develop a rigorous thermodynamic model and computer program to analyze the SOFC in relation with the overall cycle. A large increase in efficiency over the conventional pressurized water reactor cycle is realized. Both sides of the cycle achieve higher efficiencies at partial loads which is extremely important as most naval vessels operate at partial loads as well as the fact that traditional gas turbines operating alone have poor performance at reduced speeds. Furthermore, each side of the cycle provides important benefits to the other side. The high temperature exhaust from the overall exothermic reaction of the fuel cell provides heat for the reheater allowing for an overall increase in power on the nuclear side of the cycle. Likewise, the high temperature helium exiting the nuclear reactor provides a controllable method to stabilize the fuel cell at an optimal temperature band even during transients helping

  19. PLANETARY CORE FORMATION WITH COLLISIONAL FRAGMENTATION AND ATMOSPHERE TO FORM GAS GIANT PLANETS

    SciTech Connect

    Kobayashi, Hiroshi; Krivov, Alexander V.; Tanaka, Hidekazu

    2011-09-01

    Massive planetary cores ({approx}10 Earth masses) trigger rapid gas accretion to form gas giant planets such as Jupiter and Saturn. We investigate the core growth and the possibilities for cores to reach such a critical core mass. At the late stage, planetary cores grow through collisions with small planetesimals. Collisional fragmentation of planetesimals, which is induced by gravitational interaction with planetary cores, reduces the amount of planetesimals surrounding them, and thus the final core masses. Starting from small planetesimals that the fragmentation rapidly removes, less massive cores are formed. However, planetary cores acquire atmospheres that enlarge their collisional cross section before rapid gas accretion. Once planetary cores exceed about Mars mass, atmospheres significantly accelerate the growth of cores. We show that, taking into account the effects of fragmentation and atmosphere, initially large planetesimals enable formation of sufficiently massive cores. On the other hand, because the growth of cores is slow for large planetesimals, a massive disk is necessary for cores to grow enough within a disk lifetime. If the disk with 100 km sized initial planetesimals is 10 times as massive as the minimum mass solar nebula, planetary cores can exceed 10 Earth masses in the Jovian planet region (>5 AU).

  20. Greenhouse Gas Emissions from the Nuclear Fuel Cycle

    SciTech Connect

    Strom, Daniel J.

    2010-03-01

    Since greenhouse gases are a global concern, rather than a local concern as are some kinds of effluents, one must compare the entire lifecycle of nuclear power to alternative technologies for generating electricity. A recent critical analysis by Sovacool (2008) gives a clearer picture. "It should be noted that nuclear power is not directly emitting greenhouse gas emissions, but rather that lifecycle emissions occur through plant construction, operation, uranium mining and milling, and plant decommissioning." "[N]uclear energy is in no way 'carbon free' or 'emissions free,' even though it is much better (from purely a carbon-equivalent emissions standpoint) than coal, oil, and natural gas electricity generators, but worse than renewable and small scale distributed generators" (Sovacool 2008). According to Sovacool, at an estimated 66 g CO2 equivalent per kilowatt-hour (gCO2e/kWh), nuclear power emits 15 times less CO2 per unit electricity generated than unscrubbed coal generation (at 1050 gCO2e/kWh), but 7 times more than the best renewable, wind (at 9 gCO2e/kWh). The U.S. Nuclear Regulatory Commission (2009) has long recognized CO2 emissions in its regulations concerning the environmental impact of the nuclear fuel cycle. In Table S-3 of 10 CFR 51.51(b), NRC lists a 1000-MW(electric) nuclear plant as releasing as much CO2 as a 45-MW(e) coal plant. A large share of the carbon emissions from the nuclear fuel cycle is due to the energy consumption to enrich uranium by the gaseous diffusion process. A switch to either gas centrifugation or laser isotope separation would dramatically reduce the carbon emissions from the nuclear fuel cycle.

  1. Gas core nuclear thermal rocket engine research and development in the former USSR

    SciTech Connect

    Koehlinger, M.W.; Bennett, R.G.; Motloch, C.G.; Gurfink, M.M.

    1992-09-01

    Beginning in 1957 and continuing into the mid 1970s, the USSR conducted an extensive investigation into the use of both solid and gas core nuclear thermal rocket engines for space missions. During this time the scientific and engineering. problems associated with the development of a solid core engine were resolved. At the same time research was undertaken on a gas core engine, and some of the basic engineering problems associated with the concept were investigated. At the conclusion of the program, the basic principles of the solid core concept were established. However, a prototype solid core engine was not built because no established mission required such an engine. For the gas core concept, some of the basic physical processes involved were studied both theoretically and experimentally. However, no simple method of conducting proof-of-principle tests in a neutron flux was devised. This report focuses primarily on the development of the. gas core concept in the former USSR. A variety of gas core engine system parameters and designs are presented, along with a summary discussion of the basic physical principles and limitations involved in their design. The parallel development of the solid core concept is briefly described to provide an overall perspective of the magnitude of the nuclear thermal propulsion program and a technical comparison with the gas core concept.

  2. Solar/gas Brayton/Rankine cycle heat pump assessment

    NASA Astrophysics Data System (ADS)

    Rousseau, J.; Liu, A. Y.

    1982-05-01

    A 10-ton gas-fired heat pump is currently under development at AiResearch under joint DOE and GRI sponsorship. This heat pump features a highly efficient, recuperated, subatmospheric Brayton-cycle engine which drives the centrifugal compressor of a reversible vapor compression heat pump. The investigations under this program were concerned initially with the integration of this machine with a parabolic dish-type solar collector. Computer models were developed to accurately describe the performance of the heat pump packaged in this fashion. The study determined that (1) only a small portion (20 to 50 percent) of the available solar energy could be used because of a fundamental mismatch between the heating and cooling demand and the availability of solar energy, and (2) the simple pay back period, by comparison to the baseline non-solar gas-fired heat pump, was unacceptable (15 to 36 years).

  3. The first Greenland ice core record of methanesulfonate and sulfate over a full glacial cycle

    SciTech Connect

    Hansson, M.E.; Saltzman, E.S. )

    1993-06-18

    The authors report on methanesulfonate and non-seasalt sulfate found in an artic ice core from Greenland. The ice core record stretches back in time roughly 130,000 years, through a full glacial cycle. This record reveals a decreasing concentration of MSA with the advance of the glacial period, and a drop in temperatures, while the non-seasalt sulfate increased in concentration. The MSA data is in contrast to similar measurements from the southern hemisphere. The ratio of MSA to non-seasalt sulfate is found to have a strong linear relationship to the temperature, higher ratios being associated with warmer climatic periods.

  4. A Supercritical CO{sub 2} Gas Turbine Power Cycle for Next-Generation Nuclear Reactors

    SciTech Connect

    Dostal, Vaclav; Driscoll, Michael J.; Hejzlar, Pavel; Todreas, Neil E.

    2002-07-01

    Although proposed more than 35 years ago, the use of supercritical CO{sub 2} as the working fluid in a closed circuit Brayton cycle has so far not been implemented in practice. Industrial experience in several other relevant applications has improved prospects, and its good efficiency at modest temperatures (e.g., {approx}45% at 550 deg. C) make this cycle attractive for a variety of advanced nuclear reactor concepts. The version described here is for a gas-cooled, modular fast reactor. In the proposed gas-cooled fast breeder reactor design of present interest, CO{sub 2} is also especially attractive because it allows the use of metal fuel and core structures. The principal advantage of a supercritical CO{sub 2} Brayton cycle is its reduced compression work compared to an ideal gas such as helium: about 15% of gross power turbine output vs. 40% or so. This also permits the simplification of use of a single compressor stage without inter-cooling. The requisite high pressure ({approx}20 MPa) also has the benefit of more compact heat exchangers and turbines. Finally, CO{sub 2} requires significantly fewer turbine stages than He, its principal competitor for nuclear gas turbine service. One disadvantage of CO{sub 2} in a direct cycle application is the production of N-16, which will require turbine plant shielding (albeit much less than in a BWR). The cycle efficiency is also very sensitive to recuperator effectiveness and compressor inlet temperature. It was found necessary to split the recuperator into separate high-and low-temperature components, and to employ intermediate re-compression, to avoid having a pinch-point in the cold end of the recuperator. Over the past several decades developments have taken place that make the acceptance of supercritical CO{sub 2} systems more likely: supercritical CO{sub 2} pipelines are in use in the western US in oil-recovery operations; 14 advanced gas-cooled reactors (AGR) are employed in the UK at CO{sub 2} temperatures up to

  5. Cycling of Dense Core Vesicles Involved in Somatic Exocytosis of Serotonin by Leech Neurons

    PubMed Central

    Trueta, Citlali; Kuffler, Damien P.; De-Miguel, Francisco F.

    2012-01-01

    We studied the cycling of dense core vesicles producing somatic exocytosis of serotonin. Our experiments were made using electron microscopy and vesicle staining with fluorescent dye FM1-43 in Retzius neurons of the leech, which secrete serotonin from clusters of dense core vesicles in a frequency-dependent manner. Electron micrographs of neurons at rest or after 1 Hz stimulation showed two pools of dense core vesicles. A perinuclear pool near Golgi apparatuses, from which vesicles apparently form, and a peripheral pool with vesicle clusters at a distance from the plasma membrane. By contrast, after 20 Hz electrical stimulation 47% of the vesicle clusters were apposed to the plasma membrane, with some omega exocytosis structures. Dense core and small clear vesicles apparently originating from endocytosis were incorporated in multivesicular bodies. In another series of experiments, neurons were stimulated at 20 Hz while bathed in a solution containing peroxidase. Electron micrographs of these neurons contained gold particles coupled to anti-peroxidase antibodies in dense core vesicles and multivesicular bodies located near the plasma membrane. Cultured neurons depolarized with high potassium in the presence of FM1-43 displayed superficial fluorescent spots, each reflecting a vesicle cluster. A partial bleaching of the spots followed by another depolarization in the presence of FM1-43 produced restaining of some spots, other spots disappeared, some remained without restaining and new spots were formed. Several hours after electrical stimulation the FM1-43 spots accumulated at the center of the somata. This correlated with electron micrographs of multivesicular bodies releasing their contents near Golgi apparatuses. Our results suggest that dense core vesicle cycling related to somatic serotonin release involves two steps: the production of clear vesicles and multivesicular bodies after exocytosis, and the formation of new dense core vesicles in the perinuclear

  6. Compact and Robust Refilling and Connectorization of Hollow Core Photonic Crystal Fiber Gas Reference Cells

    NASA Technical Reports Server (NTRS)

    Poberezhskiy, Ilya Y.; Meras, Patrick; Chang, Daniel H.; Spiers, Gary D.

    2007-01-01

    This slide presentation reviews a method for refilling and connectorization of hollow core photonic crystal fiber gas reference cells. Thees hollow-core photonic crystal fiber allow optical propagation in air or vacuum and are for use as gas reference cell is proposed and demonstrated. It relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers.

  7. Influence of quantum degeneracy on the performance of a gas Stirling engine cycle

    NASA Astrophysics Data System (ADS)

    He, Ji-Zhou; Mao, Zhi-Yuan; Wang, Jian-Hui

    2006-09-01

    Based on the state equation of an ideal quantum gas, the regenerative loss of a Stirling engine cycle working with an ideal quantum gas is calculated. Thermal efficiency of the cycle is derived. Furthermore, under the condition of quantum degeneracy, several special thermal efficiencies are discussed. Ratios of thermal efficiencies versus the temperature ratio and volume ratio of the cycle are made. It is found that the thermal efficiency of the cycle not only depends on high and low temperatures but also on maximum and minimum volumes. In a classical gas state the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal quantum gas state the thermal efficiency of the cycle is smaller than that of the Carnot cycle. This will be significant for deeper understanding of the gas Stirling engine cycle.

  8. Effect of Gas/Steam Turbine Inlet Temperatures on Combined Cycle Having Air Transpiration Cooled Gas Turbine

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Singh, O.

    2012-10-01

    Worldwide efforts are being made for further improving the gas/steam combined cycle performance by having better blade cooling technology in topping cycle and enhanced heat recovery in bottoming cycle. The scope of improvement is possible through turbines having higher turbine inlet temperatures (TITs) of both gas turbine and steam turbine. Literature review shows that a combined cycle with transpiration cooled gas turbine has not been analyzed with varying gas/steam TITs. In view of above the present study has been undertaken for thermodynamic study of gas/steam combined cycle with respect to variation in TIT in both topping and bottoming cycles, for air transpiration cooled gas turbine. The performance of combined cycle with dual pressure heat recovery steam generator has been evaluated for different cycle pressure ratios (CPRs) varying from 11 to 23 and the selection diagrams presented for TIT varying from 1,600 to 1,900 K. Both the cycle efficiency and specific work increase with TIT for each pressure ratio. For each TIT there exists an optimum pressure ratio for cycle efficiency and specific work. For the CPR of 23 the best cycle performance is seen at a TIT of 1,900 K for maximum steam temperature of 570 °C, which gives the cycle efficiency of 60.9 % with net specific work of 909 kJ/kg.

  9. Comparisons of in situ and core gas measurements in ODP Leg 164 bore holes

    USGS Publications Warehouse

    Paull, C.K.; Lorenson, T.D.; Dickens, G.; Borowski, W.S.; Ussler, W., III; Kvenvolden, K.

    2000-01-01

    During Ocean Drilling Program Leg 164, an unprecedented effort was made to determine the amounts of gas and gas hydrate in the sediments from Sites 994, 995, and 997. For the first time in the history of academic drilling, a pressure core sampler (PCS) worked well enough to generate an independent stratigraphy of in situ gas concentrations and compositions with depth. Here, gas concentrations and composition data produced by routine shipboard gas sampling techniques are compared with PCS data.

  10. Non-Proliferative, Thorium-Based, Core and Fuel Cycle for Pressurized Water Reactors

    SciTech Connect

    Todosow M.; Todosow M.; Raitses, G. Galperin, A.

    2009-07-12

    Two of the major barriers to the expansion of worldwide adoption of nuclear power are related to proliferation potential of the nuclear fuel cycle and issues associated with the final disposal of spent fuel. The Radkowsky Thorium Fuel (RTF) concept proposed by Professor A. Radkowsky offers a partial solution to these problems. The main idea of the concept is the utilization of the seed-blanket unit (SBU) fuel assembly geometry which is a direct replacement for a 'conventional' assembly in either a Russian pressurized water reactor (VVER-1000) or a Western pressurized water reactor (PWR). The seed-blanket fuel assembly consists of a fissile (U) zone, known as seed, and a fertile (Th) zone known as blanket. The separation of fissile and fertile allows separate fuel management schemes for the thorium part of the fuel (a subcritical 'blanket') and the 'driving' part of the core (a supercritical 'seed'). The design objective for the blanket is an efficient generation and in-situ fissioning of the U233 isotope, while the design objective for the seed is to supply neutrons to the blanket in a most economic way, i.e. with minimal investment of natural uranium. The introduction of thorium as a fertile component in the nuclear fuel cycle significantly reduces the quantity of plutonium production and modifies its isotopic composition, reducing the overall proliferation potential of the fuel cycle. Thorium based spent fuel also contains fewer higher actinides, hence reducing the long-term radioactivity of the spent fuel. The analyses show that the RTF core can satisfy the requirements of fuel cycle length, and the safety margins of conventional pressurized water reactors. The coefficients of reactivity are comparable to currently operating VVER's/PWR's. The major feature of the RTF cycle is related to the total amount of spent fuel discharged for each cycle from the reactor core. The fuel management scheme adopted for RTF core designs allows a significant decrease in the

  11. A fusion-driven gas core nuclear rocket

    SciTech Connect

    Kammash, T.; Godfroy, T.

    1998-01-15

    A magnetic confinement scheme is investigated as a potential propulsion device in which thrust is generated by a propellant heated by radiation emanating from a fusion plasma. The device in question is the gasdynamic mirror (GDM) machine in which a hot dense plasma is confined long enough to generate fusion energy while allowing a certain fraction of its charged particle population to go through one end to a direct converter. The energy of these particles is converted into electric power which is recirculated to sustain the steady state operation of the system. The injected power heats the plasma to thermonuclear temperatures where the resulting fusion energy appears a charged particle power, neutron power, and radiated power in the form of bremsstrahlung and synchrotron radiation. The neutron power can be converted through a thermal converter to electric power that can be combined with the direct converter power before being fed into the injector. The radiated power, on the other hand, can be used to heat a hydrogen propellant introduced into the system at a specified pressure and mass flow rate. This propellant can be pre-heated by regeneratively cooling the (mirror) nozzle or other components of the system if feasible, or by an electrothermal unit powered by portions of the recirculated power. Using a simple heat transfer model that ignores the heat flux to the wall, and assuming total absorption of radiation energy by the propellant it is shown that such a gas core rocket is capable of producing tens of kilonewtons of thrust and several thousands of seconds of specific impulse. It is also shown that the familiar Kelvin-Helmholtz instability which arises from the relative motion of the neutral hydrogen to the ionized fuel is not likely to occur in this system due to the presence of the confining magnetic field.

  12. A fusion-driven gas core nuclear rocket

    NASA Astrophysics Data System (ADS)

    Kammash, T.; Godfroy, T.

    1998-01-01

    A magnetic confinement scheme is investigated as a potential propulsion device in which thrust is generated by a propellant heated by radiation emanating from a fusion plasma. The device in question is the gasdynamic mirror (GDM) machine in which a hot dense plasma is confined long enough to generate fusion energy while allowing a certain fraction of its charged particle population to go through one end to a direct converter. The energy of these particles is converted into electric power which is recirculated to sustain the steady state operation of the system. The injected power heats the plasma to thermonuclear temperatures where the resulting fusion energy appears a charged particle power, neutron power, and radiated power in the form of bremsstrahlung and synchrotron radiation. The neutron power can be converted through a thermal converter to electric power that can be combined with the direct converter power before being fed into the injector. The radiated power, on the other hand, can be used to heat a hydrogen propellant introduced into the system at a specified pressure and mass flow rate. This propellant can be pre-heated by regeneratively cooling the (mirror) nozzle or other components of the system if feasible, or by an electrothermal unit powered by portions of the recirculated power. Using a simple heat transfer model that ignores the heat flux to the wall, and assuming total absorption of radiation energy by the propellant it is shown that such a gas core rocket is capable of producing tens of kilonewtons of thrust and several thousands of seconds of specific impulse. It is also shown that the familiar Kelvin-Helmholtz instability which arises from the relative motion of the neutral hydrogen to the ionized fuel is not likely to occur in this system due to the presence of the confining magnetic field.

  13. Modeling and design of a reload PWR core for a 48-month fuel cycle

    SciTech Connect

    McMahon, M.V.; Driscoll, M.J.; Todreas, N.E.

    1997-05-01

    The objective of this research was to use state-of-the-art nuclear and fuel performance packages to evaluate the feasibility and costs of a 48 calendar month core in existing pressurized water reactor (PWR) designs, considering the full range of practical design and economic considerations. The driving force behind this research is the desire to make nuclear power more economically competitive with fossil fuel options by expanding the scope for achievement of higher capacity factors. Using CASMO/SIMULATE, a core design with fuel enriched to 7{sup w}/{sub o} U{sup 235} for a single batch loaded, 48-month fuel cycle has been developed. This core achieves an ultra-long cycle length without exceeding current fuel burnup limits. The design uses two different types of burnable poisons. Gadolinium in the form of gadolinium oxide (Gd{sub 2}O{sub 3}) mixed with the UO{sub 2} of selected pins is sued to hold down initial reactivity and to control flux peaking throughout the life of the core. A zirconium di-boride (ZrB{sub 2}) integral fuel burnable absorber (IFBA) coating on the Gd{sub 2}O{sub 3}-UO{sub 2} fuel pellets is added to reduce the critical soluble boron concentration in the reactor coolant to within acceptable limits. Fuel performance issues of concern to this design are also outlined and areas which will require further research are highlighted.

  14. Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 2: Advanced energy conversion systems. Part 1: Open-cycle gas turbines

    NASA Technical Reports Server (NTRS)

    Brown, D. H.; Corman, J. C.

    1976-01-01

    Ten energy conversion systems are defined and analyzed in terms of efficiency. These include: open-cycle gas turbine recuperative; open-cycle gas turbine; closed-cycle gas turbine; supercritical CO2 cycle; advanced steam cycle; liquid metal topping cycle; open-cycle MHD; closed-cycle inert gas MHD; closed-cycle liquid metal MHD; and fuel cells. Results are presented.

  15. Investigation of Freeze and Thaw Cycles of a Gas-Charged Heat Pipe

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Ottenstein, Laura; Krimchansky, Alexander

    2012-01-01

    The traditional constant conductance heat pipes (CCHPs) currently used on most spacecraft run the risk of bursting the pipe when the working fluid is frozen and later thawed. One method to avoid pipe bursting is to use a gas-charged heat pipe (GCHP) that can sustain repeated freeze/thaw cycles. The construction of the GCHP is similar to that of the traditional CCHP except that a small amount of non-condensable gas (NCG) is introduced and a small length is added to the CCHP condenser to serve as the NCG reservoir. During the normal operation, the NCG is mostly confined to the reservoir, and the GCHP functions as a passive variable conductance heat pipe (VCHP). When the liquid begins to freeze in the condenser section, the NCG will expand to fill the central core of the heat pipe, and ice will be formed only in the grooves located on the inner surface of the heat pipe in a controlled fashion. The ice will not bridge the diameter of the heat pipe, thus avoiding the risk of pipe bursting during freeze/thaw cycles. A GCHP using ammonia as the working fluid was fabricated and then tested inside a thermal vacuum chamber. The GCHP demonstrated a heat transport capability of more than 200W at 298K as designed. Twenty-seven freeze/thaw cycles were conducted under various conditions where the evaporator temperature ranged from 163K to 253K and the condenser/reservoir temperatures ranged from 123K to 173K. In all tests, the GCHP restarted without any problem with heat loads between 10W and 100W. No performance degradation was noticed after 27 freeze/thaw cycles. The ability of the GCHP to sustain repeated freeze/thaw cycles was thus successfully demonstrated.

  16. EMBRYO IMPACTS AND GAS GIANT MERGERS. I. DICHOTOMY OF JUPITER AND SATURN's CORE MASS

    SciTech Connect

    Li Shulin; Agnor, C.B.; Lin, D. N. C.

    2010-09-10

    Interior to the gaseous envelopes of Saturn, Uranus, and Neptune, there are high-density cores with masses larger than 10 Earth masses. According to the conventional sequential accretion hypothesis, such massive cores are needed for the onset of efficient accretion of their gaseous envelopes. However, Jupiter's gaseous envelope is more massive and its core may be less massive than those of Saturn. In order to account for this structural diversity and the super-solar metallicity in the envelope of Jupiter and Saturn, we investigate the possibility that they may have either merged with other gas giants or consumed several Earth-mass protoplanetary embryos during or after the rapid accretion of their envelope. In general, impinging sub-Earth-mass planetesimals disintegrate in gas giants' envelopes, deposit heavy elements well outside the cores, and locally suppress the convection. Consequently, their fragments sediment to promote the growth of cores. Through a series of numerical simulations, we show that it is possible for colliding super-Earth-mass embryos to reach the cores of gas giants. Direct parabolic collisions also lead to the coalescence of gas giants and merging of their cores. In these cases, the energy released from the impact leads to vigorous convective motion throughout the envelope and the erosion of the cores. This dichotomy contributes to the observed dispersion in the internal structure and atmospheric composition between Jupiter and Saturn and other gas giant planets and elsewhere.

  17. Core exosome-independent roles for Rrp6 in cell cycle progression.

    PubMed

    Graham, Amy C; Kiss, Daniel L; Andrulis, Erik D

    2009-04-01

    Exosome complexes are 3' to 5' exoribonucleases composed of subunits that are critical for numerous distinct RNA metabolic (ribonucleometabolic) pathways. Several studies have implicated the exosome subunits Rrp6 and Dis3 in chromosome segregation and cell division but the functional relevance of these findings remains unclear. Here, we report that, in Drosophila melanogaster S2 tissue culture cells, dRrp6 is required for cell proliferation and error-free mitosis, but the core exosome subunit Rrp40 is not. Micorarray analysis of dRrp6-depleted cell reveals increased levels of cell cycle- and mitosis-related transcripts. Depletion of dRrp6 elicits a decrease in the frequency of mitotic cells and in the mitotic marker phospho-histone H3 (pH3), with a concomitant increase in defects in chromosome congression, separation, and segregation. Endogenous dRrp6 dynamically redistributes during mitosis, accumulating predominantly but not exclusively on the condensed chromosomes. In contrast, core subunits localize predominantly to MTs throughout cell division. Finally, dRrp6-depleted cells treated with microtubule poisons exhibit normal kinetochore recruitment of the spindle assembly checkpoint protein BubR1 without restoring pH3 levels, suggesting that these cells undergo premature chromosome condensation. Collectively, these data support the idea that dRrp6 has a core exosome-independent role in cell cycle and mitotic progression. PMID:19225159

  18. Magnetization, anomalous Barkhausen effect, and core loss of Supermendur under high temperature cycling.

    NASA Technical Reports Server (NTRS)

    Niedra, J. M.; Schwarze, G. E.

    1971-01-01

    The magnetization and core loss of Supermendur were measured up to 900 C under conditions of slow temperature cycling in vacuum. As a consequence of this heating, the coercivity at 25 C increased from 21 A/m to about 110 A/m. This increase is less than previously reported. A prominent anomalous Barkhausen effect, pinched-in hysteresis loops, and a magnetic viscosity field in excess of 20 A/m were observed in the range of 600 to 700 C. At 850 C, Supermendur had a coercivity of 23 A/m, a saturation induction exceeding 1.5 T, a core loss of 26 W/kg at 400 Hz, and a maximum induction of 1.5 T. Supermendur may be useful for high temperature soft magnetic material applications where some history dependence of properties and instability of minor loops at lower temperatures is acceptable.

  19. Inert gas stratigraphy of Apollo 15 drill core sections 15001 and 15003

    NASA Technical Reports Server (NTRS)

    Huebner, W.; Kirsten, T.; Heymann, D.

    1973-01-01

    Rare gase contents were studied in Apollo 15 drill core sections corresponding to 207 to 238 and 125 to 161-cm depths, with respect to layering of the core, turnover on a centimeter scale, and cosmic proton bombardment history. Trapped gas abundance was established in all samples, the mean grain size being a major factor influencing the absolute rare gas contents. Analysis of the results suggests that the regolith materials were exposed to galactic and solar cosmic rays long before their deposition.

  20. CRITICAL CORE MASSES FOR GAS GIANT FORMATION WITH GRAIN-FREE ENVELOPES

    SciTech Connect

    Hori, Yasunori; Ikoma, Masahiro

    2010-05-10

    We investigate the critical core mass and the envelope growth timescale, assuming grain-free envelopes, to examine how small cores are allowed to form gas giants in the framework of the core-accretion model. This is motivated by a theoretical dilemma concerning Jupiter formation: modelings of Jupiter's interior suggest that it contains a small core of <10 M{sub +}, while many core-accretion models of Jupiter formation require a large core of >10 M{sub +} to finish its formation by the time of disk dissipation. Reduction of opacity in the accreting envelope is known to hasten gas giant formation. Almost all the previous studies assumed grain-dominated opacity in the envelope. Instead, we examine cases of grain-free envelopes in this study. Our numerical simulations show that an isolated core of as small as 1.7 M{sub +} is able to capture disk gas to form a gas giant on a timescale of million years if the accreting envelope is grain free; that value decreases to 0.75 M{sub +} if the envelope is metal free, namely, composed purely of hydrogen and helium. It is also shown that alkali atoms, which are known to be one of the dominant opacity sources near 1500 K in the atmospheres of hot Jupiters, have little contribution to determine the critical core mass. Our results confirm that sedimentation and coagulation of grains in the accreting envelope is a key to resolve the dilemma about Jupiter formation.

  1. Coordinated optimization of the parameters of the cooled gas-turbine flow path and the parameters of gas-turbine cycles and combined-cycle power plants

    NASA Astrophysics Data System (ADS)

    Kler, A. M.; Zakharov, Yu. B.; Potanina, Yu. M.

    2014-06-01

    In the present paper, we evaluate the effectiveness of the coordinated solution to the optimization problem for the parameters of cycles in gas turbine and combined cycle power plants and to the optimization problem for the gas-turbine flow path parameters within an integral complex problem. We report comparative data for optimizations of the combined cycle power plant at coordinated and separate optimizations, when, first, the gas turbine and, then, the steam part of a combined cycle plant is optimized. The comparative data are presented in terms of economic indicators, energy-effectiveness characteristics, and specific costs. Models that were used in the present study for calculating the flow path enable taking into account, as a factor influencing the economic and energy effectiveness of the power plant, the heat stability of alloys from which the nozzle and rotor blades of gas-turbine stages are made.

  2. Fuel-Cycle and Nuclear Material Disposition Issues Associated with High-Temperature Gas Reactors

    SciTech Connect

    Shropshire, D.E.; Herring, J.S.

    2004-10-03

    The objective of this paper is to facilitate a better understanding of the fuel-cycle and nuclear material disposition issues associated with high-temperature gas reactors (HTGRs). This paper reviews the nuclear fuel cycles supporting early and present day gas reactors, and identifies challenges for the advanced fuel cycles and waste management systems supporting the next generation of HTGRs, including the Very High Temperature Reactor, which is under development in the Generation IV Program. The earliest gas-cooled reactors were the carbon dioxide (CO2)-cooled reactors. Historical experience is available from over 1,000 reactor-years of operation from 52 electricity-generating, CO2-cooled reactor plants that were placed in operation worldwide. Following the CO2 reactor development, seven HTGR plants were built and operated. The HTGR came about from the combination of helium coolant and graphite moderator. Helium was used instead of air or CO2 as the coolant. The helium gas has a significant technical base due to the experience gained in the United States from the 40-MWe Peach Bottom and 330-MWe Fort St. Vrain reactors designed by General Atomics. Germany also built and operated the 15-MWe Arbeitsgemeinschaft Versuchsreaktor (AVR) and the 300-MWe Thorium High-Temperature Reactor (THTR) power plants. The AVR, THTR, Peach Bottom and Fort St. Vrain all used fuel containing thorium in various forms (i.e., carbides, oxides, thorium particles) and mixtures with highly enriched uranium. The operational experience gained from these early gas reactors can be applied to the next generation of nuclear power systems. HTGR systems are being developed in South Africa, China, Japan, the United States, and Russia. Elements of the HTGR system evaluated included fuel demands on uranium ore mining and milling, conversion, enrichment services, and fuel fabrication; fuel management in-core; spent fuel characteristics affecting fuel recycling and refabrication, fuel handling, interim

  3. A thermionic topping cycle for advanced gas turbines

    SciTech Connect

    Paramonov, D.V.; Carelli, M.D.

    1998-07-01

    Thermionic energy converters (TICs) operate at high temperatures (1300--2300 K) and appear to be attractive for topping cycle (TC) applications of terrestrial fossil power plants where such high temperatures exist in combustion chambers. Thermionic TCs had been considered earlier for various types of gas and steam turbine power plants and cogeneration plants. The idea of the thermionic TC is follows: hot gases in the combustion chamber heat the TIC emitters (typically up to approximately 1600--2000 K), and collectors are cooled (approximately 900--1000 K) with air which is returned into the combustion chamber. Work performed in the early 80's under the DOE thermionic technology program had demonstrated that the use of thermionic TC on a GT might increase the overall efficiency and power output by several percentage points with an incremental efficiency of 70--88 %. In this paper the feasibility of increasing conversion efficiency of advanced GT plants (particularly Westinghouse 501ATS) using state-of-the-art and advanced thermionic technology is assessed. Four TIC types were considered in application to the GT TC. They include: conventional Cs ignited mode TIC; TIC with oxygenated electrodes; high temperature Cs-Ba TIC operating in Knudsen mode, and microgap TIC. The Westinghouse 501ATS was used as the basis for the TC analysis.

  4. Performance potential of gas-core and fusion rockets - A mission applications survey.

    NASA Technical Reports Server (NTRS)

    Fishbach, L. H.; Willis, E. A., Jr.

    1971-01-01

    This paper reports an evaluation of the performance potential of five nuclear rocket engines for four mission classes. These engines are: the regeneratively cooled gas-core nuclear rocket; the light bulb gas-core nuclear rocket; the space-radiator cooled gas-core nuclear rocket; the fusion rocket; and an advanced solid-core nuclear rocket which is included for comparison. The missions considered are: earth-to-orbit launch; near-earth space missions; close interplanetary missions; and distant interplanetary missions. For each of these missions, the capabilities of each rocket engine type are compared in terms of payload ratio for the earth launch mission or by the initial vehicle mass in earth orbit for space missions (a measure of initial cost). Other factors which might determine the engine choice are discussed. It is shown that a 60 day manned round trip to Mars is conceivable.-

  5. The Structure of Gas-accreting Protoplanets and the Condition of the Critical Core Mass

    NASA Astrophysics Data System (ADS)

    Kanagawa, Kazuhiro D.; Fujimoto, Masayuki Y.

    2013-03-01

    In the core accretion model for the formation of gas giant planets, runaway gas accretion onto a core is the primary requisite, triggered when the core mass reaches a critical value. The recently revealed wide diversity of the extrasolar giant planets suggests the necessity to further the understanding of the conditions resulting in the critical core mass that initiates runaway accretion. We study the internal structure of protoplanets under hydrostatic and thermal equilibria represented in terms of a polytropic equation of state to investigate what factors determine and affect the critical core mass. We find that the protoplanets, embedded in protoplanetary disks, have the same configuration as red giants, characterized by the envelope of the centrally condensed type solution. Applying the theory of stellar structure with homology invariants, we demonstrate that there are three types of criteria for the critical core mass depending on the stiffness of polytrope and the nature of outer boundary condition. For the stiff polytropes of index N <= 3 with the Bondi radius as the outer boundary, the criterion governing the critical core mass occurs at the surface. For stiff polytropes with the Hill outer boundary and for soft polytropes of N > 3, this criterion acts at the bottom of gaseous envelope. Further, we elucidate the roles and effects of coexistent radiative and convective zones in the envelope of critical core mass. Based on the results, we discuss the relevance of Bondi and Hill surface conditions and explore the parameter dependences of critical core mass.

  6. THE STRUCTURE OF GAS-ACCRETING PROTOPLANETS AND THE CONDITION OF THE CRITICAL CORE MASS

    SciTech Connect

    Kanagawa, Kazuhiro D.; Fujimoto, Masayuki Y.

    2013-03-01

    In the core accretion model for the formation of gas giant planets, runaway gas accretion onto a core is the primary requisite, triggered when the core mass reaches a critical value. The recently revealed wide diversity of the extrasolar giant planets suggests the necessity to further the understanding of the conditions resulting in the critical core mass that initiates runaway accretion. We study the internal structure of protoplanets under hydrostatic and thermal equilibria represented in terms of a polytropic equation of state to investigate what factors determine and affect the critical core mass. We find that the protoplanets, embedded in protoplanetary disks, have the same configuration as red giants, characterized by the envelope of the centrally condensed type solution. Applying the theory of stellar structure with homology invariants, we demonstrate that there are three types of criteria for the critical core mass depending on the stiffness of polytrope and the nature of outer boundary condition. For the stiff polytropes of index N {<=} 3 with the Bondi radius as the outer boundary, the criterion governing the critical core mass occurs at the surface. For stiff polytropes with the Hill outer boundary and for soft polytropes of N > 3, this criterion acts at the bottom of gaseous envelope. Further, we elucidate the roles and effects of coexistent radiative and convective zones in the envelope of critical core mass. Based on the results, we discuss the relevance of Bondi and Hill surface conditions and explore the parameter dependences of critical core mass.

  7. Life Cycle Greenhouse Gas Emissions from Solar Photovoltaics (Fact Sheet)

    SciTech Connect

    Not Available

    2012-11-01

    The National Renewable Energy Laboratory (NREL) recently led the Life Cycle Assessment (LCA) Harmonization Project, a study that helps to clarify inconsistent and conflicting life cycle GHG emission estimates in the published literature and provide more precise estimates of life cycle GHG emissions from PV systems.

  8. Generation IV nuclear energy system initiative. Pin core subassembly designfor the Gas-Cooled Fast Reactor.

    SciTech Connect

    Farmer, M. T.; Hoffman, E. A.; Pfeiffer, P. F.; Therios, I. U.

    2006-07-31

    The Gas-Cooled Fast Reactor (GFR) is one of six systems selected for viability assessment in the Generation IV program. It features a closed nuclear fuel cycle, consisting of a high-temperature helium-cooled fast spectrum reactor, coupled to a direct-cycle helium turbine for electricity production. The GFR combines the advances of fast spectrum systems with those of high-temperature systems. It was clear from the very beginning that GFR design should be driven by the objective to offer a complementary approach to liquid metal cooling. On this basis, CEA and the US DOE decided to collaborate on the pre-conceptual design of a GFR. This reactor design will provide a high level of safety and full recycling of the actinides, and will also be highly proliferation resistant and economically attractive. The status of this collaborative project is that two unit sizes, 600 MWt and 2400 MWt were selected as the focus of the design and safety studies. Researchers studied fuel forms, fuel assembly/element designs, core configurations, primary and balance-of-plant layouts, and safety approaches for both of these unit sizes. Results regarding the feasibility of this GFR design are encouraging. For example, sustainability and non-proliferation goals can be met and the proposed concept has attractive safety features. These features take advantage of the helium in terms of its neutronic quasi-transparency as well as the enhanced Doppler effect in connection with candidate fuel and structural materials. The current design trend is to consider high unit power for the GFR (2400 MWt), an attractive level for the power density (100 MW/m{sup 3}), and the implementation of an innovative plate type fuel or pin type sub-assembly with carbide-based actinide compounds and SiC-based structural materials. Work is still needed to refine the safety approach, to select the main system options, and to more definitively establish economic parameters.

  9. Mass estimates for very cold (<8 K) gas in molecular cloud cores

    NASA Astrophysics Data System (ADS)

    Steinacker, J.; Linz, H.; Beuther, H.; Henning, Th.; Bacmann, A.

    2016-09-01

    Context. The mass of prestellar cores is an essential ingredient to understand the onset of star formation in the core. The low level of emission from cold dust may keep parts of this dust hidden from observation. Aims: We aim to determine the fraction of core mass in the temperature range <8 K that can be expected for typical low- and high-mass star formation regions. Methods: We calculated the dust temperature within standard spherically symmetric prestellar cores for a grid of density power laws in the outer core regions, core masses, and variations in the external multicomponent radiation field. We assume the dust is composed of amorphous silicate and carbon and we discuss variations of its optical properties. As a measure for the distribution of cores and clumps, we used core mass functions derived for various environments. In view of the high densities in very cold central regions, dust and gas temperatures are assumed to be equal. Results: We find that the fraction of mass with temperatures <8 K in typical low- and high-mass cores is <20%. It is possible to obtain higher fractions of very cold gas by placing intermediate- or high-mass cores in a typical low-mass star formation environment. We show that the mass uncertainty arising from far-infrared to mm modeling of very cold dust emission is smaller than the mass uncertainty owing to the unknown dust opacities. Conclusions: Under typical star formation conditions, dust with temperatures <8 K covers a small mass fraction in molecular cloud cores, but may play a more important role for special cases. The major unknown in determining the total core mass from thermal dust emission is the uncertainty in the dust opacity, not in the underestimated very cold dust mass.

  10. A thermodynamic review of cryogenic refrigeration cycles for liquefaction of natural gas

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung

    2015-12-01

    A thermodynamic review is presented on cryogenic refrigeration cycles for the liquefaction process of natural gas. The main purpose of this review is to examine the thermodynamic structure of various cycles and provide a theoretical basis for selecting a cycle in accordance with different needs and design criteria. Based on existing or proposed liquefaction processes, sixteen ideal cycles are selected and the optimal conditions to achieve their best thermodynamic performance are investigated. The selected cycles include standard and modified versions of Joule-Thomson (JT) cycle, Brayton cycle, and their combined cycle with pure refrigerants (PR) or mixed refrigerants (MR). Full details of the cycles are presented and discussed in terms of FOM (figure of merit) and thermodynamic irreversibility. In addition, a new method of nomenclature is proposed to clearly identify the structure of cycles by abbreviation.

  11. NOVEL GAS CLEANING/CONDITIONING FOR INTEGRATED GASIFICATION COMBINED CYCLE

    SciTech Connect

    Dennis A. Horazak; Richard A. Newby; Eugene E. Smeltzer; Rachid B. Slimane; P. Vann Bush; James L. Aderhold Jr; Bruce G. Bryan

    2005-12-01

    Development efforts have been underway for decades to replace dry-gas cleaning technology with humid-gas cleaning technology that would maintain the water vapor content in the raw gas by conducting cleaning at sufficiently high temperature to avoid water vapor condensation and would thus significantly simplify the plant and improve its thermal efficiency. Siemens Power Generation, Inc. conducted a program with the Gas Technology Institute (GTI) to develop a Novel Gas Cleaning process that uses a new type of gas-sorbent contactor, the ''filter-reactor''. The Filter-Reactor Novel Gas Cleaning process described and evaluated here is in its early stages of development and this evaluation is classified as conceptual. The commercial evaluations have been coupled with integrated Process Development Unit testing performed at a GTI coal gasifier test facility to demonstrate, at sub-scale the process performance capabilities. The commercial evaluations and Process Development Unit test results are presented in Volumes 1 and 2 of this report, respectively. Two gas cleaning applications with significantly differing gas cleaning requirements were considered in the evaluation: IGCC power generation, and Methanol Synthesis with electric power co-production. For the IGCC power generation application, two sets of gas cleaning requirements were applied, one representing the most stringent ''current'' gas cleaning requirements, and a second set representing possible, very stringent ''future'' gas cleaning requirements. Current gas cleaning requirements were used for Methanol Synthesis in the evaluation because these cleaning requirements represent the most stringent of cleaning requirements and the most challenging for the Filter-Reactor Novel Gas Cleaning process. The scope of the evaluation for each application was: (1) Select the configuration for the Filter-Reactor Novel Gas Cleaning Process, the arrangement of the individual gas cleaning stages, and the probable operating

  12. Optimized working conditions for a thermoelectric generator as a topping cycle for gas turbines

    NASA Astrophysics Data System (ADS)

    Brady Knowles, C.; Lee, Hohyun

    2012-10-01

    This paper presents a model for a theoretical maximum efficiency of a thermoelectric generator integrated with a Brayton-cycle engine. The thermoelectric cycle is presented in two configurations as a topping cycle and a preheating topping cycle. For the topping cycle configuration, the thermoelectric generator receives heat from a high-temperature heat source and produces electrical work before rejecting heat to a Brayton cycle. For the preheating topping cycle, the rejected heat from the thermoelectric generator partially heats the compressed working fluid of the Brayton cycle before a secondary heater delivers heat to the working fluid directly from the heat source. The thermoelectric topping cycle efficiency increases as the temperature difference between the hot- and cold-side increases; however, this limits the heat transfer possible to the Brayton cycle, which in turn reduces power generation from the Brayton cycle. This model identifies the optimum operating parameters of the thermoelectric and Brayton cycles to obtain the maximum thermal efficiency of the combined cycle. In both configurations, efficiency gains are larger at low-temperature Brayton cycles. Although a thermoelectric generator (TEG) topping cycle enhances efficiency for a low temperature turbine, efficiency cannot exceed a high temperature gas turbine. Using a TEG topping cycle is limited to cases when space or price for a high temperature turbine cannot be justified. A design to achieve the preheating thermoelectric topping cycle is also presented.

  13. Life Cycle GHG Emissions from Conventional Natural Gas Power Generation: Systematic Review and Harmonization (Presentation)

    SciTech Connect

    Heath, G.; O'Donoughue, P.; Whitaker, M.

    2012-12-01

    This research provides a systematic review and harmonization of the life cycle assessment (LCA) literature of electricity generated from conventionally produced natural gas. We focus on estimates of greenhouse gases (GHGs) emitted in the life cycle of electricity generation from conventionally produced natural gas in combustion turbines (NGCT) and combined-cycle (NGCC) systems. A process we term "harmonization" was employed to align several common system performance parameters and assumptions to better allow for cross-study comparisons, with the goal of clarifying central tendency and reducing variability in estimates of life cycle GHG emissions. This presentation summarizes preliminary results.

  14. A demonstration of a whole core neutron transport method in a gas cooled reactor

    SciTech Connect

    Connolly, K. J.; Rahnema, F.

    2013-07-01

    This paper illustrates a capability of the whole core transport method COMET. Building on previous works which demonstrated the accuracy of the method, this work serves to emphasize the robust capability of the method while also accentuating its efficiency. A set of core configurations is presented based on an operating gas-cooled thermal reactor, Japan's HTTR, and COMET determines the eigenvalue and fission density profile throughout each core configuration. Results for core multiplication factors are compared to MCNP for accuracy and also to compare runtimes. In all cases, the values given by COMET differ by those given by MCNP by less than the uncertainty inherent in the stochastic solution procedure, however, COMET requires runtimes shorter on the order of a few hundred. Figures are provided illustrating the whole core fission density profile, with segments of pins explicitly modeled individually, so that pin-level neutron flux behavior can be seen without any approximation due to simplification strategies such as homogenization. (authors)

  15. Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145

    NASA Technical Reports Server (NTRS)

    Markevitch, Maxim; Giacintucci, S.; Dallacasa, D.; Venturi, T.; Brunetti, G.; Cassano, R.; Athreya, R. M.; Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.

    2011-01-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based its unique multiwavelength morphology. Our X-ray analysis confirms the core gas is undergoing "sloshing" resulting from a prior, large scale, gravitational perturbation. In combination with extensive multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M=4.8+/-2.4 x 10(exp 14) Stellar Mass has previously (> or approx.=0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  16. Sloshing Gas in the Core of the Most Luminous Galaxy Cluster RXJ1347.5-1145

    NASA Technical Reports Server (NTRS)

    Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.; Markevitvh, Maxim

    2011-01-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based on its unique multiwavelength morphology. Our X-ray analysis confirms the core gas is undergoing "sloshing" resulting from a prior, large scale, gravitational perturbation. In combination with extensive multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M=4.8+/-2.4x10(exp 14) solar Mass has previously (> or approx.0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  17. Experimental Plans for Subsystems of a Shock Wave Driven Gas Core Reactor

    NASA Technical Reports Server (NTRS)

    Kazeminezhad, F.; Anghai, S.

    2008-01-01

    This Contractor Report proposes a number of plans for experiments on subsystems of a shock wave driven pulsed magnetic induction gas core reactor (PMI-GCR, or PMD-GCR pulsed magnet driven gas core reactor). Computer models of shock generation and collision in a large-scale PMI-GCR shock tube have been performed. Based upon the simulation results a number of issues arose that can only be addressed adequately by capturing experimental data on high pressure (approx.1 atmosphere or greater) partial plasma shock wave effects in large bore shock tubes ( 10 cm radius). There are three main subsystems that are of immediate interest (for appraisal of the concept viability). These are (1) the shock generation in a high pressure gas using either a plasma thruster or pulsed high magnetic field, (2) collision of MHD or gas dynamic shocks, their interaction time, and collision pile-up region thickness, and (3) magnetic flux compression power generation (not included here).

  18. SLOSHING GAS IN THE CORE OF THE MOST LUMINOUS GALAXY CLUSTER RXJ1347.5-1145

    SciTech Connect

    Johnson, Ryan E.; Zuhone, John; Jones, Christine; Forman, William R.; Markevitch, Maxim E-mail: cjf@cfa.harvard.edu E-mail: jzuhone@cfa.harvard.edu

    2012-06-01

    We present new constraints on the merger history of the most X-ray luminous cluster of galaxies, RXJ1347.5-1145, based on its unique multiwavelength morphology. Our X-ray analysis confirms that the core gas is undergoing 'sloshing' resulting from a prior, large-scale, gravitational perturbation. In combination with multiwavelength observations, the sloshing gas points to the primary and secondary clusters having had at least two prior strong gravitational interactions. The evidence supports a model in which the secondary subcluster with mass M = 4.8 {+-} 2.4 Multiplication-Sign 10{sup 14} M{sub Sun} has previously ({approx}>0.6 Gyr ago) passed by the primary cluster, and has now returned for a subsequent crossing where the subcluster's gas has been completely stripped from its dark matter halo. RXJ1347 is a prime example of how core gas sloshing may be used to constrain the merger histories of galaxy clusters through multiwavelength analyses.

  19. Design of intense 1.5-cycle pulses generation at 3.6 µm through a pressure gradient hollow-core fiber.

    PubMed

    Huang, Zhiyuan; Wang, Ding; Dai, Ye; Li, Yanyan; Guo, Xiaoyang; Li, Wenkai; Chen, Yun; Lu, Jun; Liu, Zhengzheng; Zhao, Ruirui; Leng, Yuxin

    2016-05-01

    We theoretically study the nonlinear compression of the 10-mJ, 62-fs, 3.6-µm laser pulses in an argon gas-filled hollow-core fiber with large diameter of 1000 µm. Using a pressure gradient to restrict undesirable nonlinear effect such as ionization, especially at the entrance, we obtain the intense 18.3-fs (~1.5 cycle) pulses at 3.6 µm only through compression with CaF2 crystal, which can be used as an ultrafast source for strong field driven experiments. In addition, we calculate and discuss the relation between optimal fiber length and coupling efficiency for a given bandwidth. These results are useful for the design of using hollow-core fiber to compress the high-energy pulses with long wavelength. PMID:27137543

  20. Preliminary Design Study of Medium Sized Gas Cooled Fast Reactor with Natural Uranium as Fuel Cycle Input

    NASA Astrophysics Data System (ADS)

    Meriyanti, Su'ud, Zaki; Rijal, K.; Zuhair, Ferhat, A.; Sekimoto, H.

    2010-06-01

    In this study a fesibility design study of medium sized (1000 MWt) gas cooled fast reactors which can utilize natural uranium as fuel cycle input has been conducted. Gas Cooled Fast Reactor (GFR) is among six types of Generation IV Nuclear Power Plants. GFR with its hard neuron spectrum is superior for closed fuel cycle, and its ability to be operated in high temperature (850° C) makes various options of utilizations become possible. To obtain the capability of consuming natural uranium as fuel cycle input, modified CANDLE burn-up scheme[1-6] is adopted this GFR system by dividing the core into 10 parts of equal volume axially. Due to the limitation of thermal hydraulic aspects, the average power density of the proposed design is selected about 70 W/cc. As an optimization results, a design of 1000 MWt reactors which can be operated 10 years without refueling and fuel shuffling and just need natural uranium as fuel cycle input is discussed. The average discharge burn-up is about 280 GWd/ton HM. Enough margin for criticallity was obtained for this reactor.

  1. Preliminary Design Study of Medium Sized Gas Cooled Fast Reactor with Natural Uranium as Fuel Cycle Input

    SciTech Connect

    Meriyanti; Su'ud, Zaki; Rijal, K.; Zuhair; Ferhat, A.; Sekimoto, H.

    2010-06-22

    In this study a feasibility design study of medium sized (1000 MWt) gas cooled fast reactors which can utilize natural uranium as fuel cycle input has been conducted. Gas Cooled Fast Reactor (GFR) is among six types of Generation IV Nuclear Power Plants. GFR with its hard neuron spectrum is superior for closed fuel cycle, and its ability to be operated in high temperature (850 deg. C) makes various options of utilizations become possible. To obtain the capability of consuming natural uranium as fuel cycle input, modified CANDLE burn-up scheme[1-6] is adopted this GFR system by dividing the core into 10 parts of equal volume axially. Due to the limitation of thermal hydraulic aspects, the average power density of the proposed design is selected about 70 W/cc. As an optimization results, a design of 1000 MWt reactors which can be operated 10 years without refueling and fuel shuffling and just need natural uranium as fuel cycle input is discussed. The average discharge burn-up is about 280 GWd/ton HM. Enough margin for criticality was obtained for this reactor.

  2. Implications of low natural gas prices on life cycle greenhouse gas emissions in the U.S. electricity sector

    NASA Astrophysics Data System (ADS)

    Jaramillo, P.; Venkatesh, A.; Griffin, M.; Matthews, S.

    2012-12-01

    Increased production of unconventional natural gas resources in the U.S. has drastically reduced the price of natural gas. While in 2005 prices went above 10/MMBtu, since 2011 they have been below 3/MMBtu. These low prices have encouraged the increase of natural gas utilization in the United States electricity sector. Natural gas can offset coal for power generation, reducing emissions such as greenhouse gases, sulfur and nitrogen oxides. In quantifying the benefit of offsetting coal by using natural gas, life cycle assessment (LCA) studies have shown up to 50% reductions in life cycle greenhouse gas (GHG) emissions can be expected. However, these studies predominantly use limited system boundaries that contain single individual coal and natural gas power plants. They do not consider (regional) fleets of power plants that are dispatched on the basis of their short-run marginal costs. In this study, simplified economic dispatch models (representing existing power plants in a given region) are developed for three U.S. regions - ERCOT, MISO and PJM. These models, along with historical load data are used to determine how natural gas utilization will increase in the short-term due to changes in natural gas price. The associated changes in fuel mix and life cycle GHG emissions are estimated. Results indicate that life cycle GHG emissions may, at best, decrease by 5-15% as a result of low natural gas prices, compared to almost 50% reductions estimated by previous LCAs. This study thus provides more reasonable estimates of potential reductions in GHG emissions from using natural gas instead of coal in the electricity sector in the short-term.

  3. Survey of alternative gas turbine engine and cycle design. Final report

    SciTech Connect

    Lukas, H.

    1986-02-01

    In the period of the 1940's to 1960's much experimentation was performed in the areas of intercooling, reheat, and recuperation, as well as the use of low-grade fuels in gas turbines. The Electric Power Research Institute (EPRI), in an effort to document past experience which can be used as the basis for current design activities, commissioned a study to document alternate cycles and components used in gas turbine design. The study was performed by obtaining the important technical and operational criteria of the cycles through a literature search of published documents, articles, and papers. Where possible the information was augmented through dialogue with persons associated with those cycles and with the manufacturers. The survey indicated that many different variations of the simple open-cycle gas turbine plant were used. Many of these changes resulted in increases in efficiency over the low simple-cycle efficiency of that period. Metallurgy, as well as compressor and turbine design, limited the simple-cycle efficiency to the upper teens. The cycle modifications increased those efficiencies to the twenties and thirties. Advances in metallurgy as well as compressor and turbine design, coupled with the decrease in flue cost, stopped the development of these complex cycles. Many of the plants operated successfully for many years, and only because newer simple-cycle gas turbine plants and large steam plants had better heat rates were these units shutdown or put into stand-by service. 24 refs., 25 figs., 114 tabs.

  4. Advanced technology cogeneration system conceptual design study: Closed cycle gas turbines

    NASA Technical Reports Server (NTRS)

    Mock, E. A. T.; Daudet, H. C.

    1983-01-01

    The results of a three task study performed for the Department of Energy under the direction of the NASA Lewis Research Center are documented. The thermal and electrical energy requirements of three specific industrial plants were surveyed and cost records for the energies consumed were compiled. Preliminary coal fired atmospheric fluidized bed heated closed cycle gas turbine and steam turbine cogeneration system designs were developed for each industrial plant. Preliminary cost and return-on-equity values were calculated and the results compared. The best of the three sites was selected for more detailed design and evaluation of both closed cycle gas turbine and steam turbine cogeneration systems during Task II. Task III involved characterizing the industrial sector electrical and thermal loads for the 48 contiguous states, applying a family of closed cycle gas turbine and steam turbine cogeneration systems to these loads, and conducting a market penetration analysis of the closed cycle gas turbine cogeneration system.

  5. 40 CFR 86.110-94 - Exhaust gas sampling system; diesel-cycle vehicles, and Otto-cycle vehicles requiring particulate...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-cycle vehicles, and Otto-cycle vehicles requiring particulate emissions measurements. 86.110-94 Section... 1977 and Later Model Year New Light-Duty Vehicles and New Light-Duty Trucks and New Otto-Cycle Complete Heavy-Duty Vehicles; Test Procedures § 86.110-94 Exhaust gas sampling system; diesel-cycle vehicles,...

  6. 40 CFR 86.110-94 - Exhaust gas sampling system; diesel-cycle vehicles, and Otto-cycle vehicles requiring particulate...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-cycle vehicles, and Otto-cycle vehicles requiring particulate emissions measurements. 86.110-94 Section... 1977 and Later Model Year New Light-Duty Vehicles and New Light-Duty Trucks and New Otto-Cycle Complete Heavy-Duty Vehicles; Test Procedures § 86.110-94 Exhaust gas sampling system; diesel-cycle vehicles,...

  7. 40 CFR 86.110-94 - Exhaust gas sampling system; diesel-cycle vehicles, and Otto-cycle vehicles requiring particulate...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-cycle vehicles, and Otto-cycle vehicles requiring particulate emissions measurements. 86.110-94 Section... 1977 and Later Model Year New Light-Duty Vehicles and New Light-Duty Trucks and New Otto-Cycle Complete Heavy-Duty Vehicles; Test Procedures § 86.110-94 Exhaust gas sampling system; diesel-cycle vehicles,...

  8. Gas Metal Arc Welding and Flux-Cored Arc Welding. Teacher Edition. Second Edition.

    ERIC Educational Resources Information Center

    Fortney, Clarence; Gregory, Mike

    These instructional materials are designed to improve instruction in Gas Metal Arc Welding (GMAW) and Flux-Cored Arc Welding (FCAW). The following introductory information is included: use of this publication; competency profile; instructional/task analysis; related academic and workplace skills list; tools, materials, and equipment list; and…

  9. Photothermal effect in gas-filled hollow-core photonic bandgap fiber

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Jin, Wei; Cao, Yingchun; Ho, Hoi Lut

    2015-09-01

    We exploit photothermal effect in gas-filled hollow-core photonic bandgap fibers, and demonstrate remarkably sensitive all-fiber (acetylene) gas sensors with noise equivalent concentration of 1-3 parts-per-billion and an unprecedented dynamic range of nearly six orders of magnitude. These results are two to three orders of magnitude better than previous direct absorption-based optical fiber gas sensors. The realization of photothermal spectroscopy in fiber-optic format will allow a new class of sensors with ultra-sensitivity and selectivity, compact size, remote and multiplexed multi-point detection capability.

  10. Kinetic Temperatures of the Dense Gas Clumps in the Orion KL Molecular Core

    NASA Technical Reports Server (NTRS)

    Wang, Kuo-Song; Kuan, Yi-Jehng; Liu, Sheng-Yuan; Charnley, Steven B.

    2010-01-01

    High angular-resolution images of the J = 18(sub K)-17(sub K) emission of CH3CN in the Orion KL molecular core were observed with the Submillimeter Array (SMA). Our high-resolution observations clearly reveal that CH3CN emission originates mainly from the Orion Hot Core and the Compact Ridge, both within approximately 15 inches of the warm and dense part of Orion KL. The clumpy nature of the molecular gas in Orion KL can also be readily seen from our high-resolution SMA images. In addition, a semi-open cavity-like kinematic structure is evident at the location between the Hot Core and the Compact Ridge. We performed excitation analysis with the "population diagram" method toward the Hot Core, IRc7, and the northern part of the Compact Ridge. Our results disclose a non-uniform temperature structure on small scales in Orion KL, with a range of temperatures from 190-620 K in the Hot Core. Near the Compact Ridge, the temperatures are found to be 170-280 K. Comparable CH3CN fractional abundances of 10(exp -8) to 10(exp -7) are found around both in the Hot Core and the Compact Ridge. Such high abundances require that a hot gas phase chemistry, probably involving ammonia released from grain mantles, plays an important role in forming these CH3CN molecules.

