40 CFR Table 1 to Subpart Nnnn of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2010 CFR

2010-07-01

... continuous compliance with the operating limit by . . . 1. thermal oxidizer a. the average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4167(a) i. collecting the combustion temperature data according to § 63.4168(c);ii. reducing the...

40 CFR Table 1 to Subpart Nnnn of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2011 CFR

2011-07-01

... continuous compliance with the operating limit by . . . 1. thermal oxidizer a. the average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4167(a) i. collecting the combustion temperature data according to § 63.4168(c);ii. reducing the...

Thermal Imaging of Medical Saw Blades and Guides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dinwiddie, Ralph Barton; Steffner, Thomas E

2007-01-01

Better Than New, LLC., has developed a surface treatment to reduce the friction and wear of orthopedic saw blades and guides. The medical saw blades were thermally imaged while sawing through fresh animal bone and an IR camera was used to measure the blade temperature as it exited the bone. The thermal performance of as-manufactured saw blades was compared to surface-treated blades, and a freshly used blade was used for temperature calibration purposes in order to account for any emissivity changes due to organic transfer layers. Thermal imaging indicates that the treated saw blades cut faster and cooler than untreatedmore » blades. In orthopedic surgery, saw guides are used to perfectly size the bone to accept a prosthesis. However, binding can occur between the blade and guide because of misalignment. This condition increases the saw blade temperature and may result in tissue damage. Both treated ad untreated saw guides were also studied. The treated saw guide operated at a significantly lower temperature than untreated guide. Saw blades and guides that operate at a cooler temperature are expected to reduce the amount of tissue damage (thermal necrosis) and may reduce the number of post-operative complications.« less

Performance of Hg1-xCdxTe infrared focal plane array at elevated temperature

NASA Astrophysics Data System (ADS)

Singh, Anand; Pal, Ravinder

2017-04-01

The simulated optical and electrical performance of the infrared HgCdTe focal plane array (FPA) for elevated operation temperature is reported. The depleted absorber layer is explored for equilibrium mode of operation up to 160 K. A resonant cavity is created to improve photon-matter interaction and hence, reduces the required absorption volume. The volume of the active region of HgCdTe detector is reduced by 70% in this manner. Dark current density is decreased without compromising the quantum efficiency. The effect of the reduced band filling effect leading to higher absorption coefficient and more efficient utilization of incident flux is employed. High quantum efficiency is achieved in a thin compositionally graded n+/ν/π/p HgCdTe photo-diode. This architecture helps to minimize the requirement of charge handling capacity in the CMOS read-out integrated circuit (ROIC) as the operation temperature is increased. Quantum efficiency ˜30% or above is shown to be sufficient for Noise Equivalent Temperature Difference (NETD) less than 20 mK with the reported design.

An Improved X-Band Maser System for Deep Space Network Applications

NASA Astrophysics Data System (ADS)

Britcliffe, M.; Hanson, T.; Fernandez, J.

2000-01-01

An 8450-MHz (X-band) maser system utilizing a commercial Gifford--McMahon (GM) closed-cycle cryocooler (CCR) was designed, fabricated, and demonstrated. The CCR system was used to cool a maser operating at 8450 MHz. The prototype GM CCR system meets or exceeds all Deep Space Network requirements for maser performance. The two-stage GM CCR operates at 4.2 K; for comparison, the DSN's current three-stage cryocooler, which uses a Joule--Thompson cooling stage in addition to GM cooling, operates at 4.5 K. The new CCR withstands heat loads of 1.5 W at 4.2 K as compared to 1 W at 4.5 K for the existing DSN cryocooler used for cooling masers. The measured noise temperature, T_e, of the maser used for these tests is defined at the ambient connection to the antenna feed system. The T_e measured 5.0 K at a CCR temperature of 4.5 K, about 1.5 K higher than the noise temperature of a typical DSN Block II-A X-band traveling-wave maser (TWM). Reducing the temperature of the CCR significantly lowers the maser noise temperature and increases maser gain and bandwidth. The new GM CCR gives future maser systems significant operational advantages, including reduced maintenance time and logistics requirements. The results of a demonstration of this new system are presented. Advantages of using a GM-cooled maser and the effects of the reduced CCR temperature on maser performance are discussed.

Motor torque compensation of an induction electric motor by adjusting a slip command during periods of supposed change in motor temperature

DOEpatents

Kelledes, William L.; St. John, Don K.

1992-01-01

The present invention maintains constant torque in an inverter driven AC induction motor during variations in rotor temperature. It is known that the torque output of a given AC induction motor is dependent upon rotor temperature. At rotor temperatures higher than the nominal operating condition the rotor impedance increases, reducing the rotor current and motor torque. In a similar fashion, the rotor impedance is reduced resulting in increased rotor current and motor torque when the rotor temperature is lower than the nominal operating condition. The present invention monitors the bus current from the DC supply to the inverter and adjusts the slip frequency of the inverter drive to maintain a constant motor torque. This adjustment is based upon whether predetermined conditions implying increased rotor temperature or decreased rotor temperature exist for longer that a predetermined interval of time.

Low-Thermal-Conductivity Pyrochlore Oxide Materials Developed for Advanced Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Zhu, Dong-Ming

2005-01-01

When turbine engines operate at higher temperatures, they consume less fuel, have higher efficiencies, and have lower emissions. The upper-use temperatures of the base materials (superalloys, silicon-based ceramics, etc.) used for the hot-section components of turbine engines are limited by the physical, mechanical, and corrosion characteristics of these materials. Thermal barrier coatings (TBCs) are applied as thin layers on the surfaces of these materials to further increase the operating temperatures. The current state-of-the-art TBC material in commercial use is partially yttria-stabilized zirconia (YSZ), which is applied on engine components by plasma spraying or by electron-beam physical vapor deposition. At temperatures higher than 1000 C, YSZ layers are prone to sintering, which increases thermal conductivity and makes them less effective. The sintered and densified coatings can also reduce thermal stress and strain tolerance, which can reduce the coating s durability significantly. Alternate TBC materials with lower thermal conductivity and better sintering resistance are needed to further increase the operating temperature of turbine engines.

Surface-plasmon distributed-feedback quantum cascade lasers operating pulsed, room temperature

NASA Astrophysics Data System (ADS)

Bousseksou, A.; Chassagneux, Y.; Coudevylle, J. R.; Colombelli, R.; Sirtori, C.; Patriarche, G.; Beaudoin, G.; Sagnes, I.

2009-08-01

We report distributed-feedback surface-plasmon quantum cascade lasers operating at λ ≈7.6μm. The distributed feedback is obtained by the sole patterning of the top metal contact on a surface plasmon waveguide. Single mode operation with more than 30dB side mode suppression ratio is obtained in pulsed mode and at room temperature. A careful experimental study confirms that by varying the grating duty cycle, one can reduce the waveguide losses with respect to standard, unpatterned surface-plasmon devices. This allows one to reduce the laser threshold current of more than a factor of 2 in the 200-300K temperature range. This approach may lead to a fabrication technology for midinfrared distributed-feedback lasers based on a very simple processing.

Electrolyte bi-layering strategy to improve the performance of an intermediate temperature solid oxide fuel cell: A review

NASA Astrophysics Data System (ADS)

Shri Prakash, B.; Pavitra, R.; Senthil Kumar, S.; Aruna, S. T.

2018-03-01

Lowering of operation temperature has become one of the primary goals of solid oxide fuel (SOFC) research as reduced temperature improves the prospects for widespread commercialization of this energy system. Reduced operational temperature also mitigates the issues associated with high temperature SOFCs and paves way not only for the large scale stationary power generation but also makes SOFCs viable for portable and transport applications. However, there are issues with electrolyte and cathode materials at low temperatures, individually as well as in association with other components, which makes the performance of the SOFCs less satisfactory than expected at lowered temperatures. Bi-layering of electrolytes and impregnation of cathodes have emerged as two important strategies to overcome these issues and achieve higher performance at low temperatures. This review article provides the perspective on the strategy of bi-layering of electrolyte to achieve the desired high performance from SOFC at low to intermediate temperatures.

High Temperature Composite Heat Exchangers

NASA Technical Reports Server (NTRS)

Eckel, Andrew J.; Jaskowiak, Martha H.

2002-01-01

High temperature composite heat exchangers are an enabling technology for a number of aeropropulsion applications. They offer the potential for mass reductions of greater than fifty percent over traditional metallics designs and enable vehicle and engine designs. Since they offer the ability to operate at significantly higher operating temperatures, they facilitate operation at reduced coolant flows and make possible temporary uncooled operation in temperature regimes, such as experienced during vehicle reentry, where traditional heat exchangers require coolant flow. This reduction in coolant requirements can translate into enhanced range or system payload. A brief review of the approaches and challengers to exploiting this important technology are presented, along with a status of recent government-funded projects.

Coupling of Transport and Chemical Processes in Catalytic Combustion

NASA Technical Reports Server (NTRS)

Bracco, F. V.; Bruno, C.; Royce, B. S. H.; Santavicca, D. A.; Sinha, N.; Stein, Y.

1983-01-01

Catalytic combustors have demonstrated the ability to operate efficiently over a much wider range of fuel air ratios than are imposed by the flammability limits of conventional combustors. Extensive commercial use however needs the following: (1) the design of a catalyst with low ignition temperature and high temperature stability, (2) reducing fatigue due to thermal stresses during transient operation, and (3) the development of mathematical models that can be used as design optimization tools to isolate promising operating ranges for the numerous operating parameters. The current program of research involves the development of a two dimensional transient catalytic combustion model and the development of a new catalyst with low temperature light-off and high temperature stablity characteristics.

Liquid Nitrogen Temperature Operation of a Switching Power Converter

NASA Technical Reports Server (NTRS)

Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

1995-01-01

The performance of a 42/28 V, 175 W, 50 kHz pulse-width modulated buck dc/dc switching power converter at liquid nitrogen temperature (LNT) is compared with room temperature operation. The power circuit as well as the control circuit of the converter, designed with commercially available components, were operated at LNT and resulted in a slight improvement in converter efficiency. The improvement in power MOSFET operation was offset by deteriorating performance of the output diode rectifier at LNT. Performance of the converter could be further improved at low temperatures by using only power MOSFET's as switches. The use of a resonant topology will further improve the circuit performance by reducing the switching noise and loss.

Development of planar solid oxide fuel cells for power generation applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minh, N.Q.

1996-04-01

Planar solid oxide fuel cells (SOFCs) are presently being developed for a variety of electric power generation application. The planar design offers simple cell geometry, high power density, and multiple fabrication and gas manifolding options. Planar SOFC technology has received much attention recently, and significant progress has been made in this area. Recent effort at AlliedSignal has focused on the development of high-performance, lightweight planar SOFCs, having thin-electrolyte films, that can be operated efficiently at reduced temperatures (< 1000{degrees}C). The advantages of reduced-temperature operation include wider material choice (including use of metallic interconnects), expected longer cell life, reduced thermal stress,more » improved reliability, and reduced fuel cell cost. The key aspect in the development of thin-film SIFCs is to incorporate the thin electrolyte layer into the desired structure of cells in a manner that yields the required characteristics. AlliedSignal has developed a simple and cost-effective method based on tape calendering for the fabrication of thin-electrolyte SOFCs. Thin-electrolyte cells made by tape calendering have shown extraordinary performance, e.g., producing more than 500mW/cm{sup 2} at 700{degrees}C and 800mW/cm{sup 2} at 800{degrees}C with hydrogen as fuel and air is oxidant. thin-electrolyte single cells have been incorporated into a compliant metallic stack structure and operated at reduced and operated at reduced-temperature conditions.« less

Concurrent CO2 Control and O2 Generation for Advanced Life Support

NASA Technical Reports Server (NTRS)

Paul, Heather L.; Duncan, Keith L.; Hagelin-Weaver, Helena E.; Bishop, Sean R.; Wachsman, Eric D.

2007-01-01

The electrochemical reduction of carbon dioxide (CO2) using ceramic oxygen generators (COGs) is well known and widely studied, however, conventional devices using yttria-stabilized zirconia (YSZ) electrolytes operate at temperatures greater than 700 C. Operating at such high temperatures increases system mass compared to lower temperature systems because of increased energy overhead to get the COG up to operating temperature and the need for heavier insulation and/or heat exchangers to reduce the COG oxygen (O2) output temperature for comfortable inhalation. Recently, the University of Florida developed novel ceramic oxygen generators employing a bilayer electrolyte of gadolinia-doped ceria and erbia-stabilized bismuth for NASA's future exploration of Mars. To reduce landed mass and operation expenditures during the mission, in-situ resource utilization was proposed using these COGs to obtain both lifesupporting oxygen and oxidant/propellant fuel, by converting CO2 from the Mars atmosphere. The results showed that oxygen could be reliably produced from CO2 at temperatures as low as 400 C. These results indicate that this technology could be adapted to CO2 removal from a spacesuit and other applications in which CO2 removal was an issue. The strategy proposed for CO2 removal for advanced life support systems employs a catalytic layer combined with a COG so that it is reduced all the way to solid carbon and oxygen. Hence, a three-phased approach was used for the development of a viable low weight COG for CO2 removal. First, to reduce the COG operating temperature a high oxide ion conductivity electrolyte was developed. Second, to promote full CO2 reduction while avoiding the problem of carbon deposition on the COG cathode, novel cathodes and a removable catalytic carbon deposition layer were designed. Third, to improve efficiency, a pre-stage for CO2 absorption was used to concentrate CO2 from the exhalate before sending it to the COG. These subsystems were then integrated into a single CO2 removal system. This paper describes our progress to date on these tasks.

Thermal Vacuum Testing of a Proto-flight Miniature Loop Heat Pipe with Two Evaporators and Two Condensers

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura

2011-01-01

This paper describes thermal vacuum testing of a proto-flight miniature loop heat pipe (MLHP) with two evaporators and two condensers designed for future small systems applications requiring low mass, low power and compactness. Each evaporator contains a wick with an outer diameter of 6.35 mm, and each has its own integral compensation chamber (CC). Miniaturization of the loop components reduces the volume and mass of the thermal system. Multiple evaporators provide flexibility for placement of instruments that need to be maintained at the same temperature, and facilitate heat load sharing among instruments, reducing the auxiliary heater power requirement. A flow regulator is used to regulate heat dissipations between the two condensers, allowing flexible placement of radiators on the spacecraft. A thermoelectric converter (TEC) is attached to each CC for control of the operating temperature and enhancement of start-up success. Tests performed include start-up, power cycle, sink temperature cycle, high power and low power operation, heat load sharing, and operating temperature control. The proto-flight MLHP demonstrated excellent performance in the thermal vacuum test. The loop started successfully and operated stably under various evaporator heat loads and condenser sink temperatures. The TECs were able to maintain the loop operating temperature within b1K of the desired set point temperature at all power levels and all sink temperatures. The un-powered evaporator would automatically share heat from the other powered evaporator. The flow regulator was able to regulate the heat dissipation among the radiators and prevent vapor from flowing into the liquid line.

Ferroelectric infrared detector and method

DOEpatents

Lashley, Jason Charles; Opeil, Cyril P.; Smith, James Lawrence

2010-03-30

An apparatus and method are provided for sensing infrared radiation. The apparatus includes a sensor element that is positioned in a magnetic field during operation to ensure a .lamda. shaped relationship between specific heat and temperature adjacent the Curie temperature of the ferroelectric material comprising the sensor element. The apparatus is operated by inducing a magnetic field on the ferroelectric material to reduce surface charge on the element during its operation.

Altitude Performance of Modified J71 Afterburner with Revised Engine Operating Conditions

NASA Technical Reports Server (NTRS)

Useller, James W.; Russey, Robert E.

1955-01-01

An investigation was conducted in an altitude test chamber at the NACA Lewis laboratory to determine the effect of a revision of the rated engine operating conditions and modifications to the afterburner fue1 system, flameholder, and shell cooling on the augmented performance of the J71-A-2 (x-29) turbo jet engine operating at altitude . The afterburner modifications were made by the manufacturer to improve the endurance at sea-level, high-pressure conditions and to reduce the afterburner shell temperatures. The engine operating conditions of rated rotational speed and turbine-outlet gas temperature were increased. Data were obtained at conditions simulating flight at a Mach number of 0.9 and at altitudes from 40,000 to 60,000 feet. The afterburner modifications caused a reduction in afterburner combustion efficiency. The increase in rated engine speed and turbine-outlet temperature coupled with the afterburner modifications resulted in the over-all thrust of the engine and afterburner being unchanged at a given afterburner equivalence ratio, while the specific fuel consumption was increased slightly. A moderate shift in the range of equivalence ratios over which the afterburner would operate was encountered, but the maximum operable altitude remained unaltered. The afterburner-shell temperatures were also slightly reduced because of the modifications to the afterburner.

Use of a Frequency Divider to Evaluate an SOI NAND Gate Device, Type CHT-7400, for Wide Temperature Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad

2010-01-01

Frequency dividers constitute essential elements in designing phase-locked loop circuits and microwave systems. In addition, they are used in providing required clocking signals to microprocessors and can be utilized as digital counters. In some applications, particularly space missions, electronics are often exposed to extreme temperature conditions. Therefore, it is required that circuits designed for such applications incorporate electronic parts and devices that can tolerate and operate efficiently in harsh temperature environments. While present electronic circuits employ COTS (commercial-off- the-shelf) parts that necessitate and are supported with some form of thermal control systems to maintain adequate temperature for proper operation, it is highly desirable and beneficial if the thermal conditioning elements are eliminated. Amongst these benefits are: simpler system design, reduced weight and size, improved reliability, simpler maintenance, and reduced cost. Devices based on silicon-on-insulator (SOI) technology, which utilizes the addition of an insulation layer in the device structure to reduce leakage currents and to minimize parasitic junctions, are well suited for high temperatures due to reduced internal heating as compared to the conventional silicon devices, and less power consumption. In addition, SOI electronic integrated circuits display good tolerance to radiation by virtue of introducing barriers or lengthening the path for penetrating particles and/or providing a region for trapping incident ionization. The benefits of these parts make them suitable for use in deep space and planetary exploration missions where extreme temperatures and radiation are encountered. Although designed for high temperatures, very little data exist on the operation of SOI devices and circuits at cryogenic temperatures. In this work, the performance of a divide-by-two frequency divider circuit built using COTS SOI logic gates was evaluated over a wide temperature range and thermal cycling to determine suitability for use in space exploration missions and terrestrial fields under extreme temperature conditions.

Fabrication and Performance of Zirconia Electrolysis Cells for Cabon Dioxide Reduction for Mars In Situ Resource Utilization Applications

NASA Technical Reports Server (NTRS)

Minh, N. Q.; Chung, B. W.; Doshi, R.; Lear, G. R.; Montgomery, K.; Ong, E. T.

1999-01-01

Use of the Martian atmosphere (95% CO2) to produce oxygen (for propellant and life support) can significantly lower the required launch mass and dramatically reduce the total cost for Mars missions. Zirconia electrolysis cells are one of the technologies being considered for oxygen generation from carbon dioxide in Mars In Situ Resource Utilization (ISRU) production plants. The attractive features of the zirconia cell for this application include simple operation and lightweight, low volume system. A zirconia electrolysis cell is an all-solid state device, based on oxygen-ion conducting zirconia electrolytes, that electrochemically reduces carbon dioxide to oxygen and carbon monoxide. The cell consists of two porous electrodes (the anode and cathode) separated by a dense zirconia electrolyte. Typical zirconia cells contain an electrolyte layer which is 200 to 400 micrometer thick. The electrical conductivity requirement for the electrolyte necessitates an operating temperature of 9000 to 10000C. Recently, the fabrication of zirconia cells by the tape calendering has been evaluated. This fabrication process provides a simple means of making cells having very thin electrolytes (5 to 30 micrometers). Thin zirconia electrolytes reduce cell ohmic losses, permitting efficient operation at lower temperatures (8000C or below). Thus, tape-calendered cells provides not only the potential of low temperature operation but also the flexibility in operating temperatures. This paper describes the fabrication of zirconia cells by the tape calendering method and discusses the performance results obtained to date.

[Analysis of the effect of detector's operating temperature on SNR in space-based remote sensor].

PubMed

Li, Zhan-feng; Wang, Shu-rong; Huang, Yu

2012-03-01

Limb viewing is a new viewing geometry for space-based atmospheric remote sensing, but the spectral radiance of atmosphere scattering reduces rapidly with limb height. So the signal-noise-ratio (SNR) is a key performance parameter of limb remote sensor. A SNR model varying with detector's temperature is proposed, based on analysis of spectral radiative transfer and noise' source in representative instruments. The SNR at limb height 70 km under space conditions was validated by simulation experiment on limb remote sensing spectrometer prototype. Theoretic analysis and experiment's results indicate congruously that when detector's temperature reduces to some extent, a maximum SNR will be reached. After considering the power consumption, thermal conductivity and other issues, optimal operating temperature of detector can be decided.

Sulfur recirculation for increased electricity production in Waste-to-Energy plants.

PubMed

Andersson, Sven; Blomqvist, Evalena W; Bäfver, Linda; Jones, Frida; Davidsson, Kent; Froitzheim, Jan; Karlsson, Martin; Larsson, Erik; Liske, Jesper

2014-01-01

Sulfur recirculation is a new technology for reducing boiler corrosion and dioxin formation. It was demonstrated in full-scale tests at a Waste to Energy plant in Göteborg (Sweden) during nearly two months of operation. Sulfur was recirculated as sulfuric acid from the flue gas cleaning back to the boiler, thus creating a sulfur loop. The new technology was evaluated by extensive measurement campaigns during operation under normal conditions (reference case) and operation with sulfur recirculation. The chlorine content of both fly ash and boiler ash decreased and the sulfur content increased during the sulfur recirculation tests. The deposit growth and the particle concentration decreased with sulfur recirculation and the dioxin concentration (I-TEQ) of the flue gas was reduced by approximately 25%. Sulfuric acid dew point measurements showed that the sulfuric acid dosage did not lead to elevated SO3 concentrations, which may otherwise induce low temperature corrosion. In the sulfur recirculation corrosion probe exposures, the corrosion rate decreased for all tested materials (16Mo3, Sanicro 28 and Inconel 625) and material temperatures (450 °C and 525 °C) compared to the reference exposure. The corrosion rates were reduced by 60-90%. Sulfur recirculation prevented the formation of transition metal chlorides at the metal/oxide interface, formation of chromate and reduced the presence of zinc in the corrosion products. Furthermore, measured corrosion rates at 525 °C with sulfur recirculation in operation were similar or lower compared to those measured at 450 °C material temperature in reference conditions, which corresponds to normal operation at normal steam temperatures. This implies that sulfur recirculation allows for higher steam data and electricity production without increasing corrosion. Copyright © 2013 The Authors. Published by Elsevier Ltd.. All rights reserved.

40 CFR Table 6 to Subpart Zzzz of... - Continuous Compliance With Emission Limitations and Operating Limitations

Code of Federal Regulations, 2010 CFR

2010-07-01

... stationary RICE >500 HP located at a major source a. Reduce CO emissions and using an oxidation catalyst, and... percent reduction is achieved a; and ii. Collecting the catalyst inlet temperature data according to § 63... rolling averages within the operating limitations for the catalyst inlet temperature; and v. Measuring the...

Progress of MCT Detector Technology at AIM Towards Smaller Pitch and Lower Dark Current

NASA Astrophysics Data System (ADS)

Eich, D.; Schirmacher, W.; Hanna, S.; Mahlein, K. M.; Fries, P.; Figgemeier, H.

2017-09-01

We present our latest results on cooled p-on- n planar mercury cadmium telluride (MCT) photodiode technology. Along with a reduction in dark current for raising the operating temperature ( T op), AIM INFRAROT-MODULE GmbH (AIM) has devoted its development efforts to shrinking the pixel size. Both are essential requirements to meet the market demands for reduced size, weight and power and high-operating temperature applications. Detectors based on the p-on- n technology developed at AIM now span the spectrum from the mid-wavelength infrared (MWIR) to the very long wavelength infrared (VLWIR) with cut-off wavelengths from 5 μm to about 13.5 μm at 80 K. The development of the p-on- n technology for VLWIR as well as for MWIR is mainly implemented in a planar photodetector design with a 20- μm pixel pitch. For the VLWIR, dark currents significantly reduced as compared to `Tennant's Rule 07' are demonstrated for operating temperatures between 30 K and 100 K. This allows for the same dark current performance at a 20 K higher operating temperature than with previous AIM technology. For MWIR detectors with a 20- μm pitch, noise equivalent temperature differences of less than 30 mK are obtained up to 170 K. This technology has been transferred to our small pixel pitch high resolution (XGA) MWIR detector with 1024 × 768 pixels at a 10- μm pitch. Excellent performance at an operating temperature of 160 K is demonstrated.

Enhanced sludge reduction in septic tanks by increasing temperature.

PubMed

Pussayanavin, Tatchai; Koottatep, Thammarat; Eamrat, Rawintra; Polprasert, Chongrak

2015-01-01

Septic tanks in most developing countries are constructed without drainage trenches or leaching fields to treat toilet wastewater and /or grey water. Due to the short hydraulic retention time, effluents of these septic tanks are still highly polluted, and there is usually high accumulation of septic tank sludge or septage containing high levels of organics and pathogens that requires frequent desludging and subsequent treatment. This study aimed to reduce sludge accumulation in septic tanks by increasing temperatures of the septic tank content. An experimental study employing two laboratory-scale septic tanks fed with diluted septage and operating at temperatures of 40 and 30°C was conducted. At steady-state conditions, there were more methanogenic activities occurring in the sludge layer of the septic tank operating at the temperature of 40°C, resulting in less total volatile solids (TVS) or sludge accumulation and more methane (CH4) production than in the unit operating at 30°C. Molecular analysis found more abundance and diversity of methanogenic microorganisms in the septic tank sludge operating at 40°C than at 30°C. The reduced TVS accumulation in the 40°C septic tank would lengthen the period of septage removal, resulting in a cost-saving in desluging and septage treatment. Cost-benefit analysis of increasing temperatures in septic tanks was discussed.

Measuring Seebeck Coefficient

NASA Technical Reports Server (NTRS)

Snyder, G. Jeffrey (Inventor)

2015-01-01

A high temperature Seebeck coefficient measurement apparatus and method with various features to minimize typical sources of errors is described. Common sources of temperature and voltage measurement errors which may impact accurate measurement are identified and reduced. Applying the identified principles, a high temperature Seebeck measurement apparatus and method employing a uniaxial, four-point geometry is described to operate from room temperature up to 1300K. These techniques for non-destructive Seebeck coefficient measurements are simple to operate, and are suitable for bulk samples with a broad range of physical types and shapes.

Prototyping a new, high-temperature SQUID magnetometer system

NASA Astrophysics Data System (ADS)

Grappone, J. Michael; Shaw, John; Biggin, Andrew J.

2017-04-01

High-sensitivity Superconducting Quantum Inference Devices (SQUIDs) and μ-metal shielding have largely solved paleomagnetic noise problems. Combing the two allows successful measurements of previously unusable samples, generally sediments with very weak (<10 pAm2) magnetizations. The improved sensitivity increases the fidelity of magnetic field variation surveys, but surveys continue to be somewhat slow. SQUIDs have historically been expensive to buy and operate, but technological advances now allow them to operate at liquid nitrogen temperatures (77 K), drastically reducing their costs. Step-wise thermal paleomagnetics studies cause large lag times during later steps as a result of heating from and cooling to room temperature for measurements. If the cooling step is removed entirely, however, the lag time drops by at least half. Available magnetometers currently provide either SQUID-level (0.1 - 1 pAm2) sensitivity or continuous heating. Combining a SQUID magnetometer with a high temperature oven is the logical next step to uncover the mysteries of the paleofield. However, the few that currently offer high temperature capabilities with noise levels approaching 10 pAm2 require either spinning or vibrating the sample, necessitating additional handling and potentially causing damage to the sample. Two primary factors have plagued previous developments: noise levels and temperature gradients. Our entire system is shielded from the environment using 4 layers of μ-metal. Our sample oven (designed for 7 mm diameter samples) sits inside a copper pipe and operates at high-frequency AC voltages. High frequency (10 kHz) AC current reduces the skin depth of radio frequency (RF) electromagnetic noise, which allows the 2 mm-thick copper shielding to reduce RF noise by ˜94%, leaving a residual field of ˜1.5 nT at the SQUID's location, 14.9 mm from the oven. A computer-controlled Eurotherm 3216 thermal controller regulates the temperature within ± 0.5 ˚ C. To reach 700 ˚ C, just above the Curie temperature of Hematite, a temperature difference of nearly 900 ˚ C between the sample and the SQUID is required. Since dipole fields decay rapidly with distance (∝ r -3 ), the equipment is designed to handle temperature gradients above 500 ˚ C cm-1 for maximum sensitivity using a passive double-vacuum separation system. All the parts used are commercially available to help reduce the operating costs and increase versatility.

Change in working characteristics of the steam turbine metal with operating time of more than 330000 hours

NASA Astrophysics Data System (ADS)

Gladshteyn, V. I.; Troitskiy, A. I.

2017-01-01

Research of a metal of the stop valve case (SVC) of the K-300-23.5 LMZ turbine (steel grade 15Kh1M1FL), destroyed after operation for 331000 hours, is performed. It's chemical composition and properties are determined as follows: a short-term mechanical tensile stress at 20°C and at elevated temperature, critical temperature, fragility, critical crack opening at elevated temperature, and long-term strength. Furthermore, nature of the microstructure, packing density of carbide particles and their size, and chemical composition of carbide sediment are estimated. A manifestation of metal properties for the main case components by comparison with a forecast of the respective characteristics made for the operating time of 331000 hours is tested. Property-time relationships are built for the forecast using statistical treatment of the test results for the samples cut out from more than 300 parts. Representativeness of the research results is proved: the statistical treatment of their differences are within the range of ±5%. It has been found that, after 150000 hours of operation, only the tensile strength insignificantly depends on the operating time at 20°C, whereas indicators of strength at elevated temperature significantly reduce, depending on the operating time. A brittle-to-ductile transition temperature (BDTT) raises, a critical notch opening changes in a complicated way, a long-term strength reduces. It has been found empirically that the limit of a long-term strength of the SVC metal at 540°C and the operating time of 105 hours is almost 1.6 times less than the required value in the as-delivered state. It is possible to evaluate a service life of the operating valves with the operating time of more than 330000 hours with respect to the long-term strength of the metal taking into account the actual temperature and stress. Guidelines for the control of similar parts are provided.

Wide-Temperature Electronics for Thermal Control of Nanosats

NASA Technical Reports Server (NTRS)

Dickman, John Ellis; Gerber, Scott

2000-01-01

This document represents a presentation which examines the wide and low-temperature electronics required for NanoSatellites. In the past, larger spacecraft used Radioisotope Heating Units (RHU's). The advantage of the use of these electronics is that they could eliminate or reduce the requirement for RHU's, reduce system weight and simplify spacecraft design by eliminating containment/support structures for RHU's. The Glenn Research Center's Wide/Low Temperature Power Electronics Program supports the development of power systems capable of reliable, efficient operation over wide and low temperature ranges. Included charts review the successes and failures of various electronic devices, the IRF541 HEXFET, The NE76118n-Channel GaAS MESFET, the Lithium Carbon Monofluoride Primary Battery, and a COTS DC-DC converter. The preliminary result of wide/low temperature testing of CTS and custom parts and power circuit indicate that through careful selection of components and technologies it is possible to design and build power circuits which operate from room temperature to near 100K.

40 CFR Table 2 to Subpart Ppppp of... - Operating Limits

Code of Federal Regulations, 2011 CFR

2011-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.9324(a) i. Collecting the combustion temperature data according to § 63.9306(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour average combustion temperature...

40 CFR Table 2 to Subpart Ppppp of... - Operating Limits

Code of Federal Regulations, 2014 CFR

2014-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.9324(a) i. Collecting the combustion temperature data according to § 63.9306(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour average combustion temperature...

40 CFR Table 2 to Subpart Ppppp of... - Operating Limits

Code of Federal Regulations, 2010 CFR

2010-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.9324(a) i. Collecting the combustion temperature data according to § 63.9306(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour average combustion temperature...

40 CFR Table 2 to Subpart Ppppp of... - Operating Limits

Code of Federal Regulations, 2013 CFR

2013-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.9324(a) i. Collecting the combustion temperature data according to § 63.9306(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour average combustion temperature...

40 CFR Table 2 to Subpart Ppppp of... - Operating Limits

Code of Federal Regulations, 2012 CFR

2012-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.9324(a) i. Collecting the combustion temperature data according to § 63.9306(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour average combustion temperature...

Simulation of SRAM SEU Sensitivity at Reduced Operating Temperatures

NASA Technical Reports Server (NTRS)

Sanathanamurthy, S.; Ramachandran, V.; Alles, M. L.; Reed, R. A.; Massengill, L. W.; Raman, A.; Turowski, M.; Mantooth, A.; Woods, B.; Barlow, M.;

High temperature operation In1-xAlxSb infrared focal plane

NASA Astrophysics Data System (ADS)

Lyu, Yanqiu; Si, Junjie; Cao, Xiancun; Zhang, Liang; Peng, Zhenyu; Ding, Jiaxin; Yao, Guansheng; Zhang, Xiaolei; Reobrazhenskiy, Valeriy

2016-05-01

A high temperature operation mid-wavelength 128×128 infrared focal plane arrays (FPA) based on low Al component In1-xAlxSb was presented in this work. InAlSb materials were grown on InSb (100) substrates using MBE technology, which was confirmed by XRD and AFM analyses. We have designed and grown two structures with and without barrier. The pixel of the detector had a conventional PIN structure with a size of 50μmx50μm. The device fabrication process consisted of mesa etching, passivation, metallization and flip-chip hybridization with readout integrated circuit (ROIC), epoxy backfill, lap and polish. Diode resistance, imaging, NETD and operability results are presented for a progression of structures that reduce the diode leakage current as the temperature is raised above 80K. These include addition of a thin region of InAlSb to reduce p-contact leakage current, and construction of the whole device from InAlSb to reduce thermal generation in the active region of the detector. An increase in temperature to 110K, whilst maintaining full 80K performance, is achieved. The I-V curves were measured at different temperature. Quantum efficiency, pixel operability, non-uniformity, and the mean NETD values of the FPAs were measured at 110K. This gives the prospect of significant benefits for the cooling systems, including, for example, use of argon in Joule-Thomson coolers or an increase in the life and/or decrease in the cost, power consumption and cool-down time of Stirling engines by several tens of percent.

High operating temperature IR-modules with reduced pitch for SWaP sensitive applications

NASA Astrophysics Data System (ADS)

Breiter, R.; Wendler, J.; Lutz, H.; Rutzinger, S.; Ihle, T.; Ziegler, J.; Rühlich, I.

2011-06-01

Low size, weight and power (SWaP) are the most critical requirements for portable thermal imagers like weapon sights or handheld observations devices. On the other hand due to current asymmetrical conflicts there are high requirements for the e/o performance of these devices providing the ability to distinguish between combatants and non-combatants in adequate ranges. Despite of all the success with uncooled technology, such requirements usually still require cooled detectors. AIM has developed a family of thermal weapon sights called HuntIR and RangIR based on high performance cooled IR-modules which are used e.g. in the infantryman of the future program of the German army (IdZ). The specific capability of these devices is a high ID range >1500m for tank targets being suitable in use as thermal sights for .50 cal rifles like the G82, targeting units for the 40mm AGL or for night observation. While such ranges sound far beyond the operational needs in urban operations, the a.m. specific needs of asymmetric warfare require sometimes even more range performance. High operating temperature (HOT) is introduced in the AIM MCT 640x512/15μm MWIR or LWIR modules for further reduction of cooler power consumption, shorter cooldown times and higher MTTF. As a key component to keep performance while further reducing SWaP AIM is developing a new cooled MCT IR-module with reduced pitch of 12 μm operating at a temperature >120 K. The module will provide full TV format with 640x480 elements sensitive in the MWIR spectral band. The paper will show recent results of AIM IR-modules with high operating temperature and the impact of design regarding the IR-module itself and thermal sights making use of it.

Composite polymer membranes for proton exchange membrane fuel cells operating at elevated temperatures and reduced humidities

NASA Astrophysics Data System (ADS)

Zhang, Tao

Proton Exchange Membrane Fuel Cells (PEMFCs) are the leading candidate in the fuel cell technology due to the high power density, solid electrolyte, and low operational temperature. However, PEMFCs operating in the normal temperature range (60-80°C) face problems including poor carbon monoxide tolerance and heat rejection. The poisoning effect can be significantly relieved by operating the fuel cell at elevated temperature, which also improves the heat rejection and electrochemical kinetics. Low relative humidity (RH) operation is also desirable to simplify the reactant humidification system. However, at elevated temperatures, reduced RH PEMFC performance is seriously impaired due to irreversible water loss from presently employed state-of-the-art polymer membrane, Nafion. This thesis focuses on developing polymer electrolyte membranes with high water retention ability for operation in elevated temperature (110-150°C), reduced humidity (˜50%RH) PEMFCs. One approach is to alter Nafion by adding inorganic particles such as TiO2, SiO2, Zr(HPO 4)2, etc. While the presence of these materials in Nafion has proven beneficial, a reduction or no improvement in the PEMFC performance of Nafion/TiO2 and Nafion/Zr(HPO4)2 membranes is observed with reduced particle sizes or increased particle loadings in Nafion. It is concluded that the PEMFC performance enhancement associated with addition of these inorganic particles was not due to the particle hydrophilicity. Rather, the particle, partially located in the hydrophobic region of the membrane, benefits the cell performance by altering the membrane structure. Water transport properties of some Nafion composite membranes were investigated by NMR methods including pulsed field gradient spin echo diffusion, spin-lattice relaxation, and spectral measurements. Compared to unmodified Nafion, composite membranes materials exhibit longer longitudinal relaxation time constant T1. In addition to the Nafion material, sulfonated styrene-ethylene/butylene-styrene triblock copolymer (sSEBS) was investigated as an alternate membrane candidate. sSEBS was modified through introduction of polymer crosslinks using benzephenone as a photoinitiator and addition of a titania co-phase. A photocrosslinked membrane initially containing 15% benzophenone and 3% titania laminated with a 10 mum Nafion layer was found to produce the best PEMFC performance (120°C, 50%RH).

Cost-Cutting Powdered Lubricant

NASA Technical Reports Server (NTRS)

2005-01-01

Scientists at NASA's Glenn Research Center developed a high-temperature, solid lubricant coating material that is saving the manufacturing industry millions of dollars. The material came out of 3 decades of tribological research, work studying high-temperature friction, lubrication, and the wearing of interacting surfaces that are in relative motion. It was developed as a shaft coating deposited by thermal spraying to protect foil air bearings used in oil-free turbomachinery, like gas turbines, and is meant to be part of a larger project: an oil-free aircraft engine capable of operating at high temperatures with increased reliability, lowered weight, reduced maintenance requirements, and increased power. This advanced coating, PS300, is a self-lubricating bearing material containing chromium oxide, with additions of a low-temperature start up lubricant (silver) and a high-temperature lubricant, making it remarkably stable at high temperatures, and better suited than previously available materials for high-stress conditions. It improves efficiency, lowers friction, reduces emissions, and has been used by NASA in advanced aeropropulsion engines, refrigeration compressors, turbochargers, and hybrid electrical turbogenerators. PS300 is ideal in any application where lowered weight and reduced maintenance are desired, and high-temperature uses and heavy operating speeds are expected. It has notable uses for the Space Agency, but it has even further-reaching potential for the industrial realm.

A low-temperature ZnO nanowire ethanol gas sensor prepared on plastic substrate

NASA Astrophysics Data System (ADS)

Lin, Chih-Hung; Chang, Shoou-Jinn; Hsueh, Ting-Jen

2016-09-01

In this work, a low-temperature ZnO nanowire ethanol gas sensor was prepared on plastic substrate. The operating temperature of the ZnO nanowire ethanol gas sensor was reduced to room temperature using ultraviolet illumination. The experimental results indicate a favorable sensor response at low temperature, with the best response at 60 °C. The results also reveal that the ZnO nanowire ethanol gas sensor can be easily integrated into portable products, whose waste heat can improve sensor response and achieve energy savings, while energy consumption can be further reduced by solar irradiation.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density.

PubMed

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y; Meinhardt, Kerry D; Chang, Hee Jung; Canfield, Nathan L; Sprenkle, Vincent L

2016-02-11

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg(-1), higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

NASA Astrophysics Data System (ADS)

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-02-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium-nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg-1, higher than that of conventional tubular sodium-nickel chloride batteries (280 °C), is obtained for planar sodium-nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium-nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.

Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications

DOE PAGES

Zinkle, S. J.; Boutard, J. L.; Hoelzer, D. T.; ...

2017-06-09

Reduced activation ferritic/martensitic steels are currently the most technologically mature option for the structural material of proposed fusion energy reactors. Advanced next-generation higher performance steels offer the opportunity for improvements in fusion reactor operational lifetime and reliability, superior neutron radiation damage resistance, higher thermodynamic efficiency, and reduced construction costs. The two main strategies for developing improved steels for fusion energy applications are based on (1) an evolutionary pathway using computational thermodynamics modelling and modified thermomechanical treatments (TMT) to produce higher performance reduced activation ferritic/martensitic (RAFM) steels and (2) a higher risk, potentially higher payoff approach based on powder metallurgy techniquesmore » to produce very high strength oxide dispersion strengthened (ODS) steels capable of operation to very high temperatures and with potentially very high resistance to fusion neutron-induced property degradation. The current development status of these next-generation high performance steels is summarized, and research and development challenges for the successful development of these materials are outlined. In conclusion, material properties including temperature-dependent uniaxial yield strengths, tensile elongations, high-temperature thermal creep, Charpy impact ductile to brittle transient temperature (DBTT) and fracture toughness behaviour, and neutron irradiation-induced low-temperature hardening and embrittlement and intermediate-temperature volumetric void swelling (including effects associated with fusion-relevant helium and hydrogen generation) are described for research heats of the new steels.« less

Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zinkle, S. J.; Boutard, J. L.; Hoelzer, D. T.

Reduced activation ferritic/martensitic steels are currently the most technologically mature option for the structural material of proposed fusion energy reactors. Advanced next-generation higher performance steels offer the opportunity for improvements in fusion reactor operational lifetime and reliability, superior neutron radiation damage resistance, higher thermodynamic efficiency, and reduced construction costs. The two main strategies for developing improved steels for fusion energy applications are based on (1) an evolutionary pathway using computational thermodynamics modelling and modified thermomechanical treatments (TMT) to produce higher performance reduced activation ferritic/martensitic (RAFM) steels and (2) a higher risk, potentially higher payoff approach based on powder metallurgy techniquesmore » to produce very high strength oxide dispersion strengthened (ODS) steels capable of operation to very high temperatures and with potentially very high resistance to fusion neutron-induced property degradation. The current development status of these next-generation high performance steels is summarized, and research and development challenges for the successful development of these materials are outlined. In conclusion, material properties including temperature-dependent uniaxial yield strengths, tensile elongations, high-temperature thermal creep, Charpy impact ductile to brittle transient temperature (DBTT) and fracture toughness behaviour, and neutron irradiation-induced low-temperature hardening and embrittlement and intermediate-temperature volumetric void swelling (including effects associated with fusion-relevant helium and hydrogen generation) are described for research heats of the new steels.« less

Development of next generation tempered and ODS reduced activation ferritic/martensitic steels for fusion energy applications

NASA Astrophysics Data System (ADS)

Zinkle, S. J.; Boutard, J. L.; Hoelzer, D. T.; Kimura, A.; Lindau, R.; Odette, G. R.; Rieth, M.; Tan, L.; Tanigawa, H.

2017-09-01

Reduced activation ferritic/martensitic steels are currently the most technologically mature option for the structural material of proposed fusion energy reactors. Advanced next-generation higher performance steels offer the opportunity for improvements in fusion reactor operational lifetime and reliability, superior neutron radiation damage resistance, higher thermodynamic efficiency, and reduced construction costs. The two main strategies for developing improved steels for fusion energy applications are based on (1) an evolutionary pathway using computational thermodynamics modelling and modified thermomechanical treatments (TMT) to produce higher performance reduced activation ferritic/martensitic (RAFM) steels and (2) a higher risk, potentially higher payoff approach based on powder metallurgy techniques to produce very high strength oxide dispersion strengthened (ODS) steels capable of operation to very high temperatures and with potentially very high resistance to fusion neutron-induced property degradation. The current development status of these next-generation high performance steels is summarized, and research and development challenges for the successful development of these materials are outlined. Material properties including temperature-dependent uniaxial yield strengths, tensile elongations, high-temperature thermal creep, Charpy impact ductile to brittle transient temperature (DBTT) and fracture toughness behaviour, and neutron irradiation-induced low-temperature hardening and embrittlement and intermediate-temperature volumetric void swelling (including effects associated with fusion-relevant helium and hydrogen generation) are described for research heats of the new steels.

Joining of Silicon Carbide-Based Ceramics for MEMS-LDI Fuel Injector Applications

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2012-01-01

Deliver the benefits of ceramics in turbine engine applications- increased efficiency, performance, horsepower, range, operating temperature, and payload and reduced cooling and operation and support costs for future engines.

Temperature stable oxide-confined 850-nm VCSELs operating at bit rates up to 25 Gbit/s at 150°C

NASA Astrophysics Data System (ADS)

Ledentsov, N.; Agustin, M.; Kropp, J.-R.; Shchukin, V. A.; Kalosha, V. P.; Chi, K. L.; Khan, Z.; Shi, J. W.; Ledentsov, N. N.

2018-02-01

New applications in industrial, automotive and datacom applications require vertical-cavity surface-emitting lasers (VCSELs) operating at very high ambient temperatures at ultrahigh speed. We discuss issues related to high temperature performance of the VCSELs including temperature response and spectral properties. The influence of the gain-to-cavity wavelength detuning on temperature performance and spectral width of the VCSELs is discussed. Performance of the oxide-confined 850 nm VCSELs with increased temperature stability capable of operating at bit rates up to 25 Gbit/s at heat sink temperature of 150°C and 35Gbit/s at 130°C. Furthermore, opposite to previous studies of VCSELs with large gain-to-cavity detuning, which demonstrated strongly increased spectral width and a strong redistribution of the mode intensities upon current increase. VCSELs demonstrated in this work show good reproducibility of a narrow spectrum in a wide range of currents and temperatures. Such performance strongly improves the transmission distance over multi-mode fiber and can reduce mode partition noise during high speed operation.

Detection near 1-nm with a laminar-flow, water-based condensation particle counter

DOE PAGES

Hering, Susanne V.; Lewis, Gregory S.; Spielman, Steven R.; ...

2016-11-18

Presented is a laminar-flow, water-based condensation particle counter capable of particle detection near 1 nm. This instrument employs a three-stage, laminar-flow growth tube with a “moderator” stage that reduces the temperature and water content of the output flow without reducing the peak supersaturation, and makes feasible operation at the large temperature differences necessary for achieving high supersaturations. The instrument has an aerosol flow of 0.3 L/min, and does not use a filtered sheath flow. It is referred to as a “versatile” water condensation particle counter, or vWCPC, as operating temperatures can be adjusted in accordance with the cut-point desired. Whenmore » operated with wall temperatures of ~2°C, >90°C, and ~22°C for the three stages, respectively, the vWCPC detects particles generated from a heated nichrome wire with a 50% efficiency cut-point near 1.6 nm mobility diameter. At these operating temperatures, it also detects 10–20% of large molecular ions formed from passing filtered ambient air through a bipolar ion source. Decreasing the temperature difference between the first two stages, with the first and second stages operated at 10 and 90°C, respectively, essentially eliminates the response to charger ions, and raises the 50% efficiency cut-point for the nichrome wire particles to 1.9 nm mobility diameter. Here, the time response, as measured by rapid removal of an inlet filter, yields a characteristic time constant of 195 ms.« less

Methods of Controlling the Loop Heat Pipe Operating Temperature

NASA Technical Reports Server (NTRS)

Ku, Jentung

2008-01-01

The operating temperature of a loop heat pipe (LHP) is governed by the saturation temperature of its compensation chamber (CC); the latter is in turn determined by the balance among the heat leak from the evaporator to the CC, the amount of subcooling carried by the liquid returning to the CC, and the amount of heat exchanged between the CC and ambient. The LHP operating temperature can be controlled at a desired set point by actively controlling the CC temperature. The most common method is to cold bias the CC and use electric heater power to maintain the CC set point temperature. The required electric heater power can be large when the condenser sink is very cold. Several methods have been developed to reduce the control heater power, including coupling block, heat exchanger and separate subcooler, variable conductance heat pipe, by-pass valve with pressure regulator, secondary evaporator, and thermoelectric converter. The paper discusses the operating principles, advantages and disadvantages of each method.

