Science.gov

Sample records for fuel temperature peaking

  1. Determination of the bias in LOFT fuel peak cladding temperature data from the blowdown phase of large-break LOCA experiments

    SciTech Connect

    Berta, V.T.; Hanson, R.G.; Johnsen, G.W.; Schultz, R.R.

    1993-05-01

    Data from the Loss-of-Fluid Test (LOFT) Program help quantify the margin of safety inherent in pressurized water reactors during postulated loss-of-coolant accidents (LOCAs). As early as 1979, questions arose concerning the accuracy of LOFT fuel rod cladding temperature data during several large-break LOCA experiments. This report analyzes how well externally-mounted fuel rod cladding thermocouples in LOFT accurately reflected actual cladding surface temperature during large-break LOCA experiments. In particular, the validity of the apparent core-wide fuel rod cladding quench exhibited during blowdown in LOFT Experiments L2-2 and L2-3 is studied. Also addressed is the question of whether the externally-mounted thermocouples might have influenced cladding temperature. The analysis makes use of data and information from several sources, including later, similar LOFT Experiments in which fuel centerline temperature measurements were made, experiments in other facilities, and results from a detailed FRAP-T6 model of the LOFT fuel rod. The analysis shows that there can be a significant difference (referred to as bias) between the surface-mounted thermocouple reading and the actual cladding temperature, and that the magnitude of this bias depends on the rate of heat transfer between the fuel rod cladding and coolant. The results of the analysis demonstrate clearly that a core-wide cladding quench did occur in Experiments L2-2 and L2-3. Further, it is shown that, in terms of peak cladding temperature recording during LOFT large-break LOCA experiments, the mean bias is 11.4 {plus_minus} 16.2K (20.5 {plus_minus} 29.2{degrees} F). The best-estimate value of peak cladding temperature for LOFT LP-02-6 is 1,104.8 K. The best-estimate peak cladding temperature for LOFT LP-LB-1 is 1284.0 K.

  2. FEMAXI-V benchmarking study on peak temperature and fission gas release prediction of PWR rod fuel

    SciTech Connect

    Suwardi; Dewayatna, W.; Briyatmoko, B.

    2012-06-06

    The present paper reports a study of FEMAXI-V code and related report on code benchmarking. Capabilities of the FEMAXI-V code to predict the thermal and fission gas release have been tested on MOX fuels in LWRs which has been done in SCK{center_dot}CEN and Belgonucleaire by using PRIMO MOX rod BD8 irradiation experiment after V Sobolev as reported O. J. Ott. Base irradiation in the BR3 reactor, the BD8 rod was transported to CEA-Saclay for irradiation in the OSIRIS reactor (ramp power excursion). The irradiation device used for the PRIMO ramps was the ISABELLE 1 loop, installed on a movable structure of the core periphery. The power variations were obtained by inwards/backwards movements of the loop in the core water. The preconditioning phase for rod BD8 occurred at a peak power level of 189 W/cm with a hold time of 27 hours. The subsequent power excursion rate amounted to 77 W/ (cm.min), reaching a terminal peak power level of 395 W/cm that lasted for 20 hours.

  3. Measurements of fuel pin/water hole worths and power peaking, void coefficients, and temperature coefficients for 4. 81 wt% enriched UO[sub 2] fuel rods

    SciTech Connect

    Harris, D.R.; Rohr, R.R.; Angelo, P.L.; Patrou, N.T.; Buckwheat, K.W.; Hayes, D.K.

    1990-01-01

    The Rensselaer Polytechnic Institute reactor critical facility is currently the only facility in North America providing critical measurement data in support of the light water reactor electric power industry. The reactor is fueled by 4.81 wt% [sup 235]U enriched UO[sub 2] high-density pellets in stainless steel clad fuel rods at the present time, although experiments with other fuels are being analyzed. The fuel pins are supported by inexpensive stainless steel lattice plates in a large open water tank. Three sets of lattice plates have been fabricated for fuel pins in square array with pitches 0.585, 0.613, and 0.640 in. (1.486, 0.613, and 1.656 cm, respectively) to provide a relevant range of water-to-fuel volume ratios. The measurements reported here are for the first of these, a relatively tight lattice of considerable interest for reactor physics methods for advanced fuels and reactors.

  4. On the off-stoichiometric peaking of adiabatic flame temperature

    SciTech Connect

    Law, C.K.; Lu, T.F.; Makino, A.

    2006-06-15

    The characteristic rich shifting of the maximum adiabatic flame temperature from the stoichiometric value for mixtures of hydrocarbon and air is demonstrated to be caused by product dissociation and hence reduced amount of heat release. Since the extent of dissociation is greater on the lean side as a result of the stoichiometry of dissociated products, the peaking occurs on the rich side. The specific heat per unit mass of the mixture is shown to increase monotonically with increasing fuel concentration, and as such tends to shift the peak toward the lean side. It is further shown that this is the cause for the lean shifting of the adiabatic flame temperature of oxidizer-enriched mixtures of N{sub m}H{sub n} and F{sub 2} and of NH{sub 3} and O{sub 2}, with various amounts of inert dilution, even though their maximum heat release still peaks on the rich side. (author)

  5. Linearity between temperature peak and bioenergy CO2 emission rates

    NASA Astrophysics Data System (ADS)

    Cherubini, Francesco; Gasser, Thomas; Bright, Ryan M.; Ciais, Philippe; Strømman, Anders H.

    2014-11-01

    Many future energy and emission scenarios envisage an increase of bioenergy in the global primary energy mix. In most climate impact assessment models and policies, bioenergy systems are assumed to be carbon neutral, thus ignoring the time lag between CO2 emissions from biomass combustion and CO2 uptake by vegetation. Here, we show that the temperature peak caused by CO2 emissions from bioenergy is proportional to the maximum rate at which emissions occur and is almost insensitive to cumulative emissions. Whereas the carbon-climate response (CCR; ref. ) to fossil fuel emissions is approximately constant, the CCR to bioenergy emissions depends on time, biomass turnover times, and emission scenarios. The linearity between temperature peak and bioenergy CO2 emission rates resembles the characteristic of the temperature response to short-lived climate forcers. As for the latter, the timing of CO2 emissions from bioenergy matters. Under the international agreement to limit global warming to 2 °C by 2100, early emissions from bioenergy thus have smaller contributions on the targeted temperature than emissions postponed later into the future, especially when bioenergy is sourced from biomass with medium (50-60 years) or long turnover times (100 years).

  6. Back-Up/ Peak Shaving Fuel Cell System

    SciTech Connect

    Staudt, Rhonda L.

    2008-05-28

    This Final Report covers the work executed by Plug Power from 8/11/03 – 10/31/07 statement of work for Topic 2: advancing the state of the art of fuel cell technology with the development of a new generation of commercially viable, stationary, Back-up/Peak-Shaving fuel cell systems, the GenCore II. The Program cost was $7.2 M with the Department of Energy share being $3.6M and Plug Power’s share being $3.6 M. The Program started in August of 2003 and was scheduled to end in January of 2006. The actual program end date was October of 2007. A no cost extension was grated. The Department of Energy barriers addressed as part of this program are: Technical Barriers for Distributed Generation Systems: o Durability o Power Electronics o Start up time Technical Barriers for Fuel Cell Components: o Stack Material and Manufacturing Cost o Durability o Thermal and water management Background The next generation GenCore backup fuel cell system to be designed, developed and tested by Plug Power under the program is the first, mass-manufacturable design implementation of Plug Power’s GenCore architected platform targeted for battery and small generator replacement applications in the telecommunications, broadband and UPS markets. The next generation GenCore will be a standalone, H2 in-DC-out system. In designing the next generation GenCore specifically for the telecommunications market, Plug Power is teaming with BellSouth Telecommunications, Inc., a leading industry end user. The final next generation GenCore system is expected to represent a market-entry, mass-manufacturable and economically viable design. The technology will incorporate: • A cost-reduced, polymer electrolyte membrane (PEM) fuel cell stack tailored to hydrogen fuel use • An advanced electrical energy storage system • A modular, scalable power conditioning system tailored to market requirements • A scaled-down, cost-reduced balance of plant (BOP) • Network Equipment Building Standards (NEBS), UL

  7. Cryogenic precision digital temperature control with peaked frequency response

    NASA Astrophysics Data System (ADS)

    Li, Jie; Lockhart, James M.; Boretsky, Peter

    2004-05-01

    A high precision temperature control system capable of maintaining the temperature of superconducting quantum interference devices (SQUIDs) constant to within 1.0 μK root-mean square over a narrow frequency band was designed and built for use with the superconducting readout system of the Gravity Probe B experiment. The system utilizes an analog ac temperature bridge with a digital proportional-integral control loop which incorporates a peaking filter. A disturbance attenuation factor of 86 or greater over the required frequency band was demonstrated in system tests with the cryogenic hardware, allowing the SQUID system to achieve the required stability. The control system was robust against variations in the thermal characteristics of the cryogenic hardware.

  8. Fuel Temperature Coefficient of Reactivity

    SciTech Connect

    Loewe, W.E.

    2001-07-31

    A method for measuring the fuel temperature coefficient of reactivity in a heterogeneous nuclear reactor is presented. The method, which is used during normal operation, requires that calibrated control rods be oscillated in a special way at a high reactor power level. The value of the fuel temperature coefficient of reactivity is found from the measured flux responses to these oscillations. Application of the method in a Savannah River reactor charged with natural uranium is discussed.

  9. Inflight fuel tank temperature survey data

    NASA Technical Reports Server (NTRS)

    Pasion, A. J.

    1979-01-01

    Statistical summaries of the fuel and air temperature data for twelve different routes and for different aircraft models (B747, B707, DC-10 and DC-8), are given. The minimum fuel, total air and static air temperature expected for a 0.3% probability were summarized in table form. Minimum fuel temperature extremes agreed with calculated predictions and the minimum fuel temperature did not necessarily equal the minimum total air temperature even for extreme weather, long range flights.

  10. A wedged-peak-pulse design with medium fuel adiabat for indirect-drive fusion

    SciTech Connect

    Fan, Zhengfeng; Ren, Guoli; Liu, Bin; Wu, Junfeng; He, X. T.; Liu, Jie; Wang, L. F.; Ye, Wenhua

    2014-10-15

    In the present letter, we propose the design of a wedged-peak pulse at the late stage of indirect drive. Our simulations of one- and two-dimensional radiation hydrodynamics show that the wedged-peak-pulse design can raise the drive pressure and capsule implosion velocity without significantly raising the fuel adiabat. It can thus balance the energy requirement and hydrodynamic instability control at both ablator/fuel interface and hot-spot/fuel interface. This investigation has implication in the fusion ignition at current mega-joule laser facilities.

  11. Peak fire temperatures and effects on annual plants in the Mojave Desert

    USGS Publications Warehouse

    Brooks, M.L.

    2002-01-01

    Very little is known about the behavior and effects of fire in the Mojave Desert, because fire was historically uncommon. However, fire has become more frequent since the 1970s with increased dominance of the invasive annual grasses Bromus rubens and Schismus spp., and land managers are concerned about its ecological effect. In this paper, I describe patterns of peak fire temperature and their effect on annual plants in creosote bush scrub vegetation of the Mojave Desert. Temperatures were monitored among microhabitats and distances from the soil surface, and between spring and summer. Microhabitats ranged from high amounts of fuel beneath creosote bush (Larrea tridentata) canopies, to intermediate amounts at the canopy drip line, to low amounts in the interspaces between them. Distances from the soil surface were within the vertical range where most annual plant seeds occur (-2, 0, 5, and 10 cm). I also compare temperature patterns with postfire changes in soil properties and annual plant biomass and species richness to infer potential mechanisms by which fires affect annual plants. Peak fire temperatures were most affected by the microhabitat fuel gradient, and the effects of fire on annual plants varied among microhabitats. Beneath creosote bushes, lethal fire temperatures for annual plant seeds occurred above- and belowground, resulting in four postfire years of reduced annual plant biomass and species richness due most likely to seed mortality, especially of Bromus rubens and native forbs. At the canopy drip line, lethal fire temperatures occurred only aboveground, reducing annual plant biomass for 1 yr and species richness for 2 yr, and increasing biomass of Schismus sp., the alien forb Erodium cicutarium, and native annuals after 3 yr. Negligible changes were caused by fire in interspaces or between spring and summer. Fire effects models for creosote bush scrub vegetation must account for patterns of peak fire temperature along the shrub-intershrub gradient

  12. Peak-Seeking Optimization of Trim for Reduced Fuel Consumption: Architecture and Performance Predictions

    NASA Technical Reports Server (NTRS)

    Schaefer, Jacob; Brown, Nelson A.

    2013-01-01

    A peak-seeking control approach for real-time trim configuration optimization for reduced fuel consumption has been developed by researchers at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center to address the goals of the NASA Environmentally Responsible Aviation project to reduce fuel burn and emissions. The peak-seeking control approach is based on a steepest-descent algorithm using a time-varying Kalman filter to estimate the gradient of a performance function of fuel flow versus control surface positions. In real-time operation, deflections of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of an F/A-18 airplane (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) are controlled for optimization of fuel flow. This paper presents the design and integration of this peak-seeking controller on a modified NASA F/A-18 airplane with research flight control computers. A research flight was performed to collect data to build a realistic model of the performance function and characterize measurement noise. This model was then implemented into a nonlinear six-degree-of-freedom F/A-18 simulation along with the peak-seeking control algorithm. With the goal of eventual flight tests, the algorithm was first evaluated in the improved simulation environment. Results from the simulation predict good convergence on minimum fuel flow with a 2.5-percent reduction in fuel flow relative to the baseline trim of the aircraft.

  13. Peak-Seeking Optimization of Trim for Reduced Fuel Consumption: Architecture and Performance Predictions

    NASA Technical Reports Server (NTRS)

    Schaefer, Jacob; Brown, Nelson

    2013-01-01

    A peak-seeking control approach for real-time trim configuration optimization for reduced fuel consumption has been developed by researchers at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center to address the goals of the NASA Environmentally Responsible Aviation project to reduce fuel burn and emissions. The peak-seeking control approach is based on a steepest-descent algorithm using a time-varying Kalman filter to estimate the gradient of a performance function of fuel flow versus control surface positions. In real-time operation, deflections of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of an FA-18 airplane (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) are controlled for optimization of fuel flow. This presentation presents the design and integration of this peak-seeking controller on a modified NASA FA-18 airplane with research flight control computers. A research flight was performed to collect data to build a realistic model of the performance function and characterize measurement noise. This model was then implemented into a nonlinear six-degree-of-freedom FA-18 simulation along with the peak-seeking control algorithm. With the goal of eventual flight tests, the algorithm was first evaluated in the improved simulation environment. Results from the simulation predict good convergence on minimum fuel flow with a 2.5-percent reduction in fuel flow relative to the baseline trim of the aircraft.

  14. Sensitivity and System Response of Pin Power Peaking in VVER-1000 Fuel Assembly Using TSUNAMI-2D

    NASA Astrophysics Data System (ADS)

    Frybort, J.

    2014-04-01

    Pin power peaking in a VVER-1000 fuel assembly and its sensitivity and uncertainty was analyzed by TSUNAMI-2D code. Several types of fuel assemblies were considered. They differ in number and position of gadolinium fuel pins. The calculations were repeated for several fuel compositions obtained by fuel depletion calculation. The results are quantified sensitivity data, which can be used for enrichment profiling.

  15. EXTENDING SODIUM FAST REACTOR DRIVER FUEL USE TO HIGHER TEMPERATURES

    SciTech Connect

    Douglas L. Porter

    2011-02-01

    Calculations of potential sodium-cooled fast reactor fuel temperatures were performed to estimate the effects of increasing the outlet temperature of a given fast reactor design by increasing pin power, decreasing assembly flow, or increasing inlet temperature. Based upon experience in the U.S., both metal and mixed oxide (MOX) fuel types are discussed in terms of potential performance effects created by the increased operating temperatures. Assembly outlet temperatures of 600, 650 and 700 °C were used as goal temperatures. Fuel/cladding chemical interaction (FCCI) and fuel melting, as well as challenges to the mechanical integrity of the cladding material, were identified as the limiting phenomena. For example, starting with a recent 1000 MWth fast reactor design, raising the outlet temperature to 650 °C through pin power increase increased the MOX centerline temperature to more than 3300 °C and the metal fuel peak cladding temperature to more than 700 °C. These exceeded limitations to fuel performance; fuel melting was limiting for MOX and FCCI for metal fuel. Both could be alleviated by design ‘fixes’, such as using a barrier inside the cladding to minimize FCCI in the metal fuel, or using annular fuel in the case of MOX. Both would also require an advanced cladding material with improved stress rupture properties. While some of these are costly, the benefits of having a high-temperature reactor which can support hydrogen production, or other missions requiring high process heat may make the extra costs justified.

  16. Nuclear fuels for very high temperature applications

    SciTech Connect

    Lundberg, L.B.; Hobbins, R.R.

    1992-08-01

    The success of the development of nuclear thermal propulsion devices and thermionic space nuclear power generation systems depends on the successful utilization of nuclear fuel materials at temperatures in the range 2000 to 3500 K. Problems associated with the utilization of uranium bearing fuel materials at these very high temperatures while maintaining them in the solid state for the required operating times are addressed. The critical issues addressed include evaporation, melting, reactor neutron spectrum, high temperature chemical stability, fabrication, fission induced swelling, fission product release, high temperature creep, thermal shock resistance, and fuel density, both mass and fissile atom. Candidate fuel materials for this temperature range are based on UO{sub 2} or uranium carbides. Evaporation suppression, such as a sealed cladding, is required for either fuel base. Nuclear performance data needed for design are sparse for all candidate fuel forms in this temperature range, especially at the higher temperatures.

  17. Nuclear fuels for very high temperature applications

    SciTech Connect

    Lundberg, L.B.; Hobbins, R.R.

    1992-01-01

    The success of the development of nuclear thermal propulsion devices and thermionic space nuclear power generation systems depends on the successful utilization of nuclear fuel materials at temperatures in the range 2000 to 3500 K. Problems associated with the utilization of uranium bearing fuel materials at these very high temperatures while maintaining them in the solid state for the required operating times are addressed. The critical issues addressed include evaporation, melting, reactor neutron spectrum, high temperature chemical stability, fabrication, fission induced swelling, fission product release, high temperature creep, thermal shock resistance, and fuel density, both mass and fissile atom. Candidate fuel materials for this temperature range are based on UO{sub 2} or uranium carbides. Evaporation suppression, such as a sealed cladding, is required for either fuel base. Nuclear performance data needed for design are sparse for all candidate fuel forms in this temperature range, especially at the higher temperatures.

  18. Peak-Seeking Optimization of Trim for Reduced Fuel Consumption: Flight-test Results

    NASA Technical Reports Server (NTRS)

    Brown, Nelson Andrew; Schaefer, Jacob Robert

    2013-01-01

    A peak-seeking control algorithm for real-time trim optimization for reduced fuel consumption has been developed by researchers at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center to address the goals of the NASA Environmentally Responsible Aviation project to reduce fuel burn and emissions. The peak-seeking control algorithm is based on a steepest-descent algorithm using a time-varying Kalman filter to estimate the gradient of a performance function of fuel flow versus control surface positions. In real-time operation, deflections of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of an F/A-18 airplane (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) are used for optimization of fuel flow. Results from six research flights are presented herein. The optimization algorithm found a trim configuration that required approximately 3 percent less fuel flow than the baseline trim at the same flight condition. The algorithm consistently rediscovered the solution from several initial conditions. These results show that the algorithm has good performance in a relevant environment.

  19. Peak-Seeking Optimization of Trim for Reduced Fuel Consumption: Flight-Test Results

    NASA Technical Reports Server (NTRS)

    Brown, Nelson Andrew; Schaefer, Jacob Robert

    2013-01-01

    A peak-seeking control algorithm for real-time trim optimization for reduced fuel consumption has been developed by researchers at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center to address the goals of the NASA Environmentally Responsible Aviation project to reduce fuel burn and emissions. The peak-seeking control algorithm is based on a steepest-descent algorithm using a time-varying Kalman filter to estimate the gradient of a performance function of fuel flow versus control surface positions. In real-time operation, deflections of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of an F/A-18 airplane (McDonnell Douglas, now The Boeing Company, Chicago, Illinois) are used for optimization of fuel flow. Results from six research flights are presented herein. The optimization algorithm found a trim configuration that required approximately 3 percent less fuel flow than the baseline trim at the same flight condition. The algorithm consistently rediscovered the solution from several initial conditions. These results show that the algorithm has good performance in a relevant environment.

  20. A universal scaling behavior in magnetic resonance peak in high temperature superconductivity

    NASA Astrophysics Data System (ADS)

    Shin, Seung Joon; Salk, Sung-Ho Suck

    2015-08-01

    Eminent inelastic neutron scattering (INS) measurements of high temperature cuprates currently lacking theoretical interpretations are the observed temperature dependence of magnetic resonance peak and linear scaling relation between the resonance peak energy, Eres and the superconducting transition temperature, Tc. Using our slave-boson approach of the t-J Hamiltonian (Phys. Rev. 64, 052501 (2001)) for this study, we show that starting from the pseudogap temperature T∗, the magnetic resonance peak increases with decreasing temperature, revealing its inflection point at Tc and that spin pairing correlations are responsible for d-wave superconductivity. We find that there exists a universal linear scaling behavior of Eres/Tc = const., irrespective of the Heisenberg exchange coupling.

  1. Effective thermal conductivity method for predicting spent nuclear fuel cladding temperatures in a dry fill gas

    SciTech Connect

    Bahney, Robert

    1997-12-19

    This paper summarizes the development of a reliable methodology for the prediction of peak spent nuclear fuel cladding temperature within the waste disposal package. The effective thermal conductivity method replaces other older methodologies.

  2. The Fuel Accident Condition Simulator (FACS) furnace system for high temperature performance testing of VHTR fuel

    SciTech Connect

    Paul A. Demkowicz; David V. Laug; Dawn M. Scates; Edward L. Reber; Lyle G. Roybal; John B. Walter; Jason M. Harp; Robert N. Morris

    2012-10-01

    The AGR-1 irradiation of TRISO-coated particle fuel specimens was recently completed and represents the most successful such irradiation in US history, reaching peak burnups of greater than 19% FIMA with zero failures out of 300,000 particles. An extensive post-irradiation examination (PIE) campaign will be conducted on the AGR-1 fuel in order to characterize the irradiated fuel properties, assess the in-pile fuel performance in terms of coating integrity and fission metals release, and determine the fission product retention behavior during high temperature safety testing. A new furnace system has been designed, built, and tested to perform high temperature accident tests. The Fuel Accident Condition Simulator furnace system is designed to heat fuel specimens at temperatures up to 2000 degrees C in helium while monitoring the release of volatile fission metals (e.g. Cs, Ag, Sr, and Eu), iodine, and fission gases (Kr, Xe). Fission gases released from the fuel to the sweep gas are monitored in real time using dual cryogenic traps fitted with high purity germanium detectors. Condensable fission products are collected on a plate attached to a water-cooled cold finger that can be exchanged periodically without interrupting the test. Analysis of fission products on the condensation plates involves dry gamma counting followed by chemical analysis of selected isotopes. This paper will describe design and operational details of the Fuel Accident Condition Simulator furnace system and the associated fission gas monitoring system, as well as preliminary system calibration results.

  3. The shape of CMB temperature and polarization peaks on the sphere

    NASA Astrophysics Data System (ADS)

    Marcos-Caballero, A.; Fernández-Cobos, R.; Martínez-González, E.; Vielva, P.

    2016-04-01

    We present a theoretical study of CMB temperature peaks, including its effect over the polarization field, and allowing nonzero eccentricity. The formalism is developed in harmonic space and using the covariant derivative on the sphere, which guarantees that the expressions obtained are completely valid at large scales (i.e., no flat approximation). The expected patterns induced by the peak, either in temperature or polarization, are calculated, as well as their covariances. It is found that the eccentricity introduces a quadrupolar dependence in the peak shape, which is proportional to a complex bias parameter bepsilon, characterizing the peak asymmetry and orientation. In addition, the one-point statistics of the variables defining the peak on the sphere is reviewed, finding some differences with respect to the flat case for large peaks. Finally, we present a mechanism to simulate constrained CMB maps with a particular peak on the field, which is an interesting tool for analysing the statistical properties of the peaks present in the data.

  4. What we can learn from peak temperatures profiles in inverted metamorphic sequences

    NASA Astrophysics Data System (ADS)

    Duprat-Oualid, Sylvia; Yamato, Philippe

    2016-04-01

    Inverted metamorphic sequences correspond to the stacking of structural units through which the metamorphic peak temperatures progressively increase upwards. Such thermal profiles, already studied for years, are characteristic of lithospheric-scale thrust zones. Nevertheless, the processes allowing their formation still remain contentious. Several processes can, indeed, lead to peak temperatures inversion: heat advection, shear heating, in-depth accretion and/or erosion (allowing the exhumation of the overthrusting block). Furthermore, heat diffusion also has an important effect on temperatures distribution on both sides of the thrust. Each one of these processes distinctly impacts on the metamorphic thermal field in the vicinity of the thrust zone. However, their respective influences were never clearly analyzed and compared despite their crucial importance for the interpretation of the inverted peak temperatures signatures. Here, we thus propose to address this shortcoming by using two-dimensional numerical models simulating intra-continental thrusts systems. To do so, we combine a parametric numerical study and the "analytical characterization" of the computed inverted peak temperatures recorded, in our models, along profiles perpendicular to the thrust zone. The parametric combinations, including kinematic setting (i.e., convergence, erosion and accretion), thermal properties, mechanical strength and heat sources, control the processes into play during the thrust activity whose relative importances can be quantified. When the resulting peak temperatures profiles present a noticeable inversion, they are converted into a function of approximation characterized by six parameters. These six outputs then constitute the keys to quantitatively decipher the inversions features, not only in terms of spatial extent and intensity over time, but also by characterizing the peak temperatures trends on either sides of the domain of inversion. This numerical and analytical

  5. Contribution For Arc Temperature Affected By Current Increment Ratio At Peak Current In Pulsed Arc

    NASA Astrophysics Data System (ADS)

    Kano, Ryota; Mitubori, Hironori; Iwao, Toru

    2015-11-01

    Tungsten Inert Gas (TIG) Welding is one of the high quality welding. However, parameters of the pulsed arc welding are many and complicated. if the welding parameters are not appropriate, the welding pool shape becomes wide and shallow.the convection of driving force contributes to the welding pool shape. However, in the case of changing current waveform as the pulse high frequency TIG welding, the arc temperature does not follow the change of the current. Other result of the calculation, in particular, the arc temperature at the reaching time of peak current is based on these considerations. Thus, the accurate measurement of the temperature at the time is required. Therefore, the objective of this research is the elucidation of contribution for arc temperature affected by current increment ratio at peak current in pulsed arc. It should obtain a detail knowledge of the welding model in pulsed arc. The temperature in the case of increment of the peak current from the base current is measured by using spectroscopy. As a result, when the arc current increases from 100 A to 150 A at 120 ms, the transient response of the temperature didn't occur during increasing current. Thus, during the current rise, it has been verified by measuring. Therefore, the contribution for arc temperature affected by current increment ratio at peak current in pulsed arc was elucidated in order to obtain more knowledge of welding model of pulsed arc.

  6. Origin of low-temperature shoulder internal friction peak of Snoek-Köster peak in a medium carbon high alloyed steel

    NASA Astrophysics Data System (ADS)

    Lu, Xianwen; Jin, Mingjiang; Zhao, Hongshan; Li, Wei; Jin, Xuejun

    2014-10-01

    A distinct internal friction peak located at the low-temperature shoulder of Snoek-Köster peak (LTS-SK) was found in Fe-0.39C-9.8Ni-1.56Si-2.0Mn steel and its evolution with respect to various aging treatments was investigated. The LTS-SK internal friction peak was found to occur when aged below 373 K. TEM observation confirmed that the ε-carbide precipitated beyond 373 K, providing an evidence that the LTS-SK peak cannot be caused by ε-carbide precipitation. The corresponding evolution on the S-K peak and thermoelectric power (TEP) illustrated that the carbon content in the solid solution decreases due to carbon atoms segregation on the surrounding dislocations during low-temperature aging. The origin of the LTS-SK peak is likely attributed to the interaction between the carbon atoms and twin boundaries in martensite.

  7. Ion Size Effect on Glow Peak Temperature in Dielectric Binary Mixed Crystals Doped With Divalent Europium

    NASA Astrophysics Data System (ADS)

    Rodriguez-Mijangos, Ricardo; Perez-Salas, Raul

    2008-03-01

    Thermoluminiscence measurements at room temperature of ``beta'' irradiated divalent Europium doped binary mixed alkali halides with RbCl and KBr components at several concentrations x in molar fraction are carried out. The experiments have been carried out to identify the effect of composition in thermoluminiscense glow peaks. A typical glow peak has been distinguished for each composition. A linear dependence of its temperature on the composition x has been found. This is principally associated with the radii size change of halogen ions. Comparison with results in mixed KCl:KBr. KBr:RbBr and KCl:RbCl support that assertion.

  8. A relationship between peak temperature drop and velocity differential in a microburst

    NASA Technical Reports Server (NTRS)

    Proctor, Fred H.

    1989-01-01

    Results from numerical microburst simulations using the Terminal Area Simulation System (Proctor, 1987) are used to develop a relationship between wind velocity differential and peak temperature drop. The numerical model and the relationships derived from the model are described. The relationship between peak temperature drop and differential wind velocity is shown to be valid during microburst development, for all precipitation shaft intensities and diameters. It is found that the relationship is not valid for low-reflectivity microburst events or in the presence of ground-based stable layers. The use of the relationship in IR wind shear detection systems is considered.

  9. Temperature for Spent Fuel Dry Storage

    SciTech Connect

    1992-07-13

    DATING (Determining Allowable Temperatures in Inert and Nitrogen Gases) calculates allowable initial temperatures for dry storage of light-water-reactor spent fuel and the cumulative damage fraction of Zircaloy cladding for specified initial storage temperature and stress and cooling histories. It is made available to ensure compliance with NUREG 10CFR Part 72, Licensing Requirements for the Storage of Spent Fuel in an Independent Spent Fuel Storage Installation (ISFSI). Although the program''s principal purpose is to calculate estimates of allowable temperature limits, estimates for creep strain, annealing fraction, and life fraction as a function of storage time are also provided. Equations for the temperature of spent fuel in inert and nitrogen gas storage are included explicitly in the code; in addition, an option is included for a user-specified cooling history in tabular form, and tables of the temperature and stress dependencies of creep-strain rate and creep-rupture time for Zircaloy at constant temperature and constant stress or constant ratio of stress/modulus can be created. DATING includes the GEAR package for the numerical solution of the rate equations and DPLOT for plotting the time-dependence of the calculated cumulative damage-fraction, creep strain, radiation damage recovery, and temperature decay.

  10. Temperature for Spent Fuel Dry Storage

    Energy Science and Technology Software Center (ESTSC)

    1992-07-13

    DATING (Determining Allowable Temperatures in Inert and Nitrogen Gases) calculates allowable initial temperatures for dry storage of light-water-reactor spent fuel and the cumulative damage fraction of Zircaloy cladding for specified initial storage temperature and stress and cooling histories. It is made available to ensure compliance with NUREG 10CFR Part 72, Licensing Requirements for the Storage of Spent Fuel in an Independent Spent Fuel Storage Installation (ISFSI). Although the program''s principal purpose is to calculate estimatesmore » of allowable temperature limits, estimates for creep strain, annealing fraction, and life fraction as a function of storage time are also provided. Equations for the temperature of spent fuel in inert and nitrogen gas storage are included explicitly in the code; in addition, an option is included for a user-specified cooling history in tabular form, and tables of the temperature and stress dependencies of creep-strain rate and creep-rupture time for Zircaloy at constant temperature and constant stress or constant ratio of stress/modulus can be created. DATING includes the GEAR package for the numerical solution of the rate equations and DPLOT for plotting the time-dependence of the calculated cumulative damage-fraction, creep strain, radiation damage recovery, and temperature decay.« less

  11. Peak Seeking Control for Reduced Fuel Consumption with Preliminary Flight Test Results

    NASA Technical Reports Server (NTRS)

    Brown, Nelson

    2012-01-01

    The Environmentally Responsible Aviation project seeks to accomplish the simultaneous reduction of fuel burn, noise, and emissions. A project at NASA Dryden Flight Research Center is contributing to ERAs goals by exploring the practical application of real-time trim configuration optimization for enhanced performance and reduced fuel consumption. This peak-seeking control approach is based on Newton-Raphson algorithm using a time-varying Kalman filter to estimate the gradient of the performance function. In real-time operation, deflection of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of a modified F-18 are directly optimized, and the horizontal stabilators and angle of attack are indirectly optimized. Preliminary results from three research flights are presented herein. The optimization system found a trim configuration that required approximately 3.5% less fuel flow than the baseline trim at the given flight condition. The algorithm consistently rediscovered the solution from several initial conditions. These preliminary results show the algorithm has good performance and is expected to show similar results at other flight conditions and aircraft configurations.

  12. Effects of fictive temperature and halogen doping on the boson peak in silica glass

    NASA Astrophysics Data System (ADS)

    Shimodaira, N.; Saito, K.; Hiramitsu, N.; Matsushita, S.; Ikushima, A. J.

    2005-01-01

    We have investigated the effect of structural disorder on the boson peak in the Raman scattering of silica glass. The structural disorder was controlled in two ways: fictive temperature (Tf) and concentration of doped halogen element (F or Cl). As results, it has been simply demonstrated from nonreduced Raman spectra that (1) the peak position and full width at half maximum of the boson peak linearly increase with increasing Tf irrespective of the halogen concentrations, and in contrast, (2) the intensity is rather strongly dependent on the halogen concentrations than Tf . Since the result in (1) is much similar to the dependence on Tf and fluorine concentration for the IR absorption around 2260cm-1 , it has been concluded that the boson peak in silica glass is microscopically related to the average magnitude and distribution of Si-O-Si bond angles in glass network. The intensity enhancement in (2) has suggested two possibilities about the contribution of the doped halogen element to the boson peak: One is a direct contribution of F or Cl atoms due to diffusive motions falling within the range of the boson peak. The other is an indirect contribution introduced by the termination of Si-O-Si bridges to some sort of vibrational motions, which may be related to the boson peak.