  11. Studying the outflow-core interaction with ALMA Cycle 1 observations of the HH 46/47 molecular outflow

    NASA Astrophysics Data System (ADS)

    Zhang, Yichen; Arce, Hector G.; Mardones, Diego; Dunham, Michael; Garay, Guido; Noriega-Crespo, Alberto; Corder, Stuartt; Offner, Stella; Cabrit, Sylvie

    2016-01-01

    We present ALMA Cycle 1 observations of the HH 46/47 molecular outflow which is driven by a low-mass Class 0/I protostar. Previous ALMA Cycle 0 12CO observation showed outflow cavities produced by the entrainment of ambient gas by the protostellar jet and wide-angle wind. Here we present analysis of observation of 12CO, 13CO, C18O and other species using combined 12m array and ACA observations. The improved angular resolution and sensitivity allow us to detect details of the outflow structure. Specially, we see that the outflow cavity wall is composed of two or more layers of outflowing gas, which separately connect to different shocked regions along the outflow axis inside the cavity, suggesting the outflow cavity wall is composed of multiple shells entrained by a series of jet bow-shock events. The new 13CO and C18O data also allow us to trace relatively denser and slower outflow material than that traced by the 12CO. These species are only detected within about 1 to 2 km/s from the cloud velocity, tracing the outflow to lower velocities than what is possible using only the 12CO emission. Interestingly, the cavity wall of the red lobe appears at very low outflow velocities (as low as ~0.2 km/s). In addition, 13CO and C18O allow us to correct for the CO optical depth, allowing us to obtain more accurate estimates of the outflow mass, momentum and kinetic energy. Applying the optical depth correction significantly increases the previous mass estimate by a factor of 14. The outflow kinetic energy distribution shows that even though the red lobe is mainly entrained by jet bow-shocks, most of the outflow energy is being deposited into the cloud at the base of the outflow cavity rather than around the heads of the bow shocks. The estimated total mass, momentum, and energy of the outflow indicate that the outflow has the ability to disperse the parent core. We found possible evidence for a slowly moving rotating outflow in CS. Our 13CO and C18O observations also trace a

  12. An efficient multi-stage Brayton-JT cycle for liquefaction of natural gas

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Chung, Myung Jin; Lee, Sanggyu; Choe, Kun Hyung

    2011-06-01

    Combined multi-stage Brayton-JT refrigeration cycles are investigated as a governmental effort in Korea to develop an original liquefaction process of natural gas in accordance with recent demand of higher efficiency and larger capacity. Based upon thermodynamic optimization theory, a combined refrigeration system is proposed with nitrogen (N2) Brayton cycle, ethylene (C2) JT cycle, and propane (C3) JT cycles, which are used for cooling the feed gas in a series of heat exchangers. Since no mixed refrigerants are used, this system is simple in operation and robust in reliability. A complete cycle design is presented to confirm its feasibility and estimate the liquefaction performance. It is expected that the proposed N2-C2-C3 cycle could have a reasonably high efficiency and the potential of great liquefaction capacity. Next steps are underway for patent application and practical process development.

  13. Effect of steam addition on cycle performance of simple and recuperated gas turbines

    NASA Technical Reports Server (NTRS)

    Boyle, R. J.

    1979-01-01

    Results are presented for the cycle efficiency and specific power of simple and recuperated gas turbine cycles in which steam is generated and used to increase turbine flow. Calculations showed significant improvements in cycle efficiency and specific power by adding steam. The calculations were made using component efficiencies and loss assumptions typical of stationary powerplants. These results are presented for a range of operating temperatures and pressures. Relative heat exchanger size and the water use rate are also examined.

  14. Fuel containment and stability in the gas core nuclear rocket. Final report, April 15, 1993--April 14, 1994

    SciTech Connect

    Kammash, T.

    1996-02-01

    One of the most promising approaches to advanced propulsion that could meet the objectives of the Space Exploration Initiative (SEI) is the open cycle gas core nuclear rocket (GCR). The energy in this device is generated by a fissioning uranium plasma which heats, through radiation, a propellant that flows around the core and exits through a nozzle, thereby converting thermal energy into thrust. Although such a scheme can produce very attractive propulsion parameters in the form of high specific impulse and high thrust, it does suffer from serious physics and engineering problems that must be addressed if it is to become a viable propulsion system. Among the major problems that must be solved are the confinement of the uranium plasma, potential instabilities and control problems associated with the dynamics of the uranium core, and the question of startup and fueling of such a reactor. In this paper, the authors focus their attention on the problems of equilibria and stability of the uranium care, and examine the potential use of an externally applied magnetic field for these purposes. They find that steady state operation of the reactor is possible only for certain care profiles that may not be compatible with the radiative aspect of the system. The authors also find that the system is susceptible to hydrodynamic and acoustic instabilities that could deplete the uranium fuel in a short time if not properly suppressed.

  15. Long-slit spectroscopy of gas in the cores of X-ray luminous clusters

    NASA Technical Reports Server (NTRS)

    Hu, E. M.; Cowie, L. L.; Wang, Z.

    1985-01-01

    The results of long-slit spectroscopy obtained for the core regions of 14 clusters of galaxies are reported. The data are presented in detail. It is shown that the presence of optical emission is tied to the properties of the hot gas in the cluster and not to the morphology of the central galaxy or cluster, demonstrating that the optical systems are indeed formed by the cooling of hot gas. Cooling flows occur when the gas density exceeds a critical central value which corresponds to a cooling time scale which, it is argued, weakly favors low values of H(0). The kinematics of the gas flows are discussed. The excitation mechanisms, correlation of optical emission with radio properties, and upper limits on coronal line strengths from the hot gas are discussed.

  16. Numerical Research of Steam and Gas Plant Efficiency of Triple Cycle for Extreme North Regions

    NASA Astrophysics Data System (ADS)

    Galashov, Nikolay; Tsibulskii, Svjatoslav; Matveev, Aleksandr; Masjuk, Vladimir

    2016-02-01

    The present work shows that temperature decrease of heat rejection in a cycle is necessary for energy efficiency of steam turbine plants. Minimum temperature of heat rejection at steam turbine plant work on water steam is 15°C. Steam turbine plant of triple cycle where lower cycle of steam turbine plant is organic Rankine cycle on low-boiling substance with heat rejection in air condenser, which safely allows rejecting heat at condensation temperatures below 0°C, has been offered. Mathematical model of steam and gas plant of triple cycle, which allows conducting complex researches with change of working body appearance and parameters defining thermodynamic efficiency of cycles, has been developed. On the basis of the model a program of parameters and index cycles design of steam and gas plants has been developed in a package of electron tables Excel. Numerical studies of models showed that energy efficiency of steam turbine plants of triple cycle strongly depend on low-boiling substance type in a lower cycle. Energy efficiency of steam and gas plants net 60% higher can be received for steam and gas plants on the basis of gas turbine plant NK-36ST on pentane and its condensation temperature below 0°C. It was stated that energy efficiency of steam and gas plants net linearly depends on condensation temperature of low-boiling substance type and temperature of gases leaving reco very boiler. Energy efficiency increases by 1% at 10% decrease of condensation temperature of pentane, and it increases by 0.88% at 15°C temperature decrease of gases leaving recovery boiler.

  17. Investigation on Carbon-Deposition Behavior from Heating Cycle Gas in Oxygen Blast Furnace Process

    NASA Astrophysics Data System (ADS)

    Liu, Jinzhou; Wang, Jingsong; She, Xuefeng; Zhang, Shiyang; Xue, Qingguo

    2015-02-01

    Among the different ways to study carbon deposition in the ironmaking process, not much attention was paid to that of heating the gas mixture, especially cycle gas in an oxygen blast furnace. In this work, the carbon-deposition characteristics of heating 100 pct CO, CO-H2 gas mixture, and cycle gas in the oxygen blast furnace process were, respectively, experimentally and theoretically investigated. First, the thermodynamics on carbon-deposition reactions were calculated. Then, the impacts of discharging operation temperature, the proportion of CO/H2 in heating the CO-H2 gas mixture, and the CO2 concentration in heating the cycle gas of an oxygen blast furnace on the carbon deposition were tested and investigated. Furthermore, the carbon-deposition behaviors in heating the CO-H2 gas mixture were compared with the thermodynamic calculation results for discussing the role of H2. In addition, carbon deposition in heating cycle gas includes CO decomposition and a carbon-deposition reaction by hybrid of CO and H2; the possible roles of each were analyzed by comparing thermodynamic calculation and experimental results. The deposited carbon was characterized by scanning electron microscope (SEM) to analyze the deposited carbon microstructure.

  18. Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactor

    SciTech Connect

    Chang Oh

    2004-07-01

    The Idaho National Engineering and Environmental Laboratory (INEEL) is investigating a Brayton cycle efficiency improvement on a high temperature gas-cooled reactor (HTGR) as part of Generation-IV nuclear engineering research initiative. In this project, we are investigating helium Brayton cycles for the secondary side of an indirect energy conversion system. Ultimately we will investigate the improvement of the Brayton cycle using other fluids, such as supercritical carbon dioxide. Prior to the cycle improvement study, we established a number of baseline cases for the helium indirect Brayton cycle. These cases look at both single-shaft and multiple-shaft turbomachinary. The baseline cases are based on a 250 MW thermal pebble bed HTGR. The results from this study are applicable to other reactor concepts such as a very high temperature gas-cooled reactor (VHTR), fast gas-cooled reactor (FGR), supercritical water reactor (SWR), and others. In this study, we are using the HYSYS computer code for optimization of the helium Brayton cycle. Besides the HYSYS process optimization, we performed parametric study to see the effect of important parameters on the cycle efficiency. For these parametric calculations, we use a cycle efficiency model that was developed based on the Visual Basic computer language. As a part of this study we are currently investigated single-shaft vs. multiple shaft arrangement for cycle efficiency and comparison, which will be published in the next paper.The ultimate goal of this study is to use supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency to values great than that of the helium Brayton cycle. This paper includes preliminary calculations of the steady state overall Brayton cycle efficiency based on the pebble bed reactor reference design (helium used as the working fluid) and compares those results with an initial calculation of a CO2 Brayton cycle.

  19. Comparison of intergrated coal gasification combined cycle power plants with current and advanced gas turbines

    SciTech Connect

    Banda, B.M.; Evans, T.F.; McCone, A.I.; Westisik, J.H.

    1984-08-01

    Two recent conceptual design studies examined ''grass roots'' integrated gasification-combined cycle (IGCC) plants for the Albany Station site of Niagara Mohawk Power Corporation. One of these studies was based on the Texaco Gasifier and the other was developed around the British Gas Co.-Lurgi slagging gasifier. Both gasifiers were operated in the ''oxygen-blown'' mode, producing medium Btu fuel gas. The studies also evaluated plant performance with both current and advanced gas turbines. Coalto-busbar efficiencies of approximately 35 percent were calculated for Texaco IGCC plants using current technology gas turbines. Efficiencies of approximately 39 percent were obtained for the same plant when using advanced technology gas turbines.

  20. Gas exchange in seawater with special emphasis on open-cycle ocean thermal energy conversion

    SciTech Connect

    Zapka, M.J.

    1988-01-01

    This study examined gas-transfer characteristics of seawater. Special emphasis is on gas-transfer processes in connection with Open-Cycle Ocean Thermal Energy Conversion (OC-OTEC) applications. Experiments probed the mechanism regulating gas transfer in bubbles and in a packed column. In order to compare gas transfer in seawater with extensively documented transfer characteristics of fresh water, all tests were conducted using both seawater and fresh water in the same experimental setting. Ten main findings are listed and briefly discussed. With appropriate system conditions, an approximately 85% removal of dissolved gas from the OC-OTEC feed stream appears to be feasible.

  1. AFB/open cycle gas turbine conceptual design study

    NASA Technical Reports Server (NTRS)

    Dickinson, T. W.; Tashjian, R.

    1983-01-01

    Applications of coal fired atmospheric fluidized bed gas turbine systems in industrial cogeneration are identified. Based on site-specific conceptual designs, the potential benefits of the AFB/gas turbine system were compared with an atmospheric fluidized design steam boiler/steam turbine system. The application of these cogeneration systems at four industrial plant sites is reviewed. A performance and benefit analysis was made along with a study of the representativeness of the sites both in regard to their own industry and compared to industry as a whole. A site was selected for the conceptual design, which included detailed site definition, AFB/gas turbine and AFB/steam turbine cogeneration system designs, detailed cost estimates, and comparative performance and benefit analysis. Market and benefit analyses identified the potential market penetration for the cogeneration technologies and quantified the potential benefits.

  2. Advanced Multi-Effect Distillation System for Desalination Using Waste Heat fromGas Brayton Cycles

    SciTech Connect

    Haihua Zhao; Per F. Peterson

    2012-10-01

    Generation IV high temperature reactor systems use closed gas Brayton Cycles to realize high thermal efficiency in the range of 40% to 60%. The waste heat is removed through coolers by water at substantially greater average temperature than in conventional Rankine steam cycles. This paper introduces an innovative Advanced Multi-Effect Distillation (AMED) design that can enable the production of substantial quantities of low-cost desalinated water using waste heat from closed gas Brayton cycles. A reference AMED design configuration, optimization models, and simplified economics analysis are presented. By using an AMED distillation system the waste heat from closed gas Brayton cycles can be fully utilized to desalinate brackish water and seawater without affecting the cycle thermal efficiency. Analysis shows that cogeneration of electricity and desalinated water can increase net revenues for several Brayton cycles while generating large quantities of potable water. The AMED combining with closed gas Brayton cycles could significantly improve the sustainability and economics of Generation IV high temperature reactors.

  3. Role of the interfaces in multiple networked one-dimensional core-shell nanostructured gas sensors.

    PubMed

    Park, Sunghoon; Ko, Hyunsung; Kim, Soohyun; Lee, Chongmu

    2014-06-25

    This study examined the gas sensing mechanism of multiple networked core-shell nanowire sensors. The ethanol gas sensing properties of In2O3/ZnO core-shell nanowires synthesized by the thermal evaporation of indium powder in an oxidizing atmosphere followed by the atomic layer deposition of ZnO were examined as an example. The pristine In2O3 nanowires and In2O3-core/ZnO-shell nanowires exhibited responses of ∼30% and ∼196%, respectively, to 1000 ppm ethanol at 300 °C. The response of the core-shell nanostructures to ethanol also showed a strong dependence on the shell layer width. The strongest response to ethanol was obtained with a shell layer thickness of ∼44 nm corresponding to 2λD, where λD is the Debye length of ZnO. The enhanced sensing properties of the core-shell nanowires toward ethanol can be explained based on the potential barrier-controlled carrier transport model combined with the surface depletion model; the former is predominant over the latter. PMID:24850501

  4. Life cycle greenhouse gas impacts of grassland management practice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biomass from conservation and dedicated grasslands could be an important feedstock for biofuels. Estimating the carbon (C) intensity of biofuel production pathways is important in order to meet greenhouse gas (GHG) targets set by government policy. Management decisions made during feedstock producti...

  5. The MS6001FA gas turbine in mid-size combined cycle and cogeneration applications

    SciTech Connect

    Ruegger, W.A.; Anderson, R.O.

    1994-12-31

    The MS6001FA gas turbine is the latest addition to the F-technology family of gas turbines. The design is based on an aerodynamic scaling of the proven MS7001FA and MS9001FA products and is available in both 50 and 60 Hz configurations. As a result of its higher F-technology firing temperature, the 6FA is ideally suited for combined cycle and other heat recovery applications where its performance represents a significant improvement over previously available mid-size gas turbines. This paper describes the basic design of the MS6001FA, including its auxiliary systems. The gas turbine`s performance in simple cycle, combined cycle, repowering, and cogeneration applications is also reviewed.

  6. Analysis of operation of the gas turbine in a poligeneration combined cycle

    NASA Astrophysics Data System (ADS)

    Bartela, Łukasz; Kotowicz, Janusz

    2013-12-01

    In the paper the results of analysis of an integrated gasification combined cycle IGCC polygeneration system, of which the task is to produce both electricity and synthesis gas, are shown. Assuming the structure of the system and the power rating of a combined cycle, the consumption of the synthesis gas for chemical production makes it necessary to supplement the lack of synthesis gas used for electricity production with the natural gas. As a result a change of the composition of the fuel gas supplied to the gas turbine occurs. In the paper the influence of the change of gas composition on the gas turbine characteristics is shown. In the calculations of the gas turbine the own computational algorithm was used. During the study the influence of the change of composition of gaseous fuel on the characteristic quantities was examined. The calculations were realized for different cases of cooling of the gas turbine expander's blades (constant cooling air mass flow, constant cooling air index, constant temperature of blade material). Subsequently, the influence of the degree of integration of the gas turbine with the air separation unit on the main characteristics was analyzed.

  7. Enhanced ethanol gas sensing properties of SnO₂-core/ZnO-shell nanostructures.

    PubMed

    Tharsika, T; Haseeb, A S M A; Akbar, Sheikh A; Sabri, Mohd Faizul Mohd; Hoong, Wong Yew

    2014-01-01

    An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ~5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures. PMID:25116903

  8. Enhanced Ethanol Gas Sensing Properties of SnO2-Core/ZnO-Shell Nanostructures

    PubMed Central

    Tharsika, T.; Haseeb, A. S. M. A.; Akbar, Sheikh A.; Sabri, Mohd Faizul Mohd; Hoong, Wong Yew

    2014-01-01

    An inexpensive single-step carbon-assisted thermal evaporation method for the growth of SnO2-core/ZnO-shell nanostructures is described, and the ethanol sensing properties are presented. The structure and phases of the grown nanostructures are investigated by field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. XRD analysis indicates that the core-shell nanostructures have good crystallinity. At a lower growth duration of 15 min, only SnO2 nanowires with a rectangular cross-section are observed, while the ZnO shell is observed when the growth time is increased to 30 min. Core-shell hierarchical nanostructures are present for a growth time exceeding 60 min. The growth mechanism for SnO2-core/ZnO-shell nanowires and hierarchical nanostructures are also discussed. The sensitivity of the synthesized SnO2-core/ZnO-shell nanostructures towards ethanol sensing is investigated. Results show that the SnO2-core/ZnO-shell nanostructures deposited at 90 min exhibit enhanced sensitivity to ethanol. The sensitivity of SnO2-core/ZnO-shell nanostructures towards 20 ppm ethanol gas at 400 °C is about ∼5-times that of SnO2 nanowires. This improvement in ethanol gas response is attributed to high active sensing sites and the synergistic effect of the encapsulation of SnO2 by ZnO nanostructures. PMID:25116903

  9. Core materials development for the fuel cycle R&D program

    NASA Astrophysics Data System (ADS)

    Maloy, S. A.; Toloczko, M.; Cole, J.; Byun, T. S.

    2011-08-01

    The Fuel Cycle Research and Development program is investigating methods of burning minor actinides in a transmutation fuel. One of the challenges of achieving this goal is to develop fuels capable of reaching extreme burnup levels (e.g. 40%). To achieve such high burnup levels' fast reactor core materials (cladding and duct) must be able to withstand very high doses (>300 dpa design goal) while in contact with the coolant and the fuel. Thus, these materials must withstand radiation effects that promote low temperature embrittlement, radiation induced segregation, high temperature helium embrittlement, swelling, accelerated creep, corrosion with the coolant, and chemical interaction with the fuel (FCCI). To develop and qualify materials to a total fluence greater than 200 dpa requires development of advanced alloys and irradiations in fast reactors to test these alloys. Test specimens of ferritic/martensitic alloys (T91/HT-9) previously irradiated in the FFTF reactor up to 210 dpa at a temperature range of 350-750 °C are presently being tested. This includes analysis of a duct made of HT-9 after irradiation to a total dose of 155 dpa at temperatures from 370 to 510 °C. Compact tension, charpy and tensile specimens have been machined from this duct and mechanical testing as well as SANS and Mossbauer spectroscopy are currently being performed. Initial results from compression testing and Charpy testing reveal a strong increase in yield stress (˜400 MPa) and a large increase in DBTT (up to 230 °C) for specimens irradiated at 383 °C to a dose of 28 dpa. Less hardening and a smaller increase in DBTT was observed for specimens irradiated at higher temperatures up to 500 °C. Advanced radiation tolerant materials are also being developed to enable the desired extreme fuel burnup levels. Specifically, coatings are being developed to minimize FCCI, and research is underway to fabricate large heats of radiation tolerant oxide dispersion steels with homogeneous oxide

  10. Core Materials Development for the Fuel Cycle R&D Program

    SciTech Connect

    S. A. Maloy; M. Toloczko; J. Cole; T. S. Byun

    2011-08-01

    The Fuel Cycle Research and Development program is investigating methods of burning minor actinides in a transmutation fuel. One of the challenges of achieving this goal is to develop fuels capable of reaching extreme burnup levels (e.g. 40%). To achieve such high burnup levels fast reactor core materials (cladding and duct) must be able to withstand very high doses (greater than 300 dpa design goal) while in contact with the coolant and the fuel. Thus, these materials must withstand radiation effects that promote low temperature embrittlement, radiation induced segregation, high temperature helium embrittlement, swelling, accelerated creep, corrosion with the coolant, and chemical interaction with the fuel (FCCI). To develop and qualify materials to a total fluence greater than 200 dpa requires development of advanced alloys and irradiations in fast reactors to test these alloys. Test specimens of ferritic/martensitic alloys (T91/HT-9) previously irradiated in the FFTF reactor up to 210 dpa at a temperature range of 350-750 C are presently being tested. This includes analysis of a duct made of HT-9 after irradiation to a total dose of 155 dpa at temperatures from 370 to 510 C. Compact tension, charpy and tensile specimens have been machined from this duct and mechanical testing as well as SANS and Mossbauer spectroscopy are currently being performed. Initial results from compression testing and Charpy testing reveal a strong increase in yield stress ({approx}400 MPa) and a large increase in DBTT (up to 230 C) for specimens irradiated at 383 C to a dose of 28 dpa. Less hardening and a smaller increase in DBTT was observed for specimens irradiated at higher temperatures up to 500 C. Advanced radiation tolerant materials are also being developed to enable the desired extreme fuel burnup levels. Specifically, coatings are being developed to minimize FCCI, and research is underway to fabricate large heats of radiation tolerant oxide dispersion steels with homogeneous

  11. Core materials development for the fuel cycle R&D program

    SciTech Connect

    Toloczko, M; Maloy, S; Cole, James I.; Byun, Thak Sang

    2011-01-01

    The Fuel Cycle Research and Development program is investigating methods of burning minor actinides in a transmutation fuel. One of the challenges of achieving this goal is to develop fuels capable of reaching extreme burnup levels (e.g. 40%). To achieve such high burnup levels fast reactor core materials (cladding and duct) must be able to withstand very high doses (>300 dpa design goal) while in contact with the coolant and the fuel. Thus, these materials must withstand radiation effects that promote low temperature embrittlement, radiation induced segregation, high temperature helium embrittlement, swelling, accelerated creep, corrosion with the coolant, and chemical interaction with the fuel (FCCI). To develop and qualify materials to a total fluence greater than 200 dpa requires development of advanced alloys and irradiations in fast reactors to test these alloys. Test specimens of ferritic/martensitic alloys (T91/HT-9) previously irradiated in the FFTF reactor up to 210 dpa at a temperature range of 350 750 C are presently being tested. This includes analysis of a duct made of HT-9 after irradiation to a total dose of 155 dpa at temperatures from 370 to 510 C. Compact tension, charpy and tensile specimens have been machined from this duct and mechanical testing as well as SANS and Mossbauer spectroscopy are currently being performed. Initial results from compression testing and Charpy testing reveal a strong increase in yield stress (400 MPa) and a large increase in DBTT (up to 230 C) for specimens irradiated at 383 C to a dose of 28 dpa. Less hardening and a smaller increase in DBTT was observed for specimens irradiated at higher temperatures up to 500 C. Advanced radiation tolerant materials are also being developed to enable the desired extreme fuel burnup levels. Specifically, coatings are being developed to minimize FCCI, and research is underway to fabricate large heats of radiation tolerant oxide dispersion steels with homogeneous oxide dispersions.

  12. Core materials development for the fuel cycle R&D program

    SciTech Connect

    Maloy, S. A.; Toloczko, Mychailo B.; Cole, J. I.; Byun, Thak Sang

    2011-12-31

    The Fuel Cycle Research and Development program is investigating methods of burning minor actinides in a transmutation fuel. One of the challenges of achieving this goal is to develop fuels capable of reaching extreme burnup levels (e.g. 40%). To achieve such high burnup levels’ fast reactor core materials (cladding and duct) must be able to withstand very high doses (>300 dpa design goal) while in contact with the coolant and the fuel. Thus, these materials must withstand radiation effects that promote low temperature embrittlement, radiation induced segregation, high temperature helium embrittlement, swelling, accelerated creep, corrosion with the coolant, and chemical interaction with the fuel (FCCI). To develop and qualify materials to a total fluence greater than 200 dpa requires development of advanced alloys and irradiations in fast reactors to test these alloys. Test specimens of ferritic/martensitic alloys (T91/HT-9) previously irradiated in the FFTF reactor up to 210 dpa at a temperature range of 350– 750 °C are presently being tested. This includes analysis of a duct made of HT-9 after irradiation to a total dose of 155 dpa at temperatures from 370 to 510 °C. Compact tension, charpy and tensile specimens have been machined from this duct and mechanical testing as well as SANS and Mossbauer spectroscopy are currently being performed. Initial results from compression testing and Charpy testing reveal a strong increase in yield stress (~400 MPa) and a large increase in DBTT (up to 230 °C) for specimens irradiated at 383 °C to a dose of 28 dpa. Less hardening and a smaller increase in DBTT was observed for specimens irradiated at higher temperatures up to 500 °C. Advanced radiation tolerant materials are also being developed to enable the desired extreme fuel burnup levels. Specifically, coatings are being developed to minimize FCCI, and research is underway to fabricate large heats of radiation tolerant oxide dispersion steels with homogeneous

  13. Small-scale AFBC hot air gas turbine power cycle

    SciTech Connect

    Ashworth, R.A.; Keener, H.M.; Hall, A.W.

    1995-12-31

    The Energy and Environmental Research Corporation (EER), the Ohio Agricultural Research and Development Center (OARDC), the Will-Burt Company (W-B) and the US Department of Energy (DOE) have successfully developed and completed pilot plant tests on a small scale atmospheric fluidized bed combustion (AFBC) system. This system can be used to generate electricity, and/or hot water, steam. Following successful pilot plant operation, commercial demonstration will take place at Cedar Lane Farms (CLF), near Wooster, Ohio. The system demonstration will be completed by the end of 1995. The project is being funded through a cooperative effort between the DOE, EER, W-B, OARDC, CLF and the Ohio Coal Development Office (OCDO). The small scale AFBC, has no internal heat transfer surfaces in the fluid bed proper. Combining the combustor with a hot air gas turbine (HAGT) for electrical power generation, can give a relatively high overall system thermal efficiency. Using a novel method of recovering waste heat from the gas turbine, a gross heat rate of 13,500 Btu/kWhr ({approximately}25% efficiency) can be achieved for a small 1.5 MW{sub e} plant. A low technology industrial recuperation type gas turbine is used that operates with an inlet blade temperature of 1,450 F and a compression ratio of 3.9:1. The AFBC-HAGT technology can be used to generate power for remote rural communities to replace diesel generators, or can be used for small industrial co-generation applications.

  14. The Core as the Third Pivotal End Member of the Earth's Plate Tectonic Cycle: A New Theory

    NASA Astrophysics Data System (ADS)

    Carman, J. H.

    2005-05-01

    Existing data and use of a hypothetical model, post-Stishovite-Magnesiowustite-Iron, indicate that the Earth's core could be the the convertor end member of the Earth's Plate Tectonic Cycle (EPTC): a new theory. This third pivitol end member, the core, is the place where the cycle begins and ends, to begin again. The first pivotal end member of the EPTC, for a three end member system, is the global MORB end member where new oceanic crust and lithosphere are created. Sea-floor spreading connects it to the second end member, the subduction end member, where oceanic crust and lithosphere disappear to become cold lithospheric-crust complexes descending through the mantle toward the Earth's core. When complexes break into it they are slowed, turned and endothermally ingested. Partial melting frees lower mantle phases and iron while forming metallic liquid and a densified immiscible silicate liquid, of which 17 vol.% reduces the bulk density of a convecting outer core by 10 %. Freed crystalline phases form micro-phases of micrometer to millimeter in size that more or less fill mega-bodies of <83 vol.% metallic liquid and <17 vol.% immiscible silicate liquid, both of centimeters to kilometers in size. Excess core energy starting each cycle comes mainly from irreversible exothermal reactions at numerous unstable phase contacts by stable phases within and between mega-bodies to yield stable products of lower Gibbs free energy, only to make new contacts and react...and react again. Other sources of exothermal energy come from radioactive silicate liquid and friction at stable phase contacts during mega-body convection. Heat accumulated from these energy sources tends to expand the outer core as univariant boundary reactions of the core and the lower mantle reverse, with +5.0 cm3g-1comming from the inner core boundary reaction alone. The outer core's pervasive expansion against the passively resisting strength of the mantle results in explosive ejection of silicate liquid

  15. Combined Brayton-JT cycles with refrigerants for natural gas liquefaction

    NASA Astrophysics Data System (ADS)

    Chang, Ho-Myung; Park, Jae Hoon; Lee, Sanggyu; Choe, Kun Hyung

    2012-06-01

    Thermodynamic cycles for natural gas liquefaction with single-component refrigerants are investigated under a governmental project in Korea, aiming at new processes to meet the requirements on high efficiency, large capacity, and simple equipment. Based upon the optimization theory recently published by the present authors, it is proposed to replace the methane-JT cycle in conventional cascade process with a nitrogen-Brayton cycle. A variety of systems to combine nitrogen-Brayton, ethane-JT and propane-JT cycles are simulated with Aspen HYSYS and quantitatively compared in terms of thermodynamic efficiency, flow rate of refrigerants, and estimated size of heat exchangers. A specific Brayton-JT cycle is suggested with detailed thermodynamic data for further process development. The suggested cycle is expected to be more efficient and simpler than the existing cascade process, while still taking advantage of easy and robust operation with single-component refrigerants.

  16. Estimating soil carbon change and biofuel life-cycle greenhouse gas emissions with economic, ecosystem and life-cycle models

    NASA Astrophysics Data System (ADS)

    Qin, Z.; Dunn, J.; Kwon, H. Y.; Mueller, S.; Wander, M.

    2015-12-01

    Land-use change (LUC) resulting from biofuel feedstock production can alter soil organic carbon (SOC) stocks of lands producing those crops and the crops they displace, possibly resulting in greenhouse gas (GHG) emissions. LUC GHG emissions included in biofuel life cycle analysis (LCA) have at times been estimated to be so great that biofuels did not offer a greenhouse gas reduction compared to conventional fossil fuels. To improve the accuracy of emissions estimates, SOC changes must be considered at a finer spatial resolution and take into account climate, soil, land use and management factors. This study reports on the incorporation of global LUC as predicted by a computable general equilibrium model (i.e., GTAP) and spatially-explicit modeled SOC estimates (using surrogate CENTURY) for various biofuel feedstock scenarios into a widely-used LCA model (i.e., GREET). Resulting estimates suggest: SOC changes associated with domestic corn production might contribute 2-6% or offset as much as 5% of total corn ethanol life-cycle GHG emissions. On the other hand, domestic LUC GHG emissions for switchgrass ethanol have the potential offset up to 60% of GHG emissions in the fuel's life cycle. Further, large SOC sequestration is predicted for Miscanthus feedstock production, enabling Miscanthus-based ethanol systems to offset all life-cycle GHG emissions and create a net carbon sink. LUC GHG emissions for ethanol derived from corn stover are small compared to other sources. Total life-cycle GHG emissions (g CO2eq MJ-1, 100cm soil) were estimated to be 59-66 for corn ethanol, 14 for stover ethanol, 18-26 for switchgrass ethanol, and -7 - -0.6 for Miscanthus ethanol.

  17. Formation of TiC-core, Graphitic-mantle Grains from CO Gas

    NASA Technical Reports Server (NTRS)

    Kimura, Yuki; Nuth, Joseph A., III; Ferguson, Frank T.

    2005-01-01

    We demonstrate a new formation route for TiC-core, graphitic-mantle spherules that does not require c-atom addition and the very long timescales associated with such growth (Bernatowicz et al. 1996). Carbonaceous materials can also be formed from C2H2 and its derivatives, as well as from CO gas. In this paper, we will demonstrate that large cage structure carbon particles can be produced from CO gas by the Boudouard reaction. Since the sublimation temperature for such fullerenes is low, the large cages can be deposited onto previously-nucleated TiC and produce TiC-core, graphitic-mantle spherules. New constraints for the formation conditions and the timescale for the formation of TiC-core, graphitic-mantle spherules are suggested by the results of this study. In particular, TiC-core, graphitic-mantle grains found in primitive meteorites that have never experienced hydration could be mantled by fullerenes or carbon nanotubes rather than by graphite. In situ observations of these grains in primitive anhydrous meteoritic matrix could confirm or refute this prediction and would demonstrate that the graphitic mantle on such grains is a metamorphic feature due to interaction of the pre-solar fullerenes with water within the meteorite matrix.

  18. Compact, stable and efficient all-fibre gas cells using hollow-core photonic crystal fibres

    NASA Astrophysics Data System (ADS)

    Benabid, F.; Couny, F.; Knight, J. C.; Birks, T. A.; Russell, P. St J.

    2005-03-01

    Gas-phase materials are used in a variety of laser-based applications-for example, in high-precision frequency measurement, quantum optics and nonlinear optics. Their full potential has however not been realized because of the lack of a suitable technology for creating gas cells that can guide light over long lengths in a single transverse mode while still offering a high level of integration in a practical and compact set-up or device. As a result, solid-phase materials are still often favoured, even when their performance compares unfavourably with gas-phase systems. Here we report the development of all-fibre gas cells that meet these challenges. Our structures are based on gas-filled hollow-core photonic crystal fibres, in which we have recently demonstrated substantially enhanced stimulated Raman scattering, and which exhibit high performance, excellent long-term pressure stability and ease of use. To illustrate the practical potential of these structures, we report two different devices: a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-continuous-wave laser pulses; and acetylene-filled cells, which we use for absolute frequency-locking of diode lasers with very high signal-to-noise ratios. The stable performance of these compact gas-phase devices could permit, for example, gas-phase laser devices incorporated in a `credit card' or even in a laser pointer.

  19. Analysis of core samples from the BPXA-DOE-USGS Mount Elbert gas hydrate stratigraphic test well: Insights into core disturbance and handling

    SciTech Connect

    Kneafsey, Timothy J.; Lu, Hailong; Winters, William; Boswell, Ray; Hunter, Robert; Collett, Timothy S.

    2009-09-01

    Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented.

  20. Effect on combined cycle efficiency of stack gas temperature constraints to avoid acid corrosion

    NASA Technical Reports Server (NTRS)

    Nainiger, J. J.

    1980-01-01

    To avoid condensation of sulfuric acid in the gas turbine exhaust when burning fuel oils contaning sulfur, the exhaust stack temperature and cold-end heat exchanger surfaces must be kept above the condensation temperature. Raising the exhaust stack temperature, however, results in lower combined cycle efficiency compared to that achievable by a combined cycle burning a sulfur-free fuel. The maximum difference in efficiency between the use of sulfur-free and fuels containing 0.8 percent sulfur is found to be less than one percentage point. The effect of using a ceramic thermal barrier coating (TBC) and a fuel containing sulfur is also evaluated. The combined-cycle efficiency gain using a TBC with a fuel containing sulfur compared to a sulfur-free fuel without TBC is 0.6 to 1.0 percentage points with air-cooled gas turbines and 1.6 to 1.8 percentage points with water-cooled gas turbines.

  1. Fe@Fe2O3 core-shell nanowires enhanced Fenton oxidation by accelerating the Fe(III)/Fe(II) cycles.

    PubMed

    Shi, Jingu; Ai, Zhihui; Zhang, Lizhi

    2014-08-01

    In this study we demonstrate Fe@Fe2O3 core-shell nanowires can improve Fenton oxidation efficiency by two times with rhodamine B as a model pollutant at pH > 4. Active species trapping experiments revealed that the rhodamine B oxidation enhancement was attributed to molecular oxygen activation induced by Fe@Fe2O3 core-shell nanowires. The molecular oxygen activation process could generate superoxide radicals to assist iron core for the reduction of ferric ions to accelerate the Fe(III)/Fe(II) cycles, which favored the H2O2 decomposition to produce more hydroxyl radicals for the rhodamine B oxidation. The combination of Fe@Fe2O3 core-shell nanowires and ferrous ions (Fe@Fe2O3/Fe(2+)) offered a superior Fenton catalyst to decompose H2O2 for producing OH. We employed benzoic acid as a probe reagent to check the generation of OH and found the OH generation rate of Fe@Fe2O3/Fe(2+) was 2-4 orders of magnitude larger than those of commonly used iron based Fenton catalysts and 38 times that of Fe(2+). The reusability and the stability of Fe@Fe2O3 core-shell nanowires were studied. Total organic carbon and ion chromatography analyses revealed the mineralization of rhodamine B and the releasing of nitrate ions. Gas chromatograph-mass spectrometry was used to investigate the degradation intermediates to propose the possible rhodamine B Fenton oxidation pathway in the presence of Fe@Fe2O3 nanowires. This study not only provides a new Fenton oxidation system for pollutant control, but also widen the application of molecular oxygen activation induced by nanoscale zero valent iron. PMID:24793112

  2. Soliton delivery of few-cycle optical gigawatt pulses in Kagome-lattice hollow-core photonic crystal fibers

    SciTech Connect

    Im, Song-Jin; Husakou, Anton; Herrmann, Joachim

    2010-08-15

    We study the delivery of few-cycle soliton-like pulses at 800 nm with gigawatt power or microjoule energy through a hollow-core kagome-lattice photonic crystal fiber over 1 m with preserved temporal and spectral shape. We show that with optimized pressure of the argon filling, 5 fs input pulses are compressed up to 2.5 fs after 20 cm and restore their shape after 1 m propagation.

  3. Recuperated atmosphere SOFC/gas turbine hybrid cycle

    DOEpatents

    Lundberg, Wayne

    2010-08-24

    A method of operating an atmospheric-pressure solid oxide fuel cell generator (6) in combination with a gas turbine comprising a compressor (1) and expander (2) where an inlet oxidant (20) is passed through the compressor (1) and exits as a first stream (60) and a second stream (62) the first stream passing through a flow control valve (56) to control flow and then through a heat exchanger (54) followed by mixing with the second stream (62) where the mixed streams are passed through a combustor (8) and expander (2) and the first heat exchanger for temperature control before entry into the solid oxide fuel cell generator (6), which generator (6) is also supplied with fuel (40).

  4. ALMA Observations of a High-density Core in Taurus: Dynamical Gas Interaction at the Possible Site of a Multiple Star Formation

    NASA Astrophysics Data System (ADS)

    Tokuda, Kazuki; Onishi, Toshikazu; Saigo, Kazuya; Kawamura, Akiko; Fukui, Yasuo; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro; Machida, Masahiro N.; Tomida, Kengo; Tachihara, Kengo

    2015-08-01

    It is crucially important to observe dense cores in order to investigate the initial condition of star formation since protostars are formed via dynamical collapse of dense cores, inhering the physical properties from their natal dense cores. Here we present the results of ALMA Cycle 0 and Cycle 1 observations of dust continuum emission and molecular rotational lines toward a dense core, MC27 (aka L1521F), which is considered to be very close to the first protostellar core phase.The Cycle 0 observations revealed complex structures at the center. We found a few starless high-density cores, one of which (MMS2) has a very high density of ~107 cm-3, around the very low-luminousity protostar detected by Spitzer. A very compact bipolar outflow with a dynamical timescale of a few hundred years was found toward the protostar. The HCO+ (3-2) observation shows several cores associated with an arc-like structure whose length is ~2000 AU, possibly due to the dynamical gas interaction. These complex structures suggest that the initial condition of star formation is highly dynamical in nature, which is considered to be a key factor in understanding fundamental issues of star formation such as origins of the stellar multiplicity and the initial mass function. These initial Cycle 0 results were published by Tokuda et al. (2014). Matsumoto et al. (2015) investigated the arc-like structures by performing numerical simulations.Detailed column density distribution with the size from ~100 to ~10000 AU scale are revealed by combining the 12m array data with the 7m array data of the ALMA Compact Array as well as with the single dish MAMBO data. Our preliminary analysis shows that the averaged radial column density distribution of the inner part (r < 2000 AU) is N(H2)~r-0.4, clearly flatter than that of the outer part, ~r-1.3. We detected the above-mentioned complex structure inside the inner flatter region, which may reflect the dynamical status of the dense core. The Cycle 1

  5. Rapid estimate of solid volume in large tuff cores using a gas pycnometer

    SciTech Connect

    Thies, C.; Geddis, A.M.; Guzman, A.G.

    1996-09-01

    A thermally insulated, rigid-volume gas pycnometer system has been developed. The pycnometer chambers have been machined from solid PVC cylinders. Two chambers confine dry high-purity helium at different pressures. A thick-walled design ensures minimal heat exchange with the surrounding environment and a constant volume system, while expansion takes place between the chambers. The internal energy of the gas is assumed constant over the expansion. The ideal gas law is used to estimate the volume of solid material sealed in one of the chambers. Temperature is monitored continuously and incorporated into the calculation of solid volume. Temperature variation between measurements is less than 0.1{degrees}C. The data are used to compute grain density for oven-dried Apache Leap tuff core samples. The measured volume of solid and the sample bulk volume are used to estimate porosity and bulk density. Intrinsic permeability was estimated from the porosity and measured pore surface area and is compared to in-situ measurements by the air permeability method. The gas pycnometer accommodates large core samples (0.25 m length x 0.11 m diameter) and can measure solid volume greater than 2.20 cm{sup 3} with less than 1% error.

  6. Film stability in a vertical rotating tube with a core-gas flow.

    NASA Technical Reports Server (NTRS)

    Sarma, G. S. R.; Lu, P. C.; Ostrach, S.

    1971-01-01

    The linear hydrodynamic stability of a thin-liquid layer flowing along the inside wall of a vertical tube rotating about its axis in the presence of a core-gas flow is examined. The stability problem is formulated under the conditions that the liquid film is thin, the density and viscosity ratios of gas to liquid are small and the relative (axial) pressure gradient in the gas is of the same order as gravity. The resulting eigenvalue problem is first solved by a perturbation method appropriate to axisymmetric long-wave disturbances. The damped nature (to within the thin-film and other approximations made) of the nonaxisymmetric and short-wave disturbances is noted. In view of the limitations on a truncated perturbation solution when the disturbance wavenumber is not small, an initial value method using digital computer is presented. Stability characteristics of neutral, growing, and damped modes are presented showing the influences of rotation, surface tension, and the core-gas flow. Energy balance in a neutral mode is also illustrated.

  7. Thermal analysis of a simple-cycle gas turbine in biogas power generation

    SciTech Connect

    Yomogida, D.E.; Thinh, Ngo Dinh

    1995-09-01

    This paper investigates the technical feasibility of utilizing small simple-cycle gas turbines (25 kW to 125 kW) for biogas power generation through thermal analysis. A computer code, GTPower, was developed to evaluate the performance of small simple-cycle gas turbines specifically for biogas combustion. The 125 KW Solar Gas Turbine (Tital series) has been selected as the base case gas turbine for biogas combustion. After its design parameters and typical operating conditions were entered into GTPower for analysis, GTPower outputted expected values for the thermal efficiency and specific work. For a sensitivity analysis, the GTPower Model outputted the thermal efficiency and specific work. For a sensitivity analysis, the GTPower Model outputted the thermal efficiency and specific work profiles for various operating conditions encountered in biogas combustion. These results will assist future research projects in determining the type of combustion device most suitable for biogas power generation.

  8. Integrating Natural Gas Hydrates in the Global Carbon Cycle

    SciTech Connect

    David Archer; Bruce Buffett

    2011-12-31

    We produced a two-dimensional geological time- and basin-scale model of the sedimentary margin in passive and active settings, for the simulation of the deep sedimentary methane cycle including hydrate formation. Simulation of geochemical data required development of parameterizations for bubble transport in the sediment column, and for the impact of the heterogeneity in the sediment pore fluid flow field, which represent new directions in modeling methane hydrates. The model is somewhat less sensitive to changes in ocean temperature than our previous 1-D model, due to the different methane transport mechanisms in the two codes (pore fluid flow vs. bubble migration). The model is very sensitive to reasonable changes in organic carbon deposition through geologic time, and to details of how the bubbles migrate, in particular how efficiently they are trapped as they rise through undersaturated or oxidizing chemical conditions and the hydrate stability zone. The active margin configuration reproduces the elevated hydrate saturations observed in accretionary wedges such as the Cascadia Margin, but predicts a decrease in the methane inventory per meter of coastline relative to a comparable passive margin case, and a decrease in the hydrate inventory with an increase in the plate subduction rate.

  9. Numerical simulation of the electrical properties of shale gas reservoir rock based on digital core

    NASA Astrophysics Data System (ADS)

    Nie, Xin; Zou, Changchun; Li, Zhenhua; Meng, Xiaohong; Qi, Xinghua

    2016-08-01

    In this paper we study the electrical properties of shale gas reservoir rock by applying the finite element method to digital cores which are built based on an advanced Markov Chain Monte Carlo method and a combination workflow. Study shows that the shale gas reservoir rock has strong anisotropic electrical conductivity because the conductivity is significantly different in both horizontal and vertical directions. The Archie formula is not suitable for application in shale reservoirs. The formation resistivity decreases in two cases; namely (a) with the increase of clay mineral content and the cation exchange capacity of clay, and (b) with the increase of pyrite content. The formation resistivity is not sensitive to the solid organic matter but to the clay and gas in the pores.

  10. Downhole well log and core montages from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Collett, T.S.; Lewis, R.E.; Winters, W.J.; Lee, M.W.; Rose, K.K.; Boswell, R.M.

    2011-01-01

    The BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well was an integral part of an ongoing project to determine the future energy resource potential of gas hydrates on the Alaska North Slope. As part of this effort, the Mount Elbert well included an advanced downhole geophysical logging program. Because gas hydrate is unstable at ground surface pressure and temperature conditions, a major emphasis was placed on the downhole-logging program to determine the occurrence of gas hydrates and the in-situ physical properties of the sediments. In support of this effort, well-log and core data montages have been compiled which include downhole log and core-data obtained from the gas-hydrate-bearing sedimentary section in the Mount Elbert well. Also shown are numerous reservoir parameters, including gas-hydrate saturation and sediment porosity log traces calculated from available downhole well log and core data. ?? 2010.

  11. Gas Sloshing and Radio Galaxy Dynamics in the Core of the 3C 449 Group

    NASA Technical Reports Server (NTRS)

    Lal, Dharam V.; Kraft, Ralph P.; Randall, Scott W.; Forman, William R.; Nulsen, Paul E.; Roediger, Elke; ZuHone, John A.; Hardcastle, Martin J.; Jones, Christine; Croston, Judith H.

    2013-01-01

    We present results from a 140 ks Chandra/ACIS-S observation of the hot gas around the canonical FR I radio galaxy 3C 449. An earlier, shorter 30 ks Chandra observation of the group gas showed an unusual entropy distribution and a surface brightness edge in the gas that could be a strong shock around the inner radio lobes. In our deeper data we find no evidence for a temperature increase inside of the brightness edge, but a temperature decrease across part of the edge. This suggests that the edge is a "sloshing" cold front due to a merger within the last 1.3-1.6 Gyr. Both the northern and southern inner jets are bent slightly to the west in projection as they enter their respective lobes, suggesting that the sloshing core is moving to the east. The straight inner jet flares at approximately the position where it crosses the contact edge, suggesting that the jet is entraining and thermalizing some of the hot gas as it crosses the edge.We also detect filaments of X-ray emission around the southern inner radio jet and lobe which we attribute to low entropy entrained gas. The lobe flaring and gas entrainment were originally predicted in simulations of Loken et al. and are confirmed in our deep observation.

  12. GAS SLOSHING AND RADIO GALAXY DYNAMICS IN THE CORE OF THE 3C 449 GROUP

    SciTech Connect

    Lal, Dharam V.; Kraft, Ralph P.; Randall, Scott W.; Forman, William R.; Nulsen, Paul E. J.; Jones, Christine; Roediger, Elke; ZuHone, John A.; Hardcastle, Martin J.; Croston, Judith H.

    2013-02-10

    We present results from a 140 ks Chandra/ACIS-S observation of the hot gas around the canonical FR I radio galaxy 3C 449. An earlier, shorter 30 ks Chandra observation of the group gas showed an unusual entropy distribution and a surface brightness edge in the gas that could be a strong shock around the inner radio lobes. In our deeper data we find no evidence for a temperature increase inside of the brightness edge, but a temperature decrease across part of the edge. This suggests that the edge is a 'sloshing' cold front due to a merger within the last {approx}<1.3-1.6 Gyr. Both the northern and southern inner jets are bent slightly to the west in projection as they enter their respective lobes, suggesting that the sloshing core is moving to the east. The straight inner jet flares at approximately the position where it crosses the contact edge, suggesting that the jet is entraining and thermalizing some of the hot gas as it crosses the edge. We also detect filaments of X-ray emission around the southern inner radio jet and lobe which we attribute to low entropy entrained gas. The lobe flaring and gas entrainment were originally predicted in simulations of Loken et al. and are confirmed in our deep observation.

  13. Selection of the air heat exchanger operating in a gas turbine air bottoming cycle

    NASA Astrophysics Data System (ADS)

    Chmielniak, Tadeusz; Czaja, Daniel; Lepszy, Sebastian

    2013-12-01

    A gas turbine air bottoming cycle consists of a gas turbine unit and the air turbine part. The air part includes a compressor, air expander and air heat exchanger. The air heat exchanger couples the gas turbine to the air cycle. Due to the low specific heat of air and of the gas turbine exhaust gases, the air heat exchanger features a considerable size. The bigger the air heat exchanger, the higher its effectiveness, which results in the improvement of the efficiency of the gas turbine air bottoming cycle. On the other hand, a device with large dimensions weighs more, which may limit its use in specific locations, such as oil platforms. The thermodynamic calculations of the air heat exchanger and a preliminary selection of the device are presented. The installation used in the calculation process is a plate heat exchanger, which is characterized by a smaller size and lower values of the pressure drop compared to the shell and tube heat exchanger. Structurally, this type of the heat exchanger is quite similar to the gas turbine regenerator. The method on which the calculation procedure may be based for real installations is also presented, which have to satisfy the economic criteria of financial profitability and cost-effectiveness apart from the thermodynamic criteria.

  14. The gas phase origin of complex organic molecules precursors in prestellar cores

    NASA Astrophysics Data System (ADS)

    Bacmann, A.; Faure, A.

    2016-05-01

    Complex organic molecules (COMs) have long been observed in the warm regions surrounding nascent protostars. The recent discovery of oxygen-bearing COMs like methyl formate or dimethyl ether in prestellar cores (Bacmann et al. [2]), where gas and dust temperatures rarely exceed 10-15 K, has challenged the previously accepted models according to which COM formation relied on the diffusion of heavy radicals on warm (˜30 K) grains. Following these detections, new questions have arisen: do non-thermal processes play a role in increasing radical mobility or should new gas-phase routes be explored? The radicals involved in the formation of the aforementioned COMs, HCO and CH3O represent intermediate species in the grain-surface synthesis of methanol which proceeds via successive hydrogenations of CO molecules in the ice. We present here observations of methanol and its grain-surface precursors HCO, H2CO, CH3O in a sample of prestellar cores and derive their relative abundances. We find that the relative abundances HCO:H2CO:CH3O:CH3OH are constant across the core sample, close to 10:100:1:100. Our results also show that the amounts of HCO and CH3O are consistent with a gas-phase synthesis of these species from H2CO and CH3OH via radical-neutral or ion-molecule reactions followed by dissociative recombinations. Thus, while grain chemistry is necessary to explain the abundances of the parent volatile CH3OH, and possibly H2CO, the reactive species HCO and CH3O might be daughter molecules directly produced in the gas-phase.

  15. Core cell cycle regulatory genes in rice and their expression profiles across the growth zone of the leaf.

    PubMed

    Pettkó-Szandtner, A; Cserháti, M; Barrôco, R M; Hariharan, S; Dudits, D; Beemster, G T S

    2015-11-01

    Rice (Oryza sativa L.) as a model and crop plant with a sequenced genome offers an outstanding experimental system for discovering and functionally analyzing the major cell cycle control elements in a cereal species. In this study, we identified the core cell cycle genes in the rice genome through a hidden Markov model search and multiple alignments supported with the use of short protein sequence probes. In total we present 55 rice putative cell cycle genes with locus identity, chromosomal location, approximate chromosome position and EST accession number. These cell cycle genes include nine cyclin dependent-kinase (CDK) genes, 27 cyclin genes, one CKS gene, two RBR genes, nine E2F/DP/DEL genes, six KRP genes, and one WEE gene. We also provide characteristic protein sequence signatures encoded by CDK and cyclin gene variants. Promoter analysis by the FootPrinter program discovered several motifs in the regulatory region of the core cell cycle genes. As a first step towards functional characterization we performed transcript analysis by RT-PCR to determine gene specific variation in transcript levels along the rice leaves. The meristematic zone of the leaves where cells are actively dividing was identified based on kinematic analysis and flow cytometry. As expected, expression of the majority of cell cycle genes was exclusively associated with the meristematic region. However genes such as different D-type cyclins, DEL1, KRP1/3, and RBR2 were also expressed in leaf segments representing the transition zone in which cells start differentiation. PMID:26459328

  16. Impacts of Vehicle Weight Reduction via Material Substitution on Life-Cycle Greenhouse Gas Emissions

    SciTech Connect

    Kelly, Jarod C.; Sullivan, John L.; Burnham, Andrew; Elgowainy, Amgad

    2015-10-20

    This study examines the vehicle-cycle impacts associated with substituting lightweight materials for those currently found in light-duty passenger vehicles. We determine part-based energy use and greenhouse gas (GHG) emission ratios by collecting material substitution data from both the literature and automotive experts and evaluating that alongside known mass-based energy use and GHG emission ratios associated with material pair substitutions. Several vehicle parts, along with full vehicle systems, are examined for lightweighting via material substitution to observe the associated impact on GHG emissions. Results are contextualized by additionally examining fuel-cycle GHG reductions associated with mass reductions relative to the baseline vehicle during the use phase and also determining material pair breakeven driving distances for GHG emissions. The findings show that, while material substitution is useful in reducing vehicle weight, it often increases vehicle-cycle GHGs depending upon the material substitution pair. However, for a vehicle’s total life cycle, fuel economy benefits are greater than the increased burdens associated with the vehicle manufacturing cycle, resulting in a net total life-cycle GHG benefit. The vehicle cycle will become increasingly important in total vehicle life-cycle GHGs, since fuel-cycle GHGs will be gradually reduced as automakers ramp up vehicle efficiency to meet fuel economy standards.

  17. The HIPPO Project Archive: Carbon Cycle and Greenhouse Gas Data

    NASA Astrophysics Data System (ADS)

    Christensen, S. W.; Aquino, J.; Hook, L.; Williams, S. F.

    2012-12-01

    The HIAPER (NSF/NCAR Gulfstream V Aircraft) Pole-to-Pole Observations (HIPPO) project measured a comprehensive suite of atmospheric trace gases and aerosols pertinent to understanding the global carbon cycle from the surface to the tropopause and approximately pole-to-pole over the Pacific Ocean. Flights took place over five missions during different seasons from 2009 to 2011. Data and documentation are available to the public from two archives: (1) NCAR's Earth Observing Laboratory (EOL) provides complete aircraft and flight operational data, and (2) the U.S. DOE's Carbon Dioxide Information Analysis Center (CDIAC) provides integrated measurement data products. The integrated products are more generally useful for secondary analyses. Data processing is nearing completion, although improvements to the data will continue to evolve and analyses will continue many years into the future. Periodic new releases of integrated measurement (merged) products will be generated by EOL when individual measurement data have been updated as directed by the Lead Principal Investigator. The EOL and CDIAC archives will share documentation and supplemental links and will ensure that the latest versions of data products are available to users of both archives. The EOL archive (http://www.eol.ucar.edu/projects/hippo/) provides the underlying investigator-provided data, including supporting data sets (e.g. operational satellite, model output, global observations, etc.), and ancillary flight operational information including field catalogs, data quality reports, software, documentation, publications, photos/imagery, and other detailed information about the HIPPO missions. The CDIAC archive provides integrated measurement data products, user documentation, and metadata through the HIPPO website (http://hippo.ornl.gov). These merged products were derived by consistently combining the aircraft state parameters for position, time, temperature, pressure, and wind speed with meteorological

  18. Operability test report for core sample truck {number_sign}1 flammable gas modifications

    SciTech Connect

    Akers, J.C.

    1997-09-15

    This report primarily consists of the original test procedure used for the Operability Testing of the flammable gas modifications to Core Sample Truck No. One. Included are exceptions, resolutions, comments, and test results. This report consists of the original, completed, test procedure used for the Operability Testing of the flammable gas modifications to the Push Mode Core Sample Truck No. 1. Prior to the Acceptance/Operability test the truck No. 1 operations procedure (TO-080-503) was revised to be more consistent with the other core sample truck procedures and to include operational steps/instructions for the SR weather cover pressurization system. A draft copy of the operations procedure was used to perform the Operability Test Procedure (OTP). A Document Acceptance Review Form is included with this report (last page) indicating the draft status of the operations procedure during the OTP. During the OTP 11 test exceptions were encountered. Of these exceptions four were determined to affect Acceptance Criteria as listed in the OTP, Section 4.7 ACCEPTANCE CRITERIA.

  19. Absorbance characteristics of a liquid-phase gas sensor based on gas-permeable liquid core waveguides.

    PubMed

    Peng, Pei; Wang, Wei; Zhang, Li; Su, Shiguang; Wang, Jiahui

    2013-12-01

    The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas-permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r(2)>0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min(-1), the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC=0.0267c+0.0351 (AU min(-1)), with r(2)=0.9922 within concentrations of 0.5-3.0 mg L(-1). The relative error for 0.5 mg L(-1) benzene (n=6) is 7.4±3.7%, and the LOD is 0.04 mg L(-1). This research can provide theoretical and practical guides for liquid-phase gas sensor design and development based on a

  20. Response of Soil Biogeochemistry to Freeze-thaw Cycles: Impacts on Greenhouse Gas Emission and Nutrient Fluxes

    NASA Astrophysics Data System (ADS)

    Rezanezhad, F.; Parsons, C. T.; Smeaton, C. M.; Van Cappellen, P.

    2014-12-01

    Freeze-thaw is an abiotic stress applied to soils and is a natural process at medium to high latitudes. Freezing and thawing processes influence not only the physical properties of soil, but also the metabolic activity of soil microorganisms. Fungi and bacteria play a crucial role in soil organic matter degradation and the production of greenhouse gases (GHG) such as CO2, CH4 and N2O. Production and consumption of these atmospheric trace gases are the result of biological processes such as photosynthesis, aerobic respiration (CO2), methanogenesis, methanotrophy (CH4), nitrification and denitrification (N2O). To enhance our understanding of the effects of freeze-thaw cycles on soil biogeochemical transformations and fluxes, a highly instrumented soil column experiment was designed to realistically simulate freeze-thaw dynamics under controlled conditions. Pore waters collected periodically from different depths of the column and solid-phase analyses on core material obtained at the initial and end of the experiment highlighted striking geochemical cycling. CO2, CH4 and N2O production at different depths within the column were quantified from dissolved gas concentrations in pore water. Subsequent emissions from the soil surface were determined by direct measurement in the head space. Pulsed CO2 emission to the headspace was observed at the onset of thawing, however, the magnitude of the pulse decreased with each subsequent freeze-thaw cycle indicating depletion of a "freeze-thaw accessible" carbon pool. Pulsed CO2 emission was due to a combination of physical release of gases dissolved in porewater and entrapped below the frozen zone and changing microbial respiration in response to electron acceptor variability (O2, NO3-, SO42-). In this presentation, we focus on soil-specific physical, chemical, microbial factors (e.g. redox conditions, respiration, fermentation) and the mechanisms that drive GHG emission and nutrient cycling in soils under freeze-thaw cycles.

  1. The Development of a New Practical Activity: Using Microorganisms to Model Gas Cycling

    ERIC Educational Resources Information Center

    Redfern, James; Burdass, Dariel; Verran, Joanna

    2014-01-01

    For many in the school science classroom, the term "microbiology" has become synonymous with "bacteriology". By overlooking other microbes, teachers may miss out on powerful practical tools. This article describes the development of an activity that uses algae and yeast to demonstrate gas cycling, and presents full instructions…

  2. Life cycle assessment of greenhouse gas emissions from beef production systems in California

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Beef production is recognized as a source of greenhouse gas (GHG) emissions; however, little information exists on the net emission from production systems. A life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate whole-farm GHG emissions from representa...

  3. Correlation between CAM-Cycling and Photosynthetic Gas Exchange in Five Species of Talinum (Portulacaceae) 1

    PubMed Central

    Harris, Fred S.; Martin, Craig E.