Evaluation of a High Temperature SOI Half-Bridge MOSFET Driver, Type CHT-HYPERION

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2010-01-01

Silicon-On-Insulator (SOI) technology utilizes the addition of an insulation layer in its structure to reduce leakage currents and to minimize parasitic junctions. As a result, SOIbased devices exhibit reduced internal heating as compared to the conventional silicon devices, consume less power, and can withstand higher operating temperatures. In addition, SOI electronic integrated circuits display good tolerance to radiation by virtue of introducing barriers or lengthening the path for penetrating particles and/or providing a region for trapping incident ionization. The benefits of these parts make them suitable for use in deep space and planetary exploration missions where extreme temperatures and radiation are encountered. Although designed for high temperatures, very little data exist on the operation of SOI devices and circuits at cryogenic temperatures. In this work, the performance of a commercial-off-the-shelf (COTS) SOI half-bridge driver integrated circuit was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers.

PubMed

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A Giles; Linfield, Edmund H; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-05

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Room-temperature nine-µm-wavelength photodetectors and GHz-frequency heterodyne receivers

NASA Astrophysics Data System (ADS)

Palaferri, Daniele; Todorov, Yanko; Bigioli, Azzurra; Mottaghizadeh, Alireza; Gacemi, Djamal; Calabrese, Allegra; Vasanelli, Angela; Li, Lianhe; Davies, A. Giles; Linfield, Edmund H.; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme; Sirtori, Carlo

2018-04-01

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

Evaluation of a new polymeric stationary phase with reversed-phase properties for high temperature liquid chromatography.

PubMed

Vanhoenacker, Gerd; Dos Santos Pereira, Alberto; Kotsuka, Takashi; Cabooter, Deirdre; Desmet, Gert; Sandra, Pat

2010-05-07

The performance of a polymeric stationary phase with reversed-phase properties (ET-RP1) was evaluated for LC separations at elevated temperature. The most significant observation was that the reduced plate height (h) decreased from 3.4 at 25 degrees C (optimal flow 0.5 mL/min) to 2.4 at 150 degrees C (optimal flow 2.5 mL/min) which is comparable to the efficiency obtained with silica-based reversed-phase columns of 4.6mm ID operated at 0.8 mL/min. The phase showed no deterioration after long use at 150 degrees C within the pH range 1-9. Catalytic activity originating from the stationary phase material, e.g. as experienced on zirconium columns operated at elevated temperature, was absent. The performance of ET-RP1 is illustrated with the analysis of some pharmaceutical samples by LC and LC-MS. Operation at elevated temperature also allows to reduce the amount of organic modifier or to replace acetonitrile and methanol by the biodegradable ethanol. Copyright (c) 2009 Elsevier B.V. All rights reserved.

40 CFR Table 4 to Subpart Kkkk of... - Operating Limits If Using the Emission Rate With Add-on Controls Option or the Control Efficiency...

Code of Federal Regulations, 2010 CFR

2010-07-01

... outlet at or below the temperature limit. 6. Concentrators, including zeolite wheels and rotary carbon.... Collecting the temperature data including zeolite inlet temperature according to § 63.3547(f)ii. Reducing the...

Biological souring and mitigation in oil reservoirs.

PubMed

Gieg, Lisa M; Jack, Tom R; Foght, Julia M

2011-10-01

Souring in oil field systems is most commonly due to the action of sulfate-reducing prokaryotes, a diverse group of anaerobic microorganisms that respire sulfate and produce sulfide (the key souring agent) while oxidizing diverse electron donors. Such biological sulfide production is a detrimental, widespread phenomenon in the petroleum industry, occurring within oil reservoirs or in topside processing facilities, under low- and high-temperature conditions, and in onshore or offshore operations. Sulfate reducers can exist either indigenously in deep subsurface reservoirs or can be "inoculated" into a reservoir system during oil field development (e.g., via drilling operations) or during the oil production phase. In the latter, souring most commonly occurs during water flooding, a secondary recovery strategy wherein water is injected to re-pressurize the reservoir and sweep the oil towards production wells to extend the production life of an oil field. The water source and type of production operation can provide multiple components such as sulfate, labile carbon sources, and sulfate-reducing communities that influence whether oil field souring occurs. Souring can be controlled by biocides, which can non-specifically suppress microbial populations, and by the addition of nitrate (and/or nitrite) that directly impacts the sulfate-reducing population by numerous competitive or inhibitory mechanisms. In this review, we report on the diversity of sulfate reducers associated with oil reservoirs, approaches for determining their presence and effects, the factors that control souring, and the approaches (along with the current understanding of their underlying mechanisms) that may be used to successfully mitigate souring in low-temperature and high-temperature oil field operations.

Electrode materials: a challenge for the exploitation of protonic solid oxide fuel cells

PubMed Central

Fabbri, Emiliana; Pergolesi, Daniele; Traversa, Enrico

2010-01-01

High temperature proton conductor (HTPC) oxides are attracting extensive attention as electrolyte materials alternative to oxygen-ion conductors for use in solid oxide fuel cells (SOFCs) operating at intermediate temperatures (400–700 °C). The need to lower the operating temperature is dictated by cost reduction for SOFC pervasive use. The major stake for the deployment of this technology is the availability of electrodes able to limit polarization losses at the reduced operation temperature. This review aims to comprehensively describe the state-of-the-art anode and cathode materials that have so far been tested with HTPC oxide electrolytes, offering guidelines and possible strategies to speed up the development of protonic SOFCs. PMID:27877342

Operation of SOI P-Channel Field Effect Transistors, CHT-PMOS30, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Electronic systems are required to operate under extreme temperatures in NASA planetary exploration and deep space missions. Electronics on-board spacecraft must also tolerate thermal cycling between extreme temperatures. Thermal management means are usually included in today s spacecraft systems to provide adequate temperature for proper operation of the electronics. These measures, which may include heating elements, heat pipes, radiators, etc., however add to the complexity in the design of the system, increases its cost and weight, and affects its performance and reliability. Electronic parts and circuits capable of withstanding and operating under extreme temperatures would reflect in improvement in system s efficiency, reducing cost, and improving overall reliability. Semiconductor chips based on silicon-on-insulator (SOI) technology are designed mainly for high temperature applications and find extensive use in terrestrial well-logging fields. Their inherent design offers advantages over silicon devices in terms of reduced leakage currents, less power consumption, faster switching speeds, and good radiation tolerance. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. Experimental investigation on the operation of SOI, N-channel field effect transistors under wide temperature range was reported earlier [1]. This work examines the performance of P-channel devices of these SOI transistors. The electronic part investigated in this work comprised of a Cissoid s CHT-PMOS30, high temperature P-channel MOSFET (metal-oxide semiconductor field-effect transistor) device [2]. This high voltage, medium-power transistor is designed for geothermal well logging applications, aerospace and avionics, and automotive industry, and is specified for operation in the temperature range of -55 C to +225 C. Table I shows some specifications of this transistor [2]. The CHT-PMOS30 device was characterized at various temperatures over the range of -190 C to +225 C in terms of its voltage/current characteristic curves. The test temperatures included +22, -50, -100, -150, -175, -190, +50, +100, +150, +175, +200, and +225 C. Limited thermal cycling testing was also performed on the device. These tests consisted of subjecting the transistor to a total of twelve thermal cycles between -190 C and +225 C. A temperature rate of change of 10 C/min and a soak time at the test temperature of 10 minutes were used throughout this work. Post-cycling measurements were also performed at selected temperatures. In addition, re-start capability at extreme temperatures, i.e. power switched on while the device was soaking for a period of 20 minutes at the test temperatures of -190 C and +225 C, was investigated.

Reduced junction temperature and enhanced performance of high power light-emitting diodes using reduced graphene oxide pattern

NASA Astrophysics Data System (ADS)

Han, Nam; Jung, Eunjin; Han, Min; Deul Ryu, Beo; Bok Ko, Kang; Park, Young Jae; Cuong, TranViet; Cho, Jaehee; Kim, Hyunsoo; Hong, Chang-Hee

2015-07-01

Thermal management has become a crucial area for further development of high-power light-emitting didoes (LEDs) due to the high operating current densities that are required and result in additional joule heating. This increased joule heating negatively affects the performance of the LEDs since it greatly decreases both the optical performance and the lifetime. To circumvent this problem, a reduced graphene oxide (rGO) layer can be inserted to act as a heat spreader. In this study, current-voltage and light-output-current measurements are systematically performed at different temperatures from 30 to 190 °C to investigate the effect that the embedded rGO pattern has on the device performance. At a high temperature and high operating current, the junction temperature (Tj) is 23% lower and the external quantum efficiency (EQE) is 24% higher for the rGO embedded LEDs relative to those of conventional LEDs. In addition, the thermal activation energy of the rGO embedded LEDs exhibits a 30% enhancement as a function of the temperature at a bias of  -5 V. This indicates that the rGO pattern plays an essential role in decreasing the junction temperature and results in a favorable performance in terms of the temperature of the high power GaN-based LED junction.

Design, Qualification and Integration Testing of the High-Temperature Resistance Temperature Device for Stirling Power System

NASA Technical Reports Server (NTRS)

Chan, Jack; Hill, Dennis H.; Elisii, Remo; White, Jonathan R.; Lewandowski, Edward J.; Oriti, Salvatore M.

2015-01-01

The Advanced Stirling Radioisotope Generator (ASRG), developed from 2006 to 2013 under the joint sponsorship of the United States Department of Energy (DOE) and National Aeronautics and Space Administration (NASA) to provide a high-efficiency power system for future deep space missions, employed Sunpower Incorporated's Advanced Stirling Convertors (ASCs) with operating temperature up to 840 C. High-temperature operation was made possible by advanced heater head materials developed to increase reliability and thermal-to-mechanical conversion efficiency. During a mission, it is desirable to monitor the Stirling hot-end temperature as a measure of convertor health status and assist in making appropriate operating parameter adjustments to maintain the desired hot-end temperature as the radioisotope fuel decays. To facilitate these operations, a Resistance Temperature Device (RTD) that is capable of high-temperature, continuous long-life service was designed, developed and qualified for use in the ASRG. A thermal bridge was also implemented to reduce the RTD temperature exposure while still allowing an accurate projection of the ASC hot-end temperature. NASA integrated two flight-design RTDs on the ASCs and assembled into the high-fidelity Engineering Unit, the ASRG EU2, at Glenn Research Center (GRC) for extended operation and system characterization. This paper presents the design implementation and qualification of the RTD, and its performance characteristics and calibration in the ASRG EU2 testing.

Temperature and Magnetic Field Dependence of Critical Current Density of YBCO with Varying Flux Pinning Additions (POSTPRINT)

DTIC Science & Technology

2010-03-01

as the cryogenic efficiency of cryocoolers and vacuum components become steadily worse at reducing temperatures 80 K. For many of these applications...it is preferred to increase the operation temperature 50 K where smaller and more ef- ficient cryocoolers can be utilized. To achieve levels required

Research on breakdown characteristics of converter transformer oil-paper insulation under compound electric field in alpine region

NASA Astrophysics Data System (ADS)

Xu, C.; Gao, Z. W.; Lan, S.; Guo, H. X.; Gong, M. C.

2018-01-01

In the paper, existing research and operating experience was summarized. On the basis, the particularity of oil-paper insulation operation condition for converter transformer was combined for studying the influence of temperature on oil-paper insulation field intensity distribution of converter transformers under different AC contents within wide temperature scope (-40°C∼105°C). The law of temperature gradients on space charge accumulation was analyzed. The breakdown or flashover characteristics of typical oil-paper compound insulation structure under the action of DC, AC and AC-DC superposition voltage at different temperatures were explored. The design principles of converter transformer oil-paper insulation structures in alpine region was proposed. The principle was adjusted and optimized properly according to the operation temperature scope and withstood AC-DC proportion. The reliability of transformer operation was improved on the one hand, and the insulating medium can be rationally utilized for reducing the manufacturing cost of the transformer on the other hand.

Advanced intermediate temperature sodium–nickel chloride batteries with ultra-high energy density

PubMed Central

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Y.; Meinhardt, Kerry D.; Chang, Hee Jung; Canfield, Nathan L.; Sprenkle, Vincent L.

2016-01-01

Sodium-metal halide batteries have been considered as one of the more attractive technologies for stationary electrical energy storage, however, they are not used for broader applications despite their relatively well-known redox system. One of the roadblocks hindering market penetration is the high-operating temperature. Here we demonstrate that planar sodium–nickel chloride batteries can be operated at an intermediate temperature of 190 °C with ultra-high energy density. A specific energy density of 350 Wh kg−1, higher than that of conventional tubular sodium–nickel chloride batteries (280 °C), is obtained for planar sodium–nickel chloride batteries operated at 190 °C over a long-term cell test (1,000 cycles), and it attributed to the slower particle growth of the cathode materials at the lower operating temperature. Results reported here demonstrate that planar sodium–nickel chloride batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs. PMID:26864635

Spectral and Concentration Sensitivity of Multijunction Solar Cells at High Temperature: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Friedman, Daniel J.; Steiner, Myles A.; Perl, Emmett E.

2017-06-14

We model the performance of two-junction solar cells at very high temperatures of ~400 degrees C and beyond for applications such as hybrid PV/solar-thermal power production, and identify areas in which the design and performance characteristics behave significantly differently than at more conventional near-room-temperature operating conditions. We show that high-temperature operation reduces the sensitivity of the cell efficiency to spectral content, but increases the sensitivity to concentration, both of which have implications for energy yield in terrestrial PV applications. For other high-temperature applications such as near-sun space missions, our findings indicate that concentration may be a useful tool to enhancemore » cell efficiency.« less

Analytical Micromechanics Modeling Technique Developed for Ceramic Matrix Composites Analysis

NASA Technical Reports Server (NTRS)

Min, James B.

2005-01-01

Ceramic matrix composites (CMCs) promise many advantages for next-generation aerospace propulsion systems. Specifically, carbon-reinforced silicon carbide (C/SiC) CMCs enable higher operational temperatures and provide potential component weight savings by virtue of their high specific strength. These attributes may provide systemwide benefits. Higher operating temperatures lessen or eliminate the need for cooling, thereby reducing both fuel consumption and the complex hardware and plumbing required for heat management. This, in turn, lowers system weight, size, and complexity, while improving efficiency, reliability, and service life, resulting in overall lower operating costs.

Superconducting gamma and fast-neutron spectrometers with high energy resolution

DOEpatents

Friedrich, Stephan; , Niedermayr, Thomas R.; Labov, Simon E.

2008-11-04

Superconducting Gamma-ray and fast-neutron spectrometers with very high energy resolution operated at very low temperatures are provided. The sensor consists of a bulk absorber and a superconducting thermometer weakly coupled to a cold reservoir, and determines the energy of the incident particle from the rise in temperature upon absorption. A superconducting film operated at the transition between its superconducting and its normal state is used as the thermometer, and sensor operation at reservoir temperatures around 0.1 K reduces thermal fluctuations and thus enables very high energy resolution. Depending on the choice of absorber material, the spectrometer can be configured either as a Gamma-spectrometer or as a fast-neutron spectrometer.

Direct methane solid oxide fuel cells and their related applications

NASA Astrophysics Data System (ADS)

Lin, Yuanbo

Solid oxide fuel cells (SOFCs), renowned for their high electrical generation efficiency with low pollutant production, are promising for reducing global energy and environmental concerns. However, there are major barriers for SOFC commercialization. A primary challenge is reducing the capital cost of SOFC power plants to levels that can compete with other generation methods. While the focus of this thesis research was on operation of SOFCs directly with methane fuel, the underlying motivation was to make SOFCs more competitive by reducing their cost. This can be achieved by making SOFCs that reduce the size and complexity of the required "balance of plant". Firstly, direct operation of SOFCs on methane is desirable since it can eliminate the external reformer. However, effective means must be found to suppress deleterious anode coking in methane. In this thesis, the operating conditions under which SOFCs can operate stably and without anode coking were investigated in detail, and the underlying mechanisms of coking and degradation were determined. Furthermore, a novel design utilizing an inert anode barrier layer was developed and shown to substantially improve stability against coking. Secondly, the direct methane SOFCs were investigated for use as electrochemical partial oxidation (EPOx) reactors that can co-generate electricity and synthesis gas (CO+H2) from methane. The results indicated that conventional SOFCs work quite well as methane partial oxidation reactors, producing syngas at relatively high rates. While this approach would not decrease the cost of SOFC power plant, it would improve prospects for commercialization by increasing the value of the power plant, because two products, electricity and syngas, can be sold. Thirdly, SOFCs utilizing thin (La,Sr)(Ga,Mg)O3 electrolytes were demonstrated. This highly conductive material allows lower SOFC operation temperature, leading to the use of lower-cost materials for sealing, interconnection, and balance of plant. Deleterious electrolyte/electrode reactions and electrolyte La loss were avoided during high-temperature co-firing by using thin La-doped ceria barrier layers, allowing very high power densities at moderate operating temperatures. (La,Sr)(Ga,Mg)O3-(La,Sr)(Fe,Co)O3 composite cathodes were investigated and optimal processing parameters that yield low interfacial polarization resistance at intermediate temperature were determined.

Synchronous temperature rate control and apparatus for refrigeration with reduced energy consumption

DOEpatents

Gomes, Alberto Regio; Keres, Stephen L.; Kuehl, Steven J.; Litch, Andrew D.; Richmond, Peter J.; Wu, Guolian

2015-09-22

A refrigerator appliance configuration, and associated methods of operation, for an appliance with a controller, a condenser, at least one evaporator, a compressor, and two refrigeration compartments. The configuration may be equipped with a variable-speed or variable-capacity compressor, variable speed evaporator or compartment fans, a damper, and/or a dual-temperature evaporator with a valve system to control flow of refrigerant through one or more pressure reduction devices. The controller, by operation of the compressor, fans, damper and/or valve system, depending on the appliance configuration, synchronizes alternating cycles of cooling each compartment to a temperature approximately equal to the compartment set point temperature.

Analysis of optimal design of low temperature economizer

NASA Astrophysics Data System (ADS)

Song, J. H.; Wang, S.

2017-11-01

This paper has studied the Off-design characteristic of low temperature economizer system based on thermodynamics analysis. Based on the data from one 1000 MW coal-fired unit, two modes of operation are contrasted and analyzed. One is to fix exhaust gas temperature and the other one is to take into account both of the average temperature difference and the exhaust gas temperature. Meanwhile, the cause of energy saving effect change is explored. Result shows that: in mode 1, the amount of decrease in coal consumption reduces from 1.11 g/kWh (under full load) to 0.54 g/kWh (under half load), and in mode 2, when the load decreases from 90% to 50%, the decrease in coal consumption reduces from 1.29 g/kWh to 0.84 g/kWh. From the result, under high load, the energy saving effect is superior, and under lower work load, energy saving effect declines rapidly when load is reduced. When load changes, the temperature difference of heat transfer, gas flow, the flue gas heat rejection and the waste heat recovery change. The energy saving effect corresponding changes result in that the energy saving effect under high load is superior and more stable. However, rational adjustment to the temperature of outlet gas can alleviate the decline of the energy saving effect under low load. The result provides theoretical analysis data for the optimal design and operation of low temperature economizer system of power plant.

Testing of a Neon Loop Heat Pipe for Large Area Cryocooling

NASA Technical Reports Server (NTRS)

Ku, Jentung; Robinson, Franklin Lee

2014-01-01

Cryocooling of large areas such as optics, detector arrays, and cryogenic propellant tanks is required for future NASA missions. A cryogenic loop heat pipe (CLHP) can provide a closed-loop cooling system for this purpose and has many advantages over other devices in terms of reduced mass, reduced vibration, high reliability, and long life. A neon CLHP was tested extensively in a thermal vacuum chamber using a cryopump as the heat sink to characterize its transient and steady performance and verify its ability to cool large areas or components. Tests conducted included loop cool-down from the ambient temperature, startup, power cycle, heat removal capability, loop capillary limit and recovery from a dry-out, low power operation, and long duration steady state operation. The neon CLHP demonstrated robust operation. The loop could be cooled from the ambient temperature to subcritical temperatures very effectively, and could start successfully by applying power to both the pump and evaporator without any pre-conditioning. It could adapt to changes in the pump power andor evaporator power, and reach a new steady state very quickly. The evaporator could remove heat loads between 0.25W and 4W. When the pump capillary limit was exceeded, the loop could resume its normal function by reducing the pump power. Steady state operations were demonstrated for up to 6 hours. The ability of the neon loop to cool large areas was therefore successfully verified.

Interfacial material for solid oxide fuel cell

DOEpatents

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

1999-01-01

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.

40 CFR Table 1 to Subpart Rrrr of... - Operating Limits if Using the Emission Rate With Add-on Controls Option

Code of Federal Regulations, 2010 CFR

2010-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4966(a) i. collecting the combustion temperature data according to § 63.4967(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion temperature...

40 CFR Table 1 to Subpart Nnnn of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2012 CFR

2012-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4167(a) i. collecting the combustion temperature data according to § 63.4168(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion temperature...

40 CFR Table 1 to Subpart Nnnn of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2014 CFR

2014-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4167(a) i. collecting the combustion temperature data according to § 63.4168(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion temperature...

40 CFR Table 1 to Subpart Nnnn of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2013 CFR

2013-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4167(a) i. collecting the combustion temperature data according to § 63.4168(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion temperature...

40 CFR Table 1 to Subpart Rrrr of... - Operating Limits if Using the Emission Rate With Add-on Controls Option

Code of Federal Regulations, 2011 CFR

2011-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4966(a) i. collecting the combustion temperature data according to § 63.4967(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion temperature...

Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir

NASA Technical Reports Server (NTRS)

Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

2011-01-01

The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly done by cold biasing the reservoir and using electrical heaters to provide the required control power. With this method, the loop operating temperature can be controlled within 0.5K or better. However, because the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if the LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP was carried out to investigate the effects on the LHP operation when the control temperature sensor was placed on the heat source instead of the reservoir. In these tests, the LHP reservoir was cold-biased and was heated by a control heater. Test results show that it was feasible to use the heat source temperature for feedback control of the LHP operation. In particular, when a thermoelectric converter was used as the reservoir control heater, the heat source temperature could be maintained within a tight range using a proportional-integral-derivative or on/off control algorithm. Moreover, because the TEC could provide both heating and cooling to the reservoir, temperature oscillations during fast transients such as loop startup could be eliminated or substantially reduced when compared to using an electrical heater as the control heater.

Identification of high performance and component technology for space electrical power systems for use beyond the year 2000

NASA Technical Reports Server (NTRS)

Maisel, James E.

1988-01-01

Addressed are some of the space electrical power system technologies that should be developed for the U.S. space program to remain competitive in the 21st century. A brief historical overview of some U.S. manned/unmanned spacecraft power systems is discussed to establish the fact that electrical systems are and will continue to become more sophisticated as the power levels appoach those on the ground. Adaptive/Expert power systems that can function in an extraterrestrial environment will be required to take an appropriate action during electrical faults so that the impact is minimal. Manhours can be reduced significantly by relinquishing tedious routine system component maintenance to the adaptive/expert system. By cataloging component signatures over time this system can set a flag for a premature component failure and thus possibly avoid a major fault. High frequency operation is important if the electrical power system mass is to be cut significantly. High power semiconductor or vacuum switching components will be required to meet future power demands. System mass tradeoffs have been investigated in terms of operating at high temperature, efficiency, voltage regulation, and system reliability. High temperature semiconductors will be required. Silicon carbide materials will operate at a temperature around 1000 K and the diamond material up to 1300 K. The driver for elevated temperature operation is that radiator mass is reduced significantly because of inverse temperature to the fourth power.

A thermodynamic approach for selecting operating conditions in the design of reversible solid oxide cell energy systems

NASA Astrophysics Data System (ADS)

Wendel, Christopher H.; Kazempoor, Pejman; Braun, Robert J.

2016-01-01

Reversible solid oxide cell (ReSOC) systems are being increasingly considered for electrical energy storage, although much work remains before they can be realized, including cell materials development and system design optimization. These systems store electricity by generating a synthetic fuel in electrolysis mode and subsequently recover electricity by electrochemically oxidizing the stored fuel in fuel cell mode. System thermal management is improved by promoting methane synthesis internal to the ReSOC stack. Within this strategy, the cell-stack operating conditions are highly impactful on system performance and optimizing these parameters to suit both operating modes is critical to achieving high roundtrip efficiency. Preliminary analysis shows the thermoneutral voltage to be a useful parameter for analyzing ReSOC systems and the focus of this study is to quantitatively examine how it is affected by ReSOC operating conditions. The results reveal that the thermoneutral voltage is generally reduced by increased pressure, and reductions in temperature, fuel utilization, and hydrogen-to-carbon ratio. Based on the thermodynamic analysis, many different combinations of these operating conditions are expected to promote efficient energy storage. Pressurized systems can achieve high efficiency at higher temperature and fuel utilization, while non-pressurized systems may require lower stack temperature and suffer from reduced energy density.

Electronics Demonstrated for Low- Temperature Operation

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammond, Ahmad; Gerber, Scott S.

2000-01-01

The operation of electronic systems at cryogenic temperatures is anticipated for many NASA spacecraft, such as planetary explorers and deep space probes. For example, an unheated interplanetary probe launched to explore the rings of Saturn would experience an average temperature near Saturn of about 183 C. Electronics capable of low-temperature operation in the harsh deep space environment also would help improve circuit performance, increase system efficiency, and reduce payload development and launch costs. An ongoing research and development program on low-temperature electronics at the NASA Glenn Research Center at Lewis Field is focusing on the design of efficient power systems that can survive and exploit the advantages of low-temperature environments. The targeted systems, which are mission driven, include converters, inverters, controls, digital circuits, and special-purpose circuits. Initial development efforts successfully demonstrated the low-temperature operation and cold-restart of several direct-current/direct-current (dc/dc) converters based on different types of circuit design, some with superconducting inductors. The table lists some of these dc/dc converters with their properties, and the photograph shows a high-voltage, high-power dc/dc converter designed for an ion propulsion system for low-temperature operation. The development efforts of advanced electronic systems and the supporting technologies for low-temperature operation are being carried out in-house and through collaboration with other Government agencies, industry, and academia. The Low Temperature Electronics Program supports missions and development programs at NASA s Jet Propulsion Laboratory and Goddard Space Flight Center. The developed technologies will be transferred to commercial end users for applications such as satellite infrared sensors and medical diagnostic equipment.

Research on crude oil storage and transportation based on optimization algorithm

NASA Astrophysics Data System (ADS)

Yuan, Xuhua

2018-04-01

At present, the optimization theory and method have been widely used in the optimization scheduling and optimal operation scheme of complex production systems. Based on C++Builder 6 program development platform, the theoretical research results are implemented by computer. The simulation and intelligent decision system of crude oil storage and transportation inventory scheduling are designed. The system includes modules of project management, data management, graphics processing, simulation of oil depot operation scheme. It can realize the optimization of the scheduling scheme of crude oil storage and transportation system. A multi-point temperature measuring system for monitoring the temperature field of floating roof oil storage tank is developed. The results show that by optimizing operating parameters such as tank operating mode and temperature, the total transportation scheduling costs of the storage and transportation system can be reduced by 9.1%. Therefore, this method can realize safe and stable operation of crude oil storage and transportation system.

Development of Anode-Supported Single Cells and Small Stacks for Intermediate Temperature Sofc at Kepri

NASA Astrophysics Data System (ADS)

Yoo, Y.-S.; Park, J.-W.; Park, J.-K.; Lim, H.-C.; Oh, J.-M.; Bae, J.-M.

Recent results on intermediate temperature-operating solid oxide fuel cells (IT-SOFC) are mainly focused on getting the higher performance of single cell at lower operating temperature, especially using planar type. We have started a project to develop 1 kW-class SOFC system for Residential Power Generation(RPG) application. For a 1 kW-class SOFC stack that can be operated at intermediate temperatures, we have developed anode-supported, planar type SOFC to have advantages for commercialization of SOFCs considering mass production and using cost-effective interconnects such as ferritic stainless steels. At higher temperature, performance of SOFC can be increased due to higher electrochemical activity of electrodes and lower ohmic losses, but the surface of metallic interconnects at cathode side is rapidly oxidized into resistive oxide scale. For efficient operation of SOFC at reduced temperature at, firstly we have developed alternative cathode materials of LSCF instead of LSM to get higher performance of electrodes, and secondly introduced functional-layered structure at anode side. The I-V and AC impedance characteristics of improved single cells and small stacks were evaluated at intermediate temperatures (650°C and 750°C) using hydrogen gas as a fuel.

High temperature ceramic composition for hydrogen retention

DOEpatents

Webb, R.W.

1974-01-01

A ceramic coating for H retention in fuel elements is described. The coating has relatively low thermal neutron cross section, is not readily reduced by H at 1500 deg F, is adherent to the fuel element base metal, and is stable at reactor operating temperatures. (JRD)

Method for control of NOx emission from combustors using fuel dilution

DOEpatents

Schefer, Robert W [Alamo, CA; Keller, Jay O [Oakland, CA

2007-01-16

A method of controlling NOx emission from combustors. The method involves the controlled addition of a diluent such as nitrogen or water vapor, to a base fuel to reduce the flame temperature, thereby reducing NOx production. At the same time, a gas capable of enhancing flame stability and improving low temperature combustion characteristics, such as hydrogen, is added to the fuel mixture. The base fuel can be natural gas for use in industrial and power generation gas turbines and other burners. However, the method described herein is equally applicable to other common fuels such as coal gas, biomass-derived fuels and other common hydrocarbon fuels. The unique combustion characteristics associated with the use of hydrogen, particularly faster flame speed, higher reaction rates, and increased resistance to fluid-mechanical strain, alter the burner combustion characteristics sufficiently to allow operation at the desired lower temperature conditions resulting from diluent addition, without the onset of unstable combustion that can arise at lower combustor operating temperatures.

Rate constant for the H˙ + H2O → ˙OH + H2 reaction at elevated temperatures measured by pulse radiolysis.

PubMed

Muroya, Y; Yamashita, S; Lertnaisat, P; Sanguanmith, S; Meesungnoen, J; Jay-Gerin, J-P; Katsumura, Y

2017-11-22

Maintaining the structural integrity of materials in nuclear power plants is an essential issue associated with safe operation. Hydrogen (H 2 ) addition or injection to coolants is a powerful technique that has been widely applied such that the reducing conditions in the coolant water avoid corrosion and stress corrosion cracking (SCC). Because the radiation-induced reaction of ˙OH + H 2 → H˙ + H 2 O plays a crucial role in these systems, the rate constant has been measured at operation temperatures of the reactors (285-300 °C) by pulse radiolysis, generating sufficient data for analysis. The reverse reaction H˙ + H 2 O → ˙OH + H 2 is negligibly slow at ambient temperature; however, it accelerates considerably quickly at elevated temperatures. Although the reverse reaction reduces the effectiveness of H 2 addition, reliable rate constants have not yet been measured. In this study, the rate constants have been determined in a temperature range of 250-350 °C by pulse radiolysis in an aqueous I - solution.

United States Advanced Ultra-Supercritical Component Test Facility for 760°C Steam Power Plants ComTest Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hack, Horst; Purgert, Robert Michael

Following the successful completion of a 15-year effort to develop and test materials that would allow coal-fired power plants to be operated at advanced ultra-supercritical (A-USC) steam conditions, a United States-based consortium is presently engaged in a project to build an A-USC component test facility (ComTest). A-USC steam cycles have the potential to improve cycle efficiency, reduce fuel costs, and reduce greenhouse gas emissions. Current development and demonstration efforts are focused on enabling the construction of A-USC plants, operating with steam temperatures as high as 1400°F (760°C) and steam pressures up to 5000 psi (35 MPa), which can potentially increasemore » cycle efficiencies to 47% HHV (higher heating value), or approximately 50% LHV (lower heating value), and reduce CO 2 emissions by roughly 25%, compared to today’s U.S. fleet. A-USC technology provides a lower-cost method to reduce CO 2 emissions, compared to CO 2 capture technologies, while retaining a viable coal option for owners of coal generation assets. Among the goals of the ComTest facility are to validate that components made from advanced nickel-based alloys can operate and perform under A-USC conditions, to accelerate the development of a U.S.-based supply chain for the full complement of A-USC components, and to decrease the uncertainty of cost estimates for future A-USC power plants. The configuration of the ComTest facility would include the key A-USC technology components that were identified for expanded operational testing, including a gas-fired superheater, high-temperature steam piping, steam turbine valve, and cycling header component. Membrane walls in the superheater have been designed to operate at the full temperatures expected in a commercial A-USC boiler, but at a lower (intermediate) operating pressure. This superheater has been designed to increase the temperature of the steam supplied by the host utility boiler up to 1400°F (760°C). The steam turbine stop and control valve component has been designed to operate at full A-USC temperatures, and would be tested both in throttling operation and to accumulate accelerated, repetitive stroke cycles. A cycling header component has been designed to confirm the suitability of new high-temperature nickel alloys to cycling operation, expected of future coal-fired power plants. Current test plans would subject these components to A-USC operating conditions for at least 8,000 hours by September 2020. The ComTest project is managed by Energy Industries of Ohio, and technically directed by the Electric Power Research Institute, Inc., with General Electric designing the A-USC components. This consortium is completing the Detailed Engineering phase of the project, with procurement scheduled to begin in late 2017. The effort is primarily funded by the U.S. Department of Energy, through the National Energy Technology Laboratory, along with the Ohio Development Services Agency. This presentation outlines the motivation for the project, explains the project’s structure and schedule, and provides technical details on the design of the ComTest facility.« less

High temperature, high intensity solar array. [for Venus Radar Mapper mission

NASA Technical Reports Server (NTRS)

Smith, B. S.; Brooks, G. R.; Pinkerton, R.

1985-01-01

The solar array for the Venus Radar Mapper mission will operate in the high temperature, high intensity conditions of a low Venus orbit environment. To fulfill the performance requirements in this environment at minimum cost and mass while maximizing power density and packing factor on the panel surface, several features were introduced into the design. These features included the use of optical surface reflectors (OSR's) to reduce the operating temperature; new adhesives for conductive bonding of OSR's to avoid electrostatic discharges; custom-designed large area cells and novel shunt diode circuit and panel power harness configurations.

A novel technique to control high temperature materials degradation in fossil plants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gonzalez-Rodriguez, J.G.; Porcayo-Calderon, J.; Martinez-Villafane, A.

1995-11-01

High temperature corrosion of superheater (SH) and, specially, reheater (RH) is strongly dependent on metal temperature. In this work, a way to continuously monitor the metal temperature of SH or RH, elements developed by the Instituto de Investigaciones Electricas (IIE) is described and the effects of operating parameters on metal temperature are evaluated. Also, the effects the steam-generator design and metal temperature on the corrosion rates have been investigated. In some steam generators, corrosion rates were reduced from 0.7 to 0.2 mm/y by changing the tube material and reducing the metal temperature. Also, the effect of metal temperature on themore » residual life of a 347H tube in a 158MW steam generator is evaluated. It is concluded that metal temperature is the most important parameter in controlling the high-temperature materials behavior in boiler environments.« less

Hydrogen peroxide concentration by pervaporation of a ternary liquid solution in microfluidics.

PubMed

Ziemecka, Iwona; Haut, Benoît; Scheid, Benoit

2015-01-21

Pervaporation in a microfluidic device is performed on liquid ternary solutions of hydrogen peroxide-water-methanol in order to concentrate hydrogen peroxide (H2O2) by removing methanol. The quantitative analysis of the pervaporation of solutions with different initial compositions is performed, varying the operating temperature of the microfluidic device. Experimental results together with a mathematical model of the separation process are used to understand the effect of the operating conditions on the microfluidic device efficiency. The parameters influencing significantly the performance of pervaporation in the microfluidic device are determined and the limitations of the process are discussed. For the analysed system, the operating temperature of the chip has to be below the temperature at which H2O2 decomposes. Therefore, the choice of an adequate reduced operating pressure is required, depending on the expected separation efficiency.

Utilizing Thermal Mass in Refrigerated Display Cases to Reduce Peak Demand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fricke, Brian A; Kuruganti, Teja; Nutaro, James J

The potential to store energy within refrigerated food products presents convenience store and supermarket operators with an opportunity to participate in utility sponsored demand response programs, whereby electricity usage can be shifted or reduced during peak periods. To determine the feasibility of reducing peak demand by shifting the refrigeration load to off-peak times, experimental and analytical analyses were performed. Simulated product, consisting of one-pint containers filled with a 50% ethylene glycol and 50% water solution, were stored in a medium-temperature vertical open refrigerated display case. Product temperature rise as a function of time was determined by turning off the refrigerationmore » to the display case, while product temperature pull-down time was subsequently determined by turning on the refrigeration to the display case. It was found that the thermal mass of the product in a medium-temperature display case was such that during a 2.5 hour period with no refrigeration, the average product temperature increased by 5.5 C. In addition, it took approximately 3.5 hours for the product to recover to its initial temperature after the refrigeration was turned on. Transient heat conduction analyses for one-dimensional objects is in good agreement with the experimental results obtained in this study. From the analysis, it appears that the thermal mass of the stored product in refrigerated display cases is sufficient to allow product temperatures to safely drift for a significant time under reduced refrigeration system operation. Thus, strategies for shifting refrigeration system electrical demand can be developed. The use of an advanced refrigeration system controller that can respond to utility signals can enable demand shifting with minimal impact.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bates, G.J.; Germano, S.

Tests were undertaken with a Renault Express 1.4 litre converted to natural gas operation. The effect of cold starts at cold temperatures and vehicle weight on tail pipe emissions were investigated with petrol and natural gas operation over the FTP75 and the 91/441/EEC drive cycles. The results show that the emissions with natural gas are unaffected by cold temperature, unlike petrol emissions which are several times higher at -15{degree}-C than at 25{degree}-C. A crude simulation, accounting for the actual temperature, shows that the conversion of a significant quantity of light duty vehicles to natural gas operation could reduce the emissionsmore » of CO and HC by more than 90% in Switzerland. 15 refs., 17 figs., 8 tabs.« less

SOI N-Channel Field Effect Transistors, CHT-NMOS80, for Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Almad

2009-01-01

Extreme temperatures, both hot and cold, are anticipated in many of NASA space exploration missions as well as in terrestrial applications. One can seldom find electronics that are capable of operation under both regimes. Even for operation under one (hot or cold) temperature extreme, some thermal controls need to be introduced to provide appropriate ambient temperatures so that spacecraft on-board or field on-site electronic systems work properly. The inclusion of these controls, which comprise of heating elements and radiators along with their associated structures, adds to the complexity in the design of the system, increases cost and weight, and affects overall reliability. Thus, it would be highly desirable and very beneficial to eliminate these thermal measures in order to simplify system's design, improve efficiency, reduce development and launch costs, and improve reliability. These requirements can only be met through the development of electronic parts that are designed for proper and efficient operation under extreme temperature conditions. Silicon-on-insulator (SOI) based devices are finding more use in harsh environments due to the benefits that their inherent design offers in terms of reduced leakage currents, less power consumption, faster switching speeds, good radiation tolerance, and extreme temperature operability. Little is known, however, about their performance at cryogenic temperatures and under wide thermal swings. The objective of this work was to evaluate the performance of a new commercial-off-the-shelf (COTS) SOI parts over an extended temperature range and to determine the effects of thermal cycling on their performance. The results will establish a baseline on the suitability of such devices for use in space exploration missions under extreme temperatures, and will aid mission planners and circuit designers in the proper selection of electronic parts and circuits. The electronic part investigated in this work comprised of a CHT-NMOS80 high temperature N-channel MOSFET (metal-oxide semiconductor field-effect transistor) device that was manufactured by CISSOID. This high voltage, medium-power transistor is fabricated using SOI processes and is designed for extreme wide temperature applications such as geothermal well logging, aerospace and avionics, and automotive industry. It has a high DC current capability and is specified for operation in the temperature range of -55 C to +225 C

Durability and Life of Ceramic Matrix Composites in Combustion Environment

NASA Technical Reports Server (NTRS)

Tewari, Surendra

1997-01-01

It is now generally recognized that the next frontier in the commercial air travel will be achieved by an optimum combination of the concepts being used for the air and space transports. It will depend upon the new engines specifically designed to meet the demanding strength, temperature, environment and economy requirements. The successful development of an advanced propulsion system for a 21st Century High Speed Civil Transport will require key advances in the combustor system. Minimizing nitrous oxide (NO(x)) emission is critical, since the deleterious interaction within the ozone layer would occur at the proposed vehicle cruise level of about 75,000 feet. In order to achieve the low NOx levels an efficient combustor operating at controlled equivalence ratios and high combustion temperatures are required. This requires a combustor, whose one portion will be operating in an oxidizing environment while the other portion will operate in a reducing environment. This rather unusual requirement has introduced considerable challenge to the materials scientists and engineers, the development of material systems capable of long-life at high temperatures (up to 3000 F) in an oxidizing and/or reducing environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Kwan -Soo; Spendelow, Jacob Schatz; Choe, Yoong -Kee

Here, fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100°C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180°C; however, these devices degrade when exposed to water below 140°C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibitmore » stable performance at 80–160°C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.« less

Internal combustion engine controls for reduced exhausts contaminants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, D.R. Jr.

1974-06-04

An electrochemical control system for achieving optimum efficiency in the catalytic conversion of hydrocarbon and carbon monoxide emissions from internal combustion engines is described. The system automatically maintains catalyst temperature at a point for maximum pollutant conversion by adjusting ignition timing and fuel/air ratio during warm-up and subsequent operation. Ignition timing is retarded during engine warm-up to bring the catalytic converter to an efficient operating temperature within a minimum period of time. After the converter reaches a predetermined minimum temperature, the spark is advanced to within its normal operating range. A needle-valve adjustment during warm-up is employed to enrich themore » fuel/air mixture by approximately 10 percent. Following warm-up and attainment of a predetermined catalyst temperature, the needle valve is moved automatically to its normal position (e.g., a fuel/air ratio of 16:1). Although the normal lean mixture causes increased amounts of nitrogen oxide emissions, present NO/sub x/ converters appear capable of handling the increased emissions under normal operating conditions.« less

Design modification for the modular helium reactor for higher temperature operation and reliability studies for nuclear hydrogen production processes

NASA Astrophysics Data System (ADS)

Reza, S. M. Mohsin

Design options have been evaluated for the Modular Helium Reactor (MHR) for higher temperature operation. An alternative configuration for the MHR coolant inlet flow path is developed to reduce the peak vessel temperature (PVT). The coolant inlet path is shifted from the annular path between reactor core barrel and vessel wall through the permanent side reflector (PSR). The number and dimensions of coolant holes are varied to optimize the pressure drop, the inlet velocity, and the percentage of graphite removed from the PSR to create this inlet path. With the removal of ˜10% of the graphite from PSR the PVT is reduced from 541°C to 421°C. A new design for the graphite block core has been evaluated and optimized to reduce the inlet coolant temperature with the aim of further reduction of PVT. The dimensions and number of fuel rods and coolant holes, and the triangular pitch have been changed and optimized. Different packing fractions for the new core design have been used to conserve the number of fuel particles. Thermal properties for the fuel elements are calculated and incorporated into these analyses. The inlet temperature, mass flow and bypass flow are optimized to limit the peak fuel temperature (PFT) within an acceptable range. Using both of these modifications together, the PVT is reduced to ˜350°C while keeping the outlet temperature at 950°C and maintaining the PFT within acceptable limits. The vessel and fuel temperatures during low pressure conduction cooldown and high pressure conduction cooldown transients are found to be well below the design limits. The reliability and availability studies for coupled nuclear hydrogen production processes based on the sulfur iodine thermochemical process and high temperature electrolysis process have been accomplished. The fault tree models for both these processes are developed. Using information obtained on system configuration, component failure probability, component repair time and system operating modes and conditions, the system reliability and availability are assessed. Required redundancies are made to improve system reliability and to optimize the plant design for economic performance. The failure rates and outage factors of both processes are found to be well below the maximum acceptable range.

Global sensitivity analysis of water age and temperature for informing salmonid disease management

NASA Astrophysics Data System (ADS)

Javaheri, Amir; Babbar-Sebens, Meghna; Alexander, Julie; Bartholomew, Jerri; Hallett, Sascha

2018-06-01

Many rivers in the Pacific Northwest region of North America are anthropogenically manipulated via dam operations, leading to system-wide impacts on hydrodynamic conditions and aquatic communities. Understanding how dam operations alter abiotic and biotic variables is important for designing management actions. For example, in the Klamath River, dam outflows could be manipulated to alter water age and temperature to reduce risk of parasite infections in salmon by diluting or altering viability of parasite spores. However, sensitivity of water age and temperature to the riverine conditions such as bathymetry can affect outcomes from dam operations. To examine this issue in detail, we conducted a global sensitivity analysis of water age and temperature to a comprehensive set of hydraulics and meteorological parameters in the Klamath River, California, where management of salmonid disease is a high priority. We applied an analysis technique, which combined Latin-hypercube and one-at-a-time sampling methods, and included simulation runs with the hydrodynamic numerical model of the Lower Klamath. We found that flow rate and bottom roughness were the two most important parameters that influence water age. Water temperature was more sensitive to inflow temperature, air temperature, solar radiation, wind speed, flow rate, and wet bulb temperature respectively. Our results are relevant for managers because they provide a framework for predicting how water within 'high infection risk' sections of the river will respond to dam water (low infection risk) input. Moreover, these data will be useful for prioritizing the use of water age (dilution) versus temperature (spore viability) under certain contexts when considering flow manipulation as a method to reduce risk of infection and disease in Klamath River salmon.

An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

DOE PAGES

Lee, Kwan -Soo; Spendelow, Jacob Schatz; Choe, Yoong -Kee; ...

2016-08-22

Here, fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100°C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180°C; however, these devices degrade when exposed to water below 140°C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibitmore » stable performance at 80–160°C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.« less

An operationally flexible fuel cell based on quaternary ammonium-biphosphate ion pairs

NASA Astrophysics Data System (ADS)

Lee, Kwan-Soo; Spendelow, Jacob S.; Choe, Yoong-Kee; Fujimoto, Cy; Kim, Yu Seung

2016-09-01

Fuel cells are promising devices for clean power generation in a variety of economically and environmentally significant applications. Low-temperature proton exchange membrane (PEM) fuel cells utilizing Nafion require a high level of hydration, which limits the operating temperature to less than 100 ∘C. In contrast, high-temperature PEM fuel cells utilizing phosphoric acid-doped polybenzimidazole can operate effectively up to 180 ∘C however, these devices degrade when exposed to water below 140 ∘C. Here we present a different class of PEM fuel cells based on quaternary ammonium-biphosphate ion pairs that can operate under conditions unattainable with existing fuel cell technologies. These fuel cells exhibit stable performance at 80-160 ∘C with a conductivity decay rate more than three orders of magnitude lower than that of a commercial high-temperature PEM fuel cell. By increasing the operational flexibility, this class of fuel cell can simplify the requirements for heat and water management, and potentially reduce the costs associated with the existing fully functional fuel cell systems.