  13. Intermediate temperature solid oxide fuel cells.

    PubMed

    Brett, Daniel J L; Atkinson, Alan; Brandon, Nigel P; Skinner, Stephen J

    2008-08-01

    High temperature solid oxide fuel cells (SOFCs), typified by developers such as Siemens Westinghouse and Rolls-Royce, operate in the temperature region of 850-1000 degrees C. For such systems, very high efficiencies can be achieved from integration with gas turbines for large-scale stationary applications. However, high temperature operation means that the components of the stack need to be predominantly ceramic and high temperature metal alloys are needed for many balance-of-plant components. For smaller scale applications, where integration with a heat engine is not appropriate, there is a trend to move to lower temperatures of operation, into the so-called intermediate temperature (IT) range of 500-750 degrees C. This expands the choice of materials and stack geometries that can be used, offering reduced system cost and, in principle, reducing the corrosion rate of stack and system components. This review introduces the IT-SOFC and explains the advantages of operation in this temperature regime. The main advances made in materials chemistry that have made IT operation possible are described and some of the engineering issues and the new opportunities that reduced temperature operation affords are discussed. This tutorial review examines the advances being made in materials and engineering that are allowing solid oxide fuel cells to operate at lower temperature. The challenges and advantages of operating in the so-called 'intermediate temperature' range of 500-750 degrees C are discussed and the opportunities for applications not traditionally associated with solid oxide fuel cells are highlighted. This article serves as an introduction for scientists and engineers interested in intermediate temperature solid oxide fuel cells and the challenges and opportunities of reduced temperature operation. PMID:18648682

  14. A regression approach to the analysis of serial peak flow among fuel oil ash exposed workers.

    PubMed

    Hauser, R; Daskalakis, C; Christiani, D C

    1996-10-01

    We investigated the association between exposure to fuel oil ash and acute airway obstruction in 31 boilermakers and 31 utility workers during the overhaul of a large oil-fired boiler. Air flow was assessed with self-recorded serial peak expiratory flow rate measurements (PEFR) using a mini-Wright meter. Exposure to thoracic particulates with an aerodynamic diameter of 10 gm or smaller (PM10) was assessed using personal sampling devices and detailed work diaries. All subjects were male, with an average age of 43 yr, and an average of 18 yr at their current trade. Average PM10 exposure on work days was 2.75 mg/m3 for boilermakers and 0.57 mg/m3 for utility workers. Three daily PEFR measurements (start-of-shift, end-of-shift, and bed-time) were analyzed simultaneously, using Huber linear regression. After adjustment for job title, welder status, age, height, smoking, and weld-years, for each mg/m3 increase in PM10, the estimated decline in PEFR was 13.2 L/min (p = 0.008) for end-of-shift, 9.9 L/min (p = 0.045) for bed-time, and 6.6 L/min (p = 0.26) for start-of-shift of the following day. This decline of the exposure effect over the 24-h period that follows was statistically significant (p = 0.004). No other factors were found to significantly modify the effect of exposure. Our results suggest that occupational exposure to fuel oil ash is associated with significant acute decrements in peak flow. PMID:8887594

  15. Analysis of the change in peak corneal temperature during excimer laser ablation in porcine eyes

    NASA Astrophysics Data System (ADS)

    Mosquera, Samuel Arba; Verma, Shwetabh

    2015-07-01

    The objective is to characterize the impact of different ablation parameters on the thermal load during corneal refractive surgery by means of excimer laser ablation on porcine eyes. One hundred eleven ablations were performed in 105 porcine eyes. Each ablation was recorded using infrared thermography and analyzed mainly based on the two tested local frequencies (40 Hz, clinical local frequency; 1000 Hz, no local frequency). The change in peak corneal temperature was analyzed with respect to varying ablation parameters [local frequency, system repetition rate, pulse energy, optical zone (OZ) size, and refractive correction]. Transepithelial ablations were also compared to intrastromal ablations. The average of the baseline temperature across all eyes was 20.5°C±1.1 (17.7°C to 22.2°C). Average of the change in peak corneal temperature for all clinical local frequency ablations was 5.8°C±0.8 (p=3.3E-53 to baseline), whereas the average was 9.0°C±1.5 for all no local frequency ablations (p=1.8E-35 to baseline, 1.6E-16 to clinical local frequency ablations). A logarithmic relationship was observed between the changes in peak corneal temperature with increasing local frequency. For clinical local frequency, change in peak corneal temperature was comparatively flat (r2=0.68 with a range of 1.5°C) with increasing system repetition rate and increased linearly with increasing OZ size (r2=0.95 with a range of 2.4°C). Local frequency controls help maintain safe corneal temperature increase during excimer laser ablations. Transepithelial ablations induce higher thermal load compared to intrastromal ablations, indicating a need for stronger thermal controls in transepithelial refractive procedures.

  16. Validation of the BISON 3D Fuel Performance Code: Temperature Comparisons for Concentrically and Eccentrically Located Fuel Pellets

    SciTech Connect

    J. D. Hales; D. M. Perez; R. L. Williamson; S. R. Novascone; B. W. Spencer

    2013-03-01

    BISON is a modern finite-element based nuclear fuel performance code that has been under development at the Idaho National Laboratory (USA) since 2009. The code is applicable to both steady and transient fuel behaviour and is used to analyse either 2D axisymmetric or 3D geometries. BISON has been applied to a variety of fuel forms including LWR fuel rods, TRISO-coated fuel particles, and metallic fuel in both rod and plate geometries. Code validation is currently in progress, principally by comparison to instrumented LWR fuel rods. Halden IFA experiments constitute a large percentage of the current BISON validation base. The validation emphasis here is centreline temperatures at the beginning of fuel life, with comparisons made to seven rods from the IFA-431 and 432 assemblies. The principal focus is IFA-431 Rod 4, which included concentric and eccentrically located fuel pellets. This experiment provides an opportunity to explore 3D thermomechanical behaviour and assess the 3D simulation capabilities of BISON. Analysis results agree with experimental results showing lower fuel centreline temperatures for eccentric fuel with the peak temperature shifted from the centreline. The comparison confirms with modern 3D analysis tools that the measured temperature difference between concentric and eccentric pellets is not an artefact and provides a quantitative explanation for the difference.

  17. Relationship between peak spatial-averaged specific absorption rate and peak temperature elevation in human head in frequency range of 1–30 GHz

    NASA Astrophysics Data System (ADS)

    Morimoto, Ryota; Laakso, Ilkka; De Santis, Valerio; Hirata, Akimasa

    2016-07-01

    This study investigates the relationship between the peak temperature elevation and the peak specific absorption rate (SAR) averaged over 10 g of tissue in human head models in the frequency range of 1–30 GHz. As a wave source, a half-wave dipole antenna resonant at the respective frequencies is located in the proximity of the pinna. The bioheat equation is used to evaluate the temperature elevation by employing the SAR, which is computed by electromagnetic analysis, as a heat source. The computed SAR is post-processed by calculating the peak spatial-averaged SAR with six averaging algorithms that consider different descriptions provided in international guidelines and standards, e.g. the number of tissues allowed in the averaging volume, different averaging shapes, and the consideration of the pinna. The computational results show that the SAR averaging algorithms excluding the pinna are essential when correlating the peak temperature elevation in the head excluding the pinna. In the averaging scheme considering an arbitrary shape, for better correlation, multiple tissues should be included in the averaging volume rather than a single tissue. For frequencies higher than 3–4 GHz, the correlation for peak temperature elevation in the head excluding the pinna is modest for the different algorithms. The 95th percentile value of the heating factor as well as the mean and median values derived here would be helpful for estimating the possible temperature elevation in the head.

  18. Portable peak flow meters: physical characteristics, influence of temperature, altitude, and humidity.

    PubMed

    Pedersen, O F; Miller, M R; Sigsgaard, T; Tidley, M; Harding, R M

    1994-05-01

    Little is known about the linearity of portable peak flow meters, or about physical gas factors affecting peak expiratory flow (PEF) readings. We therefore tested five portable peak flow meters of three types in an altitude chamber (sea level to 5,500 m) and in a climate chamber at sea level (7-37 degrees C) to determine the influence of the physical conditions of the gas on the reading of the meters. The nonlinear response of the variable orifice meters was confirmed and, when this was corrected for, the readings of these meters were found to be significantly reduced by higher altitude and lower temperature. The readings from a turbine type of peak flow meter were not affected by altitude but were reduced at low temperature. A mathematical model for the variable orifice meters could correct for both their nonlinear behaviour and the effect of gas density (altitude, temperature and humidity). The model showed that correction is not necessary for the differences in gas conditions between calibration and taking of measurements under normal laboratory conditions. All the meters tested had impedances higher than recommended (0.05 kPa.l-1.s) and this may influence PEF at high flows. The mean uncorrected PEF of six healthy subjects when measured with a Mini Wright peak flow meter at sea level and at 3,000 m fell by 5%, but the mean corrected PEF increased by 12%. This increase in PEF was about 60% of that predicted for fully density-dependent flow and agreed with the findings of other similar studies.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8050558

  19. Ion Size Effect in Glow Peak Temperature in Binary Mixed Crystals Doped with Divalente Europium

    NASA Astrophysics Data System (ADS)

    Rodriguez-Mijangos, Ricardo; Perez-Salas, Raul

    2006-03-01

    Thermoluminiscence measurements at room temperature of ``beta'' irradiated divalent Europium doped binary mixed alkali halides with KCl and KBr components at several concentrations x in molar fraction. The experiments have been carried out to identify the effect of composition of glow peaks. A typical glow peak has been distinguished for each composition. A linear dependence of its temperature on the composition x has been found. This is associated with the size change of ions Cl and Br. Initial comparative cathodoluminiscent measurement was carried out irradiating a single sample with electrons in an electron microscopy using a 30 KV voltage. With the present results is speculated the behavior of the mixed binary crystals with components KCl and RbCl, doped with divalent Europium.

  20. Technical Basis for Peak Reactivity Burnup Credit for BWR Spent Nuclear Fuel in Storage and Transportation Systems

    SciTech Connect

    Marshall, William BJ J; Ade, Brian J; Bowman, Stephen M; Gauld, Ian C; Ilas, Germina; Mertyurek, Ugur; Radulescu, Georgeta

    2015-01-01

    Oak Ridge National Laboratory and the United States Nuclear Regulatory Commission have initiated a multiyear project to investigate application of burnup credit for boiling-water reactor (BWR) fuel in storage and transportation casks. This project includes two phases. The first phase (1) investigates applicability of peak reactivity methods currently used in spent fuel pools (SFPs) to storage and transportation systems and (2) evaluates validation of both reactivity (keff) calculations and burnup credit nuclide concentrations within these methods. The second phase will focus on extending burnup credit beyond peak reactivity. This paper documents the first phase, including an analysis of lattice design parameters and depletion effects, as well as both validation components. Initial efforts related to extended burnup credit are discussed in a companion paper. Peak reactivity analyses have been used in criticality analyses for licensing of BWR fuel in SFPs over the last 20 years. These analyses typically combine credit for the gadolinium burnable absorber present in the fuel with a modest amount of burnup credit. Gadolinium burnable absorbers are used in BWR assemblies to control core reactivity. The burnable absorber significantly reduces assembly reactivity at beginning of life, potentially leading to significant increases in assembly reactivity for burnups less than 15–20 GWd/MTU. The reactivity of each fuel lattice is dependent on gadolinium loading. The number of gadolinium-bearing fuel pins lowers initial lattice reactivity, but it has a small impact on the burnup and reactivity of the peak. The gadolinium concentration in each pin has a small impact on initial lattice reactivity but a significant effect on the reactivity of the peak and the burnup at which the peak occurs. The importance of the lattice parameters and depletion conditions are primarily determined by their impact on the gadolinium depletion. Criticality code validation for BWR burnup

  1. Intermediate Temperature Solid Oxide Fuel Cell Development

    SciTech Connect

    S. Elangovan; Scott Barnett; Sossina Haile

    2008-06-30

    Solid oxide fuel cells (SOFCs) are high efficiency energy conversion devices. Present materials set, using yttria stabilized zirconia (YSZ) electrolyte, limit the cell operating temperatures to 800 C or higher. It has become increasingly evident however that lowering the operating temperature would provide a more expeditious route to commercialization. The advantages of intermediate temperature (600 to 800 C) operation are related to both economic and materials issues. Lower operating temperature allows the use of low cost materials for the balance of plant and limits degradation arising from materials interactions. When the SOFC operating temperature is in the range of 600 to 700 C, it is also possible to partially reform hydrocarbon fuels within the stack providing additional system cost savings by reducing the air preheat heat-exchanger and blower size. The promise of Sr and Mg doped lanthanum gallate (LSGM) electrolyte materials, based on their high ionic conductivity and oxygen transference number at the intermediate temperature is well recognized. The focus of the present project was two-fold: (a) Identify a cell fabrication technique to achieve the benefits of lanthanum gallate material, and (b) Investigate alternative cathode materials that demonstrate low cathode polarization losses at the intermediate temperature. A porous matrix supported, thin film cell configuration was fabricated. The electrode material precursor was infiltrated into the porous matrix and the counter electrode was screen printed. Both anode and cathode infiltration produced high performance cells. Comparison of the two approaches showed that an infiltrated cathode cells may have advantages in high fuel utilization operations. Two new cathode materials were evaluated. Northwestern University investigated LSGM-ceria composite cathode while Caltech evaluated Ba-Sr-Co-Fe (BSCF) based pervoskite cathode. Both cathode materials showed lower polarization losses at temperatures as low as 600

  2. 40 CFR 1066.950 - Fuel temperature profile.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Test Procedures for Motor Vehicles § 1066.950 Fuel temperature profile. Develop fuel temperature profiles for running loss testing as described in 40 CFR 86.129-94(d). ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Fuel temperature profile....

  3. Transient response of high temperature PEM fuel cell

    NASA Astrophysics Data System (ADS)

    Peng, J.; Shin, J. Y.; Song, T. W.

    A transient three-dimensional, single-phase and non-isothermal numerical model of polymer electrolyte membrane (PEM) fuel cell with high operating temperature has been developed and implemented in computational fluid dynamic (CFD) code. The model accounts for transient convective and diffusive transport, and allows prediction of species concentration. Electrochemical charge double-layer effect is considered. Heat generation according to electrochemical reaction and ohmic loss are involved. Water transportation across membrane is ignored due to low water electro-osmosis drag force of polymer polybenzimidazole (PBI) membrane. The prediction shows transient in current density which overshoots (undershoots) the stabilized state value when cell voltage is abruptly decreased (increased). The result shows that the peak of overshoot (undershoot) is related with cathode air stoichiometric mass flow rate instead of anode hydrogen stoichiometric mass flow rate. Current is moved smoothly and there are no overshoot or undershoot with the influence of charge double-layer effect. The maximum temperature is located in cathode catalyst layer and both fuel cell average temperature and temperature deviation are increased with increasing of current load.

  4. Peak temperature in intracratonic basins constrained by magnetic studies:Example of the Illinois Basin

    NASA Astrophysics Data System (ADS)

    Uz, E.; Ferre, E. C.; Rimmer, S.; Morse, D. G.; Crockett, J. E.

    2012-12-01

    consists in baking series of aliquot crushed unmetamorphosed sandstones at step-wise temperatures (11 steps) to determine their overall pattern of magnetic changes with temperature. The possible roles of basinal fluids and pressure are ignored in the current experiments. The choice of crushed material as opposed to oriented samples is motivated by the need for the new method to be applicable to drilling chips that are typically produced in oil and gas exploration. The specimens were cemented and baked at step temperatures from 75 to 400 degrees Celsius. The results of these experiments serve to build calibration curves for the method. The burial temperature of specimens of unknown burial temperature is obtained by comparison with those of the calibration runs. Although the new method provides only information on peak burial temperatures, as opposed to complete heating history, this shortfall is common to all existing low-temperature geothermometers.

  5. MELT WIRE SENSORS AVAILABLE TO DETERMINE PEAK TEMPERATURES IN ATR IRRADIATION TESTING

    SciTech Connect

    K. L. Davis; D. Knudson; J. Daw; J. Palmer; J. L. Rempe

    2012-07-01

    In April 2007, the Department of Energy (DOE) designated the Advanced Test Reactor (ATR) a National Scientific User Facility (NSUF) to advance US leadership in nuclear science and technology. By attracting new users from universities, laboratories, and industry, the ATR will support basic and applied nuclear research and development and help address the nation's energy security needs. In support of this new program, the Idaho National Laboratory (INL) has developed in-house capabilities to fabricate, test, and qualify new and enhanced temperature sensors for irradiation testing. Although most efforts emphasize sensors capable of providing real-time data, selected tasks have been completed to enhance sensors provided in irradiation locations where instrumentation leads cannot be included, such as drop-in capsule and Hydraulic Shuttle Irradiation System (HSIS) or 'rabbit' locations. To meet the need for these locations, the INL has developed melt wire temperature sensors for use in ATR irradiation testing. Differential scanning calorimetry and environmental testing of prototypical sensors was used to develop a library of 28 melt wire materials, capable of detecting peak irradiation temperatures ranging from 85 to 1500°C. This paper will discuss the development work and present test results.

  6. Peak metamorphic temperature and thermal history of the Southern Alps (New Zealand)

    NASA Astrophysics Data System (ADS)

    Beyssac, O.; Cox, S. C.; Vry, J.; Herman, F.

    2016-04-01

    The Southern Alps orogen of New Zealand results from late Cenozoic convergence between the Indo-Australian and Pacific plates and is one of the most active mountain belts in the world. Metamorphic rocks carrying a polymetamorphic legacy, ranging from low-greenschist to high-grade amphibolites, are exhumed in the hanging wall of the Alpine Fault. On a regional scale, the metamorphic grade has previously been described in terms of metamorphic zones and mineral isograds; application of quantitative petrology being severely limited owing to unfavorable quartzofeldspathic lithologies. This study quantifies peak metamorphic temperatures (T) in a 300 × 20 km area, based on samples forming 13 transects along-strike from Haast in the south to Hokitika in the north, using thermometry based on Raman spectroscopy of carbonaceous material (RSCM). Peak metamorphic T decreases across each transect from ≥ 640 °C locally in the direct vicinity of the Alpine Fault to less than 330 °C at the drainage divide 15-20 km southeast of the fault. Thermal field gradients exhibit a degree of similarity from the southernmost to the northernmost transects, are greater in low-grade semischist than high-grade schist, are affected by folding or discontinuous juxtaposition of metamorphic zones, and contain limited information on crustal-scale geothermal gradients. Temperatures derived by RSCM thermometry are slightly (≤ 50 °C) higher than those derived by traditional quantitative petrology using garnet-biotite thermometry and THERMOCALC modeling. The age of RSCM T appears to be mostly pre-Cenozoic over most of the area except in central Southern Alps (Franz Josef-Fox area), where the amphibolite facies schists have T of likely Cenozoic age. The RSCM T data place some constraints on the mode of exhumation along the Alpine Fault and have implications for models of Southern Alps tectonics.

  7. Temperature Stratification in a Cryogenic Fuel Tank

    NASA Technical Reports Server (NTRS)

    Daigle, Matthew John; Smelyanskiy, Vadim; Boschee, Jacob; Foygel, Michael Gregory

    2013-01-01

    A reduced dynamical model describing temperature stratification effects driven by natural convection in a liquid hydrogen cryogenic fuel tank has been developed. It accounts for cryogenic propellant loading, storage, and unloading in the conditions of normal, increased, and micro- gravity. The model involves multiple horizontal control volumes in both liquid and ullage spaces. Temperature and velocity boundary layers at the tank walls are taken into account by using correlation relations. Heat exchange involving the tank wall is considered by means of the lumped-parameter method. By employing basic conservation laws, the model takes into consideration the major multi-phase mass and energy exchange processes involved, such as condensation-evaporation of the hydrogen, as well as flows of hydrogen liquid and vapor in the presence of pressurizing helium gas. The model involves a liquid hydrogen feed line and a tank ullage vent valve for pressure control. The temperature stratification effects are investigated, including in the presence of vent valve oscillations. A simulation of temperature stratification effects in a generic cryogenic tank has been implemented in Matlab and results are presented for various tank conditions.

  8. Temperature feedback of TRIGA MARK-II fuel

    NASA Astrophysics Data System (ADS)

    Usang, M. D.; Minhat, M. S.; Rabir, M. H.; M. Rawi M., Z.

    2016-01-01

    We study the amount of temperature feedback on reactivity for the three types of TRIGA fuel i.. ST8, ST12 and LEU fuel, are used in the TRIGA MARK II reactor in Malaysia Nuclear Agency. We employ WIMSD-5B for the calculation of kin f for a single TRIGA fuel surrounded by water. Typical calculations of TRIGA fuel reactivity are usually limited to ST8 fuel, but in this paper our investigation extends to ST12 and LEU fuel. We look at the kin f of our model at various fuel temperatures and calculate the amount reactivity removed. In one instance, the water temperature is kept at room temperature of 300K to simulate sudden reactivity increase from startup. In another instance, we simulate the sudden temperature increase during normal operation where the water temperature is approximately 320K while observing the kin f at various fuel temperatures. For accidents, two cases are simulated. The first case is for water temperature at 370K and the other is without any water. We observe that the higher Uranium content fuel such as the ST12 and LEU have much smaller contribution to the reactivity in comparison to the often studied ST8 fuel. In fact the negative reactivity coefficient for LEU fuel at high temperature in water is only slightly larger to the negative reactivity coefficient for ST8 fuel in void. The performance of ST8 fuel in terms of negative reactivity coefficient is cut almost by half when it is in void. These results are essential in the safety evaluation of the reactor and should be carefully considered when choices of fuel for core reconfiguration are made.

  9. Novel Low Temperature Solid State Fuel Cells

    SciTech Connect

    Chen, Chonglin; Nash, Patrick; Liu, Jian; Collins, Gregory

    2009-12-15

    We have successfully fabricated (PrBa)Co{sub 2}O{sub 5+{delta}} and (LaBa)Co{sub 2}O{sub 5+{deleta}} epitaxial thin film on various single crystal substrates. Physical and electrochemical properties characterizations were carried out. Highly conductive oxygen-deficient double perovskite LnBaCo2O5+? thin films were grown on single crystal (001) SrTiO{sub 3} (STO), (001) MgO, (001) LaAlO{sub 3} and (110) NdGaO{sub 3} substrate by pulsed laser deposition. Microstructure studies from synchrotron X-ray diffraction and Transmission electron microscopy. High temperature transport properties was carried in different atmosphere (O{sub 2},Air, N{sub 2}) up to ~900K. Resistance response of (LaBa)Co{sub 2}O{sub 5+{delta}} epitaxial thin film was characterized in oxygen, nitrogen and 4% hydrogen over a wide range of temperature from 400�C up to 800�C. To determine the electrode performance and oxygen exchange kinetics of PrBaCo{sub 2}O{sub 5+{delta}}, multi-layered thin film based half cell was deposited on LaAlO{sub 3}(001) substrate. The temperature dependence of the resistance of this half ?cell structure was characterized by electrochemical impedance spectroscopy (EIS) within different temperature and gas environments. Anode supported fuel cells, with GCO:YSZ multilayer thin film as electrolyte and PBCO thin film as electrode, are fabricated on tape casted NiO/YSZ substrate. Full cell performance is characterized up to 800�C.

  10. Dependence of curing time, peak temperature, and mechanical properties on the composition of bone cement.

    PubMed

    Brauer, G M; Steinberger, D R; Stansbury, J W

    1986-01-01

    Commercial bone cements usually contain hydroquinone as the polymerization inhibitor and N,N-dimethyl-p-toluidine as the accelerator in the benzoyl peroxide-initiated redox polymerization. The former compounds have certain shortcomings in their biocompatibility profile. Measurements of the setting times, polymerization exotherms, and postpolymerization strengths of the cured monomer-polymer compositions show that the hydroquinone can be replaced by food grade di-tert-butyl-p-cresol (BHT). The more reactive 4-N,N-(dimethylamino)phenethanol can replace 4-N,N-dimethyl-p-toluidine, yielding cements with shorter setting times and increased strengths. Excessive heat liberated on polymerization can be reduced by partial substitution of higher-molecular-weight methacrylates, e.g., dicyclopentenyloxyethyl methacrylate for methyl methacrylate, but there is a decrease in strength of the resulting polymer. More successful has been the addition to the monomer of 1% or 2% of the chain transfer agent pentaerythritol tetra(3-mercaptopropionate), which lowers the peak temperature without changing the physical properties of the cement. Compositions with short curing times, lower exotherms, and mechanical properties that exceed those of a commercial material have been formulated. PMID:3722218

  11. Mixed field peronnel dosimetry: Part 1, High temperature peak characteristics of the reader-annealed TLD-600

    SciTech Connect

    Liu, J.C. ); Sims, C.S. )

    1991-02-01

    The high temperature peaks (TL peaks 6--7) of TLD-600 are known to have higher responses to high LET radiation than to low LET radiation. These high temperature peak characteristics were studied for the automatic reader-annealed Harshaw albedo neutron TLD. The high temperature peaks response is linear for neutrons over the dose equivalent range tested (0.05--3 mSv of a {sup 252}Cf source moderated by a 15 cm radius polyethylene sphere), but is supralinear above 20 mSv of {sup 137}Cs photons. The peaks ratio (peaks 6--7/peaks 3--5) of TLD-600 is 0.15 for neutrons of any incident energy, 0.01 for {sup 137}Cs gammas, and 0.02 for M-150 x-rays. Based on the high temperature peak characteristics, a mixed field neutron-photon personnel dosimetry methodology using a single TLD-600 element was developed. The dosimetric method was evaluated in mixed {sup 238}PuBe + {sup 137}Cs fields with four neutron-gamma dose equivalent ratios, and the neutron, photon and total dose equivalent estimations are better than 20% except in one case. However, it was found that the neutron and photon dose equivalent estimations are sensitive to the neutron and photon peaks ratios, depending on the neutron-photon dose equivalent ratio and the neutron source in the mixed field. Therefore, a successful use of this method requires knowledge of the photon and neutron energies in the mixed field. 13 refs., 6 figs., 2 tabs.

  12. Measurement and correlation of jet fuel viscosities at low temperatures

    NASA Technical Reports Server (NTRS)

    Schruben, D. L.

    1985-01-01

    Apparatus and procedures were developed to measure jet fuel viscosity for eight current and future jet fuels at temperatures from ambient to near -60 C by shear viscometry. Viscosity data showed good reproducibility even at temperatures a few degrees below the measured freezing point. The viscosity-temperature relationship could be correlated by two linear segments when plotted as a standard log-log type representation (ASTM D 341). At high temperatures, the viscosity-temperature slope is low. At low temperatures, where wax precipitation is significant, the slope is higher. The breakpoint between temperature regions is the filter flow temperature, a fuel characteristic approximated by the freezing point. A generalization of the representation for the eight experimental fuels provided a predictive correlation for low-temperature viscosity, considered sufficiently accurate for many design or performance calculations.

  13. Preparation of high temperature gas-cooled reactor fuel element

    DOEpatents

    Bradley, Ronnie A.; Sease, John D.

    1976-01-01

    This invention relates to a method for the preparation of high temperature gas-cooled reactor (HTGR) fuel elements wherein uncarbonized fuel rods are inserted in appropriate channels of an HTGR fuel element block and the entire block is inserted in an autoclave for in situ carbonization under high pressure. The method is particularly applicable to remote handling techniques.

  14. Estimating peak and solidification temperatures for anatectic pelitic migmatites using phase diagrams: sampling heterogeneous migmatites and confronting melt loss

    NASA Astrophysics Data System (ADS)

    Hamilton, Brett M.; Pattison, David R. M.

    2016-04-01

    Calculating a pressure-temperature phase diagram relevant to an anatectic pelitic migmatite sampled in outcrop is challenging because it is unclear what constitutes a meaningful bulk composition. Melt loss during metamorphism may have changed the bulk composition. The heterogeneous nature of migmatites, with light and dark coloured domains (leucosome and melanosome), means a choice must be made regarding how a migmatitic outcrop should be sampled. To address these issues, migmatites were simulated using thermodynamic modelling techniques for different melting and crystallization scenarios and bulk compositions. Using phase diagrams calculated for varying proportions of simulated melanosome and leucosome, temperatures of interest were estimated and compared with known values. Our modelling suggests: (1) It is generally possible to constrain the peak temperature using phase diagrams calculated with the composition of the melanosome; the more leucosome that is incorporated, the more innaccurate the estimate. For phase diagrams calculated using a combination of leucosome and melanosome material, peak temperature estimates differ from actual peak conditions by ‑25 to +50°C. In certain of these cases, such as those involving high proportions of leucosome to melanosome, or in which solid K-feldspar was absent at peak conditions, but is now present in the rock due to later crystallization from melt, it is not possible to estimate peak temperature. (2) The solidification temperature, whether due to crystallization of the last melt or physical loss of the melt during crystallization, will fall between the peak temperature and the water-saturated solidus (~660°C) if the melt and solids chemically interacted during cooling. This temperature can be accurately constrained from the phase diagram. If the melt crystallized in chemical isolation from the melanosome, the solidification temperature is the water-saturated solidus (625-645°C); however, physical melt loss during

  15. In vitro infrared thermography assessment of temperature peaks during the intra-oral welding of titanium abutments

    NASA Astrophysics Data System (ADS)

    Degidi, Marco; Nardi, Diego; Sighinolfi, Gianluca; Merla, Arcangelo; Piattelli, Adriano

    2012-07-01

    Control of heat dissipation and transmission to the peri-implant area during intra-oral welding is very important to limit potential damage to the surrounding tissue. The aim of this in vitro study was to assess, by means of thermal infrared imaging, the tissue temperature peaks associated with the thermal propagation pathway through the implants, the abutments and the walls of the slot of the scaffold, generated during the welding process, in three different implant systems. An in vitro polyurethane mandible model was prepared with a 7.0 mm v-shape slot. Effects on the maximum temperature by a single welding procedure were studied using different power supplies and abutments. A total of 36 welding procedures were tested on three different implant systems. The lowest peak temperature along the walls of the 7.0 mm v-shaped groove (31.6 ± 2 °C) was assessed in the specimens irrigated with sterile saline solution. The highest peak temperature (42.8 ± 2 °C) was assessed in the samples with a contemporaneous power overflow and premature pincers removal. The results of our study suggest that the procedures used until now appear to be effective to avoid thermal bone injuries. The peak tissue temperature of the in vitro model did not surpass the threshold limits above which tissue injury could occur.

  16. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-12-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching {approximately}660{degree}C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  17. Performance of HT9 clad metallic fuel at high temperature

    SciTech Connect

    Pahl, R.G.; Lahm, C.E.; Hayes, S.L.

    1992-01-01

    Steady-state testing of HT9 clad metallic fuel at high temperatures was initiated in EBR-II in November of 1987. At that time U-10 wt. % Zr fuel clad with the low-swelling ferritic/martensitic alloy HT9 was being considered as driver fuel options for both EBR-II and FFTF. The objective of the X447 test described here was to determine the lifetime of HT9 cladding when operated with metallic fuel at beginning of life inside wall temperatures approaching [approximately]660[degree]C. Though stress-temperature design limits for HT9 preclude its use for high burnup applications under these conditions due to excessive thermal creep, the X447 test was carried out to obtain data on high temperature breach phenomena involving metallic fuel since little data existed in that area.

  18. Children and adults exposed to electromagnetic fields at the ICNIRP reference levels: theoretical assessment of the induced peak temperature increase.

    PubMed

    Bakker, J F; Paulides, M M; Neufeld, E; Christ, A; Kuster, N; van Rhoon, G C

    2011-08-01

    To avoid potentially adverse health effects of electromagnetic fields (EMF), the International Commission on Non-Ionizing Radiation Protection (ICNIRP) has defined EMF reference levels. Restrictions on induced whole-body-averaged specific absorption rate (SAR(wb)) are provided to keep the whole-body temperature increase (T(body, incr)) under 1 °C during 30 min. Additional restrictions on the peak 10 g spatial-averaged SAR (SAR(10g)) are provided to prevent excessive localized tissue heating. The objective of this study is to assess the localized peak temperature increase (T(incr, max)) in children upon exposure at the reference levels. Finite-difference time-domain modeling was used to calculate T(incr, max) in six children and two adults exposed to orthogonal plane-wave configurations. We performed a sensitivity study and Monte Carlo analysis to assess the uncertainty of the results. Considering the uncertainties in the model parameters, we found that a peak temperature increase as high as 1 °C can occur for worst-case scenarios at the ICNIRP reference levels. Since the guidelines are deduced from temperature increase, we used T(incr, max) as being a better metric to prevent excessive localized tissue heating instead of localized peak SAR. However, we note that the exposure time should also be considered in future guidelines. Hence, we advise defining limits on T(incr, max) for specified durations of exposure. PMID:21772085

  19. Solid oxide fuel cell operable over wide temperature range

    DOEpatents

    Baozhen, Li; Ruka, Roswell J.; Singhal, Subhash C.

    2001-01-01

    Solid oxide fuel cells having improved low-temperature operation are disclosed. In one embodiment, an interfacial layer of terbia-stabilized zirconia is located between the air electrode and electrolyte of the solid oxide fuel cell. The interfacial layer provides a barrier which controls interaction between the air electrode and electrolyte. The interfacial layer also reduces polarization loss through the reduction of the air electrode/electrolyte interfacial electrical resistance. In another embodiment, the solid oxide fuel cell comprises a scandia-stabilized zirconia electrolyte having high electrical conductivity. The scandia-stabilized zirconia electrolyte may be provided as a very thin layer in order to reduce resistance. The scandia-stabilized electrolyte is preferably used in combination with the terbia-stabilized interfacial layer. The solid oxide fuel cells are operable over wider temperature ranges and wider temperature gradients in comparison with conventional fuel cells.

  20. Fuel processor temperature monitoring and control

    DOEpatents

    Keskula, Donald H.; Doan, Tien M.; Clingerman, Bruce J.

    2002-01-01

    In one embodiment, the method of the invention monitors one or more of the following conditions: a relatively low temperature value of the gas stream; a relatively high temperature value of the gas stream; and a rate-of-change of monitored temperature. In a preferred embodiment, the rate of temperature change is monitored to prevent the occurrence of an unacceptably high or low temperature condition. Here, at least two temperatures of the recirculating gas stream are monitored over a period of time. The rate-of-change of temperature versus time is determined. Then the monitored rate-of-change of temperature is compared to a preselected rate-of-change of value. The monitoring of rate-of-change of temperature provides proactive means for preventing occurrence of an unacceptably high temperature in the catalytic reactor.

  1. Temperature and Burnup Correlated FCCI in U-10Zr Metallic Fuel

    SciTech Connect

    William J. Carmack

    2012-05-01

    the EBR-II and study of the differences between the two fuel systems is critical for design of large advanced sodium cooled fast reactor systems. Comparing FCCI layer formation data between FFTF and EBR-II indicates that the same diffusion model can be used to represent the two systems when considering time, temperature, burnup history, and axial temperature and power profiles. This dissertation shows that FCCI formation peaks further below the top of the fuel column in FFTF experiments than has been observed in EBR-II experiments. The work provided in this dissertation will help forward the design of advanced metallic fuel systems for advanced sodium cooled fast reactors by allowing the prediction of FCCI layer formation in full length reactor designs. This will allow the accurate lifetime prediction of fuel performance capability for new advanced sodium cooled fast reactors with extended core designs.

  2. System for controlling the operating temperature of a fuel cell

    DOEpatents

    Fabis, Thomas R.; Makiel, Joseph M.; Veyo, Stephen E.

    2006-06-06

    A method and system are provided for improved control of the operating temperature of a fuel cell (32) utilizing an improved temperature control system (30) that varies the flow rate of inlet air entering the fuel cell (32) in response to changes in the operating temperature of the fuel cell (32). Consistent with the invention an improved temperature control system (30) is provided that includes a controller (37) that receives an indication of the temperature of the inlet air from a temperature sensor (39) and varies the heat output by at least one heat source (34, 36) to maintain the temperature of the inlet air at a set-point T.sub.inset. The controller (37) also receives an indication of the operating temperature of the fuel cell (32) and varies the flow output by an adjustable air mover (33), within a predetermined range around a set-point F.sub.set, in order to maintain the operating temperature of the fuel cell (32) at a set-point T.sub.opset.