    1991-01-01

    Photosynthetic gas exchange and malic acid fluctuations were monitored in 69 well-watered plants from five morphologically similar species of Talinum in an investigation of the ecophysiological significance of the Crassulacean acid metabolism (CAM)-cycling mode of photosynthesis. Unlike CAM, atmospheric CO2 uptake in CAM-cycling occurs exclusively during the day; at night, the stomata are closed and respiratory CO2 is recaptured to form malic acid. All species showed similar patterns of day-night gas exchange and overnight malic acid accumulation, confirming the presence of CAM-cycling. Species averages for gas exchange parameters and malic acid fluctuation were significantly different such that the species with the highest daytime gas exchange had the lowest malic acid accumulation and vice versa. Also, daytime CO2 exchange and transpiration were negatively correlated with overnight malic acid fluctuation for all individuals examined together, as well as within one species. This suggests that malic acid may effect reductions in both atmospheric CO2 uptake and transpiration during the day. No significant correlation between malic acid fluctuation and water-use efficiency was found, although a nonsignificant trend of increasing water-use efficiency with increasing malic acid fluctuation was observed among species averages. This study provides evidence that CO2 recycling via malic acid is negatively correlated with daytime transpirational water losses in well-watered plants. Thus, CAM-cycling could be important for survival in the thin, frequently desiccated soils of rock outcrops on which these plants occur. PMID:16668307

  4. Pulmonary Gas Transfer Related to Markers of Angiogenesis during the Menstrual Cycle

    PubMed Central

    Farha, Samar; Asosingh, Kewal; Laskowski, Daniel; Licina, Lauren; Sekigushi, Haruki; Losordo, Douglas W.; Dweik, Raed A.; Wiedemann, Herbert P.; Erzurum, Serpil C.

    2010-01-01

    Gas transfer in the female lung varies over the menstrual cycle in parallel with the cyclic angiogenesis that occurs in the uterine endometrium. Given that vessels form and regress in the uterus under the control of hormones, angiogenic factors and pro-angiogenic circulating bone marrow-derived progenitor cells, we tested the possibility that variation in pulmonary gas transfer over the menstrual cycle is related to a systemic cyclic pro-angiogenic state that influences lung vascularity. Women were evaluated over the menstrual cycle with weekly measures of lung diffusing capacity and its components, the pulmonary vascular capillary bed and membrane diffusing capacity, and their relation to circulating CD34+CD133+ progenitor cells, hemoglobin, factors affecting hemoglobin binding affinity, and pro-angiogenic factors. Lung diffusing capacity varied over the menstrual cycle, reaching a nadir during the follicular phase following menses. The decline in lung diffusing capacity was accounted for by ~25% decrease in pulmonary capillary blood volume. In parallel, circulating CD34+CD133+ progenitor cells decreased by ~24%, and were directly related to angiogenic factors, and to lung diffusing capacity and pulmonary capillary blood volume. The finding of greater number of lung microvessels in ovariectomized female mice receiving estrogen as compared to placebo verified that pulmonary vascularity is influenced by hormonal changes. These findings suggest that angiogenesis in the lungs may participate in the cyclic changes in gas transfer that occur over the menstrual cycle. PMID:17717117

  5. Proposing a novel combined cycle for optimal exergy recovery of liquefied natural gas

    NASA Astrophysics Data System (ADS)

    Salimpour, M. R.; Zahedi, M. A.

    2012-08-01

    The effective utilization of the cryogenic exergy associated with liquefied natural gas (LNG) vaporization is important. In this paper, a novel combined power cycle is proposed which utilizes LNG in different ways to enhance the power generation of a power plant. In addition to the direct expansion in the appropriate expander, LNG is used as a low-temperature heat sink for a middle-pressure gas cycle which uses nitrogen as working fluid. Also, LNG is used to cool the inlet air of an open Brayton gas turbine cycle. These measures are accomplished to improve the exergy recovery of LNG. In order to analyze the performance of the system, the influence of several key parameters such as pressure ratio of LNG turbine, ratio of the mass flow rate of LNG to the mass flow rate of air, pressure ratio of different compressors, LNG pressure and inlet pressure of nitrogen compressor, on the thermal efficiency and exergy efficiency of the offered cycle is investigated. Finally, the proposed combined cycle is optimized on the basis of first and second laws of thermodynamics.

  6. The feasibility study of small long-life gas cooled fast reactor with mixed natural Uranium/Thorium as fuel cycle input

    SciTech Connect

    Ariani, Menik; Su'ud, Zaki; Waris, Abdul; Khairurrijal,; Monado, Fiber; Sekimoto, Hiroshi

    2012-06-06

    A conceptual design study of Gas Cooled Fast Reactors with Modified CANDLE burn-up scheme has been performed. In this study, design GCFR with Helium coolant which can be continuously operated by supplying mixed Natural Uranium/Thorium without fuel enrichment plant or fuel reprocessing plant. The active reactor cores are divided into two region, Thorium fuel region and Uranium fuel region. Each fuel core regions are subdivided into ten parts (region-1 until region-10) with the same volume in the axial direction. The fresh Natural Uranium and Thorium is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and the each region-1 is filled by fresh natural Uranium/Thorium fuel. This concept is basically applied to all regions in both cores area, i.e. shifted the core of i{sup th} region into i+1 region after the end of 10 years burn-up cycle. For the next cycles, we will add only Natural Uranium and Thorium on each region-1. The calculation results show the reactivity reached by mixed Natural Uranium/Thorium with volume ratio is 4.7:1. This reactor can results power thermal 550 MWth. After reactor start-up the operation, furthermore reactor only needs Natural Uranium/Thorium supply for continue operation along 100 years.

  7. The feasibility study of small long-life gas cooled fast reactor with mixed natural Uranium/Thorium as fuel cycle input

    NASA Astrophysics Data System (ADS)

    Ariani, Menik; Su'ud, Zaki; Waris, Abdul; Khairurrijal, Monado, Fiber; Sekimoto, Hiroshi

    2012-06-01

    A conceptual design study of Gas Cooled Fast Reactors with Modified CANDLE burn-up scheme has been performed. In this study, design GCFR with Helium coolant which can be continuously operated by supplying mixed Natural Uranium/Thorium without fuel enrichment plant or fuel reprocessing plant. The active reactor cores are divided into two region, Thorium fuel region and Uranium fuel region. Each fuel core regions are subdivided into ten parts (region-1 until region-10) with the same volume in the axial direction. The fresh Natural Uranium and Thorium is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and the each region-1 is filled by fresh natural Uranium/Thorium fuel. This concept is basically applied to all regions in both cores area, i.e. shifted the core of ith region into i+1 region after the end of 10 years burn-up cycle. For the next cycles, we will add only Natural Uranium and Thorium on each region-1. The calculation results show the reactivity reached by mixed Natural Uranium/Thorium with volume ratio is 4.7:1. This reactor can results power thermal 550 MWth. After reactor start-up the operation, furthermore reactor only needs Natural Uranium/Thorium supply for continue operation along 100 years.

  8. Life cycle water consumption and wastewater generation impacts of a Marcellus shale gas well.

    PubMed

    Jiang, Mohan; Hendrickson, Chris T; VanBriesen, Jeanne M

    2014-01-01

    This study estimates the life cycle water consumption and wastewater generation impacts of a Marcellus shale gas well from its construction to end of life. Direct water consumption at the well site was assessed by analysis of data from approximately 500 individual well completion reports collected in 2010 by the Pennsylvania Department of Conservation and Natural Resources. Indirect water consumption for supply chain production at each life cycle stage of the well was estimated using the economic input-output life cycle assessment (EIO-LCA) method. Life cycle direct and indirect water quality pollution impacts were assessed and compared using the tool for the reduction and assessment of chemical and other environmental impacts (TRACI). Wastewater treatment cost was proposed as an additional indicator for water quality pollution impacts from shale gas well wastewater. Four water management scenarios for Marcellus shale well wastewater were assessed: current conditions in Pennsylvania; complete discharge; direct reuse and desalination; and complete desalination. The results show that under the current conditions, an average Marcellus shale gas well consumes 20,000 m(3) (with a range from 6700 to 33,000 m(3)) of freshwater per well over its life cycle excluding final gas utilization, with 65% direct water consumption at the well site and 35% indirect water consumption across the supply chain production. If all flowback and produced water is released into the environment without treatment, direct wastewater from a Marcellus shale gas well is estimated to have 300-3000 kg N-eq eutrophication potential, 900-23,000 kg 2,4D-eq freshwater ecotoxicity potential, 0-370 kg benzene-eq carcinogenic potential, and 2800-71,000 MT toluene-eq noncarcinogenic potential. The potential toxicity of the chemicals in the wastewater from the well site exceeds those associated with supply chain production, except for carcinogenic effects. If all the Marcellus shale well wastewater is

  9. Life Cycle Water Consumption and Wastewater Generation Impacts of a Marcellus Shale Gas Well

    PubMed Central

    2013-01-01

    This study estimates the life cycle water consumption and wastewater generation impacts of a Marcellus shale gas well from its construction to end of life. Direct water consumption at the well site was assessed by analysis of data from approximately 500 individual well completion reports collected in 2010 by the Pennsylvania Department of Conservation and Natural Resources. Indirect water consumption for supply chain production at each life cycle stage of the well was estimated using the economic input–output life cycle assessment (EIO-LCA) method. Life cycle direct and indirect water quality pollution impacts were assessed and compared using the tool for the reduction and assessment of chemical and other environmental impacts (TRACI). Wastewater treatment cost was proposed as an additional indicator for water quality pollution impacts from shale gas well wastewater. Four water management scenarios for Marcellus shale well wastewater were assessed: current conditions in Pennsylvania; complete discharge; direct reuse and desalination; and complete desalination. The results show that under the current conditions, an average Marcellus shale gas well consumes 20 000 m3 (with a range from 6700 to 33 000 m3) of freshwater per well over its life cycle excluding final gas utilization, with 65% direct water consumption at the well site and 35% indirect water consumption across the supply chain production. If all flowback and produced water is released into the environment without treatment, direct wastewater from a Marcellus shale gas well is estimated to have 300–3000 kg N-eq eutrophication potential, 900–23 000 kg 2,4D-eq freshwater ecotoxicity potential, 0–370 kg benzene-eq carcinogenic potential, and 2800–71 000 MT toluene-eq noncarcinogenic potential. The potential toxicity of the chemicals in the wastewater from the well site exceeds those associated with supply chain production, except for carcinogenic effects. If all the Marcellus shale well

  10. Effect of duty-cycles on the air plasma gas-phase of dielectric barrier discharges

    NASA Astrophysics Data System (ADS)

    Barni, R.; Biganzoli, I.; Dell'Orto, E. C.; Riccardi, C.

    2015-10-01

    An experimental investigation concerning the effects of a duty-cycle in the supply of a dielectric barrier discharge in atmospheric pressure air has been performed. Electrical characteristics of the discharge have been measured, focusing mainly on the statistical properties of the current filaments and on dielectric surface charging, both affected by the frequent repetition of breakdown imposed by the duty-cycle. Information on the gas-phase composition was gathered too. In particular, a strong enhancement in the ozone formation rate is observed when suitable long pauses separate the active discharge phases. A simulation of the chemical kinetics in the gas-phase, based on a simplified discharge modeling, is briefly described in order to shed light on the observed increase in ozone production. The effect of a duty-cycle on surface modification of polymeric films in order to increase their wettability has been investigated too.

  11. Gas-phase CO depletion and N2H+ abundances in starless cores

    NASA Astrophysics Data System (ADS)

    Lippok, N.; Launhardt, R.; Semenov, D.; Stutz, A. M.; Balog, Z.; Henning, Th.; Krause, O.; Linz, H.; Nielbock, M.; Pavlyuchenkov, Ya. N.; Schmalzl, M.; Schmiedeke, A.; Bieging, J. H.

    2013-12-01

    +. Chemical modeling indirectly suggests that the gas and dust temperatures decouple in the envelopes and that the dust grains are not yet significantly coagulated. Conclusions: We observationally confirm chemical models of CO-freezeout and nitrogen chemistry. We find clear correlations between the hydrogen density and CO depletion and the emergence of N2H+. The chemical ages indicate a core lifetime of less than 1 Myr. This work is partially based on observations by the Herschel Space Observatory. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.org

  12. Research of the DC discharge of He-Ne gas mixture in hollow core fiber

    NASA Astrophysics Data System (ADS)

    Wang, Xinbing; Duan, Lian

    2013-09-01

    Since the first waveguide 0.633 μm He-Ne laser from a 20 cm length of 430 μm glass capillary was reported in 1971, no smaller waveguide gas laser has ever been constructed. Recently as the development of low loss hollow core PBG fiber, it is possible to constract a He-Ne lasers based on hollow-core PBG fibers. For the small diameter of the air hole, it is necessary to do some research to obtain glow discharge in hollow core fibers. In this paper, the experimental research of DC discharge in 200 μm bore diameter hollow core fibers was reported. Stable glow discharge was obained at varioue He-Ne mixtures from 4 Torr to 18 Torr. In order to obtain the plasma parameter of the discharge, the trace gasses of N2 and H2 were added to the He-Ne mixtures, the optical emission spectroscopy of the discharge was recorded by a PI 2750 spectroscopy with a CCD camera. The gas temperature (Tg) could be obtained by matching the simulated rovibronic band of the N2 emission with the observed spectrum in the ultraviolet region. The spectral method was also used to obtained the electron density, which is based on the analysis of the wavelength profile of the 486.13 nm Hβ line, and the electron temperature was obtain by Boltzmann plot methods. Experimental results show that it is very difficult to achieve DC discharge in bore diameter less than 50 μm, and a RF discharge method was proposed. Project supported by the National Natural Science Foundation of China (61078033).

  13. Sloshing of the Magnetized Cool Gas in the Cores of Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    ZuHone, J. A.; Markevitch, M.; Lee, D.

    2011-01-01

    X-ray observations of many clusters of galaxies reveal the presence of edges in surface brightness and temperature, known as "cold fronts". In relaxed clusters with cool cores, these edges have been interpreted as evidence for the "sloshing" of the core gas in the cluster's gravitational potential. The smoothness of these edges has been interpreted as evidence for the stabilizing effect of magnetic fields "draped" around the front surfaces. To check this hypothesis, we perform high-resolution magnetohydrodynamics simulations of magnetized gas sloshing in galaxy clusters initiated by encounters with subclusters. We go beyond previous works on the simulation of cold fronts in a magnetized intracluster medium by simulating their formation in realistic, idealized mergers with high resolution ((Delta)x approx. 2 kpc). Our simulations sample a parameter space of plausible initial magnetic field strengths and field configurations. In the simulations, we observe strong velocity shears associated with the cold fronts amplifying the magnetic field along the cold front surfaces, increasing the magnetic field strength in these layers by up to an order of magnitude, and boosting the magnetic pressure up to near-equipartition with thermal pressure in some cases. In these layers, the magnetic field becomes strong enough to stabilize the cold fronts against Kelvin-Helmholtz instabilities, resulting in sharp, smooth fronts as those seen in observations of real clusters. These magnetic fields also result in strong suppression of mixing of high and low-entropy gas in the cluster, seen in our simulations of mergers in the absence of a magnetic field. As a result, the heating of the core due to sloshing is very modest and is unable to stave off a cooling catastrophe.

  14. Alternative functions of core cell cycle regulators in neuronal migration, neuronal maturation, and synaptic plasticity

    PubMed Central

    Frank, Christopher L.; Tsai, Li-Huei

    2009-01-01

    Recent studies have demonstrated that boundaries separating a cycling cell from a post-mitotic neuron are not as concrete as expected. Novel and unique physiological functions in neurons have been ascribed for proteins fundamentally required for cell cycle progression and control. These “core” cell cycle regulators serve diverse post-mitotic functions that span various developmental stages of a neuron, including neuronal migration, axonal elongation, axon pruning, dendrite morphogenesis, and synaptic maturation and plasticity. In this review, we detail the non-proliferative post-mitotic roles that these cell cycle proteins have recently been reported to play, the significance of their expression in neurons, mechanistic insight when available, and future prospects. PMID:19447088

  15. Analytic methods for design of wave cycles for wave rotor core engines

    NASA Technical Reports Server (NTRS)

    Resler, Edwin L., Jr.; Mocsari, Jeffrey C.; Nalim, M. R.

    1993-01-01

    A procedure to design a preliminary wave rotor cycle for any application is presented. To complete a cycle with heat addition there are two separate but related design steps that must be followed. The 'wave' boundary conditions determine the allowable amount of heat added in any case and the ensuing wave pattern requires certain pressure discharge conditions to allow the process to be made cyclic. This procedure, when applied, gives a first estimate of the cycle performance and the necessary information for the next step in the design process, namely the application of a characteristic based or other appropriate detailed one dimensional wave calculation that locates the proper porting around the periphery of the wave rotor. Four examples of the design procedure are given to demonstrate its utility and generality. These examples also illustrate the large gains in performance that could be realized with the use of wave rotor enhanced propulsion cycles.

  16. Cavity temperature and flow characteristics in a gas-core test reactor

    NASA Technical Reports Server (NTRS)

    Putre, H. A.

    1973-01-01

    A test reactor concept for conducting basic studies on a fissioning uranium plasma and for testing various gas-core reactor concepts is analyzed. The test reactor consists of a conventional fuel-element region surrounding a 61-cm-(2-ft-) diameter cavity region which contains the plasma experiment. The fuel elements provide the neutron flux for the cavity region. The design operating conditions include 60-MW reactor power, 2.7-MW cavity power, 200-atm cavity pressure, and an average uranium plasma temperature of 15,000 K. The analytical results are given for cavity radiant heat transfer, hydrogen transpiration cooling, and uranium wire or powder injection.

  17. Fuel performance models for high-temperature gas-cooled reactor core design

    SciTech Connect

    Stansfield, O.M.; Simon, W.A.; Baxter, A.M.

    1983-09-01

    Mechanistic fuel performance models are used in high-temperature gas-cooled reactor core design and licensing to predict failure and fission product release. Fuel particles manufactured with defective or missing SiC, IPyC, or fuel dispersion in the buffer fail at a level of less than 5 x 10/sup -4/ fraction. These failed particles primarily release metallic fission products because the OPyC remains intact on 90% of the particles and retains gaseous isotopes. The predicted failure of particles using performance models appears to be conservative relative to operating reactor experience.

  18. Improving greenhouse gas reduction calculations for bioenergy systems: Incremental life cycle analysis

    NASA Astrophysics Data System (ADS)

    Ney, Richard A.

    There are many scales that can be employed to calculate net greenhouse gas emissions from bioenergy systems, ranging from single point source (stack gas) measurement, to full, multi-layered life cycle analyses considering all of the inputs and outputs throughout the economy. At an appropriate scale within these extremes, a method can be selected to support verification activities related to project-based trading of greenhouse gas emissions. The boundaries of the analysis must be carefully selected in order to meet the twin goals of the verification activity: (1) to meet scientific standards for emission balance quantification; and (2) to meet cost-effectiveness criteria of the emission trading community. The Incremental Life Cycle Analysis (ILCA) methodology is proposed and implemented for the quantification of greenhouse gas emission reductions arising from substitution of switchgrass for coal in electricity generation. The method utilizes an incremental progression through the fuel life cycle, evaluating each level of the life cycle for the quality the emission estimate produced. The method also reviews the scientific uncertainty underlying emission estimation procedures so that areas of relative weakness can be targeted and improved. The ILCA methodology is applied to the Chariton Valley Biomass Project (CVBP) for case study and evaluation. The CVBP is seeking to replace coal combustion in an existing 650-MW generation facility with switchgrass, cofired at a rate of 5 percent switchgrass to 95 percent coal. When the project reaches full capacity, the ILCA estimates that 239 pounds of carbon dioxide-equivalent (CO2-eq) emissions will be reduced and/or removed from the atmosphere for every million Btu of switchgrass utilized, generating annual greenhouse gas reductions of 305,000 tons CO2-eq, leading to revenue for the project totaling over $1.5 million annually through trading of greenhouse gas emission reduction credits.

  19. Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Stern, Laura A.; Lorenson, T.D.; Pinkston, John C.

    2011-01-01

    Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA–DOE–USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5 m to 760.1 m depth, and sections investigated here were retrieved from 619.9 m and 661.0 m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70–75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20–120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas.

  20. Gas hydrate characterization and grain-scale imaging of recovered cores from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

    USGS Publications Warehouse

    Stern, L.A.; Lorenson, T.D.; Pinkston, J.C.

    2011-01-01

    Using cryogenic scanning electron microscopy (CSEM), powder X-ray diffraction, and gas chromatography methods, we investigated the physical states, grain characteristics, gas composition, and methane isotopic composition of two gas-hydrate-bearing sections of core recovered from the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well situated on the Alaska North Slope. The well was continuously cored from 606.5. m to 760.1. m depth, and sections investigated here were retrieved from 619.9. m and 661.0. m depth. X-ray analysis and imaging of the sediment phase in both sections shows it consists of a predominantly fine-grained and well-sorted quartz sand with lesser amounts of feldspar, muscovite, and minor clays. Cryogenic SEM shows the gas-hydrate phase forming primarily as a pore-filling material between the sediment grains at approximately 70-75% saturation, and more sporadically as thin veins typically several tens of microns in diameter. Pore throat diameters vary, but commonly range 20-120 microns. Gas chromatography analyses of the hydrate-forming gas show that it is comprised of mainly methane (>99.9%), indicating that the gas hydrate is structure I. Here we report on the distribution and articulation of the gas-hydrate phase within the cores, the grain morphology of the hydrate, the composition of the sediment host, and the composition of the hydrate-forming gas. ?? 2009.

  1. Cycle analysis of an integrated solid oxide fuel cell and recuperative gas turbine with an air reheating system

    NASA Astrophysics Data System (ADS)

    Zhang, Xiongwen; Li, Jun; Li, Guojun; Feng, Zhenping

    Cycle simulation and analysis for two kinds of SOFC/GT hybrid systems were conducted with the help of the simulation tool: Aspen Custom Modeler. Two cycle schemes of recuperative heat exchanger (RHE) and exhaust gas recirculated (EGR) were described according to the air reheating method. The system performance with operating pressure, turbine inlet temperature and fuel cell load were studied based on the simulation results. Then the effects of oxygen utilization, fuel utilization, operating temperature and efficiencies of the gas turbine components on the system performance of the RHE cycle and the EGR cycle were discussed in detail. Simulation results indicated that the system optimum efficiency for the EGR air reheating cycle scheme was higher than that of the RHE cycle system. A higher pressure ratio would be available for the EGR cycle system in comparison with the RHE cycle. It was found that increasing fuel utilization or oxygen utilization would decrease fuel cell efficiency but improve the system efficiency for both of the RHE and EGR cycles. The efficiency of the RHE cycle hybrid system decreased as the fuel cell air inlet temperature increased. However, the system efficiency of EGR cycle increased with fuel cell air inlet temperature. The effect of turbine efficiency on the system efficiency was more obvious than the effect of the compressor and recuperator efficiencies among the gas turbine components. It was also indicated that improving the gas turbine component efficiencies for the RHE cycle increased system efficiency higher than that for the EGR cycle.

  2. Gas Core Reactor Numerical Simulation Using a Coupled MHD-MCNP Model

    NASA Technical Reports Server (NTRS)

    Kazeminezhad, F.; Anghaie, S.

    2008-01-01

    Analysis is provided in this report of using two head-on magnetohydrodynamic (MHD) shocks to achieve supercritical nuclear fission in an axially elongated cylinder filled with UF4 gas as an energy source for deep space missions. The motivation for each aspect of the design is explained and supported by theory and numerical simulations. A subsequent report will provide detail on relevant experimental work to validate the concept. Here the focus is on the theory of and simulations for the proposed gas core reactor conceptual design from the onset of shock generations to the supercritical state achieved when the shocks collide. The MHD model is coupled to a standard nuclear code (MCNP) to observe the neutron flux and fission power attributed to the supercritical state brought about by the shock collisions. Throughout the modeling, realistic parameters are used for the initial ambient gaseous state and currents to ensure a resulting supercritical state upon shock collisions.

  3. Reducing California's Greenhouse Gas Emissions through ProductLife-Cycle Optimization

    SciTech Connect

    Masanet, Eric; Price, Lynn; de la Rue du Can, Stephane; Worrell,Ernst

    2005-12-30

    Product life-cycle optimization addresses the reduction ofenvironmental burdens associated with the production, use, andend-of-life stages of a product s life cycle. In this paper, we offer anevaluation of the opportunities related to product life-cycleoptimization in California for two key products: personal computers (PCs)and concrete. For each product, we present the results of an explorativecase study to identify specific opportunities for greenhouse gas (GHG)emissions reductions at each stage of the product life cycle. We thenoffer a discussion of the practical policy options that may exist forrealizing the identified GHG reduction opportunities. The case studiesdemonstrate that there may be significant GHG mitigation options as wellas a number of policy options that could lead to life-cycle GHG emissionsreductions for PCs and concrete in California.

  4. Thermodynamic analysis of liquefied natural gas (LNG) production cycle in APCI process

    NASA Astrophysics Data System (ADS)

    Nezhad, Shahrooz Abbasi; Shabani, Bezhan; Soleimani, Majid

    2012-12-01

    The appropriate production of liquefied natural gas (LNG) with least consuming energy and maximum efficiency is quite important. In this paper, LNG production cycle by means of APCI Process has been studied. Energy equilibrium equations and exergy equilibrium equations of each equipment in the APCI cycle were established. The equipments are described using rigorous thermodynamics and no significant simplification is assumed. Taken some operating parameters as key parameters, influences of these parameters on coefficient of performance (COP) and exergy efficiency of the cascading cycle were analyzed. The results indicate that COP and exergy efficiency will be improved with the increasing of the inlet pressure of MR (mixed refrigerant) compressors, the decreasing of the NG and MR after precooling process, outlet pressure of turbine, inlet temperature of MR compressor and NG temperature after cooling in main cryogenic heat exchanger (MCHE). The COP and exergy efficiency of the APCI cycle will be above 2% and 40%, respectively, after optimizing the key parameters.

  5. Prospective gas turbine and combined-cycle units for power engineering (a Review)

    NASA Astrophysics Data System (ADS)

    Ol'khovskii, G. G.

    2013-02-01

    The modern state of technology for making gas turbines around the world and heat-recovery combined-cycle units constructed on their basis are considered. The progress achieved in this field by Siemens, Mitsubishi, General Electric, and Alstom is analyzed, and the objectives these companies set forth for themselves for the near and more distant future are discussed. The 375-MW gas turbine unit with an efficiency of 40% produced by Siemens, which is presently the largest one, is subjected to a detailed analysis. The main specific features of this turbine are that the gas turbine unit's hot-path components have purely air cooling, due to which the installation has enhanced maneuverability. The single-shaft combined-cycle plant constructed on the basis of this turbine has a capacity of 570 MW and efficiency higher than 60%. Programs adopted by different companies for development of new-generation gas turbine units firing synthesis gas and fitted with low-emission combustion chambers and new cooling systems are considered. Concepts of rotor blades for new gas turbine units with improved thermal barrier coatings and composite blades different parts of which are made of materials selected in accordance with the conditions of their operation are discussed.

  6. Thermo-economic comparative analysis of gas turbine GT10 integrated with air and steam bottoming cycle

    NASA Astrophysics Data System (ADS)

    Czaja, Daniel; Chmielnak, Tadeusz; Lepszy, Sebastian

    2014-12-01

    A thermodynamic and economic analysis of a GT10 gas turbine integrated with the air bottoming cycle is presented. The results are compared to commercially available combined cycle power plants based on the same gas turbine. The systems under analysis have a better chance of competing with steam bottoming cycle configurations in a small range of the power output capacity. The aim of the calculations is to determine the final cost of electricity generated by the gas turbine air bottoming cycle based on a 25 MW GT10 gas turbine with the exhaust gas mass flow rate of about 80 kg/s. The article shows the results of thermodynamic optimization of the selection of the technological structure of gas turbine air bottoming cycle and of a comparative economic analysis. Quantities are determined that have a decisive impact on the considered units profitability and competitiveness compared to the popular technology based on the steam bottoming cycle. The ultimate quantity that can be compared in the calculations is the cost of 1 MWh of electricity. It should be noted that the systems analyzed herein are power plants where electricity is the only generated product. The performed calculations do not take account of any other (potential) revenues from the sale of energy origin certificates. Keywords: Gas turbine air bottoming cycle, Air bottoming cycle, Gas turbine, GT10

  7. Gas and grain chemical composition in cold cores as predicted by the Nautilus 3-phase model

    NASA Astrophysics Data System (ADS)

    Ruaud, Maxime; Wakelam, Valentine; Hersant, Franck

    2016-04-01

    We present an extended version of the 2-phase gas-grain code NAUTILUS to the 3-phase modelling of gas and grain chemistry of cold cores. In this model, both the mantle and the surface are considered as chemically active. We also take into account the competition among reaction, diffusion and evaporation. The model predictions are confronted to ice observations in the envelope of low-mass and massive young stellar objects as well as toward background stars. Modelled gas-phase abundances are compared to species observed toward TMC-1 (CP) and L134N dark clouds. We find that our model successfully reproduces the observed ice species. It is found that the reaction-diffusion competition strongly enhances reactions with barriers and more specifically reactions with H2, which is abundant on grains. This finding highlights the importance to have a good approach to determine the abundance of H2 on grains. Consequently, it is found that the major N-bearing species on grains go from NH3 to N2 and HCN when the reaction-diffusion competition is accounted. In the gas-phase and before few 105 yrs, we find that the 3-phase model does not have a strong impact on the observed species compared to the 2-phase model. After this time, the computed abundances dramatically decrease due to the strong accretion on dust, which is not counterbalanced by the desorption less efficient than in the 2-phase model. This strongly constrains the chemical-age of cold cores to be of the order of few 105 yrs.

  8. 40 CFR 86.110-94 - Exhaust gas sampling system; diesel-cycle vehicles, and Otto-cycle vehicles requiring particulate...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Exhaust gas sampling system; diesel-cycle vehicles, and Otto-cycle vehicles requiring particulate emissions measurements. 86.110-94 Section 86.110-94 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND...

  9. Tubular SOFC and SOFC/gas turbine combined cycle status and prospects

    SciTech Connect

    Veyo, S.E.; Lundberg, W.L.

    1996-12-31

    Presently under fabrication at Westinghouse for a consortium of Dutch and Danish utilities is the world`s first 100 kWe Solid Oxide Fuel Cell (SOFC) power generation system. This natural gas fueled experimental field unit will be installed near Arnhem, Netherlands, at an auxiliary district heating plant. Electrical generation efficiency of this simple cycle atmospheric pressure system will approach 50% [net ac/LHV]. For larger capacity systems, the horizon for the efficiency (atmospheric pressure) is about 55%. Pressurization would increase the efficiency. Objectives of the analyses reported were: (1) to document the improved performance potential of the two shaft turbine cycle given access to a better recuperator and lower lead losses, (2) to assess the performance of PSOFC/GT combined cycles in the 3 MW plant application that are based on use of a simple single shaft gas turbine having a design-point turbine inlet temperature that closely matches the temperature of the SOFC exhaust gas (about 850 C), (3) to estimate the performance potential of smaller combined cycle power plants employing a single SOFC submodule, and (4) to evaluate the cogeneration potential of such systems.

  10. Hybrid life-cycle assessment of natural gas based fuel chains for transportation.

    PubMed

    Strømman, Anders Hammer; Solli, Christian; Hertwich, Edgar G

    2006-04-15

    This research compares the use of natural gas, methanol, and hydrogen as transportation fuels. These three fuel chains start with the extraction and processing of natural gas in the Norwegian North Sea and end with final use in Central Europe. The end use is passenger transportation with a sub-compact car that has an internal combustion engine for the natural gas case and a fuel cell for the methanol and hydrogen cases. The life cycle assessment is performed by combining a process based life-cycle inventory with economic input-output data. The analysis shows that the potential climate impacts are lowest for the hydrogen fuel scenario with CO2 deposition. The hydrogen fuel chain scenario has no significant environmental disadvantage compared to the other fuel chains. Detailed analysis shows that the construction of the car contributes significantly to most impact categories. Finally, it is shown how the application of a hybrid inventory model ensures a more complete inventory description compared to standard process-based life-cycle assessment. This is particularly significant for car construction which would have been significantly underestimated in this study using standard process life-cycle assessment alone. PMID:16683626

  11. The thermodynamic efficiency of the condensing process circuits of binary combined-cycle plants with gas-assisted heating of cycle air

    NASA Astrophysics Data System (ADS)

    Kovalevskii, V. P.

    2011-09-01

    The thermal efficiencies of condensing-type circuits of binary combined-cycle plants containing one, two, and three loops with different pressure levels and equipped with a GTE-160 (V94.2) gas turbine unit, and with preheating of cycle air are analyzed by way of comparison in a wide range of initial steam pressures. The variation of the combined-cycle plant efficiency, stream wetness, conditional overall heating surface of the heat-recovery boiler, and other parameters is presented.

  12. Impacts of Vehicle Weight Reduction via Material Substitution on Life-Cycle Greenhouse Gas Emissions.

    PubMed

    Kelly, Jarod C; Sullivan, John L; Burnham, Andrew; Elgowainy, Amgad

    2015-10-20

    This study examines the vehicle-cycle and vehicle total life-cycle impacts of substituting lightweight materials into vehicles. We determine part-based greenhouse gas (GHG) emission ratios by collecting material substitution data and evaluating that alongside known mass-based GHG ratios (using and updating Argonne National Laboratory's GREET model) associated with material pair substitutions. Several vehicle parts are lightweighted via material substitution, using substitution ratios from a U.S. Department of Energy report, to determine GHG emissions. We then examine fuel-cycle GHG reductions from lightweighting. The fuel reduction value methodology is applied using FRV estimates of 0.15-0.25, and 0.25-0.5 L/(100km·100 kg), with and without powertrain adjustments, respectively. GHG breakeven values are derived for both driving distance and material substitution ratio. While material substitution can reduce vehicle weight, it often increases vehicle-cycle GHGs. It is likely that replacing steel (the dominant vehicle material) with wrought aluminum, carbon fiber reinforced plastic (CRFP), or magnesium will increase vehicle-cycle GHGs. However, lifetime fuel economy benefits often outweigh the vehicle-cycle, resulting in a net total life-cycle GHG benefit. This is the case for steel replaced by wrought aluminum in all assumed cases, and for CFRP and magnesium except for high substitution ratio and low FRV. PMID:26393414

  13. Fuel-cycle greenhouse gas emissions from alternative fuels in Australian heavy vehicles

    NASA Astrophysics Data System (ADS)

    Beer, Tom; Grant, Tim; Williams, David; Watson, Harry

    This paper quantifies the expected pre-combustion and combustion emissions of greenhouse gases from Australian heavy vehicles using alternative fuels. We use the term exbodied emissions for these full fuel-cycle emissions. The fuels examined are low sulfur diesel (LSD), ultra-low sulfur diesel (ULS), compressed natural gas (CNG), liquefied natural gas (LNG), liquefied petroleum gas (LPG), ethanol (from lignocellulose), biodiesel and waste oil. Biodiesel and ethanol have the lowest exbodied greenhouse gas emissions (in grams greenhouse gases per kilometre travelled). Biodiesel reduces exbodied greenhouse gas emissions from 41% to 51% whereas ethanol reduces emissions by 49-55%. In fact, both emit larger quantities of CO 2 than conventional fuels, but as most of the CO 2 is from renewable carbon stocks that fraction is not counted towards the greenhouse gas emissions from the fuel. The gaseous fuels (LPG, CNG) come next with emissions that range from 88% to 92% of diesel. The emissions of greenhouse gases from diesel are reduced if waste oil is used as a diesel extender, but the processing energy required to generate LSD and ULS in Australia increase their greenhouse gas emissions compared to diesel fuel. The extra energy required liquefy and cool LNG means that it has the highest exbodied greenhouse gas emissions of the fuels that were considered.

  14. The study of capability natural uranium as fuel cycle input for long life gas cooled fast reactors with helium as coolant

    NASA Astrophysics Data System (ADS)

    Ariani, Menik; Satya, Octavianus Cakra; Monado, Fiber; Su'ud, Zaki; Sekimoto, Hiroshi

    2016-03-01

    The objective of the present research is to assess the feasibility design of small long-life Gas Cooled Fast Reactor with helium as coolant. GCFR included in the Generation-IV reactor systems are being developed to provide sustainable energy resources that meet future energy demand in a reliable, safe, and proliferation-resistant manner. This reactor can be operated without enrichment and reprocessing forever, once it starts. To obtain the capability of consuming natural uranium as fuel cycle input modified CANDLE burn-up scheme was adopted in this system with different core design. This study has compared the core with three designs of core reactors with the same thermal power 600 MWth. The fuel composition each design was arranged by divided core into several parts of equal volume axially i.e. 6, 8 and 10 parts related to material burn-up history. The fresh natural uranium is initially put in region 1, after one cycle of 10 years of burn-up it is shifted to region 2 and the region 1 is filled by fresh natural uranium fuel. This concept is basically applied to all regions, i.e. shifted the core of the region (i) into region (i+1) region after the end of 10 years burn-up cycle. The calculation results shows that for the burn-up strategy on "Region-8" and "Region-10" core designs, after the reactors start-up the operation furthermore they only needs natural uranium supply to the next life operation until one period of refueling (10 years).

  15. Land-Energy Nexus: Life Cycle Land Use of Natural Gas-Fired Electricity

    NASA Astrophysics Data System (ADS)

    Heath, G.; Jordaan, S.; Macknick, J.; Mohammadi, E.; Ben-Horin, D.; Urrea, V.

    2014-12-01

    Comparisons of the land required for different types of energy are challenging due to the fact that upstream land use of fossil fuel technologies is not well characterized. This research focuses on improving estimates of the life cycle land use of natural gas-fired electricity through the novel combination of inventories of the location of natural gas-related infrastructure, satellite imagery analysis and gas production data. Land area per unit generation is calculated as the sum of natural gas life cycle stages divided by the throughput of natural gas, combined with the land use of the power plant divided by the generation of the power plant. Five natural gas life cycle stages are evaluated for their area: production, gathering, processing, transmission and disposal. The power plant stage is characterized by a thermal efficiency ηth, which converts MegaJoules (MJ) to kilowatt hours (kWh). We focus on seven counties in the Barnett shale region in Texas that represent over 90% of total Barnett Shale gas production. In addition to assessing the gathering and transmission pipeline network, approximately 500 sites are evaluated from the five life cycle stages plus power plants. For instance, assuming a 50 foot right-of-way for transmission pipelines, this part of the Barnett pipeline network occupies nearly 26,000 acres. Site, road and water components to total area are categorized. Methods are developed to scale up sampled results for each component type to the full population of sites within the Barnett. Uncertainty and variability are charaterized. Well-level production data are examined by integrating commercial datasets with advanced methods for quantifying estimated ultimate recovery (EUR) for wells, then summed to estimate natural gas produced in an entire play. Wells that are spatially coincident are merged using ArcGIS. All other sites are normalized by an estimate of gas throughput. Prior land use estimates are used to validate the satellite imagery analysis

  16. Suspended core-shell Pt-PtOx nanostructure for ultrasensitive hydrogen gas sensor

    NASA Astrophysics Data System (ADS)

    Basu, Palash Kr.; Kallatt, Sangeeth; Anumol, Erumpukuthickal A.; Bhat, Navakanta

    2015-06-01

    High sensitivity gas sensors are typically realized using metal catalysts and nanostructured materials, utilizing non-conventional synthesis and processing techniques, incompatible with on-chip integration of sensor arrays. In this work, we report a new device architecture, suspended core-shell Pt-PtOx nanostructure that is fully CMOS-compatible. The device consists of a metal gate core, embedded within a partially suspended semiconductor shell with source and drain contacts in the anchored region. The reduced work function in suspended region, coupled with built-in electric field of metal-semiconductor junction, enables the modulation of drain current, due to room temperature Redox reactions on exposure to gas. The device architecture is validated using Pt-PtO2 suspended nanostructure for sensing H2 down to 200 ppb under room temperature. By exploiting catalytic activity of PtO2, in conjunction with its p-type semiconducting behavior, we demonstrate about two orders of magnitude improvement in sensitivity and limit of detection, compared to the sensors reported in recent literature. Pt thin film, deposited on SiO2, is lithographically patterned and converted into suspended Pt-PtO2 sensor, in a single step isotropic SiO2 etching. An optimum design space for the sensor is elucidated with the initial Pt film thickness ranging between 10 nm and 30 nm, for low power (<5 μW), room temperature operation.

  17. New high efficiency low capital coal fueled combined cycle using existing CFBs and large gas turbines

    SciTech Connect

    Rohrer, J.W.

    1999-07-01

    Advanced Coal Power Technologies (IGCC, PFBII, and HIPPS) despite over two decades of technical development, have seen a disappointing lack of commercial (unsubsidized) utilization. Pulverized coal (PC) steam cycles still dominate because of the intrinsic high capital cost of advanced coal technologies. Recent studies have shown that partial gasification combined cycles yield higher efficiencies than full gasification IGCC cycles. They also show that atmospheric CFB combustors suffer little or no efficiency penalty versus pressurized combustors (and have substantially lower capital costs) because turbine exhaust heat can be fully recovered as the combustion air supply for atmospheric combustors. One new atmospheric partial gasification combined cycle is particularly promising from both a capital cost and efficiency basis. It integrates existing coal atmospheric CFB boiler technology with conventional simple cycle high temperature gas turbines. The CFB boiler also supplies hot bed material to an inexpensive raw coal devolatilizer riser tube which produces a medium-high BTU turbine fuel gas without the need for an expensive power robbing oxygen plant.

  18. Towards the development of rapid screening techniques for shale gas core properties

    NASA Astrophysics Data System (ADS)

    Cave, Mark R.; Vane, Christopher; Kemp, Simon; Harrington, Jon; Cuss, Robert

    2013-04-01

    Shale gas has been produced for many years in the U.S.A. and forms around 8% of total their natural gas production. Recent testing for gas on the Fylde Coast in Lancashire UK suggests there are potentially large reserves which could be exploited. The increasing significance of shale gas has lead to the need for deeper understanding of shale behaviour. There are many factors which govern whether a particular shale will become a shale gas resource and these include: i) Organic matter abundance, type and thermal maturity; ii) Porosity-permeability relationships and pore size distribution; iii) Brittleness and its relationship to mineralogy and rock fabric. Measurements of these properties require sophisticated and time consuming laboratory techniques (Josh et al 2012), whereas rapid screening techniques could provide timely results which could improve the efficiency and cost effectiveness of exploration. In this study, techniques which are portable and provide rapid on-site measurements (X-ray Fluorescence (XRF) and Infra-red (IR) spectroscopy) have been calibrated against standard laboratory techniques (Rock-Eval 6 analyser-Vinci Technologies) and Powder whole-rock XRD analysis was carried out using a PANalytical X'Pert Pro series diffractometer equipped with a cobalt-target tube, X'Celerator detector and operated at 45kV and 40mA, to predict properties of potential shale gas material from core material from the Bowland shale Roosecote, south Cumbria. Preliminary work showed that, amongst various mineralogical and organic matter properties of the core, regression models could be used so that the total organic carbon content could be predicted from the IR spectra with a 95 percentile confidence prediction error of 0.6% organic carbon, the free hydrocarbons could be predicted with a 95 percentile confidence prediction error of 0.6 mgHC/g rock, the bound hydrocarbons could be predicted with a 95 percentile confidence prediction error of 2.4 mgHC/g rock, mica content

  19. Germanium-silicon alloy and core-shell nanocrystals by gas phase synthesis

    NASA Astrophysics Data System (ADS)

    Mehringer, Christian; Kloner, Christian; Butz, Benjamin; Winter, Benjamin; Spiecker, Erdmann; Peukert, Wolfgang

    2015-03-01

    In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into the second reactor stage (HWR II) and a mixture of SiH4 and GeH4 is added. The ratio of the precursors in the feed, their partial pressures, the synthesis temperature in HWR II and the overall pressure are varied depending on the desired morphology and composition. Alloy particle production is achieved in the heterogeneous surface reaction regime, meaning that germanium (Ge) and Si are deposited on the seed surface simultaneously. The NCs can be synthesized with any desired composition, whilst maintaining a mean diameter around 30 nm with a geometric standard deviation (GSD) around 1.25. The absorption behavior and the related fundamental optical band gap energy in dependence on the alloy composition are exemplarily presented. They prove the possibility to tailor NC properties for electronical and opto-electronical applications. In the homogeneous gas phase reaction regime facetted Ge-Si core-shell structures are accessible. The Ge deposition on the seeds precedes the Si deposition due to different gas phase reaction kinetics of the precursors. The Si layer grows epitaxially on the Ge core and is around 5 nm thick.In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into

  20. Melting and metallization of silica in the cores of gas giants, ice giants, and super Earths

    NASA Astrophysics Data System (ADS)

    Mazevet, S.; Tsuchiya, T.; Taniuchi, T.; Benuzzi-Mounaix, A.; Guyot, F.

    2015-07-01

    The physical state and properties of silicates at conditions encountered in the cores of gas giants, ice giants, and of Earth-like exoplanets now discovered with masses up to several times the mass of the Earth remain mostly unknown. Here, we report on theoretical predictions of the properties of silica, SiO2, up to 4 TPa and about 20 000 K by using first principles molecular dynamics simulations based on density functional theory. For conditions found in the super Earths and in ice giants, we show that silica remains a poor electrical conductor up to 10 Mbar due to an increase in the Si-O coordination with pressure. For Jupiter and Saturn cores, we find that MgSiO3 silicate has not only dissociated into MgO and SiO2, as shown in previous studies, but that these two phases have likely differentiated to lead to a core made of liquid SiO2 and solid (Mg,Fe)O.

  1. Core acid treatment influence on well reservoir properties in Kazan oil-gas condensate field

    NASA Astrophysics Data System (ADS)

    Janishevskii, A.; Ezhova, A.

    2015-11-01

    The research involves investigation of the influence of hydrochloric acid (HCI-12%) and mud acid (mixture: HCl - 10% and HF - 3%) treatment on the Upper-Jurassic reservoir properties in Kazan oil-gas condensate field wells. The sample collection included three lots of core cylinders from one and the same depth (all in all 42). Two lots of core cylinders were distributed as following: first lot - reservoir properties were determined, and, then thin sections were cut off from cylinder faces; second lot- core cylinders were exposed to hydrochloric acid treatment, then, after flushing the reservoir properties were determined, and thin sections were prepared. Based on the quantitative petrographic rock analysis, involvin 42 thin sections, the following factors were determined: granulometric mineral composition, cement content, intergranular contacts and pore space structure. According to the comparative analysis of initial samples, the following was determined: content decrease of feldspar, clay and mica fragments, mica, clay and carbonate cement; increase of pore spaces while in the investigated samples- on exposure of rocks to acids effective porosity and permeability value range is ambiguous.

  2. THR-TH: a high-temperature gas-cooled nuclear reactor core thermal hydraulics code

    SciTech Connect

    Vondy, D.R.

    1984-07-01

    The ORNL version of PEBBLE, the (RZ) pebble bed thermal hydraulics code, has been extended for application to a prismatic gas cooled reactor core. The supplemental treatment is of one-dimensional coolant flow in up to a three-dimensional core description. Power density data from a neutronics and exposure calculation are used as the basic information for the thermal hydraulics calculation of heat removal. Two-dimensional neutronics results may be expanded for a three-dimensional hydraulics calculation. The geometric description for the hydraulics problem is the same as used by the neutronics code. A two-dimensional thermal cell model is used to predict temperatures in the fuel channel. The capability is available in the local BOLD VENTURE computation system for reactor core analysis with capability to account for the effect of temperature feedback by nuclear cross section correlation. Some enhancements have also been added to the original code to add pebble bed modeling flexibility and to generate useful auxiliary results. For example, an estimate is made of the distribution of fuel temperatures based on average and extreme conditions regularly calculated at a number of locations.

  3. Effect of multilayer ice chemistry on gas-phase deuteration in starless cores

    NASA Astrophysics Data System (ADS)

    Sipilä, O.; Caselli, P.; Taquet, V.

    2016-06-01

    Context. Astrochemical models commonly used to study the deuterium chemistry in starless cores consider a two-phase approach in which the ice on the dust grains is assumed to be entirely reactive. Recent experimental studies suggest that cold interstellar ices are mostly inert, and a multilayer model distinguishing the chemical processes at the surface and in the ice bulk would be more appropriate. Aims: We investigate whether the multilayer model can be as successful as the bulk model in reproducing the observed abundances of various deuterated gas-phase species toward starless cores. Methods: We calculated abundances for various deuterated species as functions of time using a pseudo-time-dependent chemical model adopting fixed physical conditions. We also estimated abundance gradients in starless cores by adopting a modified Bonnor-Ebert sphere as a core model. In the multilayer ice scenario, we consider desorption from one or several monolayers on the surface. Results: We find that the multilayer model predicts abundances of DCO+ and N2D+ that are about an order of magnitude lower than observed; the difference is caused by the trapping of CO and N2 within the grain mantle. As a result of the mantle trapping, deuteration efficiency in the gas phase increases and we find stronger deuterium fractionation in ammonia than has been observed. Another distinguishing feature of the multilayer model is that becomes the main deuterated ion at high density. The bulk ice model is generally easily reconciled with observations. Conclusions: Our results underline that more theoretical and experimental work is needed to understand the composition and morphology of interstellar ices, and the desorption processes that can act on them. With the current constraints, the bulk ice model appears to reproduce the observations more accurately than the multilayer ice model. According to our results, the abundance ratio of H2D+ to N2D+ is higher than 100 in the multilayer model, while only

  4. Germanium-silicon alloy and core-shell nanocrystals by gas phase synthesis.

    PubMed

    Mehringer, Christian; Kloner, Christian; Butz, Benjamin; Winter, Benjamin; Spiecker, Erdmann; Peukert, Wolfgang

    2015-03-12

    In this work we present a novel route to synthesize well defined germanium-silicon alloy (GexSi1-x) and core-shell nanocrystals (NCs) employing monosilane (SiH4) and monogermane (GeH4) as precursors in a continuously operated two-stage hot-wall aerosol reactor setup. The first hot-wall reactor stage (HWR I) is used to produce silicon (Si) seed particles from SiH4 pyrolysis in Argon (Ar). The resulting seeding aerosol is fed into the second reactor stage (HWR II) and a mixture of SiH4 and GeH4 is added. The ratio of the precursors in the feed, their partial pressures, the synthesis temperature in HWR II and the overall pressure are varied depending on the desired morphology and composition. Alloy particle production is achieved in the heterogeneous surface reaction regime, meaning that germanium (Ge) and Si are deposited on the seed surface simultaneously. The NCs can be synthesized with any desired composition, whilst maintaining a mean diameter around 30 nm with a geometric standard deviation (GSD) around 1.25. The absorption behavior and the related fundamental optical band gap energy in dependence on the alloy composition are exemplarily presented. They prove the possibility to tailor NC properties for electronical and opto-electronical applications. In the homogeneous gas phase reaction regime facetted Ge-Si core-shell structures are accessible. The Ge deposition on the seeds precedes the Si deposition due to different gas phase reaction kinetics of the precursors. The Si layer grows epitaxially on the Ge core and is around 5 nm thick. PMID:25700152

  5. DUST AND HCO{sup +} GAS IN THE STAR-FORMING CORE W3-SE

    SciTech Connect

    Zhu Lei; Zhao Junhui; Wright, M. C. H.; Wu Yuefang

    2010-03-20

    line profile suggest that other kinematics such as outflows within the central 6'' of the core likely dominate the resulting spectrum. The kinematics of the substructures of B and C suggest that the molecular gas outside the main component A appears to be dominated by the bipolar outflow originated from the dust core with a dynamical age of >3 x 10{sup 4} yr. Our analysis, based on the observations at wavelengths from millimeter, submillimeter, to mid-IR, suggest that the molecular core W3-SE hosts a group of newly formed young stars and protostars.

  6. The Tracer Gas Method of Determining the Charging Efficiency of Two-stroke-cycle Diesel Engines

    NASA Technical Reports Server (NTRS)

    Schweitzer, P H; Deluca, Frank, Jr

    1942-01-01

    A convenient method has been developed for determining the scavenging efficiency or the charging efficiency of two-stroke-cycle engines. The method consists of introducing a suitable tracer gas into the inlet air of the running engine and measuring chemically its concentration both in the inlet and exhaust gas. Monomethylamine CH(sub 3)NH(sub 2) was found suitable for the purpose as it burns almost completely during combustion, whereas the "short-circuited" portion does not burn at all and can be determined quantitatively in the exhaust. The method was tested both on four-stroke and on two-stroke engines and is considered accurate within 1 percent.

  7. Determination of cycle configuration of gas turbines and aircraft engines by an optimization procedure

    SciTech Connect

    Tsuijikawa, Y.; Nagaoka, M. )

    1991-01-01

    This paper is devoted to the analyses and optimization of simple and sophisticated cycles, particularly for various gas turbine engines and aero-engines (including the scramjet engine) to achieve maximum performance. The optimization of such criteria as thermal efficiency, specific output, and total performance for gas turbine engines, and overall efficiency, nondimensional thrust, and specific impulse for aero-engines has been performed by the optimization procedure with the multiplier method. Comparison of results with analytical solutions establishes the validity of the optimization procedure.

  8. Solid-Core, Gas-Cooled Reactor for Space and Surface Power

    SciTech Connect

    King, Jeffrey C.; El-Genk, Mohamed S.

    2006-01-20

    The solid-core, gas-cooled, Submersion-Subcritical Safe Space (S and 4) reactor is developed for future space power applications and avoidance of single point failures. The Mo-14%Re reactor core is loaded with uranium nitride fuel in enclosed cavities, cooled by He-30%Xe, and sized to provide 550 kWth for seven years of equivalent full power operation. The beryllium oxide reflector disassembles upon impact on water or soil. In addition to decreasing the reactor and shadow shield mass, Spectral Shift Absorber (SSA) materials added to the reactor core ensure that it remains subcritical in the worst-case submersion accident. With a 0.1 mm thick boron carbide coating on the outside surface of the core block and 0.25 mm thick iridium sleeves around the fuel stacks, the reflector outer diameter is 43.5 cm and the combined reactor and shadow shield mass is 935.1 kg. With 12.5 atom% gadolinium-155 added to the fuel, 2.0 mm diameter gadolinium-155 sesquioxide intersititial pins, and a 0.1 mm thick gadolinium-155 sesquioxide coating, the S and 4 reactor has a slightly smaller reflector outer diameter of 43.0 cm, and a total reactor and shield mass of 901.7 kg. With 8.0 atom% europium-151 added to the fuel, 2.0 mm diameter europium-151 sesquioxide interstitial pins, and a 0.1 mm thick europium-151 sesquioxide coating, the reflector's outer diameter and the total reactor and shield mass are further reduced to 41.5 cm and 869.2 kg, respect0011ive.

  9. Synthesis of core/shell spinel ferrite/carbon nanoparticles with enhanced cycling stability for lithium ion battery anodes

    NASA Astrophysics Data System (ADS)

    Jin, Yun-Ho; Seo, Seung-Deok; Shim, Hyun-Woo; Park, Kyung-Soo; Kim, Dong-Wan

    2012-03-01

    Monodispersed core/shell spinel ferrite/carbon nanoparticles are formed by thermolysis of metal (Fe3+, Co2+) oleates followed by carbon coating. The phase and morphology of nanoparticles are characterized by x-ray diffraction and transmission electron microscopy. Pure Fe3O4 and CoFe2O4 nanoparticles are initially prepared through thermal decomposition of metal-oleate precursors at 310 °C and they are found to exhibit poor electrochemical performance because of the easy aggregation of nanoparticles and the resulting increase in the interparticle contact resistance. In contrast, uniform carbon coating of Fe3O4 and CoFe2O4 nanoparticles by low-temperature (180 °C) decomposition of malic acid allowed each nanoparticle to be electrically wired to a current collector through a conducting percolative path. Core/shell Fe3O4/C and CoFe2O4/C nanocomposite electrodes show a high specific capacity that can exceed 700 mAh g-1 after 200 cycles, along with enhanced cycling stability.

  10. An assessment of the future of closed-cycle gas turbines

    SciTech Connect

    Fejer, A.A.; Khinkis, M.J.; Wurm, J.

    1991-01-01

    The closed-cycle gas turbine (CCGT) has not reached the worldwide level of success that was expected inspite of the strongly desirable features of this concept and the success of several large closed-cycle power plants operating in Western Europe today. However, an assessment of the CCGT's future has recently been made at the Institute of Gas Technology (IGT), and IGT has shown that due to innovative developments in technologies relevant to the development of CCGT's, coupled with worldwide changes in some economic factors, the CCGT could become a successful competitor of other externally fired power plants and also of internal combustion engines, especially in sizes ranging from 200 to 5000 kW. Documentation of data recently published in the technical literature and some recent relevant developments at IGT in the area of combustion, show a promising future for the cost. 13 refs., 4 figs., 1 tab.

  11. Association of menstrual cycle phase with the core components of empathy

    PubMed Central

    Derntl, Birgit; Hack, Ramona L.; Kryspin-Exner, Ilse; Habel, Ute

    2013-01-01

    Evidence has accumulated that emotion recognition performance varies with menstrual cycle phase. However, according to some empathy models, facial affect recognition constitutes only one component of empathic behavior, besides emotional perspective taking and affective responsiveness. It remains unclear whether menstrual cycle phase and thus estradiol and progesterone levels are also associated with the two other empathy constructs. Therefore, we investigated 40 healthy right-handed females, 20 during their follicular phase and 20 during their midluteal phase and compared their performance in three tasks tapping the empathic components as well as self-report data. Salivary hormone levels were obtained and correlated with performance parameters. Subjects were matched for age and education and did not differ in neuropsychological function. Analysis of empathy performance revealed a significant effect of phase in emotion recognition, showing higher accuracy in the follicular group. Regarding affective responsiveness, we observed a significant difference in reaction times, with faster responses for sad and angry stimuli in the midluteal group. No significant group difference emerged for emotional perspective taking. Furthermore, significant correlations between progesterone levels and emotion recognition accuracy and affective responsiveness emerged only in the luteal group. However, groups did not differ in self-reported empathy. Our results indicate that menstrual cycle phase and thus ovarian hormone concentration are differentially related to empathic behavior, particularly emotion recognition and responsiveness to negative situations, with progesterone covarying with both in the luteal phase. PMID:23098806

  12. Association of menstrual cycle phase with the core components of empathy.

    PubMed

    Derntl, Birgit; Hack, Ramona L; Kryspin-Exner, Ilse; Habel, Ute

    2013-01-01

    Evidence has accumulated that emotion recognition performance varies with menstrual cycle phase. However, according to some empathy models, facial affect recognition constitutes only one component of empathic behavior, besides emotional perspective taking and affective responsiveness. It remains unclear whether menstrual cycle phase and thus estradiol and progesterone levels are also associated with the two other empathy constructs. Therefore, we investigated 40 healthy right-handed females, 20 during their follicular phase and 20 during their midluteal phase and compared their performance in three tasks tapping the empathic components as well as self-report data. Salivary hormone levels were obtained and correlated with performance parameters. Subjects were matched for age and education and did not differ in neuropsychological function. Analysis of empathy performance revealed a significant effect of phase in emotion recognition, showing higher accuracy in the follicular group. Regarding affective responsiveness, we observed a significant difference in reaction times, with faster responses for sad and angry stimuli in the midluteal group. No significant group difference emerged for emotional perspective taking. Furthermore, significant correlations between progesterone levels and emotion recognition accuracy and affective responsiveness emerged only in the luteal group. However, groups did not differ in self-reported empathy. Our results indicate that menstrual cycle phase and thus ovarian hormone concentration are differentially related to empathic behavior, particularly emotion recognition and responsiveness to negative situations, with progesterone covarying with both in the luteal phase. PMID:23098806

  13. Using Animations to Study the Formation of Gas Giant Planets via the Core Accretion Model

    NASA Astrophysics Data System (ADS)

    Hubickyj, O.; Lissauer, J. J.; Bodemheimer, P.; D'Angelo, G.