The Effects of Clock Drift on the Mars Exploration Rovers

NASA Technical Reports Server (NTRS)

Ali, Khaled S.; Vanelli, C. Anthony

2012-01-01

All clocks drift by some amount, and the mission clock on the Mars Exploration Rovers (MER) is no exception. The mission clock on both MER rovers drifted significantly since the rovers were launched, and it is still drifting on the Opportunity rover. The drift rate is temperature dependent. Clock drift causes problems for onboard behaviors and spacecraft operations, such as attitude estimation, driving, operation of the robotic arm, pointing for imaging, power analysis, and telecom analysis. The MER operations team has techniques to deal with some of these problems. There are a few techniques for reducing and eliminating the clock drift, but each has drawbacks. This paper presents an explanation of what is meant by clock drift on the rovers, its relationship to temperature, how we measure it, what problems it causes, how we deal with those problems, and techniques for reducing the drift.

Thermoelectric Power Generation from Lanthanum Strontium Titanium Oxide at Room Temperature through the Addition of Graphene.

PubMed

Lin, Yue; Norman, Colin; Srivastava, Deepanshu; Azough, Feridoon; Wang, Li; Robbins, Mark; Simpson, Kevin; Freer, Robert; Kinloch, Ian A

2015-07-29

The applications of strontium titanium oxide based thermoelectric materials are currently limited by their high operating temperatures of >700 °C. Herein, we show that the thermal operating window of lanthanum strontium titanium oxide (LSTO) can be reduced to room temperature by the addition of a small amount of graphene. This increase in operating performance will enable future applications such as generators in vehicles and other sectors. The LSTO composites incorporated one percent or less of graphene and were sintered under an argon/hydrogen atmosphere. The resultant materials were reduced and possessed a multiphase structure with nanosized grains. The thermal conductivity of the nanocomposites decreased upon the addition of graphene, whereas the electrical conductivity and power factor both increased significantly. These factors, together with a moderate Seebeck coefficient, meant that a high power factor of ∼2500 μWm(-1)K(-2) was reached at room temperature at a loading of 0.6 wt % graphene. The highest thermoelectric figure of merit (ZT) was achieved when 0.6 wt % graphene was added (ZT = 0.42 at room temperature and 0.36 at 750 °C), with >280% enhancement compared to that of pure LSTO. A preliminary 7-couple device was produced using bismuth strontium cobalt oxide/graphene-LSTO pucks. This device had a Seebeck coefficient of ∼1500 μV/K and an open voltage of 600 mV at a mean temperature of 219 °C.

Preliminary Test Results of a Non-Contacting Finger Seal on a Herringbone-Grooved Rotor

NASA Technical Reports Server (NTRS)

Proctor, Margaret P.; Degado, Irebert R.

2008-01-01

Low leakage, non-contacting finger seals have potential to reduce gas turbine engine specific fuel consumption by 2 to 3 percent and to reduce direct operating costs by increasing the time between engine overhauls. A non-contacting finger seal with concentric lift-pads operating adjacent to a test rotor with herringbone grooves was statically tested at 300, 533, and 700 K inlet air temperatures at pressure differentials up to 576 kPa. Leakage flow factors were approximately 70 percent less than state-of-the-art labyrinth seals. Leakage rates are compared to first order predictions. Initial spin tests at 5000 rpm, 300 K inlet air temperature and pressure differentials to 241 kPa produced no measurable wear.

Mechanical attachments for flexible blanket TPS

NASA Astrophysics Data System (ADS)

Newquist, Charles W.; Anderson, David M.; Shorey, Mark W.; Preedy, Kristina S.

1998-01-01

The operability of a flexible blanket thermal protection system for a reusable launch vehicle can be improved by using mechanical attachments instead of adhesive bonding to fasten the thermal protection system to the vehicle structure. Mechanical attachments offer specific benefits by (1) permitting the use of composite or metal structures at or near their maximum temperatures (above the adhesive temperature limit) thereby reducing the required TPS thickness and weight, (2) significantly reducing both the frequency and time for TPS replacement, (3) providing easy access to hatches and the underlying structure, and (4) allowing the attachment of flexible TPS to integral cryotanks, where the TPS/structure interface temperature may fall below the lower temperature of the silicone adhesives.

Performance of High-Speed PWM Control Chips at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard; Overton, Eric

2001-01-01

The operation of power electronic systems at cryogenic temperatures is anticipated in many NASA space missions such as planetary exploration and deep space probes. In addition to surviving the space hostile environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. As part of the NASA Glenn Low Temperature Electronics Program, several commercial high-speed Pulse Width Modulation (PWM) chips have been characterized in terms of their performance as a function of temperature in the range of 25 to -196 C (liquid nitrogen). These chips ranged in their electrical characteristics, modes of control, packaging options, and applications. The experimental procedures along with the experimental data obtained on the investigated chips are presented and discussed.

The Effect of Ethanol Addition to Gasoline on Low- and Intermediate-Temperature Heat Release under Boosted Conditions in Kinetically Controlled Engines

NASA Astrophysics Data System (ADS)

Vuilleumier, David Malcolm

The detailed study of chemical kinetics in engines has become required to further advance engine efficiency while simultaneously lowering engine emissions. This push for higher efficiency engines is not caused by a lack of oil, but by efforts to reduce anthropogenic carbon dioxide emissions, that cause global warming. To operate in more efficient manners while reducing traditional pollutant emissions, modern internal combustion piston engines are forced to operate in regimes in which combustion is no longer fully transport limited, and instead is at least partially governed by chemical kinetics of combusting mixtures. Kinetically-controlled combustion allows the operation of piston engines at high compression ratios, with partially-premixed dilute charges; these operating conditions simultaneously provide high thermodynamic efficiency and low pollutant formation. The investigations presented in this dissertation study the effect of ethanol addition on the low-temperature chemistry of gasoline type fuels in engines. These investigations are carried out both in a simplified, fundamental engine experiment, named Homogeneous Charge Compression Ignition, as well as in more applied engine systems, named Gasoline Compression Ignition engines and Partial Fuel Stratification engines. These experimental investigations, and the accompanying modeling work, show that ethanol is an effective scavenger of radicals at low temperatures, and this inhibits the low temperature pathways of gasoline oxidation. Further, the investigations measure the sensitivity of gasoline auto-ignition to system pressure at conditions that are relevant to modern engines. It is shown that at pressures above 40 bar and temperatures below 850 Kelvin, gasoline begins to exhibit Low-Temperature Heat Release. However, the addition of 20% ethanol raises the pressure requirement to 60 bar, while the temperature requirement remains unchanged. These findings have major implications for a range of modern engines. Low-Temperature Heat Release significantly enhances the auto-ignition process, which limits the conditions under which advanced combustion strategies may operate. As these advanced combustion strategies are required to meet emissions and fuel-economy regulations, the findings of this dissertation may benefit and be incorporated into future engine design toolkits, such as detailed chemical kinetic mechanisms.

Gas absorption/desorption temperature-differential engine

NASA Technical Reports Server (NTRS)

Miller, C. G.

1981-01-01

Continuously operating compressor system converts 90 percent of gas-turbine plant energy to electricity. Conventional plants work in batch mode, operating at 40 percent efficiency. Compressor uses metal hydride matrix on outside of rotating drum to generate working gas, hydrogen. Rolling valve seals allow continuous work. During operation, gas is absorbed, releasing heat, and desorbed with heat gain. System conserves nuclear and fossil fuels, reducing powerplant capital and operating costs.

Analysis of the auger recombination rate in P+N-n-N-N HgCdTe detectors for HOT applications

NASA Astrophysics Data System (ADS)

Schuster, J.; Tennant, W. E.; Bellotti, E.; Wijewarnasuriya, P. S.

2016-05-01

Infrared (IR) photon detectors must be cryogenically cooled to provide the highest possible performance, usually to temperatures at or below ~ 150K. Such low operating temperatures (Top) impose very stringent requirements on cryogenic coolers. As such, there is a constant push in the industry to engineer new detector architectures that operate at higher temperatures, so called higher operating temperature (HOT) detectors. The ultimate goal for HOT detectors is room temperature operation. While this is not currently possibly for photon detectors, significant increases in Top are nonetheless beneficial in terms of reduced size, weight, power and cost (SWAP-C). The most common HgCdTe IR detector architecture is the P+n heterostructure photodiode (where a capital letter indicates a wide band gap relative to the active layer or "AL"). A variant of this architecture, the P+N-n-N-N heterostructure photodiode, should have a near identical photo-response to the P+n heterostructure, but with significantly lower dark diffusion current. The P+N-n-N-N heterostructure utilizes a very low doped AL, surrounded on both sides by wide-gap layers. The low doping in the AL, allows the AL to be fully depleted, which drastically reduces the Auger recombination rate in that layer. Minimizing the Auger recombination rate reduces the intrinsic dark diffusion current, thereby increasing Top. Note when we use the term "recombination rate" for photodiodes, we are actually referring to the net generation and recombination of minority carriers (and corresponding dark currents) by the Auger process. For these benefits to be realized, these devices must be intrinsically limited and well passivated. The focus of this proceeding is on studying the fundamental physics of the intrinsic dark currents in ideal P+N-n-N-N heterostructures, namely Auger recombination. Due to the complexity of these devices, specifically the presence of multiple heterojunctions, numerical device modeling techniques must be utilized to predict and understand the device operation, as analytical models do not exist for heterojunction devices.

Improved high operating temperature MCT MWIR modules

NASA Astrophysics Data System (ADS)

Lutz, H.; Breiter, R.; Figgemeier, H.; Schallenberg, T.; Schirmacher, W.; Wollrab, R.

2014-06-01

High operating temperature (HOT) IR-detectors are a key factor to size, weight and power (SWaP) reduced IR-systems. Such systems are essential to provide infantrymen with low-weight handheld systems with increased battery lifetimes or most compact clip-on weapon sights in combination with high electro-optical performance offered by cooled IR-technology. AIM's MCT standard n-on-p technology with vacancy doping has been optimized over many years resulting in MWIR-detectors with excellent electro-optical performance up to operating temperatures of ~120K. In the last years the effort has been intensified to improve this standard technology by introducing extrinsic doping with Gold as an acceptor. As a consequence the dark current could considerably be suppressed and allows for operation at ~140K with good e/o performance. More detailed investigations showed that limitation for HOT > 140K is explained by consequences from rising dark current rather than from defective pixel level. Recently, several crucial parameters were identified showing great promise for further optimization of HOT-performance. Among those, p-type concentration could successfully be reduced from the mid 1016 / cm3 to the lower 1015/ cm3 range. Since AIM is one of the leading manufacturers of split linear cryocoolers, an increase in operating temperature will directly lead to IR-modules with improved SWaP characteristics by making use of the miniature members of its SX cooler family with single piston and balancer technology. The paper will present recent progress in the development of HOT MWIR-detector arrays at AIM and show electro-optical performance data in comparison to focal plane arrays produced in the standard technology.

Advanced intermediate temperature sodium-nickel chloride batteries with ultra-high energy density

DOE PAGES

Li, Guosheng; Lu, Xiaochuan; Kim, Jin Yong; ...

2016-02-11

Here we demonstrate for the first time that planar Na-NiCl 2 batteries can be operated at an intermediate temperature of 190°C with ultra-high energy density. A specific energy density of 350 Wh/kg, which is 3 times higher than that of conventional tubular Na-NiCl 2 batteries operated at 280°C, was obtained for planar Na-NiCl 2 batteries operated at 190°C over a long-term cell test (1000 cycles). The high energy density and superior cycle stability are attributed to the slower particle growth of the cathode materials (NaCl and Ni) at 190°C. The results reported in this work demonstrate that planar Na-NiCl 2more » batteries operated at an intermediate temperature could greatly benefit this traditional energy storage technology by improving battery energy density, cycle life and reducing material costs.« less

Synthesis of AuPd alloyed nanoparticles via room-temperature electron reduction with argon glow discharge as electron source.

PubMed

Yang, Manman; Wang, Zongyuan; Wang, Wei; Liu, Chang-Jun

2014-01-01

Argon glow discharge has been employed as a cheap, environmentally friendly, and convenient electron source for simultaneous reduction of HAuCl4 and PdCl2 on the anodic aluminum oxide (AAO) substrate. The thermal imaging confirms that the synthesis is operated at room temperature. The reduction is conducted with a short time (30 min) under the pressure of approximately 100 Pa. This room-temperature electron reduction operates in a dry way and requires neither hydrogen nor extra heating nor chemical reducing agent. The analyses using X-ray photoelectron spectroscopy (XPS) confirm all the metallic ions have been reduced. The characterization with X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) shows that AuPd alloyed nanoparticles are formed. There also exist some highly dispersed Au and Pd monometallic particles that cannot be detected by XRD and transmission electron microscopy (TEM) because of their small particle sizes. The observed AuPd alloyed nanoparticles are spherical with an average size of 14 nm. No core-shell structure can be observed. The room-temperature electron reduction can be operated in a larger scale. It is an easy way for the synthesis of AuPd alloyed nanoparticles.

Evaluation of thermograph data for California streams

USGS Publications Warehouse

Limerinos, J.T.

1978-01-01

Statistical analysis of water-temperature data from California streams indicates that, for most purposes, long-term operation of thermographs (automatic water-temperature recording instruments) does not provide a more useful record than either short-term operation of such instruments or periodic measurements. Harmonic analyses were made of thermograph records 5 to 14 years in length from 82 stations. More than 80 percent of the annual variation in water temperature is explained by the harmonic function for 77 of the 82 stations. Harmonic coefficients based on 8 years of thermograph record at 12 stations varied only slightly from coefficients computed using two equally split 4-year records. At five stations where both thermograph and periodic (10 to 23 measurements per year) data were collected concurrently, harmonic coefficients for periodic data were defined nearly as well as those for thermograph data. Results of this analysis indicate that, except where detailed surveillance of water temperatures is required or where there is a chance of temporal change, thermograph operations can be reduced substantially without affecting the usefulness of temperature records.

40 CFR Table 3 to Subpart Qqqq of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2011 CFR

2011-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4767(a) i. Collecting the combustion temperature data according to § 63.4768(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour block average combustion...

40 CFR Table 3 to Subpart Qqqq of... - Operating Limits if Using the Emission Rate With Add-On Controls Option

Code of Federal Regulations, 2010 CFR

2010-07-01

... combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4767(a) i. Collecting the combustion temperature data according to § 63.4768(c);ii. Reducing the data to 3-hour block averages; and iii. Maintaining the 3-hour block average combustion...

40 CFR Table 1 to Subpart Rrrr of... - Operating Limits if Using the Emission Rate With Add-on Controls Option

Code of Federal Regulations, 2013 CFR

2013-07-01

... average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4966(a) i. collecting the combustion temperature data according to § 63.4967(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion...

40 CFR Table 1 to Subpart Rrrr of... - Operating Limits if Using the Emission Rate With Add-on Controls Option

Code of Federal Regulations, 2014 CFR

2014-07-01

... average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4966(a) i. collecting the combustion temperature data according to § 63.4967(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion...

40 CFR Table 1 to Subpart Rrrr of... - Operating Limits if Using the Emission Rate With Add-on Controls Option

Code of Federal Regulations, 2012 CFR

2012-07-01

... average combustion temperature in any 3-hour period must not fall below the combustion temperature limit established according to § 63.4966(a) i. collecting the combustion temperature data according to § 63.4967(c);ii. reducing the data to 3-hour block averages; and iii. maintaining the 3-hour average combustion...

A CMOS smart temperature and humidity sensor with combined readout.

PubMed

Eder, Clemens; Valente, Virgilio; Donaldson, Nick; Demosthenous, Andreas

2014-09-16

A fully-integrated complementary metal-oxide semiconductor (CMOS) sensor for combined temperature and humidity measurements is presented. The main purpose of the device is to monitor the hermeticity of micro-packages for implanted integrated circuits and to ensure their safe operation by monitoring the operating temperature and humidity on-chip. The smart sensor has two modes of operation, in which either the temperature or humidity is converted into a digital code representing a frequency ratio between two oscillators. This ratio is determined by the ratios of the timing capacitances and bias currents in both oscillators. The reference oscillator is biased by a current whose temperature dependency is complementary to the proportional to absolute temperature (PTAT) current. For the temperature measurement, this results in an exceptional normalized sensitivity of about 0.77%/°C at the accepted expense of reduced linearity. The humidity sensor is a capacitor, whose value varies linearly with relative humidity (RH) with a normalized sensitivity of 0.055%/% RH. For comparison, two versions of the humidity sensor with an area of either 0.2 mm2 or 1.2 mm2 were fabricated in a commercial 0.18 μm CMOS process. The on-chip readout electronics operate from a 5 V power supply and consume a current of approximately 85 µA.

Thermal anomalies of the transmitter experiment package on the communications technology satellite

NASA Technical Reports Server (NTRS)

Alexovich, R. E.; Curren, A. N.

1979-01-01

The causes of four temporary thermal-control-system malfunctions that gave rise to unexpected temperature excursions in the 12-gigahertz, 200-watt transmitter experiment package (TEP) on the Communications Technology Satellite were investigated. The TEP consists of a nominal 200-watt output stage tube (OST), a supporting power-processing system (PPS), and a variable-conductance heat-pipe system (VCHPS). The VCHPS, which uses three heat pipes to conduct heat from the body of the OST to a radiator fin, was designed to maintain the TEP at safe operating temperatures at all operating conditions. On four occasions during 1977, all near the spring and fall equinoxes, the OST body temperature and related temperatures displayed sudden, rapid, and unexpected rises above normal levels while the TEP was operating at essentially constant, normal conditions. The temperature excursions were terminated without TEP damage by reducing the radio frequency (RF) output power of the OST. Between the anomalies and since the fourth, the thermal control system has apparently functioned as designed. The results indicate the most probable cause of the temperature anomalies is depriming of the arteries in the variable-conductance heat pipes. A mode was identified in which the TEP, as presently configured, may operate with stable temperatures and with minimum change in performance level.

Recent Enhancements to the National Transonic Facility (Mixed Mode Operations)

NASA Technical Reports Server (NTRS)

Kilgore, W. Allen; Chan, David; Balakrishna, S.; Wahls, Richard A.

2006-01-01

The U.S. National Transonic Facility continues to make enhancements to provide quality data in a safe, efficient and cost effective method for aerodynamic ground testing. Recent enhancements discussed in this paper include the development of a Mixed-mode of operations that combine Air-mode operations with Nitrogen-mode operations. This implementation and operational results of this new Mixed-mode expands the ambient temperature transonic region of testing beyond the Air-mode limitations at a significantly reduced cost over Nitrogen Mode operation.

Establishment of minimum operational parameters for a high-volume static chamber steam pasteurization system (SPS 400-SC) for beef carcasses to support HACCP programs.

PubMed

Retzlaff, Deanna; Phebus, Randall; Kastner, Curtis; Marsden, James

2005-01-01

A static chamber steam pasteurization unit (SPS 400-SC()) was installed in a high-volume commercial beef slaughter facility. The SPS 400-SC consists of a three-phase carcass treatment cycle of water removal, steam pasteurization, and water chilling. Seven chamber temperatures (71.1, 73.9, 76.7, 79.4, 82.2, 85.0, and 87.8 degrees C) were evaluated at the midline area of pre-rigor beef carcasses. For each temperature evaluated, 20 carcass sides were randomly selected and aseptically sampled by tissue excision immediately before and after steam pasteurization to determine total aerobic bacteria, Enterobacteriaceae, generic E. coli, and total coliform populations. The 87.8 and 85.0 degrees C treatment temperatures were highly effective at reducing total aerobic bacterial populations, with log(10) reductions of 1.4 and 1.5 CFU/cm(2), respectively, from pretreatment mean population levels of 1.7 and 1.9 log10 CFU/cm(2). These temperatures also reduced Enterobacteriaceae, total coliforms, and generic E. coli to undetectable levels (<0.4 CFU/cm(2)) on all carcasses sampled. Treatment at 82.2 was marginally effective at reducing bacterial populations, while 71.1, 73.9, 76.7, and 79.4 degrees C treatments were ineffective at reducing microbial populations. In a Hazard Analysis Critical Control Points (HACCP)-based system employing steam pasteurization of carcasses as a critical control point, a critical limit of 85.0 degrees C as a minimum chamber temperature should be established, with a targeted operating temperature of 87.8 degrees C providing optimum antimicrobial activity.

New WC-Cu thermal barriers for fusion applications: High temperature mechanical behaviour

NASA Astrophysics Data System (ADS)

Tejado, E.; Dias, M.; Correia, J. B.; Palacios, T.; Carvalho, P. A.; Alves, E.; Pastor, J. Y.

2018-01-01

The combination of tungsten carbide and copper as a thermal barrier could effectively reduce the thermal mismatch between tungsten and copper alloy, which are proposed as base armour and heat sink, respectively, in the divertor of future fusion reactors. Furthermore, since the optimum operating temperature windows for these divertor materials do not overlap, a compatible thermal barrier interlayer between them is required to guarantee a smooth thermal transition, which in addition may mitigate radiation damage. The aim of this work is to study the thermo-mechanical properties of WC-Cu cermets fabricated by hot pressing. Focus is placed on the temperature effect and composition dependence, as the volume fraction of copper varies from 25 to 50 and 75 vol%. To explore this behaviour, fracture experiments are performed within a temperature range from room temperature to 800 °C under vacuum. In addition, elastic modulus and thermal expansion coefficient are estimated from these tests. Results reveal a strong dependence of the performance on temperature and on the volume fraction of copper and, surprisingly, a slight percent of Cu (25 vol%) can effectively reduce the large difference in thermal expansion between tungsten and copper alloy, which is a critical point for in service applications. The thermal performance of these materials, together with their mechanical properties could indeed reduce the heat transfer from the PFM to the underlying element while supporting the high thermal stresses of the joint. Thus, the presence of these cermets could allow the reactor to operate above the ductile to brittle transition temperature of tungsten, without compromising the underlying materials.

A New Method to Measure Temperature and Burner Pattern Factor Sensing for Active Engine Control

NASA Technical Reports Server (NTRS)

Ng, Daniel

1999-01-01

The determination of the temperatures of extended surfaces which exhibit non-uniform temperature variation is very important for a number of applications including the "Burner Pattern Factor" (BPF) of turbine engines. Exploratory work has shown that use of BPF to control engine functions can result in many benefits, among them reduction in engine weight, reduction in operating cost, increase in engine life, while attaining maximum engine efficiency. Advanced engines are expected to operate at very high temperature to achieve high efficiency. Brief exposure of engine components to higher than design temperatures due to non-uniformity in engine burner pattern can reduce engine life. The engine BPF is a measure of engine temperature uniformity. Attainment of maximum temperature uniformity and high temperatures is key to maximum efficiency and long life. A new approach to determine through the measurement of just one radiation spectrum by a multiwavelength pyrometer is possible. This paper discusses a new temperature sensing approach and its application to determine the BPF.

120 Hz pulse tube cryocooler for fast cooldown to 50 K

NASA Astrophysics Data System (ADS)

Vanapalli, Srinivas; Lewis, Michael; Gan, Zhihua; Radebaugh, Ray

2007-02-01

A pulse tube cryocooler operating at 120Hz with 3.5MPa average pressure achieved a no-load temperature of about 49.9K and a cooldown time to 80K of 5.5min. The net refrigeration power at 80K was 3.35W with an efficiency of 19.7% of Carnot when referred to input pressure-volume (PV or acoustic) power. Such low temperatures have not been previously achieved for operating frequencies above 100Hz. The high frequency operation leads to reduced cryocooler volume for a given refrigeration power, which is important to many applications and can enable development of microcryocoolers for microelectromechanical system applications.

High temperature ion source for an on-line isotope separator

DOEpatents

Mlekodaj, Ronald L.

1979-01-01

A reduced size ion source for on-line use with a cyclotron heavy-ion beam is provided. A sixfold reduction in source volume while operating with similar input power levels results in a 2000.degree. C. operating temperature. A combined target/window normally provides the reaction products for ionization while isolating the ion source plasma from the cyclotron beam line vacuum. A graphite felt catcher stops the recoiling reaction products and releases them into the plasma through diffusion and evaporation. Other target arrangements are also possible. A twenty-four hour lifetime of unattended operation is achieved, and a wider range of elements can be studied than was heretofore possible.

Electronic Components and Systems for Cryogenic Space Applications

NASA Technical Reports Server (NTRS)

Patterson, R. L.; Hammoud, A.; Dickman, J. E.; Gerber, S.; Elbuluk, M. E.; Overton, E.

2001-01-01

Electronic components and systems capable of operation at cryogenic temperatures are anticipated in many future NASA space missions such as deep space probes and planetary surface exploration. For example, an unheated interplanetary probe launched to explore the rings of Saturn would reach an average temperature near Saturn of about - 183 C. In addition to surviving the deep space harsh environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing payload development and launch costs. Terrestrial applications where components and systems must operate in low temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation system, and arctic exploration. An on-going research and development program at the NASA Glenn Research Center focuses on the development of reliable electronic devices and efficient power systems capable of surviving in low temperature environments. An overview of the program will be presented in this paper. A description of the low temperature test facilities along with selected data obtained from in-house component testing will also be discussed. Ongoing research activities that are being performed in collaboration with various organizations will also be presented.

The cataphoretic emitter effect exhibited in high intensity discharge lamp electrodes

NASA Astrophysics Data System (ADS)

Mentel, Juergen

2018-01-01

A mono-layer of atoms, electropositive with respect to the substrate atoms, forms a dipole layer, reducing its work function. Such a layer is generated by diffusion of emitter material from the interior of the substrate, by vapour deposition or by deposition of emitter material onto arc electrodes by cataphoresis. This cataphoretic emitter effect is investigated within metal halide lamps with transparent YAG ceramic burners, and within model lamps. Within the YAG lamps, arcs are operated with switched-dc current between rod shaped tungsten electrodes in high pressure Hg vapour seeded with metal iodides. Within the model lamps, dc arcs are operated between rod-shaped tungsten electrodes—one doped—in atmospheric pressure Ar. Electrode temperatures are determined by 1λ -pyrometry, combined with simulation of the electrode heat balance. Plasma temperatures, atom and ion densities of emitter material are determined by emission and absorption spectroscopy. Phase resolved measurements in YAG lamps seeded with CeI3, CsI, DyI3, TmI3 and LaI3 show, within the cathodic half period, a reduction of the electrode temperature and an enhanced metal ion density in front of the electrode, and an opposite behavior after phase reversal. With increasing operating frequency, the state of the cathode overlaps onto the anodic phase—except for Cs, being low in adsorption energy. Generally, the phase averaged electrode tip temperature is reduced by seeding a lamp with emitter material; its height depends on admixtures. Measurements at tungsten electrodes doped with ThO2, La2O3 and Ce2O3 within the model lamp show that evaporated emitter material is redeposited by an emitter ion current onto the electrode surface. It reduces the work function of tungsten cathodes above the evaporation temperature of the emitter material, too; and also of cold anodes, indicating a field reversal in front of them. The formation of an emitter spot at low cathode temperature and high emitter material density is traced back to a locally reduced work function generated by a locally enhanced emitter ion current density.

Use of thermal cycling to reduce adhesion of OTS coated coated MEMS cantilevers

NASA Astrophysics Data System (ADS)

Ali, Shaikh M.; Phinney, Leslie M.

2003-01-01

°Microelectromechanical systems (MEMS) have enormous potential to contribute in diverse fields such as automotive, health care, aerospace, consumer products, and biotechnology, but successful commercial applications of MEMS are still small in number. Reliability of MEMS is a major impediment to the commercialization of laboratory prototypes. Due to the multitude of MEMS applications and the numerous processing and packaging steps, MEMS are exposed to a variety of environmental conditions, making the prediction of operational reliability difficult. In this paper, we investigate the effects of operating temperature on the in-use adhesive failure of electrostatically actuated MEMS microcantilevers coated with octadecyltrichlorosilane (OTS) films. The cantilevers are subjected to repeated temperature cycles and electrostatically actuated at temperatures between 25°C and 300°C in ambient air. The experimental results indicate that temperature cycling of the OTS coated cantilevers in air reduces the sticking probability of the microcantilevers. The sticking probability of OTS coated cantilevers was highest during heating, which decreased during cooling, and was lowest during reheating. Modifications to the OTS release method to increase its yield are also discussed.

Welding Metallurgy of Nickel-Based Superalloys for Power Plant Construction

NASA Astrophysics Data System (ADS)

Tung, David C.

Increasing the steam temperature and pressure in coal-fired power plants is a perpetual goal driven by the pursuit of increasing thermal cycle efficiency and reducing fuel consumption and emissions. The next target steam operating conditions, which are 760°C (1400°F) and 35 MPa (5000 psi) are known as Advanced Ultra Supercritical (AUSC), and can reduce CO2 emissions up to 13% but this cannot be achieved with traditional power plant construction materials. The use of precipitation-strengthened Nickel-based alloys (superalloys) is required for components which will experience the highest operating temperatures. The leading candidate superalloys for power plant construction are alloys 740H, 282, and 617. Superalloys have excellent elevated temperature properties due to careful microstructural design which is achieved through very specific heat treatments, often requiring solution annealing or homogenization at temperatures of 1100 °C or higher. A series of postweld heat treatments was investigated and it was found that homogenization steps before aging had no noticeable effect on weld metal microhardness, however; there were clear improvements in weld metal homogeneity. The full abstract can be viewed in the document itself.

Development of a low-pressure materials pre-treatment process for improved energy efficiency

NASA Astrophysics Data System (ADS)

Lee, Kwanghee; You, Byung Don

2017-09-01

Low pressure materials pre-treatment process has been developed as an alternative to the existing high-temperature sludge drying, limestone calcination, and limonite dehydroxylation. Using the thermodynamic equilibrium relationship between temperature and pressure represented by the Clausius-Clapeyron equation, the operational temperature of these reactions could be lowered at reduced pressure for increased energy efficiency. For industrial sludge drying, the evaporation rate was controlled by interfacial kinetics showing a constant rate with time and significant acceleration in the reaction could be observed with reduced pressure. At this modified reaction rate under low pressure, the rate was also partially controlled by mass transfer. Temperature of limestone calcination was lowered, but the reaction was limited at the calculated equilibrium temperature of the Clausius-Clapeyron equation and slightly higher temperatures were required. The energy consumption during limestone calcination and limonite dehydroxylation were evaluated, where lower processing pressures could enhance the energy efficiency for limestone calcination, but limonite dehydroxylation could not achieve energy-savings due to the greater power consumption of the vacuum pump under lower pressure and reduced temperatures.

Thermal Vacuum Testing of a Helium Loop Heat Pipe for Large Area Cryocooling

NASA Technical Reports Server (NTRS)

Ku, Jentung; Robinson, Franklin

2016-01-01

Future NASA space telescopes and exploration missions require cryocooling of large areas such as optics, detector arrays, and cryogenic propellant tanks. One device that can potentially be used to provide closed-loop cryocooling is the cryogenic loop heat pipe (CLHP). A CLHP has many advantages over other devices in terms of reduced mass, reduced vibration, high reliability, and long life. A helium CLHP has been tested extensively in a thermal vacuum chamber using a cryocooler as the heat sink to characterize its transient and steady performance and to verify its ability to cool large areas or components in the 3 degrees Kelvin temperature range. The helium CLHP thermal performance test included cool-down from the ambient temperature, startup, capillary limit, heat removal capability, rapid power changes, and long duration steady state operation. The helium CLHP demonstrated robust operation under steady state and transient conditions. The loop could be cooled from the ambient temperature to subcritical temperatures very effectively, and could start successfully by simply applying power to both the capillary pump and the evaporator plate without pre-conditioning. It could adapt to a rapid heat load change and quickly reach a new steady state. Heat removal between 10 megawatts and 140 megawatts was demonstrated, yielding a power turn down ratio of 14. When the CLHP capillary limit was exceeded, the loop could resume its normal function by reducing the power to the capillary pump. Steady state operations up to 17 hours at several heat loads were demonstrated. The ability of the helium CLHP to cool large areas was therefore successfully verified.

Solar Power for Near Sun, High-Temperature Missions

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.

2008-01-01

Existing solar cells lose performance at the high temperatures encountered in Mercury orbit and inward toward the sun. For future missions designed to probe environments close to the sun, it is desirable to develop array technologies for high temperature and high light intensity. Approaches to solar array design for near-sun missions include modifying the terms governing temperature of the cell and the efficiency at elevated temperature, or use of techniques to reduce the incident solar energy to limit operating temperature. An additional problem is found in missions that involve a range of intensities, such as the Solar Probe + mission, which ranges from a starting distance of 1 AU from the sun to a minimum distance of 9.5 solar radii, or 0.044 AU. During the mission, the solar intensity ranges from one to about 500 times AM0. This requires a power system to operate over nearly three orders of magnitude of incident intensity.

Synchronous temperature rate control for refrigeration with reduced energy consumption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomes, Alberto Regio; Keres, Stephen L.; Kuehl, Steven J.

Methods of operation for refrigerator appliance configurations with a controller, a condenser, at least one evaporator, a compressor, and two refrigeration compartments. The configuration may be equipped with a variable-speed or variable-capacity compressor, variable speed evaporator or compartment fans, a damper, and/or a dual-temperature evaporator with a valve system to control flow of refrigerant through one or more pressure reduction devices. The methods may include synchronizing alternating cycles of cooling each compartment to a temperature approximately equal to the compartment set point temperature by operation of the compressor, fans, damper and/or valve system. The methods may also include controlling themore » cooling rate in one or both compartments. Refrigeration compartment cooling may begin at an interval before or after when the freezer compartment reaches its lower threshold temperature. Freezer compartment cooling may begin at an interval before or after when the freezer compartment reaches its upper threshold temperature.« less

Synchronous temperature rate control for refrigeration with reduced energy consumption

DOEpatents

Gomes, Alberto Regio; Keres, Stephen L.; Kuehl, Steven J.; Litch, Andrew D.; Richmond, Peter J.; Wu, Guolian

2015-09-22

Methods of operation for refrigerator appliance configurations with a controller, a condenser, at least one evaporator, a compressor, and two refrigeration compartments. The configuration may be equipped with a variable-speed or variable-capacity compressor, variable speed evaporator or compartment fans, a damper, and/or a dual-temperature evaporator with a valve system to control flow of refrigerant through one or more pressure reduction devices. The methods may include synchronizing alternating cycles of cooling each compartment to a temperature approximately equal to the compartment set point temperature by operation of the compressor, fans, damper and/or valve system. The methods may also include controlling the cooling rate in one or both compartments. Refrigeration compartment cooling may begin at an interval before or after when the freezer compartment reaches its lower threshold temperature. Freezer compartment cooling may begin at an interval before or after when the freezer compartment reaches its upper threshold temperature.

Performance of Power Converters at Cryogenic Temperatures

NASA Technical Reports Server (NTRS)

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

2001-01-01

Power converters capable of operation at cryogenic temperatures are anticipated to play an important role in the power system architecture of future NASA deep space missions. Design of such converters to survive cryogenic temperatures will improve the power system performance and reduce development and launch costs. Aerospace power systems are mainly a DC distribution network. Therefore, DC/DC and DC/AC converters provide the outputs needed to different loads at various power levels. Recently, research efforts have been performed at the NASA Glenn Research Center (GRC) to design and evaluate DC/DC converters that are capable of operating at cryogenic temperatures. This paper presents a summary of the research performed to evaluate the low temperature performance of five DC/DC converters. Various parameters were investigated as a function of temperature in the range of 20 to -196 C. Data pertaining to the output voltage regulation and efficiency of the converters is presented and discussed.

Hemodynamic and thermal responses to head and neck cooling in men and women

NASA Technical Reports Server (NTRS)

Ku, Y. T.; Montgomery, L. D.; Webbon, B. W.

1996-01-01

Personal cooling systems are used to alleviate symptoms of multiple sclerosis and to prevent increased core temperature during daily activities. The objective of this study was to determine the operating characteristics and the physiologic changes produced by short term use of one commercially available thermal control system. A Life Support Systems, Inc. Mark VII portable cooling system and a liquid cooling helmet were used to cool the head and neck regions of 12 female and 12 male subjects (25-55 yr) in this study. The healthy subjects, seated in an upright position at normal room temperature (approximately 21 degrees C), were tested for 30 min with the liquid cooling garment operated at its maximum cooling capacity. Electrocardiograms and scalp and intracranial blood flows were recorded periodically during each test sequence. Scalp, right and left ear, and oral temperatures and cooling system parameters were logged every 5 min. Scalp, right and left ear canal, and oral temperatures were all significantly (P <0.05) reduced by 30 min of head and neck cooling. Oral temperatures decreased approximately 0.2-0.6 degrees C after 30 min and continued to decrease further (approximately 0.1-0.2 degrees C) for a period of approximately 10 min after removal of the cooling helmet. Intracranial blood flow decreased significantly (P < 0.05) during the first 10 min of the cooling period. Both right and left ear temperatures in the women were significantly lower than those of the men during the cooling period. These data indicate that head and neck cooling may be used to reduce core temperature to that needed for symptomatic relief of both male and female multiple sclerosis patients. This study quantifies the operating characteristics of one liquid cooling garment as an example of the information needed to compare the efficiency of other garments operated under different test conditions.

E-Gun Technology

DTIC Science & Technology

1981-07-01

at high temperature . This situation was alleviated by removing most of the molybdenum sur- face contact by milling the clips to two 1/8 in. wide strips...sides. Molybdenum is used because its high - temperature capability and compatibility with barium dispenser cathodes, and the tabs are made thin to reduce...and operating temperatures than normal were required to overcome the high arrival rate of contami- nants such as oxygen for the relatively high

A High Frequency (HF) Inductive Power Transfer Circuit for High Temperature Applications Using SiC Schottky Diodes

NASA Technical Reports Server (NTRS)

Jordan, Jennifer L.; Ponchak, George E.; Spry, David J.; Neudeck, Philip G.

2018-01-01

Wireless sensors placed in high temperature environments, such as aircraft engines, are desirable to reduce the mass and complexity of routing wires. While communication with the sensors is straight forward, providing power wirelessly is still a challenge. This paper introduces an inductive wireless power transfer circuit incorporating SiC Schottky diodes and its operation from room temperature (25 C) to 500 C.

Evaluation of Capacitors at Cryogenic Temperatures for Space Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Gerber, Scott S.

1998-01-01

Advanced electronic systems designed for use in planetary exploration missions must operate efficiently and reliably under the extreme cold temperatures of deep space environment. In addition, spacecraft power electronics capable of cold temperature operation will greatly simplify the thermal management system by eliminating the need for heating units and associated equipment and thereby reduce the size and weight of the overall power system. In this study, film, mica, solid tantalum and electric double layer capacitors were evaluated as a function of temperature from room to liquid nitrogen in terms of their dielectric properties. These properties included capacitance stability and dielectric loss in the frequency range of 50 Hz to 100 kHz. DC leakage current measurements were also performed on the capacitors. The results obtained are discussed and conclusions are made concerning the suitability of the capacitors investigated for low temperature applications.

Demonstration of catalytic combustion with residual fuel

NASA Technical Reports Server (NTRS)

Dodds, W. J.; Ekstedt, E. E.

1981-01-01

An experimental program was conducted to demonstrate catalytic combustion of a residual fuel oil. Three catalytic reactors, including a baseline configuration and two backup configurations based on baseline test results, were operated on No. 6 fuel oil. All reactors were multielement configurations consisting of ceramic honeycomb catalyzed with palladium on stabilized alumina. Stable operation on residual oil was demonstrated with the baseline configuration at a reactor inlet temperature of about 825 K (1025 F). At low inlet temperature, operation was precluded by apparent plugging of the catalytic reactor with residual oil. Reduced plugging tendency was demonstrated in the backup reactors by increasing the size of the catalyst channels at the reactor inlet, but plugging still occurred at inlet temperature below 725 K (845 F). Operation at the original design inlet temperature of 589 K (600 F) could not be demonstrated. Combustion efficiency above 99.5% was obtained with less than 5% reactor pressure drop. Thermally formed NO sub x levels were very low (less than 0.5 g NO2/kg fuel) but nearly 100% conversion of fuel-bound nitrogen to NO sub x was observed.

Tuning the transition temperature of WSi$$_{x}$$ alloys for use in cryogenic microcalorimeters

DOE PAGES

Cecil, T.; Gades, L.; Madden, T.; ...

2016-03-10

Here, microwave kinetic inductance detectors (MKID) provide a pathway to highly multiplexed, high-resolution, detectors. Over the past several years we have introduced the concept of the Thermal Kinetic Inductance Detector (TKID), which operates as a microcalorimeter. As with other microcalorimeters, the thermal noise of a TKID is reduced when the operating temperature is decreased. However, because the sensitivity of a TKID decreases as the operating temperature drops below 20% of T C, the T C of the resonator material must be tuned to match the desired operating temperature. We have investigated the WSimore » $$_{x}$$ alloy system as a material for these detectors. By co-sputtering from a Si andW2Si target, we have deposited WSi$$_{x}$$ films with a tunable T C that ranges from 5 K down to 500 mK. These films provide a large kinetic inductance fraction and relatively low noise levels. We provide results of these studies showing the T C, resistivity, quality factors, and noise as a function of deposition conditions. These results show that WSi$$_{x}$$ is a good candidate for TKIDs.« less

Industrial trials of low-expansivity sawblades

Treesearch

Jeanne D. Danielson; Frank J. Worzala

1992-01-01

Low-expansivity alloys have the potential to reduce thermal instability of sawblades during the sawing operation. In preliminary industrial trials of sawblades made of low-expansivity alloy, sawing accuracy was improved 22 to 38 percent during normal sawing. When saws made of a low-expansivity alloy were operated with a large temperature gradient across the blade,...

Cryogenic exciter

DOEpatents

Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

2012-03-13

The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

Electrochemical cell

DOEpatents

Redey, L.I.; Vissers, D.R.; Prakash, J.

1994-02-01

An electrochemical cell is described having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm[sup 3]; the cell can be 90% recharged in three hours and can operate at temperatures below 160 C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6[times]10[sup 4] cm[sup 2]/g of Ni. 8 figures.

Electrochemical cell

DOEpatents

Redey, Laszlo I.; Vissers, Donald R.; Prakash, Jai

1994-01-01

An electrochemical cell having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm.sup.3 ; the cell can be 90% recharged in three hours and can operate at temperatures below 160.degree. C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6.times.10.sup.4 cm.sup.2 /g of Ni.

Electrochemical cell

DOEpatents

Redey, Laszlo I.; Vissers, Donald R.; Prakash, Jai

1996-01-01

An electrochemical cell having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm.sup.3 ; the cell can be 90% recharged in three hours and can operate at temperatures below 160.degree. C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6.times.10.sup.4 cm.sup.2 /g of Ni.

Electrochemical cell

DOEpatents

Redey, L.I.; Vissers, D.R.; Prakash, J.

1996-07-16

An electrochemical cell is described having a bimodal positive electrode, a negative electrode of an alkali metal, and a compatible electrolyte including an alkali metal salt molten at the cell operating temperature. The positive electrode has an electrochemically active layer of at least one transition metal chloride at least partially present as a charging product, and additives of bromide and/or iodide and sulfur in the positive electrode or the electrolyte. Electrode volumetric capacity is in excess of 400 Ah/cm{sup 3}; the cell can be 90% recharged in three hours and can operate at temperatures below 160 C. There is also disclosed a method of reducing the operating temperature and improving the overall volumetric capacity of an electrochemical cell and for producing a positive electrode having a BET area greater than 6{times}10{sup 4}cm{sup 2}/g of Ni. 6 figs.

Room temperature solid-state quantum emitters in the telecom range.

PubMed

Zhou, Yu; Wang, Ziyu; Rasmita, Abdullah; Kim, Sejeong; Berhane, Amanuel; Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam; Aharonovich, Igor; Gao, Wei-Bo

2018-03-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies.

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor.

PubMed

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Li, Wangwang; Zhang, Diya; Xiong, Jijun

2016-07-22

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations.

Passive Resistor Temperature Compensation for a High-Temperature Piezoresistive Pressure Sensor

PubMed Central

Yao, Zong; Liang, Ting; Jia, Pinggang; Hong, Yingping; Qi, Lei; Lei, Cheng; Zhang, Bin; Li, Wangwang; Zhang, Diya; Xiong, Jijun

2016-01-01

The main limitation of high-temperature piezoresistive pressure sensors is the variation of output voltage with operating temperature, which seriously reduces their measurement accuracy. This paper presents a passive resistor temperature compensation technique whose parameters are calculated using differential equations. Unlike traditional experiential arithmetic, the differential equations are independent of the parameter deviation among the piezoresistors of the microelectromechanical pressure sensor and the residual stress caused by the fabrication process or a mismatch in the thermal expansion coefficients. The differential equations are solved using calibration data from uncompensated high-temperature piezoresistive pressure sensors. Tests conducted on the calibrated equipment at various temperatures and pressures show that the passive resistor temperature compensation produces a remarkable effect. Additionally, a high-temperature signal-conditioning circuit is used to improve the output sensitivity of the sensor, which can be reduced by the temperature compensation. Compared to traditional experiential arithmetic, the proposed passive resistor temperature compensation technique exhibits less temperature drift and is expected to be highly applicable for pressure measurements in harsh environments with large temperature variations. PMID:27455271

Flexible and Self-Healing Aqueous Supercapacitors for Low Temperature Applications: Polyampholyte Gel Electrolytes with Biochar Electrodes.

PubMed

Li, Xinda; Liu, Li; Wang, Xianzong; Ok, Yong Sik; Elliott, Janet A W; Chang, Scott X; Chung, Hyun-Joong

2017-05-10

A flexible and self-healing supercapacitor with high energy density in low temperature operation was fabricated using a combination of biochar-based composite electrodes and a polyampholyte hydrogel electrolyte. Polyampholytes, a novel class of tough hydrogel, provide self-healing ability and mechanical flexibility, as well as low temperature operation for the aqueous electrolyte. Biochar is a carbon material produced from the low-temperature pyrolysis of biological wastes; the incorporation of reduced graphene oxide conferred mechanical integrity and electrical conductivity and hence the electrodes are called biochar-reduced-graphene-oxide (BC-RGO) electrodes. The fabricated supercapacitor showed high energy density of 30 Wh/kg with ~90% capacitance retention after 5000 charge-discharge cycles at room temperature at a power density of 50 W/kg. At -30 °C, the supercapacitor exhibited an energy density of 10.5 Wh/kg at a power density of 500 W/kg. The mechanism of the low-temperature performance excellence is likely to be associated with the concept of non-freezable water near the hydrophilic polymer chains, which can motivate future researches on the phase behaviour of water near polyampholyte chains. We conclude that the combination of the BC-RGO electrode and the polyampholyte hydrogel electrolyte is promising for supercapacitors for flexible electronics and for low temperature environments.

High temperature thruster technology for spacecraft propulsion

NASA Technical Reports Server (NTRS)

Schneider, Steven J.

1991-01-01

A technology program intended to develop high-temperature oxidation-resistant thrusters for spacecraft applications is considered. The program will provide the requisite material characterizations and fabrication to incorporate iridium coated rhenium material into small rockets for spacecraft propulsion. This material increases the operating temperature of thrusters to 2200 C, a significant increase over the 1400 C of the silicide-coated niobium chambers currently used. Stationkeeping class 22 N engines fabricated from iridium-coated rhenium have demonstrated steady state specific impulses 20-25 seconds higher than niobium chambers. These improved performances are obtained by reducing or eliminating the fuel film cooling requirements in the combustion chamber while operating at the same overall mixture ratio as conventional engines.

Synchronous compartment temperature control and apparatus for refrigeration with reduced energy consumption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gomes, Alberto Regio; Keres, Stephen L.; Kuehl, Stephen J.