  3. Lowering the temperature of solid oxide fuel cells.

    PubMed

    Wachsman, Eric D; Lee, Kang Taek

    2011-11-18

    Fuel cells are uniquely capable of overcoming combustion efficiency limitations (e.g., the Carnot cycle). However, the linking of fuel cells (an energy conversion device) and hydrogen (an energy carrier) has emphasized investment in proton-exchange membrane fuel cells as part of a larger hydrogen economy and thus relegated fuel cells to a future technology. In contrast, solid oxide fuel cells are capable of operating on conventional fuels (as well as hydrogen) today. The main issue for solid oxide fuel cells is high operating temperature (about 800°C) and the resulting materials and cost limitations and operating complexities (e.g., thermal cycling). Recent solid oxide fuel cells results have demonstrated extremely high power densities of about 2 watts per square centimeter at 650°C along with flexible fueling, thus enabling higher efficiency within the current fuel infrastructure. Newly developed, high-conductivity electrolytes and nanostructured electrode designs provide a path for further performance improvement at much lower temperatures, down to ~350°C, thus providing opportunity to transform the way we convert and store energy. PMID:22096189

  4. High temperature solid electrolyte fuel cell configurations and interconnections

    DOEpatents

    Isenberg, Arnold O.

    1984-01-01

    High temperature fuel cell configurations and interconnections are made including annular cells having a solid electrolyte sandwiched between thin film electrodes. The cells are electrically interconnected along an elongated axial outer surface.

  5. Temperature measuring analysis of the nuclear reactor fuel assembly

    SciTech Connect

    Urban, F. E-mail: zdenko.zavodny@stuba.sk; Kučák, L. E-mail: zdenko.zavodny@stuba.sk; Bereznai, J. E-mail: zdenko.zavodny@stuba.sk; Závodný, Z. E-mail: zdenko.zavodny@stuba.sk; Muškát, P. E-mail: zdenko.zavodny@stuba.sk

    2014-08-06

    Study was based on rapid changes of measured temperature values from the thermocouple in the VVER 440 nuclear reactor fuel assembly. Task was to determine origin of fluctuations of the temperature values by experiments on physical model of the fuel assembly. During an experiment, heated water was circulating in the system and cold water inlet through central tube to record sensitivity of the temperature sensor. Two positions of the sensor was used. First, just above the central tube in the physical model fuel assembly axis and second at the position of the thermocouple in the VVER 440 nuclear reactor fuel assembly. Dependency of the temperature values on time are presented in the diagram form in the paper.

  6. Thermodynamic analysis of biofuels as fuels for high temperature fuel cells

    NASA Astrophysics Data System (ADS)

    Milewski, Jarosław; Bujalski, Wojciech; Lewandowski, Janusz

    2013-02-01

    Based on mathematical modeling and numerical simulations, applicativity of various biofuels on high temperature fuel cell performance are presented. Governing equations of high temperature fuel cell modeling are given. Adequate simulators of both solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) have been done and described. Performance of these fuel cells with different biofuels is shown. Some characteristics are given and described. Advantages and disadvantages of various biofuels from the system performance point of view are pointed out. An analysis of various biofuels as potential fuels for SOFC and MCFC is presented. The results are compared with both methane and hydrogen as the reference fuels. The biofuels are characterized by both lower efficiency and lower fuel utilization factors compared with methane. The presented results are based on a 0D mathematical model in the design point calculation. The governing equations of the model are also presented. Technical and financial analysis of high temperature fuel cells (SOFC and MCFC) are shown. High temperature fuel cells can be fed by biofuels like: biogas, bioethanol, and biomethanol. Operational costs and possible incomes of those installation types were estimated and analyzed. A comparison against classic power generation units is shown. A basic indicator net present value (NPV) for projects was estimated and commented.

  7. Thermodynamic analysis of biofuels as fuels for high temperature fuel cells

    NASA Astrophysics Data System (ADS)

    Milewski, Jarosław; Bujalski, Wojciech; Lewandowski, Janusz

    2011-11-01

    Based on mathematical modeling and numerical simulations, applicativity of various biofuels on high temperature fuel cell performance are presented. Governing equations of high temperature fuel cell modeling are given. Adequate simulators of both solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) have been done and described. Performance of these fuel cells with different biofuels is shown. Some characteristics are given and described. Advantages and disadvantages of various biofuels from the system performance point of view are pointed out. An analysis of various biofuels as potential fuels for SOFC and MCFC is presented. The results are compared with both methane and hydrogen as the reference fuels. The biofuels are characterized by both lower efficiency and lower fuel utilization factors compared with methane. The presented results are based on a 0D mathematical model in the design point calculation. The governing equations of the model are also presented. Technical and financial analysis of high temperature fuel cells (SOFC and MCFC) are shown. High temperature fuel cells can be fed by biofuels like: biogas, bioethanol, and biomethanol. Operational costs and possible incomes of those installation types were estimated and analyzed. A comparison against classic power generation units is shown. A basic indicator net present value (NPV) for projects was estimated and commented.

  8. Feedback control of solid oxide fuel cell spatial temperature variation

    NASA Astrophysics Data System (ADS)

    Fardadi, Mahshid; Mueller, Fabian; Jabbari, Faryar

    A high performance feedback controller has been developed to minimize SOFC spatial temperature variation following significant load perturbations. For thermal management, spatial temperature variation along SOFC cannot be avoided. However, results indicate that feedback control can be used to manipulate the fuel cell air flow and inlet fuel cell air temperature to maintain a nearly constant SOFC electrode electrolyte assembly temperature profile. For example temperature variations of less than 5 K are obtained for load perturbations of ±25% from nominal. These results are obtained using a centralized control strategy to regulate a distributed temperature profile and manage actuator interactions. The controller is based on H-infinity synthesis using a physical based dynamic model of a single co-flow SOFC repeat cell. The model of the fuel cell spatial temperature response needed for control synthesis was linearized and reduced from nonlinear model of the fuel cell assembly. A single 11 state feedback linear system tested in the full nonlinear model was found to be effective and stable over a wide fuel cell operating envelope (0.82-0.6 V). Overall, simulation of the advanced controller resulted in small and smooth monotonic temperature response to rapid and large load perturbations. This indicates that future SOFC systems can be designed and controlled to have superb load following characteristic with less than previously expected thermal stresses.

  9. Effects of Fuel Temperature on Injection Process and Combustion of Dimethyl Ether Engine.

    PubMed

    Guangxin, Gao; Zhulin, Yuan; Apeng, Zhou; Shenghua, Liu; Yanju, Wei

    2013-12-01

    To investigate the effects of fuel temperature on the injection process in the fuel-injection pipe and the combustion characteristics of compression ignition (CI) engine, tests on a four stroke, direct injection dimethyl ether (DME) engine were conducted. Experimental results show that as the fuel temperature increases from 20 to 40 °C, the sound speed is decreased by 12.2%, the peak line pressure at pump and nozzle sides are decreased by 7.2% and 5.6%, respectively. Meanwhile, the injection timing is retarded by 2.2 °CA and the injection duration is extended by 0.8 °CA. Accordingly, the ignition delay and the combustion duration are extended by 0.7 °CA and 4.0 °CA, respectively. The cylinder peak pressure is decreased by 5.4%. As a result, the effective thermal efficiency is decreased, especially for temperature above 40 °C. Before beginning an experiment, the fuel properties of DME, including the density, the bulk modulus, and the sound speed were calculated by "ThermoData." The calculated result of sound speed is consistent with the experimental results. PMID:23918238

  10. Temperature Profile in Fuel and Tie-Tubes for Nuclear Thermal Propulsion Systems

    SciTech Connect

    Vishal Patel

    2015-02-01

    A finite element method to calculate temperature profiles in heterogeneous geometries of tie-tube moderated LEU nuclear thermal propulsion systems and HEU designs with tie-tubes is developed and implemented in MATLAB. This new method is compared to previous methods to demonstrate shortcomings in those methods. Typical methods to analyze peak fuel centerline temperature in hexagonal geometries rely on spatial homogenization to derive an analytical expression. These methods are not applicable to cores with tie-tube elements because conduction to tie-tubes cannot be accurately modeled with the homogenized models. The fuel centerline temperature directly impacts safety and performance so it must be predicted carefully. The temperature profile in tie-tubes is also important when high temperatures are expected in the fuel because conduction to the tie-tubes may cause melting in tie-tubes, which may set maximum allowable performance. Estimations of maximum tie-tube temperature can be found from equivalent tube methods, however this method tends to be approximate and overly conservative. A finite element model of heat conduction on a unit cell can model spatial dependence and non-linear conductivity for fuel and tie-tube systems allowing for higher design fidelity of Nuclear Thermal Propulsion.

  11. Method and apparatus for determining peak temperature along an optical fiber

    DOEpatents

    Fox, Richard J.

    1985-01-01

    The invention relates to a new method and new apparatus for determining the hottest temperature or the coldest temperature prevailing along the length of an optical-fiber light guide. The invention is conducted with an optical fiber capable of supporting multidiode propagation of light and comprising a core, a cladding, and a jacket. The core is selected to have (1) a higher refractive index than the core and the cladding and (2) a relatively high negative temperature coefficient of refractive index. A light beam capable of establishing substantially single-mode propagation in the core is launched into an end thereof at an angle to the axis. The angle is increased to effect the onset of light refraction from the core into the cladding. The value of the launch angle corresponding to the onset is determined and then used to establish the refractive index of the core corresponding to the onset angle. The maximum temperature prevailing along the fiber then is determined from the (1) refractive index so determined and (2) the temperature coefficient of refractive index for the core. The invention is based on the finding that the launch angle corresponding to the onset of refraction into the cladding is uniquely determined by the maximum value of the ratio of the core refractive index to the cladding refractive index, which maximum occurs at the hottest point along the fiber.

  12. Method and apparatus for determining peak temperature along an optical fiber

    DOEpatents

    Fox, R.J.

    1982-07-29

    The invention relates to a new method and new apparatus for determining the hottest temperature or the coldest temperature prevailing along the length of an optical-fiber light guide. The invention is conducted with an optical fiber capable of supporting multidiode propagation of light and comprising a core, a cladding, and a jacket. The core is selected to have (1) a higher refractive index than the core and the cladding and (2) a relatively high negative temperature coefficient of refractive index. A light beam capable of establishing substantially single-mode propagation in the core is launched into an end thereof at an angle to the axis. The angle is increased to effect the onset of light fraction from the core into the cladding. The value of the launch angle corresponding to the onset is determined and then used to establish the refractive index of the core corresponding to the onset angle. The maximum temperature prevailing along the fiber then is determined from the (1) refractive index so determined and (2) the temperature coefficient of refractive index for the core. The invention is based on the finding that the launch angle corresponding to the onset of refraction into the cladding is uniquely determined by the maximum value of the ratio of the core refractive index to the cladding refractive index, which maximum occurs at the hottest point along the fiber.

  13. The low-temperature partial-oxidation reforming of fuels for transportation fuel cell systems

    SciTech Connect

    Kumar, R.; Ahmed, S.; Krumpelt, M.

    1996-12-31

    Passenger cars powered by fuel cell propulsion systems with high efficiency offer superior fuel economy, very low to zero pollutant emissions, and the option to operate on alternative and/or renewable fuels. Although the fuel cell operates on hydrogen, a liquid fuel such as methanol or gasoline is more attractive for automotive use because of the convenience in handling and vehicle refueling. Such a liquid fuel must be dynamically converted (reformed) to hydrogen on board the vehicle in real time to meet fluctuating power demands. This paper describes the low-temperature Argonne partial-oxidation reformer (APOR) developed for this application. The APOR is a rapid-start, compact, lightweight, catalytic device that is efficient and dynamically responsive. The reformer is easily controlled by varying the feed rates of the fuel, water, and air to satisfy the rapidly changing system power demands during the vehicle`s driving cycle.

  14. Advanced anodes for high-temperature fuel cells.

    PubMed

    Atkinson, A; Barnett, S; Gorte, R J; Irvine, J T S; McEvoy, A J; Mogensen, M; Singhal, S C; Vohs, J

    2004-01-01

    Fuel cells will undoubtedly find widespread use in this new millennium in the conversion of chemical to electrical energy, as they offer very high efficiencies and have unique scalability in electricity-generation applications. The solid-oxide fuel cell (SOFC) is one of the most exciting of these energy technologies; it is an all-ceramic device that operates at temperatures in the range 500-1,000 degrees C. The SOFC offers certain advantages over lower temperature fuel cells, notably its ability to use carbon monoxide as a fuel rather than being poisoned by it, and the availability of high-grade exhaust heat for combined heat and power, or combined cycle gas-turbine applications. Although cost is clearly the most important barrier to widespread SOFC implementation, perhaps the most important technical barriers currently being addressed relate to the electrodes, particularly the fuel electrode or anode. In terms of mitigating global warming, the ability of the SOFC to use commonly available fuels at high efficiency, promises an effective and early reduction in carbon dioxide emissions, and hence is one of the lead new technologies for improving the environment. Here, we discuss recent developments of SOFC fuel electrodes that will enable the better use of readily available fuels. PMID:14704781

  15. Advanced Anodes for High-Temperature Fuel Cells

    SciTech Connect

    Atkinson, Alan; Barnett, Scott A.; Gorte, Raymond J.; Irvine, John T.; McEvoy, Augustin J.; Mogensen, Mogens; Singhal, Subhash C.; Vohs, John M.

    2004-01-04

    Fuel cells will undoubtedly find widespread use in this new millenium in the conversion of chemical to electrical energy, as they offer very high efficiencies and have unique scalability in electricity-generation applications. The solid-oxide fuel cell (SOFC) is one of the most exciting of these energy technologies; it is an all-ceramic device that operates at temperatures in the range 500-1000 C. The SOFC offers certain advantages over lower temperature fuel cells, notably its ability to use carbon monoxide as a fuel rather than being poisoned by it, and the availability of high-grade exhaust heat for combined heat and power, or combined cycle gas-turbine applications. Although cost is clearly the most important barrier to widespread SOFC implementation, perhaps the most important technical barriers currently being addressed relate to the electrodes, particularly the fuel electrode or anode. In terms of mitigating global warming, the ability of the SOFC to use commonly available fuels at high efficiency promises an effective and early reduction in carbon dioxide emissions and,hence, is one of the lead new technologies for improving the environment. Here, we discuss recent developments of SOFC fuel electrodes that will enable the better use of readily available fuels.

  16. Comment on "Origin of low-temperature shoulder internal friction peak of Snoek-Köster peak in a medium carbon high alloyed steel" by Lu et al. [Solid State Communications 195 (2014) 31

    NASA Astrophysics Data System (ADS)

    Hoyos, J. J.; Mari, D.

    2016-01-01

    We want to discuss the interpretation of low-temperature shoulder internal friction peak of Snoek-Köster peak (LTS-SK). Lu et al. (2015) [1] attributed it to the interaction between the carbon atoms and twin boundaries in martensite. Nevertheless, the decrease of the amplitude of LTS-SK peak due to carbon segregation is correlated with the interstitial carbon content in solid solution in martensite (Hoyos et al., 2015 [2]). Therefore, this peak can also be attributed to the presence of an internal friction athermal background, which is proportional to the concentration of interstitial carbon in solid solution (Tkalcec et al., 2015 [2,3]). In addition, they used an alloyed steel, in which ε carbide precipitated above of the LTS-SK peak temperature. As this behavior cannot be generalized for carbon and high alloyed steels, the carbide precipitates could made an additional contribution to the internal friction.

  17. Materials for Intermediate-Temperature Solid-Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Kilner, John A.; Burriel, Mónica

    2014-07-01

    Solid-oxide fuel cells are devices for the efficient conversion of chemical energy to electrical energy and heat. Research efforts are currently addressed toward the optimization of cells operating at temperatures in the region of 600°C, known as intermediate-temperature solid-oxide fuel cells, for which materials requirements are very stringent. In addition to the requirements of mechanical and chemical compatibility, the materials must show a high degree of oxide ion mobility and electrochemical activity at this low temperature. Here we mainly examine the criteria for the development of two key components of intermediate-temperature solid-oxide fuel cells: the electrolyte and the cathode. We limit the discussion to novel approaches to materials optimization and focus on the fluorite oxide for electrolytes, principally those based on ceria and zirconia, and on perovskites and perovskite-related families in the case of cathodes.

  18. Fuel temperature reactivity coefficient calculation by Monte Carlo perturbation techniques

    SciTech Connect

    Shim, H. J.; Kim, C. H.

    2013-07-01

    We present an efficient method to estimate the fuel temperature reactivity coefficient (FTC) by the Monte Carlo adjoint-weighted correlated sampling method. In this method, a fuel temperature change is regarded as variations of the microscopic cross sections and the temperature in the free gas model which is adopted to correct the asymptotic double differential scattering kernel. The effectiveness of the new method is examined through the continuous energy MC neutronics calculations for PWR pin cell problems. The isotope-wise and reaction-type-wise contributions to the FTCs are investigated for two free gas models - the constant scattering cross section model and the exact model. It is shown that the proposed method can efficiently predict the reactivity change due to the fuel temperature variation. (authors)

  19. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120...

  20. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120...

  1. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120...

  2. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120...

  3. 40 CFR 1065.120 - Fuel properties and fuel temperature and pressure.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Fuel properties and fuel temperature and pressure. 1065.120 Section 1065.120 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Equipment Specifications § 1065.120...

  4. Weekly cycles in peak time temperatures and urban heat island intensity

    NASA Astrophysics Data System (ADS)

    Earl, Nick; Simmonds, Ian; Tapper, Nigel

    2016-07-01

    Regular diurnal and weekly cycles (WCs) in temperature provide valuable insights into the consequences of anthropogenic activity on the urban environment. Different locations experience a range of identified WCs and have very different structures. Two important sources of urban heat are those associated with the effect of large urban structures on the radiation budget and energy storage and those from the heat generated as a consequence of anthropogenic activity. The former forcing will remain relatively constant, but a WC will appear in the latter. WCs for specific times of day and the urban heat island (UHI) have not been analysed heretofore. We use three-hourly surface (2 m) temperature data to analyse the WCs of seven major Australian cities at different times of day and to determine to what extent one of our major city’s (Melbourne) UHI exhibits a WC. We show that the WC of temperature in major cities differs according to the time of day and that the UHI intensity of Melbourne is affected on a WC. This provides crucial information that can contribute toward the push for healthier urban environments in the face of a more extreme climate.

  5. Temperature characteristics for PTC material heating diesel fuel

    NASA Astrophysics Data System (ADS)

    Gu, Lefeng; Li, Xiaolu; Wang, Jun; Li, Ying; Li, Ming

    2010-08-01

    This paper gives a way which utilizes the PTC (Positive Temperature Coefficient) material to preheat diesel fuel in the injector in order to improve the cold starting and emissions of engine. A new injector is also designed. In order to understand the preheating process in this new injector, a dynamic temperature testing system combined with the MSP430F149 data acquisition system is developed for PTC material heating diesel fuel. Especially, the corresponding software and hardware circuits are explained. The temperature of diesel fuel preheating by PTC ceramics is measured under different voltages and distances, which Curie point is 75 °C. Diesel fuel is heated by self-defined temperature around the Curie point of PTC ceramics. The diesel fuel temperature rises rapidly in 2 minutes of the beginning, then can reach 60 °C within 5 minutes as its distance is 5mm away from the surface of PTC ceramics. However, there are a lot of fundamental studies and technology to be resolved in order to apply PTC material in the injector successfully.

  6. Measurement of the D-D fusion neutron energy spectrum and variation of the peak width with plasma ion temperature

    NASA Astrophysics Data System (ADS)

    Fisher, W. A.; Chen, S. H.; Gwinn, D.; Parker, R. R.

    1983-11-01

    We report a set of neutron spectrum measurements made at the Alcator-C tokamak under Ohmic-heating conditions. It has been found that the width of the D-D fusion neutron peak increases with the plasma ion temperature consistent with the theoretical prediction. In particular, the neutron spectra resulting from the sum of many plasma discharges with ion temperatures of 780 and 1050 eV have been obtained. The width for the 780-eV case is 64+ 9-11 keV and that of the 1050-eV case, 81+10-14 keV (full width at half maximum), corresponding to ion temperatures of 740 and 1190 eV, respectively.

  7. Li zoning in zircon as a potential geospeedometer and peak temperature indicator

    NASA Astrophysics Data System (ADS)

    Trail, Dustin; Cherniak, Daniele J.; Watson, E. Bruce; Harrison, T. Mark; Weiss, Benjamin P.; Szumila, Ian

    2016-03-01

    Zircon Li concentrations and δ7Li values may potentially trace crustal recycling because continental and mantle-derived zircons yield distinct values. The usefulness of these differences may depend upon the retentivity of zircon to Li concentrations and isotopic ratios. Given the relatively high Li diffusivities measured by Cherniak and Watson (Contrib Mineral Petrol 160: 383-390, 2010), we sought to discover the scenarios under which Li mobility might be inhibited by charge-compensating cations. Toward this end, we conducted "in" diffusion experiments in which Li depth profiles of synthetic Lu-doped, P-doped, and undoped zircon were determined by nuclear reaction analysis. In separate experiments, Li was ion-implanted at depth within polished natural zircon slabs to form a Gaussian Li concentration profile. Diffusively relaxed concentration profiles were measured after heating the slabs to determine diffusivities. In all experiments, which ranged from 920 to 650 °C, calculated diffusivities are in agreement with a previously established Arrhenius relationship calibrated on trace-element-poor Mud Tank zircon. Our revised Arrhenius relationship that includes both datasets is: D_{Li} = 9.60 × 10^{ - 7} exp [ {{ - 278 ± 8{{kJ}/{mol}^{ - 1} }}{RT}} ]{m}^{ 2} {{s}}^{ - 1} We also observed that synthetic sector-zoned zircon exhibits near-step-function Li concentration profiles across sectors that correlate with changes in the rare earth element (REE) and P concentrations. This allowed us to examine how Li diffusion might couple with REE diffusion in a manner different than that described above. In particular, re-heating these grains revealed significant Li migration, but no detectable migration of the rare earth elements. Thus, unlike most elements in zircon which are not mobile at the micrometer scale under most time-temperature paths in the crust, Li zoning, relaxation of zoning, or lack of zoning altogether could be used to reveal time-temperature information

  8. Formation of monitoring and evening electron temperature peaks in the low latitude F region during 19-21 March 1988

    NASA Astrophysics Data System (ADS)

    Pavlov, A. V.; Fukao, S.; Kawamura, S.

    A comparison between the election, T_e, and ion, T_i, temperatures measured by the middle and upper atmosphere (MU) radar Shigaraki (34.85° N, 136.10° E, Japan) and those produced by the model of the ionosphere and plasmasphere is presented for 19-21 March 1988. We compare the modeled NmF2 and hmF2 with those observed bz the Akita, Kokubunji, Yamagawa,Okinawa, Chung-Li, Manila, Vanimo, and Darwin sounders and by the MU radar during the the 19-21 March 1988 geomagnetically quiet time period near 201° geomagnetic longitude. The variations of T_e are characterized by morning and evening peaks over the Darwin Yamagawa, Kokubunji and Akita ionosonde stations and over the MU radar while the model produces morning and daytime peaks in T_e above the Vanimo, Manila, Chung-Li, and Okinawa, ionosonde stations. There is a rapid heating of daytime electrons by photoelectrons, and the difference between T_e and T_i is increased after sunrise because the night-time electron density, N_e, is less than that by day, and the resulting electron cooling is less than that by day. After the abrupt morning increase, T_e decreases due to the electron cooling increase caused by the increase in N_e. We found that the night-time downward ExB drift causes the decrease in NmF2 before sunrise and the resulting increase in the magnitude, of the T_e morning peak. This plasma drift becomes more effective in lowering N_e with lowering the geomagnetic latitude, ϕ, i. e. the decrease in |ϕ| leads to the decrease in the night-time N_e before sunrise and the resulting increase in the magnitude of the morning T_e peak. The effect of the plasma drift, W, due to the neutral wind on the formation of the morning T_e peak is decreased with lowering ϕ. The increase in |ϕ| leads to the increase of the effect to the night-time W on N_e, the increase in the night-time N_e before sunrise, and the resulting decrease in the morning T_e peak, created by an evening N_e decrease, becomes strong. The decrease in

  9. Gain-guided broad area quantum cascade lasers emitting 23.5 W peak power at room temperature.

    PubMed

    Sergachev, Ilia; Maulini, Richard; Bismuto, Alfredo; Blaser, Stephane; Gresch, Tobias; Muller, Antoine

    2016-08-22

    We report gain-guided broad area quantum cascade lasers at 4.55 μm. The devices were processed in a buried heterostructure configuration with a current injector section much narrower than the active region. They demonstrate 23.5 W peak power at a temperature of 20°C and duty cycle of 1%, while their far field consists of a single symmetric lobe centered on the optical axis. These experimental results are supported well by 2D numerical simulations of electric currents and optical fields in a device cross-section. PMID:27557186

  10. Platinum-based nanocomposite electrodes for low-temperature solid oxide fuel cells with extended lifetime

    NASA Astrophysics Data System (ADS)

    Lee, Yoon Ho; Cho, Gu Young; Chang, Ikwhang; Ji, Sanghoon; Kim, Young Beom; Cha, Suk Won

    2016-03-01

    Due to its high catalytic activity and convenient fabrication procedure that uses physical vapor deposition (PVD), nanofabricated platinum (Pt) is widely used for low temperature operating solid oxide fuel cells (LT-SOFC). However, the poor thermal stability of nanofabricated Pt accelerates cell performance degradation. To solve this problem, we apply a thermal barrier coating and use the dispersion hardening process for the nanofabrication of Pt by sputter device. Through morphological and electrochemical data, GDC modified nano-porous Pt electrodes shows improved performance and thermal stability at the operating temperature of 500 °C. While the peak power density of pure Pt sample is 6.16 mW cm-2 with a performance degradation of 43% in an hour, the peak power density of the GDC modified Pt electrodes are in range of 7.42-7.91 mW cm-2 with a 7-16% of performance degradation.

  11. High temperature solid oxide fuel development activities

    SciTech Connect

    Ray, E.R.

    1993-11-01

    This paper presents an overview of the Westinghouse tubular SOFC development activities and current program status. Goal is to develop a cell that can operate for 50,000 to 100,000 h. Test results are presented for multiple single cell tests which have now successfully exceeded 40,000 hours of continuous power operation at temperature. Two 25-kW SOFC customer tests units were delivered in 1992; a 20-kW SOFC system is bein manufactured and will be operated by Southern California Edison in 1995. Megawatt class generators are being developed.

  12. Behaviour of irradiated PHWR fuel pins during high temperature heating

    NASA Astrophysics Data System (ADS)

    Viswanathan, U. K.; Unnikrishnan, K.; Mishra, Prerna; Banerjee, Suparna; Anantharaman, S.; Sah, D. N.

    2008-12-01

    Fuel pins removed from an irradiated pressurised heavy water reactor (PHWR) fuel bundle discharged after an extended burn up of 15,000 MWd/tU have been subjected to isothermal heating tests in temperature range 700-1300 °C inside hot-cells. The heating of the fuel pins was carried out using a specially designed remotely operable furnace, which allowed localized heating of about 100 mm length of the fuel pin at one end under flowing argon gas or in air atmosphere. Post-test examination performed in the hot-cells included visual examination, leak testing, dimension measurement and optical and scanning electron microscopy. Fuel pins having internal pressure of 2.1-2.7 MPa due to fission gas release underwent ballooning and micro cracking during heating for 10 min at 800 °C and 900 °C but not at 700 °C. Fuel pin heated at 1300 °C showed complete disruption of cladding in heating zone, due to the embrittlement of the cladding. The examination of fuel from the pin tested at 1300 °C showed presence of large number of bubbles; both intragranular as well as intergranular bubbles. Details of the experiments and the results are presented in this paper.

  13. Handling Temperature Bursts Reaching 464°C: Different Microbial Strategies in the Sisters Peak Hydrothermal Chimney

    PubMed Central

    Kurtz, Stefan; LaRoche, Julie

    2014-01-01

    The active venting Sisters Peak (SP) chimney on the Mid-Atlantic Ridge holds the current temperature record for the hottest ever measured hydrothermal fluids (400°C, accompanied by sudden temperature bursts reaching 464°C). Given the unprecedented temperature regime, we investigated the biome of this chimney with a focus on special microbial adaptations for thermal tolerance. The SP metagenome reveals considerable differences in the taxonomic composition from those of other hydrothermal vent and subsurface samples; these could be better explained by temperature than by other available abiotic parameters. The most common species to which SP genes were assigned were thermophilic Aciduliprofundum sp. strain MAR08-339 (11.8%), Hippea maritima (3.8%), Caldisericum exile (1.5%), and Caminibacter mediatlanticus (1.4%) as well as to the mesophilic Niastella koreensis (2.8%). A statistical analysis of associations between taxonomic and functional gene assignments revealed specific overrepresented functional categories: for Aciduliprofundum, protein biosynthesis, nucleotide metabolism, and energy metabolism genes; for Hippea and Caminibacter, cell motility and/or DNA replication and repair system genes; and for Niastella, cell wall and membrane biogenesis genes. Cultured representatives of these organisms inhabit different thermal niches; i.e., Aciduliprofundum has an optimal growth temperature of 70°C, Hippea and Caminibacter have optimal growth temperatures around 55°C, and Niastella grows between 10 and 37°C. Therefore, we posit that the different enrichment profiles of functional categories reflect distinct microbial strategies to deal with the different impacts of the local sudden temperature bursts in disparate regions of the chimney. PMID:24837379

  14. Temperature and burnup correlated fuel-cladding chemical interaction in U-10ZR metallic fuel

    NASA Astrophysics Data System (ADS)

    Carmack, William J.

    Metallic fuels are proposed for use in advanced sodium cooled fast reactors and provide a number of advantages over other fuel types considering their fabricability, performance, recyclability, and safety. Resistance to cladding "breach" and subsequent release of fission products and fuel constituents to the nuclear power plant primary coolant system is a key performance parameter for a nuclear fuel system. In metallic fuel, FCCI weakens the cladding, especially at high power-high temperature operation, contributing to fuel pin breach. Empirical relationships for FCCI have been developed from a large body of data collected from in-pile (EBR-II) and out-of-pile experiments [1]. However, these relationships are unreliable in predicting FCCI outside the range of EBR-II experimental data. This dissertation examines new FCCI data extracted from the MFF-series of prototypic length metallic fuel irradiations performed in the Fast Flux Test Facility (FFTF). The fuel in these assemblies operated a temperature and burnup conditions similar to that in EBR-II but with axial fuel height three times longer than EBR-II experiments. Comparing FCCI formation data from FFTF and EBR-II provides new insight into FCCI formation kinetics. A model is developed combining both production and diffusion of lanthanides to the fuel-cladding interface and subsequent reaction with the cladding. The model allows these phenomena to be influenced by fuel burnup (lanthanide concentrations) and operating temperature. Parameters in the model are adjusted to reproduce measured FCCI layer thicknesses from EBR-II and FFTF. The model predicts that, under appropriate conditions, rate of FCCI formation can be controlled by either fission product transport or by the reaction rate of the interaction species at the fuel-cladding interface. This dissertation will help forward the design of metallic fuel systems for advanced sodium cooled fast reactors by allowing the prediction of FCCI layer formation in full

  15. Improvements to the RELAP5/MOD3 reflood model and uncertainty quantification of reflood peak clad temperature

    SciTech Connect

    Chung, Bub Dong; Lee, Young Lee; Park, Chan Eok; Lee, Sang Yong

    1996-10-01

    Assessment of the original REAP/N4OD3.1 code against the FLECHT SEASET series of experiments has identified some weaknesses of the reflood model, such as the lack of a quenching temperature model, the shortcoming of the Chen transition boiling model, and the incorrect prediction of droplet size and interfacial heat transfer. Also, high temperature spikes during the reflood calculation resulted in high steam flow oscillation and liquid carryover. An effort had been made to improve the code with respect to the above weakness, and the necessary model for the wall heat transfer package and the numerical scheme had been modified. Some important FLECHT-SEASET experiments were assessed using the improved version and standard version. The result from the improved REAP/MOD3.1 shows the weaknesses of REAP/N4OD3.1 were much improved when compared to the standard MOD3.1 code. The prediction of void profile and cladding temperature agreed better with test data, especially for the gravity feed test. The scatter diagram of peak cladding temperatures (PCTs) is made from the comparison of all the calculated PCTs and the corresponding experimental values. The deviation between experimental and calculated PCTs were calculated for 2793 data points. The deviations are shown to be normally distributed, and used to quantify statistically the PCT uncertainty of the code. The upper limit of PCT uncertainty at 95% confidence level is evaluated to be about 99K.

  16. Immobilization of imidazole moieties in polymer electrolyte composite membrane for elevated temperature fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Ke; Zhou, Bei; Ye, Gongbo; Pan, Mu; Zhang, Haining

    2015-12-01

    Development of membrane electrolyte with reasonable proton conductivity at elevated temperature without external humidification is essential for practical applications of elevated temperature proton exchange membrane fuel cells. Herein, a novel polymer electrolyte composite membrane using imidazole as anhydrous proton carriers for elevated temperature fuel cells is investigated. The imidazole moieties are immobilized inside the Nafion/poly(tetrafluoroethylene) (PTFE) composite membrane through in situ formation of imidazole functionalized silica nanoparticles in Nafion dispersion. The thus-formed membrane exhibits strong Coulombic interaction between negatively charged sulfonic acid groups of Nafion and protonated imidazole moieties, leading to an anhydrous proton conductivity of 0.018 S cm-1 at 180 °C. With the introduction of PTFE matrix, the mechanical strength of the membrane is greatly improved. The peak power density of a single cell assembled from the hybrid membrane is observed to be 130 mW cm-2 under 350 mA cm-2 at 110 °C without external humidification and it remains stable for 20 h continuous operation. The obtained results demonstrate that the developed composite membranes could be utilized as promising membrane electrolytes for elevated temperature fuel cells.

  17. Carbon dioxide separation from high temperature fuel cell power plants

    NASA Astrophysics Data System (ADS)

    Campanari, Stefano

    High temperature fuel cell technologies, solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs), are considered for their potential application to carbon dioxide emission control. Both technologies feature electrochemical oxidisation of natural gas reformed fuels, avoiding the mixture of air and fuel flows and dilution with nitrogen and oxygen of the oxidised products; a preliminary analysis shows how the different mechanism of ion transport attributes each technology a specific advantage for the application to CO 2 separation. The paper then compares in the first part the most promising cycle configurations based on high efficiency integrated SOFC/gas turbine "hybrid" cycles, where CO 2 is separated with absorption systems or with the eventual adoption of a second SOFC module acting as an "afterburner". The second part of the paper discusses how a MCFC plant could be "retrofitted" to a conventional fossil-fuel power station, giving the possibility of draining the majority of CO 2 from the stack exhaust while keeping the overall cycle electrical efficiency approximately unchanged.