    2009-12-01

    With the ever increasing number of extrasolar planets being discovered (373 as of 8/13/09 quoted by The Extrasolar Planets Encyclopedia: exoplanet.eu) and the recognition of their diverse nature it is very important to understand the formation processes of the gas giant planets. The core accretion model has successfully explained many features of the formation of gas giant planets in the Solar System (Pollack et al. 1996, Hubickyj et al. 2005) and it has provided an explanation of the characteristics of exoplanets. One example is the observed frequency of planets around stars with a high metal content (e.g. Kornet et al. 2005, Valenti and Fischer 2008). Improvements to the input physics to our computer model have resulted in the very important result that gas giant planets (i.e. Jupiter) can form via the core accretion model on a timescale that agrees with observations of protoplanetary disks (Hillenbrand 2008). These observations set the formation time to about 3 to 5 million years. We will present our recent results (Hubickyj et al. 2005,Lissauer et al. 2009) in the form of animations. Our models generate a substantial amount of data. Having published plots of the important values of our study: mass and radius growth, luminosity, and accretion rates as a function of time, we are now ready to study the second tier of information from our recorded data. We examine the energy profiles within the envelope as it evolves, the location and changes of the convective layers, and the location of the mass deposited by the planetesimals in the envelope as the protoplanet evolves. We find that by animating the data we can study the internal processes in the growing envelope of the protoplanet. The qualitative nature of the processes in the protoplanetary envelope is easily discerned in these animations and a deeper insight to the core accretion processes in the gas giant planets is gained. Hillenbrand, L. A. 2008. Disk-dispersal and planet-formation timescales. Physica

  14. A fuel cycle framework for evaluating greenhouse gas emission reduction technology

    SciTech Connect

    Ashton, W.B.; Barns, D.W. ); Bradley, R.A. . Office of Environmental Analysis)

    1990-05-01

    Energy-related greenhouse gas (GHG) emissions arise from a number of fossil fuels, processes and equipment types throughout the full cycle from primary fuel production to end-use. Many technology alternatives are available for reducing emissions based on efficiency improvements, fuel switching to low-emission fuels, GHG removal, and changes in end-use demand. To conduct systematic analysis of how new technologies can be used to alter current emission levels, a conceptual framework helps develop a comprehensive picture of both the primary and secondary impacts of a new technology. This paper describes a broad generic fuel cycle framework which is useful for this purpose. The framework is used for cataloging emission source technologies and for evaluating technology solutions to reduce GHG emissions. It is important to evaluate fuel mix tradeoffs when investigating various technology strategies for emission reductions. For instance, while substituting natural gas for coal or oil in end-use applications to reduce CO{sub 2} emissions, natural gas emissions of methane in the production phase of the fuel cycle may increase. Example uses of the framework are given.

  15. Life Cycle Greenhouse Gas Emissions of Nuclear Electricity Generation: Systematic Review and Harmonization

    SciTech Connect

    Warner, E. S.; Heath, G. A.

    2012-04-01

    A systematic review and harmonization of life cycle assessment (LCA) literature of nuclear electricity generation technologies was performed to determine causes of and, where possible, reduce variability in estimates of life cycle greenhouse gas (GHG) emissions to clarify the state of knowledge and inform decision making. LCA literature indicates that life cycle GHG emissions from nuclear power are a fraction of traditional fossil sources, but the conditions and assumptions under which nuclear power are deployed can have a significant impact on the magnitude of life cycle GHG emissions relative to renewable technologies. Screening 274 references yielded 27 that reported 99 independent estimates of life cycle GHG emissions from light water reactors (LWRs). The published median, interquartile range (IQR), and range for the pool of LWR life cycle GHG emission estimates were 13, 23, and 220 grams of carbon dioxide equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh), respectively. After harmonizing methods to use consistent gross system boundaries and values for several important system parameters, the same statistics were 12, 17, and 110 g CO{sub 2}-eq/kWh, respectively. Harmonization (especially of performance characteristics) clarifies the estimation of central tendency and variability. To explain the remaining variability, several additional, highly influential consequential factors were examined using other methods. These factors included the primary source energy mix, uranium ore grade, and the selected LCA method. For example, a scenario analysis of future global nuclear development examined the effects of a decreasing global uranium market-average ore grade on life cycle GHG emissions. Depending on conditions, median life cycle GHG emissions could be 9 to 110 g CO{sub 2}-eq/kWh by 2050.

  16. Model-data comparison of soil organic oatter cycling: soil core scale

    NASA Astrophysics Data System (ADS)

    Wutzler, Thomas; Reichstein, Markus

    2010-05-01

    Soil organic matter (SOM) cycling is usually modeled as a donor controlled process, most often by first order kinetics. However, evidence of contradition of this donor-paradigm is appearing. One alternative hypothesis is that microbiological consumers of SOM play an important role and need to be taken into account more explicitely. Here we link SOM cycling to the modeling of microbial growth kinetics. We set up a suite of alternative models of microbial growth. Explicitly modelling the cycling of a label across carbon pools allowed to compare the model outputs to data of a soil priming experiment. The experimental data was taken from U. Hamer, & B. Marschner (2002 Journal of Plant Nutrition and Soil Science 165(3)), who incubated several 14C labelled substrates at 20°C in a model system that consisted of sand mixed with lignin for 26 days. Data streams of time series total respiration, respiration from labelled amendment and prior information on model parameters were used to determine the posterior probability density function of the model parameters of each of the model variants and to calculate Bayes-Factors, the ratios of the likelihood of the different model variants. This kind of data and Bayesian analysis is usable to compare model structures adapted to processes that determine the dynamics at this scale: co-limitation of depolymerization of older soil organic matter by both substrate and decomposers, prefererrential substrate usage, activation and deactivation and predation of microbes, and usage of both assimilated carbon and carbon of internal pools for maintenance and growth respiration.

  17. Greenhouse gas emission impacts of electric vehicles under varying driving cycles in various counties and US cities

    SciTech Connect

    Wang, M.Q.; Marr, W.W.

    1994-02-10

    Electric vehicles (EVs) can reduce greenhouse gas emissions, relative to emissions from gasoline-fueled vehicles. However, those studies have not considered all aspects that determine greenhouse gas emissions from both gasoline vehicles (GVs) and EVs. Aspects often overlooked include variations in vehicle trip characteristics, inclusion of all greenhouse gases, and vehicle total fuel cycle. In this paper, we estimate greenhouse gas emission reductions for EVs, including these important aspects. We select four US cities (Boston, Chicago, Los Angeles, and Washington, D.C.) and six countries (Australia, France, Japan, Norway, the United Kingdom, and the United States) and analyze greenhouse emission impacts of EVs in each city or country. We also select six driving cycles developed around the world (i.e., the US federal urban driving cycle, the Economic Community of Europe cycle 15, the Japanese 10-mode cycle, the Los Angeles 92 cycle, the New York City cycle, and the Sydney cycle). Note that we have not analyzed EVs in high-speed driving (e.g., highway driving), where the results would be less favorable to EVs; here, EVs are regarded as urban vehicles only. We choose one specific driving cycle for a given city or country and estimate the energy consumption of four-passenger compact electric and gasoline cars in the given city or country. Finally, we estimate total fuel cycle greenhouse gas emissions of both GVs and EVs by accounting for emissions from primary energy recovery, transportation, and processing; energy product transportation; and powerplant and vehicle operations.

  18. Measurements of gas sorption from seawater and the influence of gas release on open-cycle ocean thermal energy conversion (OC-OTEC) system performance

    SciTech Connect

    Penney, T R; Althof, J A

    1985-06-01

    The technical community has questioned the validity and cost-effectiveness of open-cycle ocean thermal energy conversion (OC-OTEC) systems because of the unknown effect of noncondensable gas on heat exchanger performance and the power needed to run vacuum equipment to remove this gas. To date, studies of seawater gas desorption have not been prototypical for system level analysis. This study gives preliminary gas desorption data on a vertical spout, direct contact evaporator and multiple condenser geometries. Results indicate that dissolved gas can be substantially removed before the seawater enters the heat exchange process, reducing the uncertainty and effect of inert gas on heat exchanger performance.

  19. Herschel observations of extended atomic gas in the core of the Perseus cluster

    NASA Astrophysics Data System (ADS)

    Mittal, Rupal; Oonk, J. B. Raymond; Ferland, Gary J.; Edge, Alastair C.; O'Dea, Christopher P.; Baum, Stefi A.; Whelan, John T.; Johnstone, Roderick M.; Combes, Francoise; Salomé, Philippe; Fabian, Andy C.; Tremblay, Grant R.; Donahue, Megan; Russell, Helen

    2012-11-01

    We present Herschel observations of the core of the Perseus cluster of galaxies. Especially intriguing is the network of filaments that surround the brightest cluster galaxy, NGC 1275, previously imaged extensively in Hα and CO. In this work, we report detections of far-infrared (FIR) lines, in particular, [C II] 158, [O I] 63, [N II] 122, [O IB] 145 and [O III] 88 μm, with Herschel. All lines are spatially extended, except [O III], with the [C II] line emission extending up to 25 kpc from the core. [C II] emission is found to be co-spatial with Hα and CO. Furthermore, [C II] shows a similar velocity distribution to CO, which has been shown in previous studies to display a close association with the Hα kinematics. The spatial and kinematical correlation among [C II], Hα and CO gives us confidence to model the different components of the gas with a common heating model. With the help of FIR continuum Herschel measurements, together with a suite of coeval radio, sub-millimetre and IR data from other observatories, we performed a spectral energy distribution fitting of NGC 1275 using a model that contains contributions from dust emission as well as synchrotron active galactic nucleus emission. This has allowed us to accurately estimate the dust parameters. The data indicate a low dust emissivity index, β ≈ 1, a total dust mass close to 107 M⊙, a cold dust component with temperature 38 ± 2 K and a warm dust component with temperature 116 ± 9 K. The FIR-derived star formation rate is 24 ± 1 M⊙ yr-1, which is in agreement with the far-ultraviolet-derived star formation rate in the core, determined after applying corrections for both Galactic and internal reddening. The total IR luminosity in the range 8-1000 μm is inferred to be 1.5 × 1011 L⊙, making NGC 1275 a luminous IR galaxy. We investigated in detail the source of the Herschel FIR and Hα emissions emerging from a core region 4 kpc in radius. Based on simulations conducted using the radiative

  20. The high density phase of the k-NN hard core lattice gas model

    NASA Astrophysics Data System (ADS)

    Nath, Trisha; Rajesh, R.

    2016-07-01

    The k-NN hard core lattice gas model on a square lattice, in which the first k next nearest neighbor sites of a particle are excluded from being occupied by another particle, is the lattice version of the hard disc model in two dimensional continuum. It has been conjectured that the lattice model, like its continuum counterpart, will show multiple entropy-driven transitions with increasing density if the high density phase has columnar or striped order. Here, we determine the nature of the phase at full packing for k up to 820 302 . We show that there are only eighteen values of k, all less than k  =  4134, that show columnar order, while the others show solid-like sublattice order.

  1. Supercontinuum up-conversion via molecular modulation in gas-filled hollow-core PCF.

    PubMed

    Bauerschmidt, S T; Novoa, D; Trabold, B M; Abdolvand, A; Russell, P St J

    2014-08-25

    We report on the efficient, tunable, and selective frequency up-conversion of a supercontinuum spectrum via molecular modulation in a hydrogen-filled hollow-core photonic crystal fiber. The vibrational Q(1) Raman transition of hydrogen is excited in the fiber by a pump pre-pulse, enabling the excitation of a synchronous, collective oscillation of the molecules. This coherence wave is then used to up-shift the frequency of an arbitrarily weak, delayed probe pulse. Perfect phase-matching for this process is achieved by using higher order fiber modes and adjusting the pressure of the filling gas. Conversion efficiencies of ~50% are obtained within a tuning range of 25 THz. PMID:25321261

  2. Instabilities in uranium plasma and the gas-core nuclear rocket engine

    NASA Technical Reports Server (NTRS)

    Tidman, D. A.

    1972-01-01

    The nonlinear evolution of unstable sound waves in a uranium plasma has been calculated using a multiple time-scale asymptotic expansion scheme. The fluid equations used include the fission power density, radiation diffusion, and the effects of the changing degree of ionization of the uranium atoms. The nonlinear growth of unstable waves is shown to be limited by mode coupling to shorter wavelength waves which are damped by radiation diffusion. This mechanism limits the wave pressure fluctuations to values of order delta P/P approximates 0.00001 in the plasma of a typical gas-core nuclear rocket engine. The instability is thus not expected to present a control problem for this engine.

  3. HTGR-GT closed-cycle gas turbine: a plant concept with inherent cogeneration (power plus heat production) capability

    SciTech Connect

    McDonald, C.F.

    1980-04-01

    The high-grade sensible heat rejection characteristic of the high-temperature gas-cooled reactor-gas turbine (HTGR-GT) plant is ideally suited to cogeneration. Cogeneration in this nuclear closed-cycle plant could include (1) bottoming Rankine cycle, (2) hot water or process steam production, (3) desalination, and (4) urban and industrial district heating. This paper discusses the HTGR-GT plant thermodynamic cycles, design features, and potential applications for the cogeneration operation modes. This paper concludes that the HTGR-GT plant, which can potentially approach a 50% overall efficiency in a combined cycle mode, can significantly aid national energy goals, particularly resource conservation.

  4. Gas-aerosol cycling of ammonia and nitric acid in The Netherlands

    NASA Astrophysics Data System (ADS)

    Roelofs, Geert-Jan; Derksen, Jeroen

    2010-05-01

    Atmospheric ammonia and nitric acid are present over NW Europe in large abundance. Observations made during the IMPACT measurement campaign (May 2008, Cabauw, The Netherlands) show a pronounced diurnal cycle of aerosol ammonium and nitrate on relatively dry days. Simultaneously, AERONET data show a distinct diurnal cycle in aerosol optical thickness (AOT). We used a global aerosol-climate model (ECHAM5-HAM) and a detailed aerosol-cloud column model to help analyse the observations from this period. The study shows that the diurnal cycle in AOT is partly associated with particle number concentration, with distinct peaks in the morning and evening. More important is relative humidity (RH). RH maximizes in the night and early morning, decreases during the morning and increases again in the evening. The particle wet radius, and therefore AOT, changes accordingly. In addition, the RH variability also influences chemistry associated with ammonia and nitric acid (formation of ammonium nitrate, dissolution in aerosol water), resulting in the observed diurnal cycle of aerosol ammonium and nitrate. The additional aerosol matter increases the hygroscopicity of the particles, and this leads to further swelling by water vapor condensation and a further increase of AOT. During the day, as RH decreases and the particles shrink, aerosol ammonium and nitrate are again partly expelled to the gas phase. This behaviour contributes significantly to the observed diurnal cycle in AOT, and it illustrates the complexity of using AOT as a proxy for aerosol concentrations in aerosol climate studies in the case of heavily polluted areas.

  5. Policy implications of uncertainty in modeled life-cycle greenhouse gas emissions of biofuels.

    PubMed

    Mullins, Kimberley A; Griffin, W Michael; Matthews, H Scott

    2011-01-01

    Biofuels have received legislative support recently in California's Low-Carbon Fuel Standard and the Federal Energy Independence and Security Act. Both present new fuel types, but neither provides methodological guidelines for dealing with the inherent uncertainty in evaluating their potential life-cycle greenhouse gas emissions. Emissions reductions are based on point estimates only. This work demonstrates the use of Monte Carlo simulation to estimate life-cycle emissions distributions from ethanol and butanol from corn or switchgrass. Life-cycle emissions distributions for each feedstock and fuel pairing modeled span an order of magnitude or more. Using a streamlined life-cycle assessment, corn ethanol emissions range from 50 to 250 g CO(2)e/MJ, for example, and each feedstock-fuel pathway studied shows some probability of greater emissions than a distribution for gasoline. Potential GHG emissions reductions from displacing fossil fuels with biofuels are difficult to forecast given this high degree of uncertainty in life-cycle emissions. This uncertainty is driven by the importance and uncertainty of indirect land use change emissions. Incorporating uncertainty in the decision making process can illuminate the risks of policy failure (e.g., increased emissions), and a calculated risk of failure due to uncertainty can be used to inform more appropriate reduction targets in future biofuel policies. PMID:21121672

  6. Life Cycle Greenhouse Gas Emissions of Coal-Fired Electricity Generation: Systematic Review and Harmonization

    SciTech Connect

    Whitaker, M.; Heath, G. A.; O'Donoughue, P.; Vorum, M.

    2012-04-01

    This systematic review and harmonization of life cycle assessments (LCAs) of utility-scale coal-fired electricity generation systems focuses on reducing variability and clarifying central tendencies in estimates of life cycle greenhouse gas (GHG) emissions. Screening 270 references for quality LCA methods, transparency, and completeness yielded 53 that reported 164 estimates of life cycle GHG emissions. These estimates for subcritical pulverized, integrated gasification combined cycle, fluidized bed, and supercritical pulverized coal combustion technologies vary from 675 to 1,689 grams CO{sub 2}-equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh) (interquartile range [IQR]= 890-1,130 g CO{sub 2}-eq/kWh; median = 1,001) leading to confusion over reasonable estimates of life cycle GHG emissions from coal-fired electricity generation. By adjusting published estimates to common gross system boundaries and consistent values for key operational input parameters (most importantly, combustion carbon dioxide emission factor [CEF]), the meta-analytical process called harmonization clarifies the existing literature in ways useful for decision makers and analysts by significantly reducing the variability of estimates ({approx}53% in IQR magnitude) while maintaining a nearly constant central tendency ({approx}2.2% in median). Life cycle GHG emissions of a specific power plant depend on many factors and can differ from the generic estimates generated by the harmonization approach, but the tightness of distribution of harmonized estimates across several key coal combustion technologies implies, for some purposes, first-order estimates of life cycle GHG emissions could be based on knowledge of the technology type, coal mine emissions, thermal efficiency, and CEF alone without requiring full LCAs. Areas where new research is necessary to ensure accuracy are also discussed.

  7. Characterization of gas hydrate reservoirs by integration of core and log data in the Ulleung Basin, East Sea

    USGS Publications Warehouse

    Bahk, J.-J.; Kim, G.-Y.; Chun, J.-H.; Kim, J.-H.; Lee, J.Y.; Ryu, B.-J.; Lee, J.-H.; Son, B.-K.; Collett, Timothy S.

    2013-01-01

    Examinations of core and well-log data from the Second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) drill sites suggest that Sites UBGH2-2_2 and UBGH2-6 have relatively good gas hydrate reservoir quality in terms of individual and total cumulative thicknesses of gas-hydrate-bearing sand (HYBS) beds. In both of the sites, core sediments are generally dominated by hemipelagic muds which are intercalated with turbidite sands. The turbidite sands are usually thin-to-medium bedded and mainly consist of well sorted coarse silt to fine sand. Anomalies in infrared core temperatures and porewater chlorinity data and pressure core measurements indicate that “gas hydrate occurrence zones” (GHOZ) are present about 68–155 mbsf at Site UBGH2-2_2 and 110–155 mbsf at Site UBGH2-6. In both the GHOZ, gas hydrates are preferentially associated with many of the turbidite sands as “pore-filling” type hydrates. The HYBS identified in the cores from Site UBGH2-6 are medium-to-thick bedded particularly in the lower part of the GHOZ and well coincident with significant high excursions in all of the resistivity, density, and velocity logs. Gas-hydrate saturations in the HYBS range from 12% to 79% with an average of 52% based on pore-water chlorinity. In contrast, the HYBS from Site UBGH2-2_2 are usually thin-bedded and show poor correlations with both of the resistivity and velocity logs owing to volume averaging effects of the logging tools on the thin HYBS beds. Gas-hydrate saturations in the HYBS range from 15% to 65% with an average of 37% based on pore-water chlorinity. In both of the sites, large fluctuations in biogenic opal contents have significant effects on the sediment physical properties, resulting in limited usage of gamma ray and density logs in discriminating sand reservoirs.

  8. Effect of different agronomic practises on greenhouse gas emissions, especially N2O and nutrient cycling

    NASA Astrophysics Data System (ADS)

    Koal, Philipp; Schilling, Rolf; Gerl, Georg; Pritsch, Karin; Munch, Jean Charles

    2014-05-01

    In order to achieve a reduction of greenhouse gas emissions, management practises need to be adapted by implementing sustainable land use. At first, reliable field data are required to assess the effect of different farming practises on greenhouse gas budgets. The conducted field experiment covers and compares two main aspects of agricultural management, namely an organic farming system and an integrated farming system, implementing additionally the effects of diverse tillage systems and fertilisation practises. Furthermore, the analysis of the alterable biological, physical and chemical soil properties enables a link between the impact of different management systems on greenhouse gas emissions and the monitored cycle of matter, especially the nitrogen cycle. Measurements were carried out on long-term field trials at the Research Farm Scheyern located in a Tertiary hilly landscape approximately 40 km north of Munich (South Germany). The long-term field trials of the organic and integrated farming system were started in 1992. Since then, parcels in a field (each around 0,2-0,4 ha) with a particular interior plot set-up have been conducted. So the 20 years impacts of different tillage and fertilisation practises on soil properties including trace gases were examined. Fluxes of CH4, N2O and CO2 are monitored since 2007 for the integrated farming system trial and since 2012 for the organic farming system trial using an automated system which consists of chambers (per point: 4 chambers, each covering 0,4 m2 area) with a motor-driven lid, an automated gas sampling unit, an on-line gas chromatographic analysis system, and a control and data logging unit (Flessa et al. 2002). Each chamber is sampled 3-4 times in 24 hours. The main outcomes are the analysis of temporal and spatial dynamics of greenhouse gas fluxes as influenced by management practice events (fertilisation and tillage) and weather effects (drying-rewetting, freezing-thawing, intense rainfall and dry periods

  9. Recovery Act: Johnston Rhode Island Combined Cycle Electric Generating Plant Fueled by Waste Landfill Gas

    SciTech Connect

    Galowitz, Stephen

    2013-06-30

    The primary objective of the Project was to maximize the productive use of the substantial quantities of waste landfill gas generated and collected at the Central Landfill in Johnston, Rhode Island. An extensive analysis was conducted and it was determined that utilization of the waste gas for power generation in a combustion turbine combined cycle facility was the highest and best use. The resulting project reflected a cost effective balance of the following specific sub-objectives. 1) Meet environmental and regulatory requirements, particularly the compliance obligations imposed on the landfill to collect, process and destroy landfill gas. 2) Utilize proven and reliable technology and equipment. 3) Maximize electrical efficiency. 4) Maximize electric generating capacity, consistent with the anticipated quantities of landfill gas generated and collected at the Central Landfill. 5) Maximize equipment uptime. 6) Minimize water consumption. 7) Minimize post-combustion emissions. To achieve the Project Objective the project consisted of several components. 1) The landfill gas collection system was modified and upgraded. 2) A State-of-the Art gas clean up and compression facility was constructed. 3) A high pressure pipeline was constructed to convey cleaned landfill gas from the clean-up and compression facility to the power plant. 4) A combined cycle electric generating facility was constructed consisting of combustion turbine generator sets, heat recovery steam generators and a steam turbine. 5) The voltage of the electricity produced was increased at a newly constructed transformer/substation and the electricity was delivered to the local transmission system. The Project produced a myriad of beneficial impacts. 1) The Project created 453 FTE construction and manufacturing jobs and 25 FTE permanent jobs associated with the operation and maintenance of the plant and equipment. 2) By combining state-of-the-art gas clean up systems with post combustion emissions control

  10. Size-controlled, magnetic, and core-shell nanoparticles synthesized by inert-gas condensation

    NASA Astrophysics Data System (ADS)

    Koten, Mark A.

    Interest in nanoparticles (2 to 100 nm in diameter) and clusters of atoms (0.5 to 2 nm in diameter) has heightened over the past two and a half decades on both fundamental and functional levels. Nanoparticles and clusters of atoms are an exciting branch of materials science because they do not behave like normal bulk matter, nor do they act like molecules. They can have shockingly different physical, chemical, optical, or magnetic properties from the same material at a larger scale. In the case of nanoparticles, the surface-to-volume ratio can change fundamental properties like melting temperature, binding energy, or electron affinity. The definitions of markers used to distinguish between metallic, semiconducting, and insulating bulk condensed matter, such as the band gap and polarizability, can even be blurred or confused on the nanoscale. Similarly, clusters of atoms can form in structures that are only stable at finite sizes, and do not translate to bulk condensed matter. Thermodynamics of finite systems changes dramatically in nanovolumes such as wires, rods, cubes, and spheres, which can lead to complex core-shell and onion-like nanostructures. Consequently, these changes in properties and structure have led to many new possibilities in the field of materials engineering. Inert-gas condensation (IGC) is a well-established method of producing nanoparticles that condense from the gas phase. Its first use dates back to the early 1990s, and it has been used to fabricate nanoparticles both commercially and in research and development for applications in magnetism, biomedicine, and catalysts. In this dissertation, IGC was used to produce a wide variety of nanoparticles. First, control over the size distributions of Cu nanoparticles and how it relates to the plasma properties inside the nucleation chamber was investigated. Next, the formation of phase pure WFe2 nanoparticles revealed that this Laves phase is ferromagnetic instead of non-magnetic. Finally, core

  11. [Raman Signal Enhancement for Gas Detection Using a Hollow Core Optical Fiber].

    PubMed

    Guo, Jin-jia; Yang, De-wang; Liu, Chun-hao

    2016-01-01

    Raman spectroscopy has been widely used for gas detection due to the advantages of simultaneous multiple species recognition, rapid analysis, and no sample preparation, etc. Low sensitivity is still a great limitation for Raman application. In this work a Raman system based on a hollow core optical fiber (HCOF) was built and the detection sensitivity for the gas was significantly improved. Also a comparison was carried out between the HCOF Raman system and back-scattering Raman system. The obtained results indicated that the HCOF Raman system could well enhance the signal while also for the background and noise. Using HCOF system, 60 folds signal enhancement was achieved with SNR improvement of 6 times for the N2 and O2 in air when comparing to the back-scattering system. While for the same signal intensity, with HCOF system the exposure time was well shortened to 1/60 and the noise was decreased to 1/2 than the back-scattering system. PMID:27228748

  12. Geochemistry of drill core headspace gases and its significance in gas hydrate drilling in Qilian Mountain permafrost

    NASA Astrophysics Data System (ADS)

    Lu, Zhengquan; Rao, Zhu; He, Jiaxiong; Zhu, Youhai; Zhang, Yongqin; Liu, Hui; Wang, Ting; Xue, Xiaohua

    2015-02-01

    Headspace gases from cores are sampled in the gas hydrate drilling well DK-8 in the Qilian Mountain permafrost. Gas components and carbon isotopes of methane from headspace gas samples are analyzed. The geochemical features of the headspace gases along the well profile are compared with occurrences of gas hydrate, and with the distribution of faults or fractures. Their geochemical significance is finally pointed out in gas hydrate occurrences and hydrocarbon migration. Results show high levels of hydrocarbon concentrations in the headspace gases at depths of 149-167 m, 228-299 m, 321-337 m and 360-380 m. Visible gas hydrate and its associated anomalies occur at 149-167 m and 228-299 m; the occurrence of high gas concentrations in core headspace gases was correlated to gas hydrate occurrences and their associated anomalies, especially in the shallow layers. Gas compositions, gas ratios of C1/ΣC1-5, C1/(C2 + C3), iC4/nC4, and iC5/nC5, and carbon isotopic compositions of methane (δ13C1, PDB‰) indicate that the headspace gases are mainly thermogenic, partly mixed with biodegraded thermogenic sources with small amounts derived from microbial sources. Faults or fracture zones are identified at intervals of 149-167 m, 228-299 m, 321-337 m, and near 360-380 m; significantly higher gas concentrations and lower dryness ratio were found in the headspace gases within the fault or fracture zones compared with areas above these zones. In the shallow zones, low dryness ratios were observed in headspace gases in zones where gas hydrate and faults or fracture zones were found, suggesting that faults or fracture zones serve as migration paths for gases in the deep layers and provide accumulation space for gas hydrate in the shallow layers of the Qilian Mountain permafrost.

  13. Generation of few-cycle laser pulses: Comparison between atomic and molecular gases in a hollow-core fiber

    NASA Astrophysics Data System (ADS)

    Zhi-Yuan, Huang; Ye, Dai; Rui-Rui, Zhao; Ding, Wang; Yu-Xin, Leng

    2016-07-01

    We numerically study the pulse compression approaches based on atomic or molecular gases in a hollow-core fiber. From the perspective of self-phase modulation (SPM), we give the extensive study of the SPM influence on a probe pulse with molecular phase modulation (MPM) effect. By comparing the two compression methods, we summarize their advantages and drawbacks to obtain the few-cycle pulses with micro- or millijoule energies. It is also shown that the double pump-probe approach can be used as a tunable dual-color source by adjusting the time delay between pump and probe pulses to proper values. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204328, 61221064, 61078037, 11127901, 11134010, and 61205208), the National Basic Research Program of China (Grant No. 2011CB808101), and the Natural Science Foundation of Shanghai, China (Grant No. 13ZR1414800).

  14. Casting core for a cooling arrangement for a gas turbine component

    DOEpatents

    Lee, Ching-Pang; Heneveld, Benjamin E

    2015-01-20

    A ceramic casting core, including: a plurality of rows (162, 166, 168) of gaps (164), each gap (164) defining an airfoil shape; interstitial core material (172) that defines and separates adjacent gaps (164) in each row (162, 166, 168); and connecting core material (178) that connects adjacent rows (170, 174, 176) of interstitial core material (172). Ends of interstitial core material (172) in one row (170, 174, 176) align with ends of interstitial core material (172) in an adjacent row (170, 174, 176) to form a plurality of continuous and serpentine shaped structures each including interstitial core material (172) from at least two adjacent rows (170, 174, 176) and connecting core material (178).

  15. Life-cycle assessment of diesel, natural gas and hydrogen fuel cell bus transportation systems

    NASA Astrophysics Data System (ADS)

    Ally, Jamie; Pryor, Trevor

    The Sustainable Transport Energy Programme (STEP) is an initiative of the Government of Western Australia, to explore hydrogen fuel cell technology as an alternative to the existing diesel and natural gas public transit infrastructure in Perth. This project includes three buses manufactured by DaimlerChrysler with Ballard fuel cell power sources operating in regular service alongside the existing natural gas and diesel bus fleets. The life-cycle assessment (LCA) of the fuel cell bus trial in Perth determines the overall environmental footprint and energy demand by studying all phases of the complete transportation system, including the hydrogen infrastructure, bus manufacturing, operation, and end-of-life disposal. The LCAs of the existing diesel and natural gas transportation systems are developed in parallel. The findings show that the trial is competitive with the diesel and natural gas bus systems in terms of global warming potential and eutrophication. Emissions that contribute to acidification and photochemical ozone are greater for the fuel cell buses. Scenario analysis quantifies the improvements that can be expected in future generations of fuel cell vehicles and shows that a reduction of greater than 50% is achievable in the greenhouse gas, photochemical ozone creation and primary energy demand impact categories.

  16. Process analysis of CO{sub 2} capture from flue gas using carbonation/calcination cycles

    SciTech Connect

    Li, Z.S.; Cai, N.S.; Croiset, E.

    2008-07-15

    Process analysis of CO{sub 2} capture from flue gas using Ca-based carbonation/calcination cycles is presented here. A carbonation/calcination system is composed essentially of two reactors (an absorber and a regenerator) with Ca-based sorbent circulating between the two reactors (assumed here as fluidized beds). CO{sub 2} is, therefore, transferred from the absorber to the regenerator. Because of the endothermicity of the calcination reaction, a certain amount of coal is burned with pure oxygen in the regenerator. Detailed mass balance, heat balance and cost of electricity and CO{sub 2} mitigation for the carbonation/calcination cycles with three Ca-based sorbents in dual fluidized beds were calculated and analyzed to study the effect of the Ca-based sorbent activity decay on CO{sub 2} capture from flue gas. The three sorbents considered were: limestone, dolomite and CaO/Ca{sub 12}Al{sub 14}O{sub 33} (75/25 wt %) sorbent. All results, including the amount of coal and oxygen required, are presented with respect to the difference in calcium oxide conversion between the absorber and the regenerator, which is an important design parameter. Finally, costs of electricity and CO{sub 2} mitigation costs using carbonation/calcination cycles for the three sorbents were estimated. The results indicate that the economics of the carbonation/calcination process compare favorably with competing technologies for capturing CO{sub 2}.

  17. Life cycle greenhouse gas emissions from U.S. liquefied natural gas exports: implications for end uses.

    PubMed

    Abrahams, Leslie S; Samaras, Constantine; Griffin, W Michael; Matthews, H Scott

    2015-03-01

    This study analyzes how incremental U.S. liquefied natural gas (LNG) exports affect global greenhouse gas (GHG) emissions. We find that exported U.S. LNG has mean precombustion emissions of 37 g CO2-equiv/MJ when regasified in Europe and Asia. Shipping emissions of LNG exported from U.S. ports to Asian and European markets account for only 3.5-5.5% of precombustion life cycle emissions, hence shipping distance is not a major driver of GHGs. A scenario-based analysis addressing how potential end uses (electricity and industrial heating) and displacement of existing fuels (coal and Russian natural gas) affect GHG emissions shows the mean emissions for electricity generation using U.S. exported LNG were 655 g CO2-equiv/kWh (with a 90% confidence interval of 562-770), an 11% increase over U.S. natural gas electricity generation. Mean emissions from industrial heating were 104 g CO2-equiv/MJ (90% CI: 87-123). By displacing coal, LNG saves 550 g CO2-equiv per kWh of electricity and 20 g per MJ of heat. LNG saves GHGs under upstream fugitive emissions rates up to 9% and 5% for electricity and heating, respectively. GHG reductions were found if Russian pipeline natural gas was displaced for electricity and heating use regardless of GWP, as long as U.S. fugitive emission rates remain below the estimated 5-7% rate of Russian gas. However, from a country specific carbon accounting perspective, there is an imbalance in accrued social costs and benefits. Assuming a mean social cost of carbon of $49/metric ton, mean global savings from U.S. LNG displacement of coal for electricity generation are $1.50 per thousand cubic feet (Mcf) of gaseous natural gas exported as LNG ($.028/kWh). Conversely, the U.S. carbon cost of exporting the LNG is $1.80/Mcf ($.013/kWh), or $0.50-$5.50/Mcf across the range of potential discount rates. This spatial shift in embodied carbon emissions is important to consider in national interest estimates for LNG exports. PMID:25650513

  18. The relationship between gas hydrate saturation and P-wave velocity of pressure cores obtained in the Eastern Nankai Trough

    NASA Astrophysics Data System (ADS)

    Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Fujii, T.; Nagao, J.

    2014-12-01

    P-wave velocity is an important parameter to estimate gas hydrate saturation in sediments. In this study, the relationship between gas hydrate saturation and P-wave velocity have been analyzed using natural hydrate-bearing-sediments obtained in the Eastern Nankai Trough, Japan. The sediment samples were collected by the Hybrid Pressure Coring System developed by Japan Agency for Marine-Earth Science and Technology during June-July 2012, aboard the deep sea drilling vessel CHIKYU. P-wave velocity was measured on board by the Pressure Core Analysis and Transfer System developed by Geotek Ltd. The samples were maintained at a near in-situ pressure condition during coring and measurement. After the measurement, the samples were stored core storage chambers and transported to MHRC under pressure. The samples were manipulated and cut by the Pressure-core Non-destructive Analysis Tools or PNATs developed by MHRC. The cutting sections were determined on the basis of P-wave velocity and visual observations through an acrylic window equipped in the PNATs. The cut samples were depressurized to measure gas volume for saturation calculations. It was found that P-wave velocity correlates well with hydrate saturation and can be reproduced by the hydrate frame component model. Using pressure cores and pressure core analysis technology, nondestructive and near in-situ correlation between gas hydrate saturation and P-wave velocity can be obtained. This study was supported by funding from the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI), Japan.

  19. Life-cycle-assessment of fuel-cells-based landfill-gas energy conversion technologies

    NASA Astrophysics Data System (ADS)

    Lunghi, P.; Bove, R.; Desideri, U.

    Landfill-gas (LFG) is produced as result of the biological reaction of municipal solid waste (MSW). This gas contains about 50% of methane, therefore it cannot be released into the atmosphere as it is because of its greenhouse effect consequences. The high percentage of methane encouraged researchers to find solutions to recover the related energy content for electric energy production. The most common technologies used at the present time are internal combustion reciprocating engines and gas turbines. High conversion efficiency guaranteed by fuel cells (FCs) enable to enhance the energy recovery process and to reduce emissions to air, such as NO x and CO. In any case, in order to investigate the environmental advantages associated with the electric energy generation using fuel cells, it is imperative to consider the whole "life cycle" of the system, "from cradle-to-grave". In fact, fuel cells are considered to be zero-emission devices, but, for example, emissions associated with their manufacture or for hydrogen production must be considered in order to evaluate all impacts on the environment. In the present work a molten carbonate fuel cell (MCFC) system for LFG recovery is considered and a life cycle assessment (LCA) is conducted for an evaluation of environmental consequences and to provide a guide for further environmental impact reduction.

  20. MIGRATION AND GROWTH OF PROTOPLANETARY EMBRYOS. II. EMERGENCE OF PROTO-GAS-GIANT CORES VERSUS SUPER EARTH PROGENITORS

    SciTech Connect

    Liu, Beibei; Zhang, Xiaojia; Lin, Douglas N. C.; Aarseth, Sverre J.

    2015-01-01

    Nearly 15%-20% of solar type stars contain one or more gas giant planets. According to the core-accretion scenario, the acquisition of their gaseous envelope must be preceded by the formation of super-critical cores with masses 10 times or larger than that of the Earth. It is natural to link the formation probability of gas giant planets with the supply of gases and solids in their natal disks. However, a much richer population of super Earths suggests that (1) there is no shortage of planetary building block material, (2) a gas giant's growth barrier is probably associated with whether it can merge into super-critical cores, and (3) super Earths are probably failed cores that did not attain sufficient mass to initiate efficient accretion of gas before it is severely depleted. Here we construct a model based on the hypothesis that protoplanetary embryos migrated extensively before they were assembled into bona fide planets. We construct a Hermite-Embryo code based on a unified viscous-irradiation disk model and a prescription for the embryo-disk tidal interaction. This code is used to simulate the convergent migration of embryos, and their close encounters and coagulation. Around the progenitors of solar-type stars, the progenitor super-critical-mass cores of gas giant planets primarily form in protostellar disks with relatively high (≳ 10{sup –7} M {sub ☉} yr{sup –1}) mass accretion rates, whereas systems of super Earths (failed cores) are more likely to emerge out of natal disks with modest mass accretion rates, due to the mean motion resonance barrier and retention efficiency.

  1. Migration and Growth of Protoplanetary Embryos. II. Emergence of Proto-Gas-Giant Cores versus Super Earth Progenitors

    NASA Astrophysics Data System (ADS)

    Liu, Beibei; Zhang, Xiaojia; Lin, Douglas N. C.; Aarseth, Sverre J.

    2015-01-01

    Nearly 15%-20% of solar type stars contain one or more gas giant planets. According to the core-accretion scenario, the acquisition of their gaseous envelope must be preceded by the formation of super-critical cores with masses 10 times or larger than that of the Earth. It is natural to link the formation probability of gas giant planets with the supply of gases and solids in their natal disks. However, a much richer population of super Earths suggests that (1) there is no shortage of planetary building block material, (2) a gas giant's growth barrier is probably associated with whether it can merge into super-critical cores, and (3) super Earths are probably failed cores that did not attain sufficient mass to initiate efficient accretion of gas before it is severely depleted. Here we construct a model based on the hypothesis that protoplanetary embryos migrated extensively before they were assembled into bona fide planets. We construct a Hermite-Embryo code based on a unified viscous-irradiation disk model and a prescription for the embryo-disk tidal interaction. This code is used to simulate the convergent migration of embryos, and their close encounters and coagulation. Around the progenitors of solar-type stars, the progenitor super-critical-mass cores of gas giant planets primarily form in protostellar disks with relatively high (gsim 10-7 M ⊙ yr-1) mass accretion rates, whereas systems of super Earths (failed cores) are more likely to emerge out of natal disks with modest mass accretion rates, due to the mean motion resonance barrier and retention efficiency.

  2. Thermodynamic and design considerations of organic Rankine cycles in combined application with a solar thermal gas turbine

    NASA Astrophysics Data System (ADS)

    Braun, R.; Kusterer, K.; Sugimoto, T.; Tanimura, K.; Bohn, D.

    2013-12-01

    Concentrated Solar Power (CSP) technologies are considered to provide a significant contribution for the electric power production in the future. Different kinds of technologies are presently in operation or under development, e.g. parabolic troughs, central receivers, solar dish systems and Fresnel reflectors. This paper takes the focus on central receiver technologies, where the solar radiation is concentrated by a field of heliostats in a receiver on the top of a tall tower. To get this CSP technology ready for the future, the system costs have to reduce significantly. The main cost driver in such kind of CSP technologies are the huge amount of heliostats. To reduce the amount of heliostats, and so the investment costs, the efficiency of the energy conversion cycle becomes an important issue. An increase in the cycle efficiency results in a decrease of the solar heliostat field and thus, in a significant cost reduction. The paper presents the results of a thermodynamic model of an Organic Rankine Cycle (ORC) for combined cycle application together with a solar thermal gas turbine. The gas turbine cycle is modeled with an additional intercooler and recuperator and is based on a typical industrial gas turbine in the 2 MW class. The gas turbine has a two stage radial compressor and a three stage axial turbine. The compressed air is preheated within a solar receiver to 950°C before entering the combustor. A hybrid operation of the gas turbine is considered. In order to achieve a further increase of the overall efficiency, the combined operation of the gas turbine and an Organic Rankine Cycle is considered. Therefore an ORC has been set up, which is thermally connected to the gas turbine cycle at two positions. The ORC can be coupled to the solar-thermal gas turbine cycle at the intercooler and after the recuperator. Thus, waste heat from different cycle positions can be transferred to the ORC for additional production of electricity. Within this investigation

  3. Air core notch-coil magnet with variable geometry for fast-field-cycling NMR.

    PubMed

    Kruber, S; Farrher, G D; Anoardo, E

    2015-10-01

    In this manuscript we present details on the optimization, construction and performance of a wide-bore (71 mm) α-helical-cut notch-coil magnet with variable geometry for fast-field-cycling NMR. In addition to the usual requirements for this kind of magnets (high field-to-power ratio, good magnetic field homogeneity, low inductance and resistance values) a tunable homogeneity and a more uniform heat dissipation along the magnet body are considered. The presented magnet consists of only one machined metallic cylinder combined with two external movable pieces. The optimal configuration is calculated through an evaluation of the magnetic flux density within the entire volume of interest. The magnet has a field-to-current constant of 0.728 mT/A, allowing to switch from zero to 0.125 T in less than 3 ms without energy storage assistance. For a cylindrical sample volume of 35 cm(3) the effective magnet homogeneity is lower than 130 ppm. PMID:26367321

  4. The multiproxy analysis of a lacustrine-palustrine sediment core from Lebanon reveals four climate cycles

    NASA Astrophysics Data System (ADS)

    Gasse, F. A.; van Campo, E.; Demory, F.; Develle, A.; Tachikawa, K.; Buchet, N.; Sonzogni, C.; Thouveny, N.; Bard, E. G.; Vidal, L.

    2013-12-01

    The study of a sediment core retrieved from the small Yammouneh basin (34.06°N-34.09°N, 36.0°E-36.03°E, 1360 m a.s.l.), Lebanon, provides for the first time a nearly continuous record spanning approximately 360 ka in northern Levant. The basin, located on the eastern flank of Mount Lebanon, is mainly supplied by karstic springs which discharge snowmelt water infiltrated through the western highlands. Part of its water inputs is lost by seepage through its faulted bottom. The core, 73 m long, consists of four whitish carbonated intervals rich in lacustrine organism remains, interrupting a thick accumulation of colored silty clays almost devoid of shells but for ostracods. We analyzed sediment features (mineralogical and elemental composition, light microscopy and SEM observations, grain size), magnetic properties, pollen and calcite oxygen isotopes (δc) derived from ostracod shell composition. The chronological framework is based on 14C ages of wood fragments, U/Th dating, and a high resolution reconstruction of relative paleointensity variations correlated with regional (Portuguese margin) and global (Sint-800) master curves down to about 360 ka. Although the chronology still needs improvement, the 3 upper carbonated intervals undoubtedly fit Interglacials MIS 1, MIS 5.5 and MIS 7, respectively. The deepest one (49-60 m) is assigned to MIS 9 by its proxy analogies with dated Interglacials. The sequence covers a large part of MIS 10. Relationships between individual indicators are explored, in addition to visual comparisons of individual records, from the multiproxy matrix after resampling at a common depth scale of 25 cm. We compute simple linear coefficients between 20 variables, perform Principal Component Analyses based on all variables, on terrestrial pollen biomes, on all sedimentological proxies, and cross-correlations between them and δc. During Interglacial maxima, high local and regional efficient moisture is evidenced by dense arboreal vegetation of

  5. Life Cycle Greenhouse Gas Emissions of Utility-Scale Wind Power: Systematic Review and Harmonization

    SciTech Connect

    Dolan, S. L.; Heath, G. A.

    2012-04-01

    A systematic review and harmonization of life cycle assessment (LCA) literature of utility-scale wind power systems was performed to determine the causes of and, where possible, reduce variability in estimates of life cycle greenhouse gas (GHG) emissions. Screening of approximately 240 LCAs of onshore and offshore systems yielded 72 references meeting minimum thresholds for quality, transparency, and relevance. Of those, 49 references provided 126 estimates of life cycle GHG emissions. Published estimates ranged from 1.7 to 81 grams CO{sub 2}-equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh), with median and interquartile range (IQR) both at 12 g CO{sub 2}-eq/kWh. After adjusting the published estimates to use consistent gross system boundaries and values for several important system parameters, the total range was reduced by 47% to 3.0 to 45 g CO{sub 2}-eq/kWh and the IQR was reduced by 14% to 10 g CO{sub 2}-eq/kWh, while the median remained relatively constant (11 g CO{sub 2}-eq/kWh). Harmonization of capacity factor resulted in the largest reduction in variability in life cycle GHG emission estimates. This study concludes that the large number of previously published life cycle GHG emission estimates of wind power systems and their tight distribution suggest that new process-based LCAs of similar wind turbine technologies are unlikely to differ greatly. However, additional consequential LCAs would enhance the understanding of true life cycle GHG emissions of wind power (e.g., changes to other generators operations when wind electricity is added to the grid), although even those are unlikely to fundamentally change the comparison of wind to other electricity generation sources.

  6. Conceptual design study on very small long-life gas cooled fast reactor using metallic natural Uranium-Zr as fuel cycle input

    NASA Astrophysics Data System (ADS)

    Monado, Fiber; Ariani, Menik; Su'ud, Zaki; Waris, Abdul; Basar, Khairul; Aziz, Ferhat; Permana, Sidik; Sekimoto, Hiroshi

    2014-02-01

    A conceptual design study of very small 350 MWth Gas-cooled Fast Reactors with Helium coolant has been performed. In this study Modified CANDLE burn-up scheme was implemented to create small and long life fast reactors with natural Uranium as fuel cycle input. Such system can utilize natural Uranium resources efficiently without the necessity of enrichment plant or reprocessing plant. The core with metallic fuel based was subdivided into 10 regions with the same volume. The fresh Natural Uranium is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and the each region-1 is filled by fresh Natural Uranium fuel. This concept is basically applied to all axial regions. The reactor discharge burn-up is 31.8% HM. From the neutronic point of view, this design is in compliance with good performance.

  7. Conceptual design study on very small long-life gas cooled fast reactor using metallic natural Uranium-Zr as fuel cycle input

    SciTech Connect

    Monado, Fiber; Ariani, Menik; Su'ud, Zaki; Waris, Abdul; Basar, Khairul; Permana, Sidik; Aziz, Ferhat; Sekimoto, Hiroshi

    2014-02-12

    A conceptual design study of very small 350 MWth Gas-cooled Fast Reactors with Helium coolant has been performed. In this study Modified CANDLE burn-up scheme was implemented to create small and long life fast reactors with natural Uranium as fuel cycle input. Such system can utilize natural Uranium resources efficiently without the necessity of enrichment plant or reprocessing plant. The core with metallic fuel based was subdivided into 10 regions with the same volume. The fresh Natural Uranium is initially put in region-1, after one cycle of 10 years of burn-up it is shifted to region-2 and the each region-1 is filled by fresh Natural Uranium fuel. This concept is basically applied to all axial regions. The reactor discharge burn-up is 31.8% HM. From the neutronic point of view, this design is in compliance with good performance.

  8. Tubular SOFC and SOFC/Gas Turbine combined cycles-status and prospects

    SciTech Connect

    Veyo, S.E.; Lundberg, W.L.

    1996-12-31

    Presently under fabrication at Westinghouse for EDB/ELSAM, a consortium of Dutch and Danish utilities, is the world`s first 100 kWe Solid Oxide Fuel Cell (SOFC) power generation system. This natural gas fueled experimental field unit will be installed near Arnhem, The Netherlands, at an auxiliary district heating plant (Hulp Warmte Centrale) at the Rivierweg in Westervoort, a site provided by NUON, one of the Dutch participants, and will supply ac power to the utility grid and hot water to the district heating system serving the Duiven/Westervoort area. The electrical generation efficiency of this simple cycle atmospheric pressure system will approach 50%. The analysis of conceptual designs for larger capacity systems indicates that the horizon for the efficiency of simple cycle atmospheric pressure units is about 55%.

  9. Effect of drink temperature on core temperature and endurance cycling performance in warm, humid conditions.

    PubMed

    Burdon, Catriona; O'Connor, Helen; Gifford, Janelle; Shirreffs, Susan; Chapman, Phillip; Johnson, Nathan

    2010-09-01

    The aims of this study were to determine the effect of cold (4 °C) and thermoneutral (37 °C) beverages on thermoregulation and performance in the heat and to explore sensory factors associated with ingesting a cold stimulus. Seven males (age 32.8 ± 6.1 years, [V(.)]O(2peak) 59.4 ± 6.6 ml x kg(-1) x min(-1)) completed cold, thermoneutral, and thermoneutral + ice trials in randomized order. Participants cycled for 90 min at 65%[V(.)]O(2peak) followed by a 15-min performance test at 28 °C and 70% relative humidity. They ingested 2.3 ml x kg(-1) of a 7.4% carbohydrate-electrolyte solution every 10 min during the 90-min steady-state exercise including 30 ml ice puree every 5 min in the ice trial. Absolute changes in skin temperature (0.22 ± 1.1 °C vs. 1.14 ± 0.9 °C; P = 0.02), mean body temperature (1.2 ± 0.3 vs. 1.6 ± 0.3 °C; P = 0.03), and heat storage were lower across the 90-min exercise bout for the cold compared with the thermoneutral trial. Significant improvements (4.9 ± 2.4%, P < 0.01) in performance were observed with cold but no significant differences were detected with ice. Consumption of cold beverages during prolonged exercise in the heat improves body temperature measures and performance. Consumption of ice did not reveal a sensory response, but requires further study. Beverages consumed by athletes exercising in the heat should perhaps be cold for performance and safety reasons. PMID:20694887

  10. Fuel-cycle greenhouse gas emissions impacts of alternative transportation fuels and advanced vehicle technologies.

    SciTech Connect

    Wang, M. Q.

    1998-12-16

    At an international conference on global warming, held in Kyoto, Japan, in December 1997, the United States committed to reduce its greenhouse gas (GHG) emissions by 7% over its 1990 level by the year 2012. To help achieve that goal, transportation GHG emissions need to be reduced. Using Argonne's fuel-cycle model, I estimated GHG emissions reduction potentials of various near- and long-term transportation technologies. The estimated per-mile GHG emissions results show that alternative transportation fuels and advanced vehicle technologies can help significantly reduce transportation GHG emissions. Of the near-term technologies evaluated in this study, electric vehicles; hybrid electric vehicles; compression-ignition, direct-injection vehicles; and E85 flexible fuel vehicles can reduce fuel-cycle GHG emissions by more than 25%, on the fuel-cycle basis. Electric vehicles powered by electricity generated primarily from nuclear and renewable sources can reduce GHG emissions by 80%. Other alternative fuels, such as compressed natural gas and liquefied petroleum gas, offer limited, but positive, GHG emission reduction benefits. Among the long-term technologies evaluated in this study, conventional spark ignition and compression ignition engines powered by alternative fuels and gasoline- and diesel-powered advanced vehicles can reduce GHG emissions by 10% to 30%. Ethanol dedicated vehicles, electric vehicles, hybrid electric vehicles, and fuel-cell vehicles can reduce GHG emissions by over 40%. Spark ignition engines and fuel-cell vehicles powered by cellulosic ethanol and solar hydrogen (for fuel-cell vehicles only) can reduce GHG emissions by over 80%. In conclusion, both near- and long-term alternative fuels and advanced transportation technologies can play a role in reducing the United States GHG emissions.

  11. The influence of woody encroachment on the nitrogen cycle: fixation, storage and gas loss

    NASA Astrophysics Data System (ADS)

    Soper, F.; Sparks, J. P.

    2015-12-01

    Woody encroachment is a pervasive land cover change throughout the tropics and subtropics. Encroachment is frequently catalyzed by nitrogen (N)-fixing trees and the resulting N inputs potentially alter whole-ecosystem N cycling, accumulation and loss. In the southern US, widespread encroachment by legume Prosopis glandulosa is associated with increased soil total N storage, inorganic N concentrations, and net mineralization and nitrification rates. To better understand the effects of this process on ecosystem N cycling, we investigated patterns of symbiotic N fixation, N accrual and soil N trace gas and N2 emissions during Prosopis encroachment into the southern Rio Grande Plains. Analyses of d15N in foliage, xylem sap and plant-available soil N suggested that N fixation rates increase with tree age and are influenced by abiotic conditions. A model of soil N accrual around individual trees, accounting for atmospheric inputs and gas losses, generates lifetimes N fixation estimates of up to 9 kg for a 100-year-old tree and current rates of 7 kg N ha-1 yr-1. However, these N inputs and increased soil cycling rates do not translate into increased N gas losses. Two years of field measurements of a complete suite of N trace gases (ammonia, nitrous oxide, nitric oxide and other oxidized N compounds) found no difference in flux between upland Prosopis groves and adjacent unencroached grasslands. Total emissions for both land cover types average 0.56-0.65 kg N ha-1 yr-1, comparable to other southern US grasslands. Additional lab experiments suggested that N2 losses are low and that field oxygen conditions are not usually conducive to denitrification. Taken together, results suggest that this ecosystem is currently experiencing a period of net N accrual under ongoing encroachment.

  12. Optimization of wave rotors for use as gas turbine engine topping cycles

    NASA Technical Reports Server (NTRS)

    Wilson, Jack; Paxson, Daniel E.

    1995-01-01

    Use of a wave rotor as a topping cycle for a gas turbine engine can improve specific power and reduce specific fuel consumption. Maximum improvement requires the wave rotor to be optimized for best performance at the mass flow of the engine. The optimization is a trade-off between losses due to friction and passage opening time, and rotational effects. An experimentally validated, one-dimensional CFD code, which includes these effects, has been used to calculate wave rotor performance, and find the optimum configuration. The technique is described, and results given for wave rotors sized for engines with sea level mass flows of 4, 26, and 400 lb/sec.

  13. The origin of gas-phase HCO and CH3O radicals in prestellar cores

    NASA Astrophysics Data System (ADS)

    Bacmann, A.; Faure, A.

    2016-03-01

    Context. The recent unexpected detection of terrestrial complex organic molecules in the cold (~10 K) gas has cast doubts on the commonly accepted formation mechanisms of these species. Standard gas-phase mechanisms are inefficient and tend to underproduce these molecules, and many of the key reactions involved are unconstrained. Grain-surface mechanisms, which were presented as a viable alternative, suffer from the fact that they rely on grain surface diffusion of heavy radicals, which is not possible thermally at very low temperatures. Aims: One of the simplest terrestrial complex organic molecules, methanol is believed to form on cold grain surfaces following from successive H atom additions on CO. Unlike heavier species, H atoms are very mobile on grain surfaces even at 10 K. Intermediate species involved in grain surface methanol formation by CO hydrogenation are the radicals HCO and CH3O, as well as the stable species formaldehyde H2CO. These radicals are thought to be precursors of complex organic molecules on grain surfaces. Methods: We present new observations of the HCO and CH3O radicals in a sample of prestellar cores and carry out an analysis of the abundances of the species HCO, H2CO, CH3O, and CH3OH, which represent the various stages of grain-surface hydrogenation of CO to CH3OH. Results: The abundance ratios between the various intermediate species in the hydrogenation reaction of CO on grains are similar in all sources of our sample, HCO:H2CO:CH3O:CH3OH ~10:100:1:100. We argue that these ratios may not be representative of the primordial abundances on the grains but, rather, suggest that the radicals HCO and CH3O are gas-phase products of the precursors H2CO and CH3OH, respectively. Various gas-phase pathways are considered, including neutral-neutral and ion-molecule reactions, and simple estimates of HCO and CH3O abundances are compared to the observations. Critical reaction rate constants, branching ratios, and intermediate species are finally

  14. Grain-scale imaging and compositional characterization of cryo-preserved India NGHP 01 gas-hydrate-bearing cores

    USGS Publications Warehouse

    Stern, Laura A.; Lorenson, T.D.

    2014-01-01

    We report on grain-scale characteristics and gas analyses of gas-hydrate-bearing samples retrieved by NGHP Expedition 01 as part of a large-scale effort to study gas hydrate occurrences off the eastern-Indian Peninsula and along the Andaman convergent margin. Using cryogenic scanning electron microscopy, X-ray spectroscopy, and gas chromatography, we investigated gas hydrate grain morphology and distribution within sediments, gas hydrate composition, and methane isotopic composition of samples from Krishna–Godavari (KG) basin and Andaman back-arc basin borehole sites from depths ranging 26 to 525 mbsf. Gas hydrate in KG-basin samples commonly occurs as nodules or coarse veins with typical hydrate grain size of 30–80 μm, as small pods or thin veins 50 to several hundred microns in width, or disseminated in sediment. Nodules contain abundant and commonly isolated macropores, in some places suggesting the original presence of a free gas phase. Gas hydrate also occurs as faceted crystals lining the interiors of cavities. While these vug-like structures constitute a relatively minor mode of gas hydrate occurrence, they were observed in near-seafloor KG-basin samples as well as in those of deeper origin (>100 mbsf) and may be original formation features. Other samples exhibit gas hydrate grains rimmed by NaCl-bearing material, presumably produced by salt exclusion during original hydrate formation. Well-preserved microfossil and other biogenic detritus are also found within several samples, most abundantly in Andaman core material where gas hydrate fills microfossil crevices. The range of gas hydrate modes of occurrence observed in the full suite of samples suggests a range of formation processes were involved, as influenced by local in situconditions. The hydrate-forming gas is predominantly methane with trace quantities of higher molecular weight hydrocarbons of primarily microbial origin. The composition indicates the gas hydrate is Structure I.

  15. Microalgae Production from Power Plant Flue Gas: Environmental Implications on a Life Cycle Basis

    SciTech Connect

    Kadam, K. L.

    2001-06-22

    Power-plant flue gas can serve as a source of CO{sub 2} for microalgae cultivation, and the algae can be cofired with coal. This life cycle assessment (LCA) compared the environmental impacts of electricity production via coal firing versus coal/algae cofiring. The LCA results demonstrated lower net values for the algae cofiring scenario for the following using the direct injection process (in which the flue gas is directly transported to the algae ponds): SOx, NOx, particulates, carbon dioxide, methane, and fossil energy consumption. Carbon monoxide, hydrocarbons emissions were statistically unchanged. Lower values for the algae cofiring scenario, when compared to the burning scenario, were observed for greenhouse potential and air acidification potential. However, impact assessment for depletion of natural resources and eutrophication potential showed much higher values. This LCA gives us an overall picture of impacts across different environmental boundaries, and hence, can help in the decision-making process for implementation of the algae scenario.

  16. Dual Brayton cycle gas turbine pressurized fluidized bed combustion power plant concept

    SciTech Connect

    Yan, X.L.; Lidsky, L.M.

    1998-07-01

    High generating efficiency has compelling economic and environmental benefits for electric power plants. There are particular incentives to develop more efficient and cleaner coal-fired power plants in order to permit use of the world`s most abundant and secure energy source. This paper presents a newly conceived power plant design, the Dual Brayton Cycle Gas Turbine PFBC, that yields 45% net generating efficiency and fires on a wide range of fuels with minimum pollution, of which coal is a particularly intriguing target for its first application. The DBC-GT design allows power plants based on the state-of-the-art PFBC technology to achieve substantially higher generating efficiencies, while simultaneously providing modern gas turbine and related heat exchanger technologies access to the large coal power generation market.