A refrigerator appliance configuration, and associated methods of operation, for an appliance with a controller, a condenser, at least one evaporator, a compressor, and two refrigeration compartments. The configuration may be equipped with a variable-speed or variable-capacity compressor, variable speed evaporator or compartment fans, a damper and/or a dual-temperature evaporator with a valve system to control flow of refrigerant through one or more pressure reduction devices. The controller, by operation of the compressor, fans, damper and/or valve system, depending on the appliance configuration, controls the cooling rate in one or both compartments to synchronize, alternating cycles of cooling the compartmentsmore » to their set point temperatures.« less

Temperature Induced Voltage Offset Drifts in Silicon Carbide Pressure Sensors

NASA Technical Reports Server (NTRS)

Okojie, Robert S.; Lukco, Dorothy; Nguyen, Vu; Savrun, Ender

2012-01-01

We report the reduction of transient drifts in the zero pressure offset voltage in silicon carbide (SiC) pressure sensors when operating at 600 C. The previously observed maximum drift of +/- 10 mV of the reference offset voltage at 600 C was reduced to within +/- 5 mV. The offset voltage drifts and bridge resistance changes over time at test temperature are explained in terms of the microstructure and phase changes occurring within the contact metallization, as analyzed by Auger electron spectroscopy and field emission scanning electron microscopy. The results have helped to identify the upper temperature reliable operational limit of this particular metallization scheme to be 605 C.

Assimilation of Freeze - Thaw Observations into the NASA Catchment Land Surface Model

NASA Technical Reports Server (NTRS)

Farhadi, Leila; Reichle, Rolf H.; DeLannoy, Gabrielle J. M.; Kimball, John S.

2014-01-01

The land surface freeze-thaw (F-T) state plays a key role in the hydrological and carbon cycles and thus affects water and energy exchanges and vegetation productivity at the land surface. In this study, we developed an F-T assimilation algorithm for the NASA Goddard Earth Observing System, version 5 (GEOS-5) modeling and assimilation framework. The algorithm includes a newly developed observation operator that diagnoses the landscape F-T state in the GEOS-5 Catchment land surface model. The F-T analysis is a rule-based approach that adjusts Catchment model state variables in response to binary F-T observations, while also considering forecast and observation errors. A regional observing system simulation experiment was conducted using synthetically generated F-T observations. The assimilation of perfect (error-free) F-T observations reduced the root-mean-square errors (RMSE) of surface temperature and soil temperature by 0.206 C and 0.061 C, respectively, when compared to model estimates (equivalent to a relative RMSE reduction of 6.7 percent and 3.1 percent, respectively). For a maximum classification error (CEmax) of 10 percent in the synthetic F-T observations, the F-T assimilation reduced the RMSE of surface temperature and soil temperature by 0.178 C and 0.036 C, respectively. For CEmax=20 percent, the F-T assimilation still reduces the RMSE of model surface temperature estimates by 0.149 C but yields no improvement over the model soil temperature estimates. The F-T assimilation scheme is being developed to exploit planned operational F-T products from the NASA Soil Moisture Active Passive (SMAP) mission.

Predicting Young’s Modulus of Glass/Ceramic Sealant for Solid Oxide Fuel Cell Considering the Combined Effects of Aging, Micro-Voids and Self-Healing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

We study the temperature dependent Young’s modulus for the glass/ceramic seal material used in Solid Oxide Fuel Cells (SOFCs). With longer heat treatment or aging time during operation, further devitrification may reduce the residual glass content in the seal material while boosting the ceramic crystalline content. In the meantime, micro-voids induced by the cooling process from the high operating temperature to room temperature can potentially degrade the mechanical properties of the glass/ceramic sealant. Upon reheating to the SOFC operating temperature, possible self-healing phenomenon may occur in the glass/ceramic sealant which can potentially restore some of its mechanical properties. A phenomenologicalmore » model is developed to model the temperature dependent Young’s modulus of glass/ceramic seal considering the combined effects of aging, micro-voids, and possible self-healing. An aging-time-dependent crystalline content model is first developed to describe the increase of the crystalline content due to the continuing devitrification under high operating temperature. A continuum damage mechanics (CDM) model is then adapted to model the effects of both cooling induced micro-voids and reheating induced self-healing. This model is applied to model the glass-ceramic G18, a candidate SOFC seal material previously developed at PNNL. Experimentally determined temperature dependent Young’s modulus is used to validate the model predictions« less

Charge dissipative dielectric for cryogenic devices

NASA Technical Reports Server (NTRS)

Cantor, Robin Harold (Inventor); Hall, John Addison (Inventor)

2007-01-01

A Superconducting Quantum Interference Device (SQUID) is disclosed comprising a pair of resistively shunted Josephson junctions connected in parallel within a superconducting loop and biased by an external direct current (dc) source. The SQUID comprises a semiconductor substrate and at least one superconducting layer. The metal layer(s) are separated by or covered with a semiconductor material layer having the properties of a conductor at room temperature and the properties of an insulator at operating temperatures (generally less than 100 Kelvins). The properties of the semiconductor material layer greatly reduces the risk of electrostatic discharge that can damage the device during normal handling of the device at room temperature, while still providing the insulating properties desired to allow normal functioning of the device at its operating temperature. A method of manufacturing the SQUID device is also disclosed.

An Integrated Chemical Reactor-Heat Exchanger Based on Ammonium Carbamate (POSTPRINT)

DTIC Science & Technology

2012-10-01

With the scrubber and exhaust operating, the test cell ammonia concentration remains below 5 ppm. To further reduce NH3 release into the test cell...material has a high decomposition enthalpy and exhibits decomposition over a wide range of temperatures. AC decomposition produces ammonia and carbon...installation due to toxic gas ( ammonia ) generation during operation. Therefore, the experiment is intended to be remotely operated. A secondary control

Field test and simulation evaluation of variable refrigerant flow systems performance

DOE PAGES

Lee, Je Hyeon; Im, Piljae; Song, Young-hak

2017-10-24

Our study aims to compare the performance of a Variable Refrigerant Flow (VRF) system with a Roof Top Unit, (RTU) and a variable-air-volume (VAV) system through field tests and energy simulations. The field test was conducted in as similar conditions as possible between the two systems, such as the installation and operating environments of heating, the ventilation and air conditioning (HVAC) system, including internal heat gain and outdoor conditions, including buildings to compare the performance of the two systems accurately. A VRF system and RTU were installed at the test building located in Oak Ridge, Tennessee, in the USA. Themore » same internal heat gain was generated at the same operating time of the two systems using lighting, electric heaters, and humidifiers inside the building. The HVAC system was alternately operated between cooling and heating operations to acquire energy performance data and to compare energy usage. Furthermore, an hourly building energy simulation model was developed with regard to the VRF system and RTU, and then the model was calibrated using actual measured data. Then, annual energy consumption of the two systems were compared and analyzed using the calibrated model. Moreover, additional analysis was conducted when the controlled discharge air temperature in the RTU was changed. The field test result showed that when energy consumptions of two systems were compared at the same outdoor conditions, using the weather-normalized model, the VRF system exhibited an energy reduction of approximately 17% during cooling operation and of approximately 74% during heating operations. A comparison on the annual energy consumption using simulations showed that the VRF system reduced energy consumption more than that of the RTU by 60%. Furthermore, when the discharge air temperature in the RTU was controlled according to the outdoor air temperature, energy consumption of the RTU was reduced by 6% in cooling operations and by 18% in heating operation. As a result, energy consumption of the VRF system was reduced by more than that of the RTU by 55% approximately.« less

Field test and simulation evaluation of variable refrigerant flow systems performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Je Hyeon; Im, Piljae; Song, Young-hak

Our study aims to compare the performance of a Variable Refrigerant Flow (VRF) system with a Roof Top Unit, (RTU) and a variable-air-volume (VAV) system through field tests and energy simulations. The field test was conducted in as similar conditions as possible between the two systems, such as the installation and operating environments of heating, the ventilation and air conditioning (HVAC) system, including internal heat gain and outdoor conditions, including buildings to compare the performance of the two systems accurately. A VRF system and RTU were installed at the test building located in Oak Ridge, Tennessee, in the USA. Themore » same internal heat gain was generated at the same operating time of the two systems using lighting, electric heaters, and humidifiers inside the building. The HVAC system was alternately operated between cooling and heating operations to acquire energy performance data and to compare energy usage. Furthermore, an hourly building energy simulation model was developed with regard to the VRF system and RTU, and then the model was calibrated using actual measured data. Then, annual energy consumption of the two systems were compared and analyzed using the calibrated model. Moreover, additional analysis was conducted when the controlled discharge air temperature in the RTU was changed. The field test result showed that when energy consumptions of two systems were compared at the same outdoor conditions, using the weather-normalized model, the VRF system exhibited an energy reduction of approximately 17% during cooling operation and of approximately 74% during heating operations. A comparison on the annual energy consumption using simulations showed that the VRF system reduced energy consumption more than that of the RTU by 60%. Furthermore, when the discharge air temperature in the RTU was controlled according to the outdoor air temperature, energy consumption of the RTU was reduced by 6% in cooling operations and by 18% in heating operation. As a result, energy consumption of the VRF system was reduced by more than that of the RTU by 55% approximately.« less

High-Performance LWIR Superlattice Detectors and FPA Based on CBIRD Design

NASA Technical Reports Server (NTRS)

Soibel, Alexander; Nguyen, Jean; Khoshakhlagh, Arezou; Rafol, Sir B.; Hoeglund, Linda; Keo, Sam A.; Mumolo, Jason M.; Liu, John; Liao, Anna; Ting, David Z.-Y.;

Silicon-On-Insulator (SOI) Devices and Mixed-Signal Circuits for Extreme Temperature Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad; Elbuluk, Malik

2008-01-01

Electronic systems in planetary exploration missions and in aerospace applications are expected to encounter extreme temperatures and wide thermal swings in their operational environments. Electronics designed for such applications must, therefore, be able to withstand exposure to extreme temperatures and to perform properly for the duration of the missions. Electronic parts based on silicon-on-insulator (SOI) technology are known, based on device structure, to provide faster switching, consume less power, and offer better radiation-tolerance compared to their silicon counterparts. They also exhibit reduced current leakage and are often tailored for high temperature operation. However, little is known about their performance at low temperature. The performance of several SOI devices and mixed-signal circuits was determined under extreme temperatures, cold-restart, and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of these devices for use in space exploration missions under extreme temperatures. The experimental results obtained on selected SOI devices are presented and discussed in this paper.

DOE Office of Scientific and Technical Information (OSTI.GOV)

S.K. Kawatra; B. Anamerie; T.C. Eisele

The pig iron nugget process was developed as an alternative to the traditional blast furnace process by Kobe Steel. The process aimed to produce pig iron nuggets, which have similar chemical and physical properties to blast furnace pig iron, in a single step. The pig iron nugget process utilizes coal instead of coke and self reducing and fluxing dried green balls instead of pellets and sinters. In this process the environmental emissions caused by coke and sinter production, and energy lost between pellet induration (heat hardening) and transportation to the blast furnace can be eliminated. The objectives of this researchmore » were to (1) produce pig iron nuggets in the laboratory, (2) characterize the pig iron nugget produced and compare them with blast furnace pig iron, (3) investigate the furnace temperature and residence time effects on the pig iron nugget production, and (4) optimize the operational furnace temperatures and residence times. The experiments involved heat treatment of self reducing and fluxing dried green balls at various furnace temperatures and residence times. Three chemically and physically different products were produced after the compete reduction of iron oxides to iron depending on the operational furnace temperatures and/or residence times. These products were direct reduced iron (DRI), transition direct reduced iron (TDRI), and pig iron nuggets. The increase in the carbon content of the system as a function of furnace temperature and/or residence time dictated the formation of these products. The direct reduced iron, transition direct reduced iron, and pig iron nuggets produced were analyzed for their chemical composition, degree of metallization, apparent density, microstructure and microhardness. In addition, the change in the carbon content of the system with the changing furnace temperature and/or residence time was detected by optical microscopy and Microhardness measurements. The sufficient carbon dissolution required for the production of pig iron nuggets was determined. It was determined that pig iron nuggets produced had a high apparent density (6.7-7.2 gr/cm3), highly metallized, slag free structure, high iron content (95-97%), high microhardness values (> 325 HVN) and microstructure similar to white cast iron. These properties made them a competitive alternative to blast furnace pig iron.« less

Pretreatment of a primary and secondary sludge blend at different thermal hydrolysis temperatures: Impacts on anaerobic digestion, dewatering and filtrate characteristics.

PubMed

Higgins, Matthew J; Beightol, Steven; Mandahar, Ushma; Suzuki, Ryu; Xiao, Steven; Lu, Hung-Wei; Le, Trung; Mah, Joshua; Pathak, Bipin; DeClippeleir, Haydee; Novak, John T; Al-Omari, Ahmed; Murthy, Sudhir N

2017-10-01

A study was performed to evaluate the effect of thermal hydrolysis pretreatment (THP) temperature on subsequent digestion performance and operation, as well as downstream parameters such as dewatering and cake quality. A blend of primary and secondary solids from the Blue Plains treatment plant in Washington, DC was dewatered to about 16% total solids (TS), and thermally hydrolyzed at five different temperatures 130, 140, 150, 160, 170 °C. The thermally hydrolyzed solids were then fed to five separate, 10 L laboratory digesters using the same feed concentration, 10.5% TS and a solids retention time (SRT) of 15 days. The digesters were operated over a six month period to achieve steady state conditions. The higher thermal hydrolysis temperatures generally improved the solids reduction and methane yields by about 5-6% over the temperature range. The increased temperature reduced viscosity of the solids and increased the cake solids after dewatering. The dissolved organic nitrogen and UV absorbance generally increased at the higher THP temperatures. Overall, operating at a higher temperature improved performance with a tradeoff of higher dissolved organic nitrogen and UV adsorbing materials in the return liquor. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication Of High-Tc Superconducting Integrated Circuits

NASA Technical Reports Server (NTRS)

Bhasin, Kul B.; Warner, Joseph D.

1992-01-01

Microwave ring resonator fabricated to demonstrate process for fabrication of passive integrated circuits containing high-transition-temperature superconductors. Superconductors increase efficiencies of communication systems, particularly microwave communication systems, by reducing ohmic losses and dispersion of signals. Used to reduce sizes and masses and increase aiming accuracies and tracking speeds of millimeter-wavelength, electronically steerable antennas. High-Tc superconductors preferable for such applications because they operate at higher temperatures than low-Tc superconductors do, therefore, refrigeration systems needed to maintain superconductivity designed smaller and lighter and to consume less power.

New constant-temperature operating mode for graphite calorimeter at LNE-LNHB.

PubMed

Daures, J; Ostrowsky, A

2005-09-07

The realization of the unit of absorbed dose at LNE-LNHB is based on calorimetry with the present GR8 graphite calorimeter. For this reason the calorimetric technique must be maintained, developed and improved in the laboratory. The usual quasi-adiabatic operating mode at LNHB is based on the thermal feedback between the core (sensitive element) and the jacket (adjacent body). When a core-jacket temperature difference is detected, a commercially available analogue PID (Proportional, Integral, Derivative) controller sends to the jacket an amount of electrical power to reduce this difference. Nevertheless, the core and jacket temperatures increase with irradiations and electrical calibrations whereas the surrounding is maintained at a fixed temperature to shield against the room temperature variations. At radiotherapy dose rates, fewer than ten measurements, or electrical calibrations, per day can be performed. This paper describes the new constant-temperature operating mode which has been implemented recently to improve flexibility in use and, to some extent, accuracy. The core and the jacket temperatures are maintained at fixed temperatures. A steady state is achieved without irradiation. Then, under irradiation, the electrical power needed to maintain the assigned temperature in the core is reduced by the amount of heat generated by ionizing radiation. The difference between these electrical powers, without and with irradiation, gives the mean absorbed dose rate to the core. The quality of this electrical power substitution measurement is strongly dependent upon the quality of the core and jacket thermal control. The core temperature is maintained at the set value using a digital PID regulator developed at the laboratory with LabView software on PC for this purpose. This regulator is versatile and particularly well suited for calorimetry purposes. Measurements in a cobalt-60 beam have shown no significant difference (<0.09%) between the two operating modes, with an equivalent reproducibility (1sigma < 0.06%). These results corroborate the negligible difference of heat transfer between steady and irradiation periods when working in quasi-adiabatic mode with thermal feedback between the core and the jacket. The new constant-temperature mode allows numerous and fully automated measurements. The electrical calibration is an integral part of the measurement; no extra runs are needed. It also allows faster thermal equilibrium before starting runs. Moreover the quality of vacuum within the gaps between the bodies is less important.

The Role of Phase Changes in TiO2/Pt/TiO2 Filaments

NASA Astrophysics Data System (ADS)

Bíró, Ferenc; Hajnal, Zoltán; Dücső, Csaba; Bársony, István

2018-04-01

This work analyses the role of phase changes in TiO2/Pt/TiO2 layer stacks for micro-heater application regarding their stability and reliable operation. The polycrystalline Pt layer wrapped in a TiO2 adhesion layer underwent a continuous recrystallisation in a self-heating operation causing a drift in the resistance ( R) versus temperature ( T) performance. Simultaneously, the TiO2 adhesion layer also deteriorates at high temperature by phase changes from amorphous to anatase and rutile crystallite formation, which not only influences the Pt diffusion in different migration phenomena, but also reduces the cross section of the Pt heater wire. Thorough scanning electron microscopy, energy dispersive spectroscopy, cross-sectional transmission electron microscopy (XTEM) and electron beam diffraction analysis of the structures operated at increasing temperature revealed the elemental structural processes leading to the instabilities and the accelerated degradation, resulting in rapid breakdown of the heater wire. Owing to stability and reliability criteria, the conditions for safe operation of these layer structures could be determined.

Hall Thruster Thermal Modeling and Test Data Correlation

NASA Technical Reports Server (NTRS)

Myers, James; Kamhawi, Hani; Yim, John; Clayman, Lauren

2016-01-01

The life of Hall Effect thrusters are primarily limited by plasma erosion and thermal related failures. NASA Glenn Research Center (GRC) in cooperation with the Jet Propulsion Laboratory (JPL) have recently completed development of a Hall thruster with specific emphasis to mitigate these limitations. Extending the operational life of Hall thursters makes them more suitable for some of NASA's longer duration interplanetary missions. This paper documents the thermal model development, refinement and correlation of results with thruster test data. Correlation was achieved by minimizing uncertainties in model input and recognizing the relevant parameters for effective model tuning. Throughout the thruster design phase the model was used to evaluate design options and systematically reduce component temperatures. Hall thrusters are inherently complex assemblies of high temperature components relying on internal conduction and external radiation for heat dispersion and rejection. System solutions are necessary in most cases to fully assess the benefits and/or consequences of any potential design change. Thermal model correlation is critical since thruster operational parameters can push some components/materials beyond their temperature limits. This thruster incorporates a state-of-the-art magnetic shielding system to reduce plasma erosion and to a lesser extend power/heat deposition. Additionally a comprehensive thermal design strategy was employed to reduce temperatures of critical thruster components (primarily the magnet coils and the discharge channel). Long term wear testing is currently underway to assess the effectiveness of these systems and consequently thruster longevity.

Thales Cryogenics rotary cryocoolers for HOT applications

NASA Astrophysics Data System (ADS)

Martin, Jean-Yves; Cauquil, Jean-Marc; Benschop, Tonny; Freche, Sébastien

2012-06-01

Thales Cryogenics has an extensive background in delivering reliable linear and rotary coolers for military, civil and space programs. Recent work carried out at detector level enable to consider a higher operation temperature for the cooled detectors. This has a direct impact on the cooling power required to the cryocooler. In continuation of the work presented last year, Thales cryogenics has studied the operation and optimization of the rotary cryocoolers at high cold regulation temperature. In this paper, the performances of the Thales Cryogenics rotary cryocoolers at elevated cold regulation temperature will be presented. From these results, some trade-offs can be made to combine correct operation of the cryocooler on all the ambient operational range and maximum efficiency of the cryocooler. These trade-offs and the impact on MTTF of elevated cold regulation temperature will be presented and discussed. In correlation with the increase of the cold operation temperature, the cryocooler input power is significantly decreased. As a consequence, the cooler drive electronics own consumption becomes relatively important and must be reduced in order to minimize global input power to the cooling function (cryocooler and cooler drive electronics). Thales Cryogenics has developed a new drive electronics optimized for low input power requirements. In parallel, improvements on RM1 and RM2 cryocoolers have been defined and implemented. The main impacts on performances of these new designs will be presented. Thales cryogenics is now able to propose an efficient cooling function for application requiring a high cold regulation temperature including a range of tuned rotary coolers.

Testing of a Helium Loop Heat Pipe for Large Area Cryocooling

NASA Technical Reports Server (NTRS)

Ku, Jentung; Robinson, Franklin

2016-01-01

Future NASA space telescopes and exploration missions require cryocooling of large areas such as optics, detector arrays, and cryogenic propellant tanks. One device that can potentially be used to provide closed-loop cryocooling is the cryogenic loop heat pipe (CLHP). A CLHP has many advantages over other devices in terms of reduced mass, reduced vibration, high reliability, and long life. A helium CLHP has been tested extensively in a thermal vacuum chamber using a cryocooler as the heat sink to characterize its transient and steady performance and verify its ability to cool large areas or components in the 3K temperature range. A copper plate with attached electrical heaters was used to simulate the heat source, and heat was collected by the CLHP evaporator and transferred to the cryocooler for ultimate heat rejection. The helium CLHP thermal performance test included cool-down from the ambient temperature, startup, capillary limit, heat removal capability, rapid power changes, and long duration steady state operation. The helium CLHP demonstrated robust operation under steady state and transient conditions. The loop could be cooled from the ambient temperature to subcritical temperatures very effectively, and could start successfully without pre-conditioning by simply applying power to both the capillary pump and the evaporator plate. It could adapt to rapid changes in the heat load, and reach a new steady state very quickly. Heat removal between 10mW and 140mW was demonstrated, yielding a power turn down ratio of 14. When the CLHP capillary limit was exceeded, the loop could resume its normal function by reducing the power to the capillary pump. Steady state operations up to 17 hours at several heat loads were demonstrated. The ability of the helium CLHP to cool large areas was therefore successfully verified.

Testing of a Helium Loop Heat Pipe for Large Area Cryocooling

NASA Technical Reports Server (NTRS)

Ku, Jentung; Robinson, Franklin Lee

2015-01-01

Future NASA space telescopes and exploration missions require cryocooling of large areas such as optics, detector arrays, and cryogenic propellant tanks. One device that can potentially be used to provide closed-loop cryocooling is the cryogenic loop heat pipe (CLHP). A CLHP has many advantages over other devices in terms of reduced mass, reduced vibration, high reliability, and long life. A helium CLHP has been tested extensively in a thermal vacuum chamber using a cryocooler as the heat sink to characterize its transient and steady performance and verify its ability to cool large areas or components in the 3K temperature range. A copper plate with attached electrical heters was used to simulate the heat source, and heat was collected by the CLHP evaporator and transferred to the cryocooler for ultimate heat rejection. The helium CLHP thermal performance test included cool-down from the ambient temperature, startup, capillary limit, heat removal capability, rapid power changes, and long duration steady state operation. The helium CLHP demonstrated robust operation under steady state and transient conditions. The loop could be cooled from the ambient temperature to subcritical temperatures very effectively, and could start successfully without pre-conditioning by simply applying power to both the capillary pump and the evaporator plate. It could adapt to rapid changes in the heat load, and reach a new steady state very quickly. Heat removal between 10mW and 140mW was demonstrated, yielding a power turn down ratio of 14. When the CLHP capillary limit was exceeded, the loop could resume its normal function by reducing the power to the capillary pump. Steady state operations up to 17 hours at several heat loads were demonstrated. The ability of the helium CLHP to cool large areas was therefore successfully verified.

Potential benefits of a ceramic thermal barrier coating on large power generation gas turbine

NASA Technical Reports Server (NTRS)

Clark, J. S.; Nainiger, J. J.

1977-01-01

Thermal barrier coating design option offers benefit in terms of reduced electricity costs when used in utility gas turbines. Options considered include: increased firing temperature, increased component life, reduced cooling air requirements, and increased corrosion resistance (resulting in increased tolerance for dirty fuels). Performance and cost data were obtained. Simple, recuperated and combined cycle applications were considered, and distillate and residual fuels were assumed. The results indicate that thermal barrier coatings could produce large electricity cost savings if these coatings permit turbine operation with residual fuels at distillate-rated firing temperatures. The results also show that increased turbine inlet temperature can result in substantial savings in fuel and capital costs.

Applications of high-temperature powder metal aluminum alloys to small gas turbines

NASA Technical Reports Server (NTRS)

Millan, P. P., Jr.

1982-01-01

A program aimed at the development of advanced powder-metallurgy (PM) aluminum alloys for high-temperature applications up to 650 F using the concepts of rapid solidification and mechanical alloying is discussed. In particular, application of rapidly solidified PM aluminum alloys to centrifugal compressor impellers, currently used in auxiliary power units for both military and commercial aircraft and potentially for advanced automotive gas turbine engines, is examined. It is shown that substitution of high-temperature aluminum for titanium alloy impellers operating in the 360-650 F range provides significant savings in material and machining costs and results in reduced component weight, and consequently, reduced rotating group inertia requirements.

Improved operation of graded-channel SOI nMOSFETs down to liquid helium temperature

NASA Astrophysics Data System (ADS)

Pavanello, Marcelo Antonio; de Souza, Michelly; Ribeiro, Thales Augusto; Martino, João Antonio; Flandre, Denis

2016-11-01

This paper presents the operation of Graded-Channel (GC) Silicon-On-Insulator (SOI) nMOSFETs at low temperatures down to liquid helium temperature in comparison to standard uniformly doped transistors. Devices from two different technologies have been measured and show that the mobility increase rate with temperature for GC SOI transistors is similar to uniformly doped devices for temperatures down to 90 K. However, at liquid helium temperature the rate of mobility increase is larger in GC SOI than in standard devices because of the different mobility scattering mechanisms. The analog properties of GC SOI devices have been investigated down to 4.16 K and show that because of its better transconductance and output conductance, an intrinsic voltage gain improvement with temperature is also obtained for devices in the whole studied temperature range. GC devices are also capable of reducing the impact ionization due to the high electric field in the drain region, increasing the drain breakdown voltage of fully-depleted SOI MOSFETs at any studied temperature and the kink voltage at 4.16 K.

The Role of Demand Response in Reducing Water-Related Power Plant Vulnerabilities

NASA Astrophysics Data System (ADS)

Macknick, J.; Brinkman, G.; Zhou, E.; O'Connell, M.; Newmark, R. L.; Miara, A.; Cohen, S. M.

2015-12-01

The electric sector depends on readily available water supplies for reliable and efficient operation. Elevated water temperatures or low water levels can trigger regulatory or plant-level decisions to curtail power generation, which can affect system cost and reliability. In the past decade, dozens of power plants in the U.S. have curtailed generation due to water temperatures and water shortages. Curtailments occur during the summer, when temperatures are highest and there is greatest demand for electricity. Climate change could alter the availability and temperature of water resources, exacerbating these issues. Constructing alternative cooling systems to address vulnerabilities can be capital intensive and can also affect power plant efficiencies. Demand response programs are being implemented by electric system planners and operators to reduce and shift electricity demands from peak usage periods to other times of the day. Demand response programs can also play a role in reducing water-related power sector vulnerabilities during summer months. Traditionally, production cost modeling and demand response analyses do not include water resources. In this effort, we integrate an electricity production cost modeling framework with water-related impacts on power plants in a test system to evaluate the impacts of demand response measures on power system costs and reliability. Specifically, we i) quantify the cost and reliability implications of incorporating water resources into production cost modeling, ii) evaluate the impacts of demand response measures on reducing system costs and vulnerabilities, and iii) consider sensitivity analyses with cooling systems to highlight a range of potential benefits of demand response measures. Impacts from climate change on power plant performance and water resources are discussed. Results provide key insights to policymakers and practitioners for reducing water-related power plant vulnerabilities via lower cost methods.

Development of advanced high temperature in-cylinder components and tribological systems for low heat rejection diesel engines, phase 1

NASA Astrophysics Data System (ADS)

Kroeger, C. A.; Larson, H. J.

1992-03-01

Analysis and concept design work completed in Phase 1 have identified a low heat rejection engine configuration with the potential to meet the Heavy Duty Transport Technology program specific fuel consumption goal of 152 g/kW-hr. The proposed engine configuration incorporates low heat rejection, in-cylinder components designed for operation at 24 MPa peak cylinder pressure. Water cooling is eliminated by selective oil cooling of the components. A high temperature lubricant will be required due to increased in-cylinder operating temperatures. A two-stage turbocharger air system with intercooling and aftercooling was selected to meet engine boost and BMEP requirements. A turbocompound turbine stage is incorporated for exhaust energy recovery. The concept engine cost was estimated to be 43 percent higher compared to a Caterpillar 3176 engine. The higher initial engine cost is predicted to be offset by reduced operating costs due the lower fuel consumption.

Room temperature solid-state quantum emitters in the telecom range

PubMed Central

Bodrog, Zoltán; Adamo, Giorgio; Gali, Adam

2018-01-01

On-demand, single-photon emitters (SPEs) play a key role across a broad range of quantum technologies. In quantum networks and quantum key distribution protocols, where photons are used as flying qubits, telecom wavelength operation is preferred because of the reduced fiber loss. However, despite the tremendous efforts to develop various triggered SPE platforms, a robust source of triggered SPEs operating at room temperature and the telecom wavelength is still missing. We report a triggered, optically stable, room temperature solid-state SPE operating at telecom wavelengths. The emitters exhibit high photon purity (~5% multiphoton events) and a record-high brightness of ~1.5 MHz. The emission is attributed to localized defects in a gallium nitride (GaN) crystal. The high-performance SPEs embedded in a technologically mature semiconductor are promising for on-chip quantum simulators and practical quantum communication technologies. PMID:29670945

Development of advanced high temperature in-cylinder components and tribological systems for low heat rejection diesel engines, phase 1

NASA Technical Reports Server (NTRS)

Kroeger, C. A.; Larson, H. J.

1992-01-01

Analysis and concept design work completed in Phase 1 have identified a low heat rejection engine configuration with the potential to meet the Heavy Duty Transport Technology program specific fuel consumption goal of 152 g/kW-hr. The proposed engine configuration incorporates low heat rejection, in-cylinder components designed for operation at 24 MPa peak cylinder pressure. Water cooling is eliminated by selective oil cooling of the components. A high temperature lubricant will be required due to increased in-cylinder operating temperatures. A two-stage turbocharger air system with intercooling and aftercooling was selected to meet engine boost and BMEP requirements. A turbocompound turbine stage is incorporated for exhaust energy recovery. The concept engine cost was estimated to be 43 percent higher compared to a Caterpillar 3176 engine. The higher initial engine cost is predicted to be offset by reduced operating costs due the lower fuel consumption.

Challenges and New Trends for Piezoelectric Actuators

NASA Technical Reports Server (NTRS)

Sehirlioglu, Alp

2008-01-01

BiScO3-PbTiO3 ceramics with TC greater than 400 C has been successfully processed. Despite the increase in TC, excess Pb addition increases both the bulk conductivity and the grain boundary contribution to conductivity at elevated temperatures. Conductivity at elevated temperatures, that limits the operating temperature for actuators, has been greatly reduced by excess Bi additions. Excess Bi doping improves poling conditions resulting in enhanced piezoelectric coefficient (d(sub 33) = 408 pC/N).

[Thermal energy utilization analysis and energy conservation measures of fluidized bed dryer].

PubMed

Xing, Liming; Zhao, Zhengsheng

2012-07-01

To propose measures for enhancing thermal energy utilization by analyzing drying process and operation principle of fluidized bed dryers,in order to guide optimization and upgrade of fluidized bed drying equipment. Through a systematic analysis on drying process and operation principle of fluidized beds,the energy conservation law was adopted to calculate thermal energy of dryers. The thermal energy of fluidized bed dryers is mainly used to make up for thermal consumption of water evaporation (Qw), hot air from outlet equipment (Qe), thermal consumption for heating and drying wet materials (Qm) and heat dissipation to surroundings through hot air pipelines and cyclone separators. Effective measures and major approaches to enhance thermal energy utilization of fluidized bed dryers were to reduce exhaust gas out by the loss of heat Qe, recycle dryer export air quantity of heat, preserve heat for dry towers, hot air pipes and cyclone separators, dehumidify clean air in inlets and reasonably control drying time and air temperature. Such technical parameters such air supply rate, air inlet temperature and humidity, material temperature and outlet temperature and humidity are set and controlled to effectively save energy during the drying process and reduce the production cost.

Operating characteristics of a three-piece-inner-ring large-bore roller bearing to speeds of 3 million DN

NASA Technical Reports Server (NTRS)

Schuller, F. T.

1984-01-01

A 118 mm bore roller bearing with a three piece inner ring ran successfully at 300,000 DN for 20 hr. Provisions were made for lubrication and cooling through the inner ring. In some tests the outer ring was also cooled. Power loss within the bearing increased with both speed and total oil flow rate to the inner ring. Outer ring temperature decreased by as much as 22 K (40 F) when outer ring cooling was employed whereas inner ring temperature remained essentially constant. Cage slip was greatly reduced or even eliminated by using a bearing with a very tight clearance at operating speed. A three piece inner ring bearing had higher inner ring temperatures and less temperature difference between the inner and outer rings than a conventional one piece inner ring bearing.

Advanced intermediate temperature sodium copper chloride battery

NASA Astrophysics Data System (ADS)

Yang, Li-Ping; Liu, Xiao-Min; Zhang, Yi-Wei; Yang, Hui; Shen, Xiao-Dong

2014-12-01

Sodium metal chloride batteries, also called as ZEBRA batteries, possess many merits such as low cost, high energy density and high safety, but their high operation temperature (270-350 °C) may cause several issues and limit their applications. Therefore, decreasing the operation temperature is of great importance in order to broaden their usage. Using a room temperature ionic liquid (RTIL) catholyte composed of sodium chloride buffered 1-ethyl-3-methylimidazolium chloride-aluminum chloride and a dense β″-aluminates solid electrolyte film with 500 micron thickness, we report an intermediate temperature sodium copper chloride battery which can be operated at only 150 °C, therefore alleviating the corrosion issues, improving the material compatibilities and reducing the operating complexities associated with the conventional ZEBRA batteries. The RTIL presents a high ionic conductivity (0.247 S cm-1) at 150 °C and a wide electrochemical window (-2.6 to 2.18 vs. Al3+/Al). With the discharge plateau at 2.64 V toward sodium and the specific capacity of 285 mAh g-1, this intermediate temperature battery exhibits an energy density (750 mWh g-1) comparable to the conventional ZEBRA batteries (728-785 mWh g-1) and superior to commercialized Li-ion batteries (550-680 mWh g-1), making it very attractive for renewable energy integration and other grid related applications.

Ternary compound electrode for lithium cells

DOEpatents

Raistrick, I.D.; Godshall, N.A.; Huggins, R.A.

1980-07-30

Lithium-based cells are promising for applications such as electric vehicles and load-leveling for power plants since lithium is very electropositive and of light weight. One type of lithium-based cell utilizes a molten salt electrolyte and normally is operated in the temperature range of about 350 to 500/sup 0/C. Such high temperature operation accelerates corrosion problems. The present invention provides an electrochemical cell in which lithium is the electroactive species. The cell has a positive electrode which includes a ternary compound generally represented as Li-M-O, wherein M is a transition metal. Corrosion of the inventive cell is considerably reduced.

Ternary compound electrode for lithium cells

DOEpatents

Raistrick, Ian D.; Godshall, Ned A.; Huggins, Robert A.

1982-01-01

Lithium-based cells are promising for applications such as electric vehicles and load-leveling for power plants since lithium is very electropositive and of light weight. One type of lithium-based cell utilizes a molten salt electrolyte and normally is operated in the temperature range of about 350.degree.-500.degree. C. Such high temperature operation accelerates corrosion problems. The present invention provides an electrochemical cell in which lithium is the electroactive species. The cell has a positive electrode which includes a ternary compound generally represented as Li-M-O, wherein M is a transition metal. Corrosion of the inventive cell is considerably reduced.

Advanced High Temperature Structural Seals

NASA Astrophysics Data System (ADS)

Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

2002-10-01

This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

Advanced High Temperature Structural Seals

NASA Technical Reports Server (NTRS)

Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

2002-01-01

This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

Multiple delivery cesium oven system for negative ion sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansal, G.; Bhartiya, S.; Pandya, K.

2012-02-15

Distribution of cesium in large negative ion beam sources to be operational in ITER, is presently based on the use of three or more cesium ovens, which operate simultaneously and are controlled remotely. However, use of multiple Cs ovens simultaneously is likely to pose difficulties in operation and maintenance of the ovens. An alternate method of Cs delivery, based on a single oven distribution system is proposed as one which could reduce the need of simultaneous operation of many ovens. A proof of principle experiment verifying the concept of a multinozzle distributor based Cs oven has been carried out atmore » Institute for Plasma Research. It is also observed that the Cs flux is not controlled by Cs reservoir temperature after few hours of operation but by the temperature of the distributor which starts behaving as a Cs reservoir.« less

Retrofit device to improve vapor compression cooling system performance by dynamic blower speed modulation

DOEpatents

Roth, Robert Paul; Hahn, David C.; Scaringe, Robert P.

2015-12-08

A device and method are provided to improve performance of a vapor compression system using a retrofittable control board to start up the vapor compression system with the evaporator blower initially set to a high speed. A baseline evaporator operating temperature with the evaporator blower operating at the high speed is recorded, and then the device detects if a predetermined acceptable change in evaporator temperature has occurred. The evaporator blower speed is reduced from the initially set high speed as long as there is only a negligible change in the measured evaporator temperature and therefore a negligible difference in the compressor's power consumption so as to obtain a net increase in the Coefficient of Performance.

A perspective on the range of gasoline compression ignition combustion strategies for high engine efficiency and low NOx and soot emissions: Effects of in-cylinder fuel stratification

DOE PAGES

Dempsey, Adam B.; Curran, Scott J.; Wagner, Robert M.

2016-01-14

Many research studies have shown that low temperature combustion in compression ignition engines has the ability to yield ultra-low NOx and soot emissions while maintaining high thermal efficiency. To achieve low temperature combustion, sufficient mixing time between the fuel and air in a globally dilute environment is required, thereby avoiding fuel-rich regions and reducing peak combustion temperatures, which significantly reduces soot and NOx formation, respectively. It has been demonstrated that achieving low temperature combustion with diesel fuel over a wide range of conditions is difficult because of its properties, namely, low volatility and high chemical reactivity. On the contrary, gasolinemore » has a high volatility and low chemical reactivity, meaning it is easier to achieve the amount of premixing time required prior to autoignition to achieve low temperature combustion. In order to achieve low temperature combustion while meeting other constraints, such as low pressure rise rates and maintaining control over the timing of combustion, in-cylinder fuel stratification has been widely investigated for gasoline low temperature combustion engines. The level of fuel stratification is, in reality, a continuum ranging from fully premixed (i.e. homogeneous charge of fuel and air) to heavily stratified, heterogeneous operation, such as diesel combustion. However, to illustrate the impact of fuel stratification on gasoline compression ignition, the authors have identified three representative operating strategies: partial, moderate, and heavy fuel stratification. Thus, this article provides an overview and perspective of the current research efforts to develop engine operating strategies for achieving gasoline low temperature combustion in a compression ignition engine via fuel stratification. In this paper, computational fluid dynamics modeling of the in-cylinder processes during the closed valve portion of the cycle was used to illustrate the opportunities and challenges associated with the various fuel stratification levels.« less

A perspective on the range of gasoline compression ignition combustion strategies for high engine efficiency and low NOx and soot emissions: Effects of in-cylinder fuel stratification

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dempsey, Adam B.; Curran, Scott J.; Wagner, Robert M.

Many research studies have shown that low temperature combustion in compression ignition engines has the ability to yield ultra-low NOx and soot emissions while maintaining high thermal efficiency. To achieve low temperature combustion, sufficient mixing time between the fuel and air in a globally dilute environment is required, thereby avoiding fuel-rich regions and reducing peak combustion temperatures, which significantly reduces soot and NOx formation, respectively. It has been demonstrated that achieving low temperature combustion with diesel fuel over a wide range of conditions is difficult because of its properties, namely, low volatility and high chemical reactivity. On the contrary, gasolinemore » has a high volatility and low chemical reactivity, meaning it is easier to achieve the amount of premixing time required prior to autoignition to achieve low temperature combustion. In order to achieve low temperature combustion while meeting other constraints, such as low pressure rise rates and maintaining control over the timing of combustion, in-cylinder fuel stratification has been widely investigated for gasoline low temperature combustion engines. The level of fuel stratification is, in reality, a continuum ranging from fully premixed (i.e. homogeneous charge of fuel and air) to heavily stratified, heterogeneous operation, such as diesel combustion. However, to illustrate the impact of fuel stratification on gasoline compression ignition, the authors have identified three representative operating strategies: partial, moderate, and heavy fuel stratification. Thus, this article provides an overview and perspective of the current research efforts to develop engine operating strategies for achieving gasoline low temperature combustion in a compression ignition engine via fuel stratification. In this paper, computational fluid dynamics modeling of the in-cylinder processes during the closed valve portion of the cycle was used to illustrate the opportunities and challenges associated with the various fuel stratification levels.« less

Oxygen Generation from Carbon Dioxide for Advanced Life Support

NASA Technical Reports Server (NTRS)

Bishop, s. R.; Duncan, K. L.; Hagelin-Weaver, H. E.; Neal, L.; Paul, H. L.; Wachsman, E. D.

2007-01-01

The partial electrochemical reduction of CO2 using ceramic oxygen generators (COGs) is well known and has been studied. Conventional COGs use yttria-stabilized zirconia (YSZ) electrolytes and operate at temperatures greater than 700 C (1, 2). Operating at a lower temperature has the advantage of reducing the mass of the ancillary components such as insulation. Moreover, complete reduction of metabolically produced CO2 (into carbon and oxygen) has the potential of reducing oxygen storage weight if the oxygen can be recovered. Recently, the University of Florida developed ceramic oxygen generators employing a bilayer electrolyte of gadolinia-doped ceria and erbia-stabilized bismuth oxide (ESB) for NASA s future exploration of Mars (3). The results showed that oxygen could be reliably produced from CO2 at temperatures as low as 400 C. These results indicate that this technology could be adapted to CO2 removal from a spacesuit and other applications in which CO2 removal is an issue. This strategy for CO2 removal in advanced life support systems employs a catalytic layer combined with a COG so that the CO2 is reduced completely to solid carbon and oxygen. First, to reduce the COG operating temperature, a thin, bilayer electrolyte was employed. Second, to promote full CO2 reduction while avoiding the problem of carbon deposition on the COG cathode, a catalytic carbon deposition layer was designed and the cathode utilized materials shown to be coke resistant. Third, a composite anode was used consisting of bismuth ruthenate (BRO) and ESB that has been shown to have high performance (4). The inset of figure 1 shows the conceptual design of the tubular COG and the rest of the figure shows schematically the test apparatus. Figure 2 shows the microstructure of a COG tube prior to testing. During testing, current is applied across the cell and initially CuO is reduced to copper metal by electrochemical pumping. Then the oxygen source becomes the CO/CO2. This presentation details the results of testing the COG.

Green Chemistry Challenge: 2017 Small Business Award

EPA Pesticide Factsheets

Green Chemistry Challenge 2017 award winner, UniEnergy,improved a vanadium redox flow battery to double the energy density, have a broader operating temperature range, a smaller footprint, reduced chemical usage, and very little capacity degradation.

Mechanical behavior and modelisation of Ti-6Al-4V titanium sheet under hot stamping conditions

NASA Astrophysics Data System (ADS)

Sirvin, Q.; Velay, V.; Bonnaire, R.; Penazzi, L.

2017-10-01

The Ti-6Al-4V titanium alloy is widely used for the manufacture of aeronautical and automotive parts (solid parts). In aeronautics, this alloy is employed for its excellent mechanical behavior associated with low density, outstanding corrosion resistance and good mechanical properties up to 600°C. It is especially used for the manufacture of fuselage frames, on the pylon for carrying out the primary structure (machining forged blocks) and the secondary structure in sheet form. In this last case, the sheet metal forming can be done through various methods: at room temperature by drawing operation, at very high temperature (≃900°C) by superplastic forming (SPF) and at intermediate temperature (≥750°C) by hot forming (HF). In order to reduce production costs and environmental troubles, the cycle times reduction associated with a decrease of temperature levels are relevant. This study focuses on the behavior modelling of Ti-6Al-4V alloy at temperatures above room temperature to obtained greater formability and below SPF condition to reduce tools workshop and energy costs. The displacement field measurement obtained by Digital Image Correlation (DIC) is based on innovative surface preparation pattern adapted to high temperature exposures. Different material parameters are identified to define a model able to predict the mechanical behavior of Ti-6Al-4V alloy under hot stamping conditions. The hardening plastic model identified is introduced in FEM to simulate an omega shape forming operation.

A Compact, Continuous Adiabatic Demagnetization Refrigerator with High Heat Sink Temperature

NASA Technical Reports Server (NTRS)

Shirron, P. J.; Canavan, E. R.; DiPirro, M. J.; Jackson, M.; Tuttle, J. G.

2003-01-01

In the continuous adiabatic demagnetization refrigerator (ADR), the existence of a constant temperature stage attached to the load breaks the link between the requirements of the load (usually a detector array) and the operation of the ADR. This allows the ADR to be cycled much faster, which yields more than an order of magnitude improvement in cooling power density over single-shot ADRs. Recent effort has focused on developing compact, efficient higher temperature stages. An important part of this work has been the development of passive gas-gap heat switches that transition (from conductive to insulating) at temperatures around 1 K and 4 K without the use of an actively heated getter. We have found that by carefully adjusting available surface area and the number of He-3 monolayers, gas-gap switches can be made to operate passively. Passive operation greatly reduces switching time and eliminates an important parasitic heat load. The current four stage ADR provides 6 micro W of cooling at 50 mK (21 micro W at 100 mK) and weighs less than 8 kg. It operates from a 4.2 K heat sink, which can be provided by an unpumped He bath or many commercially available mechanical cryocoolers. Reduction in critical current with temperature in our fourth stage NbTi magnet presently limits the maximum temperature of our system to approx. 5 K. We are developing compact, low-current Nb3Sn magnets that will raise the maximum heat sink temperature to over 10 K.

Utility of NCEP Operational and Emerging Meteorological Models for Driving Air Quality Prediction

NASA Astrophysics Data System (ADS)

McQueen, J.; Huang, J.; Huang, H. C.; Shafran, P.; Lee, P.; Pan, L.; Sleinkofer, A. M.; Stajner, I.; Upadhayay, S.; Tallapragada, V.

2017-12-01

Operational air quality predictions for the United States (U. S.) are provided at NOAA by the National Air Quality Forecasting Capability (NAQFC). NAQFC provides nationwide operational predictions of ozone and particulate matter twice per day (at 06 and 12 UTC cycles) at 12 km resolution and 1 hour time intervals through 48 hours and distributed at http://airquality.weather.gov. The NOAA National Centers for Environmental Prediction (NCEP) operational North American Mesoscale (NAM) 12 km weather prediction is used to drive the Community Multiscale Air Quality (CMAQ) model. In 2017, the NAM was upgraded in part to reduce a warm 2m temperature bias in Summer (V4). At the same time CMAQ was updated to V5.0.2. Both versions of the models were run in parallel for several months. Therefore the impact of improvements from the atmospheric chemistry model versus upgrades with the weather prediction model could be assessed. . Improvements to CMAQ were related to improvements to improvements in NAM 2 m temperature bias through increasing the opacity of clouds and reducing downward shortwave radiation resulted in reduced ozone photolysis. Higher resolution operational NWP models have recently been introduced as part of the NCEP modeling suite. These include the NAM CONUS Nest (3 km horizontal resolution) run four times per day through 60 hours and the High Resolution Rapid Refresh (HRRR, 3 km) run hourly out to 18 hours. In addition, NCEP with other NOAA labs has begun to develop and test the Next Generation Global Prediction System (NGGPS) based on the FV3 global model. This presentation also overviews recent developments with operational numerical weather prediction and evaluates the ability of these models for predicting low level temperatures, clouds and capturing boundary layer processes important for driving air quality prediction in complex terrain. The assessed meteorological model errors could help determine the magnitude of possible pollutant errors from CMAQ if used for driving meteorology. The NWP models will be evaluated against standard and mesonet fields averaged for various regions during the summer 2017. An evaluation of meteorological fields important to air quality modeling (eg: near surface winds, temperatures, moisture and boundary layer heights, cloud cover) will be reported on.