  18. Engineered Nanostructured MEA Technology for Low Temperature Fuel Cells

    SciTech Connect

    Zhu, Yimin

    2009-07-16

    The objective of this project is to develop a novel catalyst support technology based on unique engineered nanostructures for low temperature fuel cells which: (1) Achieves high catalyst activity and performance; (2) Improves catalyst durability over current technologies; and (3) Reduces catalyst cost. This project is directed at the development of durable catalysts supported by novel support that improves the catalyst utilization and hence reduce the catalyst loading. This project will develop a solid fundamental knowledge base necessary for the synthetic effort while at the same time demonstrating the catalyst advantages in Direct Methanol Fuel Cells (DMFCs).

  19. In-flight and simulated aircraft fuel temperature measurements

    NASA Technical Reports Server (NTRS)

    Svehla, Roger A.

    1990-01-01

    Fuel tank measurements from ten flights of an L1011 commercial aircraft are reported for the first time. The flights were conducted from 1981 to 1983. A thermocouple rake was installed in an inboard wing tank and another in an outboard tank. During the test periods of either 2 or 5 hr, at altitudes of 10,700 m (35,000 ft) or higher, either the inboard or the outboard tank remained full. Fuel temperature profiles generally developed in the expected manner. The bulk fuel was mixed by natural convection to a nearly uniform temperature, especially in the outboard tank, and a gradient existed at the bottom conduction zone. The data indicated that when full, the upper surface of the inboard tank was wetted and the outboard tank was unwetted. Companion NASA Lewis Research Center tests were conducted in a 0.20 cubic meter (52 gal) tank simulator of the outboard tank, chilled on the top and bottom, and insulated on the sides. Even though the simulator tank had no internal components corresponding to the wing tank, temperatures agreed with the flight measurements for wetted upper surface conditions, but not for unwetted conditions. It was concluded that if boundary conditions are carefully controlled, simulators are a useful way of evaluating actual flight temperatures.

  20. Peak-Seeking Control For Reduced Fuel Consumption: Flight-Test Results For The Full-Scale Advanced Systems Testbed FA-18 Airplane

    NASA Technical Reports Server (NTRS)

    Brown, Nelson

    2013-01-01

    A peak-seeking control algorithm for real-time trim optimization for reduced fuel consumption has been developed by researchers at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center to address the goals of the NASA Environmentally Responsible Aviation project to reduce fuel burn and emissions. The peak-seeking control algorithm is based on a steepest-descent algorithm using a time-varying Kalman filter to estimate the gradient of a performance function of fuel flow versus control surface positions. In real-time operation, deflections of symmetric ailerons, trailing-edge flaps, and leading-edge flaps of an F/A-18 airplane are used for optimization of fuel flow. Results from six research flights are presented herein. The optimization algorithm found a trim configuration that required approximately 3 percent less fuel flow than the baseline trim at the same flight condition. This presentation also focuses on the design of the flight experiment and the practical challenges of conducting the experiment.

  1. High temperature dilatometry of simulated oxide nuclear fuel

    NASA Astrophysics Data System (ADS)

    Tenishev, A. V.; Baranov, V. G.; Kuzmin, R. S.; Pokrovskiy, S. A.

    2016-04-01

    High temperature dilatometry of model systems based on uranium dioxide with additives of burnable neutron absorbers both as Gd2O3 and as AlGdO3, and fission products simulators (FPS) was performed. It shown that in some cases instead of high temperature samples shrinkage there is a sharp transition to the expansion, which is associated with an increase of the samples volume due to the formation of liquid phases. The beginning of a complex composition eutectic melting starts at temperatures from 1950 to 2250 °C in the uranium dioxide samples containing significant amounts of Al, Gd, and FPS. Thus, in the analysis of oxide nuclear fuel behavior at high temperatures should be considered that the formation of liquid phases is possible at a temperature of 1000 °C lower than a melting point of pure stoichiometric uranium dioxide if its initial composition became more complex.

  2. High performance internal reforming unit for high temperature fuel cells

    DOEpatents

    Ma, Zhiwen; Venkataraman, Ramakrishnan; Novacco, Lawrence J.

    2008-10-07

    A fuel reformer having an enclosure with first and second opposing surfaces, a sidewall connecting the first and second opposing surfaces and an inlet port and an outlet port in the sidewall. A plate assembly supporting a catalyst and baffles are also disposed in the enclosure. A main baffle extends into the enclosure from a point of the sidewall between the inlet and outlet ports. The main baffle cooperates with the enclosure and the plate assembly to establish a path for the flow of fuel gas through the reformer from the inlet port to the outlet port. At least a first directing baffle extends in the enclosure from one of the sidewall and the main baffle and cooperates with the plate assembly and the enclosure to alter the gas flow path. Desired graded catalyst loading pattern has been defined for optimized thermal management for the internal reforming high temperature fuel cells so as to achieve high cell performance.

  3. Gasoline Ultra Efficient Fuel Vehicle with Advanced Low Temperature Combustion

    SciTech Connect

    Confer, Keith

    2014-09-30

    The objective of this program was to develop, implement and demonstrate fuel consumption reduction technologies which are focused on reduction of friction and parasitic losses and on the improvement of thermal efficiency from in-cylinder combustion. The program was executed in two phases. The conclusion of each phase was marked by an on-vehicle technology demonstration. Phase I concentrated on short term goals to achieve technologies to reduce friction and parasitic losses. The duration of Phase I was approximately two years and the target fuel economy improvement over the baseline was 20% for the Phase I demonstration. Phase II was focused on the development and demonstration of a breakthrough low temperature combustion process called Gasoline Direct- Injection Compression Ignition (GDCI). The duration of Phase II was approximately four years and the targeted fuel economy improvement was 35% over the baseline for the Phase II demonstration vehicle. The targeted tailpipe emissions for this demonstration were Tier 2 Bin 2 emissions standards.

  4. Assessment of temperature peaks reached during a wildfire. An approach using X-ray diffraction and differential thermal analysis

    NASA Astrophysics Data System (ADS)

    Jiménez-González, Marco A.; Jordán, Antonio; Zavala, Lorena M.; Mataix-Solera, Jorge; Bárcenas-Moreno, Gema; Jiménez-Morillo, Nicasio T.; Bellinfante, Nicolás

    2014-05-01

    1. INTRODUCTION Wildfires may induce important chemical and physical changes in soils, including changes in the soil composition, mineralogical changes, soil water repellency, aggregate stability or textural changes (Bodí et al., 2013; Granged et al., 2011a, 2011b, 2011c; Jordán et al., 2011, 2013; Mataix-Solera et al., 2011). As these changes usually occur after threshold temperature peaks, the assessment of these helps to explain many of the processes occurring during burning and in the postfire (Pereira et al., 2012, 2013; Shakesby, 2011). In July 2011, a wildfire burnt a pine forested area (50 ha) in Gorga (Alicante, SW Spain), approximately at 38° 44.3' N and 0° 20.7' W. Main soil type is Lithic Xerorthent developed from limestone. The study of mineralogical changes in soil after a wildfire should help to assess fire temperature peaks reached during burning. In order to study the impact of fire temperature on mineralogical changes and determine temperature peaks during burning, burnt soil plots under shrubland were randomly collected (0-5 cm deep). Control samples from adjacent unburnt areas were also collected for control. 2. METHODS Soil samples were ground using an agate mortar and then sieved (< 0.002mm) and analyzed by X-ray diffraction (XRD). XRD was conducted on a Bruker (model D8 advance A25) powder θ:θ diffractometer, which uses a Cu anticathode (40KV, 30mA), Ni filter in the diffracted bean and lineal detector. Powder samples were scanned from 3 to 70° 2θ, using a step size of 0.015° 2θ and a scan speed of 0.15° 2θ s-1. Mineralogical phase identification and quantification of minerals was carried out with XPowder. In order to study other possible reaction in burnt soil, unburnt soil samples were exposed to temperatures of 300, 500 and 700 °C in a Mufla furnace during 20 minutes. Unburnt control and treated samples were analyzed by differential thermal analysis (DTA) and thermogravimetric analysis (TG). 3. RESULTS Diffractograms show that

  5. Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model

    NASA Technical Reports Server (NTRS)

    Friedman, R.; Stockemer, F. J.

    1980-01-01

    Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank, to simulate internal temperature gradients encountered in commercial airplane wing tanks. Two low-temperature situations were observed. Where the bulk of the fuel is above the specification freezing point, pumpout of the fuel removes all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depends on the fuel temperature near these surfaces. Where the bulk of the fuel is at or below the freezing point, pumpout ceases when solids block the pump inlet, and the unpumpable fraction depends on the overall average temperature.

  6. High Temperature Polymers for use in Fuel Cells

    NASA Technical Reports Server (NTRS)

    Peplowski, Katherine M.

    2004-01-01

    NASA Glenn Research Center (GRC) is currently working on polymers for fuel cell and lithium battery applications. The desire for more efficient, higher power density, and a lower environmental impact power sources has led to interest in proton exchanges membrane fuels cells (PEMFC) and lithium batteries. A PEMFC has many advantages as a power source. The fuel cell uses oxygen and hydrogen as reactants. The resulting products are electricity, heat, and water. The PEMFC consists of electrodes with a catalyst, and an electrolyte. The electrolyte is an ion-conducting polymer that transports protons from the anode to the cathode. Typically, a PEMFC is operated at a temperature of about 80 C. There is intense interest in developing a fuel cell membrane that can operate at higher temperatures in the range of 80 C- 120 C. Operating the he1 cell at higher temperatures increases the kinetics of the fuel cell reaction as well as decreasing the susceptibility of the catalyst to be poisoned by impurities. Currently, Nafion made by Dupont is the most widely used polymer membrane in PEMFC. Nafion does not function well above 80 C due to a significant decrease in the conductivity of the membrane from a loss of hydration. In addition to the loss of conductivity at high temperatures, the long term stability and relatively high cost of Nafion have stimulated many researches to find a substitute for Nafion. Lithium ion batteries are popular for use in portable electronic devices, such as laptop computers and mobile phones. The high power density of lithium batteries makes them ideal for the high power demand of today s advanced electronics. NASA is developing a solid polymer electrolyte that can be used for lithium batteries. Solid polymer electrolytes have many advantages over the current gel or liquid based systems that are used currently. Among these advantages are the potential for increased power density and design flexibility. Automobiles, computers, and cell phones require

  7. Very High Temperature Reactor (VHTR) Deep Burn Core and Fuel Analysis -- Complete Design Selection for the Pebble Bed Reactor

    SciTech Connect

    B. Boer; A. M. Ougouag

    2010-09-01

    The Deep-Burn (DB) concept focuses on the destruction of transuranic nuclides from used light water reactor fuel. These transuranic nuclides are incorporated into TRISO coated fuel particles and used in gas-cooled reactors with the aim of a fractional fuel burnup of 60 to 70% in fissions per initial metal atom (FIMA). This high performance is expected through the use of multiple recirculation passes of the fuel in pebble form without any physical or chemical changes between passes. In particular, the concept does not call for reprocessing of the fuel between passes. In principle, the DB pebble bed concept employs the same reactor designs as the presently envisioned low-enriched uranium core designs, such as the 400 MWth Pebble Bed Modular Reactor (PBMR-400). Although it has been shown in the previous Fiscal Year (2009) that a PuO2 fueled pebble bed reactor concept is viable, achieving a high fuel burnup, while remaining within safety-imposed prescribed operational limits for fuel temperature, power peaking and temperature reactivity feedback coefficients for the entire temperature range, is challenging. The presence of the isotopes 239-Pu, 240-Pu and 241-Pu that have resonances in the thermal energy range significantly modifies the neutron thermal energy spectrum as compared to a ”standard,” UO2-fueled core. Therefore, the DB pebble bed core exhibits a relatively hard neutron energy spectrum. However, regions within the pebble bed that are near the graphite reflectors experience a locally softer spectrum. This can lead to power and temperature peaking in these regions. Furthermore, a shift of the thermal energy spectrum with increasing temperature can lead to increased absorption in the resonances of the fissile Pu isotopes. This can lead to a positive temperature reactivity coefficient for the graphite moderator under certain operating conditions. The effort of this task in FY 2010 has focused on the optimization of the core to maximize the pebble discharge

  8. Improving low temperature properties of synthetic diesel fuels derived from oil shale. Alternative fuels utilization program

    SciTech Connect

    Frankenfeld, J.W.; Taylor, W.F.

    1980-11-01

    The ability of additives to improve the cold flow properties of shale oil derived fuels boiling in the diesel fuel range was evaluated. Because a commercial shale oil industry did not exist to provide actual samples of finished fuels, a representative range of hydroprocessed shale oil fractions was prepared for use in the additive testing work. Crude oil shale from Occidental Shale Company was fractionated to give three liquids in the diesel fuel boiling range. The initial boiling point in each case was 325/sup 0/F (163/sup 0/C). The final boiling points were 640/sup 0/F (338/sup 0/C), 670/sup 0/F (354/sup 0/C) and 700/sup 0/F (371/sup 0/F). Each fraction was hydrotreated to three different severities (800, 1200 and 1500 psi total pressure) over a Shell 324 nickel molybdate on alumina catalyst at 710 to 750/sup 0/F to afford 9 different model fuels. A variety of commercial and experimental additives were evaluated as cold flow improvers in the model fuels at treat levels of 0.04 to 0.4 wt %. Both the standard pour point test (ASTM D97) and a more severe low temperature flow test (LTFT) were employed. Reductions in pour points of up to 70/sup 0/F and improvements in LTFT temperatures up to 16/sup 0/F were achieved. It is concluded that flow improver additives can play an important role in improving the cold flow properties of future synthetic fuels of the diesel type derived from oil shale.

  9. High temperature seals for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Parihar, Shailendra S.

    Solid Oxide Fuel cells (SOFCs) represent a clean and efficient alternative to existing methods of energy production. But, they need hermetic seals to prevent fuel-oxidant mixing within the stack. Glasses are attractive options for fabrication of these high temperature seals but suffer from their inherent brittleness and tend to crack during thermal cycling. In this study, an innovative concept of self-healing glass seals is developed to solve the problem of cracking of glasses in a SOFC seal. Rationale behind this concept is that a glass of suitable viscosity characteristics can flow and heal cracks at SOFC operating temperatures and thus can provide seals which can self-repair. A novel method, based on in-situ video imaging of cracks on the glass surface during high temperature treatment is developed and used to select and evaluate the suitability of different glasses for making self-healing seals. Promising glasses are studied experimentally to determine kinetics of healing of Vickers indented cracks at various temperatures. In addition, the effect of crystallization of glass on its healing kinetics is studied. A model is developed for crack healing behavior and is used to validate the experimental data. Studies on Cracks healing and crystallization of glasses showed that glasses with no crystallization tendency show fast crack healing response, whereas glasses which crystallize display sluggish healing. A glass displaying fast healing kinetics and good stability against crystallization is used to fabricate self healing glass seals for SOFCs. Seals fabricated using this glass not only remained hermetic but also maintained their self i healing ability for as long as 3000 hours at 800°C and 300 thermal cycles between room temperature and 800°C. These results clearly indicated that self-healing glasses are promising candidates for SOFC seals. Key words. Solid Oxide Fuel Cells, Glass Seals, Self-Healing Glasses, Seal Leak Testing.

  10. Temperature peaking at beginning of breakdown in 2.45 GHz pulsed off-resonance electron cyclotron resonance ion source hydrogen plasma

    SciTech Connect

    Cortazar, O. D.

    2012-10-15

    An experimental study of temperature and density evolution during breakdown in off-resonance ECR hydrogen plasma is presented. Under square 2.45 GHz microwave excitation pulses with a frequency of 50 Hz and relative high microwave power, unexpected transient temperature peaks that reach 18 eV during 20 {mu}s are reported at very beginning of plasma breakdown. Decays of such peaks reach final stable temperatures of 5 eV at flat top microwave excitation pulse. Evidence of interplay between incoming power and duty cycle giving different kind of plasma parameters evolutions engaged to microwave coupling times is observed. Under relative high power conditions where short microwave coupling times are recorded, high temperature peaks are measured. However, for lower incoming powers and longer coupling times, temperature evolves gradually to a higher final temperature without peaking. On the other hand, the early instant where temperature peaks are observed also suggest a possible connection with preglow processes during breakdown in ECRIS plasmas.

  11. Multifunctional fuel additives derived from aminodiols to improve the low-temperature properties of distillate fuels

    SciTech Connect

    Baillargeon, D.J.; Cardis, A.B.; Heck, D.B.

    1991-03-19

    This patent describes a liquid hydrocarbyl fuel composition comprising a major amount of a combustible liquid hydrocarbon fuel and a minor low-temperature properties improving amount of from about 0.001% to about 10 wt % based on the total weight of the composition of an additive comprising a product of reaction made by reacting comonomers. It comprises: an aminodiol or combination or mixture of aminodiols with a reactive acid/anhydride product alone or in combination with other monomers derived from the reaction of benzophenone tetracarboxylic dianhydride or its acid equivalent.

  12. Nonhumidified intermediate temperature fuel cells using protic ionic liquids.

    PubMed

    Lee, Seung-Yul; Ogawa, Atsushi; Kanno, Michihiro; Nakamoto, Hirofumi; Yasuda, Tomohiro; Watanabe, Masayoshi

    2010-07-21

    In this paper, the characterization of a protic ionic liquid, diethylmethylammonium trifluoromethanesulfonate ([dema][TfO]), as a proton conductor for a fuel cell and the fabrication of a membrane-type fuel cell system using [dema][TfO] under nonhumidified conditions at intermediate temperatures are described in detail. In terms of physicochemical and electrochemical properties, [dema][TfO] exhibits high activity for fuel cell electrode reactions (i.e., the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR)) at a Pt electrode, and the open circuit voltage (OCV) of a liquid fuel cell is 1.03 V at 150 degrees C, as has reported in ref 27. However, diethylmethylammonium bis(trifluoromethane sulfonyl)amide ([dema][NTf(2)]) has relatively low HOR and ORR activity, and thus, the OCV is ca. 0.7 V, although [dema][NTf(2)] and [dema][TfO] have an identical cation ([dema]) and similar thermal and bulk-transport properties. Proton conduction occurs mainly via the vehicle mechanism in [dema][TfO] and the proton transference number (t(+)) is 0.5-0.6. This relatively low t(+) appears to be more disadvantageous for a proton conductor than for other electrolytes such as hydrated sulfonated polymer electrolyte membranes (t(+) = 1.0). However, fast proton-exchange reactions occur between ammonium cations and amines in a model compound. This indicates that the proton-exchange mechanism contributes to the fuel cell system under operation, where deprotonated amines are continuously generated by the cathodic reaction, and that polarization of the cell is avoided. Six-membered sulfonated polyimides in the diethylmethylammonium form exhibit excellent compatibility with [dema][TfO]. The composite membranes can be obtained up to a [dema][TfO] content of 80 wt % and exhibit good thermal stability, high ionic conductivity, and mechanical strength and gas permeation comparable to those of hydrated Nafion. H(2)/O(2) fuel cells prepared using the composite membranes can

  13. Temperature and flow measurements on near-freezing aviation fuels in a wing-tank model

    NASA Technical Reports Server (NTRS)

    Friedman, R.; Stockemer, F. J.

    1980-01-01

    Freezing behavior, pumpability, and temperature profiles for aviation turbine fuels were measured in a 190-liter tank chilled to simulate internal temperature gradients encountered in commercial airplane wing tanks. When the bulk of the fuel was above the specification freezing point, pumpout of the fuel removed all fuel except a layer adhering to the bottom chilled surfaces, and the unpumpable fraction depended on the fuel temperature near these surfaces. When the bulk of the fuel was at or below the freezing point, pumpout ceased when solids blocked the pump inlet, and the unpumpable fraction depended on the overall average temperature.

  14. HIGH-TEMPERATURE TUBULAR SOLID OXIDE FUEL CELL GENERATOR DEVELOPMENT

    SciTech Connect

    S.E. Veyo

    1998-09-01

    During the Westinghouse/USDOE Cooperative Agreement period of November 1, 1990 through November 30, 1997, the Westinghouse solid oxide fuel cell has evolved from a 16 mm diameter, 50 cm length cell with a peak power of 1.27 watts/cm to the 22 mm diameter, 150 cm length dimensions of today's commercial prototype cell with a peak power of 1.40 watts/cm. Accompanying the increase in size and power density was the elimination of an expensive EVD step in the manufacturing process. Demonstrated performance of Westinghouse's tubular SOFC includes a lifetime cell test which ran for a period in excess of 69,000 hours, and a fully integrated 25 kWe-class system field test which operated for over 13,000 hours at 90% availability with less than 2% performance degradation over the entire period. Concluding the agreement period, a 100 kW SOFC system successfully passed its factory acceptance test in October 1997 and was delivered in November to its demonstration site in Westervoort, The Netherlands.

  15. The relation between the bolometric flux and the blackbody temperature at the peak of type II bursts from the Rapid Burster

    NASA Technical Reports Server (NTRS)

    Lubin, Lori M.; Lewin, Walter H. G.; Dotani, Tadayasu; Oosterbroek, Tim; Mitsuda, Kazuhisa; Magnier, Eugene; Van Paradijs, Jan; Van Der Klis, Michiel

    1992-01-01

    During about 6 hr of Ginga observations of the Rapid Burster in August 1988, the source emitted type II bursts with durations between about 3 and about 35 s and with peak fluxes which varied by factors of about 5. The Rapid Burster was active in two bursting modes as defined by Marshall et al. (1979): mode I characterize by a burst energy distribution which is 'double-peaked' and mode II by a distribution which is 'single-peaked'. A study of the relationship between the maximum bolometric burst flux, F(max), and the associated blackbody temperature, Tc, shows that mode I bursts consistently show higher Tc values than bursts of mode II. These results, together with previous work, suggest that the relation between F(max) and Tc is dependent on mode. In mode I the color temperature is approximately independent of the burst peak flux, whereas in mode II the two properties are correlated.

  16. The influence of igneous intrusions on the peak temperatures of host rocks: Finite-time emplacement, evaporation, dehydration, and decarbonation

    NASA Astrophysics Data System (ADS)

    Wang, Dayong; Song, Yongchen; Liu, Yu; Zhao, Minglong; Qi, Tian; Liu, Weiguo

    2012-01-01

    Using a 13-m-thick basic sill and its limestone host rocks of the Permian Irati Formation from the Parana Basin, South America, as an example, this paper presents a numerical investigation based on heat conduction models on the effect of the emplacement mechanism of igneous intrusions, pore-water evaporation, and dehydration and decarbonation of host rocks on the peak temperature ( Tpeak) of host rocks. Our results demonstrate that: (1) the finite-time intrusion mechanism of magma can lower the predicted Tpeak of host rocks by up to 100 °C relative to the instantaneous intrusion mechanism, and although pore-water evaporation together with dehydration and decarbonation reactions can also depress the thermal effect of the sill on its host rocks, the maximum effect of these mechanisms on Tpeak only reaches approximately 50 °C. (2) The effect of pore-water evaporation on Tpeak is obviously greater than that of the dehydration and decarbonation reactions: the former can cause a maximum deviation of 40 °C in the predicted Tpeak, whereas the deviation due to the latter is less than 20 °C. Further, the effect of the dehydration and decarbonation reactions on Tpeak is less than 10 °C if pore-water evaporation is allowed simultaneously in the models and can hence be ignored in thermal modeling. (3) The finite-time intrusion mechanism of magma probably represents the natural condition of the sill. Pore-water evaporation and dehydration and decarbonation of host rocks are also likely to play important roles in lowering the thermal effect of the sill.

  17. An optical gas temperature probe for high temperature fossil fuel process streams

    SciTech Connect

    Bauman, L.E.; Cook, R.L.; Lineberry, J.T.; Litchford, R.J.

    1995-12-31

    Reported here are the results of a feasibility study of a modular optical gas temperature probe for direct measurement of gas temperature in fossil-fueled combustion streams. A probe based upon the spectroscopic technique of line reversal would be superior to currently available gas temperature technology. The study concluded that a modular form of the line reversal optical temperature probe is feasible and, as such. the probe should be a commercially viable product with potential economic benefits from improved monitoring and control of utility furnaces. Such a probe will have the capability of making direct measurements of gas temperature in hot (>1500 K) process streams of coal combustion systems and large-scale power plant facilities.

  18. Bio-Fuel Production Assisted with High Temperature Steam Electrolysis

    SciTech Connect

    Grant Hawkes; James O'Brien; Michael McKellar

    2012-06-01

    Two hybrid energy processes that enable production of synthetic liquid fuels that are compatible with the existing conventional liquid transportation fuels infrastructure are presented. Using biomass as a renewable carbon source, and supplemental hydrogen from high-temperature steam electrolysis (HTSE), these two hybrid energy processes have the potential to provide a significant alternative petroleum source that could reduce dependence on imported oil. The first process discusses a hydropyrolysis unit with hydrogen addition from HTSE. Non-food biomass is pyrolyzed and converted to pyrolysis oil. The pyrolysis oil is upgraded with hydrogen addition from HTSE. This addition of hydrogen deoxygenates the pyrolysis oil and increases the pH to a tolerable level for transportation. The final product is synthetic crude that could then be transported to a refinery and input into the already used transportation fuel infrastructure. The second process discusses a process named Bio-Syntrolysis. The Bio-Syntrolysis process combines hydrogen from HTSE with CO from an oxygen-blown biomass gasifier that yields syngas to be used as a feedstock for synthesis of liquid synthetic crude. Conversion of syngas to liquid synthetic crude, using a biomass-based carbon source, expands the application of renewable energy beyond the grid to include transportation fuels. It can also contribute to grid stability associated with non-dispatchable power generation. The use of supplemental hydrogen from HTSE enables greater than 90% utilization of the biomass carbon content which is about 2.5 times higher than carbon utilization associated with traditional cellulosic ethanol production. If the electrical power source needed for HTSE is based on nuclear or renewable energy, the process is carbon neutral. INL has demonstrated improved biomass processing prior to gasification. Recyclable biomass in the form of crop residue or energy crops would serve as the feedstock for this process. A process model

  19. High-temperature seals for solid oxide fuel cells (SOFC)

    NASA Astrophysics Data System (ADS)

    Singh, Raj N.

    2006-08-01

    A functioning solid oxide fuel-cell (SOFC) may require all types of seals, such as metal-metal, metal-ceramic, and ceramic-ceramic. These seals must function at high temperatures between 600 and 900 °C and in the oxidizing and reducing environments of fuels and air. Among the different types of seals, the metal-metal seals can be readily fabricated using metal joining, soldering, and brazing techniques. However, metal-ceramic and ceramic-ceramic seals require significant research and development because the brittle nature of ceramics/glasses can lead to fracture and loss of seal integrity and functionality. Consequently, any seals involving ceramics/glasses also require significant attention and technology development for reliable SOFC operation. This paper is prepared to primarily address the needs and possible approaches for high-temperature seals for SOFC and seals fabricated using some of these approaches. A new concept of self-healing glass seals is proposed for making seals among material combinations with a significant expansion mismatches.

  20. Refinements to temperature calculations of spent fuel assemblies when in a stagnant gas environment

    SciTech Connect

    Rhodes, C.A.; Haire, M.J.

    1984-01-01

    Undesirably high temperatures are possible in irradiated fuel assemblies because of the radioactive decay of fission products formed while in the reactor. The COXPRO computer code has been used for some time to calculate temperatures in spent fuel when the fuel is suspended in a stagnant gas environment. This code assumed radiation to be the only mode of heat dissipation within the fuel pin bundle. Refinements have been made to include conduction as well as radiation heat transfer within this code. Comparison of calculated and measured temperatures in four separate and independent tests indicate that maximum fuel assembly temperatures can be predicted to within about 6%. 2 references, 5 figures.

  1. Spent fuel dry storage technology development: fuel temperature measurements under imposed dry storage conditions (I kW PWR spent fuel assembly)

    SciTech Connect

    Unterzuber, R.; Wright, J.B.

    1980-09-01

    A spent fuel assembly temperature test under imposed dry storage conditions was conducted at the Engine Maintenance Assembly and Disassembly (E-MAD) facility on the Nevada Test Site in support of spent fuel dry storage technology development. This document presents the test data and results obtained from an approximately 1.0 kW decay heat level PWR spent fuel assembly. A spent fuel test apparatus was designed to utilize a representative stainless steel spent fuel canister, a canister lid containing internal temperature instrumentation to measure fuel cladding temperatures, and a carbon steel liner that encloses the canister and lid. Electrical heaters along the liner length, on the lid, and below the canister are used to impose dry storage canister temperature profiles. Temperature instrumentation is provided on the liner and canister. The liner and canister are supported by a test stand in one of the large hot cells (West Process Cell) inside E-MAD. Fuel temperature measurements have been performed using imposed canister temperature profiles from the electrically heated and spent fuel drywell tests being conducted at E-MAD as well as for four constant canister temperature profiles, each with a vacuum, helium and air backfill. Computer models have been utilized in conjunction with the test to predict the thermal response of the fuel cladding. Computer predictions are presented, and they show good agreement with the test data.

  2. Performance of vapor-fed direct dimethyl ether fuel cell utilizing high temperature polybenzimidazole polymer electrolyte membrane

    NASA Astrophysics Data System (ADS)

    Neutzler, Jay; Qian, Guoqing; Huang, Kevin; Benicewicz, Brian

    2012-10-01

    There is increasing interest in dimethyl ether (DME) as a synthetic fuel. It has present-day relevance and introduces an effective path forward as an energy-dense, low-pressure hydrogen carrier/storage fuel for fuel cells with applications in transportation, stationary, and portable power. Direct reaction DME fuel cells have particular relevance to portable power. This study presents the performance of the vapor-fed direct reaction of DME using high temperature Polybenzimidazole (PBI) Polymer Electrolyte Membrane (PEM). Catalyzed PBI membrane utilized a Pt/Ru black anode and a Pt/C supported cathode. Performance was evaluated from temperatures of 180 °C-210 °C and at pressures from 100 kPa to 300 kPa. A strong performance correlation was observed in this study for these temperatures and pressures. A peak power density of 50 mW cm-2 was achieved at 180 °C without back pressure, whereas, an increase to 129 mW cm-2 was achieved at 210 °C at 300 kPa pressure. The performance of high temperature PBI PEMFCs with direct vapor-fed DME are investigated with emphasis on the critical variables of cell operation; temperature, back pressure, and humidity.

  3. Effect of increased fuel temperature on emissions of oxides of nitrogen from a gas turbine combustor burning ASTM jet-A fuel

    NASA Technical Reports Server (NTRS)

    Marchionna, N. R.

    1974-01-01

    An annular gas turbine combustor was tested with heated ASTM Jet-A fuel to determine the effect of increased fuel temperature on the formation of oxides of nitrogen. Fuel temperature ranged from ambient to 700 K. The NOx emission index increased at a rate of 6 percent per 100 K increase in fuel temperature.

  4. Thermal Analysis of a TREAT Fuel Assembly

    SciTech Connect

    Papadias, Dionissios; Wright, Arthur E.

    2014-07-09

    The objective of this study was to explore options as to reduce peak cladding temperatures despite an increase in peak fuel temperatures. A 3D thermal-hydraulic model for a single TREAT fuel assembly was benchmarked to reproduce results obtained with previous thermal models developed for a TREAT HEU fuel assembly. In exercising this model, and variants thereof depending on the scope of analysis, various options were explored to reduce the peak cladding temperatures.

  5. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    SciTech Connect

    Allan J. Jacobson

    2005-11-17

    Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode--electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. In this report, the oxygen exchange kinetics of a P2 composition are described in detail. The oxygen exchange kinetics of the oxygen deficient double perovskite LnBaCo{sub 2}O{sub 5.5+{delta}} (Ln=Pr and Nd) have been determined by electrical conductivity relaxation. The high electronic conductivity and rapid diffusion and surface exchange kinetics of PBCO suggest its application as cathode material in intermediate temperature solid oxide fuel cells.

  6. Irradiation performance of AGR-1 high temperature reactor fuel

    SciTech Connect

    Paul A. Demkowicz; John D. Hunn; Robert N. Morris; Charles A. Baldwin; Philip L. Winston; Jason M. Harp; Scott A. Ploger; Tyler Gerczak; Isabella J. van Rooyen; Fred C. Montgomery; Chinthaka M. Silva

    2014-10-01

    The AGR-1 experiment contained 72 low-enriched uranium oxide/uranium carbide TRISO-coated particle fuel compacts in six capsules irradiated to burnups of 11.2 to 19.5% FIMA, with zero TRISO coating failures detected during the irradiation. The irradiation performance of the fuel–including the extent of fission product release and the evolution of kernel and coating microstructures–was evaluated based on detailed examination of the irradiation capsules, the fuel compacts, and individual particles. Fractional release of 110mAg from the fuel compacts was often significant, with capsule-average values ranging from 0.01 to 0.38. Analysis of silver release from individual compacts indicated that it was primarily dependent on fuel temperature history. Europium and strontium were released in small amounts through intact coatings, but were found to be significantly retained in the outer pyrocrabon and compact matrix. The capsule-average fractional release from the compacts was 1×10 4 to 5×10 4 for 154Eu and 8×10 7 to 3×10 5 for 90Sr. The average 134Cs release from compacts was <3×10 6 when all particles maintained intact SiC. An estimated four particles out of 2.98×105 experienced partial cesium release due to SiC failure during the irradiation, driving 134Cs release in two capsules to approximately 10 5. Identification and characterization of these particles has provided unprecedented insight into the nature and causes of SiC coating failure in high-quality TRISO fuel. In general, changes in coating morphology were found to be dominated by the behavior of the buffer and inner pyrolytic carbon (IPyC), and infrequently observed SiC layer damage was usually related to cracks in the IPyC. Palladium attack of the SiC layer was relatively minor, except for the particles that released cesium during irradiation, where SiC corrosion was found adjacent to IPyC cracks. Palladium, silver, and uranium were found in the SiC layer of irradiated particles, and characterization

  7. Direct fired reciprocating engine and bottoming high temperature fuel cell hybrid

    DOEpatents

    Geisbrecht, Rodney A.; Holcombe, Norman T.

    2006-02-07

    A system of a fuel cell bottoming an internal combustion engine. The engine exhaust gas may be combined in varying degrees with air and fed as input to a fuel cell. Reformer and oxidizers may be combined with heat exchangers to accommodate rich and lean burn conditions in the engine in peaking and base load conditions without producing high concentrations of harmful emissions.

  8. On the flexibility of high temperature reactor cores for high-and low-enriched fuel

    SciTech Connect

    Bzandes, S.; Lonhert, G.

    1982-07-01

    The operational flexibility of a high temperature reactor (HTR) is not restricted to either a low- or a high-enriched fuel cycle. Both fuel cycles are possible for the same core design. The fuel cycle cost is, however, penalized for low-enriched fuel; in addition, higher uranium consumption is required. Hence, an HTR is most economical to operate in the high-enriched thorium-uranium fuel cycle.