  17. Thermodynamic and economic analysis of a gas turbine combined cycle plant with oxy-combustion

    NASA Astrophysics Data System (ADS)

    Kotowicz, Janusz; Job, Marcin

    2013-12-01

    This paper presents a gas turbine combined cycle plant with oxy-combustion and carbon dioxide capture. A gas turbine part of the unit with the operating parameters is presented. The methodology and results of optimization by the means of a genetic algorithm for the steam parts in three variants of the plant are shown. The variants of the plant differ by the heat recovery steam generator (HRSG) construction: the singlepressure HRSG (1P), the double-pressure HRSG with reheating (2PR), and the triple-pressure HRSG with reheating (3PR). For obtained results in all variants an economic evaluation was performed. The break-even prices of electricity were determined and the sensitivity analysis to the most significant economic factors were performed.

  18. Observation of the core of the Perseus cluster with the Einstein solid state spectrometer: Cooling gas and elemental abundances

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.; Holt, S. S.; Smith, B. W.; Boldt, E. A.; Serlemitsos, P. J.

    1980-01-01

    Solid State Spectrometer observations of the core of the Perseus cluster have resulted in the detection of X-ray emission lines due to Si, S, and Fe. Analysis of the spectrum indicates that the X-ray emission has at least two characteristic temperatures. This is interpreted in the framework of radiative accretion in the core of the cluster. The derived parameters are a cooling time tc less than 2 x 109 yrs for the low temperature gas, a mass accretion rate of approximately 300 Mo/yr and a characteristic size of 10 to 20 Kpc for the cool gas. The Fe abundance in the core, approximately 0.4, is similar to the Fe abundance averaged over the whole cluster indicating that Fe emission is not strongly concentrated about NGC 1275. The Si and S abundances are consistent with solar values.

  19. Theory of photoionization-induced blueshift of ultrashort solitons in gas-filled hollow-core photonic crystal fibers.

    PubMed

    Saleh, Mohammed F; Chang, Wonkeun; Hölzer, Philipp; Nazarkin, Alexander; Travers, John C; Joly, Nicolas Y; Russell, Philip St J; Biancalana, Fabio

    2011-11-11

    We show theoretically that the photoionization process in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas leads to a constant acceleration of solitons in the time domain with a continuous shift to higher frequencies, limited only by ionization loss. This phenomenon is opposite to the well-known Raman self-frequency redshift of solitons in solid-core glass fibers. We also predict the existence of unconventional long-range nonlocal soliton interactions leading to spectral and temporal soliton clustering. Furthermore, if the core is filled with a Raman-active molecular gas, spectral transformations between redshifted, blueshifted, and stabilized solitons can take place in the same fiber. PMID:22181733

  20. MHTGR [modular high-temperature gas-cooled reactor] core physics validation plan

    SciTech Connect

    Baxter, A.; Hackney, R.

    1988-01-01

    This document contains the verification and validation (V&V) plan for analytical methods utilized in the nuclear design for normal and off-normal conditions within the Modular High-Temperature Gas-Cooled Reactor (MHTGR). Regulations, regulatory guides, and industry standards have been reviewed and the approach for V&V has been developed. MHTGR core physics methods are described and the status of previous V&V is summarized within this document. Additional work required to verify and validate these methods is identified. The additional validation work includes comparison of calculations with available experimental data, benchmark comparison of calculations with available experimental data, benchmark comparisons with other validated codes, results from a cooperative program now underway at the Arbeitsgemeinschaft Versuchs-Reaktor GmbH (AVR) facility in Germany, results from a planned series of experiments on the Compact Nuclear Power Source (CNPS) facility at Los Alamos, and detailed documentation of all V&V studies. In addition, information will be obtained from planned international cooperative agreements to provide supplemental data for V&V. The regulatory technology development plan will be revised to include these additional experiments. A work schedule and cost estimate for completing this plan is also provided. This work schedule indicates the timeframe in which major milestones must be performed in order to complete V&V tasks prior to the issuance of preliminary design approval from the NRC. The cost to complete V&V tasks for core physics computational methods is estimated to be $2.2M. 41 refs., 13 figs., 8 tabs.

  1. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 4: Open recuperated and bottomed gas turbine cycles. [performance prediction and energy conversion efficiency of gas turbines in electric power plants (thermodynamic cycles)

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Grube, J. E.

    1976-01-01

    Open-cycle recuperated gas turbine plant with inlet temperatures of 1255 to 1644 K (1800 to 2500 F) and recuperators with effectiveness values of 0, 70, 80 and 90% are considered. A 1644 K (2500 F) gas turbine would have a 33.5% plant efficiency in a simple cycle, 37.6% in a recuperated cycle and 47.6% when combined with a sulfur dioxide bottomer. The distillate burning recuperated plant was calculated to produce electricity at a cost of 8.19 mills/MJ (29.5 mills/kWh). Due to their low capital cost $170 to 200 $/kW, the open cycle gas turbine plant should see duty for peaking and intermediate load duty.

  2. Recovery Act: Brea California Combined Cycle Electric Generating Plant Fueled by Waste Landfill Gas

    SciTech Connect

    Galowitz, Stephen

    2012-12-31

    The primary objective of the Project was to maximize the productive use of the substantial quantities of waste landfill gas generated and collected at the Olinda Landfill near Brea, California. An extensive analysis was conducted and it was determined that utilization of the waste gas for power generation in a combustion turbine combined cycle facility was the highest and best use. The resulting Project reflected a cost effective balance of the following specific sub-objectives: • Meeting the environmental and regulatory requirements, particularly the compliance obligations imposed on the landfill to collect, process and destroy landfill gas • Utilizing proven and reliable technology and equipment • Maximizing electrical efficiency • Maximizing electric generating capacity, consistent with the anticipated quantities of landfill gas generated and collected at the Olinda Landfill • Maximizing equipment uptime • Minimizing water consumption • Minimizing post-combustion emissions • The Project produced and will produce a myriad of beneficial impacts. o The Project created 360 FTE construction and manufacturing jobs and 15 FTE permanent jobs associated with the operation and maintenance of the plant and equipment. o By combining state-of-the-art gas clean up systems with post combustion emissions control systems, the Project established new national standards for best available control technology (BACT). o The Project will annually produce 280,320 MWh’s of clean energy o By destroying the methane in the landfill gas, the Project will generate CO2 equivalent reductions of 164,938 tons annually. The completed facility produces 27.4 MWnet and operates 24 hours a day, seven days a week.

  3. Energy and greenhouse gas profiles of polyhydroxybutyrates derived from corn grain: a life cycle perspective.

    PubMed

    Kim, Seungdo; Dale, Bruce E

    2008-10-15

    Polyhydroxybutyrates (PHB) are well-known biopolymers derived from sugars orvegetable oils. Cradle-to-gate environmental performance of PHB derived from corn grain is evaluated through life cycle assessment (LCA), particularly nonrenewable energy consumption and greenhouse gas emissions. Site-specific process information on the corn wet milling and PHB fermentation and recovery processes was obtained from Telles. Most of energy used in the corn wet milling and PHB fermentation and recovery processes is generated in a cogeneration power plant in which corn stover, assumed to be representative of a variety of biomass sources that could be used, is burned to generate electricity and steam. County level agricultural information is used in estimating the environmental burdens associated with both corn grain and corn stover production. Results show that PHB derived from corn grain offers environmental advantages over petroleum-derived polymers in terms of nonrenewable energy consumption and greenhouse gas emissions. Furthermore, PHB provides greenhouse gas credits, and thus PHB use reduces greenhouse gas emissions compared to petroleum-derived polymers. Corn cultivation is one of the environmentally sensitive areas in the PHB production system. More sustainable practices in corn cultivation (e.g., using no-tillage and winter cover crops) could reduce the environmental impacts of PHB by up to 72%. PMID:18983094

  4. Oxygen-induced plasticity in tracheal morphology and discontinuous gas exchange cycles in cockroaches Nauphoeta cinerea.

    PubMed

    Bartrim, Hamish; Matthews, Philip G D; Lemon, Sussan; White, Craig R

    2014-12-01

    The function and mechanism underlying discontinuous gas exchange in terrestrial arthropods continues to be debated. Three adaptive hypotheses have been proposed to explain the evolutionary origin or maintenance of discontinuous gas exchange cycles (DGCs), which may have evolved to reduce respiratory water loss, facilitate gas exchange in high CO2 and low O2 micro-environments, or to ameliorate potential damage as a result of oversupply of O2. None of these hypotheses have unequivocal support, and several non-adaptive hypotheses have also been proposed. In the present study, we reared cockroaches Nauphoeta cinerea in selected levels of O2 throughout development, and examined how this affected growth rate, tracheal morphology and patterns of gas exchange. O2 level in the rearing environment caused significant changes in tracheal morphology and the exhibition of DGCs, but the direction of these effects was inconsistent with all three adaptive hypotheses: water loss was not associated with DGC length, cockroaches grew fastest in hyperoxia, and DGCs exhibited by cockroaches reared in normoxia were shorter than those exhibited by cockroaches reared in hypoxia or hyperoxia. PMID:25378216

  5. LIFE-CYCLE EVALUATION OF GREENHOUSE GAS EMISSIONS FROM MUNICIPAL SOLID WASTE MANAGEMENT IN THE UNITED STATES

    EPA Science Inventory

    The paper discusses a life-cycle evaluation of greenhouse gas (GHG) emissions from municipal soild waste (MSW) management in the U.S. (NOTE: Using integrated waste management, recycling/composting, waste-to-energy, and better control of landfill gas, communities across the U.S. a...

  6. Detection of a turbulent gas component associated with a starless core with subthermal turbulence in the Orion A cloud

    NASA Astrophysics Data System (ADS)

    Ohashi, Satoshi; Tatematsu, Ken'ichi; Sanhueza, Patricio; Hirota, Tomoya; Choi, Minho; Mizuno, Norikazu

    2016-07-01

    We report the detection of a wing component in NH3 emission towards the starless core TUKH122 with subthermal turbulence in the Orion A cloud. This NH3 core is suggested to be on the verge of star formation because the turbulence inside the NH3 core is almost completely dissipated, and also because it is surrounded by CCS, which resembles the prestellar core L1544 in Taurus showing infall motions. Observations were carried out with the Nobeyama 45-m telescope at 0.05 km s-1 velocity resolution. We find that the NH3 line profile consists of two components. The quiescent main component has a small linewidth of 0.3 km s-1 dominated by thermal motion, and the red-shifted wing component has a large linewidth of 1.36 km s-1 representing turbulent motion. These components show kinetic temperatures of 11 and <30 K, respectively. Furthermore, there is a clear velocity offset between the NH3 quiescent gas (Local Standard of Rest velocity = 3.7 km s-1) and the turbulent gas (4.4 km s-1). The centroid velocity of the turbulent gas corresponds to that of the surrounding gas traced by the 13CO (J = 1-0) and CS (J = 2-1) lines. Large Velocity Gradient (LVG) model calculations for CS and CO show that the turbulent gas has a temperature of 8-13 K and an H2 density of ˜104 cm-3, suggesting that the temperature of the turbulent component is also ˜10 K. The detections of both NH3 quiescent and wing components may indicate a sharp transition from the turbulent parent cloud to the quiescent dense core.

  7. Detection of a turbulent gas component associated with a starless core with subthermal turbulence in the Orion A cloud

    NASA Astrophysics Data System (ADS)

    Ohashi, Satoshi; Tatematsu, Ken'ichi; Sanhueza, Patricio; Nguyen Luong, Quang; Hirota, Tomoya; Choi, Minho; Mizuno, Norikazu

    2016-04-01

    We report the detection of a wing component in NH3 emission toward the starless core TUKH122 with subthermal turbulence in the Orion A cloud. This NH3 core is suggested to be on the verge of star formation because the turbulence inside the NH3 core is almost completely dissipated, and also because it is surrounded by CCS, which resembles the prestellar core L1544 in Taurus showing infall motions. Observations were carried out with the Nobeyama 45 m telescope at 0.05 km s-1 velocity resolution. We find that the NH3 line profile consists of two components. The quiescent main component has a small linewidth of 0.3 km s-1 dominated by thermal motions, and the red-shifted wing component has a large linewidth of 1.36 km s-1 representing turbulent motions. These components show kinetic temperatures of 11 K and < 30 K, respectively. Furthermore, there is a clear velocity offset between the NH3 quiescent gas (VLSR = 3.7 km s-1) and the turbulent gas (VLSR = 4.4 km s-1). The centroid velocity of the turbulent gas corresponds to that of the surrounding gas traced by the 13CO (J = 1 - 0) and CS (J = 2 - 1) lines. LVG model calculations for CS and CO show that the turbulent gas has a temperature of 8 - 13 K and an H2 density of ∼ 104 cm-3, suggesting that the temperature of the turbulent component is also ∼ 10 K. The detections of both NH3 quiescent and wing components may indicate a sharp transition from the turbulent parent cloud to the quiescent dense core.

  8. Life Cycle Greenhouse Gas Emissions from Uranium Mining and Milling in Canada.

    PubMed

    Parker, David J; McNaughton, Cameron S; Sparks, Gordon A

    2016-09-01

    Life cycle greenhouse gas (GHG) emissions from the production of nuclear power (in g CO2e/kWh) are uncertain due partly to a paucity of data on emissions from individual phases of the nuclear fuel cycle. Here, we present the first comprehensive life cycle assessment of GHG emissions produced from the mining and milling of uranium in Canada. The study includes data from 2006-2013 for two uranium mine-mill operations in northern Saskatchewan (SK) and data from 1995-2010 for a third SK mine-mill operation. The mine-mill operations were determined to have GHG emissions intensities of 81, 64, and 34 kg CO2e/kg U3O8 at average ore grades of 0.74%, 1.54%, and 4.53% U3O8, respectively. The production-weighted average GHG emission intensity is 42 kg CO2e/kg U3O8 at an average ore grade of 3.81% U3O8. The production-weighted average GHG emission intensity drops to 24 kg CO2e/kg U3O8 when the local hydroelectric GHG emission factor (7.2 g CO2e/kWh) is substituted for the SK grid-average electricity GHG emission factor (768 g CO2e/kWh). This results in Canadian uranium mining-milling contributing only 1.1 g CO2e/kWh to total life cycle GHG emissions from the nuclear fuel cycle (0.7 g CO2e/kWh using the local hydroelectric emission factor). PMID:27471915

  9. An analytical study of volatile metallic fission product release from very high temperature gas-cooled reactor fuel and core

    SciTech Connect

    Mitake, S.; Okamoto, F.

    1988-04-01

    Release characteristics of volatile metallic fission products from the coated fuel particle and the reactor core for a very high temperature gas-cooled reactor during its power operation has been studied using numerical analysis. A computer code FORNAX, based on Fick's diffusion law and the evaporation mass transfer relation, has been developed, which considers, in particular, distribution and time histories of power density, fuel temperature, and failed and degraded fuel particle fractions in the core. Applicability of the code to evaluate the core design has been shown and the following have been indicated on the release of cesium from the reactor: 1. The release from the intact fuel particles by diffusion through their intact coatings shows larger contribution in the total core release at higher temperature. 2. The diffusion release from the intact particle is governed not only by the diffusion in the silicon carbide layer but also by that in the fuel kernel.

  10. Buoyancy-driven inflow to a relic cold core: the gas belt in radio galaxy 3C 386

    NASA Astrophysics Data System (ADS)

    Duffy, R. T.; Worrall, D. M.; Birkinshaw, M.; Kraft, R. P.

    2016-07-01

    We report measurements from an XMM-Newton observation of the low-excitation radio galaxy 3C 386. The study focusses on an X-ray-emitting gas belt, which lies between and orthogonal to the radio lobes of 3C 386 and has a mean temperature of 0.94 ± 0.05 keV, cooler than the extended group atmosphere. The gas in the belt shows temperature structure with material closer to the surrounding medium being hotter than gas closer to the host galaxy. We suggest that this gas belt involves a `buoyancy-driven inflow' of part of the group-gas atmosphere where the buoyant rise of the radio lobes through the ambient medium has directed an inflow towards the relic cold core of the group. Inverse-Compton emission from the radio lobes is detected at a level consistent with a slight suppression of the magnetic field below the equipartition value.

  11. Buoyancy-driven inflow to a relic cold core: the gas belt in radio galaxy 3C 386

    NASA Astrophysics Data System (ADS)

    Duffy, R. T.; Worrall, D. M.; Birkinshaw, M.; Kraft, R. P.

    2016-04-01

    We report measurements from an XMM-Newton observation of the low-excitation radio galaxy 3C 386. The study focusses on an X-ray-emitting gas belt, which lies between and orthogonal to the radio lobes of 3C 386 and has a mean temperature of 0.94 ± 0.05 keV, cooler than the extended group atmosphere. The gas in the belt shows temperature structure with material closer to the surrounding medium being hotter than gas closer to the host galaxy. We suggest that this gas belt involves a `buoyancy-driven inflow' of part of the group-gas atmosphere where the buoyant rise of the radio lobes through the ambient medium has directed an inflow towards the relic cold core of the group. Inverse-Compton emission from the radio lobes is detected at a level consistent with a slight suppression of the magnetic field below the equipartition value.

  12. Networked solid oxide fuel cell stacks combined with a gas turbine cycle

    NASA Astrophysics Data System (ADS)

    Selimovic, Azra; Palsson, Jens

    An improved design of fuel cells stacks arrangement has been suggested before for MCFC where reactant streams are ducted such that they are fed and recycled among multiple MCFC stacks in series. By networking fuel cell stacks, increased efficiency, improved thermal balance, and higher total reactant utilisation can be achieved. In this study, a combination of networked solid oxide fuel cell (SOFC) stacks and a gas turbine (GT) has been modelled and analysed. In such a combination, the stacks are operating in series with respect to the fuel flow. In previous studies, conducted on hybrid SOFC/GT cycles by the authors, it was shown that the major part of the output of such cycles can be addressed to the fuel cell. In those studies, a single SOFC with parallel gas flows to individual cells were assumed. It can be expected that if the performance of the fuel cell is enhanced by networking, the overall system performance will improve. In the first part of this paper, the benefit of the networked stacks is demonstrated for a stand alone stack while the second part analyses and discusses the impact networking of the stacks has on the SOFC/GT system performance and design. For stacks with both reactant streams in series, a significant increase of system efficiency was found (almost 5% points), which, however, can be explained mainly by an improved thermal management.

  13. Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycle Technology for Auxiliary Aerospace Power

    NASA Technical Reports Server (NTRS)

    Steffen, Christopher J., Jr.; Freeh, Joshua E.; Larosiliere, Louis M.

    2005-01-01

    A notional 440 kW auxiliary power unit has been developed for 300 passenger commercial transport aircraft in 2015AD. A hybrid engine using solid-oxide fuel cell stacks and a gas turbine bottoming cycle has been considered. Steady-state performance analysis during cruise operation has been presented. Trades between performance efficiency and system mass were conducted with system specific energy as the discriminator. Fuel cell performance was examined with an area specific resistance. The ratio of fuel cell versus turbine power was explored through variable fuel utilization. Area specific resistance, fuel utilization, and mission length had interacting effects upon system specific energy. During cruise operation, the simple cycle fuel cell/gas turbine hybrid was not able to outperform current turbine-driven generators for system specific energy, despite a significant improvement in system efficiency. This was due in part to the increased mass of the hybrid engine, and the increased water flow required for on-board fuel reformation. Two planar, anode-supported cell design concepts were considered. Designs that seek to minimize the metallic interconnect layer mass were seen to have a large effect upon the system mass estimates.

  14. Life cycle assessment of gas atomised sponge nickel for use in alkaline hydrogen fuel cell applications

    NASA Astrophysics Data System (ADS)

    Wilson, Benjamin P.; Lavery, Nicholas P.; Jarvis, David J.; Anttila, Tomi; Rantanen, Jyri; Brown, Stephen G. R.; Adkins, Nicholas J.

    2013-12-01

    This paper presents a cradle-to-grave comparative Life Cycle Assessment (LCA) of new gas atomised (GA) sponge nickel catalysts and evaluates their performance against the both cast and crush (CC) sponge nickel and platinum standards currently used in commercial alkaline fuel cells (AFC). The LCA takes into account the energy used and emissions throughout the entire life cycle of sponge nickel catalysts - ranging from the upstream production of materials (mainly aluminium and nickel), to the manufacturing, to the operation and finally to the recycling and disposal. Through this assessment it was found that the energy and emissions during the operational phase associated with a given catalyst considerably outweigh the primary production, manufacturing and recycling. Primary production of the nickel (and to a lesser extent dopant materials) also has a significant environmental impact but this is offset by operational energy savings over the electrode's estimated lifetime and end of life recyclability. From the results it can be concluded that higher activity spongy nickel catalysts produced by gas atomisation could have a significantly lower environmental impact than either CC nickel or platinum. Doped GA sponge nickel in particular showed comparable performance to that of the standard platinum electrode used in AFCs.

  15. Oxygen convective uptakes in gas exchange cycles in early diapause pupae of Pieris brassicae.

    PubMed

    Jõgar, Katrin; Kuusik, Aare; Ploomi, Angela; Metspalu, Luule; Williams, Ingrid; Hiiesaar, Külli; Kivimägi, Irja; Mänd, Marika; Tasa, Tea; Luik, Anne

    2011-09-01

    Oxygen convective uptakes in gas exchange cycles were directly recorded in early diapause pupae of Pieris brassicae L. (Lepidoptera; Pieridae) by means of O2 coulometric respirometry. This method was combined with flow-through CO2 respirometry, the two systems being switchable one to the other. During recording with both systems, measurements were also taken with infrared actography. The pupae displayed short discontinuous gas exchange cycles lasting 40-70 min. No true C phase was found by flow-through measurements; instead, flutter opening of the spiracles with discrete convective O2 uptakes began shortly after the O phase whereas CO2 release was suppressed by the inward directed passive suction ventilation. The F phase was characterized by a series of small CO2 bursts (flutter events). Between these bursts, novel sub-phase `miniflutter' was observed, which consisted of six to 10 miniature inspirations without any CO2 emission. During the flow-through measurements, oxygen convective uptakes were indirectly recorded by the infrared actograph as sudden extensions (lengthening) of the abdominal segments at each spiracular microopening. PMID:21832124

  16. Multiple phase transitions in extended hard-core lattice gas models in two dimensions.

    PubMed

    Nath, Trisha; Rajesh, R

    2014-07-01

    We study the k-NN hard-core lattice gas model in which the first k next-nearest-neighbor sites of a particle are excluded from occupation by other particles on a two-dimensional square lattice. This model is the lattice version of the hard-disk system with increasing k corresponding to decreasing lattice spacing. While the hard-disk system is known to undergo a two-step freezing process with increasing density, the lattice model has been known to show only one transition. Here, based on Monte Carlo simulations and high-density expansions of the free energy and density, we argue that for k = 4,10,11,14,⋯, the lattice model undergoes multiple transitions with increasing density. Using Monte Carlo simulations, we confirm the same for k = 4,...,11. This, in turn, resolves an existing puzzle as to why the 4-NN model has a continuous transition against the expectation of a first-order transition. PMID:25122264

  17. Raman-free nonlinear optical effects in high pressure gas-filled hollow core PCF.

    PubMed

    Azhar, M; Wong, G K L; Chang, W; Joly, N Y; Russell, P St J

    2013-02-25

    The effective Kerr nonlinearity of hollow-core kagomé-style photonic crystal fiber (PCF) filled with argon gas increases to ~15% of that of bulk silica glass when the pressure is increased from 1 to 150 bar, while the zero dispersion wavelength shifts from 300 to 900 nm. The group velocity dispersion of the system is uniquely pressure-tunable over a wide range while avoiding Raman scattering-absent in noble gases-and having an extremely high optical damage threshold. As a result, detailed and well-controlled studies of nonlinear effects can be performed, in both normal and anomalous dispersion regimes, using only a fixed-frequency pump laser. For example, the absence of Raman scattering permits clean observation, at high powers, of the interaction between a modulational instability side-band and a soliton-created dispersive wave. Excellent agreement is obtained between numerical simulations and experimental results. The system has great potential for the realization of reconfigurable supercontinuum sources, wavelength convertors and short-pulse laser systems. PMID:23481974

  18. Georgia Institute of Technology research on the Gas Core Actinide Transmutation Reactor (GCATR)

    NASA Technical Reports Server (NTRS)

    Clement, J. D.; Rust, J. H.; Schneider, A.; Hohl, F.

    1976-01-01

    The program reviewed is a study of the feasibility, design, and optimization of the GCATR. The program is designed to take advantage of initial results and to continue work carried out on the Gas Core Breeder Reactor. The program complements NASA's program of developing UF6 fueled cavity reactors for power, nuclear pumped lasers, and other advanced technology applications. The program comprises: (1) General Studies--Parametric survey calculations performed to examine the effects of reactor spectrum and flux level on the actinide transmutation for GCATR conditions. The sensitivity of the results to neutron cross sections are to be assessed. Specifically, the parametric calculations of the actinide transmutation are to include the mass, isotope composition, fission and capture rates, reactivity effects, and neutron activity of recycled actinides. (2) GCATR Design Studies--This task is a major thrust of the proposed research program. Several subtasks are considered: optimization criteria studies of the blanket and fuel reprocessing, the actinide insertion and recirculation system, and the system integration. A brief review of the background of the GCATR and ongoing research is presented.

  19. Carbon cycle constraints during the last glacial/interglacial cycle derived from [CO2] and δ13Catm measurements from ice cores

    NASA Astrophysics Data System (ADS)

    Eggleston, S.; Schmitt, J.; Chappellaz, J. A.; Joos, F.; Fischer, H.

    2014-12-01

    Antarctic ice cores represent an invaluable source for understanding the climate of the past. Climatically important gases, including CO2, can be extracted from the ice and measured, thus providing atmospheric records for the past 800 kyr. Research has shown that atmospheric CO2 has varied naturally in conjunction with Antarctic air temperature. Additional knowledge of the variations of the stable carbon isotope of CO2, δ13Catm, can help us better understand the processes involved in these fluctuations. Here, we present a complete δ13Catm record extending from 160 kyrBP to the present. The present record, measured primarily on ice from the EPICA Dome C and Talos Dome ice cores, demonstrates a complex interplay of the ocean, terrestrial biosphere and atmosphere carbon reservoirs. For instance, a long-term increasing trend in δ13Catm, starting at the penultimate glacial maximum, extends well into MIS 4, while CO2 shows major drops already between 115 kyrBP and the MIS 5/4 boundary. In contrast, δ13Catm evolved roughly in antiphase during the MIS 4/3 transition with the atmospheric carbon storage increasing by 50 Gt while δ13Catm decreased by 0.5‰, a signal larger than that observed during the last glacial/interglacial termination. This antiphase relationship suggests that a single natural process or multiple processes acting on similar timescales may be responsible for this change in CO2. Modelling studies have shown that the ocean has the greatest impact on the concentration and stable isotope abundance of this greenhouse gas, in particular due to changes in stratification, upwelling, or marine productivity in the Southern Ocean. Similar to the situation at the onset of the last glacial/interglacial termination (Schmitt et al., 2012), the MIS 4/3 transition is characterized by the occurrence of a Heinrich event in the North Atlantic, presumably related to changes in the Atlantic Meridional Overturning Circulation and the upwelling of old carbon enriched

  20. Life-cycle energy and greenhouse gas emission benefits of lightweighting in automobiles: review and harmonization.

    PubMed

    Kim, Hyung Chul; Wallington, Timothy J

    2013-06-18

    Replacing conventional materials (steel and iron) with lighter alternatives (e.g., aluminum, magnesium, and composites) decreases energy consumption and greenhouse gas (GHG) emissions during vehicle use but may increase energy consumption and GHG emissions during vehicle production. There have been many life cycle assessment (LCA) studies on the benefits of vehicle lightweighting, but the wide variety of assumptions used makes it difficult to compare results from the studies. To clarify the benefits of vehicle lightweighting we have reviewed the available literature (43 studies). The GHG emissions and primary energy results from 33 studies that passed a screening process were harmonized using a common set of assumptions (lifetime distance traveled, fuel-mass coefficient, secondary weight reduction factor, fuel consumption allocation, recycling rate, and energy intensity of materials). After harmonization, all studies indicate that using aluminum, glass-fiber reinforced plastic, and high strength steel to replace conventional steel decreases the vehicle life cycle energy use and GHG emissions. Given the flexibility in options implied by the variety of materials available and consensus that these materials have substantial energy and emissions benefits, it seems likely that lightweighting will be used increasingly to improve fuel economy and reduce life cycle GHG emissions from vehicles. PMID:23668335

  1. Do radio mini-halos and gas heating in cool-core clusters have a common origin?

    NASA Astrophysics Data System (ADS)

    Bravi, L.; Gitti, M.; Brunetti, G.

    2016-01-01

    In this Letter, we present a study of the central regions of cool-core clusters hosting radio mini-halos, which are diffuse synchrotron sources extended on cluster-scales surrounding the radio-loud brightest cluster galaxy. We aim to investigate the interplay between the thermal and non-thermal components in the intracluster medium in order to get more insights into these radio sources, whose nature is still unclear. It has recently been proposed that turbulence plays a role for heating the gas in cool cores. By assuming that mini-halos are powered by the same turbulence, we expect that the integrated radio luminosity of mini-halos, νPν, depends on the cooling flow power, PCF, which in turn constrains the energy available for the non-thermal components and emission in the cool-core region. We carried out a homogeneous re-analysis of X-ray Chandra data of the largest sample of cool-core clusters hosting radio mini-halos currently available (˜20 objects), finding a quasi-linear correlation, ν P_{ν } ∝ P_CF^{0.8}. We show that the scenario of a common origin of radio mini-halos and gas heating in cool-core clusters is energetically viable, provided that mini-halos trace regions where the magnetic field strength is B ≫ 0.5 μG.

  2. Process based life-cycle assessment of natural gas from the Marcellus Shale.

    PubMed

    Dale, Alexander T; Khanna, Vikas; Vidic, Radisav D; Bilec, Melissa M

    2013-05-21

    The Marcellus Shale (MS) represents a large potential source of energy in the form of tightly trapped natural gas (NG). Producing this NG requires the use of energy and water, and has varying environmental impacts, including greenhouse gases. One well-established tool for quantifying these impacts is life-cycle assessment (LCA). This study collected information from current operating companies to perform a process LCA of production for MS NG in three areas--greenhouse gas (GHG) emissions, energy consumption, and water consumption--under both present (2011-2012) and past (2007-2010) operating practices. Energy return on investment (EROI) was also calculated. Information was collected from current well development operators and public databases, and combined with process LCA data to calculate per-well and per-MJ delivered impacts, and with literature data on combustion for calculation of impacts on a per-kWh basis during electricity generation. Results show that GHG emissions through combustion are similar to conventional natural gas, with an EROI of 12:1 (90% confidence interval of 4:1-13:1), lower than conventional fossil fuels but higher than unconventional oil sources. PMID:23611587

  3. The effects of temperature on the gas exchange cycle in Agathemera crassa.

    PubMed

    Thienel, Mariana; Canals, Mauricio; Bozinovic, Francisco; Veloso, Claudio

    2015-05-01

    Insects exhibit three patterns of gas exchange: continuous (CoGE), cyclic (CGE) and discontinuous (DGE). In this work, we present the first record of a DGE in Phasmatodea and its transition to CGE and to CoGE through a thermal gradient. The rate of CO2 production (VCO2) at 10, 20 and 30°C was examined in adults of Agathemera crassa, a high-Andean phasmid of central Chile. Carbon dioxide release was recorded during 24 h with L:D cycle of 12:12 h in order to record both rest and activity periods. At rest, A. crassa showed three patterns of gas exchange, highlighting the use of DGE preferably at 10°C. As the temperature increased, the CoGE pattern was more frequent being the only pattern observed in all individuals at 30°C. During activity, patterns changed to CoGE with a significant increase in VCO2. Our results support the idea that gas exchange patterns in insects are not distinct but correspond to a continuum of responses addressed by metabolic demand and where DGE can be expressed only under an absolute state of rest. Our results support the idea that the presence of the DGE may be underestimated in other insect taxa because they may have been measured under conditions where this pattern not necessarily can be expressed. PMID:25624164

  4. Gas desorption from seawater in open-cycle ocean thermal energy conversion barometric upcomers

    SciTech Connect

    Ghiaasiaan, S.M.; Wassel, A.T. ); Pesaran, A.A. )

    1990-08-01

    Gas desorption from warm and cold seawater under open-cycle ocean thermal energy conversion (OC-OTEC) conditions is addressed in this paper. The desorption process of dissolved O{sub 2}, N{sub 2}, and CO{sub 2} in the barometric upcomers of an OTEC plant is simulated mathematically. The model considers the growth of bubbles originating in the ocean and bubbles formed in the upcomers. Bubble growth is induced by gas mass transfer and water evaporation at the bubble-liquid interface, as well as by the decreasing hydrostatic pressure. Heterogeneous nucleation at pipe wall crevices and on suspended particles in the water stream is also modeled. Bubble coalescence due to turbulent shear and differential buoyancy is simulated. The results generated show the deaeration efficiency as a function of flow and geometric parameters. The calculations show that gas desorption in the barometric upcomers can be appreciable. Such desorption is enhanced by increasing the concentration of the incoming and/or the heterogeneously formed bubbles. Results of existing experiments are discussed and predictions are shown for the selected test conditions.

  5. Developing a data life cycle for carbon and greenhouse gas measurements: challenges, experiences and visions

    NASA Astrophysics Data System (ADS)

    Kutsch, W. L.

    2015-12-01

    Environmental research infrastructures and big data integration networks require common data policies, standardized workflows and sophisticated e-infrastructure to optimise the data life cycle. This presentation summarizes the experiences in developing the data life cycle for the Integrated Carbon Observation System (ICOS), a European Research Infrastructure. It will also outline challenges that still exist and visions for future development. As many other environmental research infrastructures ICOS RI built on a large number of distributed observational or experimental sites. Data from these sites are transferred to Thematic Centres and quality checked, processed and integrated there. Dissemination will be managed by the ICOS Carbon Portal. This complex data life cycle has been defined in detail by developing protocols and assigning responsibilities. Since data will be shared under an open access policy there is a strong need for common data citation tracking systems that allow data providers to identify downstream usage of their data so as to prove their importance and show the impact to stakeholders and the public. More challenges arise from interoperating with other infrastructures or providing data for global integration projects as done e.g. in the framework of GEOSS or in global integration approaches such as fluxnet or SOCAt. Here, common metadata systems are the key solutions for data detection and harvesting. The metadata characterises data, services, users and ICT resources (including sensors and detectors). Risks may arise when data of high and low quality are mixed during this process or unexperienced data scientists without detailed knowledge on the data aquisition derive scientific theories through statistical analyses. The vision of fully open data availability is expressed in a recent GEO flagship initiative that will address important issues needed to build a connected and interoperable global network for carbon cycle and greenhouse gas

  6. Life Cycle Greenhouse Gas Emissions of Crystalline Silicon Photovoltaic Electricity Generation: Systematic Review and Harmonization

    SciTech Connect

    Hsu, D. D.; O'Donoughue, P.; Fthenakis, V.; Heath, G. A.; Kim, H. C.; Sawyer, P.; Choi, J. K.; Turney, D. E.

    2012-04-01

    Published scientific literature contains many studies estimating life cycle greenhouse gas (GHG) emissions of residential and utility-scale solar photovoltaics (PVs). Despite the volume of published work, variability in results hinders generalized conclusions. Most variance between studies can be attributed to differences in methods and assumptions. To clarify the published results for use in decision making and other analyses, we conduct a meta-analysis of existing studies, harmonizing key performance characteristics to produce more comparable and consistently derived results. Screening 397 life cycle assessments (LCAs) relevant to PVs yielded 13 studies on crystalline silicon (c-Si) that met minimum standards of quality, transparency, and relevance. Prior to harmonization, the median of 42 estimates of life cycle GHG emissions from those 13 LCAs was 57 grams carbon dioxide equivalent per kilowatt-hour (g CO{sub 2}-eq/kWh), with an interquartile range (IQR) of 44 to 73. After harmonizing key performance characteristics, irradiation of 1,700 kilowatt-hours per square meter per year (kWh/m{sup 2}/yr); system lifetime of 30 years; module efficiency of 13.2% or 14.0%, depending on module type; and a performance ratio of 0.75 or 0.80, depending on installation, the median estimate decreased to 45 and the IQR tightened to 39 to 49. The median estimate and variability were reduced compared to published estimates mainly because of higher average assumptions for irradiation and system lifetime. For the sample of studies evaluated, harmonization effectively reduced variability, providing a clearer synopsis of the life cycle GHG emissions from c-Si PVs. The literature used in this harmonization neither covers all possible c-Si installations nor represents the distribution of deployed or manufactured c-Si PVs.

  7. Cycle development and design for CO2 capture from flue gas by vacuum swing adsorption.

    PubMed

    Zhang, Jun; Webley, Paul A

    2008-01-15

    CO2 capture and storage is an important component in the development of clean power generation processes. One CO2 capture technology is gas-phase adsorption, specifically pressure (or vacuum) swing adsorption. The complexity of these processes makes evaluation and assessment of new adsorbents difficult and time-consuming. In this study, we have developed a simple model specifically targeted at CO2 capture by pressure swing adsorption and validated our model by comparison with data from a fully instrumented pilot-scale pressure swing adsorption process. The model captures nonisothermal effects as well as nonlinear adsorption and nitrogen coadsorption. Using the model and our apparatus, we have designed and studied a large number of cycles for CO2 capture. We demonstrate that by careful management of adsorption fronts and assembly of cycles based on understanding of the roles of individual steps, we are able to quickly assess the effect of adsorbents and process parameters on capture performance and identify optimal operating regimes and cycles. We recommend this approach in contrast to exhaustive parametric studies which tend to depend on specifics of the chosen cycle and adsorbent. We show that appropriate combinations of process steps can yield excellent process performance and demonstrate how the pressure drop, and heat loss, etc. affect process performance through their effect on adsorption fronts and profiles. Finally, cyclic temperature profiles along the adsorption column can be readily used to infer concentration profiles-this has proved to be a very useful tool in cyclic function definition. Our research reveals excellent promise for the application of pressure/vacuum swing adsorption technology in the arena of CO2 capture from flue gases. PMID:18284163

  8. A Computational Fluid Dynamic and Heat Transfer Model for Gaseous Core and Gas Cooled Space Power and Propulsion Reactors

    NASA Technical Reports Server (NTRS)

    Anghaie, S.; Chen, G.

    1996-01-01

    A computational model based on the axisymmetric, thin-layer Navier-Stokes equations is developed to predict the convective, radiation and conductive heat transfer in high temperature space nuclear reactors. An implicit-explicit, finite volume, MacCormack method in conjunction with the Gauss-Seidel line iteration procedure is utilized to solve the thermal and fluid governing equations. Simulation of coolant and propellant flows in these reactors involves the subsonic and supersonic flows of hydrogen, helium and uranium tetrafluoride under variable boundary conditions. An enthalpy-rebalancing scheme is developed and implemented to enhance and accelerate the rate of convergence when a wall heat flux boundary condition is used. The model also incorporated the Baldwin and Lomax two-layer algebraic turbulence scheme for the calculation of the turbulent kinetic energy and eddy diffusivity of energy. The Rosseland diffusion approximation is used to simulate the radiative energy transfer in the optically thick environment of gas core reactors. The computational model is benchmarked with experimental data on flow separation angle and drag force acting on a suspended sphere in a cylindrical tube. The heat transfer is validated by comparing the computed results with the standard heat transfer correlations predictions. The model is used to simulate flow and heat transfer under a variety of design conditions. The effect of internal heat generation on the heat transfer in the gas core reactors is examined for a variety of power densities, 100 W/cc, 500 W/cc and 1000 W/cc. The maximum temperature, corresponding with the heat generation rates, are 2150 K, 2750 K and 3550 K, respectively. This analysis shows that the maximum temperature is strongly dependent on the value of heat generation rate. It also indicates that a heat generation rate higher than 1000 W/cc is necessary to maintain the gas temperature at about 3500 K, which is typical design temperature required to achieve high

  9. Toward Generation of High Power Ultrafast White Light Laser Using Femtosecond Terawatt Laser in a Gas-Filled Hollow-Core Fiber

    NASA Astrophysics Data System (ADS)

    Tawfik, Walid

    2015-06-01

    In this work, we could experimentally achieved the generation of white-light laser pulses of few-cycle fs pulses using a neon-filled hollow-core fiber. The observed pulses reached 6-fs at at repetition rate of 1 kHz using 2.5 mJ of 31 fs femtosecond pulses. The pulse compressing achieved by the supercontinuum produced in static neon-filled hollow fibers while the dispersion compensation is achieved by five pairs of chirped mirrors. We showed that gas pressure can be used to continuously vary the bandwidth from 350 nm to 900 nm. Furthermore, the applied technique allows for a straightforward tuning of the pulse duration via the gas pressure whilst maintaining near-transform-limited pulses with constant output energy, thereby reducing the complications introduced by chirped pulses. Through measurements of the transmission through the fiber as a function of gas pressure, a high throughput exceeding 60% was achieved. Adaptive pulse compression is achieved by using the spectral phase obtained from a spectral phase interferometry for direct electric field reconstruction (SPIDER) measurement as feedback for a liquid crystal spatial light modulator (SLM). The spectral phase of these supercontinua is found to be extremely stable over several hours. This allowed us to demonstrate successful compression to pulses as short as 5.2 fs with controlled wide spectral bandwidth, which could be used to excite different states in complicated molecules at once.

  10. [Reliability of Selected Parameters of Cycling Ergospirometry from the PowerCube-Ergo Respiratory Gas Analyser].

    PubMed

    Hoppe, M W; Sperlich, B; Baumgart, C; Janssen, M; Freiwald, J

    2015-09-01

    This study aimed to investigate the reliability of 1) the key parameters of cycling ergospirometry (maximum power output [Pmax] and oxygen uptake [V̇O2peak], ventilatory thresholds 1 [VT 1] and 2 [VT 2], and cycling efficiency [CE] and gross efficiency [GE]), 2) the commonly used parameters to quantify exhaustion (maximum heart rate [HFmax], respiratory quotient [RQmax], blood lactate concentration [BLAmax], and ratings of perceived exhaustion [RPEmax]), and 3) the kinetics of exercise induced gas exchange measurements (oxygen uptake [V̇O2], carbon dioxide output [V̇CO2], and minute ventilation [V̇E]) using the PowerCube-Ergo metabolic system in consideration of international statistical recommendations. 12 women and 12 men (28 ± 4 years; 23.2 ± 2.4 kg/m(2)) performed two cycling tests (20 watt/min) separated by one week. The reliability was calculated based on differences in means (t test and effect sizes), retest correlation (intraclass correlation coefficient [ICC]), and within-subject variation (standard error of measurement [SEM]). Of the key parameters of cycling ergospirometry, an excellent reliability (ICC ≥ 0.969; p = 0.000) and high accuracy (%SEM ≤ 4.6) were found for Pmax, V̇O2peak, and VT 1. Of the most commonly used parameters to quantify exhaustion, an excellent reliability (ICC = 0.922; p = 0.000) and high accuracy (%SEM = 1.0) existed only for HFmax. The gas exchange measurements (V̇O2, V̇CO2 und V̇E) of the PowerCube-Ergo were all excellently reliable (ICC ≥ 0,991; p = 0.000) and the accuracy of V̇O2 (SEM = 0.10 l/min) and V̇E (SEM = 3.13 l/min) fulfilled the quality guidance of exercise physiology laboratories. For future studies and practical purposes, the results are vital for the decision as to whether a difference between two tests represents a true intervention effect or just a measurement error and for the estimation of required sample sizes. PMID:25710394

  11. A scenario analysis of the life cycle greenhouse gas emissions of a new residential area

    NASA Astrophysics Data System (ADS)

    Säynäjoki, Antti; Heinonen, Jukka; Junnila, Seppo

    2012-09-01

    While buildings are often credited as accounting for some 40% of the global greenhouse gas (GHG) emissions, the construction phase is typically assumed to account for only around one tenth of the overall emissions. However, the relative importance of construction phase emissions is quickly increasing as the energy efficiency of buildings increases. In addition, the significance of construction may actually be much higher when the temporal perspective of the emissions is taken into account. The construction phase carbon spike, i.e. high GHG emissions in a short time associated with the beginning of the building’s life cycle, may be high enough to question whether new construction, no matter how energy efficient the buildings are, can contribute to reaching the greenhouse gas mitigation goals of the near future. Furthermore, the construction of energy efficient buildings causes more GHG emissions than the construction of conventional buildings. On the other hand, renovating the current building stock together with making energy efficiency improvements might lead to a smaller construction phase carbon spike and still to the same reduced energy consumption in the use phase as the new energy efficient buildings. The study uses a new residential development project in Northern Europe to assess the overall life cycle GHG emissions of a new residential area and to evaluate the influence of including the temporal allocation of the life cycle GHG emissions in the assessment. In the study, buildings with different energy efficiency levels are compared with a similar hypothetical area of buildings of the average existing building stock, as well as with a renovation of an area with average buildings from the 1960s. The GHG emissions are modeled with a hybrid life cycle assessment. The study suggests that the carbon payback time of constructing new residential areas is several decades long even when using very energy efficient buildings compared to utilizing the current

  12. High harmonic generation in a gas-filled hollow-core photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Heckl, O. H.; Baer, C. R. E.; Kränkel, C.; Marchese, S. V.; Schapper, F.; Holler, M.; Südmeyer, T.; Robinson, J. S.; Tisch, J. W. G.; Couny, F.; Light, P.; Benabid, F.; Keller, U.

    2009-10-01

    :270, 2007). The interaction between the laser pulses and the gas occurs in a Kagome-type Hollow-Core Photonic Crystal Fiber (HC-PCF) (Benabid et al., Science 298:399, 2002), which reduces the detection threshold for HHG to only 200 nJ. This novel type of fiber guides nearly all of the light in the hollow core (Couny et al., Science 318:1118, 2007), preventing damage even at intensities required for HHG. Our fiber guided 30-fs pulses with a pulse energy of more than 10 μJ, which is more than five times higher than for any other photonic crystal fiber (Hensley et al., Conference on Lasers and Electro-Optics (CLEO), IEEE Press, New York, 2008).

  13. How to quantify uncertainty and variability in life cycle assessment: the case of greenhouse gas emissions of gas power generation in the US

    NASA Astrophysics Data System (ADS)

    Hauck, M.; Steinmann, Z. J. N.; Laurenzi, I. J.; Karuppiah, R.; Huijbregts, M. A. J.

    2014-07-01

    This study quantified the contributions of uncertainty and variability to the range of life-cycle greenhouse gas (LCGHG) emissions associated with conventional gas-fired electricity generation in the US. Whereas uncertainty is defined as lack of knowledge and can potentially be reduced by additional research, variability is an inherent characteristic of supply chains and cannot be reduced without physically modifying the system. The life-cycle included four stages: production, processing, transmission and power generation, and utilized a functional unit of 1 kWh of electricity generated at plant. Technological variability requires analyses of life cycles of individual power plants, e.g. combined cycle plants or boilers. Parameter uncertainty was modeled via Monte Carlo simulation. Our approach reveals that technological differences are the predominant cause for the range of LCGHG emissions associated with gas power, primarily due to variability in plant efficiencies. Uncertainties in model parameters played a minor role for 100 year time horizon. Variability in LCGHG emissions was a factor of 1.4 for combined cycle plants, and a factor of 1.3 for simple cycle plants (95% CI, 100 year horizon). The results can be used to assist decision-makers in assessing factors that contribute to LCGHG emissions despite uncertainties in parameters employed to estimate those emissions.

  14. Enhanced performance of core-shell structured polyaniline at helical carbon nanotube hybrids for ammonia gas sensor

    SciTech Connect

    Tian, Xin; Wang, Qiang; Chen, Xiangnan; Yang, Weiqing; Xu, Xiaoling E-mail: bihan-2001@163.com; Jiang, Man; Zhou, Zuowan E-mail: bihan-2001@163.com; Wu, Zuquan

    2014-11-17

    A core-shell structured hybrid of polyaniline at helical carbon nanotubes was synthesized using in situ polymerization, which the helical carbon nanotubes were uniformly surrounded by a layer of polyaniline nanorods array. More interestingly, repeatable responses were experimentally observed that the sensitivity to ammonia gas of the as-prepared helical shaped core-shell hybrid displays an enhancement of more than two times compared to those of only polyaniline or helical carbon nanotubes sensors because of the peculiar structures with high surface area. This kind of hybrid comprising nanorod arrays of conductive polymers covering carbon nanotubes and related structures provide a potential in sensors of trace gas detection for environmental monitoring and safety forecasting.

  15. Simulation of existing gas-fuelled conventional steam power plant using Cycle Tempo

    NASA Astrophysics Data System (ADS)

    Jamel, M. S.; Abd Rahman, A.; Shamsuddin, A. H.

    2013-06-01

    Simulation of a 200 MW gas-fuelled conventional steam power plant located in Basra, Iraq was carried out. The thermodynamic performance of the considered power plant is estimated by a system simulation. A flow-sheet computer program, "Cycle-Tempo" is used for the study. The plant components and piping systems were considered and described in detail. The simulation results were verified against data gathered from the log sheet obtained from the station during its operation hours and good results were obtained. Operational factors like the stack exhaust temperature and excess air percentage were studied and discussed, as were environmental factors, such as ambient air temperature and water inlet temperature. In addition, detailed exergy losses were illustrated and describe the temperature profiles for the main plant components. The results prompted many suggestions for improvement of the plant performance.

  16. Reducing Uncertainty in Life Cycle CH4 Emissions from Natural Gas using Atmospheric Inversions

    NASA Astrophysics Data System (ADS)

    Schwietzke, S.; Griffin, W.; Matthews, S.

    2012-12-01

    Methane emissions associated with the production and use of natural gas (NG) are highly uncertain because of challenges to accurately measure fugitive CH4 emissions from NG leaks and venting throughout a large and complex industry. Better understanding the CH4 emissions from the NG life cycle is important for two reasons. First, the rising interest in NG use associated with the recent development of unconventional sources, such as shale gas, may cause a shift in the future energy system from coal towards more NG. Given its relatively high greenhouse gas potency, fugitive CH4 emissions from the NG life cycle have the potential to outweigh lower CO2 emissions compared to coal use in terms of their climate impacts over the next few decades. Second, worldwide NG related CH4 emissions play a key role in understanding the global CH4 budget. According to current atmospheric inversion studies, NG and oil production account for about 12% of global CH4 emissions. However, these results largely depend on prior emissions estimates whose uncertainties are poorly documented. The objective of this research is to analyze which ranges of global fugitive CH4 emissions from the NG life cycle are reasonable given atmospheric observations as a constraint. We establish a prior global CH4 inventory for NG, oil, and coal using emissions data from the life cycle assessment (LCA) literature. This inventory includes uncertainty estimates for different fuels, world regions, and time periods based on LCA literature, which existing inventories do not account for. Furthermore, global CH4 inversion modeling will be used to test bottom-up hypotheses of high NG leakage and venting associated with the upper bound of the prior inventory. Given the use of detailed LCA emissions factors, we will test bottom-up scenarios regarding management and technology improvements over time. The emissions inventory will be established for the past decade, and inversion modeling will be carried out using NOAA

  17. MORECA: A computer code for simulating modular high-temperature gas-cooled reactor core heatup accidents

    SciTech Connect

    Ball, S.J. )

    1991-10-01

    The design features of the modular high-temperature gas-cooled reactor (MHTGR) have the potential to make it essentially invulnerable to damage from postulated core heatup accidents. This report describes the ORNL MORECA code, which was developed for analyzing postulated long-term core heatup scenarios for which active cooling systems used to remove afterheat following the accidents can be assumed to the unavailable. Simulations of long-term loss-of-forced-convection accidents, both with and without depressurization of the primary coolant, have shown that maximum core temperatures stay below the point at which any significant fuel failures and fission product releases are expected. Sensitivity studies also have been done to determine the effects of errors in the predictions due both to uncertainties in the modeling and to the assumptions about operational parameters. MORECA models the US Department of Energy reference design of a standard MHTGR.

  18. Engineering high-performance Pd core-MgO porous shell nanocatalysts via heterogeneous gas-phase synthesis.

    PubMed

    Singh, Vidyadhar; Cassidy, Cathal; Abild-Pedersen, Frank; Kim, Jeong-Hwan; Aranishi, Kengo; Kumar, Sushant; Lal, Chhagan; Gspan, Christian; Grogger, Werner; Sowwan, Mukhles

    2015-08-28

    We report on the design and synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core-MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell. PMID:26203627

  19. Density fluctuations of a hard-core Bose gas in a one-dimensional lattice near the Mott insulating phase

    SciTech Connect

    Ates, C.; Moseley, Ch.; Ziegler, K.

    2005-06-15

    The characteristic oscillations of the density-density correlation function and the resulting structure factor are studied for a hard-core Bose gas in a one-dimensional lattice. Their wavelength diverges as the system undergoes a continuous transition from an incommensurate to a Mott insulating phase. The transition is associated with a unit static structure factor and a vanishing sound velocity. The qualitative picture is unchanged when a weak confining potential is applied to the system.

  20. Permo-Carboniferous magmatism in the core of Pangaea (Southern Pyrenees): a possible linkage between the Variscan and Cimmerian cycles?

    NASA Astrophysics Data System (ADS)

    Francisco Pereira, M.; Castro, Antonio; Chichorro, Martim; Fernandez, Carlos; Diaz-Alvarado, Juan; Martí, Joan; Rodríguez, Carmen

    2013-04-01

    In southern Europe and the western Mediterranean, Permo-Carboniferous magmatism is well represented in areas of Iberia, the Alps, Sardinia and the Balkan Peninsula. In Iberia, the magmatism that has been related to the Variscan orogeny is associated with syn-orogenic events at ca. 350-315 Ma and post-orogenic at ca. 310-295 Ma. In the southern Pyrenees there is Permo-Carboniferous sedimentary basins with a significant volume of rhyolitic ignimbrites and andesitic flows. The Erill Castell-Estac, Cadí and Castellar de n'Hug basins are spatially associated with the Boí, Montellá and Vielha granites and the Cardet dacitic dykes emplaced in Variscan basement rocks. U-Pb SHRIMP dating of zircons extracted from these granites, an andesitic flow, a dacitic dyke and six ignimbrites, revealed that magmatism was active from ca. 304 Ma to ca. 266 Ma. The scattering of zircon ages in each sample shows that the history of melt crystallization was prolonged and complex. The reported ages of the magmatic activity for the Southern Pyrenees in the range ca. 304-283 Ma (this study) fit in well with the time interval of magmatism related to the early North-dipping subduction of the Western Paleotethys Ocean, the subsequent development of Iberian orocline (Variscan cycle), and the large-scale bending and blocking of the Paleotethys Ocean subduction at East of Iberia. In paleogeographic reconstructions of the Permo-Carboniferous, Iberia is located in the core of Pangaea to the east of the probable Rheic Ocean suture and near the western end of the subduction zone of the Paleotethys Ocean. The emplacement in Iberia of granites with ca. 310-278 Ma age occurred after the collision of Laurussia and Gondwana, when the subduction of the Rheic Ocean was inactive. From a Variscan-cycle perspective, the Permo-Carboniferous magmatism of the Pyrenees has been considered as post-orogenic. However, global paleogeographic reconstructions put Iberia in between the Rheic Ocean suture and the still

  1. Experimental transient turbine blade temperatures in a research engine for gas stream temperatures cycling between 1067 and 1567 k

    NASA Technical Reports Server (NTRS)

    Gauntner, D. J.; Yeh, F. C.

    1975-01-01

    Experimental transient turbine blade temperatures were obtained from tests conducted on air-cooled blades in a research turbojet engine, cycling between cruise and idle conditions. Transient data were recorded by a high speed data acquisition system. Temperatures at the same phase of each transient cycle were repeatable between cycles to within 3.9 K (7 F). Turbine inlet pressures were repeatable between cycles to within 0.32 N/sq cm (0.47 psia). The tests were conducted at a gas stream temperature of 1567 K (2360 F) at cruise, and 1067 K (1460 F) at idle conditions. The corresponding gas stream pressures were about 26.2 and 22.4 N/sq cm (38 and 32.5 psia) respectively. The nominal coolant inlet temperature was about 811 K (1000 F).

  2. SOLUBILITY OF WATER ICE IN METALLIC HYDROGEN: CONSEQUENCES FOR CORE EROSION IN GAS GIANT PLANETS

    SciTech Connect

    Wilson, H. F.; Militzer, B.

    2012-01-20

    Using ab initio simulations we investigate whether water ice is stable in the cores of giant planets, or whether it dissolves into the layer of metallic hydrogen above. By Gibbs free energy calculations we find that for pressures between 10 and 40 Mbar the ice-hydrogen interface is thermodynamically unstable at temperatures above approximately 3000 K, far below the temperature of the core-mantle boundaries in Jupiter and Saturn. This implies that the dissolution of core material into the fluid layers of giant planets is thermodynamically favored, and that further modeling of the extent of core erosion is warranted.

  3. Comparison between parameters from maximal cycle ergometer test first without respiratory gas analysis and thereafter with respiratory gas analysis among healthy prepubertal children.

    PubMed

    Tompuri, Tuomo T; Lintu, Niina; Soininen, Sonja; Laitinen, Tomi; Lakka, Timo Antero

    2016-06-01

    It is important to distinguish true and clinically relevant changes and methodological noise from measure to measure. In the clinical practice, maximal cycle ergometer tests are typically performed first without respiratory gas analysis and thereafter, if needed, with respiratory gas analysis. Therefore, we report a comparison of parameters from maximal cycle ergometer exercise tests that were done first without respiratory gas analysis and thereafter with it in 38 prepubertal and healthy children (20 girls, 18 boys). The Bland-Altman method was used to assess agreement in maximal workload (WMAX), heart rate (HR), and systolic blood pressure (SBP) between rest and maximum. Girls achieved higher WMAX in the exercise tests with respiratory gas analysis compared with exercise tests without respiratory gas analysis (p = 0.016), whereas WMAX was similar in the tests among boys. Maximal HR (proportional offset, -1%; coefficients of variation, 3.3%) and highest SBP (proportional offset, 3%; coefficients of variation, 10.6%) were similar in the tests among children. Precision and agreement for HR improved and precision for SBP worsened with increasing exercise intensity. Heteroscedasticity was not observed for WMAX, HR, or SBP. We conclude that maximal cycle ergometer tests without and with respiratory gas analysis can be used consecutively because measurement of respiratory gases did not impair performance or have a significant effect on the maximality of the exercise tests. Our results suggest that similar references can be used for children who accept or refuse using a mask during a maximal exercise test. PMID:27163556

  4. Engineering high-performance Pd core-MgO porous shell nanocatalysts via heterogeneous gas-phase synthesis

    NASA Astrophysics Data System (ADS)

    Singh, Vidyadhar; Cassidy, Cathal; Abild-Pedersen, Frank; Kim, Jeong-Hwan; Aranishi, Kengo; Kumar, Sushant; Lal, Chhagan; Gspan, Christian; Grogger, Werner; Sowwan, Mukhles

    2015-08-01

    We report on the design and synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core-MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell.We report on the design and synthesis of high performance catalytic nanoparticles with a robust geometry via magnetron-sputter inert-gas condensation. Sputtering of Pd and Mg from two independent neighbouring targets enabled heterogeneous condensation and growth of nanoparticles with controlled Pd core-MgO porous shell structure. The thickness of the shell and the number of cores within each nanoparticle could be tailored by adjusting the respective sputtering powers. The nanoparticles were directly deposited on glassy carbon electrodes, and their catalytic activity towards methanol oxidation was examined by cyclic voltammetry. The measurements indicated that the catalytic activity was superior to conventional bare Pd nanoparticles. As confirmed by electron microscopy imaging and supported by density-functional theory (DFT) calculations, we attribute the improved catalytic performance primarily to inhibition of Pd core sintering during the catalytic process by the metal-oxide shell

  5. A demand-centered, hybrid life-cycle methodology for city-scale greenhouse gas inventories.

    PubMed

    Ramaswami, Anu; Hillman, Tim; Janson, Bruce; Reiner, Mark; Thomas, Gregg

    2008-09-01

    Greenhouse gas (GHG) accounting for individual cities is confounded by spatial scale and boundary effects that impact the allocation of regional material and energy flows. This paper develops a demand-centered, hybrid life-cycle-based methodology for conducting city-scale GHG inventories that incorporates (1) spatial allocation of surface and airline travel across colocated cities in larger metropolitan regions, and, (2) life-cycle assessment (LCA) to quantify the embodied energy of key urban materials--food, water, fuel, and concrete. The hybrid methodology enables cities to separately report the GHG impact associated with direct end-use of energy by cities (consistent with EPA and IPCC methods), as well as the impact of extra-boundary activities such as air travel and production of key urban materials (consistent with Scope 3 protocols recommended by the World Resources Institute). Application of this hybrid methodology to Denver, Colorado, yielded a more holistic GHG inventory that approaches a GHG footprint computation, with consistency of inclusions across spatial scale as well as convergence of city-scale per capita GHG emissions (approximately 25 mt CO2e/person/year) with state and national data. The method is shown to have significant policy impacts, and also demonstrates the utility of benchmarks in understanding energy use in various city sectors. PMID:18800514

  6. Life cycle assessment of greenhouse gas emissions from plug-in hybrid vehicles: implications for policy.

    PubMed

    Samaras, Constantine; Meisterling, Kyle

    2008-05-01

    Plug-in hybrid electric vehicles (PHEVs), which use electricity from the grid to power a portion of travel, could play a role in reducing greenhouse gas (GHG) emissions from the transport sector. However, meaningful GHG emissions reductions with PHEVs are conditional on low-carbon electricity sources. We assess life cycle GHG emissions from PHEVs and find that they reduce GHG emissions by 32% compared to conventional vehicles, but have small reductions compared to traditional hybrids. Batteries are an important component of PHEVs, and GHGs associated with lithium-ion battery materials and production account for 2-5% of life cycle emissions from PHEVs. We consider cellulosic ethanol use and various carbon intensities of electricity. The reduced liquid fuel requirements of PHEVs could leverage limited cellulosic ethanol resources. Electricity generation infrastructure is long-lived, and technology decisions within the next decade about electricity supplies in the power sector will affectthe potential for large GHG emissions reductions with PHEVs for several decades. PMID:18522090

  7. Meta-Analysis of Estimates of Life Cycle Greenhouse Gas Emissions from Concentrating Solar Power: Preprint

    SciTech Connect

    Heath, G. A.; Burkhardt, J. J.