Thermal Analysis of LED Phosphor Layer

NASA Astrophysics Data System (ADS)

Perera, Ukwatte Lokuliyanage Indika Upendra

Solid-state lighting technology has progressed to a level where light-emitting diode (LED) products are either on par or better than their traditional lighting technology counterparts with respect to efficacy and lifetime. At present, the most common method to create "white" light from LEDs for illumination applications is by using the LED primary radiation and wavelength-converting materials. In this method, the re-emission from the wavelength-converting materials excited by the LED primary radiation is combined with the LED primary radiation to create the "white" light. During this conversion process, heat is generated as a result of conversion inefficiencies and other loss mechanisms in the LED and the wavelength-converting materials. This generated heat, if not properly dissipated, increases the operating temperature, thereby increasing the light output degradation of the system over both the short and long term. The heat generation of the LED and thermal management of the LED have been studied extensively. Methods to effectively dissipate heat from the LEDs and maintain lower LED operating temperature are well understood. However, investigation of factors driving heat generation, the resulting temperature distribution in the phosphor layer, and the influence of the phosphor layer temperature on LED performance and reliability have not received the same focus. The goal of this dissertation was to understand the main factors driving heat and light generation and the transport of light and heat in the wavelength-converting layer of an LED system. Another goal was to understand the interaction between heat and light in the system and to develop and analyze a solution to reduce the wavelength-converting layer operating temperature, thereby improving light output and reliability. Even though past studies have explored generation and transfer separately for light and heat, to the best of the author's knowledge, this is the first study that has analyzed both factors simultaneously to optimize the performance of a phosphor-converted LED system, thus contributing new knowledge to the field. In this dissertation, a theoretical model was developed that modeled both light propagation and heat transfer in the wavelength-converting layer for identifying the factors influencing heat generation. This theoretical model included temperature-dependent phosphor efficiency and light absorption in the phosphor layer geometry. Experimental studies were used to validate the developed model. The model indicated good agreement with the experimental results. The developed theoretical model was then used to model experimental studies. These experiment results were compared with the model predicted results for total radiant power output of LED systems and phosphor layer surface temperature. These comparisons illustrated the effectiveness of a dedicated heat dissipation method in reducing the operating temperature of the wavelength-converting layer, and the contribution of different heat dissipation mechanisms were quantified using the developed numerical model. In addition to these short-term studies, an experiment was conducted to validate the effectiveness of the dedicated wavelength-converting heat sink design to improve system lifetime by reducing phosphor layer operating temperature. The proposed heat sink design decreased the operating temperature of the phosphor layer by ~10°C, improving lifetime by twofold. Finally, this dissertation investigated the potential of the developed theoretical model being used as a tool for prioritizing research tasks and as a design tool during the material selection and system configuration phases.

Regenerative air heater

DOEpatents

Hasselquist, P.B.; Baldner, R.

1980-11-26

A gas-cooled steel skirt is used to support a refractory cored brick matrix and dome structure in a high temperature regenerative air heater useful in magnetohydrodynamic power generation. The steel skirt thermally expands to accommodate the thermal expansion of the dome structure despite substantial temperature differential thereby reducing relative movement between the dome bricks. Gas cooling of the steel skirt allows the structure to operate above its normal temperature during clean-out cycles and also allows for the control of the thermal expansion of the steel skirt.

Regenerative air heater

DOEpatents

Hasselquist, Paul B.; Baldner, Richard

1982-01-01

A gas-cooled steel skirt is used to support a refractory cored brick matrix and dome structure in a high temperature regenerative air heater useful in magnetohydrodynamic power generation. The steel skirt thermally expands to accommodate the thermal expansion of the dome structure despite substantial temperature differential thereby reducing relative movement between the dome bricks. Gas cooling of the steel skirt allows the structure to operate above its normal temperature during clean-out cycles and also allows for the control of the thermal expansion of the steel skirt.

Improved Performance in Mammalian Cell Perfusion Cultures by Growth Inhibition.

PubMed

Wolf, Moritz K F; Closet, Aurélie; Bzowska, Monika; Bielser, Jean-Marc; Souquet, Jonathan; Broly, Hervé; Morbidelli, Massimo

2018-05-21

Mammalian cell perfusion cultures represent a promising alternative to the current fed-batch technology for the production of various biopharmaceuticals. Long-term operation at a fixed viable cell density (VCD) requires a viable culture and a constant removal of excessive cells. Product loss in the cell removing bleed stream deteriorates the process yield. In this study, the authors investigate the use of chemical and environmental growth inhibition on culture performance by either adding valeric acid (VA) to the production media or by reducing the culture temperature (33.0 °C) with respect to control conditions (36.5 °C, no VA). Low temperature significantly reduces cellular growth, thus, resulting in lower bleed rates accompanied by a reduced product loss of 11% compared to 26% under control conditions. Additionally, the cell specific productivity of the target protein improves and maintained stable leading to media savings per mass of product. VA shows initially an inhibitory effect on cellular growth. However, cells seemed to adapt to the presence of the inhibitor resulting in a recovery of the cellular growth. Cell cycle and Western blot analyses support the observed results. This work underlines the role of temperature as a key operating variable for the optimization of perfusion cultures. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cost-effective retrofit technology for reducing peak power demand in small and medium commercial buildings

DOE PAGES

Nutaro, James J.; Fugate, David L.; Kuruganti, Teja; ...

2015-05-27

We describe a cost-effective retrofit technology that uses collective control of multiple rooftop air conditioning units to reduce the peak power consumption of small and medium commercial buildings. The proposed control uses a model of the building and air conditioning units to select an operating schedule for the air conditioning units that maintains a temperature set point subject to a constraint on the number of units that may operate simultaneously. A prototype of this new control system was built and deployed in a large gymnasium to coordinate four rooftop air conditioning units. Based on data collected while operating this prototype,more » we estimate that the cost savings achieved by reducing peak power consumption is sufficient to repay the cost of the prototype within a year.« less

Sulfidogenic fluidized-bed treatment of metal-containing wastewater at low and high temperatures.

PubMed

Sahinkaya, Erkan; Ozkaya, Bestamin; Kaksonen, Anna H; Puhakka, Jaakko A

2007-04-15

The applicability of a fluidized-bed reactor (FBR)-based sulfate reducing bioprocess was investigated for the treatment of iron-containing (40-90 mg/L) acidic wastewater at low (8 degrees C) and high (65 degrees C) temperatures. The FBRs operated at low and high temperatures were inoculated with cultures of sulfate-reducing bacteria (SRB) originally enriched from arctic and hot mining environments, respectively. Ethanol was supplemented as carbon and electron source for SRB. At 8 degrees C, ethanol oxidation and sulfate reduction rates increased steadily and reached 320 and 265 mg/L.day, respectively, after 1 month of operation. After this point, the rates did not change significantly during 130 days of operation. Despite the complete ethanol oxidation and iron precipitation, the average sulfate reduction efficiency was 35 +/- 4% between days 30 and 130 due to the accumulation of acetate. At 65 degrees C, a rapid startup was observed as 99.9, 46, and 29% ethanol, sulfate, acetate removals, in respective order, were observed after 6 days. The feed pH was decreased gradually from its initial value of 6 to around 3.7 during 100 days of operation. The wastewater pH of 4.3-4.4 was neutralized by the alkalinity produced in acetate oxidation and the average effluent pH was 7.8 +/- 0.8. As in the low temperature FBR, acetate accumulated. Hence, the oxidation of acetate is the rate-limiting step in the sulfidogenic ethanol oxidation by thermophilic and psychrotrophic SRB. The sulfate reduction rate is three times and acetate oxidation rate is four times higher at 65 degrees C than at 8 degrees C. (c) 2006 Wiley Periodicals, Inc.

Thermal Modeling and Management of Solid Oxide Fuel Cells Operating with Internally Reformed Methane

NASA Astrophysics Data System (ADS)

Wu, Yiyang; Shi, Yixiang; Cai, Ningsheng; Ni, Meng

2018-06-01

A detailed three-dimensional mechanistic model of a large-scale solid oxide fuel cell (SOFC) unit running on partially pre-reformed methane is developed. The model considers the coupling effects of chemical and electrochemical reactions, mass transport, momentum and heat transfer in the SOFC unit. After model validation, parametric simulations are conducted to investigate how the methane pre-reforming ratio affects the transport and electrochemistry of the SOFC unit. It is found that the methane steam reforming reaction has a "smoothing effect", which can achieve more uniform distributions of gas compositions, current density and temperature among the cell plane. In the case of 1500 W/m2 power density output, adding 20% methane absorbs 50% of internal heat production inside the cell, reduces the maximum temperature difference inside the cell from 70 K to 22 K and reduces the cathode air supply by 75%, compared to the condition of completely pre-reforming of methane. Under specific operating conditions, the pre-reforming ratio of methane has an optimal range for obtaining a good temperature distribution and good cell performance.

Do Assimilated Drifter Velocities Improve Lagrangian Predictability in an Operational Ocean Model?

DTIC Science & Technology

2015-05-01

extended Kalman filter . Molcard et al. (2005) used a statistical method to cor- relate model and drifter velocities. Taillandier et al. (2006) describe the... temperature and salinity observations. Trajectory angular differ- ences are also reduced. 1. Introduction The importance of Lagrangian forecasts was seen... Temperature , salinity, and sea surface height (SSH, measured along-track by satellite altimeters) observa- tions are typically assimilated in

Method for reducing nitrogen oxides in combustion effluents

DOEpatents

Zauderer, Bert

2000-01-01

Method for reducing nitrogen oxides (NO.sub.x) in the gas stream from the combustion of fossil fuels is disclosed. In a narrow gas temperature zone, NO.sub.x is converted to nitrogen by reaction with urea or ammonia with negligible remaining ammonia and other reaction pollutants. Specially designed injectors are used to introduce air atomized water droplets containing dissolved urea or ammonia into the gaseous combustion products in a manner that widely disperses the droplets exclusively in the optimum reaction temperature zone. The injector operates in a manner that forms droplet of a size that results in their vaporization exclusively in this optimum NO.sub.x -urea/ammonia reaction temperature zone. Also disclosed is a design of a system to effectively accomplish this injection.

Evaluation of a Programmable Voltage-Controlled MEMS Oscillator, Type SiT3701, Over a Wide Temperature Range

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Semiconductor chips based on MEMS (Micro-Electro-Mechanical Systems) technology, such as sensors, transducers, and actuators, are becoming widely used in today s electronics due to their high performance, low power consumption, tolerance to shock and vibration, and immunity to electro-static discharge. In addition, the MEMS fabrication process allows for the miniaturization of individual chips as well as the integration of various electronic circuits into one module, such as system-on-a-chip. These measures would simplify overall system design, reduce parts count and interface, improve reliability, and reduce cost; and they would meet requirements of systems destined for use in space exploration missions. In this work, the performance of a recently-developed MEMS voltage-controlled oscillator was evaluated under a wide temperature range. Operation of this new commercial-off-the-shelf (COTS) device was also assessed under thermal cycling to address some operational conditions of the space environment

Firefly: A HOT camera core for thermal imagers with enhanced functionality

NASA Astrophysics Data System (ADS)

Pillans, Luke; Harmer, Jack; Edwards, Tim

2015-06-01

Raising the operating temperature of mercury cadmium telluride infrared detectors from 80K to above 160K creates new applications for high performance infrared imagers by vastly reducing the size, weight and power consumption of the integrated cryogenic cooler. Realizing the benefits of Higher Operating Temperature (HOT) requires a new kind of infrared camera core with the flexibility to address emerging applications in handheld, weapon mounted and UAV markets. This paper discusses the Firefly core developed to address these needs by Selex ES in Southampton UK. Firefly represents a fundamental redesign of the infrared signal chain reducing power consumption and providing compatibility with low cost, low power Commercial Off-The-Shelf (COTS) computing technology. This paper describes key innovations in this signal chain: a ROIC purpose built to minimize power consumption in the proximity electronics, GPU based image processing of infrared video, and a software customisable infrared core which can communicate wirelessly with other Battlespace systems.

Flight evaluation of an extended engine life mode on an F-15 airplane

NASA Technical Reports Server (NTRS)

Myers, Lawrence P.; Conners, Timothy R.

1992-01-01

An integrated flight and propulsion control system designed to reduce the rate of engine deterioration was developed and evaluated in flight on the NASA Dryden F-15 research aircraft. The extended engine life mode increases engine pressure ratio while reducing engine airflow to lower the turbine temperature at constant thrust. The engine pressure ratio uptrim is modulated in real time based on airplane maneuver requirements, flight conditions, and engine information. The extended engine life mode logic performed well, significantly reducing turbine operating temperature. Reductions in fan turbine inlet temperature of up to 80 F were obtained at intermediate power and up to 170 F at maximum augmented power with no appreciable loss in thrust. A secondary benefit was the considerable reduction in thrust-specific fuel consumption. The success of the extended engine life mode is one example of the advantages gained from integrating aircraft flight and propulsion control systems.

Autonomous Aerobraking Using Thermal Response Surface Analysis

NASA Technical Reports Server (NTRS)

Prince, Jill L.; Dec, John A.; Tolson, Robert H.

2007-01-01

Aerobraking is a proven method of significantly increasing the science payload that can be placed into low Mars orbits when compared to an all propulsive capture. However, the aerobraking phase is long and has mission cost and risk implications. The main cost benefit is that aerobraking permits the use of a smaller and cheaper launch vehicle, but additional operational costs are incurred during the long aerobraking phase. Risk is increased due to the repeated thermal loading of spacecraft components and the multiple attitude and propulsive maneuvers required for successful aerobraking. Both the cost and risk burdens can be significantly reduced by automating the aerobraking operations phase. All of the previous Mars orbiter missions that have utilized aerobraking have increasingly relied on onboard calculations during aerobraking. Even though the temperature of spacecraft components has been the limiting factor, operational methods have relied on using a surrogate variable for mission control. This paper describes several methods, based directly on spacecraft component maximum temperature, for autonomously predicting the subsequent aerobraking orbits and prescribing apoapsis propulsive maneuvers to maintain the spacecraft within specified temperature limits. Specifically, this paper describes the use of thermal response surface analysis in predicting the temperature of the spacecraft components and the corresponding uncertainty in this temperature prediction.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Zhixiao; Mukherjee, Partha P.

We report the cathode surface passivation caused by Li 2S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li 2S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li 2S film on carbon cathode surface. Li 2S film growth experiences nucleation, isolated Li 2S island growth and island coalescence. The slow adsorption rate at small S 2- concentration inhibits the formation of nucleation seeds and the lateral growth of Limore » 2S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li 2S nucleation seeds form in such an operating temperature range, which facilitates heterogeneous growth and thereby inhibits the lateral growth of the Li 2S film, which may also result in reduced surface passivation. Finally, the high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.« less

Hot piston ring tests

NASA Technical Reports Server (NTRS)

Allen, David J.; Tomazic, William A.

1987-01-01

As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

Mesoscale Elucidation of Surface Passivation in the Li-Sulfur Battery Cathode.

PubMed

Liu, Zhixiao; Mukherjee, Partha P

2017-02-15

The cathode surface passivation caused by Li 2 S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li 2 S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li 2 S film on carbon cathode surface. Li 2 S film growth experiences nucleation, isolated Li 2 S island growth and island coalescence. The slow adsorption rate at small S 2- concentration inhibits the formation of nucleation seeds and the lateral growth of Li 2 S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li 2 S nucleation seeds form in such an operating temperature range, thereby facilitating heterogeneous growth and potentially inhibiting the lateral growth of the Li 2 S film, which may ultimately result in reduced surface passivation. The high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.

Analysis of photovoltaic with water pump cooling by using ANSYS

NASA Astrophysics Data System (ADS)

Syafiqah, Z.; Amin, N. A. M.; Irwan, Y. M.; Shobry, M. Z.; Majid, M. S. A.

2017-10-01

Almost all regions in the world are facing with problem of increasing electricity cost from time to time. Besides, with the mankind’s anxiety about global warming, it has infused an ideology to rapidly move towards renewable energy sources since it is believed to be more reliable and safer. One example of the best alternatives to replace the fossil fuels sourced is solar energy. Photovoltaic (PV) panel is used to convert the sunlight into electricity. Unfortunately, the performance of PV panel can be affected by its operating temperature. With the increment of ambient temperature, the PV panel operating temperature also increase and will affect the performance of PV panel (in terms of power generated). With this concern, a water cooling system was installed on top of PV panel to help reduce the PV panel’s temperature. Five different water mass flow rate is tested due to investigate their impact towards the thermal performance and heat transfer rate.

A fully electric field driven scalable magnetoelectric switching element

NASA Astrophysics Data System (ADS)

Ahmed, R.; Victora, R. H.

2018-04-01

A technique for micromagnetic simulation of the magnetoelectric (ME) effect in Cr2O3 based structures has been developed. It has been observed that the microscopic ME susceptibility differs significantly from the experimentally measured values. The deviation between the two susceptibilities becomes more prominent near the Curie temperature, affecting the operation of the device at room temperature. A fully electric field controlled ME switching element has been proposed for use at technologically interesting densities: it employs quantum mechanical exchange at the boundaries instead of the applied magnetic field needed in traditional switching schemes. After establishing temperature dependent physics-based parameters, switching performances have been studied for different temperatures, applied electric fields, and Cr2O3 cross-sections. It has been found that our proposed use of quantum mechanical exchange favors reduced electric field operation and enhanced scalability while retaining reliable thermal stability.

Process for CO.sub.2 capture using zeolites from high pressure and moderate temperature gas streams

DOEpatents

Siriwardane, Ranjani V [Morgantown, WV; Stevens, Robert W [Morgantown, WV

2012-03-06

A method for separating CO.sub.2 from a gas stream comprised of CO.sub.2 and other gaseous constituents using a zeolite sorbent in a swing-adsorption process, producing a high temperature CO.sub.2 stream at a higher CO.sub.2 pressure than the input gas stream. The method utilizes CO.sub.2 desorption in a CO.sub.2 atmosphere and effectively integrates heat transfers for optimizes overall efficiency. H.sub.2O adsorption does not preclude effective operation of the sorbent. The cycle may be incorporated in an IGCC for efficient pre-combustion CO.sub.2 capture. A particular application operates on shifted syngas at a temperature exceeding 200.degree. C. and produces a dry CO.sub.2 stream at low temperature and high CO.sub.2 pressure, greatly reducing any compression energy requirements which may be subsequently required.

Effects of radiation and temperature on gallium nitride (GaN) metal-semiconductor-metal ultraviolet photodetectors

NASA Astrophysics Data System (ADS)

Chiamori, Heather C.; Angadi, Chetan; Suria, Ateeq; Shankar, Ashwin; Hou, Minmin; Bhattacharya, Sharmila; Senesky, Debbie G.

2014-06-01

The development of radiation-hardened, temperature-tolerant materials, sensors and electronics will enable lightweight space sub-systems (reduced packaging requirements) with increased operation lifetimes in extreme harsh environments such as those encountered during space exploration. Gallium nitride (GaN) is a ceramic, semiconductor material stable within high-radiation, high-temperature and chemically corrosive environments due to its wide bandgap (3.4 eV). These material properties can be leveraged for ultraviolet (UV) wavelength photodetection. In this paper, current results of GaN metal-semiconductor-metal (MSM) UV photodetectors behavior after irradiation up to 50 krad and temperatures of 15°C to 150°C is presented. These initial results indicate that GaN-based sensors can provide robust operation within extreme harsh environments. Future directions for GaN-based photodetector technology for down-hole, automotive and space exploration applications are also discussed.

Increasing Operational Stability in Low NOX GT Combustor Using Fuel Rich Concentric Pilot Combustor

NASA Astrophysics Data System (ADS)

Levy, Yeshayahou; Erenburg, Vladimir; Sherbaum, Valery; Ovcharenko, Vitali; Rosentsvit, Leonid; Chudnovsky, Boris; Herszage, Amiel; Talanker, Alexander

2012-03-01

Lean combustion is a method in which combustion takes place under low equivalence ratio and relatively low combustion temperatures. As such, it has the potential to lower the effect of the relatively high activation energy nitrogen-oxygen reactions which are responsible for substantial NOX formation during combustion processes. However, lowering temperature reduces the reaction rate and deteriorates combustion stability. The objective of the present study is to reduce the lower equivalence ratio limit of the stable combustion operational boundary in lean Gas Turbine (GT) combustors while still maintaining combustion stability. A lean premixed gaseous combustor was equipped with a surrounding concentric pilot flame operating under rich conditions, thus generating a hot stream of combustion products with significant amount of reactive radicals. The main combustor's fuel-air composition was varied from stoichiometric to lean mixtures. The pilot's mixture composition was also varied by changing the air flow rate, within a limited rich mixtures range. The pilot fuel flow rate was always lower than five percent of the total fuel supply at the specific stage of the experiments.

Fluidized-bed technology enabling the integration of high temperature solar receiver CSP systems with steam and advanced power cycles

DOE PAGES

Sakadjian, B.; Hu, S.; Maryamchik, M.; ...

2015-06-05

Solar Particle Receivers (SPR) are under development to drive concentrating solar plants (CSP) towards higher operating temperatures to support higher efficiency power conversion cycles. The novel high temperature SPR-based CSP system uses solid particles as the heat transfer medium (HTM) in place of the more conventional fluids such as molten salt or steam used in current state-of-the-art CSP plants. The solar particle receiver (SPR) is designed to heat the HTM to temperatures of 800 °C or higher which is well above the operating temperatures of nitrate-based molten salt thermal energy storage (TES) systems. The solid particles also help overcome somemore » of the other challenges associated with molten salt-based systems such as freezing, instability and degradation. The higher operating temperatures and use of low cost HTM and higher efficiency power cycles are geared towards reducing costs associated with CSP systems. This paper describes the SPR-based CSP system with a focus on the fluidized-bed (FB) heat exchanger and its integration with various power cycles. Furthermore, the SPR technology provides a potential pathway to achieving the levelized cost of electricity (LCOE) target of $0.06/kWh that has been set by the U.S. Department of Energy's SunShot initiative.« less

Fluidized-bed technology enabling the integration of high temperature solar receiver CSP systems with steam and advanced power cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakadjian, B.; Hu, S.; Maryamchik, M.

Solar Particle Receivers (SPR) are under development to drive concentrating solar plants (CSP) towards higher operating temperatures to support higher efficiency power conversion cycles. The novel high temperature SPR-based CSP system uses solid particles as the heat transfer medium (HTM) in place of the more conventional fluids such as molten salt or steam used in current state-of-the-art CSP plants. The solar particle receiver (SPR) is designed to heat the HTM to temperatures of 800 °C or higher which is well above the operating temperatures of nitrate-based molten salt thermal energy storage (TES) systems. The solid particles also help overcome somemore » of the other challenges associated with molten salt-based systems such as freezing, instability and degradation. The higher operating temperatures and use of low cost HTM and higher efficiency power cycles are geared towards reducing costs associated with CSP systems. This paper describes the SPR-based CSP system with a focus on the fluidized-bed (FB) heat exchanger and its integration with various power cycles. Furthermore, the SPR technology provides a potential pathway to achieving the levelized cost of electricity (LCOE) target of $0.06/kWh that has been set by the U.S. Department of Energy's SunShot initiative.« less

Probing Temperature Inside Planar SOFC Short Stack, Modules, and Stack Series

NASA Astrophysics Data System (ADS)

Yu, Rong; Guan, Wanbing; Zhou, Xiao-Dong

2017-02-01

Probing temperature inside a solid oxide fuel cell (SOFC) stack lies at the heart of the development of high-performance and stable SOFC systems. In this article, we report our recent work on the direct measurements of the temperature in three types of SOFC systems: a 5-cell short stack, a 30-cell stack module, and a stack series consisting of two 30-cell stack modules. The dependence of temperature on the gas flow rate and current density was studied under a current sweep or steady-state operation. During the current sweep, the temperature inside the 5-cell stack decreased with increasing current, while it increased significantly at the bottom and top of the 30-cell stack. During a steady-state operation, the temperature of the 5-cell stack was stable while it was increased in the 30-cell stack. In the stack series, the maximum temperature gradient reached 190°C when the gas was not preheated. If the gas was preheated and the temperature gradient was reduced to 23°C in the stack series with the presence of a preheating gas and segmented temperature control, this resulted in a low degradation rate.

Performance of an SOI Boot-Strapped Full-Bridge MOSFET Driver, Type CHT-FBDR, under Extreme Temperatures

NASA Technical Reports Server (NTRS)

Patterson, Richard; Hammoud, Ahmad

2009-01-01

Electronic systems designed for use in deep space and planetary exploration missions are expected to encounter extreme temperatures and wide thermal swings. Silicon-based devices are limited in their wide-temperature capability and usually require extra measures, such as cooling or heating mechanisms, to provide adequate ambient temperature for proper operation. Silicon-On-Insulator (SOI) technology, on the other hand, lately has been gaining wide spread use in applications where high temperatures are encountered. Due to their inherent design, SOI-based integrated circuit chips are able to operate at temperatures higher than those of the silicon devices by virtue of reducing leakage currents, eliminating parasitic junctions, and limiting internal heating. In addition, SOI devices provide faster switching, consume less power, and offer improved radiation-tolerance. Very little data, however, exist on the performance of such devices and circuits under cryogenic temperatures. In this work, the performance of an SOI bootstrapped, full-bridge driver integrated circuit was evaluated under extreme temperatures and thermal cycling. The investigations were carried out to establish a baseline on the functionality and to determine suitability of this device for use in space exploration missions under extreme temperature conditions.

Development of thermal actuators with multi-locking positions

NASA Astrophysics Data System (ADS)

Luo, J. K.; Zhu, Y.; Fu, Y. Q.; Flewitt, A. J.; Spearing, S. M.; Miao, J. M.; Milne, W. I.

2006-04-01

To reduce power consumption and operation temperature for micro-thermal actuators, metal-based micro-mechanical locks with multi-locking positions were analyzed and fabricated. The micro-locks consist of two or three U-shaped thermal actuators. The devices were made by a single mask process using electroplated Ni as the active material. Tests showed that the metal based thermal actuators deliver a maximum displacement of ~20µm at a much lower temperature than that of Si-based actuators. However Ni-actuators showed a severe back bending, which increases with increasing applied power. The temperature to initiate the back bending is as low as ~240°C. Back bending increases the distance between the two actuators, and leads to locking function failure. For practical application, Ni-based thermal actuators must be operated below 200°C.

Hydronic Heating Retrofits for Low-Rise Multifamily Buildings: Boiler Control Replacement and Monitoring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dentz, J.; Henderson, H.; Varshney, K.

2014-09-01

The ARIES Collaborative, a U.S. Department of Energy Building America research team, partnered with NeighborWorks America affiliate Homeowners' Rehab Inc. (HRI) of Cambridge, Massachusetts, to study improvements to the central hydronic heating system in one of the nonprofit's housing developments. The heating controls in the three-building, 42-unit Columbia Cambridge Alliance for Spanish Tenants housing development were upgraded. Fuel use in the development was excessive compared to similar properties. A poorly insulated thermal envelope contributed to high energy bills, but adding wall insulation was not cost-effective or practical. The more cost-effective option was improving heating system efficiency. Efficient operation of themore » heating system faced several obstacles, including inflexible boiler controls and failed thermostatic radiator valves. Boiler controls were replaced with systems that offer temperature setbacks and one that controls heat based on apartment temperature in addition to outdoor temperature. Utility bill analysis shows that post-retrofit weather-normalized heating energy use was reduced by 10%-31% (average of 19%). Indoor temperature cutoff reduced boiler runtime (and therefore heating fuel consumption) by 28% in the one building in which it was implemented. Nearly all savings were obtained during night which had a lower indoor temperature cut off (68 degrees F) than day (73 degrees F). This implies that the outdoor reset curve was appropriately adjusted for this building for daytime operation. Nighttime setback of heating system supply water temperature had no discernable impact on boiler runtime or gas bills.« less

Touch Temperature Coating for Off-the-Shelf Electrical Equipment Used on Spacecraft

NASA Technical Reports Server (NTRS)

Ungar, Eugene K.; Brady, Timothy K.

2010-01-01

Off-the-shelf electrical equipment is frequently used in space-based applications to control costs. However, the reduced heat transfer in the spacecraft microgravity environment causes the equipment to operate at significantly higher temperatures than it would in terrestrial applications. This creates touch temperature issues where items particularly metallic ones become too hot for the crew to handle safely. A touch temperature coating layup has been developed that can be added to spacebased electrically powered hardware. The coating allows the crew to safely handle the hardware, but only slightly impedes the heat transfer from the component during normal operation. In the present work, the coating generic requirements are developed and a layup is described that meets these specifications. Analytical and experimental results are presented that demonstrate the ability of the coating layup to increase the allowable limits of touch temperature while only marginally degrading heat transfer to the environment. This allows the spacecraft crew to handle objects that, if not coated, would be hot enough to cause pain or skin damage.

Novel Concrete Temperature Monitoring Method Based on an Embedded Passive RFID Sensor Tag.

PubMed

Liu, Yongsheng; Deng, Fangming; He, Yigang; Li, Bing; Liang, Zhen; Zhou, Shuangxi

2017-06-22

This paper firstly introduces the importance of temperature control in concrete measurement, then a passive radio frequency identification (RFID) sensor tag embedded for concrete temperature monitoring is presented. In order to reduce the influences of concrete electromagnetic parameters during the drying process, a T-type antenna is proposed to measure the concrete temperature at the required depth. The proposed RFID sensor tag is based on the EPC generation-2 ultra-high frequency (UHF) communication protocol and operates in passive mode. The temperature sensor can convert the sensor signals to corresponding digital signals without an external reference clock due to the adoption of phase-locked loop (PLL)-based architecture. Laboratory experimentation and on-site testing demonstrate that our sensor tag embedded in concrete can provide reliable communication performance in passive mode. The maximum communicating distance between reader and tag is 7 m at the operating frequency of 915 MHz and the tested results show high consistency with the results tested by a thermocouple.

Quantitative analysis and temperature-induced variations of moiré pattern in fiber-coupled imaging sensors.

PubMed

Karbasi, Salman; Arianpour, Ashkan; Motamedi, Nojan; Mellette, William M; Ford, Joseph E

2015-06-10

Imaging fiber bundles can map the curved image surface formed by some high-performance lenses onto flat focal plane detectors. The relative alignment between the focal plane array pixels and the quasi-periodic fiber-bundle cores can impose an undesirable space variant moiré pattern, but this effect may be greatly reduced by flat-field calibration, provided that the local responsivity is known. Here we demonstrate a stable metric for spatial analysis of the moiré pattern strength, and use it to quantify the effect of relative sensor and fiber-bundle pitch, and that of the Bayer color filter. We measure the thermal dependence of the moiré pattern, and the achievable improvement by flat-field calibration at different operating temperatures. We show that a flat-field calibration image at a desired operating temperature can be generated using linear interpolation between white images at several fixed temperatures, comparing the final image quality with an experimentally acquired image at the same temperature.

Planar solid oxide fuel cell with staged indirect-internal air and fuel preheating and reformation

DOEpatents

Geisbrecht, Rodney A; Williams, Mark C

2003-10-21

A solid oxide fuel cell arrangement and method of use that provides internal preheating of both fuel and air in order to maintain the optimum operating temperature for the production of energy. The internal preheat passes are created by the addition of two plates, one on either side of the bipolar plate, such that these plates create additional passes through the fuel cell. This internal preheat fuel cell configuration and method reduce the requirements for external heat exchanger units and air compressors. Air or fuel may be added to the fuel cell as required to maintain the optimum operating temperature through a cathode control valve or an anode control valve, respectively. A control loop comprises a temperature sensing means within the preheat air and fuel passes, a means to compare the measured temperature to a set point temperature and a determination based on the comparison as to whether the control valves should allow additional air or fuel into the preheat or bypass manifolds of the fuel cell.

Novel Concrete Temperature Monitoring Method Based on an Embedded Passive RFID Sensor Tag

PubMed Central

Liu, Yongsheng; Deng, Fangming; He, Yigang; Li, Bing; Liang, Zhen; Zhou, Shuangxi

2017-01-01

This paper firstly introduces the importance of temperature control in concrete measurement, then a passive radio frequency identification (RFID) sensor tag embedded for concrete temperature monitoring is presented. In order to reduce the influences of concrete electromagnetic parameters during the drying process, a T-type antenna is proposed to measure the concrete temperature at the required depth. The proposed RFID sensor tag is based on the EPC generation-2 ultra-high frequency (UHF) communication protocol and operates in passive mode. The temperature sensor can convert the sensor signals to corresponding digital signals without an external reference clock due to the adoption of phase-locked loop (PLL)-based architecture. Laboratory experimentation and on-site testing demonstrate that our sensor tag embedded in concrete can provide reliable communication performance in passive mode. The maximum communicating distance between reader and tag is 7 m at the operating frequency of 915 MHz and the tested results show high consistency with the results tested by a thermocouple. PMID:28640188

Remotely Powered Reconfigurable Receiver for Extreme Environment Sensing Platforms

NASA Technical Reports Server (NTRS)

Sheldon, Douglas J.

2012-01-01

Wireless sensors connected in a local network offer revolutionary exploration capabilities, but the current solutions do not work in extreme environments of low temperatures (200K) and low to moderate radiation levels (<50 krad). These sensors (temperature, radiation, infrared, etc.) would need to operate outside the spacecraft/ lander and be totally independent of power from the spacecraft/lander. Flash memory field-programmable gate arrays (FPGAs) are being used as the main signal processing and protocol generation platform in a new receiver. Flash-based FPGAs have been shown to have at least 100 reduced standby power and 10 reduction operating power when compared to normal SRAM-based FPGA technology.

Stratospheric aerosol modification by supersonic transport operations with climate implications

NASA Technical Reports Server (NTRS)

Toon, O. B.; Turco, R. P.; Pollack, J. B.; Whitten, R. C.; Poppoff, I. G.; Hamill, P.

1980-01-01

The potential effects on stratospheric aerosois of supersonic transport emissions of sulfur dioxide gas and submicron size soot granules are estimated. An interactive particle-gas model of the stratospheric aerosol is used to compute particle changes due to exhaust emissions, and an accurate radiation transport model is used to compute the attendant surface temperature changes. It is shown that a fleet of several hundred supersonic aircraft, operating daily at 20 km, could produce about a 20% increase in the concentration of large particles in the stratosphere. Aerosol increases of this magnitude would reduce the global surface temperature by less than 0.01 K.

Transient simulation of coolant peak temperature due to prolonged fan and/or water pump operation after the vehicle is keyed-off

NASA Astrophysics Data System (ADS)

Pang, Suh Chyn; Masjuki, Haji Hassan; Kalam, Md. Abul; Hazrat, Md. Ali

2014-01-01

Automotive designers should design a robust engine cooling system which works well in both normal and severe driving conditions. When vehicles are keyed-off suddenly after some distance of hill-climbing driving, the coolant temperature tends to increase drastically. This is because heat soak in the engine could not be transferred away in a timely manner, as both the water pump and cooling fan stop working after the vehicle is keyed-off. In this research, we aimed to visualize the coolant temperature trend over time before and after the vehicles were keyed-off. In order to prevent coolant temperature from exceeding its boiling point and jeopardizing engine life, a numerical model was further tested with prolonged fan and/or water pump operation after keying-off. One dimensional thermal-fluid simulation was exploited to model the vehicle's cooling system. The behaviour of engine heat, air flow, and coolant flow over time were varied to observe the corresponding transient coolant temperatures. The robustness of this model was proven by validation with industry field test data. The numerical results provided sensible insights into the proposed solution. In short, prolonging fan operation for 500 s and prolonging both fan and water pump operation for 300 s could reduce coolant peak temperature efficiently. The physical implementation plan and benefits yielded from implementation of the electrical fan and electrical water pump are discussed.

Efficiency and Regulation of Commercial Low Power DC/DC Converter Modules at Low Temperatures

NASA Technical Reports Server (NTRS)

Elbuluk, Malik E.; Gerber, Scott; Hammoud, Ahmad; Patterson, Richard L.

2000-01-01

DC/DC converters that are capable of operating at cryogenic temperatures are anticipated to play an important role in the power systems of future NASA deep space missions. Design of these converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. At the NASA Glenn Research Center Low Temperature Electronics Laboratory, several commercial off-the-shelf dc/dc converter modules were evaluated for their low temperature performance. Various parameters were investigated as a function of temperature, in the range of 20 C to -190 C. Data pertaining to the efficiency and voltage regulation of the tested converters is presented and discussed.

Development of an Operation Control System for Photovoltaics and Electric Storage Heaters for Houses Based on Information in Weather Forecasts

NASA Astrophysics Data System (ADS)

Obara, Shin'ya

An all-electric home using an electric storage heater with safety and cleaning is expanded. However, the general electric storage heater leads to an unpleasant room temperature and energy loss by the overs and shorts of the amount of heat radiation when the climate condition changes greatly. Consequently, the operation of the electric storage heater introduced into an all-electric home, a storage type electric water heater, and photovoltaics was planned using weather forecast information distributed by a communication line. The comfortable evaluation (the difference between a room-temperature target and a room-temperature result) when the proposed system was employed based on the operation planning, purchase electric energy, and capacity of photovoltaics was investigated. As a result, comfortable heating operation was realized by using weather forecast data; furthermore, it is expected that the purchase cost of the commercial power in daytime can be reduced by introducing photovoltaics. Moreover, when the capacity of the photovoltaics was increased, the surplus power was stored in the electric storage heater, but an extremely unpleasant room temperature was not shown in the investigation ranges of this paper. By obtaining weather information from the forecast of the day from an external service using a communication line, the heating system of the all-electric home with low energy loss and comfort temperature is realizable.

Geoscience Laser Altimeter System (GLAS) Final Test Report of DM LHP TV Testing

NASA Technical Reports Server (NTRS)

Baker, Charles

2000-01-01

Two loop heat pipes (LHPs) are to be used for thermal control of the Geoscience Laser Altimeter System (GLAS), planned for flight in 2001. One LHP will be used to transport 100 W from a laser to the radiator, the other will transport 210 W from electronic boxes to the radiator. In order to verify the LHP design for the GLAS application, an LHP Development Model has been fabricated, and ambient and thermal vacuum tested. Two aluminum blocks of 15 kg and 30 kg, respectively, were attached to the LHP to simulate the thermal masses connected to the heat sources. A 20 W starter heater was installed on the evaporator to aid the loop startup. A new concept to thermally couple the vapor and liquid line was also incorporated in the LHP design. Such a thermal coupling would reduce the power requirement on the compensation chamber in order to maintain the loop set point temperature. To avoid freezing of the liquid in the condenser during cold cases, propylene was selected as the working fluid. The LHP was tested under reflux mode and with adverse elevation. Tests conducted included start-up, power cycle, steady state and transient operation during hot and cold cases, and heater power requirements for the set point temperature control of the LHP. Test results showed very successful operation of the LHP under all conditions. The 20 W starter heater proved necessary in order to start the loop when a large thermal mass was attached to the evaporator. The thermal coupling between the liquid line and the vapor line significantly reduced the heater power required for loop temperature control, which was less than 5 watts in all cases, including a cold radiator. The test also demonstrated successful operation with a propylene working fluid, with successful startups with condenser temperatures as low as 100 C. Furthermore, the test demonstrated accurate control of the loop operating temperature within +/- 0.2 C, and a successful shutdown of the loop during the survival mode of operation.

Low temperature MBBR nitrification: Microbiome analysis.

PubMed

Young, Bradley; Delatolla, Robert; Kennedy, Kevin; Laflamme, Edith; Stintzi, Alain

2017-03-15

This study aims to investigate post carbon removal moving bed biofilm reactor (MBBR) nitrification through the transition from 20 °C to 1 °C and during through long term operation at 1 °C. Four pilot nitrifying MBBR reactors were operated at various ammonia loading rates to elucidate the temperature effects on ammonia removal rates, cell viability and bacterial communities. The transition from 20 °C to 1 °C and during long term operation at 1 °C were modeled using Arrhenius temperature correction coefficients. Specifically, the steady state removal rates at 1 °C on average were 22.8% of the maximum ammonia removal rate at 20 °C, which corresponds to an Arrhenius temperature correction of 1.086 during steady operation at 1 °C. The microbial communities of the nitrifying MBBR biofilm were shown to be significantly more diverse at 20 °C as compared to 1 °C operation. Although less diverse at 1 °C, 2000 species of bacteria were identified in the nitrifying biofilm during operation at this low temperature. Nitrosomonads were shown to be the dominant ammonia oxidizing bacteria (AOB) and Nitrospira was shown to be the dominant nitrite oxidizing bacteria (NOB) in all the pilot MBBR reactors at all temperatures. The performance of the post carbon removal nitrifying MBBR systems were shown to be enhanced at 1 °C by an increase in the viable embedded biomass as well as thicker biofilm. This effectively increases the number of viable cell present during low temperature operation, which partially compensates for the significant decrease in rate of ammonia removal per nitrifying cell. Operation at the highest loading conditions tested in this study at 1 °C were shown to reduce the ammonia removal rate compared to lower loading conditions at 1 °C. The lower performance at higher loading conditions at 1 °C demonstrated an enrichment in the stress response metagenomics pathways of the system. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nano-Fabrication Methods for Micro-Miniature Optical Thermometers Suited to High Temperatures and Harsh Environments

NASA Astrophysics Data System (ADS)

DePew, K. A.; Ma, C.; Schiffbauer, J. D.; Wang, J.; Dong, B.; Lally, E.; Wang, A.

2012-12-01

The Center for Photonics Technology (CPT) at Virginia Tech is engaged in cutting edge research of fiber optic sensing technologies. One current research area is the design of fiber optic temperature sensors for harsh environments. Fiber optic temperature sensing offers significant advantages over electronic sensing in terms of size and insensitivity to harsh environmental conditions and electromagnetic interference. In the field, fiber optic thermometers have been used in recent snow cover studies as well as fluvial temperature profiling projects. The extended capabilities of CPT optical sensors open further possibilities for application in additional geologic realms requiring high temperature sensing in corrosive environments. Significant strides have been made in developing single-crystal sapphire based fiber optic sensing elements for high temperature environments which are otherwise difficult to instrument. Utilization of strain insensitive designs and optical sapphire materials allow for thermometers capable of operation above 1500°C with reduced sensitivity to chemical corrosion and mechanical interference. Current efforts in fabrication techniques are reducing the footprint of temperature sensors below the millimeter scale while maintaining high resolution and operating range. The FEI Helios 600 NanoLab workstation at the Virginia Tech Institute for Critical Technologies and Applied Science has been employed, providing the capabilities necessary to reduce the footprint of sensing elements to the dimensions of standard optical communication fiber using a Ga+ focused ion beam (FIB). The capability of semi-distributed multi-point sensing can also be accomplished at this scale using similar FIB milling techniques. The fiber optic thermometer designs resulting from these methods are compact, lightweight, and able to provide remote sensing without need for electrical power at the measurement point. These traits make them an ideal sensing platform for laboratory applications with minimal instrumentation egress as well as field deployment in areas where traditional electronic technologies cannot survive.

Changes in the performance characteristics of a GaAs near infrared light emitting diode when exposed to various current and thermal stresses

NASA Technical Reports Server (NTRS)

Thomas, E. F., Jr.

1974-01-01

The changes that occurred in the optical and electrical characteristics of a near infrared, GaAs light emitting diode, when operated under various levels and combinations of current and thermal stresses are discussed. A total of forty parts were operated for two thousand hours under eight different sets of dc current and ambient temperature conditions. Degradation in the radiant optical power of these devices was thirty-four percent when operated at their rated current and an ambient temperature of 298K (25 C). Derating the current and/or the thermal stress reduced the degradation of this parameter in approximately a linear manner. All degraded devices behaved similarly, exhibiting rapid nonlinear degradation followed by a gradual linear degradation and finally a period of stable operation. An attempt was made to correlate initial device condition to degradation during stress testing, but met with little success.

Burner Rig Laboratory

NASA Image and Video Library

2015-05-12

The Fuel Burner Rig is a test laboratory at NASA Glenn, which subjects new jet engine materials, treated with protective coatings, to the hostile, high temperature, high velocity environment found inside aircraft turbine engines. These samples face 200-mile per hour flames to simulate the temperatures of aircraft engines in flight. The rig can also simulate aircraft carrier and dusty desert operations where salt and sand can greatly reduce engine life and performance.

Technical report: The design and evaluation of a basin-scale wireless sensor network for mountain hydrology

NASA Astrophysics Data System (ADS)

Zhang, Ziran; Glaser, Steven D.; Bales, Roger C.; Conklin, Martha; Rice, Robert; Marks, Danny G.

2017-05-01

A network of sensors for spatially representative water-balance measurements was developed and deployed across the 2000 km2 snow-dominated portion of the upper American River basin, primarily to measure changes in snowpack and soil-water storage, air temperature, and humidity. This wireless sensor network (WSN) consists of 14 sensor clusters, each with 10 measurement nodes that were strategically placed within a 1 km2 area, across different elevations, aspects, slopes, and canopy covers. Compared to existing operational sensor installations, the WSN reduces hydrologic uncertainty in at least three ways. First, redundant measurements improved estimation of lapse rates for air and dew-point temperature. Second, distributed measurements captured local variability and constrained uncertainty in air and dew-point temperature, snow accumulation, and derived hydrologic attributes important for modeling and prediction. Third, the distributed relative-humidity measurements offer a unique capability to monitor upper-basin patterns in dew-point temperature and characterize elevation gradient of water vapor-pressure deficit across steep, variable topography. Network statistics during the first year of operation demonstrated that the WSN was robust for cold, wet, and windy conditions in the basin. The electronic technology used in the WSN-reduced adverse effects, such as high current consumption, multipath signal fading, and clock drift, seen in previous remote WSNs.

Low NO.sub.x multistage combustor

DOEpatents

Becker, Frederick E.; Breault, Ronald W.; Litka, Anthony F.; McClaine, Andrew W.; Shukla, Kailash

2000-01-01

A high efficiency, Vortex Inertial Staged Air (VIStA) combustor provides ultra-low NO.sub.X production of about 20 ppmvd or less with CO emissions of less than 50 ppmvd, both at 3% O.sub.2. Prompt NO.sub.X production is reduced by partially reforming the fuel in a first combustion stage to CO and H.sub.2. This is achieved in the first stage by operating with a fuel rich mixture, and by recirculating partially oxidized combustion products, with control over stoichiometry, recirculation rate and residence time. Thermal NO.sub.X production is reduced in the first stage by reducing the occurrence of high temperature combustion gas regions. This is achieved by providing the first stage burner with a thoroughly pre-mixed fuel/oxidant composition, and by recirculating part of the combustion products to further mix the gases and provide a more uniform temperature in the first stage. In a second stage combustor thermal NO.sub.X production is controlled by inducing a large flow of flue gas recirculation in the second stage combustion zone to minimize the ultimate temperature of the flame. One or both of the first and second stage burners can be cooled to further reduce the combustion temperature and to improve the recirculation efficiency. Both of these factors tend to reduce production of NO.sub.X.

Design, construction, operation and costs of a modern small-scale fuel-alcohol plant

NASA Astrophysics Data System (ADS)

Leeper, S. A.; Dawley, L. J.; Wolfram, J. H.; Berglund, G. R.; Richardson, J. G.; McAtee, R. E.

1982-01-01

The design used for the small-scale fuel alcohol plant (SSFAP) is discussed. By incorporating a microprocessor into the plant design, most plant operations were automated and labor requirements were reduced. Continuous processing made energy conservation possible, thus reducing energy requirements. A low-temperature, continuous plug-flow cooker design made high yields possible. Ethanol was consistently produced at the SSFAP from corn at a yield of 2.6 gallons (anhydrous) per bushel and an energy requirement of 30,000 to 35,000 Btu/gallon (190-proof). In addition, barley, grain dust, and potato waste were converted at the SSFAP. The capacity of the SSFAP is 180,000 gallons per year (300 days operation). Competitively priced ethanol is produced at this capacity.