  9. SU-E-T-354: Peak Temperature Ratio of TLD Glow Curves to Investigate the Spatial Dependence of LET in a Clinical Proton Beam

    SciTech Connect

    Reft, C; Pankuch, M; Ramirez, H

    2014-06-01

    Purpose: Use the ratio of the two high temperature peaks (HTR) in TLD 700 glow curves to investigate spatial dependence of the linear energy transfer (LET) in proton beams. Studies show that the relative biological effectiveness (RBE) depends upon the physical dose as well as its spatial distribution. Although proton therapy uses a spatially invariant RBE of 1.1, studies suggest that the RBE increases in the distal edge of a spread out Bragg peak (SOBP) due to the increased LET. Methods: Glow curve studies in TLD 700 show that the 280 C temperature peak is more sensitive to LET radiation than the 210 C temperature peak. Therefore, the areas under the individual temperature peaks for TLDs irradiated in a proton beam normalized to the peak ratio for 6 MV photons are used to determine the HTR to obtain information on its LET. TLD 700 chips with dimensions 0.31×0.31×0.038 cc are irradiated with 90 MeV protons at varying depths in a specially designed blue wax phantom to investigate LET spatial dependence. Results: Five TLDs were placed at five different depths of the percent depth dose curve (PDD) of range 16.2 cm: center of the SOPB and approximately at the 99% distal edge, 90%, 75% and 25% of the PDD, respectively. HTR was 1.3 at the center of the SOBP and varied from 2.2 to 3.9 which can be related to an LET variation from 0.5 to 18 KeV/μ via calibration with radiation beams of varying LET. Conclusion: HTR data show a spatially invariant LET slightly greater than the 6 MV radiations in the SOBP, but a rapidly increasing LET at the end of the proton range. These results indicate a spatial variation in RBE with potential treatment consequences when selecting treatment margins to minimize the uncertainties in proton RBE.

  10. New Optimal Sensor Suite for Ultrahigh Temperature Fossil Fuel Applications

    SciTech Connect

    John Coggin; Jonas Ivasauskas; Russell G. May; Michael B. Miller; Rena Wilson

    2006-09-30

    Accomplishments during Phase II of a program to develop and demonstrate photonic sensor technology for the instrumentation of advanced powerplants are described. The goal of this project is the research and development of advanced, robust photonic sensors based on improved sapphire optical waveguides, and the identification and demonstration of applications of the new sensors in advanced fossil fuel power plants, where the new technology will contribute to improvements in process control and monitoring. During this program work period, major progress has been experienced in the development of the sensor hardware, and the planning of the system installation and operation. The major focus of the next work period will be the installation of sensors in the Hamilton, Ohio power plant, and demonstration of high-temperature strain gages during mechanical testing of SOFC components.

  11. Controlling for peak power extraction from microbial fuel cells can increase stack voltage and avoid cell reversal

    NASA Astrophysics Data System (ADS)

    Boghani, Hitesh C.; Papaharalabos, George; Michie, Iain; Fradler, Katrin R.; Dinsdale, Richard M.; Guwy, Alan J.; Ieropoulos, Ioannis; Greenman, John; Premier, Giuliano C.

    2014-12-01

    Microbial fuel cells (MFCs) are bioelectrochemical systems which can degrade organic materials and are increasingly seen as potential contributors to low carbon technologies, particularly in energy recovery from and treatment of wastewaters. The theoretical maximum open circuit voltage from MFCs lies in the region of 1.1 V, but is reduced substantially by overvoltage losses. Practical use of the power requires stacking or other means to increase voltage. Series stacking of MFCs with typically encountered variability in operating conditions and performance raises the risk of cell reversal, which diminishes overall power performance. A novel strategy of MFC subsystem series connectivity along with maximum power point tracking (MPPT) generates increased power from individual MFCs whilst eliminating cell reversal. MFCs fed with lower concentrations of substrate experienced voltage reversal when connected in normal series connection with one common load, but when MFCs and loads together were connected in series, the underperforming cell is effectively bypassed and maximum power is made available. It is concluded that stack voltage may be increased and cell reversal avoided using the hybrid connectivity along with MPPT. This approach may be suitable for stacked MFC operations in the event that large scale arrays/modules are deployed in treating real wastewaters.

  12. Carbide fuel pin and capsule design for irradiations at thermionic temperatures

    NASA Technical Reports Server (NTRS)

    Siegel, B. L.; Slaby, J. G.; Mattson, W. F.; Dilanni, D. C.

    1973-01-01

    The design of a capsule assembly to evaluate tungsten-emitter - carbide-fuel combinations for thermionic fuel elements is presented. An inpile fuel pin evaluation program concerned with clad temperture, neutron spectrum, carbide fuel composition, fuel geometry,fuel density, and clad thickness is discussed. The capsule design was a compromise involving considerations between heat transfer, instrumentation, materials compatibility, and test location. Heat-transfer calculations were instrumental in determining the method of support of the fuel pin to minimize axial temperature variations. The capsule design was easily fabricable and utilized existing state-of-the-art experience from previous programs.

  13. On the influence of temperature on PEM fuel cell operation

    NASA Astrophysics Data System (ADS)

    Coppo, M.; Siegel, N. P.; Spakovsky, M. R. von

    The 3D implementation of a previously developed 2D PEMFC model [N.P. Siegel, M.W. Ellis, D.J. Nelson, M.R. von Spakovsky, A two-dimensional computational model of a PEMFC with liquid water transport, J. Power Sources 128 (2) (2004) 173-184; N.P. Siegel, M.W. Ellis, D.J. Nelson, M.R. von Spakovsky, Single domain PEMFC model based on agglomerate catalyst geometry, J. Power Sources 115 (2003) 81-89] has been used to analyze the various pathways by which temperature affects the operation of a proton exchange membrane fuel cell [M. Coppo, CFD analysis and experimental investigation of proton exchange membrane fuel cells, Ph.D. Dissertation, Politecnico di Torino, Turin, Italy, 2005]. The original model, implemented in a specially modified version of CFDesign ® [CFDesign ® V5.1, Blue Ridge Numerics, 2003] , accounts for all of the major transport processes including: (i) a three-phase model for water transport in the liquid, vapor and dissolved phases, (ii) proton transport, (iii) gaseous species transport and reaction, (iv) an agglomerate model for the catalyst layers and (v) gas phase momentum transport. Since the details of it have been published earlier [N.P. Siegel, M.W. Ellis, D.J. Nelson, M.R. von Spakovsky, A two-dimensional computational model of a PEMFC with liquid water transport, J. Power Sources 128 (2) (2004) 173-184; N.P. Siegel, M.W. Ellis, D.J. Nelson, M.R. von Spakovsky, Single domain PEMFC model based on agglomerate catalyst geometry, J. Power Sources 115 (2003) 81-89; N.P. Siegel, Development and validation of a computational model for a proton exchange membrane fuel cell, Ph.D. Dissertation, Virginia Polytechnic Institute and State University, Blacksburg, VA, 2003], only new features are briefly discussed in the present work. In particular, the model has been extended in order to account for the temperature dependence of all of the physical properties involved in the model formulation. Moreover, a novel model has been developed to describe liquid

  14. Low-temperature α peak of the internal friction in niobium and its relation to the relaxation of kinks in dislocations

    NASA Astrophysics Data System (ADS)

    Natsik, V. D.; Pal'-Val', P. P.; Pal'-Val', L. N.; Semerenko, Yu. A.

    2001-05-01

    The influence of impurities on the parameters of the α peak of the internal friction in single-crystal and polycrystalline niobium is investigated; the internal friction is recorded in the temperature range 200-250 K at a vibrational frequency of ≈80 kHz. It is found that increasing the purity of the samples leads to an increase of the peak location temperature and to an increase of its width and amplitude. The structural sensitivity of this peak was observed previously in a study of the influence on this peak of a preliminary plastic deformation, thermocycling, and low-temperature recovery. A statistical description of the whole set of experimental data is proposed, which takes into account the dependence of the activation energy and attempt period on the impurity concentration and on the characteristic value and statistical scatter of the internal stresses. A new algorithm is developed for analyzing the experimental data to obtain empirical estimates for the values of the activation energy, its variance, the attempt period, and relaxation strength for the different structural states of the samples. It is shown that the α peak is a consequence of the resonant interaction of elastic vibrations with the thermally activated nucleation of kink pairs on dislocation segments lying in the valleys of the Peierls potential relief. Empirical estimates are obtained for the values of the main parameters characterizing this process. It is found that the properties of the α peak in niobium are in qualitative agreement with Engelke's theory of the nucleation and relaxation of dislocation kinks.

  15. High temperature tubular solid oxide fuel cell development

    SciTech Connect

    Ray, E.R.

    1992-01-01

    Important to the development commercialization of any new technology is a field test program. This is a mutually beneficial program for both the developer and the prospective user. The developer is able to acquire valuable field operating experience that is not available in a laboratory while the user has the opportunity to become familiar with the new technology and gains a working knowledge of it through hands-on experience. Westinghouse, recognizing these benefits, initiated a program in 1986 by supplying a 400 W SOFC generator to Tennessee Valley Authority. This generator operated for approximately 1,760 hours and was constructed of twenty-four 30 cm thick-wall PST cells. In 1987, three, 3 kW SOFC generators were installed and operated at the facilities of the Tokyo Gas Company and the Osaka Gas Company. At Osaka Gas, two generators were used. First a training generator, operated for 2900 hours before it was replaced on a preplanned schedule with the second generator. The second generator operated for 3,600 hours. Tokyo Gas generator was operated for 4,900 hours. These generators had a 98% availability and measured NO{sub x} levels of less than 1.3 ppM. The 3 kW SOFC generators were constructed of 144 36 cm thick-wall PST cells. The 3 kW generators, as was the TVA generator, were fueled with hydrogen and carbon monoxide. The next major milestone in the field unit program was reached in early 1992 with the delivery to The UTILITIES, a consortium of the Kansai Electric Power company, the Tokyo Gas Company, and the Osaka Gas Company, of a natural gas fueled all electric SOFC system. This system is rated at a nominal 25 kW dc with a peak capacity of 40 kW dc. The NO{sub x} was measured at <0.3 ppM (corrected to 15% oxygen). The system consists of 1152 cells (thin-wall PST) of 50 cm active length, manufactured at the PPMF. Cells are contained in two independently controlled and operated generators. 2,300 hours of stable operation has been obtained on the first unit.

  16. High temperature tubular solid oxide fuel cell development

    SciTech Connect

    Ray, E.R.

    1992-09-01

    Important to the development commercialization of any new technology is a field test program. This is a mutually beneficial program for both the developer and the prospective user. The developer is able to acquire valuable field operating experience that is not available in a laboratory while the user has the opportunity to become familiar with the new technology and gains a working knowledge of it through hands-on experience. Westinghouse, recognizing these benefits, initiated a program in 1986 by supplying a 400 W SOFC generator to Tennessee Valley Authority. This generator operated for approximately 1,760 hours and was constructed of twenty-four 30 cm thick-wall PST cells. In 1987, three, 3 kW SOFC generators were installed and operated at the facilities of the Tokyo Gas Company and the Osaka Gas Company. At Osaka Gas, two generators were used. First a training generator, operated for 2900 hours before it was replaced on a preplanned schedule with the second generator. The second generator operated for 3,600 hours. Tokyo Gas generator was operated for 4,900 hours. These generators had a 98% availability and measured NO{sub x} levels of less than 1.3 ppM. The 3 kW SOFC generators were constructed of 144 36 cm thick-wall PST cells. The 3 kW generators, as was the TVA generator, were fueled with hydrogen and carbon monoxide. The next major milestone in the field unit program was reached in early 1992 with the delivery to The UTILITIES, a consortium of the Kansai Electric Power company, the Tokyo Gas Company, and the Osaka Gas Company, of a natural gas fueled all electric SOFC system. This system is rated at a nominal 25 kW dc with a peak capacity of 40 kW dc. The NO{sub x} was measured at <0.3 ppM (corrected to 15% oxygen). The system consists of 1152 cells (thin-wall PST) of 50 cm active length, manufactured at the PPMF. Cells are contained in two independently controlled and operated generators. 2,300 hours of stable operation has been obtained on the first unit.

  17. Observed Temperature Effects on Hourly Residential Electric LoadReduction in Response to an Experimental Critical Peak PricingTariff

    SciTech Connect

    Herter, Karen B.; McAuliffe, Patrick K.; Rosenfeld, Arthur H.

    2005-11-14

    The goal of this investigation was to characterize themanual and automated response of residential customers to high-price"critical" events dispatched under critical peak pricing tariffs testedin the 2003-2004 California Statewide Pricing Pilot. The 15-monthexperimental tariff gave customers a discounted two-price time-of-userate on 430 days in exchange for 27 critical days, during which the peakperiod price (2 p.m. to 7 p.m.) was increased to about three times thenormal time-of-use peak price. We calculated response by five-degreetemperature bins as the difference between peak usage on normal andcritical weekdays. Results indicatedthat manual response to criticalperiods reached -0.23 kW per home (-13 percent) in hot weather(95-104.9oF), -0.03 kW per home (-4 percent) in mild weather (60-94.9oF),and -0.07 kW per home (-9 percent) during cold weather (50-59.9oF).Separately, we analyzed response enhanced by programmable communicatingthermostats in high-use homes with air-conditioning. Between 90oF and94.9oF, the response of this group reached -0.56 kW per home (-25percent) for five-hour critical periods and -0.89 kW/home (-41 percent)for two-hour critical periods.

  18. Low platinum loading for high temperature proton exchange membrane fuel cell developed by ultrasonic spray coating technique

    NASA Astrophysics Data System (ADS)

    Su, Huaneng; Jao, Ting-Chu; Barron, Olivia; Pollet, Bruno G.; Pasupathi, Sivakumar

    2014-12-01

    This paper reports use of an ultrasonic-spray for producing low Pt loadings membrane electrode assemblies (MEAs) with the catalyst coated substrate (CCS) fabrication technique. The main MEA sub-components (catalyst, membrane and gas diffusion layer (GDL)) are supplied from commercial manufacturers. In this study, high temperature (HT) MEAs with phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB-PBI) membrane are fabricated and tested under 160 °C, hydrogen and air feed 100 and 250 cc min-1 and ambient pressure conditions. Four different Pt loadings (from 0.138 to 1.208 mg cm-2) are investigated in this study. The experiment data are determined by in-situ electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high Pt loading MEA exhibits higher performance at high voltage operating conditions but lower performances at peak power due to the poor mass transfer. The Pt loading 0.350 mg cm-2 GDE performs the peak power density and peak cathode mass power to 0.339 W cm-2 and 0.967 W mgPt-1, respectively. This work presents impressive cathode mass power and high fuel cell performance for high temperature proton exchange membrane fuel cells (HT-PEMFCs) with low Pt loadings.

  19. Materials System for Intermediate Temperature Solid Oxide Fuel Cell

    SciTech Connect

    Uday B. Pal; Srikanth Gopalan

    2005-01-24

    AC complex impedance spectroscopy studies were conducted between 600-800 C on symmetrical cells that employed strontium-and-magnesium-doped lanthanum gallate electrolyte, La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3} (LSGM). The objective of the study was to identify the materials system for fabrication and evaluation of intermediate temperature (600-800 C) solid oxide fuel cells (SOFCs). The slurry-coated electrode materials had fine porosity to enhance catalytic activity. Cathode materials investigated include La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), LSCF (La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3}), a two-phase particulate composite consisting of LSM-doped-lanthanum gallate (LSGM), and LSCF-LSGM. The anode materials were Ni-Ce{sub 0.85}Gd{sub 0.15}O{sub 2} (Ni-GDC) and Ni-Ce{sub 0.6}La{sub 0.4}O{sub 2} (Ni-LDC) composites. Experiments conducted with the anode materials investigated the effect of having a barrier layer of GDC or LDC in between the LSGM electrolyte and the Ni-composite anode to prevent adverse reaction of the Ni with lanthanum in LSGM. For proper interpretation of the beneficial effects of the barrier layer, similar measurements were performed without the barrier layer. The ohmic and the polarization resistances of the system were obtained over time as a function of temperature (600-800 C), firing temperature, thickness, and the composition of the electrodes. The study revealed important details pertaining to the ohmic and the polarization resistances of the electrode as they relate to stability and the charge-transfer reactions that occur in such electrode structures.

  20. Effects of chemical equilibrium on turbine engine performance for various fuels and combustor temperatures

    NASA Technical Reports Server (NTRS)

    Tran, Donald H.; Snyder, Christopher A.

    1992-01-01

    A study was performed to quantify the differences in turbine engine performance with and without the chemical dissociation effects for various fuel types over a range of combustor temperatures. Both turbojet and turbofan engines were studied with hydrocarbon fuels and cryogenic, nonhydrocarbon fuels. Results of the study indicate that accuracy of engine performance decreases when nonhydrocarbon fuels are used, especially at high temperatures where chemical dissociation becomes more significant. For instance, the deviation in net thrust for liquid hydrogen fuel can become as high as 20 percent at 4160 R. This study reveals that computer central processing unit (CPU) time increases significantly when dissociation effects are included in the cycle analysis.

  1. Interconnects for intermediate temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Huang, Wenhua

    Presently, one of the principal goals of solid oxide fuel cells (SOFCs) research is to reduce the stack operating temperature to between 600 and 800°C. However, one of the principal technological barriers is the non-availability of a suitable material satisfying all of the stability requirements for the interconnect. In this work two approaches for intermediate temperature SOFC interconnects have been explored. The first approach comprises an interconnect consisting of a bi-layer structure, a p-type oxide (La0.96Sr0.08MnO 2.001/LSM) layer exposed to a cathodic environment, and an n-type oxide (Y0.08Sr0.88Ti0.95Al0.05O 3-delta/YSTA) layer exposed to anodic conditions. Theoretical analysis based on the bi-layer structure has established design criteria to implement this approach. The analysis shows that the interfacial oxygen partial pressure, which determines the interconnect stability, is independent of the electronic conductivities of both layers but dependent on the oxygen ion layer interconnects, the oxygen ion conductivities of LSM and YSTA were measured as a function of temperature and oxygen partial pressure. Based on the measured data, it has been determined that if the thickness of YSTA layer is around 0.1cm, the thickness of LSM layer should be around 0.6 mum in order to maintain the stability of LSM. In a second approach, a less expensive stainless steel interconnect has been studied. However, one of the major concerns associated with the use of metallic interconnects is the development of a semi-conducting or insulating oxide scale and chromium volatility during extended exposure to the SOFC operating environment. Dense and well adhered Mn-Cu spinet oxide coatings were successfully deposited on stainless steel by an electrophoretic deposition (EPD) technique. It was found that the Mn-Cu-O coating significantly reduced the oxidation rate of the stainless steel and the volatility of chromium. The area specific resistance (ASR) of coated Crofer 22 APU is

  2. Direct Utilization of Coal Syngas in High Temperature Fuel Cells

    SciTech Connect

    Celik, Ismail B.

    2014-10-30

    This EPSCoR project had two primary goals: (i) to build infrastructure and work force at WVU to support long-term research in the area of fuel cells and related sciences; (ii) study effects of various impurities found in coal-syngas on performance of Solid Oxide Fuel Cells (SOFC). As detailed in this report the WVU research team has made significant accomplishments in both of these areas. What follows is a brief summary of these accomplishments: State-of-the-art test facilities and diagnostic tools have been built and put into use. These include cell manufacturing, half-cell and full-cell test benches, XPS, XRD, TEM, Raman, EDAX, SEM, EIS, and ESEM equipment, unique in-situ measurement techniques and test benches (Environmental EM, Transient Mass-Spectrometer-MS, and IR Optical Temperature measurements). In addition, computational capabilities have been developed culminating in a multi-scale multi-physics fuel cell simulation code, DREAM-SOFC, as well as a Beowulf cluster with 64 CPU units. We have trained 16 graduate students, 10 postdoctoral fellows, and recruited 4 new young faculty members who have actively participated in the EPSCoR project. All four of these faculty members have already been promoted to the tenured associate professor level. With the help of these faculty and students, we were able to secure 14 research awards/contracts amounting to a total of circa $5.0 Million external funding in closely related areas of research. Using the facilities mentioned above, the effects of PH3, HCl, Cl2, and H2S on cell performance have been studied in detail, mechanisms have been identified, and also remedies have been proposed and demonstrated in the laboratory. For example, it has been determined that PH3 reacts rapidly with Ni to from secondary compounds which may become softer or even melt at high temperature and then induce Ni migration to the surface of the cell changing the material and micro-structural properties of the cell drastically. It is found that

  3. Platinum redispersion on metal oxides in low temperature fuel cells.

    PubMed

    Tripković, Vladimir; Cerri, Isotta; Nagami, Tetsuo; Bligaard, Thomas; Rossmeisl, Jan

    2013-03-01

    We have analyzed the aptitude of several metal oxide supports (TiO(2), SnO(2), NbO(2), ZrO(2), SiO(2), Ta(2)O(5) and Nb(2)O(5)) to redisperse platinum under electrochemical conditions pertinent to the Proton Exchange Membrane Fuel Cell (PEMFC) cathode. The redispersion on oxide supports in air has been studied in detail; however, due to different operating conditions it is not straightforward to link the chemical and the electrochemical environment. The largest differences reflect in (1) the oxidation state of the surface (the oxygen species coverage), (2) temperature and (3) the possibility of platinum dissolution at high potentials and the interference of redispersion with normal working potential of the PEMFC cathode. We have calculated the PtO(x) (x = 0, 1, 2) adsorption energies on different metal oxides' surface terminations as well as inside the metal oxides' bulk, and we have concluded that NbO(2) might be a good support for platinum redispersion at PEMFC cathodes. PMID:23358311

  4. Analysis of higher than normal fuel temperatures in the hexagonal geometry TRIGA reactor

    SciTech Connect

    Hughes, D.; Boyle, P.; Levine, S.H.

    1996-12-31

    The 1-MW Pennsylvania State University TRIGA has hexagonal geometry and a water-filled central thimble. It was operated with all 8.5 wt% U fuel from December 1965 until July 1972, when 12 wt% U fuel elements replaced the 8.5 wt% U fuel in the centermost ring, the B ring. Although the power density of the 12 wt% U fuel was {approximately}35% greater than the corresponding 8.5 wt% U fuel, its maximum steady-state fuel temperature was always below 500{degrees}C when operating at 1 MW. Since that time, the core has been successfully loaded by placing six 12 wt% U fuel elements in the B ring. The used 12 wt% U fuel moved outward. Recently, however, a new instrumented 12 wt% U fuel element initially read a much higher fuel temperature than all previous similar fuel elements. The purpose of this paper is to present the calculations and experiments performed to correlate calculations with experimental data and to determine the cause of the higher fuel temperature for this element.

  5. Experimental Study of the Stability of Aircraft Fuels at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Vranos, A.; Marteney, P. J.

    1980-01-01

    An experimental study of fuel stability was conducted in an apparatus which simulated an aircraft gas turbine fuel system. Two fuels were tested: Jet A and Number 2 Home Heating oil. Jet A is an aircraft gas turbine fuel currently in wide use. No. 2HH was selected to represent the properties of future turbine fuels, particularly experimental Reference Broad Specification, which, under NASA sponsorship, was considered as a possible next-generation fuel. Tests were conducted with varying fuel flow rates, delivery pressures and fuel pretreatments (including preheating and deoxygenation). Simulator wall temperatures were varied between 422K and 672K at fuel flows of 0.022 to 0.22 Kg/sec. Coking rate was determined at four equally-spaced locations along the length of the simulator. Fuel samples were collected for infrared analysis. The dependence of coking rate in Jet A may be correlated with surface temperature via an activation energy of 9 to 10 kcal/mole, although the results indicate that both bulk fluid and surface temperature affect the rate of decomposition. As a consequence, flow rate, which controls bulk temperature, must also be considered. Taken together, these results suggest that the decomposition reactions are initiated on the surface and continue in the bulk fluid. The coking rate data for No. 2 HH oil are very highly temperature dependent above approximately 533K. This suggests that bulk phase reactions can become controlling in the formation of coke.

  6. Low-Enriched Fuel Design Concept for the Prismatic Very High Temperature Reactor Core

    SciTech Connect

    Sterbentz, James W

    2007-05-01

    A new non-TRISO fuel and clad design concept is proposed for the prismatic, heliumcooled Very High Temperature Reactor core. The new concept could substantially reduce the current 10-20 wt% TRISO uranium enrichments down to 4-6 wt% for both initial and reload cores. The proposed fuel form would be a high-temperature, high-density uranium ceramic, for example UO2, configured into very small diameter cylindrical rods. The small diameter fuel rods significantly increase core reactivity through improved neutron moderation and fuel lumping. Although a high-temperature clad system for the concept remains to be developed, recent success in tube fabrication and preliminary irradiation testing of silicon carbide (SiC) cladding for light water reactor applications offers good potential for this application, and for future development of other carbide clad designs. A high-temperature ceramic fuel, together with a high-temperature clad material, could also lead to higher thermal safety margins during both normal and transient reactor conditions relative to TRISO fuel. The calculated neutronic results show that the lowenrichment, small diameter fuel rods and low thermal neutron absorbing clad retain the strong negative Doppler fuel temperature coefficient of reactivity that ensures inherent safe operation of the VHTR, and depletion studies demonstrate that an 18-month power cycle can be achieved with the lower enrichment fuel.

  7. Nonhumidified High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2005-01-01

    Fuel cells are being considered for a wide variety of aerospace applications. One of the most versatile types of fuel cells is the proton-exchange-membrane (PEM) fuel cell. PEM fuel cells can be easily scaled to meet the power and space requirements of a specific application. For example, small 100-W PEM fuel cells are being considered for personal power for extravehicular activity suit applications, whereas larger PEM fuel cells are being designed for primary power in airplanes and in uninhabited air vehicles. Typically, PEM fuel cells operate at temperatures up to 80 C. To increase the efficiency and power density of the fuel cell system, researchers are pursuing methods to extend the operating temperature of the PEM fuel cell to 180 C. The most widely used membranes in PEM fuel cells are Nafion 112 and Nafion 117--sulfonated perfluorinated polyethers that were developed by DuPont. In addition to their relatively high cost, the properties of these membranes limit their use in a PEM fuel cell to around 80 C. The proton conductivity of Nafion membranes significantly decreases above 80 C because the membrane dehydrates. The useful operating range of Nafion-based PEM fuel cells can be extended to over 100 C if ancillary equipment, such as compressors and humidifiers, is added to maintain moisture levels within the membrane. However, the addition of these components reduces the power density and increases the complexity of the fuel cell system.

  8. Rate and peak concentrations of off-gas emissions in stored wood pellets--sensitivities to temperature, relative humidity, and headspace volume.

    PubMed

    Kuang, Xingya; Shankar, Tumuluru Jaya; Bi, Xiaotao T; Lim, C Jim; Sokhansanj, Shahab; Melin, Staffan

    2009-11-01

    Wood pellets emit CO, CO(2), CH(4), and other volatiles during storage. Increased concentration of these gases in a sealed storage causes depletion of concentration of oxygen. The storage environment becomes toxic to those who operate in and around these storages. The objective of this study was to investigate the effects of temperature, moisture, and the relative size of storage headspace on emissions from wood pellets in an enclosed space. Twelve 10-l plastic containers were used to study the effects of headspace ratio (25, 50, and 75% of container volume) and temperatures (10-50 degrees C). Another eight containers were set in uncontrolled storage relative humidity (RH) and temperature. Concentrations of CO(2), CO, and CH(4) were measured by gas chromatography (GC). The results showed that emissions of CO(2), CO, and CH(4) from stored wood pellets are more sensitive to storage temperature than to RH and the relative volume of headspace. Higher peak emission factors are associated with higher temperatures. Increased headspace volume ratio increases peak off-gas emissions because of the availability of oxygen associated with pellet decomposition. Increased RH in the enclosed container increases the rate of off-gas emissions of CO(2), CO, and CH(4) and oxygen depletion. PMID:19656803

  9. Rate and peak concentrations of off-gas emissions in stored wood pellets sensitivities to temperature, relative humidity, and headspace volume

    SciTech Connect

    Kuang, Xingya; Shankar, T.J.; Bi, X.T.; Lim, C. Jim; Sokhansanj, Shahabaddine; Melin, Staffan

    2009-08-01

    Wood pellets emit CO, CO2, CH4 and other volatiles during storage. Increased concentration of these gases in a sealed storage causes depletion of concentration of oxygen. The storage environment becomes toxic to those who operate in and around these storages. The objective of this study was to investigate the effects of temperature, moisture and storage headspace on emissions from wood pellets in an enclosed space. Twelve 10-liter plastic containers were used to study the effects of headspace ratio (25%, 50%, and 75% of container volume) and temperatures (10-50oC). Another eight containers were set in uncontrolled storage relative humidity and temperature. Concentrations of CO2, CO and CH4 were measured by a gas chromatography (GC). The results showed that emissions of CO2, CO and CH4 from stored wood pellets are most sensitive to storage temperature. Higher peak emission factors are associated with higher temperatures. Increased headspace volume ratio increases peak off-gas emissions because of the availability of oxygen for pellet decomposition. Increased relative humidity in the enclosed container increases the rate of off-gas emissions of CO2, CO and CH4 and oxygen depletion.

  10. Influence of temperature on growth and peak oil biosynthesis in a carbon-limited medium by Pythium irregulare'

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Kinetic analysis was investigated for a carbon-limited medium, with a carbon-to-nitrogen ratio of 5.0, supporting the growth of the 5,8,11,14,17-eicosapentaenoic acid (20:5; omega-3)accumulating fungal organism Pythium irregulare. The productivity and yield parameters at three temperatures, 14, 21, ...

  11. High temperature polymers for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Einsla, Brian Russel

    Novel proton exchange membranes (PEMs) were investigated that show potential for operating at higher temperatures in both direct methanol (DMFC) and H 2/air PEM fuel cells. The need for thermally stable polymers immediately suggests the possibility of heterocyclic polymers bearing appropriate ion conducting sites. Accordingly, monomers and random disulfonated poly(arylene ether) copolymers containing either naphthalimide, benzoxazole or benzimidazole moieties were synthesized via direct copolymerization. The ion exchange capacity (IEC) was varied by simply changing the ratio of disulfonated monomer to nonsulfonated monomer in the copolymerization step. Water uptake and proton conductivity of cast membranes increased with IEC. The water uptake of these heterocyclic copolymers was lower than that of comparable disulfonated poly(arylene ether) systems, which is a desirable improvement for PEMs. Membrane electrode assemblies were prepared and the initial fuel cell performance of the disulfonated polyimide and polybenzoxazole (PBO) copolymers was very promising at 80°C compared to the state-of-the-art PEM (NafionRTM); nevertheless these membranes became brittle under operating conditions. Several series of poly(arylene ether)s based on disodium-3,3'-disulfonate-4,4 '-dichlorodiphenylsulfone (S-DCDPS) and a benzimidazole-containing bisphenol were synthesized and afforded copolymers with enhanced stability. Selected properties of these membranes were compared to separately prepared miscible blends of disulfonated poly(arylene ether sulfone) copolymers and polybenzimidazole (PBI). Complexation of the sulfonic acid groups with the PBI structure reduced water swelling and proton conductivity. The enhanced proton conductivity of NafionRTM membranes has been proposed to be due to the aggregation of the highly acidic side-chain sulfonic acid sites to form ion channels. A series of side-chain sulfonated poly(arylene ether sulfone) copolymers based on methoxyhydroquinone was

  12. Additional experiments on flowability improvements of aviation fuels at low temperatures, volume 2

    NASA Technical Reports Server (NTRS)

    Stockemer, F. J.; Deane, R. L.

    1982-01-01

    An investigation was performed to study flow improver additives and scale-model fuel heating systems for use with aviation hydrocarbon fuel at low temperatures. Test were performed in a facility that simulated the heat transfer and temperature profiles anticipated in wing fuel tanks during flight of long-range commercial aircraft. The results are presented of experiments conducted in a test tank simulating a section of an outer wing integral fuel tank approximately full-scale in height, chilled through heat exchange panels bonded to the upper and lower horizontal surfaces. A separate system heated lubricating oil externally by a controllable electric heater, to transfer heat to fuel pumped from the test tank through an oil-to-fuel heat exchanger, and to recirculate the heated fuel back to the test tank.

  13. A reduced temperature solid oxide fuel cell with three-dimensionally ordered macroporous cathode

    SciTech Connect

    Liang, B.; Suzuki, T.; Hamamoto, K.; Yamaguchi, T.; Sumi, H.; Fujishiro, Y.; Ingram, B. J.; Carter, J. D.

    2012-01-01

    Three-dimensionally ordered macroporous cathode was fabricated for a zirconia based micro-tubular solid oxide fuel cells (SOFCs). Three different cathodes (cathode A, no pore former; cathode B, with pore former (1.5 {micro}m in diameter); cathode C, with pore former (0.8 {micro}m in diameter)) were compared to investigate how the microstructure of it affected the cell performance at various operating temperatures. Micro-sized pores were well distributed within cathode B and C. The total porosity of cathode A is 35%, while it respectively reached 42 and 50% for cathodes B and C. At the same time, the specific surface area of them was 28.8 and 52.0% larger than that of the cathode A. As a result, the peak power density of the zirconia based cell, with cathode C, was 0.25 and 0.56 W cm{sup -2} at 550 and 600 C, while the respective value was just 0.11 and 0.30 W cm{sup -2} for the cell with cathode A. Thus, optimizing microstructure of cathode should be one of the best approaches for lowering the operating temperature for SOFCs.

  14. TEMP: a computer code to calculate fuel pin temperatures during a transient. [LMFBR

    SciTech Connect

    Bard, F E; Christensen, B Y; Gneiting, B C

    1980-04-01

    The computer code TEMP calculates fuel pin temperatures during a transient. It was developed to accommodate temperature calculations in any system of axi-symmetric concentric cylinders. When used to calculate fuel pin temperatures, the code will handle a fuel pin as simple as a solid cylinder or as complex as a central void surrounded by fuel that is broken into three regions by two circumferential cracks. Any fuel situation between these two extremes can be analyzed along with additional cladding, heat sink, coolant or capsule regions surrounding the fuel. The one-region version of the code accurately calculates the solution to two problems having closed-form solutions. The code uses an implicit method, an explicit method and a Crank-Nicolson (implicit-explicit) method.

  15. Fuel properties effect on the performance of a small high temperature rise combustor

    NASA Technical Reports Server (NTRS)

    Acosta, Waldo A.; Beckel, Stephen A.

    1989-01-01

    The performance of an advanced small high temperature rise combustor was experimentally determined at NASA-Lewis. The combustor was designed to meet the requirements of advanced high temperature, high pressure ratio turboshaft engines. The combustor featured an advanced fuel injector and an advanced segmented liner design. The full size combustor was evaluated at power conditions ranging from idle to maximum power. The effect of broad fuel properties was studied by evaluating the combustor with three different fuels. The fuels used were JP-5, a blend of Diesel Fuel Marine/Home Heating Oil, and a blend of Suntec C/Home Heating Oil. The fuel properties effect on the performance of the combustion in terms of pattern factor, liner temperatures, and exhaust emissions are documented.

  16. Ortigalita Peak gabbro, Franciscan complex: U-Pb dates of intrusion and high-pressure low-temperature metamorphism

    NASA Astrophysics Data System (ADS)

    Mattinson, James M.; Echeverria, Lina M.