    2011-09-01

    In reviewing life cycle assessment (LCA) literature of utility-scale CSP systems, this analysis focuses on clarifying central tendency and reducing variability in estimates of life cycle greenhouse gas (GHG) emissions through a meta-analytical process called harmonization. From 125 references reviewed, 10 produced 36 independent GHG emission estimates passing screens for quality and relevance: 19 for parabolic trough technology and 17 for power tower technology. The interquartile range (IQR) of published GHG emission estimates was 83 and 20 g CO2eq/kWh for trough and tower, respectively, with medians of 26 and 38 g CO2eq/kWh. Two levels of harmonization were applied. Light harmonization reduced variability in published estimates by using consistent values for key parameters pertaining to plant design and performance. Compared to the published estimates, IQR was reduced by 69% and median increased by 76% for troughs. IQR was reduced by 26% for towers, and median was reduced by 34%. A second level of harmonization was applied to five well-documented trough LC GHG emission estimates, harmonizing to consistent values for GHG emissions embodied in materials and from construction activities. As a result, their median was further reduced by 5%, while the range increased by 6%. In sum, harmonization clarified previous results.

  8. Evaluating greenhouse gas impacts of organic waste management options using life cycle assessment.

    PubMed

    Kong, Dung; Shan, Jilei; Iacoboni, Mario; Maguin, Stephen R

    2012-08-01

    Efforts to divert organics away from landfills are viewed by many as an important measure to significantly reduce the climate change impacts of municipal solid waste management. However, the actual greenhouse gas (GHG) impacts of organics diversion from landfills have yet to be thoroughly evaluated and whether such a diversion provides significant environmental benefits in terms of GHG impacts must be answered. This study, using California-specific information, aimed to analyse the GHG impacts of organics diversion through a life-cycle assessment (LCA). This LCA considered all aspects of organics management including transportation, materials handling, GHG emissions, landfill gas capture/utilization, energy impacts, and carbon sequestration. The LCA study evaluated overall GHG impacts of landfilling, and alternative management options such as composting and anaerobic digestion for diverted organic waste. The LCA analysis resulted in net GHG reductions of 0.093, 0.048, 0.065 and 0.073 tonnes carbon equivalent per tonne organic waste for landfilling, windrow composting, aerated static pile composting, and anaerobic digestion, respectively. This study confirms that all three options for organics management result in net reductions of GHG emissions, but it also shows that organics landfilling, when well-managed, generates greater GHG reductions. The LCA provides scientific insight with regards to the environmental impacts of organics management options, which should be considered in decision and policy-making. The study also highlights the importance of how site and case-specific conditions influence project outcomes when considering organic waste management options. PMID:22588112

  9. The impact of 'Cash for Clunkers' on greenhouse gas emissions: a life cycle perspective

    NASA Astrophysics Data System (ADS)

    Lenski, Shoshannah M.; Keoleian, Gregory A.; Bolon, Kevin M.

    2010-10-01

    One of the goals of the US Consumer Assistance to Recycle and Save (CARS) Act of 2009, more commonly known as 'Cash for Clunkers', was to improve the US vehicle fleet fuel efficiency. Previous studies of the program's environmental impact have focused mainly on the effect of improved fuel economy, and the resulting reductions in fuel use and emissions during the vehicle use phase. We propose and apply a method for analyzing the net effect of CARS on greenhouse gas emissions from a full vehicle life cycle perspective, including the impact of premature production and retirement of vehicles. We find that CARS had a one-time effect of preventing 4.4 million metric tons of CO2-equivalent emissions, about 0.4% of US annual light-duty vehicle emissions. Of these, 3.7 million metric tons are avoided during the period of the expected remaining life of the inefficient 'clunkers'. 1.5 million metric tons are avoided as consumers purchase vehicles that are more efficient than their next replacement vehicle would otherwise have been. An additional 0.8 million metric tons are emitted as a result of premature manufacturing and disposal of vehicles. These results are sensitive to the remaining lifetime of the 'clunkers' and to the fuel economy of new vehicles in the absence of CARS, suggesting important considerations for policymakers deliberating on the use of accelerated vehicle retirement programs as a part of the greenhouse gas emissions policy.

  10. Obliquity-Controlled Water Vapor/Trace Gas Feedback in the Martian Greenhouse Cycle

    NASA Astrophysics Data System (ADS)

    Mischna, M. A.; Baker, V. R.; Milliken, R.; Richardson, M. I.; Lee, C.

    2013-12-01

    We have explored possible mechanisms for the generation of warm, wet climates on early Mars as a result of greenhouse warming by both water vapor and periodic volcanic trace gas emissions, using the Mars Weather Research and Forecasting (MarsWRF) general circulation model. The presence of both water vapor (a strong greenhouse gas) and other trace greenhouse gases (such as SO2) in a predominantly CO2 atmosphere may act, under certain conditions, to elevate surface temperatures above the freezing point of liquid water, at least episodically. The levels of warming obtained in our simulations do not reach the values seen in Johnson et al., (2008, JGR, 113, E08005), nor are they widespread for extended periods. Rather, warming above 273 K is found in more localized environments and for geologically brief periods of time. Such periodic episodes are controlled by two factors. First is the obliquity of the planet, which plays a significant role is ';activating' extant surface water ice reservoirs, allowing levels of atmospheric water vapor to rise when obliquity is high, and fall precipitously when the obliquity is low. During these low-obliquity periods, the atmosphere is all but incapable of supporting warm surface temperatures except for brief episodes localized wholly in the tropics; thus, there is a natural regulator in the obliquity cycle for maintaining periodic warming. Second is the presence of a secondary trace gas 'trigger', like volcanically released SO2, in the atmosphere. In the absence of such a trace gas, water vapor alone appears incapable of raising temperatures above the melting point; however, by temporarily raising the baseline global temperatures (in the absence of warming by water vapor) by 10-15 K, as with SO2, the trigger gas keeps atmospheric temperatures sufficiently warm, especially during nighttime, to maintain levels of water vapor in the atmosphere that provide the needed warming. Furthermore, we find that global warming can be achieved more

  11. Hi Gas Cycles and Lyman Continuum Optical Depth in Low-Redshift Starbursts

    NASA Astrophysics Data System (ADS)

    Jaskot, Anne Elizabeth

    Neutral gas both fuels star formation and determines the propagation of ionizing photons. In this work, we reveal the interactions between H I, star formation, and radiative feedback in two samples of low-redshift starbursts. Using the ALFALFA-Halpha sample, we present the first comparison of starbursts and non-starbursts within a statistically uniform, H I-selected sample. The moderate H I gas fractions of the starbursts relative to non-starbursts indicate efficient HI to H2 conversion and show that the H I supply is largely unaffected by ionizing radiation. Mergers may trigger the more massive starbursts, while the absence of obvious kinematical disturbances in dwarf starbursts may indicate periodic starburst activity, triggered by cycles of gas expulsion and re-accretion. While the ALFALFA-Halpha galaxies demonstrate that starbursts may maintain large H I reservoirs, the more powerful starbursts in the Green Pea (GP) galaxies illustrate the effects of extreme radiative feedback on neutral gas. To investigate whether the enormous [O III]/[O II] ratios in the most extreme GPs indicate LyC escape, we use photoionization modeling to constrain their ionizing sources and optical depths. Radiation from Wolf-Rayet stars or unusually hot O stars reproduces the observed [O III]/[O II] ratios, but no clear signatures of these stars are present. The GP spectra do suggest the presence of shocks, however, and accounting for shock emission necessitates a low optical depth. We therefore suggest that the GPs may be a new class of low-redshift LyC Emitters (LCEs), and we evaluate this scenario using Hubble Space Telescope COS spectra of four GPs. With these spectra, we develop a simple physical picture of the neutral gas optical depth and geometry that explains the previously enigmatic link between Lyalpha, Si II, and Si II* lines observed in high-redshift Lyalpha Emitters. Two GPs are likely optically thin along the line of sight, and their strong, narrow Lyalpha emission, weak

  12. Effects of Hydrogen Gas Environment on Fatigue Strength at 107 cycles in Plain Specimen of Type 316L Stainless Steel

    NASA Astrophysics Data System (ADS)

    Kawamoto, Kyohei; Ochi, Kazuhiko; Oda, Yasuji; Noguchi, Hiroshi

    In order to clarify the hydrogen effect on the fatigue strength at 107 cycles in a plain specimen of type 316L austenitic stainless steel, rotating bending fatigue tests in laboratory air and plane bending fatigue tests in 1.0 MPa dry hydrogen gas and in air at 313 K were carried out. The main results obtained are as follows. The observed fatigue behavior showed that the fatigue strength at 107 cycles in both environments is determined by the non-propagation of a fatigue crack of the order of the grain size. Also, the strength at 107 cycles in hydrogen gas is slightly higher than that in air. In the region of high-cycle fatigue, the fatigue life in hydrogen gas is longer than that in air, which is mainly caused by the longer crack initiation life in hydrogen gas. The crack propagation life in hydrogen gas is shorter than that in air but has only a small ratio to the fatigue life in this region.

  13. Compact and Robust Refilling and Connectorization of Hollow Core Photonic Crystal Fiber Gas Reference Cells

    NASA Technical Reports Server (NTRS)

    Poberezhskiy, Ilya Y.; Meras, Patrick; Chang, Daniel H.; Spiers, Gary D.

    2007-01-01

    A simple method for evacuating, refilling and connectorizing hollow-core photonic crystal fiber for use asgas reference cell is proposed and demonstrated. It relies on torch-sealing a quartz filling tube connected to amechanical splice between regular and hollow-core fibers.

  14. Life cycle greenhouse gas impacts of ethanol, biomethane and limonene production from citrus waste

    NASA Astrophysics Data System (ADS)

    Pourbafrani, Mohammad; McKechnie, Jon; MacLean, Heather L.; Saville, Bradley A.

    2013-03-01

    The production of biofuel from cellulosic residues can have both environmental and financial benefits. A particular benefit is that it can alleviate competition for land conventionally used for food and feed production. In this research, we investigate greenhouse gas (GHG) emissions associated with the production of ethanol, biomethane, limonene and digestate from citrus waste, a byproduct of the citrus processing industry. The study represents the first life cycle-based evaluations of citrus waste biorefineries. Two biorefinery configurations are studied—a large biorefinery that converts citrus waste into ethanol, biomethane, limonene and digestate, and a small biorefinery that converts citrus waste into biomethane, limonene and digestate. Ethanol is assumed to be used as E85, displacing gasoline as a light-duty vehicle fuel; biomethane displaces natural gas for electricity generation, limonene displaces acetone in solvents, and digestate from the anaerobic digestion process displaces synthetic fertilizer. System expansion and two allocation methods (energy, market value) are considered to determine emissions of co-products. Considerable GHG reductions would be achieved by producing and utilizing the citrus waste-based products in place of the petroleum-based or other non-renewable products. For the large biorefinery, ethanol used as E85 in light-duty vehicles results in a 134% reduction in GHG emissions compared to gasoline-fueled vehicles when applying a system expansion approach. For the small biorefinery, when electricity is generated from biomethane rather than natural gas, GHG emissions are reduced by 77% when applying system expansion. The life cycle GHG emissions vary substantially depending upon biomethane leakage rate, feedstock GHG emissions and the method to determine emissions assigned to co-products. Among the process design parameters, the biomethane leakage rate is critical, and the ethanol produced in the large biorefinery would not meet EISA

  15. The impact of soil amendments on greenhouse gas emissions: a comprehensive life cycle assessment approach

    NASA Astrophysics Data System (ADS)

    DeLonge, M. S.; Ryals, R.; Silver, W. L.

    2011-12-01

    Soil amendments, such as compost and manure, can be applied to grasslands to improve soil conditions and enhance aboveground net primary productivity. Applying such amendments can also lead to soil carbon (C) sequestration and, when materials are diverted from waste streams (e.g., landfills, manure lagoons), can offset greenhouse gas (GHG) emissions. However, amendment production and application is also associated with GHG emissions, and the net impact of these amendments remains unclear. To investigate the potential for soil amendments to reduce net GHG emissions, we developed a comprehensive, field-scale life cycle assessment (LCA) model. The LCA includes GHG (i.e., CO2, CH4, N2O) emissions of soil amendment production, application, and ecosystem response. Emissions avoided by diverting materials from landfills or manure management systems are also considered. We developed the model using field observations from grazed annual grassland in northern California (e.g., soil C; above- and belowground net primary productivity; C:N ratios; trace gas emissions from soils, manure piles, and composting), CENTURY model simulations (e.g., long-term soil C and trace gas emissions from soils under various land management strategies), and literature values (e.g., GHG emissions from transportation, inorganic fertilizer production, composting, and enteric fermentation). The LCA quantifies and contrasts the potential net GHG impacts of applying compost, manure, and commercial inorganic fertilizer to grazing lands. To estimate the LCA uncertainty, sensitivity tests were performed on the most widely ranging or highly uncertain parameters (e.g., compost materials, landfill emissions, manure management system emissions). Finally, our results are scaled-up to assess the feasibility and potential impacts of large-scale adoption of soil amendment application as a land-management strategy in California. Our base case results indicate that C sinks and emissions offsets associated with

  16. Dual-shell hollow polyaniline/sulfur-core/polyaniline composites improving the capacity and cycle performance of lithium-sulfur batteries

    NASA Astrophysics Data System (ADS)

    An, Yanling; Wei, Pan; Fan, Meiqiang; Chen, Da; Chen, Haichao; Ju, QiangJian; Tian, Guanglei; Shu, Kangying

    2016-07-01

    In this study, a dual-shell hollow polyaniline/sulfur-core/polyaniline (hPANI/S/PANI) composite was prepared by successively depositing PANI, S, and PANI on the surface of a template silicon sphere. The electrochemical properties of this composite were evaluated using a lithium plate as an anode in lithium/sulfur cells. The hPANI/S/PANI composite showed a discharge capacity of 572.2 mAh g-1 after 214 cycles at 0.1 C, and the Coulombic efficiency was above 87% in the whole charge/discharge cycle. The improved cycle property of the hPANI/S/PANI composite can be ascribed to the fine sulfur particles homogeneously deposited on the PANI surface and sprawled inside the two PANI layers during the charge/discharge cycle. This behavior stabilized the nanostructure of sulfur and enhanced its conductivity.

  17. Potential performance improvement using a reacting gas (nitrogin tetroxide) as the working fluid in a closed Brayton cycle

    NASA Technical Reports Server (NTRS)

    Stochl, R. J.

    1979-01-01

    The results of an analysis to estimate the performance that could be obtained by using a chemically reacting gas (nitrogen tetroxide) as the working fluid in a closed Brayton cycle are presented. Compared with data for helium as the working fluid, these results indicate efficiency improvements from 4 to 90 percent, depending on turbine inlet temperature, pressures, and gas residence time in heat transfer equipment.

  18. Gas composition and isotopic geochemistry of cuttings, core, and gas hydrate from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well

    USGS Publications Warehouse

    Lorenson, T.D.

    1999-01-01

    Molecular and isotopic composition of gases from the JAPEX/JNOC/GSC Mallik 2L-38 gas hydrate research well demonstrate that the in situ gases can be divided into three zones composed of mixtures of microbial and thermogenic gases. Sediments penetrated by the well are thermally immature; thus the sediments are probably not a source of thermogenic gas. Thermogenic gas likely migrated from depths below 5000 m. Higher concentrations of gas within and beneath the gas hydrate zone suggest that gas hydrate is a partial barrier to gas migration. Gas hydrate accumulations occur wholly within zone 3, below the base of permafrost. The gas in gas hydrate resembles, in part, the thermogenic gas in surrounding sediments and gas desorbed from lignite. Gas hydrate composition implies that the primary gas hydrate form is Structure I. However, Structure II stabilizing gases are more concentrated and isotopically partitioned in gas hydrate relative to the sediment hosting the gas hydrate, implying that Structure II gas hydrate may be present in small quantities.

  19. A dynamic process model of a natural gas combined cycle -- Model development with startup and shutdown simulations

    SciTech Connect

    Liese, Eric; Zitney, Stephen E.

    2013-01-01

    Research in dynamic process simulation for integrated gasification combined cycles (IGCC) with carbon capture has been ongoing at the National Energy Technology Laboratory (NETL), culminating in a full operator training simulator (OTS) and immersive training simulator (ITS) for use in both operator training and research. A derivative work of the IGCC dynamic simulator has been a modification of the combined cycle section to more closely represent a typical natural gas fired combined cycle (NGCC). This paper describes the NGCC dynamic process model and highlights some of the simulator’s current capabilities through a particular startup and shutdown scenario.

  20. Geological controls on the occurrence of gas hydrate from core, downhole log, and seismic data in the Shenhu area, South China Sea

    USGS Publications Warehouse

    Xiujuan Wang; Xiujuan Wang; Collett, Timothy S.; Lee, Myung W.; Yang, Shengxiong; Guo, Yiqun; Wu, Shiguo

    2014-01-01

    Multi-channel seismic reflection data, well logs, and recovered sediment cores have been used in this study to characterize the geologic controls on the occurrence of gas hydrate in the Shenhu area of the South China Sea. The concept of the "gas hydrate petroleum system" has allowed for the systematic analysis of the impact of gas source, geologic controls on gas migration, and the role of the host sediment in the formation and stability of gas hydrates as encountered during the 2007 Guangzhou Marine Geological Survey Gas Hydrate Expedition (GMGS-1) in the Shenhu area. Analysis of seismic and bathymetric data identified seventeen sub-linear, near-parallel submarine canyons in this area. These canyons, formed in the Miocene, migrated in a northeasterly direction, and resulted in the burial and abandonment of canyons partially filled by coarse-grained sediments. Downhole wireline log (DWL) data were acquired from eight drill sites and sediment coring was conducted at five of these sites, which revealed the presence of suitable reservoirs for the occurrence of concentrated gas hydrate accumulations. Gas hydrate-bearing sediment layers were identified from well log and core data at three sites mainly within silt and silt clay sediments. Gas hydrate was also discovered in a sand reservoir at one site as inferred from the analysis of the DWL data. Seismic anomalies attributed to the presence of gas below the base of gas hydrate stability zone, provided direct evidence for the migration of gas into the overlying gas hydrate-bearing sedimentary sections. Geochemical analyses of gas samples collected from cores confirmed that the occurrence of gas hydrate in the Shenhu area is controlled by the presence thermogenic methane gas that has migrated into the gas hydrate stability zone from a more deeply buried source.

  1. Uncertainty analysis of integrated gasification combined cycle systems based on Frame 7H versus 7F gas turbines

    SciTech Connect

    Yunhua Zhu; H. Christopher Frey

    2006-12-15

    Integrated gasification combined cycle (IGCC) technology is a promising alternative for clean generation of power and coproduction of chemicals from coal and other feedstocks. Advanced concepts for IGCC systems that incorporate state-of-the-art gas turbine systems, however, are not commercially demonstrated. Therefore, there is uncertainty regarding the future commercial-scale performance, emissions, and cost of such technologies. The Frame 7F gas turbine represents current state-of-practice, whereas the Frame 7H is the most recently introduced advanced commercial gas turbine. The objective of this study was to evaluate the risks and potential payoffs of IGCC technology based on different gas turbine combined cycle designs. Models of entrained-flow gasifier-based IGCC systems with Frame 7F (IGCC-7F) and 7H gas turbine combined cycles (IGCC-7H) were developed in ASPEN Plus. An uncertainty analysis was conducted. Gasifier carbon conversion and project cost uncertainty are identified as the most important uncertain inputs with respect to system performance and cost. The uncertainties in the difference of the efficiencies and costs for the two systems are characterized. Despite uncertainty, the IGCC-7H system is robustly preferred to the IGCC-7F system. Advances in gas turbine design will improve the performance, emissions, and cost of IGCC systems. The implications of this study for decision-making regarding technology selection, research planning, and plant operation are discussed. 38 refs., 11 figs., 5 tabs.

  2. Uncertainty analysis of integrated gasification combined cycle systems based on Frame 7H versus 7F gas turbines.

    PubMed

    Zhu, Yunhua; Frey, H Christopher

    2006-12-01

    Integrated gasification combined cycle (IGCC) technology is a promising alternative for clean generation of power and coproduction of chemicals from coal and other feedstocks. Advanced concepts for IGCC systems that incorporate state-of-the-art gas turbine systems, however, are not commercially demonstrated. Therefore, there is uncertainty regarding the future commercial-scale performance, emissions, and cost of such technologies. The Frame 7F gas turbine represents current state-of-practice, whereas the Frame 7H is the most recently introduced advanced commercial gas turbine. The objective of this study was to evaluate the risks and potential payoffs of IGCC technology based on different gas turbine combined cycle designs. Models of entrained-flow gasifier-based IGCC systems with Frame 7F (IGCC-7F) and 7H gas turbine combined cycles (IGCC-7H) were developed in ASPEN Plus. An uncertainty analysis was conducted. Gasifier carbon conversion and project cost uncertainty are identified as the most important uncertain inputs with respect to system performance and cost. The uncertainties in the difference of the efficiencies and costs for the two systems are characterized. Despite uncertainty, the IGCC-7H system is robustly preferred to the IGCC-7F system. Advances in gas turbine design will improve the performance, emissions, and cost of IGCC systems. The implications of this study for decision-making regarding technology selection, research planning, and plant operation are discussed. PMID:17195484

  3. System study of an MHD/gas turbine combined-cycle baseload power plant. HTGL report No. 134

    SciTech Connect

    Annen, K.D.

    1981-08-01

    The MHD/gas turbine combined-cycle system has been designed specifically for applications where the availability of cooling water is very limited. The base case systems which were studied consisted of an MHD plant with a gas turbine bottoming plant, and required no cooling water. The gas turbine plant uses only air as its working fluid and receives its energy input from the MHD exhaust gases by means of metal tube heat exchangers. In addition to the base case systems, vapor cycle variation systems were considered which included the addition of a vapor cycle bottoming plant to improve the thermal efficiency. These systems required a small amount of cooling water. The MHD/gas turbine systems were modeled with sufficient detail, using realistic component specifications and costs, so that the thermal and economic performance of the system could be accurately determined. Three cases of MHD/gas turbine systems were studied, with Case I being similar to an MHD/steam system so that a direct comparison of the performances could be made, with Case II being representative of a second generation MHD system, and with Case III considering oxygen enrichment for early commercial applications. The systems are nominally 800 MW/sub e/ to 1000 MW/sub e/ in size. The results show that the MHD/gas turbine system has very good thermal and economic performances while requiring either little or no cooling water. Compared to the MHD/steam system which has a cooling tower heat load of 720 MW, the Base Case I MHD/gas turbine system has a heat rate which is 13% higher and a cost of electricity which is only 7% higher while requiring no cooling water. Case II results show that an improved performance can be expected from second generation MHD/gas turbine systems. Case III results show that an oxygen enriched MHD/gas turbine system may be attractive for early commercial applications in dry regions of the country.

  4. Highly cross-linked Cu/a-Si core-shell nanowires for ultra-long cycle life and high rate lithium batteries

    NASA Astrophysics Data System (ADS)

    Wang, Hongxiang; Song, Hucheng; Lin, Zixia; Jiang, Xiaofan; Zhang, Xiaowei; Yu, Linwei; Xu, Jun; Pan, Lijia; Wang, Junzhuan; Zheng, Mingbo; Shi, Yi; Chen, Kunji

    2016-01-01

    Seeking long cycle lifetime and high rate performance are still challenging aspects to promote the application of silicon-loaded lithium ion batteries (LIBs), where optimal structural and compositional design are critical to maximize a synergistic effect in composite core-shell nanowire anode structures. We here propose and demonstrate a high quality conformal coating of an amorphous Si (a-Si) thin film over a matrix of highly cross-linked CuO nanowires (NWs). The conformal a-Si coating can serve as both a high capacity storage medium and a high quality binder that joins crossing CuO NWs into a continuous network. And the CuO NWs can be reduced into highly conductive Cu cores in low temperature H2 annealing. In this way, we have demonstrated an excellent cycling stability that lasts more than 700 (or 1000) charge/discharge cycles at a current density of 3.6 A g-1 (or 1 A g-1), with a high capacity retention rate of 80%. Remarkably, these Cu/a-Si core-shell anode structures can survive an extremely high charging current density of 64 A g-1 for 25 runs, and then recover 75% initial capacity when returning to 1 A g-1. We also present the first and straightforward experimental proof that these robust highly-cross-linked core-shell networks can preserve the structural integrity even after 1000 runs of cycling. All these results indicate a new and convenient strategy towards a high performance Si-loaded battery application.Seeking long cycle lifetime and high rate performance are still challenging aspects to promote the application of silicon-loaded lithium ion batteries (LIBs), where optimal structural and compositional design are critical to maximize a synergistic effect in composite core-shell nanowire anode structures. We here propose and demonstrate a high quality conformal coating of an amorphous Si (a-Si) thin film over a matrix of highly cross-linked CuO nanowires (NWs). The conformal a-Si coating can serve as both a high capacity storage medium and a high

  5. NONWATER QUALITY IMPACTS OF CLOSED-CYCLE COOLING SYSTEMS AND THE INTERACTION OF STACK GAS AND COOLING TOWER PLUMES

    EPA Science Inventory

    The report gives results of a literature survey of the nonwater quality impacts of closed-cycle cooling systems. Following discussions of cooling tower and stack gas plumes, interactions of these plumes are considered. For cooling tower plumes, plume types, behavior, salt drift g...

  6. 40 CFR 86.1309-90 - Exhaust gas sampling system; Otto-cycle and non-petroleum-fueled engines.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Exhaust gas sampling system; Otto-cycle and non-petroleum-fueled engines. 86.1309-90 Section 86.1309-90 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES...

  7. The high-efficient regenerative cycle of a gas turbine unit with recirculation of combustion products at high pressure

    NASA Astrophysics Data System (ADS)

    Khodus, V. V.

    2010-02-01

    The circuit of a stationary gas turbine unit is proposed using which it is possible to obtain the thermodynamic advantages of a regenerative cycle with a small compression ratio as a result of setting up a partially closed loop (with a small compression ratio) and high absolute values of pressure at the inlet to and outlet from the circulation loop compressor.

  8. Highly cross-linked Cu/a-Si core-shell nanowires for ultra-long cycle life and high rate lithium batteries.

    PubMed

    Wang, Hongxiang; Song, Hucheng; Lin, Zixia; Jiang, Xiaofan; Zhang, Xiaowei; Yu, Linwei; Xu, Jun; Pan, Lijia; Wang, Junzhuan; Zheng, Mingbo; Shi, Yi; Chen, Kunji

    2016-02-01

    Seeking long cycle lifetime and high rate performance are still challenging aspects to promote the application of silicon-loaded lithium ion batteries (LIBs), where optimal structural and compositional design are critical to maximize a synergistic effect in composite core-shell nanowire anode structures. We here propose and demonstrate a high quality conformal coating of an amorphous Si (a-Si) thin film over a matrix of highly cross-linked CuO nanowires (NWs). The conformal a-Si coating can serve as both a high capacity storage medium and a high quality binder that joins crossing CuO NWs into a continuous network. And the CuO NWs can be reduced into highly conductive Cu cores in low temperature H2 annealing. In this way, we have demonstrated an excellent cycling stability that lasts more than 700 (or 1000) charge/discharge cycles at a current density of 3.6 A g(-1) (or 1 A g(-1)), with a high capacity retention rate of 80%. Remarkably, these Cu/a-Si core-shell anode structures can survive an extremely high charging current density of 64 A g(-1) for 25 runs, and then recover 75% initial capacity when returning to 1 A g(-1). We also present the first and straightforward experimental proof that these robust highly-cross-linked core-shell networks can preserve the structural integrity even after 1000 runs of cycling. All these results indicate a new and convenient strategy towards a high performance Si-loaded battery application. PMID:26572901

  9. Integral manifolding structure for fuel cell core having parallel gas flow

    DOEpatents

    Herceg, J.E.

    1983-10-12

    Disclosed herein are manifolding means for directing the fuel and oxidant gases to parallel flow passageways in a fuel cell core. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte and interconnect wall consists respectively of anode and cathode materials layered on the opposite sides of electrolyte material, or on the opposite sides of interconnect material. A core wall projects beyond the open ends of the defined core passageways and is disposed approximately midway between and parallel to the adjacent overlaying and underlying interconnect walls to define manifold chambers therebetween on opposite sides of the wall. Each electrolyte wall defining the flow passageways is shaped to blend into and be connected to this wall in order to redirect the corresponding fuel and oxidant passageways to the respective manifold chambers either above or below this intermediate wall. Inlet and outlet connections are made to these separate manifold chambers respectively, for carrying the fuel and oxidant gases to the core, and for carrying their reaction products away from the core.

  10. Integral manifolding structure for fuel cell core having parallel gas flow

    DOEpatents

    Herceg, Joseph E.

    1984-01-01

    Disclosed herein are manifolding means for directing the fuel and oxidant gases to parallel flow passageways in a fuel cell core. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte and interconnect wall consists respectively of anode and cathode materials layered on the opposite sides of electrolyte material, or on the opposite sides of interconnect material. A core wall projects beyond the open ends of the defined core passageways and is disposed approximately midway between and parallel to the adjacent overlaying and underlying interconnect walls to define manifold chambers therebetween on opposite sides of the wall. Each electrolyte wall defining the flow passageways is shaped to blend into and be connected to this wall in order to redirect the corresponding fuel and oxidant passageways to the respective manifold chambers either above or below this intermediate wall. Inlet and outlet connections are made to these separate manifold chambers respectively, for carrying the fuel and oxidant gases to the core, and for carrying their reaction products away from the core.

  11. Synthesis and morphology of iron-iron oxide core-shell nanoparticles produced by high pressure gas condensation.

    PubMed

    Xing, Lijuan; Ten Brink, Gert H; Chen, Bin; Schmidt, Franz P; Haberfehlner, Georg; Hofer, Ferdinand; Kooi, Bart J; Palasantzas, George

    2016-05-27

    Core-shell structured Fe nanoparticles (NPs) produced by high pressure magnetron sputtering gas condensation were studied using transmission electron microscopy (TEM) techniques, electron diffraction, electron energy-loss spectroscopy (EELS), tomographic reconstruction, and Wulff shape construction analysis. The core-shell structure, which is composed of an Fe core surrounded by a maghemite (γ-Fe2O3) and/or magnetite (Fe3O4) shell, was confirmed by fast Fourier transform (FFT) analysis combined with EELS. It was found that the particle size and shape strongly depend on the gas environment. Moreover, extensive analysis showed that NPs with a size between 10-20 nm possess a truncated cubic morphology, which is confined by the 6 {100} planes that are truncated by the 12 {110} planes at different degrees. For NPs larger than 20 nm, the rhombic dodecahedron defined by the 12 {110} planes is the predominant crystal shape, while truncated rhombic dodecahedrons, as well as non-truncated and truncated cubic NPs, were also observed. The NPs without truncation showed a characteristic inward relaxation indicating that besides thermodynamics kinetics also plays a crucial role during particle growth. PMID:27089553

  12. Energy analyses and greenhouse gas emissions assessment for saffron production cycle.

    PubMed

    Bakhtiari, Amir Abbas; Hematian, Amir; Sharifi, Azin

    2015-10-01

    Population growth and world climate changes are putting high pressure on agri-food production systems. Exacerbating use of energy sources and expanding the environmental damaging symptoms are the results of these difficult situations. This study was conducted to determine the energy balance for saffron production cycle and investigate the corresponding greenhouse gas (GHG) emissions in Iran. Saffron (Crocus sativus L.) is one of the main spice that historically cultivated in Iran. Data were obtained from 127 randomly selected saffron growers using a face to face questionnaire technique. The results revealed that in 5 years of saffron production cycle, the overall input and output energy use were to be 163,912.09 and 184,868.28 MJ ha(-1), respectively. The highest-level of energy consumption belongs to seeds (23.7 %) followed by chemical fertilizers (23.4 %). Energy use efficiency, specific energy, net energy, and energy productivity of saffron production were 1.1, 13.4 MJ kg(-1), 20,956.2 MJ ha(-1), and 0.1 kg MJ(-1), respectively. The result shows that the cultivation of saffron emits 2325.5 kg CO2 eq. ha(-1) greenhouse gas, in which around 46.5 % belonged to electricity followed by chemical fertilizers. In addition the Cobb-Douglas production function was applied into EViews 7 software to define the functional relationship. The results of econometric model estimation showed that the impact of human labor, electricity, and water for irrigation on stigma, human labor, electricity, and seed on corm and also human labor and farmyard manure (FYM) on flower and leaf yield were found to be statistically significant. Sensitivity analysis results of the energy inputs demonstrated that the marginal physical productivity (MPP) worth of electricity energy was the highest for saffron stigma and corm, although saffron flower and leaf had more sensitivity on chemicals energy inputs. Moreover, MPP values of renewable and indirect energies were higher than non-renewable and

  13. Noble gas-derived insights into carbon cycling into the deep biosphere

    NASA Astrophysics Data System (ADS)

    Sherwood Lollar, B.; Ballentine, C. J.; Lippmann-Pipke, J.; Slater, G. F.; Onstott, T. C.; Lin, L.; Moran, J.; Tille, S.; Moser, D. P.; Lacrampe-Couloume, G.

    2009-12-01

    Discovery of chemoautotrophic microbial communities at the mid-ocean ridges launched the exploration of the "deep hot biosphere". Recent advances have demonstrated however that chemoautotrophic communities are not restricted to high temperature hydrothermal settings. The discovery that the terrestrial subsurface too hosts chemoautotrophic ecosystems sustained by the products of water-rock reactions - albeit at lower temperatures and slower rates of reaction - has expanded our view of the extent of the planet that is habitable. Compelling questions remain. What are the ultimate limits to life in the Earth's deep subsurface? What are the underlying controls on microbial metabolic activity and biodiversity? The answers to these questions may provide insight into the evolutionary relationship of deep terrestrial microbial communities to marine sediment-hosted and vent-hosted communities, into the origin of life on Earth, and the potential for life on other planets and moons. At more than 2 km below surface, fracture waters accessed via mines in the tectonically quiescent Precambrian Shields of Canada and South Africa are dominated by radiogenic noble gases and crustal-derived carbon sources. Key uncertainties concerning the deep terrestrial biosphere in these settings include the rates and mechanisms of carbon cycling far from the photosphere, and hence the scale and significance of this remote and exotic reservoir of the global biogeochemical cycle. While carbon geochemistry and stable isotopes, as well as molecular microbiology, have facilitated major advances in identifying the geochemical and microbiological processes involved, this presentation will highlight how coupling these techniques with noble gases constrains the timescales for the deep carbon cycle. In particular, the coupling of noble gas tracers with carbon geochemistry provides the key to recognizing that hydrogeologically isolated fracture networks of geochemically distinct groundwaters exert a major

  14. Uncertainties in Life Cycle Greenhouse Gas Emissions from Advanced Biomass Feedstock Logistics Supply Chains in Kansas

    SciTech Connect

    Cafferty, Kara G.; Searcy, Erin M.; Nguyen, Long; Spatari, Sabrina

    2014-11-01

    To meet Energy Independence and Security Act (EISA) cellulosic biofuel mandates, the United States will require an annual domestic supply of about 242 million Mg of biomass by 2022. To improve the feedstock logistics of lignocellulosic biofuels and access available biomass resources from areas with varying yields, commodity systems have been proposed and designed to deliver on-spec biomass feedstocks at preprocessing “depots”, which densify and stabilize the biomass prior to long-distance transport and delivery to centralized biorefineries. The harvesting, preprocessing, and logistics (HPL) of biomass commodity supply chains thus could introduce spatially variable environmental impacts into the biofuel life cycle due to needing to harvest, move, and preprocess biomass from multiple distances that have variable spatial density. This study examines the uncertainty in greenhouse gas (GHG) emissions of corn stover logisticsHPL within a bio-ethanol supply chain in the state of Kansas, where sustainable biomass supply varies spatially. Two scenarios were evaluated each having a different number of depots of varying capacity and location within Kansas relative to a central commodity-receiving biorefinery to test GHG emissions uncertainty. Monte Carlo simulation was used to estimate the spatial uncertainty in the HPL gate-to-gate sequence. The results show that the transport of densified biomass introduces the highest variability and contribution to the carbon footprint of the logistics HPL supply chain (0.2-13 g CO2e/MJ). Moreover, depending upon the biomass availability and its spatial density and surrounding transportation infrastructure (road and rail), logistics HPL processes can increase the variability in life cycle environmental impacts for lignocellulosic biofuels. Within Kansas, life cycle GHG emissions could range from 24 to 41 g CO2e/MJ depending upon the location, size and number of preprocessing depots constructed. However, this

  15. Comparison of life cycle greenhouse gases from natural gas pathways for medium and heavy-duty vehicles.

    PubMed

    Tong, Fan; Jaramillo, Paulina; Azevedo, Inês M L

    2015-06-16

    The low-cost and abundant supply of shale gas in the United States has increased the interest in using natural gas for transportation. We compare the life cycle greenhouse gas (GHG) emissions from different natural gas pathways for medium and heavy-duty vehicles (MHDVs). For Class 8 tractor-trailers and refuse trucks, none of the natural gas pathways provide emissions reductions per unit of freight-distance moved compared to diesel trucks. When compared to the petroleum-based fuels currently used in these vehicles, CNG and centrally produced LNG increase emissions by 0-3% and 2-13%, respectively, for Class 8 trucks. Battery electric vehicles (BEVs) powered with natural gas-produced electricity are the only fuel-technology combination that achieves emission reductions for Class 8 transit buses (31% reduction compared to the petroleum-fueled vehicles). For non-Class 8 trucks (pick-up trucks, parcel delivery trucks, and box trucks), BEVs reduce emissions significantly (31-40%) compared to their diesel or gasoline counterparts. CNG and propane achieve relatively smaller emissions reductions (0-6% and 19%, respectively, compared to the petroleum-based fuels), while other natural gas pathways increase emissions for non-Class 8 MHDVs. While using natural gas to fuel electric vehicles could achieve large emission reductions for medium-duty trucks, the results suggest there are no great opportunities to achieve large emission reductions for Class 8 trucks through natural gas pathways with current technologies. There are strategies to reduce the carbon footprint of using natural gas for MHDVs, ranging from increasing vehicle fuel efficiency, reducing life cycle methane leakage rate, to achieving the same payloads and cargo volumes as conventional diesel trucks. PMID:25938939

  16. Total fuel-cycle analysis of heavy-duty vehicles using biofuels and natural gas-based alternative fuels.

    PubMed

    Meyer, Patrick E; Green, Erin H; Corbett, James J; Mas, Carl; Winebrake, James J

    2011-03-01

    Heavy-duty vehicles (HDVs) present a growing energy and environmental concern worldwide. These vehicles rely almost entirely on diesel fuel for propulsion and create problems associated with local pollution, climate change, and energy security. Given these problems and the expected global expansion of HDVs in transportation sectors, industry and governments are pursuing biofuels and natural gas as potential alternative fuels for HDVs. Using recent lifecycle datasets, this paper evaluates the energy and emissions impacts of these fuels in the HDV sector by conducting a total fuel-cycle (TFC) analysis for Class 8 HDVs for six fuel pathways: (1) petroleum to ultra low sulfur diesel; (2) petroleum and soyoil to biodiesel (methyl soy ester); (3) petroleum, ethanol, and oxygenate to e-diesel; (4) petroleum and natural gas to Fischer-Tropsch diesel; (5) natural gas to compressed natural gas; and (6) natural gas to liquefied natural gas. TFC emissions are evaluated for three greenhouse gases (GHGs) (carbon dioxide, nitrous oxide, and methane) and five other pollutants (volatile organic compounds, carbon monoxide, nitrogen oxides, particulate matter, and sulfur oxides), along with estimates of total energy and petroleum consumption associated with each of the six fuel pathways. Results show definite advantages with biodiesel and compressed natural gas for most pollutants, negligible benefits for e-diesel, and increased GHG emissions for liquefied natural gas and Fischer-Tropsch diesel (from natural gas). PMID:21416755

  17. Design of Gas-phase Synthesis of Core-Shell Particles by Computational Fluid - Aerosol Dynamics.

    PubMed

    Buesser, B; Pratsinis, S E

    2011-11-01

    Core-shell particles preserve the bulk properties (e.g. magnetic, optical) of the core while its surface is modified by a shell material. Continuous aerosol coating of core TiO2 nanoparticles with nanothin silicon dioxide shells by jet injection of hexamethyldisiloxane precursor vapor downstream of titania particle formation is elucidated by combining computational fluid and aerosol dynamics. The effect of inlet coating vapor concentration and mixing intensity on product shell thickness distribution is presented. Rapid mixing of the core aerosol with the shell precursor vapor facilitates efficient synthesis of hermetically coated core-shell nanoparticles. The predicted extent of hermetic coating shells is compared to the measured photocatalytic oxidation of isopropanol by such particles as hermetic SiO2 shells prevent the photocatalytic activity of titania. Finally the performance of a simpler, plug-flow coating model is assessed by comparisons to the present detailed CFD model in terms of coating efficiency and silica average shell thickness and texture. PMID:23729817

  18. Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment

    PubMed Central

    Balakrishnan, Madhesan; Sacia, Eric R.; Sreekumar, Sanil; Gunbas, Gorkem; Gokhale, Amit A.; Scown, Corinne D.; Toste, F. Dean; Bell, Alexis T.

    2015-01-01

    Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailored for aviation fuels as well as lubricants by changing the production strategy. We also demonstrate that a sugarcane biorefinery could use natural synergies between various routes to produce a mixture of lubricant base oils and jet fuels that achieve net life-cycle greenhouse gas savings of up to 80%. PMID:26056307

  19. Cycle Analysis of Micro Gas Turbine-Molten Carbonate Fuel Cell Hybrid System

    NASA Astrophysics Data System (ADS)

    Kimijima, Shinji; Kasagi, Nobuhide

    A hybrid system based on a micro gas turbine (µGT) and a high-temperature fuel cell, i.e., molten carbonate fuel cell (MCFC) or solid oxide fuel cell (SOFC), is expected to achieve a much higher efficiency than conventional distributed power generation systems. In this study, a cycle analysis method and the performance evaluation of a µGT-MCFC hybrid system, of which the power output is 30kW, are investigated to clarify its feasibility. We developed a general design strategy in which a low fuel input to a combustor and higher MCFC operating temperature result in a high power generation efficiency. A high recuperator temperature effectiveness and a moderate steam-carbon ratio are the requirements for obtaining a high material strength in a turbine. In addition, by employing a combustor for complete oxidation of MCFC effluents without additional fuel input, i.e., a catalytic combustor, the power generation efficiency of a µGT-MCFC is achieved at over 60%(LHV).

  20. Material considerations for HRSGs in gas turbine combined cycle plants. Final report

    SciTech Connect

    Bourgeois, H.S.

    1996-08-01

    The primary objectives of this project are to investigate and identify the limitations of current heat recovery steam generator (HRSG) materials, identify potential materials that could be used in future high temperature HRSGs, and develop a research and development plan to address the deficiencies and the future requirements. The project team developed a comprehensive survey which was forwarded to many HRSG manufacturers worldwide. The manufacturers were questioned about cycle experience, failure experience, design practices, materials, research and development, and future designs. The team assembled the responses and other in-house data to identify the key problem areas, probably future operating parameters, and possible material issues. The draft report was circulated to the manufacturers surveyed for comments before the final report was issued. The predominant current problem area for HRSGs relates to insulation; however, it is anticipated that in future designs, tube failures and welds will become most important. Poor water chemistry has already resulted in numerous failure mechanisms. By 2005, HSRGs are expected to operated with the following average conditions: unfired gas temperatures of 1125 F, steam temperatures of 950 F, steam pressures of 1500 psi, and exhaust temperatures of 170 F.

  1. Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment.

    PubMed

    Balakrishnan, Madhesan; Sacia, Eric R; Sreekumar, Sanil; Gunbas, Gorkem; Gokhale, Amit A; Scown, Corinne D; Toste, F Dean; Bell, Alexis T

    2015-06-23

    Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailored for aviation fuels as well as lubricants by changing the production strategy. We also demonstrate that a sugarcane biorefinery could use natural synergies between various routes to produce a mixture of lubricant base oils and jet fuels that achieve net life-cycle greenhouse gas savings of up to 80%. PMID:26056307

  2. In-N-Out: The Gas Cycle from Dwarfs to Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Christensen, Charlotte R.; Davé, Romeel; Governato, Fabio; Pontzen, Andrew; Brooks, Alyson; Munshi, Ferah; Quinn, Thomas; Wadsley, James

    2016-06-01

    We examine the scalings of galactic outflows with halo mass across a suite of 20 high-resolution cosmological zoom galaxy simulations covering halo masses in the range {10}9.5{--}{10}12 {M}ȯ . These simulations self-consistently generate outflows from the available supernova energy in a manner that successfully reproduces key galaxy observables, including the stellar mass–halo mass, Tully–Fisher, and mass–metallicity relations. We quantify the importance of ejective feedback to setting the stellar mass relative to the efficiency of gas accretion and star formation. Ejective feedback is increasingly important as galaxy mass decreases; we find an effective mass loading factor that scales as {v}{{circ}}-2.2, with an amplitude and shape that are invariant with redshift. These scalings are consistent with analytic models for energy-driven wind, based solely on the halo potential. Recycling is common: about half of the outflow mass across all galaxy masses is later reaccreted. The recycling timescale is typically ∼1 Gyr, virtually independent of halo mass. Recycled material is reaccreted farther out in the disk and with typically ∼2–3 times more angular momentum. These results elucidate and quantify how the baryon cycle plausibly regulates star formation and alters the angular momentum distribution of disk material across the halo mass range where most cosmic star formation occurs.

  3. Quantifying the uncertainties in life cycle greenhouse gas emissions for UK wheat ethanol

    NASA Astrophysics Data System (ADS)

    Yan, Xiaoyu; Boies, Adam M.

    2013-03-01

    Biofuels are increasingly promoted worldwide as a means for reducing greenhouse gas (GHG) emissions from transport. However, current regulatory frameworks and most academic life cycle analyses adopt a deterministic approach in determining the GHG intensities of biofuels and thus ignore the inherent risk associated with biofuel production. This study aims to develop a transparent stochastic method for evaluating UK biofuels that determines both the magnitude and uncertainty of GHG intensity on the basis of current industry practices. Using wheat ethanol as a case study, we show that the GHG intensity could span a range of 40-110 gCO2e MJ-1 when land use change (LUC) emissions and various sources of uncertainty are taken into account, as compared with a regulatory default value of 44 gCO2e MJ-1. This suggests that the current deterministic regulatory framework underestimates wheat ethanol GHG intensity and thus may not be effective in evaluating transport fuels. Uncertainties in determining the GHG intensity of UK wheat ethanol include limitations of available data at a localized scale, and significant scientific uncertainty of parameters such as soil N2O and LUC emissions. Biofuel polices should be robust enough to incorporate the currently irreducible uncertainties and flexible enough to be readily revised when better science is available.

  4. Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment

    DOE PAGESBeta

    Balakrishnan, Madhesan; Sacia, Eric R.; Sreekumar, Sanil; Gunbas, Gorkem; Gokhale, Amit A.; Scown, Corinne D.; Toste, F. Dean; Bell, Alexis T.

    2015-06-08

    Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a methodmore » for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailored for aviation fuels as well as lubricants by changing the production strategy. We demonstrate that a sugarcane biorefinery could use natural synergies between various routes to produce a mixture of lubricant base oils and jet fuels that achieve net life-cycle greenhouse gas savings of up to 80%.« less

  5. Novel pathways for fuels and lubricants from biomass optimized using life-cycle greenhouse gas assessment

    SciTech Connect

    Balakrishnan, Madhesan; Sacia, Eric R.; Sreekumar, Sanil; Gunbas, Gorkem; Gokhale, Amit A.; Scown, Corinne D.; Toste, F. Dean; Bell, Alexis T.

    2015-06-08

    Decarbonizing the transportation sector is critical to achieving global climate change mitigation. Although biofuels will play an important role in conventional gasoline and diesel applications, bioderived solutions are particularly important in jet fuels and lubricants, for which no other viable renewable alternatives exist. Producing compounds for jet fuel and lubricant base oil applications often requires upgrading fermentation products, such as alcohols and ketones, to reach the appropriate molecular-weight range. Ketones possess both electrophilic and nucleophilic functionality, which allows them to be used as building blocks similar to alkenes and aromatics in a petroleum refining complex. Here, we develop a method for selectively upgrading biomass-derived alkyl methyl ketones with >95% yields into trimer condensates, which can then be hydrodeoxygenated in near-quantitative yields to give a new class of cycloalkane compounds. The basic chemistry developed here can be tailored for aviation fuels as well as lubricants by changing the production strategy. We demonstrate that a sugarcane biorefinery could use natural synergies between various routes to produce a mixture of lubricant base oils and jet fuels that achieve net life-cycle greenhouse gas savings of up to 80%.

  6. In-N-Out: The Gas Cycle from Dwarfs to Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Christensen, Charlotte R.; Davé, Romeel; Governato, Fabio; Pontzen, Andrew; Brooks, Alyson; Munshi, Ferah; Quinn, Thomas; Wadsley, James

    2016-06-01

    We examine the scalings of galactic outflows with halo mass across a suite of 20 high-resolution cosmological zoom galaxy simulations covering halo masses in the range {10}9.5{--}{10}12 {M}ȯ . These simulations self-consistently generate outflows from the available supernova energy in a manner that successfully reproduces key galaxy observables, including the stellar mass–halo mass, Tully–Fisher, and mass–metallicity relations. We quantify the importance of ejective feedback to setting the stellar mass relative to the efficiency of gas accretion and star formation. Ejective feedback is increasingly important as galaxy mass decreases; we find an effective mass loading factor that scales as {v}{{circ}}-2.2, with an amplitude and shape that are invariant with redshift. These scalings are consistent with analytic models for energy-driven wind, based solely on the halo potential. Recycling is common: about half of the outflow mass across all galaxy masses is later reaccreted. The recycling timescale is typically ˜1 Gyr, virtually independent of halo mass. Recycled material is reaccreted farther out in the disk and with typically ˜2–3 times more angular momentum. These results elucidate and quantify how the baryon cycle plausibly regulates star formation and alters the angular momentum distribution of disk material across the halo mass range where most cosmic star formation occurs.

  7. HYBRID SULFUR CYCLE FLOWSHEETS FOR HYDROGEN PRODUCTION USING HIGH-TEMPERATURE GAS-COOLED REACTORS

    SciTech Connect

    Gorensek, M.

    2011-07-06

    Two hybrid sulfur (HyS) cycle process flowsheets intended for use with high-temperature gas-cooled reactors (HTGRs) are presented. The flowsheets were developed for the Next Generation Nuclear Plant (NGNP) program, and couple a proton exchange membrane (PEM) electrolyzer for the SO2-depolarized electrolysis step with a silicon carbide bayonet reactor for the high-temperature decomposition step. One presumes an HTGR reactor outlet temperature (ROT) of 950 C, the other 750 C. Performance was improved (over earlier flowsheets) by assuming that use of a more acid-tolerant PEM, like acid-doped poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI), instead of Nafion{reg_sign}, would allow higher anolyte acid concentrations. Lower ROT was accommodated by adding a direct contact exchange/quench column upstream from the bayonet reactor and dropping the decomposition pressure. Aspen Plus was used to develop material and energy balances. A net thermal efficiency of 44.0% to 47.6%, higher heating value basis is projected for the 950 C case, dropping to 39.9% for the 750 C case.

  8. Neutron flux measurements in the side-core region of Hunterston B advanced gas-cooled reactor

    SciTech Connect

    Allen, D.A.; Shaw, S.E.; Huggon, A.P.; Steadman, R.J.; Thornton, D.A.; Whiley, G.S.

    2011-07-01

    The core restraints of advanced gas-cooled reactors are important structural components that are required to maintain the geometric integrity of the cores. A review of neutron dosimetry for the sister stations Hunterston B and Hinkley Point B identified that earlier conservative assessments predicted high thermal neutron dose rates to key components of the restraint structure (the restraint rod welds), with the implication that some of them may be predicted to fail during a seismic event. A revised assessment was therefore undertaken [Thornton, D. A., Allen, D. A., Tyrrell, R. J., Meese, T. C., Huggon, A.P., Whiley, G. S., and Mossop, J. R., 'A Dosimetry Assessment for the Core Restraint of an Advanced Gas Cooled Reactor,' Proceedings of the 13. International Symposium on Reactor Dosimetry (ISRD-13, May 2008), World Scientific, River Edge, NJ, 2009, W. Voorbraak, L. Debarberis, and P. D'hondt, Eds., pp. 679-687] using a detailed 3D model and a Monte Carlo radiation transport program, MCBEND. This reassessment resulted in more realistic fast and thermal neutron dose recommendations, the latter in particular being much lower than had been thought previously. It is now desirable to improve confidence in these predictions by providing direct validation of the MCBEND model through the use of neutron flux measurements. This paper describes the programme of work being undertaken to deploy two neutron flux measurement 'stringers' within the side-core region of one of the Hunterston B reactors for the purpose of validating the MCBEND model. The design of the stringers and the determination of the preferred deployment locations have been informed by the use of detailed MCBEND flux calculations. These computational studies represent a rare opportunity to design a flux measurement beforehand, with the clear intention of minimising the anticipated uncertainties and obtaining measurements that are known to be representative of the neutron fields to which the vulnerable steel

  9. Perforated hollow-core optical waveguides for on-chip atomic spectroscopy and gas sensing

    NASA Astrophysics Data System (ADS)

    Giraud-Carrier, M.; Hill, C.; Decker, T.; Black, J. A.; Schmidt, H.; Hawkins, A.

    2016-03-01

    A hollow-core waveguide structure for on-chip atomic spectroscopy is presented. The devices are based on Anti-Resonant Reflecting Optical Waveguides and may be used for a wide variety of applications which rely on the interaction of light with gases and vapors. The designs presented here feature short delivery paths of the atomic vapor into the hollow waveguide. They also have excellent environmental stability by incorporating buried solid-core waveguides to deliver light to the hollow cores. Completed chips were packaged with an Rb source and the F = 3 ≥ F' = 2, 3, 4 transitions of the D2 line in 85Rb were monitored for optical absorption. Maximum absorption peak depths of 9% were measured.

  10. Reducing Uncertainty in Life Cycle CH4 Emissions from Natural Gas using Atmospheric Inversions

    NASA Astrophysics Data System (ADS)

    Schwietzke, S.; Griffin, W.; Matthews, H.; Bruhwiler, L.

    2013-12-01

    Rising interest in natural gas (NG) as a potentially cleaner alternative to coal and successful tapping of unconventional resources in North America, particularly shale gas, have led to numerous life cycle assessment (LCA) studies revisiting NG leakage rates, i.e., the fraction of produced NG, mostly methane, emitted to the atmosphere, intentionally or unintentionally. Accurately quantifying leakage rates of the full NG life cycle - extraction, processing, transport, and distribution - is challenging due to the size and complexity of the NG industry. Recent U.S. LCA estimates suggest that current NG leakage could be as high as 8% and 6%, from shale and conventional NG, respectively, compared to less than 2% in the latest EPA GHG emission inventory. Reducing uncertainty in the NG leakage rate is important for assessing potential climate benefits of NG over coal, and for understanding the global CH4 budget. The objective of this research is to analyze which ranges of the global average NG leakage rate are reasonable given existing atmospheric observations. We establish detailed prior global CH4 and C2H6 emission inventory scenarios for NG, oil, and coal using emissions data from the LCA literature including uncertainty estimates. Global CH4 and C2H6 inverse box-modeling is used to test the above hypotheses of various global NG leakage rates over the period 1984-2011. Forward simulations with NOAA's CarbonTracker-CH4 (CT-CH4) model provide additional spatial and seasonal information about CH4 atmospheric distribution. Box model inversion results indicate worst-case scenarios of current (2010) global average NG leakage rates of 7% (128 Tg CH4/yr) and 5% (92 Tg CH4/yr) based on CH4 isotope and C2H6 observations, respectively, as well as available raw gas composition data. Worst-case assumptions include upper bound estimates of the global CH4 and C2H6 budget, lower bound literature estimates of all CH4 and C2H6 sources other than NG simultaneously, and absence of a

  11. Accelerator-driven subcritical fission in molten salt core: Closing the nuclear fuel cycle for green nuclear energy

    NASA Astrophysics Data System (ADS)

    McIntyre, Peter; Assadi, Saeed; Badgley, Karie; Baker, William; Comeaux, Justin; Gerity, James; Kellams, Joshua; McInturff, Al; Pogue, Nathaniel; Phongikaroon, Supathorn; Sattarov, Akhdiyor; Simpson, Michael; Sooby, Elizabeth; Tsvetkov, Pavel

    2013-04-01

    A technology for accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a basis for the destruction of the transuranics in used nuclear fuel. The molten salt fuel is a eutectic mixture of NaCl and the chlorides of the transuranics and fission products. The core is driven by proton beams from a strong-focusing cyclotron stack. This approach uniquely provides an intrinsically safe means to drive a core fueled only with transuranics, thereby eliminating competing breeding terms.

  12. Accelerator-driven subcritical fission in molten salt core: Closing the nuclear fuel cycle for green nuclear energy

    SciTech Connect

    McIntyre, Peter; Assadi, Saeed; Badgley, Karie; Baker, William; Comeaux, Justin; Gerity, James; Kellams, Joshua; McInturff, Al; Pogue, Nathaniel; Sattarov, Akhdiyor; Sooby, Elizabeth; Tsvetkov, Pavel; Phongikaroon, Supathorn; Simpson, Michael

    2013-04-19

    A technology for accelerator-driven subcritical fission in a molten salt core (ADSMS) is being developed as a basis for the destruction of the transuranics in used nuclear fuel. The molten salt fuel is a eutectic mixture of NaCl and the chlorides of the transuranics and fission products. The core is driven by proton beams from a strong-focusing cyclotron stack. This approach uniquely provides an intrinsically safe means to drive a core fueled only with transuranics, thereby eliminating competing breeding terms.

  13. Effect of pressure and shielding gas on the microstructure of hyperbaric metal cored GMAW welds down to 111 bar

    SciTech Connect

    Jorge, J.C.F.; Santos, V.R. dos

    1995-12-31

    The microstructural evolution of hyperbaric C-Mn weld metals was studied by means of bead-on-plate welds deposit with GMAW process using a commercial metal cored wire. The welding was carried out in the flat position in the range of 51 bar to 111 bar with He+ CO{sub 2} as shielding gas, which CO{sub 2} content varied from 0.1% to 0.8 %. The microstructures were quantitatively analyzed by optical microscopy to evaluate the amount of constituents according to the IIW/IIS terminology. The results showed that all weld metals presented great amounts of acicular ferrite and a stronger influence of pressure on microstructure compared to the influence of the shielding gas.