High Quantum Efficiency Nanopillar Photodiodes Overcoming the Diffraction Limit of Light.

PubMed

Lee, Wook-Jae; Senanayake, Pradeep; Farrell, Alan C; Lin, Andrew; Hung, Chung-Hong; Huffaker, Diana L

2016-01-13

InAs1-xSbx nanowires have recently attracted interest for infrared sensing applications due to the small bandgap and high thermal conductivity. However, previous reports on nanowire-based infrared sensors required low operating temperatures in order to mitigate the high dark current and have shown poor sensitivities resulting from reduced light coupling efficiency beyond the diffraction limit. Here, InAsSb nanopillar photodiodes with high quantum efficiency are achieved by partially coating the nanopillar with metal that excites localized surface plasmon resonances, leading to quantum efficiencies of ∼29% at 2390 nm. These high quantum efficiency nanopillar photodiodes, with 180 nm diameters and 1000 nm heights, allow operation at temperatures as high as 220 K and exhibit a detection wavelength up to 3000 nm, well beyond the diffraction limit. The InAsSb nanopillars are grown on low cost GaAs (111)B substrates using an InAs buffer layer, making our device architecture a promising path toward low-cost infrared focal plane arrays with high operating temperature.

High-Temperature, Wirebondless, Ultracompact Wide Bandgap Power Semiconductor Modules

NASA Technical Reports Server (NTRS)

Elmes, John

2015-01-01

Silicon carbide (SiC) and other wide bandgap semiconductors offer great promise of high power rating, high operating temperature, simple thermal management, and ultrahigh power density for both space and commercial power electronic systems. However, this great potential is seriously limited by the lack of reliable high-temperature device packaging technology. This Phase II project developed an ultracompact hybrid power module packaging technology based on the use of double lead frames and direct lead frame-to-chip transient liquid phase (TLP) bonding that allows device operation up to 450 degC. The new power module will have a very small form factor with 3-5X reduction in size and weight from the prior art, and it will be capable of operating from 450 degC to -125 degC. This technology will have a profound impact on power electronics and energy conversion technologies and help to conserve energy and the environment as well as reduce the nation's dependence on fossil fuels.

Using the Transient Response of WO₃ Nanoneedles under Pulsed UV Light in the Detection of NH₃ and NO₂.

PubMed

Gonzalez, Oriol; Welearegay, Tesfalem G; Vilanova, Xavier; Llobet, Eduard

2018-04-26

Here we report on the use of pulsed UV light for activating the gas sensing response of metal oxides. Under pulsed UV light, the resistance of metal oxides presents a ripple due to light-induced transient adsorption and desorption phenomena. This methodology has been applied to tungsten oxide nanoneedle gas sensors operated either at room temperature or under mild heating (50 °C or 100 °C). It has been found that by analyzing the rate of resistance change caused by pulsed UV light, a fast determination of gas concentration is achieved (ten-fold improvement in response time). The technique is useful for detecting both oxidizing (NO₂) and reducing (NH₃) gases, even in the presence of different levels of ambient humidity. Room temperature operated sensors under pulsed UV light show good response towards ammonia and nitrogen dioxide at low power consumption levels. Increasing their operating temperature to 50 °C or 100 °C has the effect of further increasing sensitivity.

Thermal excitation spectrum from entanglement in an expanding quantum string

DOE PAGES

Berges, Jurgen; Floerchinger, Stefan; Venugopalan, Raju

2018-01-31

Here, a surprising result in e +e - collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time τ, wemore » show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature Tτ = h(2πk Bτ), even in the absence of any scatterings.« less

Advanced rocket propulsion

NASA Technical Reports Server (NTRS)

Obrien, Charles J.

1993-01-01

Existing NASA research contracts are supporting development of advanced reinforced polymer and metal matrix composites for use in liquid rocket engines of the future. Advanced rocket propulsion concepts, such as modular platelet engines, dual-fuel dual-expander engines, and variable mixture ratio engines, require advanced materials and structures to reduce overall vehicle weight as well as address specific propulsion system problems related to elevated operating temperatures, new engine components, and unique operating processes. High performance propulsion systems with improved manufacturability and maintainability are needed for single stage to orbit vehicles and other high performance mission applications. One way to satisfy these needs is to develop a small engine which can be clustered in modules to provide required levels of total thrust. This approach should reduce development schedule and cost requirements by lowering hardware lead times and permitting the use of existing test facilities. Modular engines should also reduce operational costs associated with maintenance and parts inventories.

Thermal excitation spectrum from entanglement in an expanding quantum string

NASA Astrophysics Data System (ADS)

Berges, Jürgen; Floerchinger, Stefan; Venugopalan, Raju

2018-03-01

A surprising result in e+e- collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time τ, we show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature Tτ = ħ / (2 πkB τ), even in the absence of any scatterings.

Thermal excitation spectrum from entanglement in an expanding quantum string

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berges, Jurgen; Floerchinger, Stefan; Venugopalan, Raju

Here, a surprising result in e +e - collisions is that the particle spectra from the string formed between the expanding quark-antiquark pair have thermal properties even though scatterings appear not to be frequent enough to explain this. We address this problem by considering the finite observable interval of a relativistic quantum string in terms of its reduced density operator by tracing over the complement region. We show how quantum entanglement in the presence of a horizon in spacetime for the causal transfer of information leads locally to a reduced mixed-state density operator. For very early proper time τ, wemore » show that the entanglement entropy becomes extensive and scales with the rapidity. At these early times, the reduced density operator is of thermal form, with an entanglement temperature Tτ = h(2πk Bτ), even in the absence of any scatterings.« less

Surface coating of ceria nanostructures for high-temperature oxidation protection

NASA Astrophysics Data System (ADS)

Aadhavan, R.; Bhanuchandar, S.; Babu, K. Suresh

2018-04-01

Stainless steels are used in high-temperature structural applications but suffer from degradation at an elevated temperature of operation due to thermal stress which leads to spallation. Ceria coating over chromium containing alloys induces protective chromia layer formation at alloy/ceria interface thereby preventing oxidative degradation. In the present work, three metals of differing elemental composition, namely, AISI 304, AISI 410, and Inconel 600 were tested for high-temperature stability in the presence and absence of ceria coating. Nanoceria was used as the target to deposit the coating through electron beam physical vapor deposition method. After isothermal oxidation at 1243 K for 24 h, Ceria coated AISI 304 and Inconel 600 exhibited a reduced rate of oxidation by 4 and 1 orders, respectively, in comparison with the base alloy. The formation of spinel structure was found to be lowered in the presence of ceria due to the reduced migration of cations from the alloy.

Loop Heat Pipe Operation with Thermoelectric Converters and Coupling Blocks

NASA Technical Reports Server (NTRS)

Ku, Jentung; Nagano, Hosei

2007-01-01

This paper presents theoretical and experimental studies on using thermoelectric converters (TECs) and coupling blocks to control the operating temperature of a miniature loop heat pipes (MLHP). The MLHP has two parallel evaporators and two parallel condensers, and each evaporator has its own integral compensation chamber (CC). A TEC is attached to each CC, and connected to the evaporator via a copper thermal strap. The TEC can provide both heating and cooling to the CC, therefore extending the LHP operating temperature over a larger range of the evaporator heat load. A bi-polar power supply is used for the TEC operation. The bipolar power supply automatically changes the direction of the current to the TEC, depending on whether the CC requires heating or cooling, to maintain the CC temperature at the desired set point. The TEC can also enhance the startup success by maintaining a constant CC temperature during the start-up transient. Several aluminum coupling blocks are installed between the vapor line and liquid line. The coupling blocks serve as a heat exchanger which preheats the cold returning liquid so as to reduce the amount of liquid subcooling, and hence the power required to maintain the CC at the desired set point temperature. This paper focuses on the savings of the CC control heater power afforded by the TECs when compared to traditional electric heaters. Tests were conducted by varying the evaporator power, the condenser sink temperature, the CC set point temperature, the number of coupling blocks, and the thermal conductance of the thermal strap. Test results show that the TECs are able to control the CC temperature within k0.5K under all test conditions, and the required TEC heater power is only a fraction of the required electric heater power.

Evaluation of Heliostat Standby Aiming Strategies to Reduce Avian Flux Hazards and Impacts on Operational Performance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendelin, Timothy J; Ho, Clifford K.; Horstman, Luke

This paper presents a study of alternative heliostat standby aiming strategies and their impact on avian flux hazards and operational performance of a concentrating solar power plant. A mathematical model was developed that predicts the bird-feather temperature as a function of solar irradiance, thermal emittance, convection, and thermal properties of the feather. The irradiance distribution in the airspace above the Ivanpah Unit 2 heliostat field was simulated using a ray-trace model for two different times of the day, four days of the year, and nine different standby aiming strategies. The impact of the alternative aiming strategies on operational performance wasmore » assessed by comparing the heliostat slew times from standby position to the receiver for the different aiming strategies. Increased slew times increased a proxy start-up time that reduced the simulated annual energy production. Results showed that spreading the radial aim points around the receiver to a distance of ~150 m or greater reduced the hazardous exposure times that the feather temperature exceeded the hazard metric of 160 degrees C. The hazardous exposure times were reduced by ~23% and 90% at a radial spread of aim points extending to 150 m and 250 m, respectively, but the simulated annual energy production decreased as a result of increased slew times. Single point-focus aiming strategies were also evaluated, but these strategies increased the exposure hazard relative to other aiming strategies.« less

Comparison of operating strategies for increased biogas production from thin stillage.

PubMed

Moestedt, Jan; Nordell, Erik; Schnürer, Anna

2014-04-10

The effect of increasing organic loading rate (OLR) and simultaneously decreasing hydraulic retention time (HRT) during anaerobic digestion of sulphur- and nitrogen-rich thin stillage was investigated during operation of continuously stirred tank laboratory reactors at two different temperatures. The operating strategies and substrate were set in order to mimic an existing full-scale commercial biogas plant in Sweden. The reactors were operated for 554-570 days with a substrate mixture of thin stillage and milled grain, resulting in high ammonium concentrations (>4.5gL(-1)). Initially, one reactor was operated at 38°C, as in the full-scale plant, while in the experimental reactor the temperature was raised to 44°C. Both reactors were then subjected to increasing OLR (from 3.2 to 6.0gVSL(-1)d(-1)) and simultaneously decreasing HRT (from 45 to 24 days) to evaluate the effects of these operational strategies on process stability, hydrogen sulphide levels and microbial composition. The results showed that operation at 44°C was the most successful strategy, resulting in up to 22% higher methane yield compared with the mesophilic reactor, despite higher free ammonia concentration. Furthermore, kinetic studies revealed higher biogas production rate at 44°C compared with 38°C, while the level of hydrogen sulphide was not affected. Quantitative PCR analysis of the microbiological population showed that methanogenic archaea and syntrophic acetate-oxidising bacteria had responded to the new process temperature while sulphate-reducing bacteria were only marginally affected by the temperature-change. Copyright © 2014 Elsevier B.V. All rights reserved.

Low-Cost Production of Composite Bushings for Jet Engine Applications

NASA Technical Reports Server (NTRS)

Gray, Robert A.

1998-01-01

The objectives of this research program were to reduce the manufacturing costs of variable stator vane bushings by 1) eliminating the expensive carbon fiber braiding operation, 2) replacing the batch mode impregnation, B-stage, and cutting operations with a continuous process, and 3) reducing the molding cycle and machining operations with injection molding to achieve near-net shapes. Braided bushings were successfully fabricated with both AMB-17XLD and AMB-TPD resin systems. The composite bushings achieved high glass transition temperature after post-cure (+300 C) and comparable weight loss to the PNM-15 bushings. ANM-17XLD bushings made with "batch-mode" molding compound (at 0.5 in. fiber length) achieved a +300 lb-force flange break strength which was superior to the continuous braided-fiber reinforced bushing. The non-MDA resin technology developed in this contract appears attractive for bushing applications that do not exceed a 300 C use temperature. Two thermoplastic polyimide resins were synthesized in order to generate injection molding compound powders. Excellent processing results were obtained at injection temperatures in excess of 300 C. Micro-tensile specimens were produced from each resin type and the Tg measurements (by TMA) for these samples were equivalent to AURUM(R). Thermal Gravimetric Analysis (TGA) conducted at 10 C/min showed that the non-MDA AMB-type polyimide thermoplastics had comparable weight loss to PMR-15 up to 500 C.

Wear and friction characteristics of electroless Ni-B-W coatings at different operating temperatures

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Arkadeb; Barman, Tapan Kumar; Sahoo, Prasanta

2018-02-01

Sodium borohydride reduced electroless nickel alloy coatings have high wear resistance and low coefficient of friction. The present work investigates the deposition and tribological behavior of a ternary variant of the borohydride reduced coating i.e. Ni-B-W. Electroless Ni-B-W coatings were deposited on AISI 1040 steel substrates. In order to improve the mechanical properties of the deposits, they were heat treated at 350 °C for 1 h. The coatings in their as-deposited and heat treated conditions were characterized by scanning electron microscope, energy dispersive x-ray analysis and x-ray diffraction techniques. Ni-B-W coatings are amorphous in their as-deposited state while they become crystalline on heat treatment. In fact a high microhardness of Ni-B-W coatings is also observed in as-deposited condition. The microhardness further improves on heat treatment. Tribological behavior of the heat treated coatings with varying load (10-50 N), sliding speed (0.25-0.42 m s-1) and operating temperature (25 °C-500 °C) were evaluated on a pin-on-disc type test setup while the wear mechanisms were also studied. Tribological behavior of Ni-B-W coatings is enhanced at 500 °C operating temperature in comparison with 100 or 300 °C due to formation of protective oxide scales and microstructural changes due to in-situ heat treatment effect.

Evaluation of Bosch-Based Systems Using Non-Traditional Catalysts at Reduced Temperatures

NASA Technical Reports Server (NTRS)

Abney, Morgan B.; Mansell, J. Matthew

2011-01-01

Oxygen and water resupply make open loop atmosphere revitalization (AR) systems unfavorable for long-term missions beyond low Earth orbit. Crucial to closing the AR loop are carbon dioxide reduction systems with low mass and volume, minimal power requirements, and minimal consumables. For this purpose, NASA is exploring using Bosch-based systems. The Bosch process is favorable over state-of-the-art Sabatier-based processes due to complete loop closure. However, traditional operation of the Bosch required high reaction temperatures, high recycle rates, and significant consumables in the form of catalyst resupply due to carbon fouling. A number of configurations have been proposed for next-generation Bosch systems. First, alternative catalysts (catalysts other than steel wool) can be used in a traditional single-stage Bosch reactor to improve reaction kinetics and increase carbon packing density. Second, the Bosch reactor may be split into separate stages wherein the first reactor stage is dedicated to carbon monoxide and water formation via the reverse water-gas shift reaction and the second reactor stage is dedicated to carbon formation. A series system will enable maximum efficiency of both steps of the Bosch reaction, resulting in optimized operation and maximum carbon formation rate. This paper details the results of testing of both single-stage and two-stage Bosch systems with alternative catalysts at reduced temperatures. These results are compared to a traditional Bosch system operated with a steel wool catalyst.

Development of Electronics for Low-Temperature Space Missions

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Dickman, John E.; Gerber, Scott S.; Overton, Eric

2001-01-01

Electronic systems that are capable of operating at cryogenic temperatures will be needed for many future NASA space missions, including deep space probes and spacecraft for planetary surface exploration. In addition to being able to survive the harsh deep space environment, low-temperature electronics would help improve circuit performance, increase system efficiency, and reduce payload development and launch costs. Terrestrial applications where components and systems must operate in low-temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation systems, and arctic exploration. An ongoing research and development project for the design, fabrication, and characterization of low-temperature electronics and supporting technologies at NASA Glenn Research Center focuses on efficient power systems capable of surviving in and exploiting the advantages of low-temperature environments. Supporting technologies include dielectric and insulating materials, semiconductor devices, passive power components, optoelectronic devices, and packaging and integration of the developed components into prototype flight hardware. An overview of the project is presented, including a description of the test facilities, a discussion of selected data from component testing, and a presentation of ongoing research activities being performed in collaboration with various organizations.

Community Microgrid Scheduling Considering Network Operational Constraints and Building Thermal Dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Guodong; Ollis, Thomas B.; Xiao, Bailu

Here, this paper proposes a Mixed Integer Conic Programming (MICP) model for community microgrids considering the network operational constraints and building thermal dynamics. The proposed optimization model optimizes not only the operating cost, including fuel cost, purchasing cost, battery degradation cost, voluntary load shedding cost and the cost associated with customer discomfort due to room temperature deviation from the set point, but also several performance indices, including voltage deviation, network power loss and power factor at the Point of Common Coupling (PCC). In particular, the detailed thermal dynamic model of buildings is integrated into the distribution optimal power flow (D-OPF)more » model for the optimal operation of community microgrids. The heating, ventilation and air-conditioning (HVAC) systems can be scheduled intelligently to reduce the electricity cost while maintaining the indoor temperature in the comfort range set by customers. Numerical simulation results show the effectiveness of the proposed model and significant saving in electricity cost could be achieved with network operational constraints satisfied.« less

Community Microgrid Scheduling Considering Network Operational Constraints and Building Thermal Dynamics

DOE PAGES

Liu, Guodong; Ollis, Thomas B.; Xiao, Bailu; ...

2017-10-10

Here, this paper proposes a Mixed Integer Conic Programming (MICP) model for community microgrids considering the network operational constraints and building thermal dynamics. The proposed optimization model optimizes not only the operating cost, including fuel cost, purchasing cost, battery degradation cost, voluntary load shedding cost and the cost associated with customer discomfort due to room temperature deviation from the set point, but also several performance indices, including voltage deviation, network power loss and power factor at the Point of Common Coupling (PCC). In particular, the detailed thermal dynamic model of buildings is integrated into the distribution optimal power flow (D-OPF)more » model for the optimal operation of community microgrids. The heating, ventilation and air-conditioning (HVAC) systems can be scheduled intelligently to reduce the electricity cost while maintaining the indoor temperature in the comfort range set by customers. Numerical simulation results show the effectiveness of the proposed model and significant saving in electricity cost could be achieved with network operational constraints satisfied.« less

Development and application of a specially designed heating system for temperature-programmed high-performance liquid chromatography using subcritical water as the mobile phase.

PubMed

Teutenberg, T; Goetze, H-J; Tuerk, J; Ploeger, J; Kiffmeyer, T K; Schmidt, K G; Kohorst, W gr; Rohe, T; Jansen, H-D; Weber, H

2006-05-05

A specially designed heating system for temperature-programmed HPLC was developed based on experimental measurements of eluent temperature inside a stainless steel capillary using a very thin thermocouple. The heating system can be operated at temperatures up to 225 degrees C and consists of a preheating, a column heating and a cooling unit. Fast cycle times after a temperature gradient can be realized by an internal silicone oil bath which cools down the preheating and column heating unit. Long-term thermal stability of a polybutadiene-coated zirconium dioxide column has been evaluated using a tubular oven in which the column was placed. The packing material was stable after 50h of operation at 185 degrees C. A mixture containing four steroids was separated at ambient conditions using a mobile phase of 25% acetonitrile:75% deionized water and a mobile phase of pure deionized water at 185 degrees C using the specially designed heating system and the PBD column. Analysis time could be drastically reduced from 17 min at ambient conditions and a flow rate of 1 mL/min to only 1.2 min at 185 degrees C and a flow rate of 5 mL/min. At these extreme conditions, no thermal mismatch was observed and peaks were not distorted, thus underlining the performance of the developed heating system. Temperature programming was performed by separating cytostatic and antibiotic drugs with a temperature gradient using only water as the mobile phase. In contrast to an isocratic elution of this mixture at room temperature, overall analysis time could be reduced two-fold from 20 to 10 min.

Microgravity heat pump for space station thermal management.

PubMed

Domitrovic, R E; Chen, F C; Mei, V C; Spezia, A L

2003-01-01

A highly efficient recuperative vapor compression heat pump was developed and tested for its ability to operate independent of orientation with respect to gravity while maximizing temperature lift. The objective of such a heat pump is to increase the temperature of, and thus reduce the size of, the radiative heat rejection panels on spacecrafts such as the International Space Station. Heat pump operation under microgravity was approximated by gravitational-independent experiments. Test evaluations include functionality, efficiency, and temperature lift. Commercially available components were used to minimize costs of new hardware development. Testing was completed on two heat pump design iterations--LBU-I and LBU--II, for a variety of operating conditions under the variation of several system parameters, including: orientation, evaporator water inlet temperature (EWIT), condenser water inlet temperature (CWIT), and compressor speed. The LBU-I system employed an ac motor, belt-driven scroll compressor, and tube-in-tube heat exchangers. The LBU-II system used a direct-drive AC motor compressor assembly and plate heat exchangers. The LBU-II system in general outperformed the LBU-I system on all accounts. Results are presented for all systems, showing particular attention to those states that perform with a COP of 4.5 +/- 10% and can maintain a temperature lift of 55 degrees F (30.6 degrees C) +/- 10%. A calculation of potential radiator area reduction shows that points with maximum temperature lift give the greatest potential for reduction, and that area reduction is a function of heat pump efficiency and a stronger function of temperature lift.

Performance improvement of a large capacity GM cryocooler

NASA Astrophysics Data System (ADS)

Wang, C.; Olesh, A.; Cosco, J.

2017-12-01

This paper presents the improvement of a large GM cryocooler, Cryomech model AL600, based on redesigning a cold head stem seal, regenerator, heat exchanger and displacer bumper as well as optimizing operating parameters. The no-load temperature is reduced from 26.6 K to 23.4 K. The cooling capacity is improved from 615 W to 701W at 80 K with a power input of 12.5 kW. It has the highest relative Carnot Efficiency at 15.4%. The vibration of AL600 is investigated experimentally. The new displacer bumper significantly reduces the vibration force on the room temperature flange by 82 % from 520 N to 93 N.

Apparatus and method to reduce wear and friction between CMC-to-metal attachment and interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cairo, Ronald Ralph; Parolini, Jason Robert; Delvaux, John McConnell

An apparatus to reduce wear and friction between CMC-to-metal attachment and interface, including a metal layer configured for insertion between a surface interface between a CMC component and a metal component. The surface interface of the metal layer is compliant relative to asperities of the surface interface of the CMC component. A coefficient of friction between the surface interface of the CMC component and the metal component is about 1.0 or less at an operating temperature between about 300.degree. C. to about 325.degree. C. and a limiting temperature of the metal component.

PHEMT as a circuit element for high impedance nanopower amplifiers for ultra-low temperatures application

NASA Astrophysics Data System (ADS)

Korolev, A. M.; Shulga, V. M.; Gritsenko, I. A.; Sheshin, G. A.

2015-04-01

In this work, high electron mobility transistor (HEMT) was studied as a circuit element for amplifiers operating at temperatures of the order of 10-100 mK. To characterize the HEMT, the relative parameters are proposed to be used. HEMT characteristics were measured at a temperature of 50 mK for the first time. It follows from the reported studies that the power consumption of high-impedance HEMT-based amplifiers can be reduced down to hundreds of nanowatt or even lower.

Potential use of ceramic coating as a thermal insulation on cooled turbine hardware

NASA Technical Reports Server (NTRS)

Liebert, C. H.; Stepka, F. S.

1976-01-01

An analysis was made to determine the potential benefits of using a ceramic thermal insulation coating of calcia-stabilized zirconia on cooled engine parts. The analysis was applied to turbine vanes of a high temperature and high pressure core engine and a moderate temperature and low pressure research engine. Measurements made during engine operation showed that the coating substantially reduced vane metal wall temperatures. Evaluation of the durability of the coating on turbine vanes and blades in a furnace and engine were encouraging.

Solid oxide fuel cell cathode infiltrate particle size control and oxygen surface exchange resistance determination

NASA Astrophysics Data System (ADS)

Burye, Theodore E.

Over the past decade, nano-sized Mixed Ionic Electronic Conducting (MIEC) -- micro-sized Ionic Conducting (IC) composite cathodes produced by the infiltration method have received much attention in the literature due to their low polarization resistance (RP) at intermediate (500-700°C) operating temperatures. Small infiltrated MIEC oxide nano-particle size and low intrinsic MIEC oxygen surface exchange resistance (Rs) have been two critical factors allowing these Nano-Micro-Composite Cathodes (NMCCs) to achieve high performance and/or low temperature operation. Unfortunately, previous studies have not found a reliable method to control or reduce infiltrated nano-particle size. In addition, controversy exists on the best MIEC infiltrate composition because: 1) Rs measurements on infiltrated MIEC particles are presently unavailable in the literature, and 2) bulk and thin film Rs measurements on nominally identical MIEC compositions often vary by up to 3 orders of magnitude. Here, two processing techniques, precursor nitrate solution desiccation and ceria oxide pre-infiltration, were developed to systematically produce a reduction in the average La0.6Sr0.4Co0.8Fe 0.2O3-delta (LSCF) infiltrated nano-particle size from 50 nm to 22 nm. This particle size reduction reduced the SOFC operating temperature, (defined as the temperature where RP=0.1 Ocm 2) from 650°C to 540°C. In addition, Rs values for infiltrated MIEC particles were determined for the first time through finite element modeling calculations on 3D Focused Ion Beam-Scanning Electron Microscope (FIB-SEM) reconstructions of electrochemically characterized infiltrated electrodes.

The energy cost of quantum information losses

NASA Astrophysics Data System (ADS)

Romanelli, Alejandro; de Lima Marquezino, Franklin; Portugal, Renato; Donangelo, Raul

2018-05-01

We explore the energy cost of the information loss resulting from the passage of an initial density operator to a reduced one. We use the concept of entanglement temperature in order to obtain a lower bound for the energy change associated with this operation. We determine the minimal energy required for the case of the information losses associated with the trace over the space coordinates of a two-dimensional quantum walk.

Micro-mechanical resonators for dynamically reconfigurable reduced voltage logic gates

NASA Astrophysics Data System (ADS)

Chappanda, K. N.; Ilyas, S.; Younis, M. I.

2018-05-01

Due to the limitations of transistor-based logic devices such as their poor performance at elevated temperature, alternative computing methods are being actively investigated. In this work, we present electromechanical logic gates using electrostatically coupled in-plane micro-cantilever resonators operated at modest vacuum conditions of 5 Torr. Operating in the first resonant mode, we demonstrate 2-bit XOR, 2- and 3-bit AND, 2- and 3-bit NOR, and 1-bit NOT gates; all condensed in the same device. Through the designed electrostatic coupling, the required voltage for the logic gates is reduced by 80%, along with the reduction in the number of electrical interconnects and devices per logic operation (contrary to transistors). The device is dynamically reconfigurable between any logic gates in real time without the need for any change in the electrical interconnects and the drive circuit. By operating in the first two resonant vibration modes, we demonstrate mechanical logic gates consisting of two 2-bit AND and two 2-bit XOR gates. The device is tested at elevated temperatures and is shown to be functional as a logic gate up to 150 °C. Also, the device has high reliability with demonstrated lifetime greater than 5  ×  1012 oscillations.

A new cryostat for precise temperature control

NASA Astrophysics Data System (ADS)

Dong, B.; Zhou, G.; Liu, L. Q.; Zhang, X.; Xiong, L. Y.; Li, Q.

2013-09-01

Gifford-McMahon (GM) cryocoolers are often used in cryostat as cold sources. It has advantages of simple structure and low operating cost as well as disadvantages of vibration and temperature oscillation, which are fatal for some applications that are very sensitive to temperature stability at low temperature. To solve the problem, a thermal analysis model which is used to simulate heat transfer in the cryostat is built and discussed. According to the analysis results, a cryostat that can provide variable temperature (4-20 K) for the accurate temperature control experiments is designed and manufactured. In this cryostat, a polytetrafluoroethylene (PTFE) sheet is used as a thermal damper to reduce the temperature oscillation, with which, the temperature oscillation of the sample cooling holder is less than 4 mK at the 20 K region.

Phenomenological Studies on Sodium for CSP Applications: A Safety Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armijo, Kenneth Miguel; Andraka, Charles E.

Sodium as a heat transfer fluid (HTF) can achieve temperatures above 700°C to improve power cycle performance for reducing large infrastructure costs of high-temperature systems. Current concentrating solar power (CSP) sensible HTF’s (e.g. air, salts) have poor thermal conductivity, and thus low heat transfer capabilities, requiring a large receiver. The high thermal conductivity of sodium has demonstrated high heat transfer rates on dish and towers systems, which allow a reduction in receiver area by a factor of two to four, reducing re-radiation and convection losses and cost by a similar factor. Sodium produces saturated vapor at pressures suitable for transportmore » starting at 600°C and reaches one atmosphere at 870°C, providing a wide range of suitable latent operating conditions that match proposed high temperature, isothermal input power cycles. This advantage could increase the receiver and system efficiency while lowering the cost of CSP tower systems. Although there are a number of desirable thermal performance advantages associated with sodium, its propensity to rapidly oxidize presents safety challenges. This investigation presents a literature review that captures historical operations/handling lessons for advanced sodium systems, and the current state-of-knowledge related to sodium combustion behavior. Technical and operational solutions addressing sodium safety and applications in CSP will be discussed, including unique safety hazards and advantages using latent sodium. Operation and maintenance experience from the nuclear industry with sensible and latent systems will also be discussed in the context of safety challenges and risk mitigation solutions.« less

Horticultural, systems-engineering and economic evaluations of short-term plant storage techniques as a labor management tool for vegetable grafting nurseries

PubMed Central

Son, Young-Jun; Lewis, Myles; Spalholz, Hans; Tronstad, Russell

2017-01-01

This transdisciplinary study has a three-fold systems approach in evaluating a horticultural technology: 1) horticultural evaluations, 2) economic and resource analyses, and 3) systems engineering analyses, using low temperature storage as an example technology. Vegetable grafting is a technique to produce value-added seedlings but requires labor intensive nursery operations. Low temperature storage of seedlings for a short period of time can reduce peak production, but has not been evaluated at the extent demonstrated in this paper. Seedlings of 22 genotypes of Cucurbitaceae (cucurbit family) and Solanaceae (nightshade family) were evaluated for storability under selected temperatures and photosynthetic photon flux. Storability of Cucurbitaceous seedlings varied between 2 to 4 weeks at 12°C and 13 μmol m-2 s-1. Solanaceous seedlings were generally storable for 4 weeks at 12°C and 13 μmol m-2 s-1, but tomato seedlings could be stored for 4 weeks at 10°C and 5 μmol m-2 s-1. Capital and weekly operational costs of a low temperature storage system with a design that meets environmental requirements were estimated as $671 to $708 per m2 footprint and $0.79 to $2.21 per m2 footprint per week, respectively. Electricity costs per plant was less than 0.1 cents for 2 to 4 weeks of storage. Using a schedule-optimization heuristic and a logistics simulator previously developed for grafting nursery operations, six production scenarios consisting of two crops (tomato or watermelon) and three production peak patterns were examined to evaluate the impact of including low temperature storage. While the overall average costs of grafting labor were not significantly different, maximum labor demand and grafting labor cost during the peak production week were reduced by 31% to 50% and 14% to 30% by using storage, respectively. Therefore, low temperature storage can be an effective means to address the issue of labor management in grafting nurseries. PMID:28182757

Advances in tunable diode laser technology

NASA Technical Reports Server (NTRS)

Lo, W.

1980-01-01

The improvement of long-term reliability, the purification of mode properties, and the achievement of higher-temperature operation were examined. In reliability studies a slow increase in contact resistance during room temperature storage for lasers fabricated with In-Au or In-Pt contacts was observed. This increase is actually caused by the diffusion of In into the surface layer of laser crystals. By using a three layered structure of In-Au-Pt or In-Pt-Au, this mode of degradation was reduced. In characterizing the mode properties, it was found that the lasers emit in a highly localized, filamentary manner. For widestripe lasers the emission occurs near the corners of the junction. In order to achieve single-mode operation, stripe widths on the order of 8-10 micrometers are needed. Also, it was found that room temperature electroluminescence is possible near 4.6 micrometers.

Study on Endurance and Performance of Impregnated Ruthenium Catalyst for Thruster System.

PubMed

Kim, Jincheol; Kim, Taegyu

2018-02-01

Performance and endurance of the Ru catalyst were studied for nitrous oxide monopropellant thruster system. The thermal decomposition of N2O requires a considerably high temperature, which make it difficult to be utilized as a thruster propellant, while the propellant decomposition temperature can be reduced by using the catalyst through the decomposition reaction with the propellant. However, the catalyst used for the thruster was frequently exposed to high temperature and high-pressure environment. Therefore, the state change of the catalyst according to the thruster operation was analyzed. Characterization of catalyst used in the operation condition of the thruster was performed using FE-SEM and EDS. As a result, performance degradation was occurred due to the volatilization of Ru catalyst and reduction of the specific surface area according to the phase change of Al2O3.

Measuring Thermoelectric Properties Automatically

NASA Technical Reports Server (NTRS)

Chmielewski, A.; Wood, C.

1986-01-01

Microcomputer-controlled system speeds up measurements of Hall voltage, Seebeck coefficient, and thermal diffusivity in semiconductor compounds for thermoelectric-generator applications. With microcomputer system, large data base of these parameters gathered over wide temperature range. Microcomputer increases measurement accuracy, improves operator productivity, and reduces test time.

YBCO microbolometer operating below Tc - A modelization based on critical current-temperature dependence

NASA Astrophysics Data System (ADS)

Robbes, D.; Langlois, P.; Dolabdjian, C.; Bloyet, D.; Hamet, J. F.; Murray, H.

1993-03-01

Using careful measurements of the I-V curve of a YBCO thin-film microbridge under light irradiation at 780 nm and temperature close to 77 K, it is shown that the critical current versus temperature dependence is a good thermometer for estimating bolometric effects in the film. A novel dynamic voltage bias is introduced which directly gives the device current responsitivity and greatly reduces risks of thermal runaway. Detectivity is very low but it is predicted that a noise equivalent temperature of less than 10 exp -7 K/sq rt Hz would be achievable in a wide temperature range (10-80 K), which is an improvement over thermometry at the resistive transition.

Supplemental heating of deposition tooling shields

DOEpatents

Ohlhausen, James A.; Peebles, Diane E.; Hunter, John A.; Eckelmeyer, Kenneth H.

2000-01-01

A method of reducing particle generation from the thin coating deposited on the internal surfaces of a deposition chamber which undergoes temperature variation greater than 100.degree. C. comprising maintaining the temperature variation of the internal surfaces low enough during the process cycle to keep thermal expansion stresses between the coating and the surfaces under 500 MPa. For titanium nitride deposited on stainless steel, this means keeping temperature variations under approximately 70.degree. C. in a chamber that may be heated to over 350.degree. C. during a typical processing operation. Preferably, a supplemental heater is mounted behind the upper shield and controlled by a temperature sensitive element which provides feedback control based on the temperature of the upper shield.

Hand-to-hand coupling and strategies to minimize unintentional energy transfer during laparoscopic surgery.

PubMed

Overbey, Douglas M; Hilton, Sarah A; Chapman, Brandon C; Townsend, Nicole T; Barnett, Carlton C; Robinson, Thomas N; Jones, Edward L

2017-11-01

Energy-based devices are used in nearly every laparoscopic operation. Radiofrequency energy can transfer to nearby instruments via antenna and capacitive coupling without direct contact. Previous studies have described inadvertent energy transfer through bundled cords and nonelectrically active wires. The purpose of this study was to describe a new mechanism of stray energy transfer from the monopolar instrument through the operating surgeon to the laparoscopic telescope and propose practical measures to decrease the risk of injury. Radiofrequency energy was delivered to a laparoscopic L-hook (monopolar "bovie"), an advanced bipolar device, and an ultrasonic device in a laparoscopic simulator. The tip of a 10-mm telescope was placed adjacent but not touching bovine liver in a standard four-port laparoscopic cholecystectomy setup. Temperature increase was measured as tissue temperature from baseline nearest the tip of the telescope which was never in contact with the energy-based device after a 5-s open-air activation. The monopolar L-hook increased tissue temperature adjacent to the camera/telescope tip by 47 ± 8°C from baseline (P < 0.001). By having an assistant surgeon hold the camera/telescope (rather than one surgeon holding both the active electrode and the camera/telescope), temperature change was reduced to 26 ± 7°C (P < 0.001). Alternative energy devices significantly reduced temperature change in comparison to the monopolar instrument (47 ± 8°C) for both the advanced bipolar (1.2 ± 0.5°C; P < 0.001) and ultrasonic (0.6 ± 0.3°C; P < 0.001) devices. Stray energy transfers from the monopolar "bovie" instrument through the operating surgeon to standard electrically inactive laparoscopic instruments. Hand-to-hand coupling describes a new form of capacitive coupling where the surgeon's body acts as an electrical conductor to transmit energy. Strategies to reduce stray energy transfer include avoiding the same surgeon holding the active electrode and laparoscopic camera or using alternative energy devices. Copyright © 2017 Elsevier Inc. All rights reserved.

Method of CO.sub.2 removal from a gasesous stream at reduced temperature

DOEpatents

Fisher, James C; Siriwardane, Ranjani V; Berry, David A; Richards, George A

2014-11-18

A method for the removal of H.sub.2O and CO.sub.2 from a gaseous stream comprising H.sub.2O and CO.sub.2, such as a flue gas. The method initially utilizes an H.sub.2O removal sorbent to remove some portion of the H.sub.2O, producing a dry gaseous stream and a wet H.sub.2O removal sorbent. The dry gaseous stream is subsequently contacted with a CO.sub.2 removal sorbent to remove some portion of the CO.sub.2, generating a dry CO.sub.2 reduced stream and a loaded CO.sub.2 removal sorbent. The loaded CO.sub.2 removal sorbent is subsequently heated to produce a heated CO.sub.2 stream. The wet H.sub.2O removal sorbent and the dry CO.sub.2 reduced stream are contacted in a first regeneration stage, generating a partially regenerated H.sub.2O removal sorbent, and the partially regenerated H.sub.2O removal sorbent and the heated CO.sub.2 stream are subsequently contacted in a second regeneration stage. The first and second stage regeneration typically act to retain an initial monolayer of moisture on the various removal sorbents and only remove moisture layers bound to the initial monolayer, allowing for relatively low temperature and pressure operation. Generally the applicable H.sub.2O sorption/desorption processes may be conducted at temperatures less than about 70.degree. C. and pressures less than 1.5 atmospheres, with certain operations conducted at temperatures less than about 50.degree. C.

Space Technology: Game Changing Development Deep Space Engine (DSE) 100 lbf and 5 lbf Thruster Development and Qualification

NASA Technical Reports Server (NTRS)

Barnett, Gregory

2017-01-01

Science mission studies require spacecraft propulsion systems that are high-performance, lightweight, and compact. Highly matured technology and low-cost, short development time of the propulsion system are also very desirable. The Deep Space Engine (DSE) 100-lbf thruster is being developed to meet these needs. The overall goal of this game changing technology project is to qualify the DSE thrusters along with 5-lbf attitude control thrusters for space flight and for inclusion in science and exploration missions. The aim is to perform qualification tests representative of mission duty cycles. Most exploration missions are constrained by mass, power and cost. As major propulsion components, thrusters are identified as high-risk, long-lead development items. NASA spacecraft primarily rely on 1960s' heritage in-space thruster designs and opportunities exist for reducing size, weight, power, and cost through the utilization of modern materials and advanced manufacturing techniques. Advancements in MON-25/MMH hypergolic bipropellant thrusters represent a promising avenue for addressing these deficiencies with tremendous mission enhancing benefits. DSE is much lighter and costs less than currently available thrusters in comparable thrust classes. Because MON-25 propellants operate at lower temperatures, less power is needed for propellant conditioning for in-space propulsion applications, especially long duration and/or deep-space missions. Reduced power results in reduced mass for batteries and solar panels. DSE is capable of operating at a wide propellant temperature range (between -22 F and 122 F) while a similar existing thruster operates between 45 F and 70 F. Such a capability offers robust propulsion operation as well as flexibility in design. NASA's Marshall Space Flight Center evaluated available operational Missile Defense Agency heritage thrusters suitable for the science and lunar lander propulsion systems.

Identification of Flights for Cost-Efficient Climate Impact Reduction

NASA Technical Reports Server (NTRS)

Chen, Neil Y.; Kirschen, Philippe G.; Sridhar, Banavar; Ng, Hok K.

2014-01-01

The aircraft-induced climate impact has drawn attention in recent years. Aviation operations affect the environment mainly through the release of carbon-dioxide, nitrogen-oxides, and by the formation of contrails. Recent research has shown that altering trajectories can reduce aviation environmental cost by reducing Absolute Global Temperature Change Potential, a climate assessment metric that adapts a linear system for modeling the global temperature response to aviation emissions and contrails. However, these methods will increase fuel consumption that leads to higher fuel costs imposed on airlines. The goal of this work is to identify ights for which the environmental cost of climate impact reduction outweighs the increase in operational cost on an individual aircraft basis. Environmental cost is quanti ed using the monetary social cost of carbon. The increase in operational cost is considering cost of additional fuel usage only. For this paper, an algorithm has been developed that modi es the trajectories of ights to evaluate the e ect of environ- mental cost and operational cost of ights in the United States National Airspace System. The algorithm identi es ights for which the environmental cost of climate impact can be reduced and modi es their trajectories to achieve maximum environmental net bene t, which is the di erence between reduction in environmental cost and additional operational cost. The result shows on a selected day, 16% of the ights among eight major airlines, or 2,043 ights, can achieve environmental net bene t using weather forecast data, resulting in net bene t of around $500,000. The result also suggests that the long-haul ights would be better candidates for cost-ecient climate impact reduction than the short haul ights. The algorithm will help to identify the characteristics of ights that are capable of applying cost-ecient climate impact reduction strategy.

Humidification during laparoscopic surgery: overview of the clinical benefits of using humidified gas during laparoscopic surgery.

PubMed

Binda, Maria Mercedes

2015-11-01

The peritoneum is the serous membrane that covers the abdominal cavity and most of the intra-abdominal organs. It is a very delicate layer highly susceptible to damage and it is not designed to cope with variable conditions such as the dry and cold carbon dioxide (CO2) during laparoscopic surgery. The aim of this review was to evaluate the effects caused by insufflating dry and cold gas into the abdominal cavity after laparoscopic surgery. A literature search using the Pubmed was carried out. Articles identified focused on the key issues of laparoscopy, peritoneum, morphology, pneumoperitoneum, humidity, body temperature, pain, recovery time, post-operative adhesions and lens fogging. Insufflating dry and cold CO2 into the abdomen causes peritoneal damage, post-operative pain, hypothermia and post-operative adhesions. Using humidified and warm gas prevents pain after surgery. With regard to hypothermia due to desiccation, it can be fully prevented using humidified and warm gas. Results relating to the patient recovery are still controversial. The use of humidified and warm insufflation gas offers a significant clinical benefit to the patient, creating a more physiologic peritoneal environment and reducing the post-operative pain and hypothermia. In animal models, although humidified and warm gas reduces post-operative adhesions, humidified gas at 32 °C reduced them even more. It is clear that humidified gas should be used during laparoscopic surgery; however, a question remains unanswered: to achieve even greater clinical benefit to the patient, at what temperature should the humidified gas be when insufflated into the abdomen? More clinical trials should be performed to resolve this query.

Method for improving the mechanical properties of uranium-1 to 3 wt % zirconium alloy

DOEpatents

Anderson, R.C.

1983-11-22

A uranium-1 to 3 wt % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750 to 850/sup 0/C and then quenched in water, is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenchd plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325 to 375/sup 0/C for five to six hours and then aging the plate at a higher temperature ranging from 480 to 500/sup 0/C for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

Energy Storage and Generation for Extreme Temperature and Pressure and Directional Measurement While Drilling Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Signorelli, Riccardo; Cooley, John

2015-10-14

FastCAP Systems Corporation has successfully completed all milestones defined by the award DE-EE0005503. Under this program, FastCAP developed three critical subassemblies to TRL3 demonstrating proof of concept of a geothermal MWD power source. This power source includes an energy harvester, electronics and a novel high temperature ultracapacitor (“ultracap”) rechargeable energy storage device suitable for geothermal exploration applications. FastCAP’s ruggedized ultracapacitor (ultracap) technology has been proven and commercialized in oil and gas exploration operating to rated temperatures of 150°C. Characteristics of this technology are that it is rechargeable and relatively high power. This technology was the basis for the advancements inmore » rechargeable energy storage under this project. The ultracap performs reliably at 250°C and beyond and operates over a wide operating temperature range: -5°C to 250°C. The ultracap has significantly higher power density than lithium thionyl chloride batteries, a non-rechargeable incumbent used in oil and gas drilling today. Several hermetically sealed, prototype devices were tested in our laboratories at constant temperatures of 250°C showing no significant degradation over 2000 hours of operation. Other prototypes were tested at Sandia National Lab in the month of April, 2015 for a third party performance validation. These devices showed outstanding performance over 1000 hours of operation at three rated temperatures, 200°C, 225°C and 250°C, with negligible capacitance degradation and minimal equivalent series resistance (ESR) increase. Similarly, FastCAP’s ruggedized electronics have been proven and commercialized in oil and gas exploration operating to rated temperatures of 150°C. This technology was the basis for the advancements in downhole electronics under this project. Principal contributions here focused on design for manufacture innovations that have reduced the prototype build cycle time by a factor of 10x. The electronics have demonstrated a substantially reduced design cycle time by way of process and material selection innovations and have been qualified for 250°C / 10 Grms for at least 200 hours. FastCAP has also invented a rotary inertial energy generator (RIEG) to harvest various mechanical energy sources that exist downhole. This device is flow-independent and has been demonstrated as a proof of concept to survive geothermal well temperatures under this project. The herein energy harvester has been developed to provide operational power by harvesting rotational mechanical energy that exists downhole in geothermal drilling. The energy harvester has been tested at 250°C / 10 Grms for 200 hours. Deployment of these technologies in geothermal drilling and exploration applications could have an immediate and significant impact on the effectiveness and efficiency of drilling processes, particularly with regard to use of advanced logging and monitoring techniques. The ultimate goal of this work is to reduce drilling risk to make geothermal energy more attractive and viable to the customer. Generally speaking, we aim to support the transfer of MWD techniques from oil and gas to geothermal exploration with considerations toward the practical differences between the two. One of the most significant obstacles to the deployment of advanced drilling and production techniques in the geothermal context are limitations related to the maximum operating temperatures of downhole batteries used to provide power for downhole sensors, steering tools, telemetry equipment and other MWD/LWD technologies. FastCAP’s higher temperature ultracapacitor technology will provide power solutions for similar advanced drilling and production techniques, even in the harsher environments associated with geothermal energy production. This ultracapacitor will enable downhole power solutions for the geothermal industry capable of the same reliable and safe operation our team has demonstrated in the oil and gas context. Without batteries, geothermal MWD is left without a downhole power source. Some very high temperature turbines exist but provide unsteady, intermittent power and no power when the flow is off. In high loss formations common to geothermal exploration, it will be auspicious to support air drilling in which case there is no flow to power a turbine at all. In the best case, rechargeable energy storage will help to buffer unsteady power from non-battery power sources and in the worst case it will be needed to store energy from highly intermittent sources to provide a continuously operable power source to the tool.« less

Turbo-Brayton cryocooler technology for low-temperature space applications

NASA Astrophysics Data System (ADS)

Zagarola, Mark V.; Breedlove, Jeffrey F.; McCormick, John A.; Swift, Walter L.