    1980-12-01

    Paleontological and isotopic age data from the Franciscan complex in the Ortigalita Peak quadrangle, Diablo Range, California, provide new insight into the tectonic evolution of at least part of the Franciscan complex. Graywacke, shale, pillowed greenstone, and chert in the quadrangle were deposited in Late Jurassic (Tithonian) time, about 135 to 150 m.y. ago, on the basis of radiolaria. These rocks then were incorporated in an accretionary wedge prior to the intrusion of gabbroic magma 95 m.y. ago (U-Pb dating on zircons). Subduction (metamorphism of gabbro and surrounding sedimentary rocks to blueschist grade) closely followed intrusion at about 92 m.y. ago (U-Pb dating on metamorphic titanite and “plagioclase” = albite + pumpellyite ± quartz). The brief interval between intrusion and subduction confirms the idea that the gabbro was intruded into the accretionary wedge, essentially at the site of plate convergence. The much longer interval (about 40 to 55 m.y.) between deposition and subduction reveals that the Franciscan had a long presubduction history and provides a time frame within which more speculative concepts such as extensive northward translation of the Franciscan must be constrained.

  17. Experimental Study of Fuel Heating at Low Temperatures in a Wing Tank Model, Volume 1

    NASA Technical Reports Server (NTRS)

    Stockemer, F. J.

    1981-01-01

    Scale model fuel heating systems for use with aviation hydrocarbon fuel at low temperatures were investigated. The effectiveness of the heating systems in providing flowability and pumpability at extreme low temperature when some freezing of the fuel would otherwise occur is evaluated. The test tank simulated a section of an outer wing tank, and was chilled on the upper and lower surfaces. Turbine engine lubricating oil was heated, and recirculating fuel transferred the heat. Fuels included: a commercial Jet A; an intermediate freeze point distillate; a higher freeze point distillate blended according to Experimental Referee Broadened Specification guidelines; and a higher freeze point paraffinic distillate used in a preceding investigation. Each fuel was chilled to selected temperature to evaluate unpumpable solid formation (holdup). Tests simulating extreme cold weather flight, without heating, provided baseline fuel holdup data. Heating and recirculating fuel increased bulk temperature significantly; it had a relatively small effect on temperature near the bottom of the tank. Methods which increased penetration of heated fuel into the lower boundary layer improved the capability for reducing holdup.

  18. Effects of Thermal Mass, Window Size, and Night-Time Ventilation on Peak Indoor Air Temperature in the Warm-Humid Climate of Ghana

    PubMed Central

    Amos-Abanyie, S.; Akuffo, F. O.; Kutin-Sanwu, V.

    2013-01-01

    Most office buildings in the warm-humid sub-Saharan countries experience high cooling load because of the predominant use of sandcrete blocks which are of low thermal mass in construction and extensive use of glazing. Relatively, low night-time temperatures are not harnessed in cooling buildings because office openings remain closed after work hours. An optimization was performed through a sensitivity analysis-based simulation, using the Energy Plus (E+) simulation software to assess the effects of thermal mass, window size, and night ventilation on peak indoor air temperature (PIAT). An experimental system was designed based on the features of the most promising simulation model, constructed and monitored, and the experimental data used to validate the simulation model. The results show that an optimization of thermal mass and window size coupled with activation of night-time ventilation provides a synergistic effect to obtain reduced peak indoor air temperature. An expression that predicts, indoor maximum temperature has been derived for models of various thermal masses. PMID:23878528

  19. Materials System for Intermediate Temperature Solid Oxide Fuel Cell

    SciTech Connect

    Uday B. Pal; Srikanth Gopalan

    2006-01-12

    The objective of this work was to obtain a stable materials system for intermediate temperature solid oxide fuel cell (SOFC) capable of operating between 600-800 C with a power density greater than 0.2 W/cm{sup 2}. The solid electrolyte chosen for this system was La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3}, (LSGM). To select the right electrode materials from a group of possible candidate materials, AC complex impedance spectroscopy studies were conducted between 600-800 C on symmetrical cells that employed the LSGM electrolyte. Based on the results of the investigation, LSGM electrolyte supported SOFCs were fabricated with La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3}-La{sub 0.9}Sr{sub 0.1}Ga{sub 0.8}Mg{sub 0.2}O{sub 3} (LSCF-LSGM) composite cathode and Nickel-Ce{sub 0.6}La{sub 0.4}O{sub 3} (Ni-LDC) composite anode having a barrier layer of Ce{sub 0.6}La{sub 0.4}O{sub 3} (LDC) between the LSGM electrolyte and the Ni-LDC anode. Electrical performance and stability of these cells were determined and the electrode polarization behavior as a function of cell current was modeled between 600-800 C. The electrical performance of the anode-supported SOFC was simulated assuming an electrode polarization behavior identical to the LSGM-electrolyte-supported SOFC. The simulated electrical performance indicated that the selected material system would provide a stable cell capable of operating between 600-800 C with a power density between 0.2 to 1 W/cm{sup 2}.

  20. An A-site-deficient perovskite offers high activity and stability for low-temperature solid-oxide fuel cells.

    PubMed

    Zhu, Yinlong; Chen, Zhi-Gang; Zhou, Wei; Jiang, Shanshan; Zou, Jin; Shao, Zongping

    2013-12-01

    Solid oxide fuel cells (SOFCs) directly convert fossil and/or renewable fuels into electricity and/or high-quality heat in an environmentally friendly way. However, high operating temperatures result in high cost and material issues, which have limited the commercialization of SOFCs. To lower their operating temperatures, highly active and stable cathodes are required to maintain a reasonable power output. Here, we report a layer-structured A-site deficient perovskite Sr0.95 Nb0.1 Co0.9 O3-δ (SNC0.95) prepared by solid-state reactions that shows not only high activity towards the oxygen reduction reaction (ORR) at operating temperatures below 600 °C, but also offers excellent structural stability and compatibility, and improved CO2 resistivity. An anode-supported fuel cell with SNC0.95 cathode delivers a peak power density as high as 1016 mW cm(-2) with an electrode-area-specific resistance of 0.052 Ω cm(2) at 500 °C. PMID:24155098

  1. Testing of uranium nitride fuel in T-111 cladding at 1200 K cladding temperature

    NASA Technical Reports Server (NTRS)

    Rohal, R. G.; Tambling, T. N.; Smith, R. L.

    1973-01-01

    Two groups of six fuel pins each were assembled, encapsulated, and irradiated in the Plum Brook Reactor. The fuel pins employed uranium mononitride (UN) in a tantalum alloy clad. The first group of fuel pins was irradiated for 1500 hours to a maximum burnup of 0.7-atom-percent uranium. The second group of fuel pins was irradiated for about 3000 hours to a maximum burnup of 1.0-atom-percent uranium. The average clad surface temperature during irradiation of both groups of fuel pins was approximately 1200 K. The postirradiation examination revealed the following: no clad failures or fuel swelling occurred; less than 1 percent of the fission gases escaped from the fuel; and the clad of the first group of fuel pins experienced clad embrittlement whereas the second group, which had modified assembly and fabrication procedures to minimize contamination, had a ductile clad after irradiation.

  2. A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2

    SciTech Connect

    Hashimoto, K.; Cho, K.; Shibauchi, T.; Kasahara, S.; Mizukami, Y.; Katsumata, R.; Tsuruhara, Y.; Terashima, T.; Ikeda, H.; Tanatar, M. A.; Kitano, H.; Salovich, N.; Giannetta, R. W.; Walmsley, P.; Carrington, A.; Prozorov, R.; Matsuda, Y.

    2012-06-21

    In a superconductor, the ratio of the carrier density, n, to its effective mass, m*, is a fundamental property directly reflecting the length scale of the superfluid flow, the London penetration depth, lL. In two-dimensional systems, this ratio n/m* (~1/lL 2) determines the effective Fermi temperature, TF. We report a sharp peak in the x-dependence of lL at zero temperature in clean samples of BaFe2(As1–xPx)2 at the optimum composition x = 0.30, where the superconducting transition temperature Tc reaches a maximum of 30 kelvin. This structure may arise from quantum fluctuations associated with a quantum critical point. The ratio of Tc/TF at x = 0.30 is enhanced, implying a possible crossover toward the Bose-Einstein condensate limit driven by quantum criticality.

  3. Spent fuel temperature and age determination from the analysis of uranium and plutonium isotopics

    SciTech Connect

    Scott, Mark R; Eccleston, George W; Bedell, Jeffrey J; Lockard, Chanelle M

    2009-01-01

    The capability to determine the age (time since irradiation) of spent fuel can be useful for verification and safeguards. While the age of spent fuel can be determined based on measurements of short-lived fission products, these measurements are not routinely done nor generally reported. As an alternative, age can also be determined if the uranium (U) and plutonium (Pu) isotopic values are available. Uranium isotopics are not strongly affected by fuel temperature, and bumup is determined from the {sup 235}U and {sup 236}U isotopic values. Age is calculated after estimating the {sup 241}Pu at the end of irradiation while accounting for the fuel temperature, which is determined from {sup 239}Pu or {sup 240}Pu. Burnup and age determinations are calibrated to reactor models that provide uranium and plutonium isotopics over the range of fuel irradiation. The reactor model must contain sufficient fidelity on details of the reactor type, fuel burnup, irradiation history, initial fuel enrichment and fuel temperature to obtain accurate isotopic calculations. If the latter four are unknown, they can be derived from the uranium and plutonium isotopics. Fuel temperature has a significant affect on the production of plutonium isotopics; therefore, one group cross section reactor models, such as ORIGEN, cannot be used for these calculations. Multi-group cross section set codes, such as Oak Ridge National Laboratory's TRITON code, must be used.

  4. Real time monitoring of temperature of a micro proton exchange membrane fuel cell.

    PubMed

    Lee, Chi-Yuan; Lee, Shuo-Jen; Hu, Yuh-Chung; Shih, Wen-Pin; Fan, Wei-Yuan; Chuang, Chih-Wei

    2009-01-01

    Silicon micro-hole arrays (Si-MHA) were fabricated as a gas diffusion layer (GDL) in a micro fuel cell using the micro-electro-mechanical-systems (MEMS) fabrication technique. The resistance temperature detector (RTD) sensor was integrated with the GDL on a bipolar plate to measure the temperature inside the fuel cell. Experimental results demonstrate that temperature was generally linearly related to resistance and that accuracy and sensitivity were within 0.5 °C and 1.68×10(-3)/°C, respectively. The best experimental performance was 9.37 mW/cm(2) at an H(2)/O(2) dry gas flow rate of 30/30 SCCM. Fuel cell temperature during operation was 27 °C, as measured using thermocouples in contact with the backside of the electrode. Fuel cell operating temperature measured in situ was 30.5 °C. PMID:22573963

  5. Peak performance.

    PubMed

    Milewski, Mary

    2006-10-01

    Earlier this year, a Pittsburgh-based adventurer became the first American with diabetes to reach the top of Mount Everest. He proved that nothing--not record-breaking winds, freezing temperatures, dangerous ice, or his disease--would slow him down. PMID:17039621

  6. New Optical Sensor Suite for Ultrahigh Temperature Fossil Fuel Application

    SciTech Connect

    John Coggin; Tom Flynn; Jonas Ivasauskas; Daniel Kominsky; Carrie Kozikowski; Russell May; Michael Miller; Tony Peng; Gary Pickrell; Raymond Rumpf; Kelly Stinson-Bagby; Dan Thorsen; Rena Wilson

    2007-12-31

    Accomplishments of a program to develop and demonstrate photonic sensor technology for the instrumentation of advanced powerplants and solid oxide fuel cells are described. The goal of this project is the research and development of advanced, robust photonic sensors based on improved sapphire optical waveguides, and the identification and demonstration of applications of the new sensors in advanced fossil fuel power plants, where the new technology will contribute to improvements in process control and monitoring.

  7. New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells

    SciTech Connect

    Allan J. Jacobson

    2006-09-30

    Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode-electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. The initial choices for study were perovskite oxides based on substituted LaFeO{sub 3} (P1 compositions), where significant data in single cell tests exist at PNNL for example, for La{sub 0.8}Sr{sub 0.2}FeO{sub 3} cathodes on both YSZ and CSO/YSZ. The materials selection was then extended to La{sub 2}NiO{sub 4} compositions (K1 compositions), and then in a longer range task we evaluated the possibility of completely unexplored group of materials that are also perovskite related, the ABM{sub 2}O{sub 5+{delta}}. A key component of the research strategy was to evaluate for each cathode material composition, the key performance parameters, including ionic and electronic conductivity, surface exchange rates, stability with respect to the specific electrolyte choice, and thermal expansion coefficients. In the initial phase, we did this in parallel with

  8. Cold temperature diesel performance/combustion with Canadian low ignition quality fuels

    SciTech Connect

    Neill, W.S.; Wolf, W.M.; Webster, G.D.

    1986-01-01

    Three Canadian tar sands derived experimental diesel fuels with cetane numbers (CN) of 36, 31 and 26 and a reference fuel with a 47 CN were tested in a Deutz F1L511D, single cylinder, 4 stroke, naturally aspirated, diesel engine. Tests were performed with intake and cooling air temperatures of 0/sup 0/C and -12/sup 0/C over the entire engine operating range. Performance and combustion behaviour with the 36 CN fuel was marginally acceptable at 0/sup 0/C and unacceptable at -12/sup 0/C. High maximum combustion pressures and rates of combustion pressure rise were encountered at the low engine speed, high load condition with the experimental fuels. Poor combustion behaviour was also experienced with the two low CN fuels at light loads. Operation of this engine configuration with the 31 and 26 CN fuels is not recommended at 0/sup 0/C and lower intake air temperatures.

  9. Long term deposit formation in aviation turbine fuel at elevated temperature

    NASA Technical Reports Server (NTRS)

    Giovanetti, A. J.; Szetela, E. J.

    1986-01-01

    An experimental characterization is conducted for the relationships between deposit mass, operating time, and temperature, in coking associated with aviation fuels under conditions simulating those typical of turbine engine fuel systems. Jet A and Suntech A fuels were tested in stainless steel tubing heated to 420-750 K, over test durations of between 3 and 730 hr and at fuel velocities of 0.07-1.3 m/sec. Deposit rates are noted to be a strong function of tube temperature; for a given set of test conditions, deposition rates for Suntech A exceed those of Jet A by a factor of 10. Deposition rates increased markedly with test duration for both fuels. The heated tube data obtained are used to develop a global chemical kinetic model for fuel oxidation and carbon deposition.

  10. In-situ monitoring of internal local temperature and voltage of proton exchange membrane fuel cells.

    PubMed

    Lee, Chi-Yuan; Fan, Wei-Yuan; Hsieh, Wei-Jung

    2010-01-01

    The distribution of temperature and voltage of a fuel cell are key factors that influence performance. Conventional sensors are normally large, and are also useful only for making external measurements of fuel cells. Centimeter-scale sensors for making invasive measurements are frequently unable to accurately measure the interior changes of a fuel cell. This work focuses mainly on fabricating flexible multi-functional microsensors (for temperature and voltage) to measure variations in the local temperature and voltage of proton exchange membrane fuel cells (PEMFC) that are based on micro-electro-mechanical systems (MEMS). The power density at 0.5 V without a sensor is 450 mW/cm(2), and that with a sensor is 426 mW/cm(2). Since the reaction area of a fuel cell with a sensor is approximately 12% smaller than that without a sensor, but the performance of the former is only 5% worse. PMID:22163556

  11. Electrode Design for Low Temperature Direct-Hydrocarbon Solid Oxide Fuel Cells

    NASA Technical Reports Server (NTRS)

    Chen, Fanglin (Inventor); Zhao, Fei (Inventor); Liu, Qiang (Inventor)

    2015-01-01

    In certain embodiments of the present disclosure, a solid oxide fuel cell is described. The solid oxide fuel cell includes a hierarchically porous cathode support having an impregnated cobaltite cathode deposited thereon, an electrolyte, and an anode support. The anode support includes hydrocarbon oxidation catalyst deposited thereon, wherein the cathode support, electrolyte, and anode support are joined together and wherein the solid oxide fuel cell operates a temperature of 600.degree. C. or less.

  12. Electrode design for low temperature direct-hydrocarbon solid oxide fuel cells

    SciTech Connect

    Chen, Fanglin; Zhao, Fei; Liu, Qiang

    2015-10-06

    In certain embodiments of the present disclosure, a solid oxide fuel cell is described. The solid oxide fuel cell includes a hierarchically porous cathode support having an impregnated cobaltite cathode deposited thereon, an electrolyte, and an anode support. The anode support includes hydrocarbon oxidation catalyst deposited thereon, wherein the cathode support, electrolyte, and anode support are joined together and wherein the solid oxide fuel cell operates a temperature of 600.degree. C. or less.

  13. High temperature solid oxide regenerative fuel cell for solar photovoltaic energy storage

    NASA Technical Reports Server (NTRS)

    Bents, David J.

    1987-01-01

    A hydrogen-oxygen regenerative fuel cell (RFC) energy storage system based on high temperature solid oxide fuel cell (SOFC) technology is described. The reactants are stored as gases in lightweight insulated pressure vessels. The product water is stored as a liquid in saturated equilibrium with the fuel gas. The system functions as a secondary battery and is applicable to darkside energy storage for solar photovoltaics.

  14. Investigations into the low temperature behavior of jet fuels: Visualization, modeling, and viscosity studies

    NASA Astrophysics Data System (ADS)

    Atkins, Daniel L.

    Aircraft operation in arctic regions or at high altitudes exposes jet fuel to temperatures below freeze point temperature specifications. Fuel constituents may solidify and remain within tanks or block fuel system components. Military and scientific requirements have been met with costly, low freeze point specialty jet fuels. Commercial airline interest in polar routes and the use of high altitude unmanned aerial vehicles (UAVs) has spurred interest in the effects of low temperatures and low-temperature additives on jet fuel. The solidification of jet fuel due to freezing is not well understood and limited visualization of fuel freezing existed prior to the research presented in this dissertation. Consequently, computational fluid dynamics (CFD) modeling that simulates jet fuel freezing and model validation were incomplete prior to the present work. The ability to simulate jet fuel freezing is a necessary tool for fuel system designers. An additional impediment to the understanding and simulation of jet fuel freezing has been the absence of published low-temperature thermo-physical properties, including viscosity, which the present work addresses. The dissertation is subdivided into three major segments covering visualization, modeling and validation, and viscosity studies. In the first segment samples of jet fuel, JPTS, kerosene, Jet A and Jet A containing additives, were cooled below their freeze point temperatures in a rectangular, optical cell. Images and temperature data recorded during the solidification process provided information on crystal habit, crystallization behavior, and the influence of the buoyancy-driven flow on freezing. N-alkane composition of the samples was determined. The Jet A sample contained the least n-alkane mass. The cooling of JPTS resulted in the least wax formation while the cooling of kerosene yielded the greatest wax formation. The JPTS and kerosene samples exhibited similar crystallization behavior and crystal habits during

  15. On0Line Fuel Failure Monitor for Fuel Testing and Monitoring of Gas Cooled Very High Temperature Reactor

    SciTech Connect

    Ayman I. Hawari; Mohamed A. Bourham

    2010-04-22

    IVery High Temperature Reactors (VHTR) utilize the TRISO microsphere as the fundamental fuel unit in the core. The TRISO microsphere (~ 1- mm diameter) is composed of a UO2 kernel surrounded by a porous pyrolytic graphite buffer, an inner pyrolytic graphite layer, a silicon carbide (SiC) coating, and an outer pyrolytic graphite layer. The U-235 enrichment of the fuel is expected to range from 4% – 10% (higher enrichments are also being considered). The layer/coating system that surrounds the UO2 kernel acts as the containment and main barrier against the environmental release of radioactivity. To understand better the behavior of this fuel under in-core conditions (e.g., high temperature, intense fast neutron flux, etc.), the US Department of Energy (DOE) is launching a fuel testing program that will take place at the Advanced Test Reactor (ATR) located at Idaho National Laboratory (INL). During this project North Carolina State University (NCSU) researchers will collaborate with INL staff for establishing an optimized system for fuel monitoring for the ATR tests. In addition, it is expected that the developed system and methods will be of general use for fuel failure monitoring in gas cooled VHTRs.

  16. Fission product release and microstructure changes of irradiated MOX fuel at high temperatures

    NASA Astrophysics Data System (ADS)

    Colle, J.-Y.; Hiernaut, J.-P.; Wiss, T.; Beneš, O.; Thiele, H.; Papaioannou, D.; Rondinella, V. V.; Sasahara, A.; Sonoda, T.; Konings, R. J. M.

    2013-11-01

    Samples of irradiated MOX fuel of 44.5 GWd/tHM mean burn-up were prepared by core drilling at three different radial positions of a fuel pellet. They were subsequently heated in a Knudsen effusion mass spectrometer up to complete vaporisation of the sample (˜2600 K) and the release of fission gas (krypton and xenon) as well as helium was measured. Scanning electron microscopy was used in parallel to investigate the evolution of the microstructure of a sample heated under the same condition up to given key temperatures as determined from the gas release profiles. A clear initial difference for fission gas release and microstructure was observed as a function of the radial position of the samples and therefore of irradiation temperature. A good correlation between the microstructure evolution and the gas release peaks could be established as a function of the temperature of irradiation and (laboratory) heating. The region closest to the cladding (0.58 < r/r0 < 0.96), designated as sample type A in Fig. 1. It represents the "cooler" part of the fuel pellet. The irradiation temperatures (Tirrad) in this range are from 854 to 1312 K (ΔT: 458 K). The intermediate radial zone of the pellet (0.42 < r/r0 < 0.81), designated sample type B in Fig. 1, has a Tirrad ranging from 1068 to 1434 K (ΔT: 365 K). The central zone of the pellet (0.003 < r/r0 < 0.41), designated sample type C in Fig. 1, which was close to the hottest part of the pellet, has a Tirrad ranging from 1442 to 1572 K (ΔT: 131 K). The sample irradiation temperatures were determined from the calculated temperature profile (exponential function) knowing the core temperature of the fuel (1573 K) [11], the standard temperature for this type of fuel at the inner side of the cladding (800 K). The average burnup was calculated with TRANSURANUS code [12] and the PA burnup is the average burnup multiplied by the ratio of the fissile Pu concentration in PA over average fissile Pu concentration in fuel [11]. Calculated

  17. Efficient Conversion of Lignin to Electricity Using a Novel Direct Biomass Fuel Cell Mediated by Polyoxometalates at Low Temperatures.

    PubMed

    Zhao, Xuebing; Zhu, J Y

    2016-01-01

    A novel polyoxometalates (POMs) mediated direct biomass fuel cell (DBFC) was used in this study to directly convert lignin to electricity at low temperatures with high power output and Faradaic efficiency. When phosphomolybdic acid H3 PMo12 O40 (PMo12) was used as the electron and proton carrier in the anode solution with a carbon electrode, and O2 was directly used as the final electron acceptor under the catalysis of Pt, the peak power density reached 0.96 mW cm(-2), 560 times higher than that of phenol-fueled microbial fuel cells (MFCs). When the cathode reaction was catalyzed by PMo12, the power density could be greatly enhanced to 5 mW cm(-2). Continuous operation demonstrated that this novel fuel cell was promising as a stable electrochemical power source. Structure analysis of the lignin indicated that the hydroxyl group content was reduced whereas the carbonyl group content increased. Both condensation and depolymerization takes place during the PMo12 oxidation of lignin. PMID:26692572

  18. Modeling of Spent Fuel Oxidation at Low Temperature

    SciTech Connect

    Poulesquen, Arnaud; Ferry, Cecile; Desgranges, Lionel

    2007-07-01

    During dry storage, the oxidation of the spent fuel in case of cladding and container failure (accidental scenario) could be detrimental for further handling of the spent fuel rod and for the safety of the facilities. Depending on whether the uranium dioxide is under the form of powder or pellet, irradiated or unirradiated, the weight gain curves do not present the same shape. To account for these different behaviours, two models have been developed. Firstly, the oxidation of unirradiated powders has been modelled based on the coexistence, during the oxidation, of two intermediate products, U{sub 4}O{sub 9} and U{sub 3}O{sub 7}. The comparison between the calculation and the literature data is good in terms of weight gain curves and chemical diffusion coefficient of oxygen within the two phases. Secondly, the oxidation of spent fuel fragments is approached by a convolution procedure between a grain oxidation model and an empirical parameter which represents the linear oxidation speed of grain boundary or an average distance able to cover the entire spent fuel fragment. This procedure of calculation allows in one hand to account for the incubation period noticed on unirradiated pellets or spent fuel and in another hand to link the empirical parameter to physical as porosity, cracks or linear power, or operational parameters such as fission gas release (FGR) respectively. A comparison of this new modelling with experimental data will be proposed. (authors)

  19. Hospital admissions due to diseases of arteries and veins peaked at physiological equivalent temperature -10 to 10 °C in Germany in 2009-2011.

    PubMed

    Shiue, Ivy; Perkins, David R; Bearman, Nick

    2016-04-01

    We aimed to understand relationships of the weather as biometeorological and hospital admissions due to diseases of arteries and veins by subtypes, which have been scarcely studied, in a national setting in recent years. This is an ecological study. Ten percent of daily hospital admissions from the included hospitals (n = 1,618) across Germany that were available between 1 January 2009 and 31 December 2011 (n = 5,235,600) were extracted from Statistisches Bundesamt, Germany. We identified I70-I79 Diseases of arteries, arterioles and capillaries and I80-I89 Diseases of veins, lymphatic vessels and lymph nodes by International Classification of Diseases version 10 as the study outcomes. Daily weather data from 64 weather stations that covered 13 German states including air temperature, humidity, wind speed, cloud cover, radiation flux and vapour pressure were obtained and generated into physiologically equivalent temperature (PET). Two-way fractional-polynomial prediction was plotted with 95 % confidence intervals. For most of the subtypes from diseases of arteries and veins, hospital admissions slightly peaked in spring and dropped when PET was at 10 °C. There were no other large differences across 12 months. Admissions of peripheral vascular diseases, arterial embolism and thrombosis, phlebitis and thrombophlebitis, oesophageal varices and nonspecific lymphadenitis peaked when PET was between 0 and -10 °C, while others peaked when PET was between 0 and 10 °C. More medical resources could have been needed on days when PETs were at -10 to 10 °C than on other days. Adaptation to such weather change for health professionals and the general public would seem to be imperative. PMID:26631019

  20. Deep Burn Develpment of Transuranic Fuel for High-Temperature Helium-Cooled Reactors - July 2010

    SciTech Connect

    Snead, Lance Lewis; Besmann, Theodore M; Collins, Emory D; Bell, Gary L

    2010-08-01

    The DB Program Quarterly Progress Report for April - June 2010, ORNL/TM/2010/140, was distributed to program participants on August 4. This report discusses the following: (1) TRU (transuranic elements) HTR (high temperature helium-cooled reactor) Fuel Modeling - (a) Thermochemical Modeling, (b) 5.3 Radiation Damage and Properties; (2) TRU HTR Fuel Qualification - (a) TRU Kernel Development, (b) Coating Development, (c) ZrC Properties and Handbook; and (3) HTR Fuel Recycle - (a) Recycle Processes, (b) Graphite Recycle, (c) Pyrochemical Reprocessing - METROX (metal recovery from oxide fuel) Process Development.

  1. Performance, durability and low temperature evaluation of sunflower oil as a diesel fuel extender

    SciTech Connect

    Baranescu, R.A.; Lusco, J.J.

    1982-01-01

    The paper presents the results of a research project to evaluate performance and durability of direct injection turbocharged diesel engines using sunflower oil and blends thereof. Alcaline refined sunflower oil and three different blends of sunflower oil and diesel fuel were comparatively tested against No. 2 diesel fuel for: physical and chemical characteristics, fuel injection system performance, short term engine performance, propensity to nozzle deposits buildup, limited durability operation and low temperature starting capability. Results are presented for the various phases of the project and correlations between the fuel characteristics and engine accept-ability are discussed. 19 figures, 2 tables.

  2. Charring temperatures are driven by the fuel types burned in a peatland wildfire

    PubMed Central

    Hudspith, Victoria A.; Belcher, Claire M.; Yearsley, Jonathan M.

    2014-01-01

    Peatlands represent a globally important carbon store; however, the human exploitation of this ecosystem is increasing both the frequency and severity of fires on drained peatlands. Yet, the interactions between the hydrological conditions (ecotopes), the fuel types being burned, the burn severity, and the charring temperatures (pyrolysis intensity) remain poorly understood. Here we present a post-burn assessment of a fire on a lowland raised bog in Co. Offaly, Ireland (All Saints Bog). Three burn severities were identified in the field (light, moderate, and deeply burned), and surface charcoals were taken from 17 sites across all burn severities. Charcoals were classified into two fuel type categories (either ground or aboveground fuel) and the reflectance of each charcoal particle was measured under oil using reflectance microscopy. Charcoal reflectance shows a positive relationship with charring temperature and as such can be used as a temperature proxy to reconstruct minimum charring temperatures after a fire event. Resulting median reflectance values for ground fuels are 1.09 ± 0.32%Romedian, corresponding to estimated minimum charring temperatures of 447°C ± 49°C. In contrast, the median charring temperatures of aboveground fuels were found to be considerably higher, 646°C ± 73°C (3.58 ± 0.77%Romedian). A mixed-effects modeling approach was used to demonstrate that the interaction effects of burn severity, as well as ecotope classes, on the charcoal reflectance is small compared to the main effect of fuel type. Our findings reveal that the different fuel types on raised bogs are capable of charring at different temperatures within the same fire, and that the pyrolysis intensity of the fire on All Saints Bog was primarily driven by the fuel types burning, with only a weak association to the burn severity or ecotope classes. PMID:25566288

  3. Porous nuclear fuel element for high-temperature gas-cooled nuclear reactors

    DOEpatents

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2011-03-01

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  4. Porous nuclear fuel element with internal skeleton for high-temperature gas-cooled nuclear reactors

    SciTech Connect

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2013-09-03

    Porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's), and to processes for fabricating them. Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, the nuclear fuel may be deposited inside of a highly porous skeletal structure made of, for example, reticulated vitreous carbon foam.

  5. Methods for manufacturing porous nuclear fuel elements for high-temperature gas-cooled nuclear reactors

    DOEpatents

    Youchison, Dennis L.; Williams, Brian E.; Benander, Robert E.

    2010-02-23

    Methods for manufacturing porous nuclear fuel elements for use in advanced high temperature gas-cooled nuclear reactors (HTGR's). Advanced uranium bi-carbide, uranium tri-carbide and uranium carbonitride nuclear fuels can be used. These fuels have high melting temperatures, high thermal conductivity, and high resistance to erosion by hot hydrogen gas. Tri-carbide fuels, such as (U,Zr,Nb)C, can be fabricated using chemical vapor infiltration (CVI) to simultaneously deposit each of the three separate carbides, e.g., UC, ZrC, and NbC in a single CVI step. By using CVI, a thin coating of nuclear fuel may be deposited inside of a highly porous skeletal structure made, for example, of reticulated vitreous carbon foam.

  6. Analysis of the Effect of Time, Temperature, and Fuel Age on Helium Release from 238-Plutonium Dioxide Fuel

    NASA Astrophysics Data System (ADS)

    Barklay, Chadwick D.; Kramer, Daniel P.; Ruhkamp, Joseph D.

    2005-02-01

    The compound 238-plutonium dioxide has been employed over the last several decades as the fuel of choice in fabricating nuclear powered thermal to electrical converters. The alpha decay of 238-plutonium results in the generation of helium ions as a function of time. While the quantity of helium formed within the fuel can be easily calculated, its diffusion and/or release mechanism as a function of time, temperature, fuel quantity and age needs to be characterized. Within the scope of this paper the principle interest centers on determining the expected quantity of helium that will be released from solid 238-plutonium dioxide fuel forms enclosed within a primary containment vessel (PCV) under Hypothetical Accident Conditions (HAC) as described in 10 CFR 71.73(4). Once the quantity of helium released during HAC has been determined, the partial pressure increase due to the helium release can be calculated for a given shipping configuration. This partial pressure increase due to helium release during HAC for a selected shipping configuration can then be used to determine if the structural integrity of the package will be maintained or compromised during HAC. However, it is important to recognize that helium release is not a function of a particular shipping package, but as shall be demonstrated is a function of time, temperature, and fuel quantity and age.

  7. Analysis of the Effect of Time, Temperature, and Fuel Age on Helium Release from 238-Plutonium Dioxide Fuel

    SciTech Connect

    Barklay, Chadwick D.; Kramer, Daniel P.; Ruhkamp, Joseph D.

    2005-02-06

    The compound 238-plutonium dioxide has been employed over the last several decades as the fuel of choice in fabricating nuclear powered thermal to electrical converters. The alpha decay of 238-plutonium results in the generation of helium ions as a function of time. While the quantity of helium formed within the fuel can be easily calculated, its diffusion and/or release mechanism as a function of time, temperature, fuel quantity and age needs to be characterized. Within the scope of this paper the principle interest centers on determining the expected quantity of helium that will be released from solid 238-plutonium dioxide fuel forms enclosed within a primary containment vessel (PCV) under Hypothetical Accident Conditions (HAC) as described in 10 CFR 71.73(4). Once the quantity of helium released during HAC has been determined, the partial pressure increase due to the helium release can be calculated for a given shipping configuration. This partial pressure increase due to helium release during HAC for a selected shipping configuration can then be used to determine if the structural integrity of the package will be maintained or compromised during HAC. However, it is important to recognize that helium release is not a function of a particular shipping package, but as shall be demonstrated is a function of time, temperature, and fuel quantity and age.

  8. Temperature and voltage responses of a molten carbonate fuel cell in the presence of a hydrogen fuel leakage

    NASA Astrophysics Data System (ADS)

    Law, M. C.; Liang, G. V. Y.; Lee, V. C. C.; Wee, S. K.

    2015-04-01

    A two dimensional (2-D), dynamic model of a molten carbonate fuel cell (MCFC) was developed using COMSOL Multi-physics. The model was used to investigate the dynamic behaviour of the MCFC in the presence of hydrogen fuel leakage. A leakage was modelled as a known outflow velocity at the anode gas channel. The effects of leakage velocity and the leakage location were investigated. The simulations show that anode electrode temperature increases as the leakage velocity increases. The voltage generated is shown to decrease at the start of the leakage occurrence due to loss of hydrogen gas. Later the voltage increases as the anode temperature increases. The results also show that the changes of temperature and voltage are more significant if a leakage occurs nearer to the inlet compared to that at the outlet of anode gas channel.