  14. Ionized gas kinematics at high resolution. IV. Star formation and a rotating core in the Medusa (NGC 4194)

    SciTech Connect

    Beck, Sara C.; Lacy, John; Turner, Jean; Greathouse, Thomas; Neff, Susan

    2014-05-20

    NGC 4194 is a post-merger starburst known as The Medusa for its striking tidal features. We present here a detailed study of the structure and kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data include radio continuum maps with resolution up to 0.''18 (35 pc) and a 12.8 μm [Ne II] data cube with spectral resolution ∼4 km s{sup –1}: the first high-resolution, extinction-free observations of this remarkable object. The ionized gas has the kinematic signature of a core in solid-body rotation. The starburst has formed a complex of bright compact H II regions, probably excited by deeply embedded super star clusters, but none of these sources is a convincing candidate for a Galactic nucleus. The nuclei of the merger partners that created the Medusa have not yet been identified.

  15. Ionized Gas Kinematics at High Resolution. IV. Star Formation and a Rotating Core in the Medusa (NGC 4194)

    NASA Technical Reports Server (NTRS)

    Beck, Sara C.; Lacy, John; Neff, Susan Gale; Turner, Jean; Greathouse, Thomas; Neff, Susan

    2014-01-01

    NGC 4194 is a post-merger starburst known as The Medusa for its striking tidal features.We present here a detailed study of the structure and kinematics of ionized gas in the central 0.65 kpc of the Medusa. The data include radio continuum maps with resolution up to 0".18 (35 pc) and a 12.8 micron [Ne II] data cube with spectral resolution approx. 4 km/s: the first high-resolution, extinction-free observations of this remarkable object. The ionized gas has the kinematic signature of a core in solid-body rotation. The starburst has formed a complex of bright compact H II regions, probably excited by deeply embedded super star clusters, but none of these sources is a convincing candidate for a Galactic nucleus. The nuclei of the merger partners that created the Medusa have not yet been identified.

  16. Subwatt threshold cw Raman fiber-gas laser based on H2-filled hollow-core photonic crystal fiber.

    PubMed

    Couny, F; Benabid, F; Light, P S

    2007-10-01

    We report on what is, to our knowledge, the first cw pumped Raman fiber-gas laser based on a hollow-core photonic crystal fiber filled with hydrogen. The high efficiency of the gas-laser interaction inside the fiber allows operation in a single-pass configuration. The transmitted spectrum exhibits 99.99% of the output light at the Stokes wavelength and a pump power threshold as low as 2.25 W. The study of the Stokes emission evolution with pressure shows that highly efficient Raman amplification is still possible even at atmospheric pressure. The addition of fiber Bragg gratings to the system, creating a cavity at the Stokes wavelength, reduces the Raman threshold power below 600 mW. PMID:17930673

  17. The Formation of Glycine in Hot Cores: New Gas-grain Chemical Simulations of Star-forming Regions

    NASA Astrophysics Data System (ADS)

    Garrod, Robin

    2012-07-01

    Organic molecules of increasing complexity have been detected in the warm envelopes of star-forming cores, commonly referred to as "hot cores". Spectroscopic searches at mm/sub-mm wavelengths have uncovered both amines and carboxylic acids in these regions, as well as a range of other compounds including alcohols, ethers, esters, and nitriles. However, the simplest amino acid, glycine (NH2CH2COOH), has not yet been reliably detected in the ISM. There has been much interest in this molecule, due to its importance to the formation of proteins, and to life, while the positive identification of interstellar molecules of similar or greater complexity suggests that its existence in star-forming regions is plausible. I will present the results of recent models of hot-core chemistry that simulate the formation of both simple and complex molecules on the surfaces or within the ice mantles of dust grains. I will also present results from the first gas-grain astrochemical model to approach the question of amino-acid formation in hot cores. The formation of glycine in moderate abundance is found to be as efficient as that for similarly complex species, while its sublimation from the grains occurs at somewhat higher temperatures. However, simulated emission spectra based on the model results show that the degree of compactness of high-abundance regions, and the density and temperature profiles of the cores may be the key variables affecting the future detection of glycine, as well as other amino acids, and may explain its non-detection to date.

  18. Gas and grain chemical composition in cold cores as predicted by the Nautilus three-phase model

    NASA Astrophysics Data System (ADS)

    Ruaud, Maxime; Wakelam, Valentine; Hersant, Franck

    2016-07-01

    We present an extended version of the two-phase gas-grain code NAUTILUS to the three-phase modelling of gas and grain chemistry of cold cores. In this model, both the mantle and the surface are considered as chemically active. We also take into account the competition among reaction, diffusion and evaporation. The model predictions are confronted to ice observations in the envelope of low-mass and massive young stellar objects as well as towards background stars. Modelled gas-phase abundances are compared to species observed towards TMC-1 (CP) and L134N dark clouds. We find that our model successfully reproduces the observed ice species. It is found that the reaction-diffusion competition strongly enhances reactions with barriers and more specifically reactions with H2, which is abundant on grains. This finding highlights the importance having a good approach to determine the abundance of H2 on grains. Consequently, it is found that the major N-bearing species on grains go from NH3 to N2 and HCN when the reaction-diffusion competition is taken into account. In the gas phase and before a few 105 yr, we find that the three-phase model does not have a strong impact on the observed species compared to the two-phase model. After this time, the computed abundances dramatically decrease due to the strong accretion on dust, which is not counterbalanced by the desorption less efficient than in the two-phase model. This strongly constrains the chemical age of cold cores to be of the order of few 105 yr.

  19. Ex-Core CFD Analysis Results for the Prometheus Gas Reactor

    SciTech Connect

    Lorentz, Donald G.

    2007-01-30

    This paper presents the initial nozzle-to-nozzle (N2N) reactor vessel model scoping studies using computational fluid dynamics (CFD) analysis methods. The N2N model has been solved under a variety of different boundary conditions. This paper presents some of the basic hydraulic results from the N2N CFD analysis effort. It also demonstrates how designers were going to apply the analysis results to modify a number of the design features. The initial goals for developing a preliminary CFD N2N model were to establish baseline expectations for pressure drops and flow fields around the reactor core. Analysis results indicated that the averaged reactor vessel pressure drop for all analyzed cases was 46.9 kPa ({approx}6.8 psid). In addition, mass flow distributions to the three core fuel channel regions exhibited a nearly inverted profile to those specified for the in-core thermal/hydraulic design. During subsequent design iterations, the goal would have been to modify or add design features that would have minimized reactor vessel pressure drop and improved flow distribution to the inlet of the core.

  20. Cold gas in cluster cores: global stability analysis and non-linear simulations of thermal instability

    NASA Astrophysics Data System (ADS)

    Choudhury, Prakriti Pal; Sharma, Prateek

    2016-04-01

    We perform global linear stability analysis and idealized numerical simulations in global thermal balance to understand the condensation of cold gas from hot/virial atmospheres (coronae), in particular the intracluster medium (ICM). We pay particular attention to geometry (e.g. spherical versus plane-parallel) and the nature of the gravitational potential. Global linear analysis gives a similar value for the fastest growing thermal instability modes in spherical and Cartesian geometries. Simulations and observations suggest that cooling in haloes critically depends on the ratio of the cooling time to the free-fall time (tcool/tff). Extended cold gas condenses out of the ICM only if this ratio is smaller than a threshold value close to 10. Previous works highlighted the difference between the nature of cold gas condensation in spherical and plane-parallel atmospheres; namely, cold gas condensation appeared easier in spherical atmospheres. This apparent difference due to geometry arises because the previous plane-parallel simulations focused on in situ condensation of multiphase gas but spherical simulations studied condensation anywhere in the box. Unlike previous claims, our non-linear simulations show that there are only minor differences in cold gas condensation, either in situ or anywhere, for different geometries. The amount of cold gas depends on the shape of tcool/tff; gas has more time to condense if gravitational acceleration decreases towards the centre. In our idealized plane-parallel simulations with heating balancing cooling in each layer, there can be significant mass/energy/momentum transfer across layers that can trigger condensation and drive tcool/tff far beyond the critical value close to 10.

  1. In Vitro Effect of Porcelain Firing Cycle and Different Thicknesses of IPS E.max CAD Core on Marginal Accuracy of All-Ceramic Restorations

    PubMed Central

    Jalalian, Ezatollah; Zarbakhsh, Arash; Mohtashamrad, Zahra; Nourbakhsh, Nazanin; Jafarpour, Esmat

    2015-01-01

    Objectives: Marginal adaptation is important for long-term success of full-coverage restorations. The aim of this study was to determine the effect of porcelain firing cycle and different thicknesses of IPS e.max core on marginal accuracy of all-ceramic restorations. Materials and Methods: A standard stainless steel die with 0.8 mm classic chamfer finish line and 10° taper was used in this in vitro study. An impression was taken from the stainless steel die to fabricate 20 epoxy resin dies, which were then scanned and IPS e.max CAD cores were fabricated using computer-aided design/computer-aided manufacturing (CAD/CAM) technique in two groups of 10 with 0.7 mm (group A) and 0.4mm (group B) core thickness. Copings were then placed on their respective dies and randomly numbered. The amount of marginal gap was measured in 10 points under a stereomicroscope (×90 magnification) before and after porcelain veneering. Results: The mean gap in 0.7mm and 0.4mm core thicknesses was 15.62±2.55μm and 19.68±3.09μm before porcelain firing and 32.01±3.19μm and 35.24±3.8μm after porcelain firing. The difference in marginal gap between the two thicknesses was significant before porcelain firing but not significant after veneering. Significant differences were also found in the marginal gap before and after porcelain veneering in each group. Conclusion: The porcelain firing cycle increases marginal gap in IPS e.max CAD restorations; 0.3 mm decrease in core thickness slightly increased marginal discrepancy, however it was not significant. PMID:27507992

  2. Wettability modification of rock cores by fluorinated copolymer emulsion for the enhancement of gas and oil recovery

    NASA Astrophysics Data System (ADS)

    Feng, Chunyan; Kong, Ying; Jiang, Guancheng; Yang, Jinrong; Pu, Chunsheng; Zhang, Yuzhong

    2012-07-01

    The fluorine-containing acrylate copolymer emulsion was prepared with butyl acrylate, methacrylic acid and 1H, 1H, 2H, 2H-perfluorooctyl acrylate as monomers. Moreover, the structure of the copolymer was verified by Fourier transform infrared (FTIR), nuclear magnetic resonance (1H NMR and 19F NMR) and X-ray photoelectron spectroscopy (XPS) analyses. The results showed that all the monomers had been copolymerized and the presence of fluorine moieties. The contact angle (CA) analyses, capillary rise and imbibition spontaneous tests were used to estimate the influence of the copolymer emulsion on the wettability of gas reservoirs. It was observed that the rock surface was of large contact angles of water, oilfield sewage, hexadecane and crude oil after treatment with the emulsion. The capillary rise results indicated that the contact angles of water/air and oil/air systems increased from 60° and 32° to 121° and 80°, respectively, due to the emulsion treatment. Similarly, because of wettability alteration by the fluoropolymer, the imbibition of water and oil in rock core decreased significantly. Experimental results demonstrated that the copolymer emulsion can alter the wettability of porous media from strong liquid-wetting to gas-wetting. This work provides a cost-effective method to prepare the fluoropolymer which can increase gas deliverability by altering the wettability of gas-condensate reservoirs and mitigating the water block effect.

  3. Energy Economic Data Base (EEDB) Program: Phase 9 Update (1987) report, AGCC5-A supplement: Advanced gas turbine combined cycle (natural gas based) power generating station

    SciTech Connect

    Not Available

    1989-05-01

    The purpose of this AGCC5-A supplement is to identify direct equipment, material and labor costs, and indirect costs in sufficient detail to be used as a baseline for comparing the costs of combined-cycle gas-fired power plants with the costs of alternatives. This information is needed to satisfy the cost evaluation requirements of the Oak Ridge National Laboratory (ORNL) and the US Department of Energy (DOE). 11 refs., 9 figs., 15 tabs.

  4. Parametric thermodynamic analysis of closed-cycle gas-laser operation in space

    NASA Technical Reports Server (NTRS)

    Burns, R. K.

    1974-01-01

    Cycle efficiency and radiator area required were calculated for thermally and electrically pumped lasers operating in closed cycles with a compressor and the required heat exchangers. A thermally pumped laser included within a Brayton cycle was also analyzed. Performance of all components, including the laser, was parametrically varied. For the thermally pumped laser the cycle efficiencies range below 10 percent and are very sensitive to the high-pressure losses associated with the supersonic diffuser required at the laser cavity exit. The efficiencies predicted for the electrically pumped laser cycles range slightly higher, but radiator area also tends to be larger.

  5. Fuel efficient hydrodynamic containment for gas core fission reactor rocket propulsion. Final report, September 30, 1992--May 31, 1995

    SciTech Connect

    Sforza, P.M.; Cresci, R.J.

    1997-05-31

    Gas core reactors can form the basis for advanced nuclear thermal propulsion (NTP) systems capable of providing specific impulse levels of more than 2,000 sec., but containment of the hot uranium plasma is a major problem. The initial phase of an experimental study of hydrodynamic confinement of the fuel cloud in a gas core fission reactor by means of an innovative application of a base injection stabilized recirculation bubble is presented. The development of the experimental facility, a simulated thrust chamber approximately 0.4 m in diameter and 1 m long, is described. The flow rate of propellant simulant (air) can be varied up to about 2 kg/sec and that of fuel simulant (air, air-sulfur hexafluoride) up to about 0.2 kg/sec. This scale leads to chamber Reynolds numbers on the same order of magnitude as those anticipated in a full-scale nuclear rocket engine. The experimental program introduced here is focused on determining the size, geometry, and stability of the recirculation region as a function of the bleed ratio, i.e. the ratio of the injected mass flux to the free stream mass flux. A concurrent CFD study is being carried out to aid in demonstrating that the proposed technique is practical.

  6. Incorporating redox processes improves prediction of carbon and nutrient cycling and greenhouse gas emission

    NASA Astrophysics Data System (ADS)

    Tang, Guoping; Zheng, Jianqiu; Yang, Ziming; Graham, David; Gu, Baohua; Mayes, Melanie; Painter, Scott; Thornton, Peter

    2016-04-01

    Among the coupled thermal, hydrological, geochemical, and biological processes, redox processes play major roles in carbon and nutrient cycling and greenhouse gas (GHG) emission. Increasingly, mechanistic representation of redox processes is acknowledged as necessary for accurate prediction of GHG emission in the assessment of land-atmosphere interactions. Simple organic substrates, Fe reduction, microbial reactions, and the Windermere Humic Aqueous Model (WHAM) were added to a reaction network used in the land component of an Earth system model. In conjunction with this amended reaction network, various temperature response functions used in ecosystem models were assessed for their ability to describe experimental observations from incubation tests with arctic soils. Incorporation of Fe reduction reactions improves the prediction of the lag time between CO2 and CH4 accumulation. The inclusion of the WHAM model enables us to approximately simulate the initial pH drop due to organic acid accumulation and then a pH increase due to Fe reduction without parameter adjustment. The CLM4.0, CENTURY, and Ratkowsky temperature response functions better described the observations than the Q10 method, Arrhenius equation, and ROTH-C. As electron acceptors between O2 and CO2 (e.g., Fe(III), SO42‑) are often involved, our results support inclusion of these redox reactions for accurate prediction of CH4 production and consumption. Ongoing work includes improving the parameterization of organic matter decomposition to produce simple organic substrates, examining the influence of redox potential on methanogenesis under thermodynamically favorable conditions, and refining temperature response representation near the freezing point by additional model-experiment iterations. We will use the model to describe observed GHG emission at arctic and tropical sites.

  7. Simultaneous multi-design point approach to gas turbine on-design cycle analysis for aircraft engines

    NASA Astrophysics Data System (ADS)

    Schutte, Jeffrey Scott

    Gas turbine engines for aircraft applications are required to meet multiple performance and sizing requirements, subject to constraints established by the best available technology level, that are both directly and indirectly associated with the aerothermodynamic cycle. The performance requirements and limiting values of constraints that are considered by the cycle analyst conducting an engine cycle design occur at multiple operating conditions. The traditional approach to cycle analysis chooses a single design point with which to perform the on-design analysis. Additional requirements and constraints not transpiring at the design point must be evaluated in off-design analysis and therefore do not influence the cycle design. Such an approach makes it difficult to design the cycle to meet more than a few requirements and limits the number of different aerothermodynamic cycle designs that can reasonably be evaluated. Engine manufacturers have developed computational methods to create aerothermodynamic cycles that meet multiple requirements, but such methods are closely held secrets of their design process. This thesis presents a transparent and publicly available on-design cycle analysis method for gas turbine engines which generates aerothermodynamic cycles that simultaneously meet performance requirements and constraints at numerous design points. Such a method provides the cycle analyst the means to control all aspects of the aerothermodynamic cycle and provides the ability to parametrically create candidate engine cycles in greater numbers to comprehensively populate the cycle design space. The cycle design space represents all of the candidate engine cycles that meet the performance requirements for a particular application from which a "best" engine can be selected. This thesis develops the multi-design point on-design cycle analysis method labeled simultaneous MDP. The method is divided into three different phases resulting in an 11 step process to generate a

  8. In-flight gas phase growth of metal/multi layer graphene core shell nanoparticles with controllable sizes.

    PubMed

    Sengar, Saurabh K; Mehta, B R; Kumar, Rakesh; Singh, Vinod

    2013-01-01

    In this report, we present a general method for a continuous gas-phase synthesis of size-selected metal/multi layer graphene (MLG) core shell nanoparticles having a narrow size distribution of metal core and MLG shell for direct deposition onto any desired substrate kept under clean vacuum conditions. Evolution of MLG signature is clearly observed as the metal-carbon agglomerates get transformed to well defined metal/MLG core shell nanoparticles during their flight through the sintering zone. The growth takes place via an intermediate state of alloy nanoparticle (Pd-carbon) or composite nanoparticle (Cu-carbon), depending upon the carbon solubility in the metal and relative surface energy values. It has been also shown that metal/MLG nanoparticles can be converted to graphene shells. This study will have a large impact on how graphene or graphene based composite nanostructures can be grown and deposited in applications requiring controllable dimensions, varied substrate choice, large area and large scale depositions. PMID:24100702

  9. In-flight gas phase growth of metal/multi layer graphene core shell nanoparticles with controllable sizes

    PubMed Central

    Sengar, Saurabh K.; Mehta, B. R.; Kumar, Rakesh; Singh, Vinod

    2013-01-01

    In this report, we present a general method for a continuous gas-phase synthesis of size-selected metal/multi layer graphene (MLG) core shell nanoparticles having a narrow size distribution of metal core and MLG shell for direct deposition onto any desired substrate kept under clean vacuum conditions. Evolution of MLG signature is clearly observed as the metal-carbon agglomerates get transformed to well defined metal/MLG core shell nanoparticles during their flight through the sintering zone. The growth takes place via an intermediate state of alloy nanoparticle (Pd-carbon) or composite nanoparticle (Cu-carbon), depending upon the carbon solubility in the metal and relative surface energy values. It has been also shown that metal/MLG nanoparticles can be converted to graphene shells. This study will have a large impact on how graphene or graphene based composite nanostructures can be grown and deposited in applications requiring controllable dimensions, varied substrate choice, large area and large scale depositions. PMID:24100702

  10. Applications of plasma core reactors to terrestrial energy systems

    NASA Technical Reports Server (NTRS)

    Latham, T. S.; Biancardi, F. R.; Rodgers, R. J.

    1974-01-01

    Plasma core reactors offer several new options for future energy needs in addition to space power and propulsion applications. Power extraction from plasma core reactors with gaseous nuclear fuel allows operation at temperatures higher than conventional reactors. Highly efficient thermodynamic cycles and applications employing direct coupling of radiant energy are possible. Conceptual configurations of plasma core reactors for terrestrial applications are described. Closed-cycle gas turbines, MHD systems, photo- and thermo-chemical hydrogen production processes, and laser systems using plasma core reactors as prime energy sources are considered. Cycle efficiencies in the range of 50 to 65 percent are calculated for closed-cycle gas turbine and MHD electrical generators. Reactor advantages include continuous fuel reprocessing which limits inventory of radioactive by-products and thorium-U-233 breeder configurations with about 5-year doubling times.-

  11. An Introduction to Thermodynamic Performance Analysis of Aircraft Gas Turbine Engine Cycles Using the Numerical Propulsion System Simulation Code

    NASA Technical Reports Server (NTRS)

    Jones, Scott M.

    2007-01-01

    This document is intended as an introduction to the analysis of gas turbine engine cycles using the Numerical Propulsion System Simulation (NPSS) code. It is assumed that the analyst has a firm understanding of fluid flow, gas dynamics, thermodynamics, and turbomachinery theory. The purpose of this paper is to provide for the novice the information necessary to begin cycle analysis using NPSS. This paper and the annotated example serve as a starting point and by no means cover the entire range of information and experience necessary for engine performance simulation. NPSS syntax is presented but for a more detailed explanation of the code the user is referred to the NPSS User Guide and Reference document (ref. 1).

  12. Fuel-Cycle Fossil Energy Use and Greenhouse Gas Emissions of Fuel Ethanol Produced from U.S. Midwest Corn

    SciTech Connect

    Wang, Michael; Saricks, Christoper; Wu, May

    1997-12-19

    This study addresses two issues: (1) data and information essential to an informed choice about the corn-to-ethanol cycle are in need of updating, thanks to scientific and technological advances in both corn farming and ethanol production; and (2) generalized national estimates of energy intensities and greenhouse gas (GHG) production are of less relevance than estimates based specifically on activities and practices in the principal domestic corn production and milling region -- the upper Midwest.

  13. Levelized life-cycle costs for four residue-collection systems and four gas-production systems

    SciTech Connect

    Thayer, G.R.; Rood, P.L.; Williamson, K.D. Jr.; Rollett, H.

    1983-01-01

    Technology characterizations and life-cycle costs were obtained for four residue-collection systems and four gas-production systems. All costs are in constant 1981 dollars. The residue-collection systems were cornstover collection, wheat-straw collection, soybean-residue collection, and wood chips from forest residue. The life-cycle costs ranged from $19/ton for cornstover collection to $56/ton for wood chips from forest residues. The gas-production systems were low-Btu gas from a farm-size gasifier, solar flash pyrolysis of biomass, methane from seaweed farms, and hydrogen production from bacteria. Life-cycle costs ranged from $3.3/10/sup 6/ Btu for solar flash pyrolysis of biomass to $9.6/10/sup 6/ Btu for hydrogen from bacteria. Sensitivity studies were also performed for each system. The sensitivity studies indicated that fertilizer replacement costs were the dominate costs for the farm-residue collection, while residue yield was most important for the wood residue. Feedstock costs were most important for the flash pyrolysis. Yields and capital costs are most important for the seaweed farm and the hydrogen from bacteria system.

  14. Assessment of the performance of a natural gas liquefaction cycle using natural refrigerants

    NASA Astrophysics Data System (ADS)

    Yoon, Jung-In; Choi, Kwang-Hwan; Lee, Ho-Sang; Kim, Hyeon-Ju; Son, Chang-Hyo

    2015-01-01

    This study proposed a new cascade liquefaction cycle that uses CO2-C2H6-N2 and CO2-N2, analyzed its performance and exergy using HYSYS which is the liquefaction process simulator, and checked its applicability. The analysis results showed that the CO2-C2H6-N2 liquefaction cycle was more efficient and the CO2-N2 liquefaction cycle was better in terms of exergy loss. Furthermore, the liquefaction cycle that uses the CO2-N2 refrigerant showed lower thermal efficiency and higher compressor work than the conventional liquefaction cycle that uses C3H8-C2H4-C1H4. Thus, the proposed CO2-C2H6-N2 cycle is expected to have reasonably high thermal efficiency and potential for a high liquefaction capacity.

  15. Analysis of a topping-cycle, aircraft, gas-turbine-engine system which uses cryogenic fuel

    NASA Technical Reports Server (NTRS)

    Turney, G. E.; Fishbach, L. H.

    1984-01-01

    A topping-cycle aircraft engine system which uses a cryogenic fuel was investigated. This system consists of a main turboshaft engine that is mechanically coupled (by cross-shafting) to a topping loop, which augments the shaft power output of the system. The thermodynamic performance of the topping-cycle engine was analyzed and compared with that of a reference (conventional) turboshaft engine. For the cycle operating conditions selected, the performance of the topping-cycle engine in terms of brake specific fuel consumption (bsfc) was determined to be about 12 percent better than that of the reference turboshaft engine. Engine weights were estimated for both the topping-cycle engine and the reference turboshaft engine. These estimates were based on a common shaft power output for each engine. Results indicate that the weight of the topping-cycle engine is comparable with that of the reference turboshaft engine.

  16. Volcanic controls on ash iron solubility: thermodynamic modeling of gas-ash interaction in the hot core of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Hoshyaripour, G.; Hort, M.; Langmann, B.

    2012-04-01

    Recently it has been shown that volcanic ash can act as a fertilizer for phytoplankton bloom by injecting bio-available iron into the surface ocean. However, it is also well known that iron in volcanic ash at least at its generation point (i.e. magma) is mostly in insoluble form, i.e. not bio-available. Although different volcanic and atmospheric processes are assumed to contribute to the transformation of insoluble iron into soluble salts, the causes of iron mobilization in volcanic ash are poorly constrained. Here we explore the volcanic control on the mobilization of iron in volcanic ash in the hot core of volcanic plumes (T>600° C) based on thermodynamic equilibrium considerations. A conceptual box model is considered for the hot core in which 1000° C magmatic gas, ash and 25° C ambient air are mixed. The initial composition of volcanic gas and ash are parameterized based on three types of tectonic settings (convergent plate, divergent plate, and hot spot) and basaltic to rhyolitic magmas. The effect of the initial oxidation state is also considered by changing the oxygen fugacity. First, magmatic oxides (i.e. SiO2, FeO, MgO etc) are titrated into the magmatic gas at constant temperature and fugacity in order to generate the initial iron carrying minerals. Since the alteration of ash composition is mainly diffusion controlled, we assume that inside the hot core of the volcanic plume the Fe speciation is only affected at or near to the ash surface. Results show that the main initial iron carrying minerals are usually ilmenite and fayalite with some addition of pyhrrotite at reduced conditions in divergent plate and hot spot settings. Then the 1000° C magmatic gas-ash mixture is mixed with the 25° C air (N2 79%, O2 21%) until a temperature of 600° C is reached. Results demonstrate that the hot core functions as an oxidizing reactor for the ash surface transforming the whole Fe2+ minerals to Fe3+ species while being cooled to 600° C. However, in reduced

  17. Picosecond pulses compression at 1053-nm center wavelength by using a gas-filled hollow-core fiber compressor

    NASA Astrophysics Data System (ADS)

    Huang, Zhi-Yuan; Wang, Ding; Leng, Yu-Xin; Dai, Ye

    2015-01-01

    We theoretically study the nonlinear compression of picosecond pulses with 10-mJ of input energy at the 1053-nm center wavelength by using a one-meter-long gas-filled hollow-core fiber (HCF) compressor and considering the third-order dispersion (TOD) effect. It is found that when the input pulse is about 1 ps/10 mJ, it can be compressed down to less than 20 fs with a high transmission efficiency. The gas for optimal compression is krypton gas which is filled in a HCF with a 400-μm inner diameter. When the input pulse duration is increased to 5 ps, it can also be compressed down to less than 100 fs efficiently under proper conditions. The results show that the TOD effect has little impact on picosecond pulse compression and the HCF compressor can be applied on compressing picosecond pulses efficiently with a high compression ratio, which will benefit the research of high-field laser physics. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204328, 61221064, 61078037, 11127901, and 11134010), the National Basic Research Program of China (Grant No. 2011CB808101), the Commission of Science and Technology of Shanghai, China (Grant No. 12dz1100700), the Natural Science Foundation of Shanghai, China (Grant No. 13ZR1414800), and the International Science and Technology Cooperation Program of China (Grant No. 2011DFA11300).

  18. Examination of core samples from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Effects of retrieval and preservation

    SciTech Connect

    Kneafsey, T.J.; Liu, T.J. H.; Winters, W.; Boswell, R.; Hunter, R.; Collett, T.S.

    2011-06-01

    Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented.

  19. Examination of core samples from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope: Effects of retrieval and preservation

    USGS Publications Warehouse

    Kneafsey, T.J.; Lu, H.; Winters, W.; Boswell, R.; Hunter, R.; Collett, T.S.

    2011-01-01

    Collecting and preserving undamaged core samples containing gas hydrates from depth is difficult because of the pressure and temperature changes encountered upon retrieval. Hydrate-bearing core samples were collected at the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well in February 2007. Coring was performed while using a custom oil-based drilling mud, and the cores were retrieved by a wireline. The samples were characterized and subsampled at the surface under ambient winter arctic conditions. Samples thought to be hydrate bearing were preserved either by immersion in liquid nitrogen (LN), or by storage under methane pressure at ambient arctic conditions, and later depressurized and immersed in LN. Eleven core samples from hydrate-bearing zones were scanned using x-ray computed tomography to examine core structure and homogeneity. Features observed include radial fractures, spalling-type fractures, and reduced density near the periphery. These features were induced during sample collection, handling, and preservation. Isotopic analysis of the methane from hydrate in an initially LN-preserved core and a pressure-preserved core indicate that secondary hydrate formation occurred throughout the pressurized core, whereas none occurred in the LN-preserved core, however no hydrate was found near the periphery of the LN-preserved core. To replicate some aspects of the preservation methods, natural and laboratory-made saturated porous media samples were frozen in a variety of ways, with radial fractures observed in some LN-frozen sands, and needle-like ice crystals forming in slowly frozen clay-rich sediments. Suggestions for hydrate-bearing core preservation are presented.

  20. Effect of an aerodynamic helmet on head temperature, core temperature, and cycling power compared with a traditional helmet.

    PubMed

    Lee, Joshua F; Brown, Skyler R; Lange, Andrew P; Brothers, R Matthew

    2013-12-01

    Nonvented "aerodynamic helmets" reduce wind resistance but may increase head (Th) and gastrointestinal (Tgi) temperature and reduce performance when worn in hot conditions. This study tested the hypothesis that Th and Tgi would be greater during low-intensity cycling (LIC) in the heat while wearing an aero helmet (AERO) vs. a traditional vented racing helmet (REG). This study also tested the hypothesis that Th, Tgi, and finish time would be greater, and power output would be reduced during a self-paced time trial in the heat with AERO vs. REG. Ten highly trained heat-acclimated endurance athletes conducted LIC (50% V[Combining Dot Above]O2max, LIC) and a high-intensity 12-km self-paced time trial (12-km TT) on a cycle ergometer in 39° C on 2 different days (AERO and REG), separated by >48 hours. During LIC, Th was higher at minute 7.5 and all time points thereafter in AERO vs. REG (p < 0.05). Similarly, during the 12-km TT, Th was higher at minutes 12.5, 15, and 17.5 in AERO vs. REG (p < 0.05). Heart rate (HR) and Tgi increased during LIC and during 12-km TT (both p < 0.001); however, no significant interaction (helmet × time) existed for HR or Tgi at either intensity (all p > 0.05). No group differences existed for finish time or power output during the 12-km TT (both p > 0.05). In conclusion, Th becomes elevated during cycling in the heat with an aero helmet compared with a traditional vented racing helmet during LIC and high-intensity cycling, yet Tgi and HR responses are similar irrespective of helmet type and Th. Furthermore, the higher Th that develops when an aero helmet is worn during cycling in the heat does not affect power output or cycling performance during short-duration high-intensity events. PMID:23539083

  1. Dynamics and control modeling of the closed-cycle gas turbine (GT-HTGR) power plant

    SciTech Connect

    Bardia, A.

    1980-02-01

    The simulation if presented for the 800-MW(e) two-loop GT-HTGR plant design with the REALY2 transient analysis computer code, and the modeling of control strategies called for by the inherently unique operational requirements of a multiple loop GT-HTGR is described. Plant control of the GT-HTGR is constrained by the nature of its power conversion loops (PCLs) in which the core cooling flow and the turbine flow are directly related and thus changes in flow affect core cooling as well as turbine power. Additionally, the high thermal inertia of the reactor core precludes rapid changes in the temperature of the turbine inlet flow.

  2. Thermal modeling of core sampling in flammable gas waste tanks. Part 1: Push-mode sampling

    SciTech Connect

    Unal, C.; Stroh, K.; Pasamehmetoglu, K.O.

    1997-08-01

    The radioactive waste stored in underground storage tanks at Hanford site is routinely being sampled for waste characterization purposes. The push- and rotary-mode core sampling is one of the sampling methods employed. The waste includes mixtures of sodium nitrate and sodium nitrite with organic compounds that can produce violent exothermic reactions if heated above 160 C during core sampling. A self-propagating waste reaction would produce very high temperatures that eventually result in failure of the tank and radioactive material releases to environment. A two-dimensional thermal model based on a lumped finite volume analysis method is developed. The enthalpy of each node is calculated from the first law of thermodynamics. A flash temperature and effective contact area concept were introduced to account the interface temperature rise. No maximum temperature rise exceeding the critical value of 60 C was found in the cases studied for normal operating conditions. Several accident conditions are also examined. In these cases it was found that the maximum drill bit temperature remained below the critical reaction temperature as long as a 30 scfm purge flow is provided the push-mode drill bit during sampling in rotary mode. The failure to provide purge flow resulted in exceeding the limiting temperatures in a relatively short time.

  3. Organic Rankine Cycle for Residual Heat to Power Conversion in Natural Gas Compressor Station. Part I: Modelling and Optimisation Framework

    NASA Astrophysics Data System (ADS)

    Chaczykowski, Maciej

    2016-06-01

    Basic organic Rankine cycle (ORC), and two variants of regenerative ORC have been considered for the recovery of exhaust heat from natural gas compressor station. The modelling framework for ORC systems has been presented and the optimisation of the systems was carried out with turbine power output as the variable to be maximized. The determination of ORC system design parameters was accomplished by means of the genetic algorithm. The study was aimed at estimating the thermodynamic potential of different ORC configurations with several working fluids employed. The first part of this paper describes the ORC equipment models which are employed to build a NLP formulation to tackle design problems representative for waste energy recovery on gas turbines driving natural gas pipeline compressors.

  4. Life cycle carbon footprint of shale gas: review of evidence and implications.

    PubMed

    Weber, Christopher L; Clavin, Christopher

    2012-06-01

    The recent increase in the production of natural gas from shale deposits has significantly changed energy outlooks in both the US and world. Shale gas may have important climate benefits if it displaces more carbon-intensive oil or coal, but recent attention has discussed the potential for upstream methane emissions to counteract this reduced combustion greenhouse gas emissions. We examine six recent studies to produce a Monte Carlo uncertainty analysis of the carbon footprint of both shale and conventional natural gas production. The results show that the most likely upstream carbon footprints of these types of natural gas production are largely similar, with overlapping 95% uncertainty ranges of 11.0-21.0 g CO(2)e/MJ(LHV) for shale gas and 12.4-19.5 g CO(2)e/MJ(LHV) for conventional gas. However, because this upstream footprint represents less than 25% of the total carbon footprint of gas, the efficiency of producing heat, electricity, transportation services, or other function is of equal or greater importance when identifying emission reduction opportunities. Better data are needed to reduce the uncertainty in natural gas's carbon footprint, but understanding system-level climate impacts of shale gas, through shifts in national and global energy markets, may be more important and requires more detailed energy and economic systems assessments. PMID:22545623

  5. Peculiarities of distribution of gas-dynamic manifestations in mines of the Kuznetsk coal basin by days of the weekly cycle

    SciTech Connect

    Oparin, V.N.; Ludzish, V.S.; Kulakov, G.I.; Rudakov, V.A.

    2005-04-01

    The peculiarities of the origin of gas-dynamic events (rock, coal, and gas outbursts, methane ignition) in the Kuznetsk Basin mines in 1988 - 2004 are analyzed. A review is presented for information on recent accident and injury rate caused by disastrous gas-dynamic manifestations. The effect of bimodal frequency distribution of gas-dynamic events generated by explosion and burning of methane is revealed within a generalized weekly cycle.

  6. Masking of the circadian rhythms of heart rate and core temperature by the rest-activity cycle in man

    NASA Technical Reports Server (NTRS)

    Gander, Philippa H.; Connell, Linda J.; Graeber, R. Curtis

    1986-01-01

    Experiments were conducted to estimate the magnitude of the masking effect produced in humans by alternate periods of physical activity and rest or sleep on the circadian rhythms of heart rate and core temperature. The heart rate, rectal temperature, and nondominant wrist activity were monitored in 12 male subjects during 6 days of normal routine at home and during 6 days of controlled bed-rest regimen. The comparisons of averaged waveforms for the activity, heart rate, and temperature indicated that about 45 percent of the range of the circadian heart rate rhythm during normal routine and about 14 percent of the range of the circadian temperature rhythm were attributable to the effects of activity. The smaller effect of activity on the temperature rhythm may be partially attributable to the fact that core temperature is being more rigorously conserved than heart rate, at least during moderate exercise.

  7. Direct fiber comb stabilization to a gas-filled hollow-core photonic crystal fiber.

    PubMed

    Wu, Shun; Wang, Chenchen; Fourcade-Dutin, Coralie; Washburn, Brian R; Benabid, Fetah; Corwin, Kristan L

    2014-09-22

    We have isolated a single tooth from a fiber laser-based optical frequency comb for nonlinear spectroscopy and thereby directly referenced the comb. An 89 MHz erbium fiber laser frequency comb is directly stabilized to the P(23) (1539.43 nm) overtone transition of (12)C(2)H(2) inside a hollow-core photonic crystal fiber. To do this, a single comb tooth is isolated and amplified from 20 nW to 40 mW with sufficient fidelity to perform saturated absorption spectroscopy. The fractional stability of the comb, ~7 nm away from the stabilized tooth, is shown to be 6 × 10(-12) at 100 ms gate time, which is over an order of magnitude better than that of a comb referenced to a GPS-disciplined Rb oscillator. PMID:25321837

  8. A SEARCH FOR CO-EVOLVING ION AND NEUTRAL GAS SPECIES IN PRESTELLAR MOLECULAR CLOUD CORES

    SciTech Connect

    Tassis, Konstantinos; Hezareh, Talayeh; Willacy, Karen

    2012-11-20

    A comparison between the widths of ion and neutral molecule spectral lines has been recently used to estimate the strength of the magnetic field in turbulent star-forming regions. However, the ion (HCO{sup +}) and neutral (HCN) species used in such studies may not be necessarily co-evolving at every scale and density, and thus, may not trace the same regions. Here, we use coupled chemical/dynamical models of evolving prestellar molecular cloud cores including non-equilibrium chemistry, with and without magnetic fields, to study the spatial distribution of HCO{sup +} and HCN, which have been used in observations of spectral line width differences to date. In addition, we seek new ion-neutral pairs that are good candidates for such observations, because they have similar evolution and are approximately co-spatial in our models. We identify three such good candidate pairs: HCO{sup +}/NO, HCO{sup +}/CO, and NO{sup +}/NO.

  9. Plasmon response of a quantum-confined electron gas probed by core-level photoemission

    SciTech Connect

    Ozer, Mustafa M; Moon, Eun Ju; Eguiluz, Adolfo G; Weitering, Harm H

    2011-01-01

    We demonstrate the existence of quantized 'bulk' plasmons in ultrathin magnesium films on Si(111) by analyzing plasmon-loss satellites in core-level photoemission spectra, recorded as a function of the film thickness d. Remarkably, the plasmon energy is shown to vary as 1/d{sup 2} all the way down to three atomic layers. The loss spectra are dominated by the n=1 and n=2 normal modes, consistent with the excitation of plasmons involving quantized electronic subbands. With decreasing film thickness, spectral weight is gradually transferred from the plasmon modes to the low-energy single-particle excitations. These results represent striking manifestations of the role of quantum confinement on plasmon resonances in precisely controlled nanostructures.

  10. THE NATURE OF FILAMENTARY COLD GAS IN THE CORE OF THE VIRGO CLUSTER

    SciTech Connect

    Werner, N.; Canning, R. E. A.; Allen, S. W.; Simionescu, A.; Von der Linden, A.; Oonk, J. B. R.; Kos, J.; Van Weeren, R. J.; Nulsen, P. E. J.; Edge, A. C.; Fabian, A. C.; Reynolds, C. S.; Ruszkowski, M.

    2013-04-20

    We present a multi-wavelength study of the emission-line nebulae located {approx}38'' (3 kpc in projection) southeast of the nucleus of M87, the central dominant galaxy of the Virgo Cluster. We report the detection of far-infrared (FIR) [C II] line emission at 158 {mu}m from the nebulae using observations made with the Herschel Photodetector Array Camera and Spectrometer (PACS). The infrared line emission is extended and co-spatial with optical H{alpha}+ [N II], far-ultraviolet C IV lines, and soft X-ray emission. The filamentary nebulae evidently contain multi-phase material spanning a temperature range of at least five orders of magnitude, from {approx}100 K to {approx}10{sup 7} K. This material has most likely been uplifted by the active galactic nucleus from the center of M87. The thermal pressure of the 10{sup 4} K phase appears to be significantly lower than that of the surrounding hot intracluster medium (ICM), indicating the presence of additional turbulent and magnetic pressure in the filaments. If the turbulence in the filaments is subsonic then the magnetic field strength required to balance the pressure of the surrounding ICM is B {approx} 30-70 {mu}G. The spectral properties of the soft X-ray emission from the filaments indicate that it is due to thermal plasma with kT {approx} 0.5-1 keV, which is cooling by mixing with the cold gas and/or radiatively. Charge exchange can be ruled out as a significant source of soft X-rays. Both cooling and mixing scenarios predict gas with a range of temperatures. This is at first glance inconsistent with the apparent lack of X-ray emitting gas with kT < 0.5 keV. However, we show that the missing very soft X-ray emission could be absorbed by the cold gas in the filaments with an integrated hydrogen column density of N{sub H} {approx} 1.6 Multiplication-Sign 10{sup 21} cm{sup -2}, providing a natural explanation for the apparent temperature floor to the X-ray emission at kT {approx} 0.5 keV. The FIR through ultraviolet

  11. Crew radiation dose from the plume of a high impulse gas-core nuclear rocket during a Mars mission.

    NASA Technical Reports Server (NTRS)

    Masser, C. C.

    1971-01-01

    Analytical calculations are performed to determine the radiation dose rate and total dose to the crew of a gas-core nuclear rocket from the fission fragments located throughout the plume volume. The radiation dose from the plume fission fragments to two crew locations of 100 and 200 meters from the nozzle exit are calculated. It is found that, in the case of the most probable fission fragment retention time of 100 seconds, the crew must be protected from the radiation dose. Five centimeters of lead shielding would reduce the radiation dose by two orders of magnitude thereby protecting the crew. The increase in vehicle weight would be insignificant (7150 kg to a vehicle gross weight of 0.94 million kg).

  12. Two techniques for temporal pulse compression in gas-filled hollow-core kagomé photonic crystal fiber.

    PubMed

    Mak, K F; Travers, J C; Joly, N Y; Abdolvand, A; Russell, P St J

    2013-09-15

    We demonstrate temporal pulse compression in gas-filled kagomé hollow-core photonic crystal fiber (PCF) using two different approaches: fiber-mirror compression based on self-phase modulation under normal dispersion, and soliton effect self-compression under anomalous dispersion with a decreasing pressure gradient. In the first, efficient compression to near-transform-limited pulses from 103 to 10.6 fs was achieved at output energies of 10.3 μJ. In the second, compression from 24 to 6.8 fs was achieved at output energies of 6.6 μJ, also with near-transform-limited pulse shapes. The results illustrate the potential of kagomé-PCF for postprocessing the output of fiber lasers. We also show that, using a negative pressure gradient, ultrashort pulses can be delivered directly into vacuum. PMID:24104822

  13. Efficient anti-Stokes generation via intermodal stimulated Raman scattering in gas-filled hollow-core PCF.

    PubMed

    Trabold, B M; Abdolvand, A; Euser, T G; Russell, P St J

    2013-12-01

    A strong anti-Stokes Raman signal, from the vibrational Q(1) transition of hydrogen, is generated in gas-filled hollow-core photonic crystal fiber. To be efficient, this process requires phase-matching, which is not automatically provided since the group velocity dispersion is typically non-zero and--inside a fiber--cannot be compensated for using a crossed-beam geometry. Phase-matching can however be arranged by exploiting the different dispersion profiles of higher-order modes. We demonstrate the generation of first and second anti-Stokes signals in higher-order modes by pumping with an appropriate mixture of fundamental and a higher-order modes, synthesized using a spatial light modulator. Conversion efficiencies as high as 5.3% are achieved from the pump to the first anti-Stokes band. PMID:24514522

  14. Simulating Astro-H Observations of Sloshing Gas Motions in the Cores of Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    ZuHone, J. A.; Miller, E. D.; Simionescu, A.; Bautz, M. W.

    2016-04-01

    Astro-H will be the first X-ray observatory to employ a high-resolution microcalorimeter, capable of measuring the shift and width of individual spectral lines to the precision necessary for estimating the velocity of the diffuse plasma in galaxy clusters. This new capability is expected to bring significant progress in understanding the dynamics, and therefore the physics, of the intracluster medium. However, because this plasma is optically thin, projection effects will be an important complicating factor in interpreting future Astro-H measurements. To study these effects in detail, we performed an analysis of the velocity field from simulations of a galaxy cluster experiencing gas sloshing and generated synthetic X-ray spectra, convolved with model Astro-H Soft X-ray Spectrometer (SXS) responses. We find that the sloshing motions produce velocity signatures that will be observable by Astro-H in nearby clusters: the shifting of the line centroid produced by the fast-moving cold gas underneath the front surface, and line broadening produced by the smooth variation of this motion along the line of sight. The line shapes arising from inviscid or strongly viscous simulations are very similar, indicating that placing constraints on the gas viscosity from these measurements will be difficult. Our spectroscopic analysis demonstrates that, for adequate exposures, Astro-H will be able to recover the first two moments of the velocity distribution of these motions accurately, and in some cases multiple velocity components may be discerned. The simulations also confirm the importance of accurate treatment of point-spread function scattering in the interpretation of Astro-H/SXS spectra of cluster plasmas.

  15. Life cycle energy and greenhouse gas emissions for an ethanol production process based on blue-green algae.

    PubMed

    Luo, Dexin; Hu, Zushou; Choi, Dong Gu; Thomas, Valerie M; Realff, Matthew J; Chance, Ronald R

    2010-11-15

    Ethanol can be produced via an intracellular photosynthetic process in cyanobacteria (blue-green algae), excreted through the cell walls, collected from closed photobioreactors as a dilute ethanol-in-water solution, and purified to fuel grade ethanol. This sequence forms the basis for a biofuel production process that is currently being examined for its commercial potential. In this paper, we calculate the life cycle energy and greenhouse gas emissions for three different system scenarios for this proposed ethanol production process, using process simulations and thermodynamic calculations. The energy required for ethanol separation increases rapidly for low initial concentrations of ethanol, and, unlike other biofuel systems, there is little waste biomass available to provide process heat and electricity to offset those energy requirements. The ethanol purification process is a major consumer of energy and a significant contributor to the carbon footprint. With a lead scenario based on a natural-gas-fueled combined heat and power system to provide process electricity and extra heat and conservative assumptions around the ethanol separation process, the net life cycle energy consumption, excluding photosynthesis, ranges from 0.55 MJ/MJ(EtOH) down to 0.20 MJ/ MJ(EtOH), and the net life cycle greenhouse gas emissions range from 29.8 g CO₂e/MJ(EtOH) down to 12.3 g CO₂e/MJ(EtOH) for initial ethanol concentrations from 0.5 wt % to 5 wt %. In comparison to gasoline, these predicted values represent 67% and 87% reductions in the carbon footprint for this ethanol fuel on a energy equivalent basis. Energy consumption and greenhouse gas emissions can be further reduced via employment of higher efficiency heat exchangers in ethanol purification and/ or with use of solar thermal for some of the process heat. PMID:20968295

  16. Gas turbine ceramic-coated-vane concept with convection-cooled porous metal core

    NASA Technical Reports Server (NTRS)

    Kascak, A. F.; Liebert, C. H.; Handschuh, R. F.; Ludwig, L. P.

    1981-01-01

    Analysis and flow experiments on a ceramic-coated-porous-metal vane concept indicated the feasibility, from a heat transfer standpoint, of operating in a high-temperature (2500 F) gas turbine cascade facility. The heat transfer and pressure drop calculations provided a basis for selecting the ceramic layer thickness (to 0.08 in.), which was found to be the dominant factor in the overall heat transfer coefficient. Also an approximate analysis of the heat transfer in the vane trailing edge revealed that with trailing-edge ejection the ceramic thickness could be reduced to (0.01 in.) in this portion of the vane.

  17. Tunable frequency-up/down conversion in gas-filled hollow-core photonic crystal fibers.

    PubMed

    Saleh, Mohammed F; Biancalana, Fabio

    2015-09-15

    Based on the interplay between photoionization and Raman effects in gas-filled photonic crystal fibers, we propose a new optical device to control frequency conversion of ultrashort pulses. By tuning the input-pulse energy, the output spectrum can be either down-converted, up-converted, or even frequency-shift compensated. For low input energies, the Raman effect is dominant and leads to a redshift that increases linearly during propagation. For larger pulse energies, photoionization starts to take over the frequency-conversion process and induces a strong blueshift. The fiber-output pressure can be used as an additional degree of freedom to control the spectrum shift. PMID:26371900

  18. Evaluation of Indirect Combined Cycle in Very High Temperature Gas--Cooled Reactor

    SciTech Connect

    Chang Oh; Robert Barner; Cliff Davis; Steven Sherman; Paul Pickard

    2006-10-01

    The U.S. Department of Energy and Idaho National Laboratory are developing a very high temperature reactor to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is twofold: (a) efficient, low-cost energy generation and (b) hydrogen production. Although a next-generation plant could be developed as a single-purpose facility, early designs are expected to be dual purpose, as assumed here. A dual-purpose design with a combined cycle of a Brayton top cycle and a bottom Rankine cycle was investigated. An intermediate heat transport loop for transporting heat to a hydrogen production plant was used. Helium, CO2, and a helium-nitrogen mixture were studied to determine the best working fluid in terms of the cycle efficiency. The relative component sizes were estimated for the different working fluids to provide an indication of the relative capital costs. The relative size of the turbomachinery was measured by comparing the power input/output of the component. For heat exchangers the volume was computed and compared. Parametric studies away from the baseline values of the cycle were performed to determine the effects of varying conditions in the cycle. This gives some insight into the sensitivity of the cycle to various operating conditions as well as trade-offs between efficiency and component size. Parametric studies were carried out on reactor outlet temperature, mass flow, pressure, and turbine cooling.

  19. Steam Generator Component Model in a Combined Cycle of Power Conversion Unit for Very High Temperature Gas-Cooled Reactor

    SciTech Connect

    Oh, Chang H; Han, James; Barner, Robert; Sherman, Steven R

    2007-06-01

    The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP), Very High Temperature Gas-Cooled Reactor (VHTR) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in its early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. A combined cycle is considered as one of the power conversion units to be coupled to the very high-temperature gas-cooled reactor (VHTR). The combined cycle configuration consists of a Brayton top cycle coupled to a Rankine bottoming cycle by means of a steam generator. A detailed sizing and pressure drop model of a steam generator is not available in the HYSYS processes code. Therefore a four region model was developed for implementation into HYSYS. The focus of this study was the validation of a HYSYS steam generator model of two phase flow correlations. The correlations calculated the size and heat exchange of the steam generator. To assess the model, those calculations were input into a RELAP5 model and its results were compared with HYSYS results. The comparison showed many differences in parameters such as the heat transfer coefficients and revealed the different methods used by the codes. Despite differences in approach, the overall results of heat transfer were in good agreement.

  20. A safety assessment of rotary mode core sampling in flammable gas single shell tanks: Hanford Site, Richland, Washington

    SciTech Connect

    Raymond, R.E.

    1996-04-15

    This safety assessment (SA) addresses each of the required elements associated with the installation, operation, and removal of a rotary-mode core sampling (RMCS) device in flammable-gas single-shell tanks (SSTs). The RMCS operations are needed in order to retrieve waste samples from SSTs with hard layers of waste for which push-mode sampling is not adequate for sampling. In this SA, potential hazards associated with the proposed action were identified and evaluated systematically. Several potential accident cases that could result in radiological or toxicological gas releases were identified and analyzed and their consequences assessed. Administrative controls, procedures and design changes required to eliminate or reduce the potential of hazards were identified. The accidents were analyzed under nine categories, four of which were burn scenarios. In SSTS, burn accidents result in unacceptable consequences because of a potential dome collapse. The accidents in which an aboveground burn propagates into the dome space were shown to be in the ``beyond extremely unlikely`` frequency category. Given the unknown nature of the gas-release behavior in the SSTS, a number of design changes and administrative controls were implemented to achieve these low frequencies. Likewise, drill string fires and dome space fires were shown to be very low frequency accidents by taking credit for the design changes, controls, and available experimental and analytical data. However, a number of Bureau of Mines (BOM) tests must be completed before some of the burn accidents can be dismissed with high confidence. Under the category of waste fires, the possibility of igniting the entrapped gases and the waste itself were analyzed. Experiments are being conducted at the BOM to demonstrate that the drill bit is not capable of igniting the trapped gas in the waste. Laboratory testing and thermal analysis demonstrated that, under normal operating conditions, the drill bit will not create high

  1. Testing and analysis of the impact on engine cycle parameters and control system modifications using hydrogen or methane as fuel in an industrial gas turbine

    NASA Astrophysics Data System (ADS)

    Funke, H. H.-W.; Keinz, J.; Börner, S.; Hendrick, P.; Elsing, R.

    2016-07-01

    The paper highlights the modification of the engine control software of the hydrogen (H2) converted gas turbine Auxiliary Power Unit (APU) GTCP 36-300 allowing safe and accurate methane (CH4) operation achieved without mechanical changes of the metering unit. The acceleration and deceleration characteristics of the engine controller from idle to maximum load are analyzed comparing H2 and CH4. Also, the paper presents the influence on the thermodynamic cycle of gas turbine resulting from the different fuels supported by a gas turbine cycle simulation of H2 and CH4 using the software GasTurb.

  2. Fuel Summary for Peach Bottom Unit 1 High-Temperature Gas-Cooled Reactor Cores 1 and 2

    SciTech Connect

    Karel I. Kingrey

    2003-04-01

    This fuel summary report contains background and summary information for the Peach Bottom Unit 1, High-Temperature, Gas-Cooled Reactor Cores 1 and 2. This report contains detailed information about the fuel in the two cores, the Peach Bottom Unit 1 operating history, nuclear parameters, physical and chemical characteristics, and shipping and storage canister related data. The data in this document have been compiled from a large number of sources and are not qualified beyond the qualification of the source documents. This report is intended to provide an overview of the existing data pertaining to spent fuel management and point to pertinent reference source documents. For design applications, the original source documentation must be used. While all referenced sources are available as records or controlled documents at the Idaho National Engineering and Environmental Laboratory (INEEL), some of the sources were marked as informal or draft reports. This is noted where applicable. In some instances, source documents are not consistent. Where they are known, this document identifies those instances and provides clarification where possible. However, as stated above, this document has not been independently qualified and such clarifications are only included for information purposes. Some of the information in this summary is available in multiple source documents. An effort has been made to clearly identify at least one record document as the source for the information included in this report.

  3. Portable optical frequency standard based on sealed gas-filled hollow-core fiber using a novel encapsulation technique

    NASA Astrophysics Data System (ADS)

    Triches, Marco; Brusch, Anders; Hald, Jan

    2015-12-01

    A portable stand-alone optical frequency standard based on a gas-filled hollow-core photonic crystal fiber is developed to stabilize a fiber laser to the ^{13}{C}_2{H}_2 P(16) (ν _1 + ν _3) transition at 1542 nm using saturated absorption. A novel encapsulation technique is developed to permanently seal the hollow-core fiber with easy light coupling, showing negligible pressure increase over two months. The locked laser shows a fractional frequency instability below 8 × 10^{-12} for an averaging time up to 104 s. The lock-point repeatability over one month is 2.6 × 10^{-11}, corresponding to a standard deviation of 5.3 kHz. The system is also assembled in a more compact and easy-to-use configuration ( Plug&Play), showing comparable performance with previously published work. The real portability of this technology is proved by shipping the system to a collaborating laboratory, showing unchanged performance after the return.

  4. Sedimentary facies and petrophysical characteristics of cores from the lower Vicksburg gas reservoirs, McAllen Ranch field, Hidalgo County, Texas

    SciTech Connect

    Langford, R.P.; Maguregui, J. ); Howard, W.E.; Hall, J.D. )

    1990-09-01

    As part of an effort funded by the Gas Research Institute, the Department of Energy, and the State of Texas, and with the cooperation of Shell Oil Co., sandstones in the Vicksburg S (Oligocene) reservoir were cored in the McAllen Ranch gas field in the A. A. McAllen B- 17 and B- 18 wells. Detailed correlation of the cores with petrophysical data illustrates the controls of deposition and diagenesis on reservoir quality. The cores were drilled using oil-based mud, and special care in handling minimized evaporation. Core-derived water saturations were compared with log-calculated water saturations. Special core analyses of cementation factor, saturation exponent, and relative permeability were performed. Thin-section petrography and X-ray diffraction were used to determine mineralogy. The cores consist of prodelta and delta-front facies. Permeability and porosity generally increase with increasing grain size and are greatest in 1 to 2 ft thick zones within massive and laminated beds in the uppermost delta front. Porous intervals increase in abundance upward within the delta-front sandstones. Permeability variation over two orders of magnitude within the reservoir sands corresponds to diagenetic facies within the core. High permeability occurs only within thin bands. Trough cross-stratified sandstone is commonly porous only near the tops of the foresets. Differences in the character of the microresistivity curve of the high-resolution dipmeter log correlate with differences in cementation and with different depositional facies within the cores. Comparison of microresistivity logs and cores allows extrapolation of facies and cement characteristics and resulting reservoir properties to uncored intervals with the objective of maximizing recovery of natural gas.

  5. AMBIENT TEMPERATURE AND DRIVING CYCLE EFFECTS FROM AN AUTOMOBILE POWERED BY LIQUIFIED PETROLEUM GAS

    EPA Science Inventory

    This paper describes an emissions study of a 1991 Chevrolet Lumina, powered by liquefied petroleum gas. he study was designed to obtain emissions information to predict how liquid petroleum gas usage impacts ambient air quality and air toxics concentrations. he study was also des...

  6. Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture - Part A: Methodology and reference cases

    NASA Astrophysics Data System (ADS)

    Campanari, Stefano; Mastropasqua, Luca; Gazzani, Matteo; Chiesa, Paolo; Romano, Matteo C.

    2016-08-01

    Driven by the search for the highest theoretical efficiency, in the latest years several studies investigated the integration of high temperature fuel cells in natural gas fired power plants, where fuel cells are integrated with simple or modified Brayton cycles and/or with additional bottoming cycles, and CO2 can be separated via chemical or physical separation, oxy-combustion and cryogenic methods. Focusing on Solid Oxide Fuel Cells (SOFC) and following a comprehensive review and analysis of possible plant configurations, this work investigates their theoretical potential efficiency and proposes two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs integrated with a steam turbine or gas turbine cycle. The SOFC works at atmospheric or pressurized conditions and the resulting power plant exceeds 78% LHV efficiency without CO2 capture (as discussed in part A of the work) and 70% LHV efficiency with substantial CO2 capture (part B). The power plants are simulated at the 100 MW scale with a complete set of realistic assumptions about fuel cell (FC) performance, plant components and auxiliaries, presenting detailed energy and material balances together with a second law analysis.

  7. Development of a dynamic simulator for a natural gas combined cycle (NGCC) power plant with post-combustion carbon capture

    SciTech Connect

    Liese, E.; Zitney, S.

    2012-01-01

    The AVESTAR Center located at the U.S. Department of Energy’s National Energy Technology Laboratory and West Virginia University is a world-class research and training environment dedicated to using dynamic process simulation as a tool for advancing the safe, efficient and reliable operation of clean energy plants with CO{sub 2} capture. The AVESTAR Center was launched with a high-fidelity dynamic simulator for an Integrated Gasification Combined Cycle (IGCC) power plant with pre-combustion carbon capture. The IGCC dynamic simulator offers full-scope Operator Training Simulator (OTS) Human Machine Interface (HMI) graphics for realistic, real-time control room operation and is integrated with a 3D virtual Immersive Training Simulator (ITS), thus allowing joint control room and field operator training. The IGCC OTS/ITS solution combines a “gasification with CO{sub 2} capture” process simulator with a “combined cycle” power simulator into a single high-performance dynamic simulation framework. This presentation will describe progress on the development of a natural gas combined cycle (NGCC) dynamic simulator based on the syngas-fired combined cycle portion of AVESTAR’s IGCC dynamic simulator. The 574 MW gross NGCC power plant design consisting of two advanced F-class gas turbines, two heat recovery steam generators (HRSGs), and a steam turbine in a multi-shaft 2x2x1 configuration will be reviewed. Plans for integrating a post-combustion carbon capture system will also be discussed.