2003-03-01

High performance, low temperature cryocoolers are being developed for future space-borne telescopes and instruments. To meet mission objectives, these coolers must be compact, lightweight, have low input power, operate reliably for 5-10 years, and produce no disturbances that would affect the pointing accuracy of the instruments. This paper describes progress in the development of turbo-Brayton cryocoolers addressing cooling in the 5 K to 20 K temperature range for loads of up to 300 mW. The key components for these cryocoolers are the miniature, high-speed turbomachines and the high performance recuperative heat exchangers. The turbomachines use gas-bearings to support the low mass, high speed rotors, resulting in negligible vibration and long life. Precision fabrication techniques are used to produce the necessary micro-scale geometric features that provide for high cycle efficiencies at these reduced sizes. Turbo-Brayton cryocoolers for higher temperatures and loads have been successfully developed for space applications. For efficient operation at low temperatures and capacities, advances in the core technologies have been pursued. Performance test results of a new, low poer compressor will be presented, and early cryogenic test results on a low temperature expansion turbine will be discussed. Projections for several low temperature cooler configurations are summarized.

Concept of a Cryogenic System for a Cryogen-Free 25 T Superconducting Magnet

NASA Astrophysics Data System (ADS)

Iwai, Sadanori; Takahashi, Masahiko; Miyazaki, Hiroshi; Tosaka, Taizo; Tasaki, Kenji; Hanai, Satoshi; Ioka, Shigeru; Watanabe, Kazuo; Awaji, Satoshi; Oguro, Hidetoshi

A cryogen-free 25 T superconducting magnet using a ReBCO insert coil that generates 11.5 T in a 14 T background field of outer low-temperature superconducting (LTS) coils is currently under development. The AC loss of the insert coil during field ramping is approximately 8.8 W, which is difficult to dissipate at the operating temperature of the LTS coils (4 K). However, since a ReBCO coil can operate at a temperature above 4 K, the ReBCO insert coil is cooled to about 10 K by two GM cryocoolers, and the LTS coils are independently cooled by two GM/JT cryocoolers. Two GM cryocoolers cool a circulating helium gas through heat exchangers, and the gas is transported over a long distance to the cold stage located on the ReBCO insert coil, in order to protect the cryocoolers from the leakage field of high magnetic fields. The temperature difference of the 2nd cold stage of the GM cryocoolers and the insert coil can be reduced by increasing the gas flow rate. However, at the same time, the heat loss of the heat exchangers increases, and the temperature of the second cold stage is raised. Therefore, the gas flow rate is optimized to minimize the operating temperature of the ReBCO insert coil by using a flow controller and a bypass circuit connected to a buffer tank.

High-speed highly temperature stable 980 nm VCSELs operating at 25 Gb/s at up to 85 °C for short reach optical interconnects

NASA Astrophysics Data System (ADS)

Mutig, Alex; Lott, James A.; Blokhin, Sergey A.; Moser, Philip; Wolf, Philip; Hofmann, Werner; Nadtochiy, Alexey M.; Bimberg, Dieter

2011-03-01

The progressive penetration of optical communication links into traditional copper interconnect markets greatly expands the applications of vertical cavity surface emitting lasers (VCSELs) for the next-generation of board-to-board, moduleto- module, chip-to-chip, and on-chip optical interconnects. Stability of the VCSEL parameters at high temperatures is indispensable for such applications, since these lasers typically reside directly on or near integrated circuit chips. Here we present 980 nm oxide-confined VCSELs operating error-free at bit rates up to 25 Gbit/s at temperatures as high as 85 °C without adjustment of the drive current and peak-to-peak modulation voltage. The driver design is therefore simplified and the power consumption of the driver electronics is lowered, reducing the production and operational costs. Small and large signal modulation experiments at various temperatures from 20 up to 85 °C for lasers with different oxide aperture diameters are presented in order to analyze the physical processes controlling the performance of the VCSELs. Temperature insensitive maximum -3 dB bandwidths of around 13-15 GHz for VCSELs with aperture diameters of 10 μm and corresponding parasitic cut-off frequencies exceeding 22 GHz are observed. Presented results demonstrate the suitability of our VCSELs for practical high speed and high temperature stable short-reach optical links.

Experimental Investigations to evaluate the effects of cutting parameters on cutting temperature and residual stresses during milling process of the AISI 1045

NASA Astrophysics Data System (ADS)

Abdelkrim, M.; Brabie, G.; Belloufi, A.; Catalin, T.; Chirita, B.

2017-08-01

Today major metal cutting companies in industrial countries, looking to gain time and reduce manufacturing costs while respecting the environment. There are many phenomena which affect the quality and production costs of the product, including cutting efforts, cutting temperature, residual stresses, etc. A better understanding of these phenomena will reduce production costs and maximize productivity. The aim of this work is to analyze the effect of machining conditions (cutting speed, feed speed and cutting depth) on cutting temperature and residual stresses, during the milling operations using the response surface method. A good accuracy between predicted and measured values of the cutting temperature was found, the cutting speed and the depth of cut are parameters whose effect is most sensitive to the residual stresses and the cutting temperature.However, little influence has been registered in the case of an increase of the feed rate. The percentage of error is 4.57%, indicating that the numerical approach can accurately predict the cutting temperature of the AISI 1045.

Room temperature CO and H2 sensing with carbon nanoparticles.

PubMed

Kim, Daegyu; Pikhitsa, Peter V; Yang, Hongjoo; Choi, Mansoo

2011-12-02

We report on a shell-shaped carbon nanoparticle (SCNP)-based gas sensor that reversibly detects reducing gas molecules such as CO and H(2) at room temperature both in air and inert atmosphere. Crystalline SCNPs were synthesized by laser-assisted reactions in pure acetylene gas flow, chemically treated to obtain well-dispersed SCNPs and then patterned on a substrate by the ion-induced focusing method. Our chemically functionalized SCNP-based gas sensor works for low concentrations of CO and H(2) at room temperature even without Pd or Pt catalysts commonly used for splitting H(2) molecules into reactive H atoms, while metal oxide gas sensors and bare carbon-nanotube-based gas sensors for sensing CO and H(2) molecules can operate only at elevated temperatures. A pristine SCNP-based gas sensor was also examined to prove the role of functional groups formed on the surface of functionalized SCNPs. A pristine SCNP gas sensor showed no response to reducing gases at room temperature but a significant response at elevated temperature, indicating a different sensing mechanism from a chemically functionalized SCNP sensor.

REDUCING TITANIUM TETRACHLORIDE WITH HIGH-SURFACE SODIUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fleck, D.C.; Wong, M.M.; Baker, D.H. Jr.

1960-01-01

A method of using sodium for reducing titanium tetrachloride, developed to improve the extractive metallurgy of titunium, is described. Finely divided titanium metal, titanium lower chlorides, or a mixture thereof was produced in a continuous operation at temperatures between 105 and 205 deg C by the reaction of molten sodium and vaporized titanium tetrachloride in an agitated bed of finely divided inert solids (powdered sodium chloride or the reaction products). Composition of the product was controlled by varying the relative quantities of sodium and titanium tetrachloride used. A description of the operations and analytical data of the reaction products aremore » given. (auth)« less

Development and test of a 100 kVA superconducting transformer operated at 77 K

NASA Astrophysics Data System (ADS)

Kummeth, P.; Schlosser, R.; Massek, P.; Schmidt, H.; Albrecht, C.; Breitfelder, D.; Neumüller, H.-W.

2000-05-01

High-temperature superconducting (HTS) transformers are very promising candidates for application in electrical power engineering. Their main advantages are reduced size, weight, better efficiency and reduced potential fire and environmental hazards. We have designed, constructed and tested a 100 kVA HTS power transformer operated at 77 K. The nominal primary and secondary currents (voltages) are 18 A (5.6 kV) and 92 A (1.1 kV), respectively. No-load tests, short-circuit tests and load tests proved repeatedly that the transformer has the rated capacity. HTS winding losses of 20.6 W and iron losses of 403 W were measured.

Actively driven thermal radiation shield

DOEpatents

Madden, Norman W.; Cork, Christopher P.; Becker, John A.; Knapp, David A.

2002-01-01

A thermal radiation shield for cooled portable gamma-ray spectrometers. The thermal radiation shield is located intermediate the vacuum enclosure and detector enclosure, is actively driven, and is useful in reducing the heat load to mechanical cooler and additionally extends the lifetime of the mechanical cooler. The thermal shield is electrically-powered and is particularly useful for portable solid-state gamma-ray detectors or spectrometers that dramatically reduces the cooling power requirements. For example, the operating shield at 260K (40K below room temperature) will decrease the thermal radiation load to the detector by 50%, which makes possible portable battery operation for a mechanically cooled Ge spectrometer.

OM300 Direction Drilling Module

DOE Data Explorer

MacGugan, Doug

2013-08-22

OM300 – Geothermal Direction Drilling Navigation Tool: Design and produce a prototype directional drilling navigation tool capable of high temperature operation in geothermal drilling Accuracies of 0.1° Inclination and Tool Face, 0.5° Azimuth Environmental Ruggedness typical of existing oil/gas drilling Multiple Selectable Sensor Ranges High accuracy for navigation, low bandwidth High G-range & bandwidth for Stick-Slip and Chirp detection Selectable serial data communications Reduce cost of drilling in high temperature Geothermal reservoirs Innovative aspects of project Honeywell MEMS* Vibrating Beam Accelerometers (VBA) APS Flux-gate Magnetometers Honeywell Silicon-On-Insulator (SOI) High-temperature electronics Rugged High-temperature capable package and assembly process

Performance of Air-cooled Engine Cylinders Using Blower Cooling

NASA Technical Reports Server (NTRS)

Schey, Oscar W; Ellerbrock, Herman H , Jr

1936-01-01

An investigation was made to obtain information on the minimum quantity of air and power required to cool conventional air cooled cylinders at various operating conditions when using a blower. The results of these tests show that the minimum power required for satisfactory cooling with an overall blower efficiency of 100 percent varied from 2 to 6 percent of the engine power depending on the operating conditions. The shape of the jacket had a large effect on the cylinder temperatures. Increasing the air speed over the front of the cylinder by keeping the greater part of the circumference of the cylinder covered by the jacket reduced the temperatures over the entire cylinder.

A Curious Year on Mars - Long-Term Thermal Trends for Mars Science Laboratory Rover's First Martian Year

NASA Technical Reports Server (NTRS)

Cucullu, Gordy C., III; Zayas, Daniel; Novak, Keith; Wu, Pat

2014-01-01

By the time of this writing, Curiosity, the Mars Science Laboratory (MSL) Rover, has weathered four seasons in Gale Crater, just south of and approaching the foothills of the 5-km high Aeolis Mons, known as "Mount Sharp," at 4.59 deg south latitude. The mission design included a much broader latitude range of 30 deg north to 30 deg south constraining some of the Rover environmental requirements and operations. To date, Curiosity has relayed over 150 MB of thermal telemetry. Curiosity has relayed over 150 MB of thermal telemetry through four seasons. The trends and idiosyncrasies revealed through four seasons of telemetry from Mars are discussed. The better-characterized thermal environment allows for less conservatism in operational models and increases the amount of science data collection. Examples include: the elimination of overheating concerns for some cameras and the use of the previous sol's temperature telemetry along with the conservative soak temperature curve from the winter thermal model, to produce a custom heating prescription for the upcoming weeks thus increasing operation time and reducing heating times. This paper discusses the lessons learned for Rover operation as well as general idiosyncrasies discovered about the local environment-such as the effect of orientation on subsystem temperature variation, a regular morning and afternoon wind, ground and air microclimates with distinct temperature differences from other terrain, and how the Rover affects the local environment. This paper further documents and explains some of the interesting highs and lows of the temperature telemetry data as well as offers explanations for sudden temperature changes on board the Rover.

Conceptual design and integration of a space station resistojet propulsion assembly

NASA Technical Reports Server (NTRS)

Tacina, Robert R.

1987-01-01

The resistojet propulsion module is designed as a simple, long life, low risk system offering operational flexibility to the space station program. It can dispose of a wide variety of typical space station waste fluids by using them as propellants for orbital maintenance. A high temperature mode offers relatively high specific impulse with long life while a low temperature mode can propulsively dispose of mixtures that contain oxygen or hydrocarbons without reducing thruster life or generating particulates in the plume. A low duty cycle and a plume that is confined to a small aft region minimizes the impacts on the users. Simple interfaces with other space station systems facilitate integration. It is concluded that there are no major obstacles and many advantages to developing, installing, and operating a resistojet propulsion module aboard the Initial Operational Capability (IOC) space station.

Effect of fabrication process on physical and mechanical properties of tungsten carbide - cobalt composite: A review

NASA Astrophysics Data System (ADS)

Mahaidin, Ahmad Aswad; Jaafar, Talib Ria; Selamat, Mohd Asri; Budin, Salina; Sulaiman, Zaim Syazwan; Hamid, Mohamad Hasnan Abdul

2017-12-01

WC-Co, which is also known as cemented carbide, is widely used in metal cutting industry and wear related application due to their excellent mechanical properties. Manufacturing industries are focusing on improving productivity and reducing operational cost with machining operation is considered as one of the factors. Thus, machining conditions are becoming more severe and required better cutting tool bit with improved mechanical properties to withstand high temperature operation. Numerous studies have been made over the generation for further improvement of cemented carbide properties to meet the constant increase in demand. However, the results of these studies vary due to different process parameters and manufacturing technology. This paper summarizes the studies to improve the properties of WC-Co composite using different consolidation (powder size, mixing method, formulation, etc) and sintering parameters (temperature, time, atmosphere, etc).

Capillary Limit in a Loop Heat Pipe with Dual Evaporators

NASA Technical Reports Server (NTRS)

Ku, Jentung; Birur, Gajanana; Obenschain, Arthur F. (Technical Monitor)

2002-01-01

This paper describes a study on the capillary limit of a loop heat pipe (LHP) with two evaporators and two condensers. Both theoretical analysis and experimental investigation are conducted. Tests include heat load to one evaporator only, even heat loads to both evaporators and uneven heat load to both evaporators. Results show that after the capillary limit is exceeded, vapor will penetrate through the wick of the weaker evaporator and the compensation chamber (CC) of that evaporator will control the loop operating temperature regardless of which CC has been in control prior to the event Because the evaporator can tolerate vapor bubbles, the loop may continue to work and reach a new steady state at a higher operating temperature. The loop may even function with a modest increase in the heat load past the capillary limit With a heat load to only one evaporator, the capillary limit can be identified by rapid increases in the operating temperature and in the temperature difference between the evaporator and the CC. However, it is more difficult to tell when the capillary limit is exceeded if heat loads are applied to both evaporators. In all cases, the loop can recover by reducing the heat load to the loop.

Mesoscale Elucidation of Surface Passivation in the Li–Sulfur Battery Cathode

DOE PAGES

Liu, Zhixiao; Mukherjee, Partha P.

2017-01-23

We report the cathode surface passivation caused by Li 2S precipitation adversely affects the performance of lithium-sulfur (Li-S) batteries. Li 2S precipitation is a complicated mesoscale process involving adsorption, desorption and diffusion kinetics, which are affected profoundly by the reactant concentration and operating temperature. In this work, a mesoscale interfacial model is presented to study the growth of Li 2S film on carbon cathode surface. Li 2S film growth experiences nucleation, isolated Li 2S island growth and island coalescence. The slow adsorption rate at small S 2- concentration inhibits the formation of nucleation seeds and the lateral growth of Limore » 2S islands, which deters surface passivation. An appropriate operating temperature, especially in the medium-to-high temperature range, can also defer surface passivation. Fewer Li 2S nucleation seeds form in such an operating temperature range, which facilitates heterogeneous growth and thereby inhibits the lateral growth of the Li 2S film, which may also result in reduced surface passivation. Finally, the high specific surface area of the cathode microstructure is expected to mitigate the surface passivation.« less

Development of a Thin Film Primary Surface Heat Exchanger for Advanced Power Cycles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allison, Tim; Beck, Griffin; Bennett, Jeffrey

This project objective is to develop a high-temperature design upgrade for an existing primary surface heat exchanger so that the redesigned hardware is capable of operation in CO 2 at temperatures up to 1,510°F (821°C) and pressure differentials up to 130 psi (9 bar). The heat exchanger is proposed for use as a recuperator in an advanced low-pressure oxy-fuel Brayton cycle that is predicted to achieve over 50% thermodynamic efficiency, although the heat exchanger could also be used in other high-temperature, low-differential pressure cycles. This report describes the progress to date, which includes continuing work performed to select and testmore » new candidate materials for the recuperator redesign, final mechanical and thermal performance analysis results of various redesign concepts, and the preliminary design of a test loop for the redesigned recuperator including a budgetary estimate for detailed test loop design, procurement, and test operation. A materials search was performed in order to investigate high-temperature properties of many candidate materials, including high-temperature strength and nickel content. These properties were used to rank the candidate materials, resulting in a reduced list of nine materials for corrosion testing. Multiple test rigs were considered and analyzed for short-term corrosion testing and Thermal Gravimetric Analysis (TGA) was selected as the most cost-effective option for evaluating corrosion resistance of the candidate materials. In addition, tantalum, niobium, and chromium coatings were identified as potential options for increased corrosion resistance. The test results show that many materials exhibit relatively low weight gain rates, and that niobium and tantalum coatings may improve corrosion resistance for many materials, while chromium coatings appear to oxidize and debond quickly. Metallurgical analysis of alloys was also performed, showing evidence of intergranular attack in 282 that may cause long-term reliability problems in CO 2 service at these temperatures. However, long-term testing in a flowing environment is recommended in order to understand accurately the severity of the attack. Detailed economic modeling of the existing air cycle recuperator and CO 2 cycle recuperator options was also completed, including costs for material, fabrication, fuel, maintenance, and operation. The analysis results show that the increased capital cost for high-temperature materials may be offset by higher cycle efficiencies, decreasing the overall lifetime cost of the system. The economic analysis also examines costs associated with increased pressure drop and material changes for two redesign options. These results show that, even with slightly reduced performance and/or higher material costs, the lifetime cost per energy production may still be reduced by over 12%. The existing recuperator design information was provided by Solar Turbines, Inc. via several models, drawings, and design handoff meetings. Multiple fluid/thermal and structural models were created in order to analyze critical recuperator performance and mechanical strength in critical areas throughout the redesign process. These models were analyzed for a baseline condition (consistent with current Mercury 50 operation) for validation purposes. Results are presented for heat transfer coefficients and pressure drops, matching well with the existing operational data. Simulation of higher-temperature CO 2 conditions was also performed, showing a slight expected increase in both heat transfer and pressure drop. Mechanical analysis results for critical areas on the cross-flow and counter-flow sheets have also been obtained for air and CO 2 cases. These results show similar stresses in both cases but significantly reduced safety factors for the CO 2 case due to reduced yield and creep rupture strengths of alloy 625 at the higher temperatures. A concept brainstorm session and initial down-selection were completed in order to identify promising redesign options for further analysis. Detailed analysis of all promising redesign options was performed via finite element and computational fluid dynamic simulations in order to characterize mechanical and thermal-fluid performance of each option. These options included material change, various sheet thickness configurations, pitch and phasing of cross-flow and counter-flow sheets, and separator sheets. The analysis results have identified two viable redesign options that maintain existing safety margins optimally through a material change to Haynes 282 and (A) sheet thickness increases of 40% on the counter-flow sheet and 75% on the hot side cross-flow corrugation sheet or (B) addition of a separator sheet in the counter-flow section while maintaining the original counter-flow sheet thickness and increasing the cross-flow corrugation sheet thickness by 90% to account for the increase in cell height. While both options satisfy mechanical stress constraints, the separator sheet design has a higher part count, slightly reduced heat transfer, and slightly higher pressure drop than the first option and is not preferred. Finally, several test loop concepts have been developed for different full-scale and reduced-scale recuperator testing options. For each option, various loop components, such as heat exchangers, valves, heaters, and compressors, were evaluated in an effort to maximize utilization of existing resources. All concepts utilize an existing 3-MW CO 2 compressor, heater, and loop coolers, but the concepts vary by incorporating different amounts of new equipment for achieving various flow rates (all concepts operate at design pressure and temperature). The third concept achieves a 1 kg/s test without purchasing any costly equipment (coolers, heaters, blowers, etc.). Since the stacked cell design of the recuperator results in the same flow conditions at each core cell (even for a reduced-scale test). Thus, test loop Concept #3 was selected for the preliminary design. This loop design is detailed within the report, culminating in a budgetary estimate of $1,013,000.00 for the detailed design, construction, commissioning, and operation of a high-temperature recuperator test loop.« less

Impact of operating conditions on the acetylene contamination in the cathode of proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Zhai, Yunfeng; St-Pierre, Jean

2017-12-01

Realistically, proton exchange membrane fuel cells (PEMFCs) are operated under varying operating conditions that potentially impact the acetylene contamination reactions. In this paper, the effects of the cell operating conditions on the acetylene contamination in PEMFCs are investigated under different current densities and temperatures with different acetylene concentrations in the cathode. Electrochemical impedance spectroscopy is applied during the constant-current operation to analyze the impacts of the operating conditions on the acetylene electrochemical reactions. The experimental results indicate that higher acetylene concentrations, higher current densities and lower cell temperatures decrease the cell performance more. In particular, cathode poisoning becomes more severe at medium cell current densities. The cell cathode potentials at such current densities are not sufficient to completely oxidize the intermediate or sufficiently low to completely reduce the adsorbed acetylene. Based on these investigations, the possible condition-dependent limitations of the acetylene concentration and cell operating voltage are proposed for insight into the acetylene contamination mitigation stratagem. Regarding the barrier conditions, the acetylene reactions change abruptly, and adjusting the cell operation parameters to change the acetylene adsorbate and intermediate accumulation conditions to induce complete oxidation or reduction conditions may mitigate the severe acetylene contamination effects on PEMFCs.

Close-Spaced High Temperature Knudsen Flow.

DTIC Science & Technology

1986-07-15

work~was a study of discharge processes in Knudsen mode (collisionless), thermionic energy converters. Areas of research involve’mechanisms for reducing ...power densities. The mechanisms/we have chosen to study are: reduction of space-charge through a very close interelectrode gap (less than 10 microns...In order to operate at practical current densities, the effect of electron space charge must be reduced . This can be done through very close

Building America Case Study: Boiler Control Replacement for Hydronically Heated Multifamily Buildings, Cambridge, Massachusetts (Fact Sheet)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

2014-11-01

The ARIES Collaborative, a U.S. Department of Energy Building America research team, partnered with NeighborWorks America affiliate Homeowners' Rehab Inc. (HRI) of Cambridge, Massachusetts, to study improvements to the central hydronic heating system in one of the nonprofit's housing developments. The heating controls in the three-building, 42-unit Columbia Cambridge Alliance for Spanish Tenants housing development were upgraded. Fuel use in the development was excessive compared to similar properties. A poorly insulated thermal envelope contributed to high energy bills, but adding wall insulation was not cost-effective or practical. The more cost-effective option was improving heating system efficiency. Efficient operation of themore » heating system faced several obstacles, including inflexible boiler controls and failed thermostatic radiator valves. Boiler controls were replaced with systems that offer temperature setbacks and one that controls heat based on apartment temperature in addition to outdoor temperature. Utility bill analysis shows that post-retrofit weather-normalized heating energy use was reduced by 10%-31% (average of 19%). Indoor temperature cutoff reduced boiler runtime (and therefore heating fuel consumption) by 28% in the one building in which it was implemented. Nearly all savings were obtained during night which had a lower indoor temperature cut off (68 degrees F) than day (73 degrees F). This implies that the outdoor reset curve was appropriately adjusted for this building for daytime operation. Nighttime setback of heating system supply water temperature had no discernable impact on boiler runtime or gas bills.« less

Evaluation of Ceramic Matrix Composite Technology for Aircraft Turbine Engine Applications

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Jaskowiak, Martha H.; Kiser, James D.; Zhu, Dongming

2013-01-01

The goals of the NASA Environmentally Responsible Aviation (ERA) Project are to reduce the NO(x) emissions, fuel burn, and noise from turbine engines. In order to help meet these goals, commercially-produced ceramic matrix composite (CMC) components and environmental barrier coatings (EBCs) are being evaluated as parts and panels. The components include a CMC combustor liner, a CMC high pressure turbine vane, and a CMC exhaust nozzle as well as advanced EBCs that are tailored to the operating conditions of the CMC combustor and vane. The CMC combustor (w/EBC) could provide 2700 F temperature capability with less component cooling requirements to allow for more efficient combustion and reductions in NOx emissions. The CMC vane (w/EBC) will also have temperature capability up to 2700 F and allow for reduced fuel burn. The CMC mixer nozzle will offer reduced weight and improved mixing efficiency to provide reduced fuel burn. The main objectives are to evaluate the manufacturability of the complex-shaped components and to evaluate their performance under simulated engine operating conditions. Progress in CMC component fabrication, evaluation, and testing is presented in which the goal is to advance from the proof of concept validation (TRL 3) to a system/subsystem or prototype demonstration in a relevant environment (TRL 6).

Simultaneous Assimilation of AMSR-E Brightness Temperature and MODIS LST to Improve Soil Moisture with Dual Ensemble Kalman Smoother

NASA Astrophysics Data System (ADS)

Huang, Chunlin; Chen, Weijin; Wang, Weizhen; Gu, Juan

2017-04-01

Uncertainties in model parameters can easily cause systematic differences between model states and observations from ground or satellites, which significantly affect the accuracy of soil moisture estimation in data assimilation systems. In this paper, a novel soil moisture assimilation scheme is developed to simultaneously assimilate AMSR-E brightness temperature (TB) and MODIS Land Surface Temperature (LST), which can correct model bias by simultaneously updating model states and parameters with dual ensemble Kalman filter (DEnKS). The Common Land Model (CoLM) and a Q-h Radiative Transfer Model (RTM) are adopted as model operator and observation operator, respectively. The assimilation experiment is conducted in Naqu, Tibet Plateau, from May 31 to September 27, 2011. Compared with in-situ measurements, the accuracy of soil moisture estimation is tremendously improved in terms of a variety of scales. The updated soil temperature by assimilating MODIS LST as input of RTM can reduce the differences between the simulated and observed brightness temperatures to a certain degree, which helps to improve the estimation of soil moisture and model parameters. The updated parameters show large discrepancy with the default ones and the former effectively reduces the states bias of CoLM. Results demonstrate the potential of assimilating both microwave TB and MODIS LST to improve the estimation of soil moisture and related parameters. Furthermore, this study also indicates that the developed scheme is an effective soil moisture downscaling approach for coarse-scale microwave TB.

Water cycle and its management for plant habitats at reduced pressures

NASA Technical Reports Server (NTRS)

Rygalov, Vadim Y.; Fowler, Philip A.; Wheeler, Raymond M.; Bucklin, Ray A.

2004-01-01

Experimental and mathematical models were developed for describing and testing temperature and humidity parameters for plant production in bioregenerative life support systems. A factor was included for analyzing systems operating at low (10-101.3 kPa) pressure to reduce gas leakage and structural mass (e.g., inflatable greenhouses for space application). The expected close relationship between temperature and relative humidity was observed, along with the importance of heat exchanger coil temperature and air circulation rate. The presence of plants in closed habitats results in increased water flux through the system. Changes in pressure affect gas diffusion rates and surface boundary layers, and change convective transfer capabilities and water evaporation rates. A consistent observation from studies with plants at reduced pressures is increased evapotranspiration rates, even at constant vapor pressure deficits. This suggests that plant water status is a critical factor for managing low-pressure production systems. The approach suggested should help space mission planners design artificial environments in closed habitats.

Power control electronics for cryogenic instrumentation

NASA Technical Reports Server (NTRS)

Ray, Biswajit; Gerber, Scott S.; Patterson, Richard L.; Myers, Ira T.

1995-01-01

In order to achieve a high-efficiency high-density cryogenic instrumentation system, the power processing electronics should be placed in the cold environment along with the sensors and signal-processing electronics. The typical instrumentation system requires low voltage dc usually obtained from processing line frequency ac power. Switch-mode power conversion topologies such as forward, flyback, push-pull, and half-bridge are used for high-efficiency power processing using pulse-width modulation (PWM) or resonant control. This paper presents several PWM and multiresonant power control circuits, implemented using commercially available CMOS and BiCMOS integrated circuits, and their performance at liquid-nitrogen temperature (77 K) as compared to their room temperature (300 K) performance. The operation of integrated circuits at cryogenic temperatures results in an improved performance in terms of increased speed, reduced latch-up susceptibility, reduced leakage current, and reduced thermal noise. However, the switching noise increased at 77 K compared to 300 K. The power control circuits tested in the laboratory did successfully restart at 77 K.

Thermoelectric properties and performance of flexible reduced graphene oxide films up to 3,000 K

NASA Astrophysics Data System (ADS)

Li, Tian; Pickel, Andrea D.; Yao, Yonggang; Chen, Yanan; Zeng, Yuqiang; Lacey, Steven D.; Li, Yiju; Wang, Yilin; Dai, Jiaqi; Wang, Yanbin; Yang, Bao; Fuhrer, Michael S.; Marconnet, Amy; Dames, Chris; Drew, Dennis H.; Hu, Liangbing

2018-02-01

The development of ultrahigh-temperature thermoelectric materials could enable thermoelectric topping of combustion power cycles as well as extending the range of direct thermoelectric power generation in concentrated solar power. However, thermoelectric operation temperatures have been restricted to under 1,500 K due to the lack of suitable materials. Here, we demonstrate a thermoelectric conversion material based on high-temperature reduced graphene oxide nanosheets that can perform reliably up to 3,000 K. After a reduction treatment at 3,300 K, the nanosheet film exhibits an increased conductivity to 4,000 S cm-1 at 3,000 K and a high power factor S2σ = 54.5 µW cm-1 K-2. We report measurements characterizing the film's thermoelectric properties up to 3,000 K. The reduced graphene oxide film also exhibits a high broadband radiation absorbance and can act as both a radiative receiver and a thermoelectric generator. The printable, lightweight and flexible film is attractive for system integration and scalable manufacturing.

Water cycle and its management for plant habitats at reduced pressures.

PubMed

Rygalov, Vadim Y; Fowler, Philip A; Wheeler, Raymond M; Bucklin, Ray A

2004-01-01

Experimental and mathematical models were developed for describing and testing temperature and humidity parameters for plant production in bioregenerative life support systems. A factor was included for analyzing systems operating at low (10-101.3 kPa) pressure to reduce gas leakage and structural mass (e.g., inflatable greenhouses for space application). The expected close relationship between temperature and relative humidity was observed, along with the importance of heat exchanger coil temperature and air circulation rate. The presence of plants in closed habitats results in increased water flux through the system. Changes in pressure affect gas diffusion rates and surface boundary layers, and change convective transfer capabilities and water evaporation rates. A consistent observation from studies with plants at reduced pressures is increased evapotranspiration rates, even at constant vapor pressure deficits. This suggests that plant water status is a critical factor for managing low-pressure production systems. The approach suggested should help space mission planners design artificial environments in closed habitats.

The Mauna Kea Weather Center: Custom Atmospheric Forecasting Support for Mauna Kea

NASA Astrophysics Data System (ADS)

Businger, Steven

2011-03-01

The success of operations at Mauna Kea Observatories is strongly influenced by weather conditions. The Mauna Kea Weather Center, an interdisciplinary research program, was established in 1999 to develop and provide custom weather support for Mauna Kea Observatories. The operational forecasting goals of the program are to facilitate the best possible use of favorable atmospheric conditions for scientific benefit and to ensure operational safety. During persistent clear periods, astronomical observing quality varies substantially due to changes in the vertical profiles of temperature, wind, moisture, and turbulence. Cloud and storm systems occasionally cause adverse or even hazardous conditions. A dedicated, daily, real-time mesoscale numerical modeling effort provides crucial forecast guidance in both cases. Several key atmospheric variables are forecast with sufficient skill to be of operational and scientific benefit to the telescopes on Mauna Kea. Summit temperature forecasts allow mirrors to be set to the ambient temperature to reduce image distortion. Precipitable water forecasts allow infrared observations to be prioritized according to atmospheric opacity. Forecasts of adverse and hazardous conditions protect the safety of personnel and allow for scheduling of maintenance when observing is impaired by cloud. The research component of the project continues to improve the accuracy and content of the forecasts. In particular, case studies have resulted in operational forecasts of astronomical observing quality, or seeing.

Final Technical Report - 300°C Capable Electronics Platform and Temperature Sensor System For Enhanced Geothermal Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Cheng-Po; Shaddock, David; Sandvik, Peter

2012-11-30

A silicon carbide (SiC) based electronic temperature sensor prototype has been demonstrated to operate at 300°C. We showed continuous operation of 1,000 hours with SiC operational amplifier and surface mounted discreet resistors and capacitors on a ceramic circuit board. This feasibility demonstration is a major milestone in the development of high temperature electronics in general and high temperature geothermal exploration and well management tools in particular. SiC technology offers technical advantages that are not found in competing technologies such as silicon-on-insulator (SOI) at high temperatures of 200°C to 300°C and beyond. The SiC integrated circuits and packaging methods can bemore » used in new product introduction by GE Oil and Gas for high temperature down-hole tools. The existing SiC fabrication facility at GE is sufficient to support the quantities currently demanded by the marketplace, and there are other entities in the United States and other countries capable of ramping up SiC technology manufacturing. The ceramic circuit boards are different from traditional organic-based electronics circuit boards, but the fabrication process is compatible with existing ceramic substrate manufacturing. This project has brought high temperature electronics forward, and brings us closer to commercializing tools that will enable and reduce the cost of enhanced geothermal technology to benefit the public in terms of providing clean renewable energy at lower costs.« less

Noise thermometry at ultra-low temperatures.

PubMed

Rothfuss, D; Reiser, A; Fleischmann, A; Enss, C

2016-03-28

The options for primary thermometry at ultra-low temperatures are rather limited. In practice, most laboratories are using (195)Pt NMR thermometers in the microkelvin range. In recent years, current sensing direct current superconducting quantum interference devices (DC-SQUIDs) have enabled the use of noise thermometry in this temperature range. Such devices have also demonstrated the potential for primary thermometry. One major advantage of noise thermometry is the fact that no driving current is needed to operate the device and thus the heat dissipation within the thermometer can be reduced to a minimum. Ultimately, the intrinsic power dissipation is given by the negligible back action of the readout SQUID. For thermometry in low-temperature experiments, current noise thermometers and magnetic flux fluctuation thermometers have proved to be most suitable. To make use of such thermometers at ultra-low temperatures, we have developed a cross-correlation technique that reduces the amplifier noise contribution to a negligible value. For this, the magnetic flux fluctuations caused by the Brownian motion of the electrons in our noise source are measured inductively by two DC-SQUID magnetometers simultaneously and the signals from these two channels are cross-correlated. Experimentally, we have characterized a thermometer made of a cold-worked high-purity copper cylinder with a diameter of 5 mm and a length of 20 mm for temperatures between 42 μK and 0.8 K. For a given temperature, a measuring time below 1 min is sufficient to reach a precision of better than 1%. The extremely low power dissipation in the thermometer allows continuous operation without heating effects. © 2016 The Author(s).

CFD analysis of a full-scale ceramic kiln module under actual operating conditions

NASA Astrophysics Data System (ADS)

Milani, Massimo; Montorsi, Luca; Stefani, Matteo; Venturelli, Matteo

2017-11-01

The paper focuses on the CFD analysis of a full-scale module of an industrial ceramic kiln under actual operating conditions. The multi-dimensional analysis includes the real geometry of a ceramic kiln module employed in the preheating and firing sections and investigates the heat transfer between the tiles and the burners' flame as well as the many components that comprise the module. Particular attention is devoted to the simulation of the convective flow field in the upper and lower chambers and to the effects of radiation on the different materials is addressed. The assessment of the radiation contribution to the tiles temperature is paramount to the improvement of the performance of the kiln in terms of energy efficiency and fuel consumption. The CFD analysis is combined to a lumped and distributed parameter model of the entire kiln in order to simulate the module behaviour at the boundaries under actual operating conditions. Finally, the CFD simulation is employed to address the effects of the module operating conditions on the tiles' temperature distribution in order to improve the temperature uniformity as well as to enhance the energy efficiency of the system and thus to reduce the fuel consumption.

The effect of energy accumulation and boundary slip on laminar flow between rotating plates

NASA Astrophysics Data System (ADS)

Wu, Zhenpeng; Zeng, Liangcai; Chen, Keying; Jin, Xiaohong; Wu, Shiqian

2018-02-01

The poor operating conditions of fluid lubrication equipment during the start-up process are due to the resistance of the high-viscosity lubricating liquid. Moreover, the excessive reduction in fluid viscosity due to the elevated temperature resulting from power consumption during prolonged operation is not conducive to the generation of dynamic pressure. In this study, we examine the effect of energy accumulation and boundary slip on the laminar flow of a liquid between a pair of rotating plates. The experiments are conducted using a rotary rheometer, with polymethyl methacrylate (PMMA) as the thermal insulation material and polytetrafluoroethylene (PTFE) as the slip drag reduction material, and a three-dimensional simulation model is established. This model is derived by combining the energy equation including the slip length and the heat conduction equation. Thus, the temperature changes over time are predicted by this model, and the model accuracy is verified by experiments. The results reveal the following points: 1) boundary slips function as a drag reduction mechanism for short-time continuous operation; 2) under prolonged operation, the slip reduces the extent of the oil viscosity decrease and clear control of the elevated temperature by the boundary slip is observed.

Optimisation of the supercritical extraction of toxic elements in fish oil.

PubMed

Hajeb, P; Jinap, S; Shakibazadeh, Sh; Afsah-Hejri, L; Mohebbi, G H; Zaidul, I S M

2014-01-01

This study aims to optimise the operating conditions for the supercritical fluid extraction (SFE) of toxic elements from fish oil. The SFE operating parameters of pressure, temperature, CO2 flow rate and extraction time were optimised using a central composite design (CCD) of response surface methodology (RSM). High coefficients of determination (R²) (0.897-0.988) for the predicted response surface models confirmed a satisfactory adjustment of the polynomial regression models with the operation conditions. The results showed that the linear and quadratic terms of pressure and temperature were the most significant (p < 0.05) variables affecting the overall responses. The optimum conditions for the simultaneous elimination of toxic elements comprised a pressure of 61 MPa, a temperature of 39.8ºC, a CO₂ flow rate of 3.7 ml min⁻¹ and an extraction time of 4 h. These optimised SFE conditions were able to produce fish oil with the contents of lead, cadmium, arsenic and mercury reduced by up to 98.3%, 96.1%, 94.9% and 93.7%, respectively. The fish oil extracted under the optimised SFE operating conditions was of good quality in terms of its fatty acid constituents.

Thermal Analysis and Correlation of the Mars Odyssey Spacecraft's Solar Array During Aerobraking Operations

NASA Technical Reports Server (NTRS)

Dec, John A.; Gasbarre, Joseph F.; George, Benjamin E.

2002-01-01

The Mars Odyssey spacecraft made use of multipass aerobraking to gradually reduce its orbit period from a highly elliptical insertion orbit to its final science orbit. Aerobraking operations provided an opportunity to apply advanced thermal analysis techniques to predict the temperature of the spacecraft's solar array for each drag pass. Odyssey telemetry data was used to correlate the thermal model. The thermal analysis was tightly coupled to the flight mechanics, aerodynamics, and atmospheric modeling efforts being performed during operations. Specifically, the thermal analysis predictions required a calculation of the spacecraft's velocity relative to the atmosphere, a prediction of the atmospheric density, and a prediction of the heat transfer coefficients due to aerodynamic heating. Temperature correlations were performed by comparing predicted temperatures of the thermocouples to the actual thermocouple readings from the spacecraft. Time histories of the spacecraft relative velocity, atmospheric density, and heat transfer coefficients, calculated using flight accelerometer and quaternion data, were used to calculate the aerodynamic heating. During aerobraking operations, the correlations were used to continually update the thermal model, thus increasing confidence in the predictions. This paper describes the thermal analysis that was performed and presents the correlations to the flight data.

ZnO nanorod arrays and direct wire bonding on GaN surfaces for rapid fabrication of antireflective, high-temperature ultraviolet sensors

NASA Astrophysics Data System (ADS)

So, Hongyun; Senesky, Debbie G.

2016-11-01

Rapid, cost-effective, and simple fabrication/packaging of microscale gallium nitride (GaN) ultraviolet (UV) sensors are demonstrated using zinc oxide nanorod arrays (ZnO NRAs) as an antireflective layer and direct bonding of aluminum wires to the GaN surface. The presence of the ZnO NRAs on the GaN surface significantly reduced the reflectance to less than 1% in the UV and 4% in the visible light region. As a result, the devices fabricated with ZnO NRAs and mechanically stable aluminum bonding wires (pull strength of 3-5 gf) showed higher sensitivity (136.3% at room temperature and 148.2% increase at 250 °C) when compared with devices with bare (uncoated) GaN surfaces. In addition, the devices demonstrated reliable operation at high temperatures up to 300 °C, supporting the feasibility of simple and cost-effective UV sensors operating with higher sensitivity in high-temperature conditions, such as in combustion, downhole, and space exploration applications.

Minimum maximum temperature gradient coil design.

PubMed

While, Peter T; Poole, Michael S; Forbes, Larry K; Crozier, Stuart

2013-08-01

Ohmic heating is a serious problem in gradient coil operation. A method is presented for redesigning cylindrical gradient coils to operate at minimum peak temperature, while maintaining field homogeneity and coil performance. To generate these minimaxT coil windings, an existing analytic method for simulating the spatial temperature distribution of single layer gradient coils is combined with a minimax optimization routine based on sequential quadratic programming. Simulations are provided for symmetric and asymmetric gradient coils that show considerable improvements in reducing maximum temperature over existing methods. The winding patterns of the minimaxT coils were found to be heavily dependent on the assumed thermal material properties and generally display an interesting "fish-eye" spreading of windings in the dense regions of the coil. Small prototype coils were constructed and tested for experimental validation and these demonstrate that with a reasonable estimate of material properties, thermal performance can be improved considerably with negligible change to the field error or standard figures of merit. © 2012 Wiley Periodicals, Inc.

Development of intermediate temperature sodium nickel chloride rechargeable batteries using conventional polymer sealing technologies

NASA Astrophysics Data System (ADS)

Chang, Hee Jung; Lu, Xiaochuan; Bonnett, Jeff F.; Canfield, Nathan L.; Son, Sori; Park, Yoon-Cheol; Jung, Keeyoung; Sprenkle, Vincent L.; Li, Guosheng

2017-04-01

Developing advanced and reliable electrical energy storage systems is critical to fulfill global energy demands and stimulate the growth of renewable energy resources. Sodium metal halide batteries have been under serious consideration as a low cost alternative energy storage device for stationary energy storage systems. Yet, there are number of challenges to overcome for the successful market penetration, such as high operating temperature and hermetic sealing of batteries that trigger an expensive manufacturing process. Here we demonstrate simple, economical and practical sealing technologies for Na-NiCl2 batteries operated at an intermediate temperature of 190 °C. Conventional polymers are implemented in planar Na-NiCl2 batteries after a prescreening test, and their excellent compatibilities and durability are demonstrated by a stable performance of Na-NiCl2 battery for more than 300 cycles. The sealing methods developed in this work will be highly beneficial and feasible for prolonging battery cycle life and reducing manufacturing cost for Na-based batteries at elevated temperatures (<200 °C).

Effects of broadened property fuels on radiant heat flux to gas turbine combustor liners

NASA Technical Reports Server (NTRS)

Haggard, J. B., Jr.

1983-01-01

The effects of fuel type, inlet air pressure, inlet air temperature, and fuel/air ratio on the combustor radiation were investigated. Combustor liner radiant heat flux measurements were made in the spectral region between 0.14 and 6.5 microns at three locations in a modified commercial aviation can combustor. Two fuels, Jet A and a heavier distillate research fuel called ERBS were used. The use of ERBS fuel as opposed to Jet A under similar operating conditions resulted in increased radiation to the combustor liner and hence increased backside liner temperature. This increased radiation resulted in liner temperature increases always less than 73 C. The increased radiation is shown by way of calculations to be the result of increased soot concentrations in the combustor. The increased liner temperatures indicated can substantially affect engine maintenance costs by reducing combustor liner life up to 1/3 because of the rapid decay in liner material properties when operated beyond their design conditions.

WF/PC internal molecular contamination during system thermal-vacuum test

NASA Technical Reports Server (NTRS)

Taylor, Daniel M.; Barengoltz, J.; Jenkins, T.; Leschly, K.; Triolo, J.

1988-01-01

During the recent system thermal vacuum test of the Wide-Field/Planetary Camera (WF/PC), instrumentation was added to the WF/PC to characterize the internal molecular contamination and verify the instrument throughput down to 1470 angstroms. Analysis of data elements revealed two contaminants affecting the far-ultraviolet (FUV) performance of the WF/PC. The one contaminant (heavy volatile) is correlated with the electronic and housing temperature, and the contamination is significantly reduced when the electronics are operated below plus 8 degrees to plus 10 degrees C. The other contaminant (light volatile) is controlled by the heat pipe temperature, and the contamination is significantly reduced when the Thermal Electric Cooler (TEC) hot-junction temperature is below minus 40 degrees to minus 50 degrees C. The utility of contamination sensors located behind instruments during system tests was demonstrated.

Mechanical and Microstructure Study of Nickel-Based ODS Alloys Processed by Mechano-Chemical Bonding and Ball Milling

NASA Astrophysics Data System (ADS)

Amare, Belachew N.

Due to the need to increase the efficiency of modern power plants, land-based gas turbines are designed to operate at high temperature creating harsh environments for structural materials. The elevated turbine inlet temperature directly affects the materials at the hottest sections, which includes combustion chamber, blades, and vanes. Therefore, the hottest sections should satisfy a number of material requirements such as high creep strength, ductility at low temperature, high temperature oxidation and corrosion resistance. Such requirements are nowadays satisfied by implementing superalloys coated by high temperature thermal barrier coating (TBC) systems to protect from high operating temperature required to obtain an increased efficiency. Oxide dispersive strengthened (ODS) alloys are being considered due to their high temperature creep strength, good oxidation and corrosion resistance for high temperature applications in advanced power plants. These alloys operating at high temperature are subjected to different loading systems such as thermal, mechanical, and thermo-mechanical combined loads at operation. Thus, it is critical to study the high temperature mechanical and microstructure properties of such alloys for their structural integrity. The primary objective of this research work is to investigate the mechanical and microstructure properties of nickel-based ODS alloys produced by combined mechano-chemical bonding (MCB) and ball milling subjected to high temperature oxidation, which are expected to be applied for high temperature turbine coating with micro-channel cooling system. Stiffness response and microstructure evaluation of such alloy systems was studied along with their oxidation mechanism and structural integrity through thermal cyclic exposure. Another objective is to analyze the heat transfer of ODS alloy coatings with micro-channel cooling system using finite element analysis (FEA) to determine their feasibility as a stand-alone structural coating. During this project it was found that stiffness response to increase and remain stable to a certain level and reduce at latter stages of thermal cyclic exposure. The predominant growth and adherent Ni-rich outer oxide scale was found on top of the alumina scale throughout the oxidation cycles. The FEA analysis revealed that ODS alloys could be potential high temperature turbine coating materials if micro-channel cooling system is implemented.

Plastic Deformation of Micromachined Silicon Diaphragms with a Sealed Cavity at High Temperatures

PubMed Central

Ren, Juan; Ward, Michael; Kinnell, Peter; Craddock, Russell; Wei, Xueyong

2016-01-01

Single crystal silicon (SCS) diaphragms are widely used as pressure sensitive elements in micromachined pressure sensors. However, for harsh environments applications, pure silicon diaphragms are hardly used because of the deterioration of SCS in both electrical and mechanical properties. To survive at the elevated temperature, the silicon structures must work in combination with other advanced materials, such as silicon carbide (SiC) or silicon on insulator (SOI), for improved performance and reduced cost. Hence, in order to extend the operating temperatures of existing SCS microstructures, this work investigates the mechanical behavior of pressurized SCS diaphragms at high temperatures. A model was developed to predict the plastic deformation of SCS diaphragms and was verified by the experiments. The evolution of the deformation was obtained by studying the surface profiles at different anneal stages. The slow continuous deformation was considered as creep for the diaphragms with a radius of 2.5 mm at 600 °C. The occurrence of plastic deformation was successfully predicted by the model and was observed at the operating temperature of 800 °C and 900 °C, respectively. PMID:26861332

Thermoelectric Exhaust Heat Recovery with Heat Pipe-Based Thermal Control

NASA Astrophysics Data System (ADS)

Brito, F. P.; Martins, Jorge; Hançer, Esra; Antunes, Nuno; Gonçalves, L. M.