  9. Sensitivity Analysis of Fuel Centerline Temperatures in SuperCritical Water-cooled Reactors (SCWRs)

    NASA Astrophysics Data System (ADS)

    Abdalla, Ayman

    SuperCritical Water-cooled Reactors (SCWRs) are one of the six nuclear-reactor concepts currently being developed under the Generation-IV International Forum (GIF). A main advantage of SCW Nuclear Power Plants (NPPs) is that they offer higher thermal efficiencies compared to those of current conventional NPPs. Unlike today's conventional NPPs, which have thermal efficiencies between 30 - 35%, SCW NPPs will have thermal efficiencies within a range of 45 - 50%, owing to high operating temperatures and pressures (i.e., coolant temperatures as high as 625°C at 25 MPa pressure). The use of current fuel bundles with UO2 fuel at the high operating parameters of SCWRs may cause high fuel centerline temperatures, which could lead to fuel failure and fission gas release. Studies have shown that when the Variant-20 (43-element) fuel bundle was examined at SCW conditions, the fuel centerline temperature industry limit of 1850°C for UO2 and the sheath temperature design limit of 850°C might be exceeded. Therefore, new fuel-bundle designs, which comply with the design requirements, are required for future use in SCWRs. The main objective of this study to conduct a sensitivity analysis in order to identify the main factors that leads to fuel centerline temperature reduction. Therefore, a 54-element fuel bundle with smaller diameter of fuel elements compared to that of the 43-element bundle was designed and various nuclear fuels are examined for future use in a generic Pressure Tube (PT) SCWR. The 54-element bundle consists of 53 heated fuel elements with an outer diameter of 9.5 mm and one central unheated element of 20-mm outer diameter which contains burnable poison. The 54-element fuel bundle has an outer diameter of 103.45 mm, which is the same as the outer diameter of the 43-element fuel bundle. After developing the 54-element fuel bundle, one-dimensional heat-transfer analysis was conducted using MATLAB and NIST REFPROP programs. As a result, the Heat Transfer

  10. Liquid Fuel Production from Biomass via High Temperature Steam Electrolysis

    SciTech Connect

    Grant L. Hawkes; Michael G. McKellar

    2009-11-01

    A process model of syngas production using high temperature electrolysis and biomass gasification is presented. Process heat from the biomass gasifier is used to heat steam for the hydrogen production via the high temperature steam electrolysis process. Hydrogen from electrolysis allows a high utilization of the biomass carbon for syngas production. Oxygen produced form the electrolysis process is used to control the oxidation rate in the oxygen-fed biomass gasifier. Based on the gasifier temperature, 94% to 95% of the carbon in the biomass becomes carbon monoxide in the syngas (carbon monoxide and hydrogen). Assuming the thermal efficiency of the power cycle for electricity generation is 50%, (as expected from GEN IV nuclear reactors), the syngas production efficiency ranges from 70% to 73% as the gasifier temperature decreases from 1900 K to 1500 K. Parametric studies of system pressure, biomass moisture content and low temperature alkaline electrolysis are also presented.

  11. Effect of increased fuel temperature on emissions of oxides of nitrogen from a gas turbine combustor burning natural gas

    NASA Technical Reports Server (NTRS)

    Marchionna, N. R.

    1973-01-01

    An annular gas turbine combustor was tested with heated natural gas fuel to determine the effect of increasing fuel temperature on the formation of oxides of nitrogen. Fuel temperatures ranged from ambient to 800 K (980 F). Combustor pressure was 6 atmospheres and the inlet air temperature ranged from 589 to 894 K (600 to 1150 F). The NOx emission index increased with fuel temperature at a rate of 4 to 9 percent per 100 K (180 F), depending on the inlet air temperature. The rate of increase in NOx was lowest at the highest inlet air temperature tested.

  12. Computational fluid dynamics simulations of jet fuel flow near the freeze point temperature

    NASA Astrophysics Data System (ADS)

    Assudani, Rajee

    2006-12-01

    Under low-temperature environmental conditions, the cooling of aircraft fuel results in reduced fluidity with the potential for freezing. Therefore, it is important to study the flow and heat transfer phenomena that occur in an aircraft fuel tank near the freeze point temperature of jet fuels. The purpose of this dissertation is to study the effects of low temperatures on the flow, heat transfer and freezing of commercial and military jet fuels. The research is accomplished with the help of computational models of a thermal simulator tank and a quartz duct. Experimental results with the thermal simulator tank show that fuel flowability and pumpability decrease substantially as temperature is reduced. Time-dependent temperature and velocity distributions were numerically simulated for static cooling. Measured properties were used in all the computational fluid dynamics simulations. The calculations show that stringers, ribs, and other structures strongly promote fuel cooling. Also, the cooler, denser fuel resides near the bottom surface of the fuel tank simulator. The presence of an ullage space within the tank was found to strongly influence the fuel temperature profile by sometimes reducing cooling from the upper surface. Moreover, since the presence of ullage space is an explosion risk, some military aircraft fuel tanks are fitted with explosion suppressant polyurethane foam. To study the effect of foam on the flowability and heat transfer inside the simulator tank, the wing tank thermal simulator was filled with military specified polyurethane foam. The tank was simultaneously drained and cooled and the mass flow rate results showed that flowability of the fuel is not affected by the presence of foam. However, the presence of foam certainly affected the heat transfer phenomenon inside the fuel tank when the simulator tank was cooled and drained simultaneously. To study the freezing behavior of jet fuel under forced flow conditions, a quartz duct was fabricated

  13. Effect of particle size on activation energy and peak temperature of the thermoluminescence glow curve of undoped ZnS nanoparticles.

    PubMed

    Chandra, B P; Chandrakar, Raju Kumar; Chandra, V K; Baghel, R N

    2016-03-01

    This paper reports the effect of particle size on the thermoluminescence (TL) of undoped ZnS nanoparticles. ZnS nanoparticles were prepared using a chemical precipitation method in which mercaptoethanol was used as the capping agent. The nanoparticles were characterized by X-ray diffraction, field emission gun-scanning electron microscopy and high-resolution transmission electron microscopy. When the concentrations of mercaptoethanol used are 0, 0.005, 0.01, 0.015, 0.025, 0.040 and 0.060 M, the sizes of the nanoparticles are 2.86, 2.81, 2.69, 2.40, 2.10, 1.90 and 1.80 nm, respectively. Initially, the TL intensity of UV-irradiated ZnS nanoparticles increases with temperature, attains a peak value Im for a particular temperature Tm, and then decreases with further increases in temperature. The values of both Im and Tm increase with decreasing nanoparticle size. Whereas the activation energy decreases slightly with decreasing nanoparticle size, the frequency factor decreases significantly as the nanoparticle size is reduced. The order of kinetics for the TL glow curve of ZnS nanoparticles is 2. Expressions are derived for the dependence of activation energy (Ea) and Tm on nanoparticle size, and good agreement is found between the experimental and theoretical results. PMID:26332287

  14. Use of a commercial heat transfer code to predict horizontally oriented spent fuel rod surface temperatures

    SciTech Connect

    Wix, S.D.; Koski, J.A.

    1993-03-01

    Radioactive spent fuel assemblies are a source of hazardous waste that will have to be dealt with in the near future. It is anticipated that the spent fuel assemblies will be transported to disposal sites in spent fuel transportation casks. In order to design a reliable and safe transportation cask, the maximum cladding temperature of the spent fuel rod arrays must be calculated. A comparison between numerical calculations using commercial thermal analysis software packages and experimental data simulating a horizontally oriented spent fuel rod array was performed. Twelve cases were analyzed using air and helium for the fill gas, with three different heat dissipation levels. The numerically predicted temperatures are higher than the experimental data for all levels of heat dissipation with air as the fill gas. The temperature differences are 4{degree}C and 23{degree}C for the low heat dissipation and high heat dissipation, respectively. The temperature predictions using helium as a fill gas are lower for the low and medium heat dissipation levels, but higher at the high heat dissipation. The temperature differences are 1{degree}C and 6{degree}C for the low and medium heat dissipation, respectively. For the high heat dissipation level, the temperature predictions are 16{degree}C higher than the experimental data. Differences between the predicted and experimental temperatures can be attributed to several factors. These factors include experimental uncertainty in the temperature and heat dissipation measurements, actual convection effects not included in the model, and axial heat flow in the experimental data. This work demonstrates that horizontally oriented spent fuel rod surface temperature predictions can be made using existing commercial software packages. This work also shows that end effects will be increasingly important as the amount of dissipated heat increases.

  15. Experimental investigation on circumferential and axial temperature gradient over fuel channel under LOCA

    NASA Astrophysics Data System (ADS)

    Yadav, Ashwini Kumar; kumar, Ravi; Gupta, Akhilesh; Chatterjee, Barun; Mukhopadhyay, Deb; Lele, H. G.

    2014-06-01

    In a nuclear reactor temperature rises drastically in fuel channels under loss of coolant accident due to failure of primary heat transportation system. Present investigation has been carried out to capture circumferential and axial temperature gradients during fully and partially voiding conditions in a fuel channel using 19 pin fuel element simulator. A series of experiments were carried out by supplying power to outer, middle and center rods of 19 pin fuel simulator in ratio of 1.4:1.1:1. The temperature at upper periphery of pressure tube (PT) was slightly higher than at bottom due to increase in local equivalent thermal conductivity from top to bottom of PT. To simulate fully voided conditions PT was pressurized at 2.0 MPa pressure with 17.5 kW power injection. Ballooning initiated from center and then propagates towards the ends and hence axial temperature difference has been observed along the length of PT. For asymmetric heating, upper eight rods of fuel simulator were activated and temperature difference up-to 250 °C has been observed from top to bottom periphery of PT. Such situation creates steep circumferential temperature gradient over PT and could lead to breaching of PT under high pressure.

  16. New Optical Sensor Suite for Ultrahigh Temperature Fossil Fuel Applications

    SciTech Connect

    Russell G. May; Tony Peng; Gary Pickrell

    2005-10-31

    Development of practical, high-temperature optical claddings for improved waveguiding in sapphire fibers continued during the reporting period. A set of designed experiments using the Taguchi method was undertaken to efficiently determine the optimal set of processing variables to yield clad fibers with good optical and mechanical properties. Eighteen samples of sapphire fibers were prepared with spinel claddings, each with a unique set of variables. Statistical analyses of the results were then used to predict the set of factors that would result in a spinel cladding with the optimal geometrical, mechanical, and optical properties. To confirm the predictions of the Taguchi analysis, sapphire fibers were clad with the magnesium aluminate spinel coating using the predicted optimal set of factors. In general, the clad fibers demonstrated high quality, exceeding the best results obtained during the Phase I effort. Tests of the high-temperature stability of the clad fibers were also conducted. The results indicated that the clad fibers were stable at temperatures up to 1300 C for the duration of the three day test. At the higher temperatures, some changes in the geometry of the fibers were observed. The design, fabrication, and testing of a sapphire sensor for measurement of temperature was undertaken. The specific sensor configuration uses a polished sapphire wafer as the temperature-sensitive element. The wafer is attached to a sapphire fiber (clad or unclad), and interrogated as a Fabry-Perot sensor. Methods for assembling the sensor were investigated. A prototype sensor was fabricated and tested at room temperature and elevated temperatures. Results were difficult to interpret, due to the presence of modal noise which was found to result from the use of a spectrometer that was not designed for use with multimode fibers. A spectrometer optimized for use of multimode fiber has been obtained, and further evaluation of the sapphire temperature sensor is continuing.

  17. The Effects of Engine Speed and Mixture Temperature on the Knocking Characteristics of Several Fuels

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1940-01-01

    Six 100-octane and two 87-octane aviation engine fuels were tested in a modified C.F.R. variable-compression engine at 1,500, 2,000 and 2,500 rpm. The mixture temperature was raised from 50 to 300 F in approximately 50 degree steps and, at each temperature, the compression ratio was adjusted to give incipient knock as shown by a cathode ray indicator. The results are presented in tabular form. The results are analyzed on the assumption that the conditions which determine whether a given fuel will knock are the maximum values of density and temperature reached by the burning gases. A maximum permissible density factor, proportional to the maximum density of the burning gases just prior to incipient knock, and the temperature of the burning gases at that time were computed for each of the test conditions. Values of the density factors were plotted against the corresponding end-gas temperatures for the three engine speeds and also against engine speed for several and end-gas temperatures. The maximum permissible density factor varied only slightly with engine speed but decreased rapidly with an increase in the end-gas temperature. The effect of changing the mixture temperature was different for fuels of different types. The results emphasize the desirability of determining the anti knock values of fuels over a wide range of engine and intake-air conditions rather that at a single set of conditions.

  18. High temperature solid electrolyte fuel cell with ceramic electrodes

    DOEpatents

    Marchant, David D.; Bates, J. Lambert

    1984-01-01

    A solid oxide electrolyte fuel cell is described having a central electrolyte comprised of a HfO.sub.2 or ZrO.sub.2 ceramic stabilized and rendered ionically conductive by the addition of Ca, Mg, Y, La, Nd, Sm, Gd, Dy Er, or Yb. The electrolyte is sandwiched between porous electrodes of a HfO.sub.2 or ZrO.sub.2 ceramic stabilized by the addition of a rare earth and rendered electronically conductive by the addition of In.sub.2 O.sub.3. Alternatively, the anode electrode may be made of a metal such as Co, Ni, Ir Pt, or Pd.

  19. High temperature solid electrolyte fuel cell with ceramic electrodes

    DOEpatents

    Bates, J.L.; Marchant, D.D.

    A solid oxide electrolyte fuel cell is described having a central electrolyte comprised of a HfO/sub 2/ or ZrO/sub 2/ ceramic stabilized and rendered ionically conductive by the addition of Ca, Mg, Y, La, Nd, Sm, Gd, Dy Er, or Yb. The electrolyte is sandwiched between porous electrodes of a HfO/sub 2/ or ZrO/sub 2/ ceramic stabilized by the addition of a rare earth and rendered electronically conductive by the addition of In/sub 2/O/sub 3/. Alternatively, the anode electrode may be made of a metal such as Co, Ni, Ir Pt, or Pd.

  20. Low-temperature ignition of droplets of suspension organic water-carbon fuels

    NASA Astrophysics Data System (ADS)

    Nakoryakov, V. E.; Glushkov, D. O.; Kuznetsov, G. V.; Strizhak, P. A.

    2016-07-01

    The conditions and integral characteristics of stable low-temperature ignition of droplets of suspension organic water-coal fuels are established by using the means of high-speed video-detection. The oxidizer temperature for these conditions varies in the range of 600-900 K (much below the temperatures in furnace chambers of modern power installations exceeding 1200 K). The velocity of the oxidizer-flow motion varies from 0.5 to 5 m/s, and the sizes (conditional radii) of droplets vary from 0.5 to 1.5 mm. The times of initiation of burning under conditions of low-temperature heating and the duration of the complete combustion of droplets of the corresponding compositions of organic water-coal fuels are determined. The necessary and sufficient conditions of stable ignition are singled out for promising organic water-coal fuels.

  1. Determination of the Effects of Speed, Temperature, and Fuel Factors on Exhaust Emissions

    NASA Astrophysics Data System (ADS)

    Chou, Chia-Yang David

    1995-11-01

    This study provided a comprehensive approach to examining the relative significance and possible synergistic effects of speed, temperature, and fuel on mobile source emissions modeling. Eleven passenger vehicles from three fuel delivery system control groups were tested, namely, three from carburetor (CARBU), three from throttle body injection (TBI), and five from multi-port fuel injection (MPFI) group. A minimum of 90 tests were conducted on each vehicle with a random combination of three fuel types (Phase 1, Phase 2, and Indolene), three temperatures (50 F, 75 F, and 100 F), and ten speed cycles. Each vehicle was repeated for ten speed cycles (75 F and Indolene). In general, exhaust emissions descended in the order of CARBU, TBI, and MPFI. All vehicles in the CARBU group contained a "dead" catalyst, which probably explained why vehicles in CARBU were "high emitters.". Results from the paired t-test indicated that exhaust emissions difference between Phase 1 and Phase 2 fuels for all vehicles was significant. The net exhaust emissions reduction of Phase 2 over Phase 1 fuel for HC and NOx was 21% and 12%, respectively; which is in good agreements with the CARB projected 17% HC (including evaporative and exhaust emissions) and 11% CO emissions reduction based on 1996 calendar year when Phase 2 fuel is introduced. Temperature had minimal effects on exhaust emissions especially the test cycles were in hot-stabilized mode. Nevertheless, exhaust emissions from cold-start mode were higher than hot-start mode because the catalyst had not reached to optimal operating temperature during the cold-start mode. The relative contributions of speed, temperature, and fuel to exhaust emissions were determined using analysis of variance (ANOVA) and it was found interaction terms among fuel, speed, and temperature were statistically insignificant. Individually, the temperature and fuel factor played a minor role in exhaust emission modeling. Speed and vehicle type were the two

  2. NEW OPTICAL SENSOR SUITE FOR ULTRAHIGH TEMPERATURE FOSSIL FUEL APPLICATIONS

    SciTech Connect

    Russell G. May; Tony Peng; Tom Flynn

    2004-12-01

    Accomplishments during the Phase I of a program to develop and demonstrate technology for the instrumentation of advanced powerplants are described. Engineers from Prime Research, LC and Babcock and Wilcox Research Center collaborated to generate a list of potential applications for robust photonic sensors in existing and future boiler plants. From that list, three applications were identified as primary candidates for initial development and demonstration of high-temperature sensors in an ultrasupercritical power plant. A matrix of potential fiber optic sensor approaches was derived, and a data set of specifications for high-temperature optical fiber was produced. Several fiber optic sensor configurations, including interferometric (extrinsic and intrinsic Fabry-Perot interferometer), gratings (fiber Bragg gratings and long period gratings), and microbend sensors, were evaluated in the laboratory. In addition, progress was made in the development of materials and methods to apply high-temperature optical claddings to sapphire fibers, in order to improve their optical waveguiding properties so that they can be used in the design and fabrication of high-temperature sensors. Through refinements in the processing steps, the quality of the interface between core and cladding of the fibers was improved, which is expected to reduce scattering and attenuation in the fibers. Numerical aperture measurements of both clad and unclad sapphire fibers were obtained and used to estimate the reduction in mode volume afforded by the cladding. High-temperature sensors based on sapphire fibers were also investigated. The fabrication of an intrinsic Fabry-Perot cavity within sapphire fibers was attempted by the bulk diffusion of magnesium oxide into short localized segments of longer sapphire fibers. Fourier analysis of the fringes that resulted when the treated fiber was interrogated by a swept laser spectrometer suggested that an intrinsic cavity had been formed in the fiber. Also

  3. Temperature Distributions in LMR Fuel Pin Bundles as Modeled by COBRA-IV-I

    NASA Astrophysics Data System (ADS)

    Wright, Steven A.; Stout, Sherry

    2005-02-01

    Most pin type reactor designs for space power or terrestrial applications group the fuel pins into a number of relatively large fuel pin bundles or subassemblies. Fuel bundles for terrestrial liquid metal fast breeders reactors typically use 217 - 271 pins per sub-assembly, while some SP100 designs use up to 331 pins in a central subassembly that was surrounded by partial assemblies. Because thermal creep is exponentially related to temperature, small changes in fuel pin cladding temperature can make large differences in the lifetime in a high temperature liquid metal reactor (LMR). This paper uses the COBRA-IV-I computer code to determine the temperature distribution within LMR fuel bundles. COBRA-IV-I uses the sub-channel analysis approach to determine the enthalpy (or temperature) and flow distribution in rod bundles for both steady-state and transient conditions. The COBRA code runs in only a few seconds and has been benchmarked and tested extensively over a wide range of flow conditions. In this report the flow and temperature distributions for two types of lithium cooled space reactor core designs were calculated. One design uses a very tight fuel pin packing that has a pitch to diameter ratio of 1.05 (small wire wrap with a diameter of 392 μm) as proposed in SP100. The other design uses a larger pitch to diameter ratio of 1.09 with a larger more conventional sized wire wrap diameter of 1 mm. The results of the COBRA pin bundle calculations show that the larger pitch-to-diameter fuel bundle designs are more tolerant to local flow blockages, and in addition they are less sensitive to mal-flow distributions that occur near the edges of the subassembly.

  4. Temperature Distributions in LMR Fuel Pin Bundles as Modeled by COBRA-IV-I

    SciTech Connect

    Wright, Steven A.; Stout, Sherry

    2005-02-06

    Most pin type reactor designs for space power or terrestrial applications group the fuel pins into a number of relatively large fuel pin bundles or subassemblies. Fuel bundles for terrestrial liquid metal fast breeders reactors typically use 217 - 271 pins per sub-assembly, while some SP100 designs use up to 331 pins in a central subassembly that was surrounded by partial assemblies. Because thermal creep is exponentially related to temperature, small changes in fuel pin cladding temperature can make large differences in the lifetime in a high temperature liquid metal reactor (LMR). This paper uses the COBRA-IV-I computer code to determine the temperature distribution within LMR fuel bundles. COBRA-IV-I uses the sub-channel analysis approach to determine the enthalpy (or temperature) and flow distribution in rod bundles for both steady-state and transient conditions. The COBRA code runs in only a few seconds and has been benchmarked and tested extensively over a wide range of flow conditions. In this report the flow and temperature distributions for two types of lithium cooled space reactor core designs were calculated. One design uses a very tight fuel pin packing that has a pitch to diameter ratio of 1.05 (small wire wrap with a diameter of 392 {mu}m) as proposed in SP100. The other design uses a larger pitch to diameter ratio of 1.09 with a larger more conventional sized wire wrap diameter of 1 mm. The results of the COBRA pin bundle calculations show that the larger pitch-to-diameter fuel bundle designs are more tolerant to local flow blockages, and in addition they are less sensitive to mal-flow distributions that occur near the edges of the subassembly.

  5. Novel Electrode Materials for Low-Temperature Solid-Oxide Fuel Cells

    SciTech Connect

    Shaowu Zha; Meilin Liu

    2005-03-23

    Composites electrodes consisting of silver and bismuth vanadates exhibit remarkable catalytic activity for oxygen reduction at 500-550 C and greatly reduce the cathode-electrolyte (doped ceria) resistances of low temperature SOFCs, down to about 0.53 {omega}cm{sup 2} at 500 C and 0.21 {omega}cm{sup 2} at 550 C. The observed power densities of 231, 332, and 443 mWcm-2 at 500, 525 and 550 C, respectively, make it possible to operate SOFCs at temperatures about 500 C. Fuel cell performance depends strongly on the anode microstructure, which is determined by the anode compositions and fabrication conditions. Four types of anodes with two kinds of NiO and GDC powders were investigated. By carefully adjusting the anode microstructure, the GDC electrolyte/anode interfacial polarization resistances reduced dramatically. The interfacial resistance at 600 C decreased from 1.61 {omega} cm{sup 2} for the anodes prepared using commercially available powders to 0.06 {omega} cm{sup 2} for those prepared using powders derived from a glycine-nitrate process. Although steam reforming or partial oxidation is effective in avoiding carbon deposition of hydrocarbon fuels, it increases the operating cost and reduces the energy efficiency. Anode-supported SOFCs with an electrolyte of 20 {micro}m-thick Gd-doped ceria (GDC) were fabricated by co-pressing. A catalyst (1 %wt Pt dispersed on porous Gd-doped ceria) for pre-reforming of propane was developed with relatively low steam to carbon (S/C) ratio ({approx}0.5), coupled with direct utilization of the reformate in low-temperature SOFCs. Propane was converted to smaller molecules during pre-reforming, including H{sub 2}, CH{sub 4}, CO, and CO{sub 2}. A peak power density of 247 mW/cm{sup 2} was observed when pre-reformed propane was directly fed to an SOFC operated at 600 C. No carbon deposition was observed in the fuel cell for a continuous operation of 10 hours at 600 C. The ability of producing vastly different microstructures and

  6. Novel Method for Measuring Temperature Distribution within Fuel Cell using Microsensors

    NASA Astrophysics Data System (ADS)

    Lee, Chi-Yuan; Hsieh, Chi-Lieh; Wu, Guan-Wei

    2007-05-01

    A fuel cell has the potential to become an important source of electric power. However, measuring the temperature inside the fuel cell is difficult. Hence, in this investigation, an array of microsensors is set up inside the fuel cell to measure the temperature distribution. The substrate of a bipolar plate in the fuel cell is stainless steel (SS-316) and an electroforming technique is implemented to fabricate channels in the stainless steel substrate. Then micro-electro-mechanical system (MEMS) technologies are employed to fabricate a platinum temperature sensor on the rib of a channel in the stainless steel substrate. In this experiment, the temperature of microsensor is measured to range from 31 to 80 °C and its resistance ranges from 0.593 to 0.649 Ω. Experimental results demonstrate that temperature is almost linearly related to resistance and that accuracy and sensitivity are 0.5 °C and 1.93× 10-3/°C, respectively. The performance curves of a single fuel cell operating at 34 °C and H2/O2 gas flow rates of 50/50 ml/min are determined. The maximum power density is 170 mW/cm2 and the current density is 513 mA/cm2.

  7. Ignition of blended-fuel droplet in high-temperature atmosphere

    SciTech Connect

    Takei, M.; Tsukamoto, T.; Niioka, T. )

    1993-04-01

    Ignition time of a suspended fuel droplet is obtained experimentally with high ambient temperature. A stationary fuel droplet suspended by a fine silica fiber is taken into a furnace moving on rail and is quickly exposed to high ambient temperature. Blended fuels of n-heptane and n-hexadecane are used, and the effects of fuel mixture ratio, initial droplet diameter, and ambient air temperature on ignition time are observed. For pure hexadecane droplets, ignition time increases with the increase in initial droplet diameter. On the other hand, it decreases for pure heptane, especially under lower ambient temperatures. For the case of mixed fuel, the variation of ignition time with the initial droplet diameter has a characteristic feature, namely the results show that an initial droplet diameter exists at which the ignition time has the maximum value and that this diameter increases with a decrease of the heptane concentration or the ambient temperature. The maximum ignition time is also confirmed by the combination of ethylalcohol and decylalcohol.

  8. Photo-Activated Low Temperature, Micro Fuel Cell Power Source

    SciTech Connect

    Harry L. Tuller

    2007-03-30

    A Key objective of this program is to identify electrodes that will make it possible to significantly reduce the operating temperature of micro-SOFC and thin film-based SOFCs. Towards this end, efforts are directed towards: (a) identifying the key rate limiting steps which limit presently utilized electrodes from performing at reduced temperatures, as well as, (b) investigating the use of optical, as opposed to thermal energy, as a means for photocatalyzing electrode reactions and enabling reduced operating temperatures. During Phase I, the following objectives were achieved: (a) assembly and testing of our unique Microprobe Thin Film Characterization System; (b) fabrication of the model cathode materials system in thin film form by both PLD and ink jet printing; and (c) the successful configuration and testing of the model materials as cathodes in electrochemical cells. A further key objective (d) to test the potential of illumination in enhancing electrode performance was also achieved.

  9. NEW OPTICAL SENSOR SUITE FOR ULTRAHIGH TEMPERATURE FOSSIL FUEL APPLICATIONS

    SciTech Connect

    Russell G. May; Tony Peng; Tom Flynn

    2004-04-01

    Accomplishments during the first six months of a program to develop and demonstrate technology for the instrumentation of advanced powerplants are described. Engineers from Prime Research, LC and Babcock and Wilcox Research Center collaborated to generate a list of potential applications for robust photonic sensors in existing and future boiler plants. From that list, three applications were identified as primary candidates for initial development and demonstration of high-temperature sensors in an ultrasupercritical power plant. In addition, progress was made in the development of materials and methods to apply high-temperature optical claddings to sapphire fibers, in order to improve their optical waveguiding properties so that they can be used in the design and fabrication of high-temperature sensors. Through refinements in the processing steps, the quality of the interface between core and cladding of the fibers was improved, which is expected to reduce scattering and attenuation in the fibers.

  10. Durability of symmetrically and asymmetrically porous polybenzimidazole membranes for high temperature proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Jheng, Li-Cheng; Chang, Wesley Jen-Yang; Hsu, Steve Lien-Chung; Cheng, Po-Yang

    2016-08-01

    Two types of porous polybenzimidazole (PBI) membranes with symmetric and asymmetric morphologies were fabricated by the template-leaching method and characterized by scanning electron microscope (SEM). Their physicochemical properties were compared in terms of acid-doping level, proton conductivity, mechanical strength, and oxidative stability. The durability of fuel cell operation is one of the most challenging for the PBI based membrane electrode assembly (MEA) used in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). In the present work, we carried out a long-term steady-state fuel cell test to compare the effect of membrane structure on the cell voltage degradation. It has also been demonstrated that the asymmetrically porous PBI could bring some notable improvements on the durability of fuel cell operation, the fuel crossover problem, and the phosphoric acid leakage.

  11. High temperature gas-cooled reactor (HTGR) graphite pebble fuel: Review of technologies for reprocessing

    SciTech Connect

    Mcwilliams, A. J.

    2015-09-08

    This report reviews literature on reprocessing high temperature gas-cooled reactor graphite fuel components. A basic review of the various fuel components used in the pebble bed type reactors is provided along with a survey of synthesis methods for the fabrication of the fuel components. Several disposal options are considered for the graphite pebble fuel elements including the storage of intact pebbles, volume reduction by separating the graphite from fuel kernels, and complete processing of the pebbles for waste storage. Existing methods for graphite removal are presented and generally consist of mechanical separation techniques such as crushing and grinding chemical techniques through the use of acid digestion and oxidation. Potential methods for reprocessing the graphite pebbles include improvements to existing methods and novel technologies that have not previously been investigated for nuclear graphite waste applications. The best overall method will be dependent on the desired final waste form and needs to factor in the technical efficiency, political concerns, cost, and implementation.

  12. An earthquake transient method for pebble-bed reactors and a fuel temperature model for TRISO fueled reactors

    NASA Astrophysics Data System (ADS)

    Ortensi, Javier

    This investigation is divided into two general topics: (1) a new method for analyzing the safe shutdown earthquake event in a pebble bed reactor core, and (2) the development of an explicit tristructural-isotropic fuel model for high temperature reactors. The safe shutdown earthquake event is one of the design basis accidents for the pebble bed reactor. The new method captures the dynamic geometric compaction of the pebble bed core. The neutronic and thermal-fluids grids are dynamically re-meshed to simulate the re-arrangement of the pebbles in the reactor during the earthquake. Results are shown for the PBMR-400 assuming it is subjected to the Idaho National Laboratory's design basis earthquake. The study concludes that the PBMR-400 can safely withstand the reactivity insertions induced by the slumping of the core and the resulting relative withdrawal of the control rods. This characteristic stems from the large negative Doppler feedback of the fuel. This Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated, high-temperature reactors that use fuel based on TRISO particles. The correct prediction of the magnitude and time-dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. An explicit TRISO fuel temperature model named THETRIS has been developed in this work and incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes. The new model yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume. The performance of the code during fast and moderately-slow transients is verified. These analyses show how explicit TRISO models improve the predictions of the fuel temperature, and consequently, of the power escalation. In addition, a brief study of the potential effects on the transient behavior of high-temperature reactors due to the presence of a gap inside the TRISO particles is included

  13. Development of low temperature solid oxide fuel cells

    SciTech Connect

    Bakker, W.T.; Goldstein, R.

    1996-12-31

    The historical focus of the electric utility industry has been central station power plants. These plants are usually sited outside urban areas and electricity was delivered via high voltage transmission lines. Several things are beginning to change this historical precedent One is the popular concern with EMF as a health hazard. This has rendered the construction of new lines as well as upgrading old ones very difficult. Installation of power generating equipment near the customer enables the utility to better utilize existing transmission and distribution networks and defer investments. Power quality and lark of disturbances and interruptions is also becoming increasingly more important to many customers. Grid connected, but dedicated small power plants can greatly improve power quality. Finally the development of high efficiency, low emission, modular fuel cells promises near pollution free localized power generation with an efficiency equal to or exceeding that of even the most efficient central power stations.

  14. Infrared spectroscopic and conductivity studies of ureasil-based proton conducting membranes for medium temperature fuel cell applications.

    PubMed

    Vince, Jelica; Vuk, Angela Šurca; Stangar, Urška Lavrenčič; Perše, Lidija Slemenik; Orel, Boris; Hočevar, Stanko

    2010-12-01

    Proton conducting membranes for fuel cells were prepared by the sol-gel process from two different ureasil organic-inorganic hybrid precursors: bis[(N-(3-triethoxysilylpropyl)ureido]-terminated poly(propylene glycol) 4000 (PPGU) and bis[3-(N-(3-triethoxysilylpropyl)ureido)propyl]-terminated poly(dimethylsiloxane) 1000 (PDMSU). Heteropoly silicotungstic acid was added to actuate the reactions of hydrolysis and condensation and to introduce proton conductivity. XRD measurements of membranes revealed the presence of a diffraction peak at 6.3°, which could be ascribed to gradual formation of R-(SiO3/2) silsesquioxane clusters, i.e. arrangement of the Si-O-Si skeleton on the nano-scale. TG and DSC measurements showed thermal stability of the membranes above 120 °C. Proton conductivities at room temperature were of the order of 10-4 to 10-3 S/cm, classifying the membranes in the group of super ionic conductors. At elevated temperatures up to 160 °C and at conditions of autogenous pressure, conductivities increased up to values acceptable for fuel cells of 10-1 S/cm, which could be the result of the presence of H3O+ ions. The protonation of the urea groups and the formation of amidonium ions [C(OH)=NH+] were followed using IR ATR spectroscopy. PMID:24061888

  15. Proposal of the Atmospheric Pressure Turbine (APT) and High Temperature Fuel Cell Hybrid System

    NASA Astrophysics Data System (ADS)

    Tsujikawa, Yoshiharu; Kaneko, Ken-Ichi; Suzuki, Jun

    Solid oxide fuel cell (SOFC) has been extensively developed in many countries as an ultra-high efficient energy converter. Such high temperature fuel cell can be operated as a hybrid system of integrating of turbo machinery. A major decision is whether to place the cell stack in pressurized or unpressurized section. This paper discusses the exhaust energy recovery from fuel cells by use of turbo machines under unpressurized conditions, working with inverted Brayton cycle in which turbine expansion, cooling by heat exchanger and draft by compressor are made in an open cycle mode. It is denoted as “atmospheric pressure turbine (APT)”.

  16. 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.

  17. Full-length high-temperature severe fuel damage test No. 5

    SciTech Connect

    Lanning, D.D.; Lombardo, N.J.; Hensley, W.K.; Fitzsimmons, D.E.; Panisko, F.E.; Hartwell, J.K.

    1993-09-01

    This report describes and presents data from a severe fuel damage test that was conducted in the National Research Universal (NRU) reactor at Chalk River Nuclear Laboratories (CRNL), Ontario, Canada. The test, designated FLHT-5, was the fourth in a series of full-length high-temperature (FLHT) tests on light-water reactor fuel. The tests were designed and performed by staff from the US Department of Energy`s Pacific Northwest Laboratory (PNL), operated by Battelle Memorial Institute. The test operation and test results are described in this report. The fuel bundle in the FLHT-5 experiment included 10 unirradiated full-length pressurized-water reactor (PWR) rods, 1 irradiated PWR rod and 1 dummy gamma thermometer. The fuel rods were subjected to a very low coolant flow while operating at low fission power. This caused coolant boilaway, rod dryout and overheating to temperatures above 2600 K, severe fuel rod damage, hydrogen generation, and fission product release. The test assembly and its effluent path were extensively instrumented to record temperatures, pressures, flow rates, hydrogen evolution, and fission product release during the boilaway/heatup transient. Post-test gamma scanning of the upper plenum indicated significant iodine and cesium release and deposition. Both stack gas activity and on-line gamma spectrometer data indicated significant ({approximately}50%) release of noble fission gases. Post-test visual examination of one side of the fuel bundle revealed no massive relocation and flow blockage; however, rundown of molten cladding was evident.