  8. Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture - Part A: Methodology and reference cases

    NASA Astrophysics Data System (ADS)

    Campanari, Stefano; Mastropasqua, Luca; Gazzani, Matteo; Chiesa, Paolo; Romano, Matteo C.

    2016-08-01

    Driven by the search for the highest theoretical efficiency, in the latest years several studies investigated the integration of high temperature fuel cells in natural gas fired power plants, where fuel cells are integrated with simple or modified Brayton cycles and/or with additional bottoming cycles, and CO2 can be separated via chemical or physical separation, oxy-combustion and cryogenic methods. Focusing on Solid Oxide Fuel Cells (SOFC) and following a comprehensive review and analysis of possible plant configurations, this work investigates their theoretical potential efficiency and proposes two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs integrated with a steam turbine or gas turbine cycle. The SOFC works at atmospheric or pressurized conditions and the resulting power plant exceeds 78% LHV efficiency without CO2 capture (as discussed in part A of the work) and 70% LHV efficiency with substantial CO2 capture (part B). The power plants are simulated at the 100 MW scale with a complete set of realistic assumptions about fuel cell (FC) performance, plant components and auxiliaries, presenting detailed energy and material balances together with a second law analysis.

  9. Hybrid sulfur cycle operation for high-temperature gas-cooled reactors

    SciTech Connect

    Gorensek, Maximilian B

    2015-02-17

    A hybrid sulfur (HyS) cycle process for the production of hydrogen is provided. The process uses a proton exchange membrane (PEM) SO.sub.2-depolarized electrolyzer (SDE) for the low-temperature, electrochemical reaction step and a bayonet reactor for the high-temperature decomposition step The process can be operated at lower temperature and pressure ranges while still providing an overall energy efficient cycle process.

  10. Successful field evaluation of the efficiency of a gas gravity drainage process by applying recent developments in Sponge coring technique in a major oil field

    SciTech Connect

    Durandeau, M.; El-Emam, M.; Anis, A.H.; Fanti, G.

    1995-11-01

    This paper describes the application and integration of new technologies and recent developments in Sponge coring and presents the methodology used to carry out successfully the various phases of well designed Sponge coring project, including the coring phase, the on-site measurements and the full evaluation of the Sponge core samples. A field case is presented where a Sponge coring project was accomplished to obtain accurate fluids distribution and evaluate the gas gravity drainage efficiency in one of the Arab D sub-reservoirs of a major oil field offshore Abu Dhabi. A Sponge coring technology team was created to optimize the methodology used during Sponge coring an minimize the uncertainties which persisted on some of the previous operations. The effectiveness of the technique is discussed, with comparison to open hole logs and SCAL data. Realistic petrophysical parameters were obtained from non-invaded, native-state core samples. The effective oil saturation obtained from the Sponge core analysis results showed that the gravity segregation mechanism has been very active and efficient to recover the oil in the reservoir.

  11. Emissions tradeoffs among alternative marine fuels: total fuel cycle analysis of residual oil, marine gas oil, and marine diesel oil.

    PubMed

    Corbett, James J; Winebrake, James J

    2008-04-01

    Worldwide concerns about sulfur oxide (SOx) emissions from ships are motivating the replacement of marine residual oil (RO) with cleaner, lower-sulfur fuels, such as marine gas oil (MGO) and marine diesel oil (MDO). Vessel operators can use MGO and MDO directly or blended with RO to achieve environmental and economic objectives. Although expected to be much cleaner in terms of criteria pollutants, these fuels require additional energy in the upstream stages of the fuel cycle (i.e., fuel processing and refining), and thus raise questions about the net impacts on greenhouse gas emissions (primarily carbon dioxide [CO2]) because of production and use. This paper applies the Total Energy and Environmental Analysis for Marine Systems (TEAMS) model to conduct a total fuel cycle analysis of RO, MGO, MDO, and associated blends for a typical container ship. MGO and MDO blends achieve significant (70-85%) SOx emissions reductions compared with RO across a range of fuel quality and refining efficiency assumptions. We estimate CO2 increases of less than 1% using best estimates of fuel quality and refinery efficiency parameters and demonstrate how these results vary based on parameter assumptions. Our analysis suggests that product refining efficiency influences the CO2 tradeoff more than differences in the physical and energy parameters of the alternative fuels, suggesting that modest increases in CO2 could be offset by efficiency improvements at some refineries. Our results help resolve conflicting estimates of greenhouse gas tradeoffs associated with fuel switching and other emissions control policies. PMID:18422040

  12. Design, construction, and operation of a life-cycle test system for the evaluation of flue gas cleanup processes

    SciTech Connect

    Pennline, H.W.; Yeh, James T.; Hoffman, J.S.; Longton, E.J.; Vore, P.A.; Resnik, K.P.; Gromicko, F.N.

    1995-12-01

    The Pittsburgh Energy Technology Center of the US Department of Energy has designed, constructed, and operated a Life-Cycle Test Systems (LCTS) that will be used primarily for the investigation of dry, regenerable sorbent flue gas cleanup processes. Sorbent continuously cycles from an absorber reactor where the pollutants are removed from the flue gas, to a regenerator reactor where the activity of the spent sorbent is restored and a usable by-product stream of gas is produced. The LCTS will initially be used to evaluate the Moving-Bed Copper Oxide Process by determining the effects of various process parameters on SO{sub 2} and NO{sub x} removals. The purpose of this paper is to document the design rationale and details, the reactor/component/instrument installation, and the initial performance of the system. Although the Moving-Bed Copper Oxide Process will be investigated initially, the design of the LCTS evolved to make the system a multipurpose, versatile research facility. Thus, the unit can be used to investigate various other processes for pollution abatement of SO{sub 2}, NO{sub x}, particulates, air toxics, and/or other pollutants.

  13. POWER CYCLE AND STRESS ANALYSES FOR HIGH TEMPERATURE GAS-COOLED REACTOR

    SciTech Connect

    Oh, Chang H; Davis, Cliff; Hawkes, Brian D; Sherman, Steven R

    2007-05-01

    The Department of Energy and the Idaho National Laboratory are developing a Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art nuclear technology. The purpose of the demonstration is two fold 1) efficient low cost energy generation and 2) hydrogen production. Although a next generation plant could be developed as a single-purpose facility, early designs are expected to be dual-purpose. While hydrogen production and advanced energy cycles are still in its early stages of development, research towards coupling a high temperature reactor, electrical generation and hydrogen production is under way. Many aspects of the NGNP must be researched and developed in order to make recommendations on the final design of the plant. Parameters such as working conditions, cycle components, working fluids, and power conversion unit configurations must be understood. Three configurations of the power conversion unit were demonstrated in this study. A three-shaft design with three turbines and four compressors, a combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated cycle with three stages of reheat were investigated. An intermediate heat transport loop for transporting process heat to a High Temperature Steam Electrolysis (HTSE) hydrogen production plant was used. Helium, CO2, and a 80% nitrogen, 20% helium mixture (by weight) were studied to determine the best working fluid in terms cycle efficiency and development cost. In each of these configurations the relative component size were estimated for the different working fluids. The relative size of the turbomachinery was measured by comparing the power input/output of the component. For heat exchangers the volume was computed and compared. Parametric studies away from the baseline values of the three-shaft and combined cycles were performed to determine the effect of varying conditions in the cycle. This gives some insight into the sensitivity of these cycles to

  14. Performance assessment and optimization of an irreversible nano-scale Stirling engine cycle operating with Maxwell-Boltzmann gas

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mohammad H.; Ahmadi, Mohammad-Ali; Pourfayaz, Fathollah

    2015-09-01

    Developing new technologies like nano-technology improves the performance of the energy industries. Consequently, emerging new groups of thermal cycles in nano-scale can revolutionize the energy systems' future. This paper presents a thermo-dynamical study of a nano-scale irreversible Stirling engine cycle with the aim of optimizing the performance of the Stirling engine cycle. In the Stirling engine cycle the working fluid is an Ideal Maxwell-Boltzmann gas. Moreover, two different strategies are proposed for a multi-objective optimization issue, and the outcomes of each strategy are evaluated separately. The first strategy is proposed to maximize the ecological coefficient of performance (ECOP), the dimensionless ecological function (ecf) and the dimensionless thermo-economic objective function ( F . Furthermore, the second strategy is suggested to maximize the thermal efficiency ( η), the dimensionless ecological function (ecf) and the dimensionless thermo-economic objective function ( F). All the strategies in the present work are executed via a multi-objective evolutionary algorithms based on NSGA∥ method. Finally, to achieve the final answer in each strategy, three well-known decision makers are executed. Lastly, deviations of the outcomes gained in each strategy and each decision maker are evaluated separately.

  15. Greenhouse gas reductions through enhanced use of residues in the life cycle of Malaysian palm oil derived biodiesel.

    PubMed

    Hansen, Sune Balle; Olsen, Stig Irving; Ujang, Zaini

    2012-01-01

    This study identifies the potential greenhouse gas (GHG) reductions, which can be achieved by optimizing the use of residues in the life cycle of palm oil derived biodiesel. This is done through compilation of data on existing and prospective treatment technologies as well as practical experiments on methane potentials from empty fruit bunches. Methane capture from the anaerobic digestion of palm oil mill effluent was found to result in the highest GHG reductions. Among the solid residues, energy extraction from shells was found to constitute the biggest GHG savings per ton of residue, whereas energy extraction from empty fruit bunches was found to be the most significant in the biodiesel production life cycle. All the studied waste treatment technologies performed significantly better than the conventional practices and with dedicated efforts of optimized use in the palm oil industry, the production of palm oil derived biodiesel can be almost carbon neutral. PMID:22137753

  16. Problems of the high-cycle fatigue of the materials intended for the parts of modern gas-turbine engines and power plants

    NASA Astrophysics Data System (ADS)

    Petukhov, A. N.

    2010-10-01

    The problems related to the determination of the life of the structural materials applied for important parts in gas-turbine engines and power plants from the results of high-cycle fatigue tests are discussed. Methods for increasing the reliability of the high-cycle fatigue characteristics and the factors affecting the operational reliability are considered.

  17. Core Level Spectroscopy and Tautomerism of Key Biomolecules in the Gas Phase

    NASA Astrophysics Data System (ADS)

    Feyer, V.; Plekan, O.; Richter, R.; Prince, K. C.; Coreno, M.; Giuliano, B. M.; Evangelisti, L.; Melandri, S.; Caminati, W.; Trofimov, A. B.; Zaytseva, I. L.; Moskovskaya, T. E.; Gromov, E. V.; Schirmer, J.

    2010-06-01

    The nucleobases cytosine, thymine and uracil are pyrimidine derivatives. They pair with their complementary purines, guanine and adenine, through hydrogen bonding to form DNA and RNA chains. The tautomeric forms of DNA bases are capable of unusual base pairing like thymine-guanine and cytosine-adenine and create mutations, which are the precursors of some molecular-based diseases. Low energy spectroscopies such as microwave, laser and infrared techniques are commonly used as methods to investigate the conformatonal and tautomeric equilibria of biomolecules, while the high energy technique of x-ray photoemission spectroscopy (XPS) has yielded a smaller amount of significant structural information about biomolecules in the gas phase. In the present studies we successfully apply XPS to the study of five nucleic acid base tautomers, as well as the prototypical system 2-hydroxypyridimine and the related molecules S-methyl-2-thiouracil and 2-thiouracil in the vapor phase. XPS is a quantitative technique, allowing the experimental determination of the populations of keto and enol tautomers at known equilibrium temperatures: it is difficult to obtain this information otherwise. The effect of different substituents on stability of tautomers has been revealed. Quantum chemistry calculations have been carried out in order to obtain information about the structure, relative stability and difference in populations of the tautomers and conformers under study.

  18. Life Cycle Greenhouse Gas Emissions of Trough and Tower Concentrating Solar Power Electricity Generation: Systematic Review and Harmonization

    SciTech Connect

    Burkhardt, J. J.; Heath, G.; Cohen, E.

    2012-04-01

    In reviewing life cycle assessment (LCA) literature of utility-scale concentrating solar power (CSP) systems, this analysis focuses on reducing variability and clarifying the central tendency of published estimates of life cycle greenhouse gas (GHG) emissions through a meta-analytical process called harmonization. From 125 references reviewed, 10 produced 36 independent GHG emissions estimates passing screens for quality and relevance: 19 for parabolic trough (trough) technology and 17 for power tower (tower) technology. The interquartile range (IQR) of published estimates for troughs and towers were 83 and 20 grams of carbon dioxide equivalent per kilowatt-hour (g CO2-eq/kWh),1 respectively; median estimates were 26 and 38 g CO2-eq/kWh for trough and tower, respectively. Two levels of harmonization were applied. Light harmonization reduced variability in published estimates by using consistent values for key parameters pertaining to plant design and performance. The IQR and median were reduced by 87% and 17%, respectively, for troughs. For towers, the IQR and median decreased by 33% and 38%, respectively. Next, five trough LCAs reporting detailed life cycle inventories were identified. The variability and central tendency of their estimates are reduced by 91% and 81%, respectively, after light harmonization. By harmonizing these five estimates to consistent values for global warming intensities of materials and expanding system boundaries to consistently include electricity and auxiliary natural gas combustion, variability is reduced by an additional 32% while central tendency increases by 8%. These harmonized values provide useful starting points for policy makers in evaluating life cycle GHG emissions from CSP projects without the requirement to conduct a full LCA for each new project.

  19. Selecting the process arrangement for preparing the gas turbine working fluid for an integrated gasification combined-cycle power plant

    NASA Astrophysics Data System (ADS)

    Ryzhkov, A. F.; Gordeev, S. I.; Bogatova, T. F.

    2015-11-01

    Introduction of a combined-cycle technology based on fuel gasification integrated in the process cycle (commonly known as integrated gasification combined cycle technology) is among avenues of development activities aimed at achieving more efficient operation of coal-fired power units at thermal power plants. The introduction of this technology is presently facing the following difficulties: IGCC installations are characterized by high capital intensity, low energy efficiency, and insufficient reliability and availability indicators. It was revealed from an analysis of literature sources that these drawbacks are typical for the gas turbine working fluid preparation system, the main component of which is a gasification plant. Different methods for improving the gasification plant chemical efficiency were compared, including blast air high-temperature heating, use of industrial oxygen, and a combination of these two methods implying limited use of oxygen and moderate heating of blast air. Calculated investigations aimed at estimating the influence of methods for achieving more efficient air gasification are carried out taking as an example the gasifier produced by the Mitsubishi Heavy Industries (MHI) with a thermal capacity of 500 MW. The investigation procedure was verified against the known experimental data. Modes have been determined in which the use of high-temperature heating of blast air for gasification and cycle air upstream of the gas turbine combustion chamber makes it possible to increase the working fluid preparation system efficiency to a level exceeding the efficiency of the oxygen process performed according to the Shell technology. For the gasification plant's configuration and the GTU working fluid preparation system be selected on a well-grounded basis, this work should be supplemented with technical-economic calculations.

  20. High cycle fatigue behavior of Incoloy 800H in a simulated high-temperature gas-cooled reactor helium environment

    SciTech Connect

    Soo, P.; Sabatini, R.L.; Epel, L.G.; Hare, J.R. Sr.

    1980-01-01

    The current study was an attempt to evaluate the high cycle fatigue strength of Incoloy 800H in a High-Temperature Gas-Cooled Reactor helium environment containing significant quantities of moisture. As-heat-treated and thermally-aged materials were tested to determine the effects of long term corrosion in the helium test gas. Results from in-helium tests were compared to those from a standard air environment. It was found that the mechanisms of fatigue failure were very complex and involved recovery/recrystallization of the surface ground layer on the specimens, sensitization, hardness changes, oxide scale integrity, and oxidation at the tips of propagation cracks. For certain situations a corrosion-fatigue process seems to be controlling. However, for the helium environment studied, there was usually no aging or test condition for which air gave a higher fatigue strength.

  1. Noble Gas and Mineralogical Tracers of Interplanetary Dust Particles and Impact Debris in a Central Pacific Sediment Core

    NASA Astrophysics Data System (ADS)

    Darrah, T. H.; Poreda, R. J.

    2005-12-01

    Thirty-five deep ocean sediment samples from the Central Pacific sediment core LL-44 GPC-3 were examined for their noble gas composition and mineralogy. The samples spanned from 30 to 71 Ma in age, including the Cretaceous/Tertiary (K/T), Paleocene/Eocene (P/E), and Eocene/Oligocene (E/O) boundaries. From each bulk sediment sample, magnetic grains (5-200 μg/g; 1-20 μm diameter) were isolated and analyzed. Noble gas measurements determined the helium and neon isotopic compositions and the abundance of extra-terrestrial (ET) noble gases for the bulk and magnetic fractions. 3He/4He ratios of 3.1x10-4 and 20Ne/22Ne ratios of 9.96-12.62 are consistent with the SEP (solar energetic particle) signature seen in both zero-age magnetic grains (Z-MAG) from the central Pacific sediments and stratospheric interplanetary dust particles (IDPs). The isolated magnetic fraction typically consisted of less than 1% of the bulk sample while accounting for 3 to 10% of the bulk sediment 3He with a maximum of 40% at K/T boundary. The magnetic isolates revealed no significant differences of 3He/4He, 20Ne/22Ne, or (3He/20Ne)solar from the bulk GPC-3 sediments or Z-MAG grains. No temporal variation in He or Ne or anomalous gas signatures associated with the boundaries present within this time interval was observed. Scanning electron microscope analysis was utilized to determine the mineralogy of the magnetic isolates in an effort to distinguish between the continuous flux of interplanetary dust particles and the flux associated with major impact events. This information may also assist in determining the carrier phase of ET noble gases. Anomalously high Ni, Mg, Al, and Cr compositions combined with low or nonexistent abundances of titanium can distinguish extraterrestrial spinel grains from terrestrial spinel. The SEM analysis revealed stark contrasts in composition and morphology in the samples associated with the boundaries included in this study. A survey of ``background'' samples

  2. Performance assessment of an irreversible nano Brayton cycle operating with Maxwell-Boltzmann gas

    NASA Astrophysics Data System (ADS)

    Açıkkalp, Emin; Caner, Necmettin

    2015-05-01

    In the last decades, nano-technology has been developed very fast. According to this, nano-cycle thermodynamics should improve with a similar rate. In this paper, a nano-scale irreversible Brayton cycle working with helium is evaluated for different thermodynamic criteria. These are maximum work output, ecological function, ecological coefficient of performance, exergetic performance criteria and energy efficiency. Thermodynamic analysis was performed for these criteria and results were submitted numerically. In addition, these criteria are compared with each other and the most convenient methods for the optimum conditions are suggested.

  3. Including impacts of particulate emissions on marine ecosystems in life cycle assessment: the case of offshore oil and gas production.

    PubMed

    Veltman, Karin; Huijbregts, Mark A J; Rye, Henrik; Hertwich, Edgar G

    2011-10-01

    Life cycle assessment is increasingly used to assess the environmental performance of fossil energy systems. Two of the dominant emissions of offshore oil and gas production to the marine environment are the discharge of produced water and drilling waste. Although environmental impacts of produced water are predominantly due to chemical stressors, a major concern regarding drilling waste discharge is the potential physical impact due to particles. At present, impact indicators for particulate emissions are not yet available in life cycle assessment. Here, we develop characterization factors for 2 distinct impacts of particulate emissions: an increased turbidity zone in the water column and physical burial of benthic communities. The characterization factor for turbidity is developed analogous to characterization factors for toxic impacts, and ranges from 1.4 PAF (potentially affected fraction) · m(3) /d/kg(p) (kilogram particulate) to 7.0 x 10³ [corrected] for drilling mud particles discharged from the rig. The characterization factor for burial describes the volume of sediment that is impacted by particle deposition on the seafloor and equals 2.0 × 10(-1) PAF · m(3) /d/kg(p) for cutting particles. This characterization factor is quantified on the basis of initial deposition layer characteristics, such as height and surface area, the initial benthic response, and the recovery rate. We assessed the relevance of including particulate emissions in an impact assessment of offshore oil and gas production. Accordingly, the total impact on the water column and on the sediment was quantified based on emission data of produced water and drilling waste for all oil and gas fields on the Norwegian continental shelf in 2008. Our results show that cutting particles contribute substantially to the total impact of offshore oil and gas production on marine sediments, with a relative contribution of 55% and 31% on the regional and global scale, respectively. In contrast, the

  4. Studying the Outflow-Core Interaction with ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Arce, H. G.; Mardones, D.; Dunham, M. M.; Garay, G.; Noriega-Crespo, A.; Corder, S.; Offner, S.

    2015-12-01

    We present preliminary analysis of ALMA cycle 1 12m array 12CO /13CO /C18O data of the HH 46/47 molecular outflow. 13CO and C18O trace relatively denser outflow material than 12CO and allow us to trace the outflow to lower velocities than what it possible using only the 12CO emission. Interestingly, the cavity wall of the red lobe can be seen at velocity as low as 0.2 km/s. Using C18O, we are now able to estimate the optical depth of 13CO, and then use the corrected 13CO emission to further and better correct the 12CO emission and estimate the mass, momentum, and kinetic energy of the outflow. Moreover, C18O reveals a flattened rotational structure at the center, likely to be a rotational envelope infalling onto an inner Keplerian disk.

  5. Comparison between Borehole Geophysical Observations and Sedimentary Facies for Three Long Cores Recovered from the Ulleung Basin, Korea: Insights into the Distribution of Gas Hydrate

    NASA Astrophysics Data System (ADS)

    Lim, H.; Lee, S.; Bahk, J.

    2010-12-01

    In late 2007, a logging-while-drilling (LWD) operation was performed as part of gas hydrate study at five sites in the Ulleung Basin, east of Korea. Of those five sites, long sediment cores were also recovered at three sites (UBGH-4, 9, and 10), allowing us to compare borehole observation results with characteristics of sediment in the cores. In this study, we analyzed the resistivity log and resistivity image recorded using GVR-SONIC-ADN MD200 to see if there exists any meaningful relationship between the borehole data and sedimentary facies described in the cores. The presence of fracture zones and their orientation were also estimated from the resistivity images. Site UBGH-4 shows little evidence of disintegrated mud (DITM), an important source of gas hydrate. No notable changes could be seen in the resistivity log or image at this site. On the other hand, at Site UBGH-9, several peaks in resistivity values and numerous fractures are found at 70-150 mbsf. This depth interval matches with DITM found in the cores. At UBGH-10, DITM facies are found below 175 mbsf, but unfortunately due to error in resistivity and image data, it is unclear as to whether this depth coincides with the location of abundant gas hydrate or not. In summary, the argument that massive gas hydrates generally occur in the mud sections with ample fractures could not be thoroughly tested except for Site UBGH-9 where the two features do correlate.

  6. Flammable gas tank safety program: Data requirements for core sample analysis developed through the Data Quality Objectives (DQO) process. Revision 1

    SciTech Connect

    McDuffie, N.G.; LeClair, M.D.

    1995-04-28

    This document represents the application of the Data Quality Objectives (DQO) process to the Flammable Gas Tank Safety Issue at the Hanford Site. The product of this effort is a list of data required from tank core sample analysis to support resolution of this issue.

  7. Life cycle greenhouse gas emissions of sugar cane renewable jet fuel.

    PubMed

    Moreira, Marcelo; Gurgel, Angelo C; Seabra, Joaquim E A

    2014-12-16

    This study evaluated the life cycle GHG emissions of a renewable jet fuel produced from sugar cane in Brazil under a consequential approach. The analysis included the direct and indirect emissions associated with sugar cane production and fuel processing, distribution, and use for a projected 2020 scenario. The CA-GREET model was used as the basic analytical tool, while Land Use Change (LUC) emissions were estimated employing the GTAP-BIO-ADV and AEZ-EF models. Feedstock production and LUC impacts were evaluated as the main sources of emissions, respectively estimated as 14.6 and 12 g CO2eq/MJ of biofuel in the base case. However, the renewable jet fuel would strongly benefit from bagasse and trash-based cogeneration, which would enable a net life cycle emission of 8.5 g CO2eq/MJ of biofuel in the base case, whereas Monte Carlo results indicate 21 ± 11 g CO2eq/MJ. Besides the major influence of the electricity surplus, the sensitivity analysis showed that the cropland-pasture yield elasticity and the choice of the land use factor employed to sugar cane are relevant parameters for the biofuel life cycle performance. Uncertainties about these estimations exist, especially because the study relies on projected performances, and further studies about LUC are also needed to improve the knowledge about their contribution to the renewable jet fuel life cycle. PMID:25419647

  8. Life Cycle Greenhouse Gas Emissions from Concentrating Solar Power (Fact Sheet)

    SciTech Connect

    Not Available

    2012-11-01

    The National Renewable Energy Laboratory (NREL) recently led the Life Cycle Assessment (LCA) Harmonization Project, a study that makes great strides in clarifying inconsistent and conflicting GHG emission estimates in the published literature while providing more precise estimates of GHG emissions from utility-scale CSP systems.

  9. Hybrid Co3O4/SnO2 Core-Shell Nanospheres as Real-Time Rapid-Response Sensors for Ammonia Gas.

    PubMed

    Wang, Lili; Lou, Zheng; Zhang, Rui; Zhou, Tingting; Deng, Jianan; Zhang, Tong

    2016-03-16

    Novel hybrid Co3O4/SnO2 core-shell nanospheres have been effectively realized by a one-step hydrothermal, template-free preparation method. Our strategy involves a simple fabrication scheme that entails the coating of natural cross-link agents followed by electrostatic interaction between the positive charges of Sn and Co ions and the negative charge of glutamic acid. The core-shell architecture enables novel flexibility of gas sensor surfaces compared to commonly used bulk materials. The highly efficient charge transfer and unique structure are key to ensuring the availability of high response and rapid-response speed. It demonstrates how hybrid core-shell nanospheres can be used as an advance function material to fabricate electrical sensing devices that may be useful as gas sensors. PMID:26943006

  10. Metal-organic framework-immobilized polyhedral metal nanocrystals: reduction at solid-gas interface, metal segregation, core-shell structure, and high catalytic activity.

    PubMed

    Aijaz, Arshad; Akita, Tomoki; Tsumori, Nobuko; Xu, Qiang

    2013-11-01

    For the first time, this work presents surfactant-free monometallic and bimetallic polyhedral metal nanocrystals (MNCs) immobilized to a metal-organic framework (MIL-101) by CO-directed reduction of metal precursors at the solid-gas interface. With this novel method, Pt cubes and Pd tetrahedra were formed by CO preferential bindings on their (100) and (111) facets, respectively. PtPd bimetallic nanocrystals showed metal segregation, leading to Pd-rich core and Pt-rich shell. Core-shell Pt@Pd nanocrystals were immobilized to MIL-101 by seed-mediated two-step reduction, representing the first example of core-shell MNCs formed using only gas-phase reducing agents. These MOF-supported MNCs exhibited high catalytic activities for CO oxidation. PMID:24138338

  11. Method and apparatus utilizing ionizing and microwave radiation for saturation determination of water, oil and a gas in a core sample

    DOEpatents

    Maerefat, Nicida L.; Parmeswar, Ravi; Brinkmeyer, Alan D.; Honarpour, Mehdi

    1994-01-01

    A system for determining the relative permeabilities of gas, water and oil in a core sample has a microwave emitter/detector subsystem and an X-ray emitter/detector subsystem. A core holder positions the core sample between microwave absorbers which prevent diffracted microwaves from reaching a microwave detector where they would reduce the signal-to-noise ratio of the microwave measurements. The microwave emitter/detector subsystem and the X-ray emitter/detector subsystem each have linear calibration characteristics, allowing one subsystem to be calibrated with respect to the other subsystem. The dynamic range of microwave measurements is extended through the use of adjustable attenuators. This also facilitates the use of core samples with wide diameters. The stratification characteristics of the fluids may be observed with a windowed cell separator at the outlet of the core sample. The condensation of heavy hydrocarbon gas and the dynamic characteristics of the fluids are observed with a sight glass at the outlet of the core sample.

  12. Method and apparatus utilizing ionizing and microwave radiation for saturation determination of water, oil and a gas in a core sample

    DOEpatents

    Maerefat, N.L.; Parmeswar, R.; Brinkmeyer, A.D.; Honarpour, M.

    1994-08-23

    A system is described for determining the relative permeabilities of gas, water and oil in a core sample has a microwave emitter/detector subsystem and an X-ray emitter/detector subsystem. A core holder positions the core sample between microwave absorbers which prevent diffracted microwaves from reaching a microwave detector where they would reduce the signal-to-noise ratio of the microwave measurements. The microwave emitter/detector subsystem and the X-ray emitter/detector subsystem each have linear calibration characteristics, allowing one subsystem to be calibrated with respect to the other subsystem. The dynamic range of microwave measurements is extended through the use of adjustable attenuators. This also facilitates the use of core samples with wide diameters. The stratification characteristics of the fluids may be observed with a windowed cell separator at the outlet of the core sample. The condensation of heavy hydrocarbon gas and the dynamic characteristics of the fluids are observed with a sight glass at the outlet of the core sample. 11 figs.

  13. Hg Isotope Ratios of a Sediment Core from Plastic Lake, Ontario: Implications for Hg Cycle in Aquatic Environment

    NASA Astrophysics Data System (ADS)

    Xie, Q.; Dillon, P.; Evans, D.; Lu, S.

    2004-12-01

    Hg isotope ratios in a sediment core obtained in Plastic Lake, Ontario, Canada, have been measured by coupling a gold trap with an MC-ICP-MS. The core is about 30 cm in depth and corresponds to a time period of about 250 years, based on 210Pb dating. The samples were combusted at high temperature and the Hg collected onto a gold trap. The gold trap was subsequently heated to release Hg directly into the MC-ICP-MS. An in-house sample introduction system was employed to extend Hg signal duration in order to obtain high precision in isotope ratio measurement. The instrumental mass bias was corrected using Tl introduced simultaneously via an Aridus membrane desolvation nebulizer. Based on long term measurement of a NIST-2225 elemental Hg standard (over 120 measurements since Oct. 2002), the external reproducibility ranges from 45 ppm for 201Hg/202Hg to 100 ppm for 199Hg/202Hg (2 sigma relative standard error). Hg in the sediments shows an increase in light isotope enrichment at about 10 cm depth. The total Hg also displays an increase at the same depth. The depth corresponds to approximately the 1920s, a time period when there was a major increase in coal-burning power generation. Limited Hg isotope data for other terrestrial samples appears to indicate that Hg bound to organic carbon is enriched in light isotopes relative to elemental Hg. For example, the DOLT-3, a dogfish liver standard reference material with half of its Hg as MeHg, has the lightest Hg isotope composition among measured terrestrial samples. It is not clear at this stage whether the increase in total Hg and light Hg isotope enrichment in recent years represent a change in methylation rate of the lake, or an increase in atmospheric deposition of Hg combined with a change in source. Discussions based on available Hg isotope data of terrestrial samples together with other chemical data for the lake will be presented.

  14. On high suppression of NO x and CO emissions in gas-turbine plants with combined gas-and-steam cycles

    NASA Astrophysics Data System (ADS)

    Ivanov, A. A.; Ermakov, A. N.; Shlyakhov, R. A.

    2010-12-01

    In this work are given results of analyzing processes of production of nitrogen oxides (NO x ) and afterburning of CO when firing natural gas at combined-cycle gas-turbine plants. It is shown that for suppressing emissions of the said microcomponents it is necessary to lower temperature in hot local zones of the flame in which NOx is formed, and, in so doing, to avoid chilling of cold flame zones that prevents afterburning of CO. The required lowering of the combustion temperature can be provided by combustion of mixtures of methane with steam, with high mixing uniformity that ensures the same and optimum fraction of the steam "ballast" in each microvolume of the flame. In addition to chilling, the steam ballast makes it possible to maintain a fairly high concentration of hydroxil radicals in the flame zone as well, and this provides high burning out of fuel and reduction in carbon monoxide emissions (active steam ballast). Due to this fact the fraction of steam when firing its mixtures with methane in a gas-turbine plant can be increased up to the weight ratio 4: 1. In this case, the concentrations of NO x and CO in emissions can be reduced to ultra-low values (less than 3 ppm).

  15. Planting increases the abundance and structure complexity of soil core functional genes relevant to carbon and nitrogen cycling

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Liang, Yuting; Jiang, Yuji; Yang, Yunfeng; Xue, Kai; Xiong, Jinbo; Zhou, Jizhong; Sun, Bo

    2015-09-01

    Plants have an important impact on soil microbial communities and their functions. However, how plants determine the microbial composition and network interactions is still poorly understood. During a four-year field experiment, we investigated the functional gene composition of three types of soils (Phaeozem, Cambisols and Acrisol) under maize planting and bare fallow regimes located in cold temperate, warm temperate and subtropical regions, respectively. The core genes were identified using high-throughput functional gene microarray (GeoChip 3.0), and functional molecular ecological networks (fMENs) were subsequently developed with the random matrix theory (RMT)-based conceptual framework. Our results demonstrated that planting significantly (P < 0.05) increased the gene alpha-diversity in terms of richness and Shannon - Simpson’s indexes for all three types of soils and 83.5% of microbial alpha-diversity can be explained by the plant factor. Moreover, planting had significant impacts on the microbial community structure and the network interactions of the microbial communities. The calculated network complexity was higher under maize planting than under bare fallow regimes. The increase of the functional genes led to an increase in both soil respiration and nitrification potential with maize planting, indicating that changes in the soil microbial communities and network interactions influenced ecological functioning.

  16. Planting increases the abundance and structure complexity of soil core functional genes relevant to carbon and nitrogen cycling

    PubMed Central

    Wang, Feng; Liang, Yuting; Jiang, Yuji; Yang, Yunfeng; Xue, Kai; Xiong, Jinbo; Zhou, Jizhong; Sun, Bo

    2015-01-01

    Plants have an important impact on soil microbial communities and their functions. However, how plants determine the microbial composition and network interactions is still poorly understood. During a four-year field experiment, we investigated the functional gene composition of three types of soils (Phaeozem, Cambisols and Acrisol) under maize planting and bare fallow regimes located in cold temperate, warm temperate and subtropical regions, respectively. The core genes were identified using high-throughput functional gene microarray (GeoChip 3.0), and functional molecular ecological networks (fMENs) were subsequently developed with the random matrix theory (RMT)-based conceptual framework. Our results demonstrated that planting significantly (P < 0.05) increased the gene alpha-diversity in terms of richness and Shannon – Simpson’s indexes for all three types of soils and 83.5% of microbial alpha-diversity can be explained by the plant factor. Moreover, planting had significant impacts on the microbial community structure and the network interactions of the microbial communities. The calculated network complexity was higher under maize planting than under bare fallow regimes. The increase of the functional genes led to an increase in both soil respiration and nitrification potential with maize planting, indicating that changes in the soil microbial communities and network interactions influenced ecological functioning. PMID:26396042

  17. Energy Conversion Alternatives Study (ECAS), Westinghouse phase 1. Volume 6: Closed-cycle gas turbine systems. [energy conversion efficiency in electric power plants

    NASA Technical Reports Server (NTRS)

    Amos, D. J.; Fentress, W. K.; Stahl, W. F.

    1976-01-01

    Both recuperated and bottomed closed cycle gas turbine systems in electric power plants were studied. All systems used a pressurizing gas turbine coupled with a pressurized furnace to heat the helium for the closed cycle gas turbine. Steam and organic vapors are used as Rankine bottoming fluids. Although plant efficiencies of over 40% are calculated for some plants, the resultant cost of electricity was found to be 8.75 mills/MJ (31.5 mills/kWh). These plants do not appear practical for coal or oil fired plants.

  18. Particle image velocimetry measurements in a representative gas-cooled prismatic reactor core model for the estimation of bypass flow

    NASA Astrophysics Data System (ADS)

    Conder, Thomas E.

    Core bypass flow is considered one of the largest contributors to uncertainty in fuel temperature within the Modular High Temperature Gas-cooled Reactor (MHTGR). It refers to the coolant that navigates through the interstitial regions between the graphite fuel blocks instead of traveling through the designated coolant channels. These flows are of concern because they reduce the desired flow rates in the coolant channels, and thereby have significant influence on the maximum fuel element and coolant exit temperatures. Thus, accurate prediction of the bypass flow is important because it directly impacts core temperature, influencing the life and efficiency of the reactor. An experiment was conducted at Idaho National Laboratory to quantify the flow in the coolant channels in relation to the interstitial gaps between fuel blocks in a representative MHTGR core. Particle Image Velocimetry (PIV) was used to measure the flow fields within a simplified model, which comprised of a stacked junction of six partial fuel blocks with nine coolant tubes, separated by a 6mm gap width. The model had three sections: The upper plenum, upper block, and lower block. Model components were fabricated from clear, fused quartz where optical access was needed for the PIV measurements. Measurements were taken in three streamwise locations: in the upper plenum and in the midsection of the large and small fuel blocks. A laser light sheet was oriented parallel to the flow, while velocity fields were measured at millimeter intervals across the width of the model, totaling 3,276 PIV measurement locations. Inlet conditions were varied to incorporate laminar, transition, and turbulent flows in the coolant channels---all which produced laminar flow in the gap and non-uniform, turbulent flow in the upper plenum. The images were analyzed to create vector maps, and the data was exported for processing and compilation. The bypass flow was estimated by calculating the flow rates through the coolant

  19. Asymmetric supercapacitors based on carbon nanotubes@NiO ultrathin nanosheets core-shell composites and MOF-derived porous carbon polyhedrons with super-long cycle life

    NASA Astrophysics Data System (ADS)

    Yi, Huan; Wang, Huanwen; Jing, Yuting; Peng, Tianquan; Wang, Xuefeng

    2015-07-01

    Aqueous electrolyte based asymmetric supercapacitors (ASCs) has recently attracted increasing interest by virtue of their operation voltage and high ionic conductivity. Herein, we developed a novel ASC based on carbon nanotubes@nickel oxide nanosheets (CNT@NiO) core-shell composites as positive electrode and porous carbon polyhedrons (PCPs) as negative electrode in aqueous KOH solution as electrolyte. The CNT@NiO core-shell hybrids were prepared through a facile chemical bath deposition method followed by thermal annealing, while PCPs were obtained by direct carbonization of Zn-based metal-organic frameworks (MOFs). Owing to their unique microstructures, outstanding electrochemical properties have been achieved in three-electrode configuration, e.g., 996 F g-1 at 1 A g-1, 500 at 20 A g-1 for the CNT@NiO electrode within 0-0.5 V window, and 245 F g-1 at 1 A g-1 for the PCPs electrode within -1-0 V window. Resulting from these merits, the as-fabricated CNT@NiO//PCPs ASC exhibits maximum energy density of 25.4 Wh kg-1 at a power density of 400 W kg-1 and even remains 9.8 Wh kg-1 at 16,000 W kg-1 (a full charge-discharge within 4.4 s) in the wide voltage region of 0-1.6 V. More importantly, the CNT@NiO//PCPs asymmetric supercapacitor shows ultralong cycling stability, with 93% capacitance retention after 10,000 cycles.

  20. Generation IV nuclear energy system initiative. Large GFR core subassemblydesign for the Gas-Cooled Fast Reactor.

    SciTech Connect

    Hoffman, E. A.; Kulak, R. F.; Therios, I. U.; Wei, T. Y. C.

    2006-07-31

    Gas-cooled fast reactor (GFR) designs are being developed to meet Gen IV goals of sustainability, economics, safety and reliability, and proliferation resistance and physical protection as part of an International Generation IV Nuclear Energy System Research Initiative effort. Different organizations are involved in the development of a variety of GFR design concepts. The current analysis has focused on the evaluation of low-pressure drop, pin-core designs with favorable passive cooling properties. Initial evaluation of the passive cooling safety case for the GFR during depressurized decay heat removal accidents with concurrent loss of electric power have resulted in requirements for a reduction of core power density to the 100 w/cc level and a low core pressure drop of 0.5 bars. Additional design constraints and the implementation of their constraints are evaluated in this study to enhance and passive cooling properties of the reactor. Passive cooling is made easier by a flat radial distribution of the decay heat. One goal of this study was to evaluate the radial power distribution and determine to what extent it can be flattened, since the decay heat is nearly proportional to the fission power at shutdown. In line with this investigation of the radial power profile, an assessment was also made of the control rod configuration. The layout provided a large number of control rod locations with a fixed area provided for control rods. The number of control rods was consistent with other fast reactor designs. The adequacy of the available control rod locations was evaluated. Future studies will be needed to optimize the control rod designs and evaluate the shutdown system. The case for low pressure drop core can be improved by the minimization of pressure drop sources such as the number of required fuel spacers in the subassembly design and by the details of the fuel pin design. The fuel pin design is determined by a number of neutronic, thermal-hydraulic (gas dynamics

  1. Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture - Part B: Applications

    NASA Astrophysics Data System (ADS)

    Campanari, Stefano; Mastropasqua, Luca; Gazzani, Matteo; Chiesa, Paolo; Romano, Matteo C.

    2016-09-01

    An important advantage of solid oxide fuel cells (SOFC) as future systems for large scale power generation is the possibility of being efficiently integrated with processes for CO2 capture. Focusing on natural gas power generation, Part A of this work assessed the performances of advanced pressurised and atmospheric plant configurations (SOFC + GT and SOFC + ST, with fuel cell integration within a gas turbine or a steam turbine cycle) without CO2 separation. This Part B paper investigates such kind of power cycles when applied to CO2 capture, proposing two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs with internal reforming and low temperature CO2 separation process. The power plants are simulated at the 100 MW scale with a set of realistic assumptions about FC performances, main components and auxiliaries, and show the capability of exceeding 70% LHV efficiency with high CO2 capture (above 80%) and a low specific primary energy consumption for the CO2 avoided (1.1-2.4 MJ kg-1). Detailed results are presented in terms of energy and material balances, and a sensitivity analysis of plant performance is developed vs. FC voltage and fuel utilisation to investigate possible long-term improvements. Options for further improvement of the CO2 capture efficiency are also addressed.

  2. Orbital Circularization of a Planet Accreting Disk Gas: The Formation of Distant Jupiters in Circular Orbits Based on a Core Accretion Model

    NASA Astrophysics Data System (ADS)

    Kikuchi, Akihiro; Higuchi, Arika; Ida, Shigeru

    2014-12-01

    Recently, gas giant planets in nearly circular orbits with large semimajor axes (a ~ 30-1000 AU) have been detected by direct imaging. We have investigated orbital evolution in a formation scenario for such planets, based on a core accretion model. (1) Icy cores accrete from planetesimals at <~ 30 AU, (2) they are scattered outward by an emerging nearby gas giant to acquire highly eccentric orbits, and (3) their orbits are circularized through the accretion of disk gas in outer regions, where they spend most of their time. We analytically derived equations to describe the orbital circularization through gas accretion. Numerical integrations of these equations show that the eccentricity decreases by a factor of more than 5 while the planetary mass increases by a factor of 10. Because runaway gas accretion increases planetary mass by ~10-300, the orbits are sufficiently circularized. On the other hand, a is reduced at most only by a factor of two, leaving the planets in the outer regions. If the relative velocity damping by shock is considered, the circularization slows down, but is still efficient enough. Therefore, this scenario potentially accounts for the formation of observed distant jupiters in nearly circular orbits. If the apocenter distances of the scattered cores are larger than the disk sizes, their a shrink to a quarter of the disk sizes; the a-distribution of distant giants could reflect the outer edges of the disks in a similar way that those of hot jupiters may reflect inner edges.

  3. Orbital circularization of a planet accreting disk gas: the formation of distant jupiters in circular orbits based on a core accretion model

    SciTech Connect

    Kikuchi, Akihiro; Higuchi, Arika; Ida, Shigeru E-mail: higuchia@geo.titech.ac.jp

    2014-12-10

    Recently, gas giant planets in nearly circular orbits with large semimajor axes (a ∼ 30-1000 AU) have been detected by direct imaging. We have investigated orbital evolution in a formation scenario for such planets, based on a core accretion model. (1) Icy cores accrete from planetesimals at ≲ 30 AU, (2) they are scattered outward by an emerging nearby gas giant to acquire highly eccentric orbits, and (3) their orbits are circularized through the accretion of disk gas in outer regions, where they spend most of their time. We analytically derived equations to describe the orbital circularization through gas accretion. Numerical integrations of these equations show that the eccentricity decreases by a factor of more than 5 while the planetary mass increases by a factor of 10. Because runaway gas accretion increases planetary mass by ∼10-300, the orbits are sufficiently circularized. On the other hand, a is reduced at most only by a factor of two, leaving the planets in the outer regions. If the relative velocity damping by shock is considered, the circularization slows down, but is still efficient enough. Therefore, this scenario potentially accounts for the formation of observed distant jupiters in nearly circular orbits. If the apocenter distances of the scattered cores are larger than the disk sizes, their a shrink to a quarter of the disk sizes; the a-distribution of distant giants could reflect the outer edges of the disks in a similar way that those of hot jupiters may reflect inner edges.

  4. Biochar alters manure's effect on nitrogen cycling and greenhouse gas emissions in a calcareous soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Few multiyear field studies have examined the impacts of a one-time biochar application on net N mineralization and greenhouse gas emissions in an irrigated, calcareous soil; yet such applications are hypothesized as a means of sequestering atmospheric CO2 and improving soil quality. We fall-applie...

  5. The integrated approach to a gas turbine topping cycle cogeneration system

    SciTech Connect

    Leibowitz, H.; Tabb, E.

    1984-06-01

    Under Gas Research Institute (GRI) sponsorship, a new gas turbine cogeneration system was developed by Mechanical Technology, Inc., (MTI) for installation at a General Motors plant in early 1985. Specific emphasis was placed on system integration. A single, prime-reliable drive train and a single control center replace a wide assortment of nonintegrated, free-standing power drives and control centers. On-line availability, installation costs, and overall user acceptance are improved. The cogeneration set produces 3 MW /SUB e/ and 8,860 kg/hr (19,500 lb/hr) of 1825 kPa (250 psig) saturated steam using an Allison 501-KH gas turbine and a natural circulation waste heat boiler. The system is designed for multifuel operation using either natural gas or distillate oil. A steam injection feature is employed to increase output to 4 MW /SUB e/ when process steam demand diminishes. The system is prepackaged, skid mounted, and delivered in four modules: one each for the machinery, duct burner, waste heat boiler, and controls.

  6. Managing the nitrogen cycle to reduce greenhouse gas emissions from crop production and biofuel expansion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The United States Renewable Fuel Standards (RFS2) established under the Energy Independence and Security Act of 2007 requires greenhouse gas (GHG) emissions to be lower for biofuels relative to fossil fuel combustion. However, there is an extensive debate in the literature about the potential to red...

  7. Thermohydraulics in a high-temperature gas-cooled reactor primary loop during early phases of unrestricted core-heatup accidents

    SciTech Connect

    Kroeger, P.G.; Colman, J.; Hsu, C.J.

    1983-01-01

    In High Temperature Gas Cooled Reactor (HTGR) siting considerations, the Unrestricted Core Heatup Accidents (UCHA) are considered as accidents of highest consequence, corresponding to core meltdown accidents in light water reactors. Initiation of such accidents can be, for instance, due to station blackout, resulting in scram and loss of all main loop forced circulation, with none of the core auxiliary cooling system loops being started. The result is a slow but continuing core heatup, extending over days. During the initial phases of such UCHA scenarios, the primary loop remains pressurized, with the system pressure slowly increasing until the relief valve setpoint is reached. The major objectives of the work described here were to determine times to depressurization as well as approximate loop component temperatures up to depressurization.

  8. Life-cycle fossil energy consumption and greenhouse gas emissions of bioderived chemicals and their conventional counterparts.

    PubMed

    Adom, Felix; Dunn, Jennifer B; Han, Jeongwoo; Sather, Norm

    2014-12-16

    Biomass-derived chemical products may offer reduced environmental impacts compared to their fossil-derived counterparts and could improve profit margins at biorefineries when coproduced with higher-volume, lower-profit margin biofuels. It is important to assess on a life-cycle basis the energy and environmental impacts of these bioproducts as compared to conventional, fossil-derived products. We undertook a life-cycle analysis of eight bioproducts produced from either algal-derived glycerol or corn stover-derived sugars. Selected on the basis of technology readiness and market potential, the bioproducts are propylene glycol, 1,3-propanediol, 3-hydroxypropionic acid, acrylic acid, polyethylene, succinic acid, isobutanol, and 1,4-butanediol. We developed process simulations to obtain energy and material flows in the production of each bioproduct and examined sensitivity of these flows to process design assumptions. Conversion process data for fossil-derived products were based on the literature. Conversion process data were combined with upstream parameters in the Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model to generate life-cycle greenhouse gas (GHG) emissions and fossil energy consumption (FEC) for each bioproduct and its corresponding petroleum-derived product. The bioproducts uniformly offer GHG emissions reductions compared to their fossil counterparts ranging from 39 to 86% on a cradle-to-grave basis. Similarly, FEC was lower for bioproducts than for conventional products. PMID:25380298

  9. Biofuels via Fast Pyrolysis of Perennial Grasses: A Life Cycle Evaluation of Energy Consumption and Greenhouse Gas Emissions.

    PubMed

    Zaimes, George G; Soratana, Kullapa; Harden, Cheyenne L; Landis, Amy E; Khanna, Vikas

    2015-08-18

    A well-to-wheel (WTW) life cycle assessment (LCA) model is developed to evaluate the environmental profile of producing liquid transportation fuels via fast pyrolysis of perennial grasses: switchgrass and miscanthus. The framework established in this study consists of (1) an agricultural model used to determine biomass growth rates, agrochemical application rates, and other key parameters in the production of miscanthus and switchgrass biofeedstock; (2) an ASPEN model utilized to simulate thermochemical conversion via fast pyrolysis and catalytic upgrading of bio-oil to renewable transportation fuel. Monte Carlo analysis is performed to determine statistical bounds for key sustainability and performance measures including life cycle greenhouse gas (GHG) emissions and Energy Return on Investment (EROI). The results of this work reveal that the EROI and GHG emissions (gCO2e/MJ-fuel) for fast pyrolysis derived fuels range from 1.52 to 2.56 and 22.5 to 61.0 respectively, over the host of scenarios evaluated. Further analysis reveals that the energetic performance and GHG reduction potential of fast pyrolysis-derived fuels are highly sensitive to the choice of coproduct scenario and LCA allocation scheme, and in select cases can change the life cycle carbon balance from meeting to exceeding the renewable fuel standard emissions reduction threshold for cellulosic biofuels. PMID:26196154

  10. Redox cycle stability of mixed oxides used for hydrogen generation in the cyclic water gas shift process

    SciTech Connect

    Datta, Pradyot

    2013-10-15

    Graphical abstract: - Highlights: • Fe{sub 2}O{sub 3} modified with CaO, SiO{sub 2} and Al{sub 2}O{sub 3} was studied in cyclic water gas shift reactor. • For the first time stability of such oxides were tested for 100 redox cycles. • Optimally added oxides significantly improved the activity and the stability of Fe{sub 2}O{sub 3}. • Increased stability was attributed to the impediment of neck formation. - Abstract: Repeated cycles of the reduction of Fe{sub 3}O{sub 4} with reductive gas, e.g. hydrogen and subsequent oxidation of the reduced iron material with water vapor can be harnessed as a process for the production of pure hydrogen. The redox behavior of iron oxide modified with various amounts of SiO{sub 2}, CaO and Al{sub 2}O{sub 3} was investigated in the present study. The total amount of the additional metal oxides was always below 15 wt%. The samples were prepared by co-precipitation using urea hydrolysis method. The influence of various metal oxides on the hydrogen production capacity and the material stability was studied in detail in terms of temperature-programmed reduction (TPR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. Furthermore, the activity and the stability of the samples were tested in repeated reduction with diluted H{sub 2} and re-oxidation cycles with H{sub 2}O. The results indicate that combination of several oxides as promoter increases the stability of the iron oxide material by mitigating the sintering process. The positive influence of the oxides in stabilizing the iron oxide material is attributed to the impediment of neck formation responsible for sintering.

  11. Development and application of the EPIC model for carbon cycle, greenhouse-gas mitigation, and biofuel studies

    SciTech Connect

    Izaurralde, Roberto C.; Mcgill, William B.; Williams, J.R.

    2012-06-01

    This chapter provides a comprehensive review of the EPIC model in relation to carbon cycle, greenhouse-gas mitigation, and biofuel applications. From its original capabilities and purpose (i.e., quantify the impacts or erosion on soil productivity), the EPIC model has evolved into a comprehensive terrestrial ecosystem model for simulating with more or less process-level detail many ecosystem processes such as weather, hydrology, plant growth and development, carbon cycle (including erosion), nutrient cycling, greenhouse-gas emissions, and the most complete set of manipulations that can be implemented on a parcel of land (e.g. tillage, harvest, fertilization, irrigation, drainage, liming, burning, pesticide application). The chapter also provides details and examples of the latest efforts in model development such as the coupled carbon-nitrogen model, a microbial denitrification model with feedback to the carbon decomposition model, updates on calculation of ecosystem carbon balances, and carbon emissions from fossil fuels. The chapter has included examples of applications of the EPIC model in soil carbon sequestration, net ecosystem carbon balance, and biofuel studies. Finally, the chapter provides the reader with an update on upcoming improvements in EPIC such as the additions of modules for simulating biochar amendments, sorption of soluble C in subsoil horizons, nitrification including the release of N2O, and the formation and consumption of methane in soils. Completion of these model development activities will render an EPIC model with one of the most complete representation of biogeochemical processes and capable of simulating the dynamic feedback of soils to climate and management in terms not only of transient processes (e.g., soil water content, heterotrophic respiration, N2O emissions) but also of fundamental soil properties (e.g. soil depth, soil organic matter, soil bulk density, water limits).

  12. Performance calculations and research direction for a water enhanced regenerative gas turbine cycle

    SciTech Connect

    Rogers, L.H.; Archer, D.H.

    1993-09-01

    A cycle has been conceived that combines compressor cooling, humidification, and regenerative air heating with the added enhancement of direct injection of water into the air flow. In this cycle it is proposed that a fine mist of water be injected into the compressor air stream and a spray or film of water into the regenerator air stream. Water injection into the compressor air flow realizes several benefits: it cools the air flow, reducing the power required for compression and increasing the potential for exhaust heat recovery; it adds mass to the air stream, increasing the power produced by expansion; and it reduces the amount of cooling bleed air required by increasing the specific heat and decreasing the temperature of the cooling air stream. The greatest benefit would be derived from spraying a fine mist of water directly into the existing air flow into or before the compressor so that cooling and compression would occur simultaneously. This may be accomplished by entraining the water droplets in the inlet air flow or by introducing the water in stages during compression. An alternative and less technically challenging approach is to extract the air stream to a saturation chamber and then reintroduce the air stream into the compressor. This approach is not as desirable because it would increase the equipment cost and add a significant pressure drop penalty. The second use of water in this cycle is in water-assisted regeneration.

  13. Effect of different agronomic management practices on greenhouse gas emissions and nutrient cycling in a long-term field trial

    NASA Astrophysics Data System (ADS)

    Koal, Philipp; Schilling, Rolf; Gerl, Georg; Pritsch, Karin; Munch, Jean Charles

    2015-04-01

    In order to achieve a reduction of greenhouse gas emissions, modern agronomic management practices need to be established. Therefore, to assess the effect of different farming practices on greenhouse gas emissions, reliable data are required. The experiment covers and compares two main aspects of agricultural management for a better implementation of sustainable land use. The focus lies on the determination and interpretation of greenhouse gas emissions, however, regarding in each case a different agricultural management system, namely an organic farming system and an integrated farming system where the effect of diverse tillage systems and fertilisation practices are observed. In addition, with analysis of the alterable biological, physical and chemical soil properties a link between the impact of different management systems on greenhouse gas emissions and the observed cycle of matter in the soil, especially the nitrogen and carbon cycle, will be enabled. Measurements have been carried out on long-term field trials at the Research Farm Scheyern located in a Tertiary hilly landscape approximately 40 km north of Munich (South Germany). The long-term field trials of the organic and integrated farming system were started in 1992. Since then parcels of land (each around 0.2-0.4 ha) with a particular interior plot set-up have been conducted with the same crop rotation, tillage and fertilisation practice referring to organic and integrated farming management. Thus, the management impacts on the soil of more than 20 years are being examined. Fluxes of CH4, N2O and CO2 have been monitored since 2007 for the integrated farming system trial and since 2012 for the organic farming system trial using an automated system which consists of chambers (0.4 m2 area) with a motor-driven lid, an automated gas sampling unit, an on-line gas chromatographic analysis system, and a control and data logging unit. Precipitation and temperature data have been observed for each experimental

  14. Integrated gasification combined cycle and steam injection gas turbine powered by biomass joint-venture evaluation

    SciTech Connect

    Sterzinger, G J

    1994-05-01

    This report analyzes the economic and environmental potential of biomass integrated gasifier/gas turbine technology including its market applications. The mature technology promises to produce electricity at $55--60/MWh and to be competitive for market applications conservatively estimated at 2000 MW. The report reviews the competitiveness of the technology of a stand-alone, mature basis and finds it to be substantial and recognized by DOE, EPRI, and the World Bank Global Environmental Facility.

  15. Fluid and chemical cycling at Bush Hill: Implications for gas- and hydrate-rich environments

    NASA Astrophysics Data System (ADS)

    Tryon, Michael D.; Brown, Kevin M.

    2004-12-01

    The results of a deployment of aqueous flux meters at the Bush Hill hydrate mound show that persistent hydrologic instability is a primary feature of the globally abundant gas- and hydrate-rich cold seep environment. Seven flux meters were deployed for 14 weeks in the area of the Bush Hill hydrate mound. Instruments were deployed on microbial mats, bivalves, adjacent to the surface hydrate mound, and a site without visible fauna. Flow rates were observed to range from downflow of 0.01 mm/day to upflow of >15 mm/day. Temporal variability and a major hydrological event were observed to occur on all instruments. There is evidence that this event was related to a gas expulsion episode. The two instruments which exhibited downflow during the event were near surface hydrates and bubbling vents. Nearby instruments recorded a rapid increase in flow rates at the time of the event with a subsequent decrease in rates to the previous background values. Two instruments showed significant output of seawater-like fluids, while the others output typical methane seep-type pore fluids. These results at a passive margin site, along with our previously published convergent margin results at gas-rich northeast Pacific cold seeps (Hydrate Ridge, Eel River margin), illustrate the hydrologic complexity of these environments. We now propose that these and our earlier results are characteristic of seafloor environments which have abundant free gas and hydrates. These mechanisms have major consequences for the near-surface geochemical and microbial environment and for the way we interpret measurements made in these areas.

  16. Preliminary analysis of compound systems based on high temperature fuel cell, gas turbine and Organic Rankine Cycle

    NASA Astrophysics Data System (ADS)

    Sánchez, D.; Muñoz de Escalona, J. M.; Monje, B.; Chacartegui, R.; Sánchez, T.

    This article presents a novel proposal for complex hybrid systems comprising high temperature fuel cells and thermal engines. In this case, the system is composed by a molten carbonate fuel cell with cascaded hot air turbine and Organic Rankine Cycle (ORC), a layout that is based on subsequent waste heat recovery for additional power production. The work will credit that it is possible to achieve 60% efficiency even if the fuel cell operates at atmospheric pressure. The first part of the analysis focuses on selecting the working fluid of the Organic Rankine Cycle. After a thermodynamic optimisation, toluene turns out to be the most efficient fluid in terms of cycle performance. However, it is also detected that the performance of the heat recovery vapour generator is equally important, what makes R245fa be the most interesting fluid due to its balanced thermal and HRVG efficiencies that yield the highest global bottoming cycle efficiency. When this fluid is employed in the compound system, conservative operating conditions permit achieving 60% global system efficiency, therefore accomplishing the initial objective set up in the work. A simultaneous optimisation of gas turbine (pressure ratio) and ORC (live vapour pressure) is then presented, to check if the previous results are improved or if the fluid of choice must be replaced. Eventually, even if system performance improves for some fluids, it is concluded that (i) R245fa is the most efficient fluid