  18. High Temperature Corrosion Problem of Boiler Components in presence of Sulfur and Alkali based Fuels

    NASA Astrophysics Data System (ADS)

    Ghosh, Debashis; Mitra, Swapan Kumar

    2011-04-01

    Material degradation and ageing is of particular concern for fossil fuel fired power plant components. New techniques/approaches have been explored in recent years for Residual Life assessment of aged components and material degradation due to different damage mechanism like creep, fatigue, corrosion and erosion etc. Apart from the creep, the high temperature corrosion problem in a fossil fuel fired boiler is a matter of great concern if the fuel contains sulfur, chlorine sodium, potassium and vanadium etc. This paper discusses the material degradation due to high temperature corrosion in different critical components of boiler like water wall, superheater and reheater tubes and also remedial measures to avoid the premature failure. This paper also high lights the Residual Life Assessment (RLA) methodology of the components based on high temperature fireside corrosion. of different critical components of boiler.

  19. The coupling influence of airflow and temperature on the wall-wetted fuel film distribution

    SciTech Connect

    Cheng, Yong-sheng; Deng, Kangyao; Li, Tao

    2010-02-15

    The coupling influence of airflow and temperature on the two-dimensional distribution of the film resulted from fuel spray impinging on a horizontal flat wall was studied with experiments. The horizontal airflow direction was perpendicular to the vertical axis of the injection spray. The results show that, as air velocity increases, the film shape turns from a circle to an oblong. As wall temperature increases, the film area shrinks. Film thickness decreases as wall temperature or air velocity increases. The boiling point of the fuel is an important temperature to affect the film area and the film thickness. Film center moves more far away in the downstream direction as air velocity increases. For a certain air velocity, film center moves less far away as wall temperature increases. (author)

  20. Combustion studies of coal derived solid fuels by thermogravimetric analysis. III. Correlation between burnout temperature and carbon combustion efficiency

    USGS Publications Warehouse

    Rostam-Abadi, M.; DeBarr, J.A.; Chen, W.T.

    1990-01-01

    Burning profiles of 35-53 ??m size fractions of an Illinois coal and three partially devolatilized coals prepared from the original coal were obtained using a thermogravimetric analyzer. The burning profile burnout temperatures were higher for lower volatile fuels and correlated well with carbon combustion efficiencies of the fuels when burned in a laboratory-scale laminar flow reactor. Fuels with higher burnout temperatures had lower carbon combustion efficiencies under various time-temperature conditions in the laboratory-scale reactor. ?? 1990.

  1. Promotion of Oxygen Reduction by Exsolved Silver Nanoparticles on a Perovskite Scaffold for Low-Temperature Solid Oxide Fuel Cells.

    PubMed

    Zhu, Yinlong; Zhou, Wei; Ran, Ran; Chen, Yubo; Shao, Zongping; Liu, Meilin

    2016-01-13

    Solid oxide fuel cells (SOFCs) have potential to be the cleanest and most efficient electrochemical energy conversion devices with excellent fuel flexibility. To make SOFC systems more durable and economically competitive, however, the operation temperature must be significantly reduced, which depends sensitively on the development of highly active electrocatalysts for oxygen reduction reaction (ORR) at low temperatures. Here we report a novel silver nanoparticle-decorated perovskite oxide, prepared via a facile exsolution process from a Sr0.95Ag0.05Nb0.1Co0.9O3-δ (SANC) perovskite precursor, as a highly active and robust ORR electrocatalyst for low-temperature SOFCs. The exsolved Sr0.95Ag0.05Nb0.1Co0.9O3-δ (denoted as e-SANC) electrode is very active for ORR, achieving a very low area specific resistance (∼0.214 Ω cm(2) at 500 °C). An anode-supported cell with the new heterostructured cathode demonstrates very high peak power density (1116 mW cm(-2) at 500 °C) and stable operation for 140 h at a current density of 625 mA cm(-2). The superior ORR activity and stability are attributed to the fast oxygen surface exchange kinetics and the firm adhesion of the Ag nanoparticles to the Sr0.95Nb0.1Co0.9O3-δ (SNC0.95) support. Moreover, the e-SANC cathode displays improved tolerance to CO2. These unique features make the new heterostructured material a highly promising cathode for low-temperature SOFCs. PMID:26619096

  2. Kidney stone ablation times and peak saline temperatures during Holmium:YAG and Thulium fiber laser lithotripsy, in vitro, in a ureteral model

    NASA Astrophysics Data System (ADS)

    Hardy, Luke A.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

    2015-02-01

    Using a validated in vitro ureter model for laser lithotripsy, the performance of an experimental Thulium fiber laser (TFL) was studied and compared to clinical gold standard Holmium:YAG laser. The Holmium laser (λ = 2120 nm) was operated with standard parameters of 600 mJ, 350 μs, 6 Hz, and 270-μm-core optical fiber. TFL (λ = 1908 nm) was operated with 35 mJ, 500 μs, 150-500 Hz, and 100-μm-core fiber. Urinary stones (60% calcium oxalate monohydrate / 40% calcium phosphate), of uniform mass and diameter (4-5 mm) were laser ablated with fibers through a flexible video-ureteroscope under saline irrigation with flow rates of 22.7 ml/min and 13.7 ml/min for the TFL and Holmium laser, respectively. The temperature 3 mm from tube's center and 1 mm above mesh sieve was measured by a thermocouple and recorded during experiments. Total laser and operation times were recorded once all stone fragments passed through a 1.5-mm sieve. Holmium laser time measured 167 +/- 41 s (n = 12). TFL times measured 111 +/- 49 s, 39 +/- 11 s, and 23 +/- 4 s, for pulse rates of 150, 300, and 500 Hz (n = 12 each). Mean peak saline irrigation temperatures reached 24 +/- 1 °C for Holmium, and 33 +/- 3 °C, 33 +/- 7 °C, and 39 +/- 6 °C, for TFL at pulse rates of 150, 300, and 500 Hz. To avoid thermal buildup and provide a sufficient safety margin, TFL lithotripsy should be performed with pulse rates below 500 Hz and/or increased saline irrigation rates. The TFL rapidly fragmented kidney stones due in part to its high pulse rate, high power density, high average power, and reduced stone retropulsion, and may provide a clinical alternative to the conventional Holmium laser for lithotripsy.

  3. Hospital admissions of hypertension, angina, myocardial infarction and ischemic heart disease peaked at physiologically equivalent temperature 0°C in Germany in 2009-2011.

    PubMed

    Shiue, Ivy; Perkins, David R; Bearman, Nick

    2016-01-01

    We aimed to understand and to provide evidence on relationships of the weather as biometeorological and hospital admissions due to hypertension, angina, myocardial infarction and ischemic heart disease in a national setting in recent years that might help indicate when to expect more admissions for health professionals and the general public. This is an ecological study. Ten percent of daily hospital admissions from the included hospitals (n = 1618) across Germany that were available between 1 January 2009 and 31 December 2011 (n = 5,235,600) were extracted from Statistisches Bundesamt, Germany. We identified I11 hypertensive heart disease, I13 hypertensive heart and renal disease, I15 secondary hypertension, I20 angina pectoris, I21 acute myocardial infarction and I25 chronic ischemic heart disease by International Classification of Diseases version 10 as the study outcomes. Daily weather data from 64 weather stations that covered 13 German States including air temperature, humidity, wind speed, cloud cover, radiation flux and vapour pressure were obtained and generated into physiologically equivalent temperature (PET). Two-way fractional-polynomial prediction was plotted with 95% confidence intervals. Hospital admissions of hypertension, angina, myocardial infarction, heart disease peaked in winter and early spring when PETs were around 0°C. Admissions had an apparent drop when PETs reached 10°C. More medical resources could have been needed on days when PETs were around 0°C than on other days. While adaptation to such weather change for health professionals and the general public would seem to be imperative, future research with a longitudinal monitoring would still be needed. PMID:26286805

  4. Processing of FRG high-temperature gas-cooled reactor fuel elements at General Atomic under the US/FRG cooperative agreement for spent fuel elements

    SciTech Connect

    Holder, N.D.; Strand, J.B.; Schwarz, F.A.; Drake, R.N.

    1981-11-01

    The Federal Republic of Germany (FRG) and the United States (US) are cooperating on certain aspects of gas-cooled reactor technology under an umbrella agreement. Under the spent fuel treatment development section of the agreement, both FRG mixed uranium/ thorium and low-enriched uranium fuel spheres have been processed in the Department of Energy-sponsored cold pilot plant for high-temperature gas-cooled reactor (HTGR) fuel processing at General Atomic Company in San Diego, California. The FRG fuel spheres were crushed and burned to recover coated fuel particles suitable for further treatment for uranium recovery. Successful completion of the tests described in this paper demonstrated certain modifications to the US HTGR fuel burining process necessary for FRG fuel treatment. Results of the tests will be used in the design of a US/FRG joint prototype headend facility for HTGR fuel.

  5. MATERIALS SYSTEM FOR INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELL

    SciTech Connect

    Uday B. Pal; Srikanth Gopalan

    2004-02-15

    AC complex impedance spectroscopy studies were conducted on symmetrical cells of the type [gas, electrode/LSGM electrolyte/electrode, gas]. The electrode materials were slurry-coated on both sides of the LSGM electrolyte support. The electrodes selected for this investigation are candidate materials for SOFC electrodes. Cathode materials include La{sub 1-x}Sr{sub x}MnO{sub 3} (LSM), LSCF (La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3}), a two-phase particulate composite consisting of LSM + doped-lanthanum gallate (LSGM), and LSCF + LSGM. Pt metal electrodes were also used for the purpose of comparison. Anode material investigated was the Ni + GDC composite. The study revealed important details pertaining to the charge-transfer reactions that occur in such electrodes. The information obtained can be used to design electrodes for intermediate temperature SOFCs based on LSGM electrolyte.

  6. STABLE HIGH CONDUCTIVITY BILAYERED ELECTROLYTES FOR LOW TEMPERATURE SOLID OXIDE FUEL CELLS

    SciTech Connect

    Eric D. Wachsman; Keith L. Duncan

    2001-09-30

    Solid oxide fuel cells (SOFCs) are the future of energy production in America. They offer great promise as a clean and efficient process for directly converting chemical energy to electricity while providing significant environmental benefits (they produce negligible hydrocarbons, CO, or NO{sub x} and, as a result of their high efficiency, produce about one-third less CO{sub 2} per kilowatt hour than internal combustion engines). Unfortunately, the current SOFC technology, based on a stabilized zirconia electrolyte, must operate in the region of 1000 C to avoid unacceptably high ohmic losses. These high temperatures demand (a) specialized (expensive) materials for the fuel cell interconnects and insulation, (b) time to heat up to the operating temperature and (c) energy input to arrive at the operating temperature. Therefore, if fuel cells could be designed to give a reasonable power output at low to intermediate1 temperatures tremendous benefits may be accrued. At low temperatures, in particular, it becomes feasible to use ferritic steel for interconnects instead of expensive and brittle ceramic materials such as those based on LaCrO{sub 3}. In addition, sealing the fuel cell becomes easier and more reliable; rapid start-up is facilitated; thermal stresses (e.g., those caused by thermal expansion mismatches) are reduced; radiative losses ({approx}T{sup 4}) become minimal; electrode sintering becomes negligible and (due to a smaller thermodynamic penalty) the SOFC operating cycle (heating from ambient) would be more efficient. Combined, all these improvements further result in reduced initial and operating costs. The problem is, at lower temperatures the conductivity of the conventional stabilized zirconia electrolyte decreases to the point where it cannot supply electrical current efficiently to an external load. The primary objectives of the proposed research are to develop a stable high conductivity (> 0.05 S cm{sup -1} at {le} 550 C) electrolyte for lower

  7. High temperature electrolyzer/fuel cell power cycle: Preliminary design considerations

    NASA Technical Reports Server (NTRS)

    Morehouse, Jeffrey H.

    1987-01-01

    A model of a high temperature electrolyzer/fuel cell, hydrogen/oxygen, thermally regenerative power cycle is developed and used to simulate system performance for varying system parameters. Initial estimates of system efficiency, weight, and volume are provided for a one KWe module assuming specific electrolyzer and fuel cell characteristics, both current and future. Specific interest is placed on examining the system responses to changes in device voltage versus current density operating curves, and the associated optimum operating ranges. The performance of a solar-powered, space based system in low earth orbit is examined in terms of the light-dark periods requiring storage. The storage design tradeoffs between thermal energy, electrical energy, and hydrogen/oxygen mass storage are examined. The current technology module is based on the 1000 C solid oxide electrolyzer cell and the alkaline fuel cell. The Future Technology system examines benefits involved with developing a 1800K electrolyzer operating with an advanced fuel cell.

  8. Investigation of Bio-Diesel Fueled Engines under Low-Temperature Combustion Strategies

    SciTech Connect

    Chia-fon F. Lee; Alan C. Hansen

    2010-09-30

    In accordance with meeting DOE technical targets this research was aimed at developing and optimizing new fuel injection technologies and strategies for the combustion of clean burning renewable fuels in diesel engines. In addition a simultaneous minimum 20% improvement in fuel economy was targeted with the aid of this novel advanced combustion system. Biodiesel and other renewable fuels have unique properties that can be leveraged to reduce emissions and increase engine efficiency. This research is an investigation into the combustion characteristics of biodiesel and its impacts on the performance of a Low Temperature Combustion (LTC) engine, which is a novel engine configuration that incorporates technologies and strategies for simultaneously reducing NOx and particulate emissions while increasing engine efficiency. Generating fundamental knowledge about the properties of biodiesel and blends with petroleum-derived diesel and their impact on in-cylinder fuel atomization and combustion processes was an important initial step to being able to optimize fuel injection strategies as well as introduce new technologies. With the benefit of this knowledge experiments were performed on both optical and metal LTC engines in which combustion and emissions could be observed and measured under realistic conditions. With the aid these experiments and detailed combustion models strategies were identified and applied in order to improve fuel economy and simultaneously reduce emissions.

  9. High-Temperature-Turbine Technology Program: Phase II. Technology test and support studies. Design and development of the liquid-fueled high-temperature combustor for the Turbine Spool Technology Rig

    SciTech Connect

    1981-06-01

    The concept selected by Curtiss-Wright for this DOE sponsored High Temperature Turbine Technology (HTTT) Program utilizes transpiration air-cooling of the turbine subsystem airfoils. With moderate quantities of cooling air, this method of cooling has been demonstrated to be effective in a 2600 to 3000/sup 0/F gas stream. Test results show that transpiration air-cooling also protects turbine components from the aggressive environment produced by the combustion of coal-derived fuels. A new single-stage, high work transpiration air-cooled turbine has been designed and fabricated for evaluation in a rotating test vehicle designated the Turbine Spool Technology Rig (TSTR). The design and development of the annular combustor for the TSTR are described. Some pertinent design characteristics of the combustor are: fuel, Jet A; inlet temperature, 525/sup 0/F; inlet pressure, 7.5 Atm; temperature rise, 2475/sup 0/F; efficiency, 98.5%; exit temperature pattern, 0.25; and exit mass flow, 92.7 pps. The development program was conducted on a 60/sup 0/ sector of the full-round annular combustor. Most design goals were achieved, with the exception of the peak gas exit temperature and local metal temperatures at the rear of the inner liner, both of which were higher than the design values. Subsequent turbine vane cascade testing established the need to reduce both the peak gas temperature (for optimum vane cooling) and the inner liner metal temperature (for combustor durability). Further development of the 60/sup 0/ combustor sector achieved the required temperature reductions and the final configuration was incorporated in the TSTR full-annular burner.

  10. Study of the effects of fuel vortex film cooling on high temperature coating durability

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A report on the effects of fuel vortex film cooling on high temperature coating durability is presented. The program evaluated candidate high temperature oxidation resistant reaction control system engine thrust chamber material. As a result of the evaluation, the current and future programs may be optimized from the materials standpoint. Engine firing data for the evaluation of one material system is generated. The subjects considered are: (1) screening of materials, (2) thrust chamber fabrication, (3) engine testing, and (4) analysis of the data.

  11. Full-length high-temperature severe fuel damage test No. 2. Final safety analysis

    SciTech Connect

    Hesson, G.M.; Lombardo, N.J.; Pilger, J.P.; Rausch, W.N.; King, L.L.; Hurley, D.E.; Parchen, L.J.; Panisko, F.E.

    1993-09-01

    Hazardous conditions associated with performing the Full-Length High- Temperature (FLHT). Severe Fuel Damage Test No. 2 experiment have been analyzed. Major hazards that could cause harm or damage are (1) radioactive fission products, (2) radiation fields, (3) reactivity changes, (4) hydrogen generation, (5) materials at high temperature, (6) steam explosion, and (7) steam pressure pulse. As a result of this analysis, it is concluded that with proper precautions the FLHT- 2 test can be safely conducted.

  12. Coherent anti-Stokes Raman spectroscopy temperature measurements in a hydrogen-fueled supersonic combustor

    NASA Technical Reports Server (NTRS)

    Smith, Michael W.; Jarrett, Olin, Jr.; Antcliff, Richard R.; Northam, G. B.; Cutler, Andrew D.; Taylor, David J.

    1993-01-01

    Coherent anti-Stokes Raman spectroscopy (CARS) thermometry has been used to obtain static temperature cross sections in a three-dimensional supersonic combustor flowfield. Data were obtained in three spanwise planes downstream of a single normal fuel injector which was located downstream of a rearward-facing step. The freestream flow was nominally Mach 2 and was combustion heated to a total temperature of 1440 K (yielding a static temperature of about 800 K in the freestream) to simulate the inflow to a combustor operating at a flight Mach number of about 5.4. Since a broadband probe laser was used an instantaneous temperature sample was obtained with each laser shot at a repetition rate of 10 Hz. Thus root-mean-square (rms) temperatures and temperature probability density functions (pdf's) were obtained in addition to mean temperatures.

  13. Effects of coolant parameters on steady state temperature distribution in phospheric-acid fuel cell electrode

    NASA Technical Reports Server (NTRS)

    Alkasab, K. A.; Abdul-Aziz, A.

    1991-01-01

    The influence of thermophysical properties and flow rate on the steady-state temperature distribution in a phosphoric-acid fuel cell electrode plate was experimentally investigated. An experimental setup that simulates the operating conditions prevailing in a phosphoric-acid fuel cell stack was used. The fuel cell cooling system utilized three types of coolants to remove excess heat generated in the cell electrode and to maintain a reasonably uniform temperature distribution in the electrode plate. The coolants used were water, engine oil, and air. These coolants were circulated at Reynolds number ranging from 1165 to 6165 for water; 3070 to 6864 for air; and 15 to 79 for oil. Experimental results are presented.

  14. Air oxidation behavior of fuel for the High Temperature Engineering Test Reactor (HTTR)

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hironobu; Hayashi, Kimio; Fukuda, Kousaku

    1992-08-01

    The oxidation behavior of the HTTR fuel was studied with respect to the scenario of an air ingress accident which had been assessed in the HTTR safety analysis. The coated fuel particles were heated under a sufficient air flow in the temperature range of 900-1400 C for maximum duration of 600 h (at 1300 C). Failure fractions of the SiC coating layer after the heat treatments remained within the fraction at the fuel production. And the failure behavior of the SiC layer did not depend on such heating conditions as the temperature and the duration in the present experiment. It was confirmed by scanning electron microscopy (SEM), X-ray diffraction, and laser Raman spectroscopy that a thin oxide film was formed on the SiC layer by the heat treatments.

  15. Pu-Zr alloy for high-temperature foil-type fuel

    DOEpatents

    McCuaig, Franklin D.

    1977-01-01

    A nuclear reactor fuel alloy consists essentially of from slightly greater than 7 to about 4 w/o zirconium, balance plutonium, and is characterized in that the alloy is castable and is rollable to thin foils. A preferred embodiment of about 7 w/o zirconium, balance plutonium, has a melting point substantially above the melting point of plutonium, is rollable to foils as thin as 0.0005 inch thick, and is compatible with cladding material when repeatedly cycled to temperatures above 650.degree. C. Neutron reflux densities across a reactor core can be determined with a high-temperature activation-measurement foil which consists of a fuel alloy foil core sandwiched and sealed between two cladding material jackets, the fuel alloy foil core being a 7 w/o zirconium, plutonium foil which is from 0.005 to 0.0005 inch thick.

  16. An evaluation of near-field host rock temperatures for a spent fuel repository

    SciTech Connect

    Altenhofen, M.K.; Lowery, P.S.

    1988-11-01

    A repository heat transfer analysis has been performed by the Pacific Northwest Laboratory (PNL) for the US Department of Energy's Performance Assessment Scientific Support Program. The objective of this study was to evaluate the near-field thermal environmental conditions for a spent fuel repository system. A spent fuel logistics analysis was performed using a waste management system simulation model, WASTES-II, to evaluate the thermal characteristics of spent fuel received at the repository. A repository-scale thermal analysis was performed using a finite difference heat transfer code, TEMPEST, to evaluate the near-field host rock temperature. The calculated temporal and spatial distributions of near-field host rock temperatures provide input to the repository source term model in evaluations of engineered barrier system performance. 9 refs., 10 figs., 2 tabs.

  17. New High-Temperature Membranes Developed for Proton Exchange Membrane Fuel Cells

    NASA Technical Reports Server (NTRS)

    Kinder, James D.

    2004-01-01

    Fuel cells are receiving a considerable amount of attention for potential use in a variety of areas, including the automotive industry, commercial power generation, and personal electronics. Research at the NASA Glenn Research Center has focused on the development of fuel cells for use in aerospace power systems for aircraft, unmanned air vehicles, and space transportation systems. These applications require fuel cells with higher power densities and better durability than what is required for nonaerospace uses. In addition, membrane cost is a concern for any fuel cell application. The most widely used membrane materials for proton exchange membrane (PEM) fuel cells are based on sulfonated perfluorinated polyethers, typically Nafion 117, Flemion, or Aciplex. However, these polymers are costly and do not function well at temperatures above 80 C. At higher temperatures, conventional membrane materials dry out and lose their ability to conduct protons, essential for the operation of the fuel cell. Increasing the operating temperature of PEM fuel cells from 80 to 120 C would significantly increase their power densities and enhance their durability by reducing the susceptibility of the electrode catalysts to carbon monoxide poisoning. Glenn's Polymers Branch has focused on developing new, low-cost membranes that can operate at these higher temperatures. A new series of organically modified siloxane (ORMOSIL) polymers were synthesized for use as membrane materials in a high-temperature PEM fuel cell. These polymers have an organic portion that can allow protons to transport through the polymer film and a cross-linked silica network that gives the polymers dimensional stability. These flexible xerogel polymer films are thermally stable, with decomposition onset as high as 380 C. Two types of proton-conducting ORMOSIL films have been produced: (1) NASA-A, which can coordinate many highly acid inorganic salts that facilitate proton conduction and (2) NASA-B, which has been

  18. Novel Gas Sensors for High-Temperature Fossil Fuel Applications

    SciTech Connect

    Palitha Jayaweera; Francis Tanzella

    2005-03-01

    SRI International (SRI) is developing ceramic-based microsensors to detect exhaust gases such as NO, NO{sub 2}, and CO in advanced combustion and gasification systems under this DOE NETL-sponsored research project. The sensors detect the electrochemical activity of the exhaust gas species on catalytic electrodes attached to a solid state electrolyte and are designed to operate at the high temperatures, elevated pressures, and corrosive environments typical of large power generation exhausts. The sensors can be easily integrated into online monitoring systems for active emission control. The ultimate objective is to develop sensors for multiple gas detection in a single package, along with data acquisition and control software and hardware, so that the information can be used for closed-loop control in novel advanced power generation systems. This report details the Phase I Proof-of-Concept, research activities performed from October 2003 to March 2005. SRI's research work includes synthesis of catalytic materials, sensor design and fabrication, software development, and demonstration of pulse voltammetric analysis of NO, NO{sub 2}, and CO gases on catalytic electrodes.

  19. 40 CFR 86.1229-85 - Dynamometer load determination and fuel temperature profile.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 20 2013-07-01 2013-07-01 false Dynamometer load determination and fuel temperature profile. 86.1229-85 Section 86.1229-85 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES (CONTINUED) Evaporative...

  20. CARCINOGENICITY OF HOUSEHOLD SOLID FUEL COMBUSTION AND OF HIGH-TEMPERATURE FRYING

    EPA Science Inventory

    In October, 2006, 19 scientists from eight countries met at the International Agency for Research on Cancer (IARC) in Lyon, France, to assess the carcinogenicity of household solid fuel combustion (coal and biomass) and of high-temperature frying. These assessments will be publi...

  1. Molten carbonate fuel cells: A high temperature fuel cell on the edge to commercialization

    NASA Astrophysics Data System (ADS)

    Bischoff, Manfred

    The Molten Carbonate Fuel Cell (MCFC) technology has been developed in USA, Japan, Korea and Europe for many years. What has started about 30 years ago as an interesting laboratory object has now matured to a potential alternative to conventional power generation systems. Especially the combined heat and power (CHP) generation is an area, where MCFC power plants can be applied with great advantage, due to the high efficiencies which can be achieved. It was demonstrated by several manufacturers that in the sub-MW region MCFC power plants can reach electrical efficiencies of 47%. By making use of the heat generated by the system, total efficiencies of more than 80% can be achieved. The present paper will discuss some aspects of the development work going on with a focus on the role of the molten carbonate contained in the cells. An outlook will be given for the future prospects of this young technology in a changing energy market.

  2. Effect of calcination temperature on oxidation state of cobalt in calcium cobaltite and relevant performance as intermediate-temperature solid oxide fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Yu, Shancheng; He, Shoucheng; Chen, Han; Guo, Lucun

    2015-04-01

    Calcium cobaltite materials are synthesized by calcining the mixture of CaCO3 and Co3O4 with the Ca: Co ratio of 3:4. The reactivity of CaCO3 with Co3O4 is evaluated by thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermal expansion coefficient (TEC), electrical conductivity and electrochemical performance as intermediate-temperature solid oxide fuel cells (IT-SOFCs) cathode of as-prepared materials are characterized. The experiment results show that simultaneous decomposition of CaCO3 with calcium cobaltite formation occurs at 650-900 °C. The average valence for Co ions of calcium cobaltite increases with temperature in the range of 750-900 °C, involved in the formation of the compounds Ca3Co4O9 and Ca9Co12O28 at 800 and 900 °C, respectively. The performance of calcium cobaltite cathodes applied in IT-SOFCs is significantly effected by the oxidation state of cobalt ions. As a result, Ca9Co12O28 cathode has a lower area specific resistance (e.g. 41.8% lower at 800 °C) and higher peak power density (e.g. 45.0% higher at 800 °C) than the cathode of Ca3Co4O9.

  3. Enhanced performance and stability of high temperature proton exchange membrane fuel cell by incorporating zirconium hydrogen phosphate in catalyst layer

    NASA Astrophysics Data System (ADS)

    Barron, Olivia; Su, Huaneng; Linkov, Vladimir; Pollet, Bruno G.; Pasupathi, Sivakumar

    2015-03-01

    Zirconium hydrogen phosphate (ZHP) together with polytetrafluoroethylene (PTFE) polymer binder is incorporated into the catalyst layers (CLs) of ABPBI (poly(2,5-benzimidazole))-based high temperature polymer electrolyte membrane fuel cell (HT-PEMFCs) to improve its performance and durability. The influence of ZHP content (normalised with respect to dry PTFE) on the CL properties are structurally characterised by scanning electron microscopy (SEM) and mercury intrusion porosimetry. Electrochemical analyses of the resultant membrane electrode assemblies (MEAs) are performed by recording polarisation curves and impedance spectra at 160 °C, ambient pressure and humidity. The result show that a 30 wt.% ZHP/PTFE content in the CL is optimum for improving fuel cell performance, the resultant MEA delivers a peak power of 592 mW cm-2 at a cell voltage of 380 mV. Electrochemical impedance spectra (EIS) indicate that 30% ZHP in the CL can increase the proton conductivity compared to the pristine PTFE-gas diffusion electrode (GDE). A short term stability test (∼500 h) on the 30 wt.% ZHP/PTFE-GDE shows a remarkable high durability with a degradation rate as low as ∼19 μV h-1 at 0.2 A cm-2, while 195 μV h-1 was obtained for the pristine GDE.

  4. Options for treating high-temperature gas-cooled reactor fuel for repository disposal

    SciTech Connect

    Lotts, A.L.; Bond, W.D.; Forsberg, C.W.; Glass, R.W.; Harrington, F.E.; Micheals, G.E.; Notz, K.J.; Wymer, R.G.

    1992-02-01

    This report describes the options that can reasonably be considered for disposal of high-temperature gas-cooled reactor (HTGR) fuel in a repository. The options include whole-block disposal, disposal with removal of graphite (either mechanically or by burning), and reprocessing of spent fuel to separate the fuel and fission products. The report summarizes what is known about the options without extensively projecting or analyzing actual performance of waste forms in a repository. The report also summarizes the processes involved in convert spent HTGR fuel into the various waste forms and projects relative schedules and costs for deployment of the various options. Fort St. Vrain Reactor fuel, which utilizes highly-enriched {sup 235}U (plus thorium) and is contained in a prismatic graphite block geometry, was used as the baseline for evaluation, but the major conclusions would not be significantly different for low- or medium-enriched {sup 235}U (without thorium) or for the German pebble-bed fuel. Future US HTGRs will be based on the Fort St. Vrain (FSV) fuel form. The whole block appears to be a satisfactory waste form for disposal in a repository and may perform better than light-water reactor (LWR) spent fuel. From the standpoint of process cost and schedule (not considering repository cost or value of fuel that might be recycled), the options are ranked as follows in order of increased cost and longer schedule to perform the option: (1) whole block, (2a) physical separation, (2b) chemical separation, and (3) complete chemical processing.

  5. 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

  6. Improved Prediction of the Temperature Feedback in TRISO-Fueled Reactors

    SciTech Connect

    Javier Ortensi; Abderrafi M. Ougouag

    2009-08-01

    The Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated high temperature reactors that use fuel based on Tristructural-Isotropic coated particles. It follows that the correct prediction of the magnitude and time-dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. We present a fuel conduction model for obtaining better estimates of the temperature feedback during moderate and fast transients. The fuel model has been incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes as a single TRISO particle within each calculation cell. The heat generation rate is scaled down from the neutronic solution and a Dirichlet boundary condition is imposed as the bulk graphite temperature from the thermal-hydraulic solution. This simplified approach yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume, but with much less computational effort. An analysis of the hypothetical total control ejection in the PBMR-400 design verifies the performance of the code during fast transients. In addition, the analysis of the earthquake-initiated event in the PBMR-400 design verifies the performance of the code during slow transients. These events clearly depict the improvement in the predictions of the fuel temperature, and consequently, of the power escalations. In addition, a brief study of the potential effects of particle layer de-bonding on the transient behavior of high temperature reactors is included. Although the formation of a gap occurs under special conditions its consequences on the dynamic behavior of the reactor should be analyzed. The presence of a gap in the fuel can cause some unusual reactor behavior during fast transients, but still the reactor shuts down due to the strong feedback effects.

  7. Deep Burn: Development of Transuranic Fuel for High-Temperature Helium-Cooled Reactors- Monthly Highlights October 2010

    SciTech Connect

    Snead, Lance Lewis; Besmann, Theodore M; Collins, Emory D; Bell, Gary L

    2010-11-01

    The DB Program monthly highlights report for September 2010, ORNL/TM-2010/252, was distributed to program participants by email on October 26. This report discusses: (1) Core and Fuel Analysis; (2) Spent Fuel Management; (3) Fuel Cycle Integration of the HTR (high temperature helium-cooled reactor); (4) TRU (transuranic elements) HTR Fuel Qualification; (5) HTR Spent Fuel Recycle - (a) TRU Kernel Development (ORNL), (b) Coating Development (ORNL), (c) Characterization Development and Support, (d) ZrC Properties and Handbook; and (6) HTR Fuel Recycle.

  8. The Challenges Associated with High Burnup and High Temperature for UO2 TRISO-Coated Particle Fuel

    SciTech Connect

    David Petti; John Maki

    2005-02-01

    The fuel service conditions for the DOE Next Generation Nuclear Plant (NGNP) will be challenging. All major fuel related design parameters (burnup, temperature, fast neutron fluence, power density, particle packing fraction) exceed the values that were qualified in the successful German UO2 TRISO-coated particle fuel development program in the 1980s. While TRISO-coated particle fuel has been irradiated at NGNP relevant levels for two or three of the design parameters, no data exist for TRISO-coated particle fuel for all five parameters simultaneously. Of particular concern are the high burnup and high temperatures expected in the NGNP. In this paper, where possible, we evaluate the challenges associated with high burnup and high temperature quantitatively by examining the performance of the fuel in terms of different known failure mechanisms. Potential design solutions to ameliorate the negative effects of high burnup and high temperature are also discussed.

  9. Effect of Dissolved Oxygen on the Filterability of Jet Fuels for Temperatures Between 300 Degrees and 400 Degrees F

    NASA Technical Reports Server (NTRS)

    Mckeown, Anderson B; Hibbard, Robert R

    1955-01-01

    The effect of dissolved oxygen in the filter-clogging characteristics of three JP-4 and two JP-5 fuels was studied at 300 degrees to 400 degrees F in a bench- scale rig, employing filter paper as the filter medium. The residence time of the fuel at the high temperature was approximately 6 seconds. For these conditions, the clogging characteristics of the fuels increased with both increasing temperature and increasing concentration of dissolved oxygen. The amount of insoluble material formed at high temperatures necessary to produce clogging of filters was very small, of the order of 1 milligram per gallon of fuel.

  10. Mechanical and transport properties of NafionRTM for PEM fuel cells; temperature and hydration effects

    NASA Astrophysics Data System (ADS)

    Majsztrik, Paul William

    This work investigates the mechanical and water transport properties of Nafion, a fully fluorinated ion conducting polymer used as a membrane material in proton exchange membrane fuel cells (PEMFCs). Both of these properties are extremely important to the short and long term operation of fuel cells. Nafion is a viscoelastic material, responding to stress in a time-dependant manner. The result is that Nafion flows under stress and responds dynamically to changes in hydration and stress. Stresses applied to the membrane of a PEM fuel cell, both from clamping as well as strain from changing levels of hydration, cause Nafion to flow. This results in thinning in spots and sometimes leads to the development of pinholes or contact problems between membrane and electrode. Temperature and water content strongly affect Nafion's viscoelastic response, of direct importance for operating PEM fuel cells. The viscoelastic response of Nafion was measured over a range of temperature and hydration using viscoelastic creep. A specially designed creep apparatus with environmental controls was used. It was found that the effects of temperature and hydration on Nafion's viscoelastic response are very complicated. Around room temperature, water acts to plasticize Nafion; elastic modulus and resistance to creep decrease with increasing hydration. As temperature increases, water has the opposite effect on mechanical response; hydration acts to stabilize the material. Mechanical property values are reported over a range of temperature and hydration germane to the operation of PEMFCs. Additionally, the data is used to infer molecular level interactions and the effects of temperature and hydration on microstructure. Hydration of Nafion and other PEMFC materials is required for the high proton conductivity needed for fuel cell operation. Uptake of water by Nafion results in volumetric swelling. Water transport through Nafion was directly measured by permeation. Both liquid and vapor phase