2015-06-01

Heat pipe (HP)-based heat exchangers can be used for very low resistance heat transfer between a hot and a cold source. Their operating temperature depends solely on the boiling point of their working fluid, so it is possible to control the heat transfer temperature if the pressure of the HP can be adjusted. This is the case of the variable conductance HPs (VCHP). This solution makes VCHPs ideal for the passive control of thermoelectric generator (TEG) temperature levels. The present work assesses, both theoretically and experimentally, the merit of the aforementioned approach. A thermal and electrical model of a TEG with VCHP assist is proposed. Experimental results obtained with a proof of concept prototype attached to a small single-cylinder engine are presented and used to validate the model. It was found that the HP heat exchanger indeed enables the TEG to operate at a constant, optimal temperature in a passive and safe way, and with a minimal overall thermal resistance, under part load, it effectively reduces the active module area without deprecating the temperature level of the active modules.

Characterization of a High Current, Long Life Hollow Cathode

NASA Technical Reports Server (NTRS)

VanNoord, Jonathan L.; Kamhawi, Hani; McEwen, Heather K.

2006-01-01

The advent of higher power spacecraft makes it desirable to use higher power electric propulsion thrusters such as ion thrusters or Hall thrusters. Higher power thrusters require cathodes that are capable of producing higher currents. One application of these higher power spacecraft is deep-space missions that require tens of thousands of hours of operation. This paper presents the approach used to design a high current, long life hollow cathode assembly for that application, along with test results from the corresponding hollow cathode. The design approach used for the candidate hollow cathode was to reduce the temperature gradient in the insert, yielding a lower peak temperature and allowing current to be produced more uniformly along the insert. The lower temperatures result in a hollow cathode with increased life. The hollow cathode designed was successfully operated at currents from 10 to 60 A with flow rates of 5 to 19 sccm with a maximum orifice temperature measured of 1100 C. Data including discharge voltage, keeper voltage, discharge current, flow rates, and orifice plate temperatures are presented.

Contrasting suspended covers reveal the impact of an artificial monolayer on heat transfer processes at the interfacial boundary layer.

PubMed

Pittaway, P; Martínez-Alvarez, V; Hancock, N

2015-01-01

The highly variable performance of artificial monolayers in reducing evaporation from water storages has been attributed to wind speed and wave turbulence. Other factors operating at the interfacial boundary layer have seldom been considered. In this paper, two physical shade covers differing in porosity and reflectivity were suspended over 10 m diameter water tanks to attenuate wind and wave turbulence. The monolayer octadecanol was applied to one of the covered tanks, and micrometeorological conditions above and below the covers were monitored to characterise diurnal variation in the energy balance. A high downward (air-to-water) convective heat flux developed under the black cover during the day, whereas diurnal variation in the heat flux under the more reflective, wind-permeable white cover was much less. Hourly air and water temperature profiles under the covers over 3 days when forced convection was minimal (low wind speed) were selected for analysis. Monolayer application reduced temperature gain in surface water under a downward convective heat flux, and conversely reduced temperature loss under an upward convective heat flux. This 'dual property' may explain why repeat application of an artificial monolayer to retard evaporative loss (reducing latent heat loss) does not inevitably increase water temperature.

High-Temperature Superconductors as Electromagnetic Deployment and Support Structures in Spacecraft. [NASA NIAC Phase I

NASA Technical Reports Server (NTRS)

Getliffe, Gwendolyn V.; Inamdar, Niraj K.; Masterson, Rebecca; Miller, David W.

2012-01-01

This report, concluding a one-year NIAC Phase I study, describes a new structural and mechanical technique aimed at reducing the mass and increasing the deployed-to-stowed length and volume ratios of spacecraft systems. This technique uses the magnetic fields generated by electrical current passing through coils of high-temperature superconductors (HTSs) to support spacecraft structures and deploy them to operational configurations from their stowed positions inside a launch vehicle fairing.

Multi-Megawatt Power System Trade Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longhurst, Glen Reed; Schnitzler, Bruce Gordon; Parks, Benjamin Travis

2001-11-01

As part of a larger task, the Idaho National Engineering and Environmental Laboratory (INEEL) was tasked to perform a trade study comparing liquid-metal cooled reactors having Rankine power conversion systems with gas-cooled reactors having Brayton power conversion systems. This report summarizes the approach, the methodology, and the results of that trade study. Findings suggest that either approach has the possibility to approach the target specific mass of 3-5 kg/kWe for the power system, though it appears either will require improvements to achieve that. Higher reactor temperatures have the most potential for reducing the specific mass of gas-cooled reactors but domore » not necessarily have a similar effect for liquid-cooled Rankine systems. Fuels development will be the key to higher reactor operating temperatures. Higher temperature turbines will be important for Brayton systems. Both replacing lithium coolant in the primary circuit with gallium and replacing potassium with sodium in the power loop for liquid systems increase system specific mass. Changing the feed pump turbine to an electric motor in Rankine systems has little effect. Key technologies in reducing specific mass are high reactor and radiator operating temperatures, low radiator areal density, and low turbine/generator system masses. Turbine/generator mass tends to dominate overall power system mass for Rankine systems. Radiator mass was dominant for Brayton systems.« less

Proton radiation damage experiment on P-Channel CCD for an X-ray CCD camera onboard the ASTRO-H satellite

NASA Astrophysics Data System (ADS)

Mori, Koji; Nishioka, Yusuke; Ohura, Satoshi; Koura, Yoshiaki; Yamauchi, Makoto; Nakajima, Hiroshi; Ueda, Shutaro; Kan, Hiroaki; Anabuki, Naohisa; Nagino, Ryo; Hayashida, Kiyoshi; Tsunemi, Hiroshi; Kohmura, Takayoshi; Ikeda, Shoma; Murakami, Hiroshi; Ozaki, Masanobu; Dotani, Tadayasu; Maeda, Yukie; Sagara, Kenshi

2013-12-01

We report on a proton radiation damage experiment on P-channel CCD newly developed for an X-ray CCD camera onboard the ASTRO-H satellite. The device was exposed up to 109 protons cm-2 at 6.7 MeV. The charge transfer inefficiency (CTI) was measured as a function of radiation dose. In comparison with the CTI currently measured in the CCD camera onboard the Suzaku satellite for 6 years, we confirmed that the new type of P-channel CCD is radiation tolerant enough for space use. We also confirmed that a charge-injection technique and lowering the operating temperature efficiently work to reduce the CTI for our device. A comparison with other P-channel CCD experiments is also discussed. We performed a proton radiation damage experiment on a new P-channel CCD. The device was exposed up to 109 protons cm-2 at 6.7 MeV. We confirmed that it is radiation tolerant enough for space use. We confirmed that a charge-injection technique reduces the CTI. We confirmed that lowering the operating temperature also reduces the CTI.

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1992-01-01

Thin film ferroelectric capacitors comprising a ferroelectric film sandwiched between electrodes for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode. The anneal is done so as to form the interface between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550 to 600 C for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the nonswitching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the nonswitching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Enhanced fatigue and retention in ferroelectric thin film memory capacitors by post-top electrode anneal treatment

NASA Technical Reports Server (NTRS)

Thakoor, Sarita (Inventor)

1994-01-01

Thin film ferroelectric capacitors (10) comprising a ferroelectric film (18) sandwiched between electrodes (16 and 20) for nonvolatile memory operations are rendered more stable by subjecting the capacitors to an anneal following deposition of the top electrode (20). The anneal is done so as to form the interface (22) between the ferroelectric film and the top electrode. Heating in an air oven, laser annealing, or electron bombardment may be used to form the interface. Heating in an air oven is done at a temperature at least equal to the crystallization temperature of the ferroelectric film. Where the ferroelectric film comprises lead zirconate titanate, annealing is done at about 550.degree. to 600.degree. C. for about 10 to 15 minutes. The formation treatment reduces the magnitude of charge associated with the non-switching pulse in the thin film ferroelectric capacitors. Reduction of this charge leads to significantly more stable nonvolatile memory operations in both digital and analog memory devices. The formation treatment also reduces the ratio of change of the charge associated with the non-switching pulse as a function of retention time. These improved memory devices exhibit greater performance in retention and reduced fatigue in memory arrays.

Synthesis, Characterization, and Optimization of Novel Solid Oxide Fuel Cell Anodes

NASA Astrophysics Data System (ADS)

Miller, Elizabeth C.

This dissertation presents research on the development of novel materials and fabrication procedures for solid oxide fuel cell (SOFC) anodes. The work discussed here is divided into three main categories: all-oxide anodes, catalyst exsolution oxide anodes, and Ni-infiltrated anodes. The all-oxide and catalyst exsolution anodes presented here are further classi?ed as Ni-free anodes operating at the standard 700-800°C SOFC temperature while the Ni-infiltrated anodes operate at intermediate temperatures (≤650°C). Compared with the current state-of-the-art Ni-based cermets, all-oxide, Ni-free SOFC anodes offer fewer coking issues in carbon-containing fuels, reduced degradation due to fuel contaminants, and improved stability during redox cycling. However, electrochemical performance has proven inferior to Ni-based anodes. The perovskite oxide Fe-substituted strontium titanate (STF) has shown potential as an anode material both as a single phase electrode and when combined with Gd-doped ceria (GDC) in a composite electrode. In this work, STF is synthesized using a modified Pechini processes with the aim of reducing STF particle size and increasing the electrochemically active area in the anode. The Pechini method produced particles ? 750 nm in diameter, which is signi°Cantly smaller than the typically micron-sized solid state reaction powder. In the first iteration of anode fabrication with the Pechini powder, issues with over-sintering of the small STF particles limited gas di?usion in the anode. However, after modifying the anode firing temperature, the Pechini cells produced power density comparable to solid state reaction based cells from previous work by Cho et al. Catalyst exsolution anodes, in which metal cations exsolve out of the lattice under reducing conditions and form nanoparticles on the oxide surface, are another Ni-free option for standard operating temperature SOFCs. Little information is known about the onset of nanoparticle formation, which presents opportunities for the new kinds of ex situ and in situ experiments performed in this thesis. Ex situ experiments involved reducing powder samples at SOFC operating temperatures under hydrogen gas and characterizing them via electron microscopy and X-ray diffraction (XRD). For the in situ experiments, powders were heated, then reduced at temperature, and catalyst exsolution was observed in real-time. Pechini-synthesized cerium oxide substituted with 2-5 mol% Pd was studied using in situ X-ray heating experiments at Argonne National Laboratory's Advanced Photon Source. In these experiments, the powder was subjected to several cycles of reduction and oxidation at 800°C, and Pd metal formation was confirmed through the appearance of Pd peaks in the X-ray spectra. Next, Fe- and Ru-substituted lanthanum strontium chromite (LSCrFeRu14) synthesized by solid state reaction was characterized with ex situ and in situ microscopy. Transmission electron microscopy (TEM) in situ heating experiments were conducted to observe Ru nanoparticle evolution under the reducing conditions of the TEM vacuum chamber. LSCrFeRu14 was heated to 750°C and observed over ˜ 90 min at temperature during which time nanoparticle formation, coarsening, and di?usion were observed. Experiments on both materials sought to understand the conditions and timing of nanoparticle formation in the anode, which is not necessarily apparent from electrochemical data. Reducing the operating temperature of SOFCs from the current state-of-the-art range of 700-800°C to ≤ 650°C has many advantages, among them increased long-term stability, reduced balance of plant costs, fewer interconnect/seal material issues, and decreased start-up times. In order to maintain good performance at reduced temperature, these intermediate temperature SOFCs require new materials including highly active alternatives to micron-scale Ni-YSZ composite anodes. The present work focuses on the development of IT-SOFCs with Sr0.8La 0.2TiO3 (SLT) anode supports, thin La1--xSr x Ga0.8Mg0.2O3 (x = 0.1, 0.2) dense electrolytes, and porous LSGM anode functional layers. The SLT support and the LSGM functional layer are infiltrated with nanoscale Ni, creating extensive electrochemically active triple phase boundary area. The scope of the work presented here encompasses every step of cell development including powder synthesis, optimization of firing conditions, and long-term stability testing. Using an optimized fabrication process, cells with power density > 1.2 W cm-2 were fabricated. Dry pressing and colloidal de-position were used to make the first generation of these cells, and once suitable times and temperatures were determined, the process was shifted to tape casting to make larger batches of uniform cells. After obtaining initial results of low anode polarization resistance and high power density, the long-term stability of the Ni-infiltrated anodes was examined. A coarsening model was developed using the data from accelerated degradation tests to predict cell performance over a typical device lifetime. This thesis encompasses a broad range of novel SOFC anode materials, each of which has its own strengths and weaknesses. Presenting several possible avenues for SOFC development provides a complete picture of the ?eld and its current focuses. The wide scope of this work offers multiple solutions for the SOFC community and demonstrates that SOFCs are a strong candidate for meeting the United States' need for energy conversion and storage.

A fiber optic temperature sensor based on multi-core microstructured fiber with coupled cores for a high temperature environment

NASA Astrophysics Data System (ADS)

Makowska, A.; Markiewicz, K.; Szostkiewicz, L.; Kolakowska, A.; Fidelus, J.; Stanczyk, T.; Wysokinski, K.; Budnicki, D.; Ostrowski, L.; Szymanski, M.; Makara, M.; Poturaj, K.; Tenderenda, T.; Mergo, P.; Nasilowski, T.

2018-02-01

Sensors based on fiber optics are irreplaceable wherever immunity to strong electro-magnetic fields or safe operation in explosive atmospheres is needed. Furthermore, it is often essential to be able to monitor high temperatures of over 500°C in such environments (e.g. in cooling systems or equipment monitoring in power plants). In order to meet this demand, we have designed and manufactured a fiber optic sensor with which temperatures up to 900°C can be measured. The sensor utilizes multi-core fibers which are recognized as the dedicated medium for telecommunication or shape sensing, but as we show may be also deployed advantageously in new types of fiber optic temperature sensors. The sensor presented in this paper is based on a dual-core microstructured fiber Michelson interferometer. The fiber is characterized by strongly coupled cores, hence it acts as an all-fiber coupler, but with an outer diameter significantly wider than a standard fused biconical taper coupler, which significantly increases the coupling region's mechanical reliability. Owing to the proposed interferometer imbalance, effective operation and high-sensitivity can be achieved. The presented sensor is designed to be used at high temperatures as a result of the developed low temperature chemical process of metal (copper or gold) coating. The hermetic metal coating can be applied directly to the silica cladding of the fiber or the fiber component. This operation significantly reduces the degradation of sensors due to hydrolysis in uncontrolled atmospheres and high temperatures.

Hypothyroidism leads to increased dopamine receptor sensitivity and concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crocker, A.D.; Overstreet, D.H.; Crocker, J.M.

1986-06-01

Rats treated with iodine-131 were confirmed to be hypothyroid by their reduced baseline core body temperatures, reduced serum thyroxine concentrations and elevated serum thyroid stimulating hormone concentrations. When hypothyroid rats were compared to euthyroid controls they were more sensitive to the effects of apomorphine (1.0 mumol/kg) on stereotypy, operant responding and body temperature and showed a smaller reduction in locomotor activity after injection of haloperidol (0.25 mumol/kg). Receptor binding studies on striatal homogenates indicated that hypothyroid rats had increased concentrations of D2 dopamine receptors but there was no change in the affinity. It is concluded that hypothyroidism increases dopamine receptormore » sensitivity by increasing receptor concentration.« less

Microcombustor

DOEpatents

Gardner, Timothy J.; Manginelli, Ronald P.; Lewis, Patrick R.; Frye-Mason, Gregory C.; Colburn, Chris

2004-09-07

A microcombustor comprises a microhotplate and a catalyst for sustained combustion on the microscale. The microhotplate has very low heat capacity and thermal conductivity that mitigate large heat losses arising from large surface-to-volume ratios typical of the microdomain. The heated catalyst enables flame ignition and stabilization, permits combustion with lean fuel/air mixtures, extends a hydrocarbon's limits of flammability, and lowers the combustion temperature. The reduced operating temperatures enable a longer microcombustor lifetime and the reduced fuel consumption enables smaller fuel supplies, both of which are especially important for portable microsystems applications. The microcombustor can be used for on-chip thermal management and for sensor applications, such as heating of a micro gas chromatography column and for use as a micro flame ionization detector.

Low emissivity high-temperature tantalum thin film coatings for silicon devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rinnerbauer, Veronika; Senkevich, Jay J.; Joannopoulos, John D.

The authors study the use of thin ( ~230 nm ) tantalum (Ta) layers on silicon (Si) as a low emissivity (high reflectivity) coating for high-temperature Si devices. Such coatings are critical to reduce parasitic radiation loss, which is one of the dominant loss mechanisms at high temperatures (above 700 °C ). The key factors to achieve such a coating are low emissivity in the near infrared and superior thermal stability at high operating temperatures. The authors investigated the emissivity of Ta coatings deposited on Si with respect to deposition parameters, and annealing conditions, and temperature. The authors found thatmore » after annealing at temperatures ≥900 °C the emissivity in the near infrared ( 1–3 μm ) was reduced by a factor of 2 as compared to bare Si. In addition, the authors measured thermal emission at temperatures from 700 to 1000 °C , which is stable up to a heater temperature equal to the annealing temperature. Furthermore, Auger electron spectroscopy profiles of the coatings before and after annealing were taken to evaluate thermal stability. A thin (about 70 nm) Ta₂O₅ layer was found to act as an efficient diffusion barrier between the Si substrate and the Ta layer to prevent Si diffusion.« less

Air-atomizing splash-cone fuel nozzle reduces pollutant emissions from turbojet engines

NASA Technical Reports Server (NTRS)

Ingebo, R. D.; Norgren, C. T.

1973-01-01

Advantages of fuel nozzle over conventional pressure-atomizing fuel nozzles: simplicity of construction, ability to distribute fuel-air mixture uniformly across full height of combustor without using auxiliary air supply, reliability when using contaminated fuels, and durability of nozzle at high operating temperatures.

Temperature insensitive and ultra wideband silica-based dual polarization optical hybrid for coherent receiver with highly symmetrical interferometer design.

PubMed

Nasu, Yusuke; Mizuno, Takayuki; Kasahara, Ryoichi; Saida, Takashi

2011-12-12

To extend the operation wavelength range of dual-polarization optical hybrids (DPOH), we propose a highly symmetrical interferometer design for a polarization beam splitter and an optical hybrid to reduce temperature and wavelength dependence. The design successfully decreases this dependence, and a fabricated DPOH with silica-based planar lightwave circuits provides temperature-insensitive performance with a polarization extinction ratio of over 25 dB and phase errors of less than 3 degrees over the entire C- and L-bands. © 2011 Optical Society of America

Steady State Thermal Analyses of SCEPTOR X-57 Wingtip Propulsion

NASA Technical Reports Server (NTRS)

Schnulo, Sydney L.; Chin, Jeffrey C.; Smith, Andrew D.; Dubois, Arthur

2017-01-01

Electric aircraft concepts enable advanced propulsion airframe integration approaches that promise increased efficiency as well as reduced emissions and noise. NASA's fully electric Maxwell X-57, developed under the SCEPTOR program, features distributed propulsion across a high aspect ratio wing. There are 14 propulsors in all: 12 high lift motor that are only active during take off and climb, and 2 larger motors positioned on the wingtips that operate over the entire mission. The power electronics involved in the wingtip propulsion are temperature sensitive and therefore require thermal management. This work focuses on the high and low fidelity heat transfer analysis methods performed to ensure that the wingtip motor inverters do not reach their temperature limits. It also explores different geometry configurations involved in the X-57 development and any thermal concerns. All analyses presented are performed at steady state under stressful operating conditions, therefore predicting temperatures which are considered the worst-case scenario to remain conservative.

Li + -Desolvation Dictating Lithium-Ion Battery’s Low-Temperature Performances

DOE PAGES

Li, Qiuyan; Lu, Dongping; Zheng, Jianming; ...

2017-11-17

Lithium (Li) ion battery (LIB) has penetrated almost every aspects of human life, from portable electronics, vehicles to grids, and its operation stability in extreme environments becomes increasingly important. Among these, sub-zero temperature presents a kinetic challenge to the electrochemical reactions required to deliver the stored energy. Here, in this work, we attempted to identify the rate-determining process for Li + migration under such low temperatures, so that an optimum electrolyte formulation could be designed to maximize the energy output. Substantial increase in available capacities from graphite||LiNi 0.80Co 0.15Al 0.05O 2 chemistry down to -40°C is achieved by reducing themore » solvent molecule that more tightly binds to Li + and thus constitutes high desolvation energy barrier. Lastly, the fundamental understanding is applicable universally to a wide spectrum of electrochemical devices that have to operate in similar environments.« less

Contractor cuts solar gain with custom window curtain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ingraham, R.

1985-04-22

A local energy services contractor, using a 210-foot motorized thermal curtain to deflect sunlight entering the windows, has reduced excessive heat gain at a racetrack clubhouse here, cutting air conditioning run-time by about 75%. Because Mobile Greyhound Park's clubhouse faces east, direct exposure to sunlight from dawn to afternoon race time, about 1 p.m., was bringing the indoor temperature to almost 100/sup 0/, according to Stan Norris, operations management for the contracting firm, Technical Energy Controls, Inc. Lowering the temperature to a comfortable level required running four Carrier Corporation air handling units, rated at a total of more than 170more » tons, for about eight hours, and annual energy bills were running at about $240,000, Norris said. With the aluminum foil-backed vinyl curtain, the air handling units need only operate two hours to bring temperatures to comfort levels.« less

High temperature superconductors for magnetic suspension applications

NASA Technical Reports Server (NTRS)

Mcmichael, C. K.; Cooley, R. S.; Chen, Q. Y.; Ma, K. B.; Lamb, M. A.; Meng, R. L.; Chu, C. W.; Chu, W. K.

1994-01-01

High temperature superconductors (HTS) hold the promise for applications in magnetic levitation bearings, vibration damping, and torque coupling. Traditional magnetic suspension systems require active feedback and vibration controls in which power consumption and low frequency vibration are among the major engineering concerns. HTS materials have been demonstrated to be an enabling approach towards such problems due to their flux trapping properties. In our laboratory at TCSUH, we have been conducting a series of experiments to explore various mechanical applications using HTS. We have constructed a 30 lb. model flywheel levitated by a hybrid superconducting magnetic bearing (HSMB). We are also developing a levitated and vibration-dampled platform for high precision instrumentation. These applications would be ideal for space usages where ambient temperature is adequate for HTS to operate properly under greatly reduced cryogenic requirements. We will give a general overview of these potential applications and discuss the operating principles of the HTS devices we have developed.

Li+-Desolvation Dictating Lithium-Ion Battery's Low-Temperature Performances.

PubMed

Li, Qiuyan; Lu, Dongping; Zheng, Jianming; Jiao, Shuhong; Luo, Langli; Wang, Chong-Min; Xu, Kang; Zhang, Ji-Guang; Xu, Wu

2017-12-13

Lithium (Li) ion battery has penetrated almost every aspect of human life, from portable electronics, vehicles, to grids, and its operation stability in extreme environments is becoming increasingly important. Among these, subzero temperature presents a kinetic challenge to the electrochemical reactions required to deliver the stored energy. In this work, we attempted to identify the rate-determining process for Li + migration under such low temperatures, so that an optimum electrolyte formulation could be designed to maximize the energy output. Substantial increase in the available capacities from graphite∥LiNi 0.80 Co 0.15 Al 0.05 O 2 chemistry down to -40 °C is achieved by reducing the solvent molecule that more tightly binds to Li + and thus constitutes a high desolvation energy barrier. The fundamental understanding is applicable universally to a wide spectrum of electrochemical devices that have to operate in similar environments.

Li + -Desolvation Dictating Lithium-Ion Battery’s Low-Temperature Performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Qiuyan; Lu, Dongping; Zheng, Jianming

Lithium (Li) ion battery (LIB) has penetrated almost every aspects of human life, from portable electronics, vehicles to grids, and its operation stability in extreme environments becomes increasingly important. Among these, sub-zero temperature presents a kinetic challenge to the electrochemical reactions required to deliver the stored energy. In this work, we attempted to identify the rate-determining process for Li+ migration under such low temperatures, so that an optimum electrolyte formulation could be designed to maximize the energy output. Substantial increase in available capacities from graphite||LiNi0.80Co0.15Al0.05O2 chemistry down to -40°C is achieved by reducing the solvent molecule that more tightly bindsmore » to Li+ and thus constitutes high desolvation energy barrier. The fundamental understanding is applicable universally to all electrochemical devices that have to operate in similar environments.« less

Li + -Desolvation Dictating Lithium-Ion Battery’s Low-Temperature Performances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Qiuyan; Lu, Dongping; Zheng, Jianming

Lithium (Li) ion battery (LIB) has penetrated almost every aspects of human life, from portable electronics, vehicles to grids, and its operation stability in extreme environments becomes increasingly important. Among these, sub-zero temperature presents a kinetic challenge to the electrochemical reactions required to deliver the stored energy. Here, in this work, we attempted to identify the rate-determining process for Li + migration under such low temperatures, so that an optimum electrolyte formulation could be designed to maximize the energy output. Substantial increase in available capacities from graphite||LiNi 0.80Co 0.15Al 0.05O 2 chemistry down to -40°C is achieved by reducing themore » solvent molecule that more tightly binds to Li + and thus constitutes high desolvation energy barrier. Lastly, the fundamental understanding is applicable universally to a wide spectrum of electrochemical devices that have to operate in similar environments.« less

Acetone Sensing Properties of a Gas Sensor Composed of Carbon Nanotubes Doped With Iron Oxide Nanopowder

PubMed Central

Tan, Qiulin; Fang, Jiahua; Liu, Wenyi; Xiong, Jijun; Zhang, Wendong

2015-01-01

Iron oxide (Fe2O3) nanopowder was prepared by a precipitation method and then mixed with different proportions of carbon nanotubes. The composite materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. A fabricated heater-type gas sensor was compared with a pure Fe2O3 gas sensor under the influence of acetone. The effects of the amount of doping, the sintering temperature, and the operating temperature on the response of the sensor and the response recovery time were analyzed. Experiments show that doping of carbon nanotubes with iron oxide effectively improves the response of the resulting gas sensors to acetone gas. It also reduces the operating temperature and shortens the response recovery time of the sensor. The response of the sensor in an acetone gas concentration of 80 ppm was enhanced, with good repeatability. PMID:26569253

Acetone Sensing Properties of a Gas Sensor Composed of Carbon Nanotubes Doped With Iron Oxide Nanopowder.

PubMed

Tan, Qiulin; Fang, Jiahua; Liu, Wenyi; Xiong, Jijun; Zhang, Wendong

2015-11-11

Iron oxide (Fe₂O₃) nanopowder was prepared by a precipitation method and then mixed with different proportions of carbon nanotubes. The composite materials were characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. A fabricated heater-type gas sensor was compared with a pure Fe₂O₃ gas sensor under the influence of acetone. The effects of the amount of doping, the sintering temperature, and the operating temperature on the response of the sensor and the response recovery time were analyzed. Experiments show that doping of carbon nanotubes with iron oxide effectively improves the response of the resulting gas sensors to acetone gas. It also reduces the operating temperature and shortens the response recovery time of the sensor. The response of the sensor in an acetone gas concentration of 80 ppm was enhanced, with good repeatability.

Modeling and Simulation of a Nuclear Fuel Element Test Section

NASA Technical Reports Server (NTRS)

Moran, Robert P.; Emrich, William

2011-01-01

"The Nuclear Thermal Rocket Element Environmental Simulator" test section closely simulates the internal operating conditions of a thermal nuclear rocket. The purpose of testing is to determine the ideal fuel rod characteristics for optimum thermal heat transfer to their hydrogen cooling/working fluid while still maintaining fuel rod structural integrity. Working fluid exhaust temperatures of up to 5,000 degrees Fahrenheit can be encountered. The exhaust gas is rendered inert and massively reduced in temperature for analysis using a combination of water cooling channels and cool N2 gas injectors in the H2-N2 mixer portion of the test section. An extensive thermal fluid analysis was performed in support of the engineering design of the H2-N2 mixer in order to determine the maximum "mass flow rate"-"operating temperature" curve of the fuel elements hydrogen exhaust gas based on the test facilities available cooling N2 mass flow rate as the limiting factor.

High-temperature superconducting undulator magnets

DOE PAGES

Kesgin, Ibrahim; Kasa, Matthew; Ivanyushenkov, Yury; ...

2017-02-13

Here, this paper presents test results on a prototype superconducting undulator magnet fabricated using 15% Zr-doped rare-earth barium copper oxide high temperature superconducting (HTS) tapes. On an 11-pole magnet we demonstrate an engineering current density, J e, of more than 2.1 kA mm -2 at 4.2 K, a value that is 40% higher than reached in comparable devices wound with NbTi-wire, which is used in all currently operating superconducting undulators. A novel winding scheme enabling the continuous winding of tape-shaped conductors into the intricate undulator magnets as well as a partial interlayer insulation procedure were essential in reaching this advancemore » in performance. Currently, there are rapid advances in the performance of HTS; therefore, achieving even higher current densities in an undulator structure or/and operating it at temperatures higher than 4.2 K will be possible, which would substantially simplify the cryogenic design and reduce overall costs.« less

Measurement approach and design of the CubeSat Infrared Atmospheric Sounder (CIRAS)

NASA Astrophysics Data System (ADS)

Pagano, Thomas S.; Rider, David; Rud, Mayer; Ting, David; Yee, Karl

2016-09-01

The CubeSat Infrared Atmospheric Sounder (CIRAS) will measure upwelling infrared radiation of the Earth in the MWIR region of the spectrum from space on a CubeSat. The observed radiances have information of potential value to weather forecasting agencies and can be used to retrieve lower tropospheric temperature and water vapor globally for weather and climate science investigations. Multiple units can be flown to improve temporal coverage or in formation to provide new data products including 3D atmospheric motion vector winds. CIRAS incorporates key new instrument technologies including a 2D array of High Operating Temperature Barrier Infrared Detector (HOT-BIRD) material, selected for its high uniformity, low cost, low noise and higher operating temperatures than traditional materials. The detectors are hybridized to a commercial ROIC and commercial camera electronics. The second key technology is an MWIR Grating Spectrometer (MGS) designed to provide imaging spectroscopy for atmospheric sounding in a CubeSat volume. The MGS has no moving parts and includes an immersion grating to reduce the volume and reduce distortion. The third key technology is an infrared blackbody fabricated with black silicon to have very high emissivity in a flat plate construction. JPL will also develop the mechanical, electronic and thermal subsystems for CIRAS, while the spacecraft will be a commercially available CubeSat. The integrated system will be a complete 6U CubeSat capable of measuring temperature and water vapor profiles with good lower tropospheric sensitivity. The CIRAS is the first step towards the development of an Earth Observation Nanosatellite Infrared (EON-IR) capable of operational readiness to mitigate a potential loss of CrIS on JPSS or complement the current observing system with different orbit crossing times.

Design and development of SiGe based near-infrared photodetectors

NASA Astrophysics Data System (ADS)

Zeller, John W.; Puri, Yash R.; Sood, Ashok K.; McMahon, Shane; Efsthadiatis, Harry; Haldar, Pradeep; Dhar, Nibir K.

2014-10-01

Near-infrared (NIR) sensors operating at room temperatures are critical for a variety of commercial and military applications including detecting mortar fire and muzzle flashes. SiGe technology offers a low-cost alternative to conventional IR sensor technologies such as InGaAs, InSb, and HgCdTe for developing NIR micro-sensors that will not require any cooling and can operate with high bandwidths and comparatively low dark currents. Since Ge has a larger thermal expansion coefficient than Si, tensile strain may be incorporated into detector devices during the growth process, enabling an extended operating wavelength range above 1600 nm. SiGe based pin photodetectors have advantages of high stability, low noise, and high responsivity compared to metal-semiconductor-metal (MSM) devices. We have developed a process flow and are fabricating SiGe detector devices on 12" (300 mm) silicon wafers in order to take advantage of high throughput, large-area leading-edge silicon based CMOS technology that provides small feature sizes with associated device cost/density scaling advantages. The fabrication of the detector devices is facilitated by a two-step growth process incorporating initial low temperature growth of Ge/SiGe to form a thin strain-relaxed layer, followed by high temperature growth to deposit a thicker absorbing film, and subsequent high temperature anneal. This growth process is designed to effectively reduce dark current and enhance detector performance by reducing the number of defects and threading dislocations which form recombination centers during the growth process. Various characterization techniques have been employed to determine the properties of the epitaxially deposited Ge/SiGe layers, and the corresponding results are discussed.

Cause and cure for high volatile coal and corrosive gases at TXI, Midlothian Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahid, A.; Bottelberghe, B.; Crowther, J.

2007-07-01

The plant has raw materials which are high in pyritic sulfur. The coal mill uses the preheater exhaust gases, which have elevated amounts of SO{sub 2}. The coal being used is highly volatile. Therefore the coal mill bag filter had few occurrences of smoldered bags causing potentially unsafe conditions. This problem was solved by implementing some operational changes like reducing the mill exit temperature based on dewatering curve of coal and making the system more inert. To achieve this water had to be added into the system. When the mill exit temperature was reduced, the operating temperatures were below themore » sulfuric and hydrochloric acid dew points. Because of this corrosive acid stream in the gas flow, the bag filter started corroding. En route to solving these issues, the plant neutralized the acid by adding the raw meal dust and changing the bag filter into a stainless steel construction. Furthermore, the requirement to spray water in the system was removed by adding a heat exchanger to the coal mill inlet. Also, there were some design changes made to the coal mill bag filter, which helped in stable operation and extended bag life in the bag filter. This paper discusses these issues and how these problems were solved. This paper would be of beneficial use for other plants, which have to deal with high volatile coal and highly corrosive gases.« less

Design, fabrication and test of a liquid hydrogen titanium honeycomb cryogenic test tank for use as a reusable launch vehicle main propellant tank

NASA Astrophysics Data System (ADS)

Stickler, Patrick B.; Keller, Peter C.

1998-01-01

Reusable Launch Vehicles (RLV's) utilizing LOX\\LH2 as the propellant require lightweight durable structural systems to meet mass fraction goals and to reduce overall systems operating costs. Titanium honeycomb sandwich with flexible blanket TPS on the windward surface is potentially the lightest-weight and most operable option. Light weight is achieved in part because the honeycomb sandwich tank provides insulation to its liquid hydrogen contents, with no need for separate cryogenic insulation, and in part because the high use temperature of titanium honeycomb reduces the required surface area of re-entry thermal protection systems. System operability is increased because TPS needs to be applied only to surfaces where temperatures exceed approximately 650 K. In order to demonstrate the viability of a titanium sandwich constructed propellant tank, a technology demonstration program was conducted including the design, fabrication and testing of a propellant tank-TPS system. The tank was tested in controlled as well as ambient environments representing ground hold conditions for a RLV main propellant tank. Data collected during each test run was used to validate predictions for air liquefaction, outside wall temperature, boil-off rates, frost buildup and its insulation effects, and the effects of placing a thermal protection system blanket on the external surface. Test results indicated that titanium honeycomb, when used as a RLV propellant tank material, has great promise as a light-weight structural system.

Phenomenological studies on sodium for CSP applications: A safety review

NASA Astrophysics Data System (ADS)

Armijo, Kenneth M.; Andraka, Charles E.

2016-05-01

Sodium Heat transfer fluids (HTF) such as sodium, can achieve temperatures above 700°C to obtain power cycle performance improvements for reducing large infrastructure costs of high-temperature systems. Current concentrating solar power (CSP) sensible HTF's (e.g. air, salts) have poor thermal conductivity, and thus low heat transfer capabilities, requiring a large receiver. The high thermal conductivity of sodium has demonstrated high heat transfer rates on dish and towers systems, which allow a reduction in receiver area by a factor of two to four, reducing re-radiation and convection losses and cost by a similar factor. Sodium produces saturated vapor at pressures suitable for transport starting at 600°C and reaches one atmosphere at 870°C, providing a wide range of suitable operating conditions that match proposed high temperature, isothermal power cycles. This advantage could increase the efficiency while lowering the cost of CSP tower systems. Although there are a number of desirable thermal performance advantages associated with sensible sodium, its propensity to rapidly oxidize presents safety challenges. This investigation presents a literature review that captures historical operations/handling lessons for advanced sodium receiver designs, and the current state-of-knowledge related to sodium combustion behavior. Technical and operational solutions addressing sodium safety and applications in CSP will be discussed, including unique safety hazards and advantages using latent sodium. Lessons obtained from the nuclear industry with sensible and latent systems will also be discussed in the context of safety challenges and risk mitigation solutions.

Increasing the operation temperature of polymer electrolyte membranes for fuel cells: From nanocomposites to hybrids

NASA Astrophysics Data System (ADS)

Licoccia, Silvia; Traversa, Enrico

Among the possible systems investigated for energy production with low environmental impact, polymeric electrolyte membrane fuel cells (PEMFCs) are very promising as electrochemical power sources for application in portable technology and electric vehicles. For practical applications, operating FCs at temperatures above 100 °C is desired, both for hydrogen and methanol fuelled cells. When hydrogen is used as fuel, an increase of the cell temperature produces enhanced CO tolerance, faster reaction kinetics, easier water management and reduced heat exchanger requirement. The use of methanol instead of hydrogen as a fuel for vehicles has several practical benefits such as easy transport and storage, but the slow oxidation kinetics of methanol needs operating direct methanol fuel cells (DMFCs) at intermediate temperatures. For this reason, new membranes are required. Our strategy to achieve the goal of operating at temperatures above 120 °C is to develop organic/inorganic hybrid membranes. The first approach was the use of nanocomposite class I hybrids where nanocrystalline ceramic oxides were added to Nafion. Nanocomposite membranes showed enhanced characteristics, hence allowing their operation up to 130 °C when the cell was fuelled with hydrogen and up to 145 °C in DMFCs, reaching power densities of 350 mW cm -2. The second approach was to prepare Class II hybrids via the formation of covalent bonds between totally aromatic polymers and inorganic clusters. The properties of such covalent hybrids can be modulated by modifying the ratio between organic and inorganic groups and the nature of the chemical components allowing to reach high and stable conductivity values up to 6.4 × 10 -2 S cm -1 at 120 °C.

Electrically injected GaAsBi/GaAs single quantum well laser diodes

NASA Astrophysics Data System (ADS)

Liu, Juanjuan; Pan, Wenwu; Wu, Xiaoyan; Cao, Chunfang; Li, Yaoyao; Chen, Xiren; Zhang, Yanchao; Wang, Lijuan; Yan, Jinyi; Zhang, Dongliang; Song, Yuxin; Shao, Jun; Wang, Shumin

2017-11-01

We present electrically injected GaAs/GaAsBi single quantum well laser diodes (LDs) emitting at a record long wavelength of 1141 nm at room temperature grown by molecular beam epitaxy. The LDs have excellent device performances with internal quantum efficiency of 86%, internal loss of 10 cm-1 and transparency current density of 196 A/cm2. The LDs can operate under continuous-wave mode up to 273 K. The characteristic temperature are extracted to be 125 K in the temperature range of 77˜150 K, and reduced to 90 K in the range of 150˜273 K. The temperature coefficient of 0.3 nm/K is extracted in the temperature range of 77˜273 K.

Experimental results from a laboratory-scale molten salt thermocline storage

NASA Astrophysics Data System (ADS)

Seubert, Bernhard; Müller, Ralf; Willert, Daniel; Fluri, Thomas

2017-06-01

Single-tank storage presents a valid option for cost reduction in thermal energy storage systems. For low-temperature systems with water as storage medium this concept is widely implemented and tested. For high-temperature systems very limited experimental data are publicly available. To improve this situation a molten salt loop for experimental testing of a single-tank storage prototype was designed and built at Fraunhofer ISE. The storage tank has a volume of 0.4 m3 or a maximum capacity of 72 kWhth. The maximum charging and discharging power is 60 kW, however, a bypass flow control system enables to operate the system also at a very low power. The prototype was designed to withstand temperatures up to 550 °C. A cascaded insulation with embedded heating cables can be used to reduce the effect of heat loss on the storage which is susceptible to edge effects due to its small size. During the first tests the operating temperatures were adapted to the conditions in systems with thermal oil as heat transfer fluid and a smaller temperature difference. A good separation between cold and hot fluid was achieved with temperature gradients of 95 K within 16 cm.

Wide-Temperature-Range Integrated Operational Amplifier

NASA Technical Reports Server (NTRS)

Mojarradi, Mohammad; Levanas, Greg; Chen, Yuan; Kolawa, Elizabeth; Cozy, Raymond; Blalock, Benjamin; Greenwell, Robert; Terry, Stephen

2007-01-01

A document discusses a silicon-on-insulator (SOI) complementary metal oxide/semiconductor (CMOS) integrated- circuit operational amplifier to be replicated and incorporated into sensor and actuator systems of Mars-explorer robots. This amplifier is designed to function at a supply potential less than or equal to 5.5 V, at any temperature from -180 to +120 C. The design is implemented on a commercial radiation-hard SOI CMOS process rated for a supply potential of less than or equal to 3.6 V and temperatures from -55 to +110 C. The design incorporates several innovations to achieve this, the main ones being the following: NMOS transistor channel lengths below 1 m are generally not used because research showed that this change could reduce the adverse effect of hot carrier injection on the lifetimes of transistors at low temperatures. To enable the amplifier to withstand the 5.5-V supply potential, a circuit topology including cascade devices, clamping devices, and dynamic voltage biasing was adopted so that no individual transistor would be exposed to more than 3.6 V. To minimize undesired variations in performance over the temperature range, the transistors in the amplifier are biased by circuitry that maintains a constant inversion coefficient over the temperature range.

Numerical Analysis of the Temperature Impact on Performance of GaN-Based 460-nm Light-Emitting Diode.

PubMed

Tawfik, Wael Z; Lee, June Key

2018-03-01

The influence of temperature on the characteristics of a GaN-based 460-nm light-emitting diode (LED) prepared on sapphire substrate was simulated using the SiLENSe and SpeCLED software programs. High temperatures impose negative effects on the performance of GaN-based LEDs. As the temperature increases, electrons acquire higher thermal energies, and therefore LEDs may suffer more from high-current loss mechanisms, which in turn causes a reduction in the radiative recombination rate in the active region. The internal quantum efficiency was reduced by about 24% at a current density of 35 A/cm2, and the electroluminescence spectral peak wavelength was redshifted. The LED operated at 260 K and exhibited its highest light output power of ~317.5 mW at a maximum injection current of 350 mA, compared to 212.2 mW for an LED operated at 400 K. However, increasing temperature does not cause a droop in efficiency under high injection conditions. The peak efficiency at 1 mA of injection current decreases more rapidly by ~15% with increasing temperature from 260 to 400 K than the efficiency at high injection current of 350 mA by ~11%.

Comprehensive Evaluation of Power Supplies at Cryogenic Temperatures for Deep Space Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Gerber, Scott; Hammoud, Ahmad; Elbuluk, Malik E.; Lyons, Valerie (Technical Monitor)

2002-01-01

The operation of power electronic systems at cryogenic temperatures is anticipated in many future space missions such as planetary exploration and deep space probes. In addition to surviving the space hostile environments, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. DC/DC converters are widely used in space power systems in the areas of power management, conditioning, and control. As part of the on-going Low Temperature Electronics Program at NASA, several commercial-off-the-shelf (COTS) DC/DC converters, with specifications that might fit the requirements of specific future space missions have been selected for investigation at cryogenic temperatures. The converters have been characterized in terms of their performance as a function of temperature in the range of 20 C to - 180 C. These converters ranged in electrical power from 8 W to 13 W, input voltage from 9 V to 72 V and an output voltage of 3.3 V. The experimental set-up and procedures along with the results obtained on the converters' steady state and dynamic characteristics are presented and discussed.

Pumpless thermal management of water-cooled high-temperature proton exchange membrane fuel cells

NASA Astrophysics Data System (ADS)

Song, Tae-Won; Choi, Kyoung-Hwan; Kim, Ji-Rae; Yi, Jung S.

2011-05-01

Proton exchange membrane fuel cells (PEMFCs) have been considered for combined heat and power (CHP) applications, but cost reduction has remained an issue for commercialization. Among various types of PEMFC, the high-temperature (HT) PEMFC is gaining more attention due to the simplicity of the system, that will make the total system cost lower. A pumpless cooling concept is introduced to reduce the number of components of a HT PEMFC system even further and also decrease the parasitic power required for operating the system. In this concept, water is used as the coolant, and the buoyancy force caused by the density difference between vapour and liquid when operated above boiling temperate is utilized to circulate the coolant between the stack and the cooling device. In this study, the basic parameters required to design the cooling device are discussed, and the stable operation of the HT PEMFC stack in both the steady-state and during transient periods is demonstrated. It found that the pumpless cooling method provides more uniform temperature distribution within the stack, regardless of the direction of coolant flow.

Thermal performance of a multi-evaporator loop heat pipe with thermal masses and thermal electrical coolers

NASA Technical Reports Server (NTRS)

Ku, Jentung; Ottenstein, Laura; Birur, Gajanana

2004-01-01

This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermal electric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of condenser is fully utilized. Ammonia was used ad the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 1OW even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/-0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing the orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling the LHP operating temperature; and 5) Effectiveness of the flow regulator in preventing vapor from going back the evaporators.

Thermal Performance of a Multi-Evaporator Loop Heat Pipe with Thermal Masses and Thermoelectric Coolers

NASA Technical Reports Server (NTRS)

Ku, Jen-Tung; Ottenstein, Laura; Birur, Gajanana

2004-01-01

This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermoelectric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of the condensers is fully utilized. Ammonia was used as the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 10W even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/- 0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling the LHP operating temperature; and 5 ) Effectiveness of the flow regulator in preventing vapor from going back the evaporators.

Adiabatic demagnetization refrigerator for use in zero gravity

NASA Technical Reports Server (NTRS)

Dingus, Michael L.

1988-01-01

In this effort, a new design concept for an adiabatic demagnetization refrigerator (ADR) that is capable of operation in zero gravity has been developed. The design uses a vortex precooler to lower the initial temperature of magnetic salt from the initial space superfluid helium dewar of 1.8 K to 1.1 K. This reduces the required maximum magnetic field from 4 Tesla to 2 Tesla. The laboratory prototype vortex precooler reached a minimum temperature of 0.78 K, and had a cooling power of 1 mW at 1.1 K. A study was conducted to determine the dependence of vortex cooler performance on system element configuration. A superfluid filled capillary heat switch was used in the design. The laboratory prototype ADR reached a minimum temperature of 0.107 K, and maintained temperatures below 0.125 K for 90 minutes. Demagnetization was carried out from a maximum field of 2 T. A soft iron shield was developed that reduced the radial central field to 1 gauss at 0.25 meters.

Operation and design selection of high temperature superconducting magnetic bearings

NASA Astrophysics Data System (ADS)

Werfel, F. N.; Floegel-Delor, U.; Riedel, T.; Rothfeld, R.; Wippich, D.; Goebel, B.

2004-10-01

Axial and radial high temperature superconducting (HTS) magnetic bearings are evaluated by their parameters. Journal bearings possess advantages over thrust bearings. High magnetic gradients in a multi-pole permanent magnet (PM) configuration, the surrounding melt textured YBCO stator and adequate designs are the key features for increasing the overall bearing stiffness. The gap distance between rotor and stator determines the specific forces and has a strong impact on the PM rotor design. We report on the designing, building and measuring of a 200 mm prototype 100 kg HTS bearing with an encapsulated and thermally insulated melt textured YBCO ring stator. The encapsulation requires a magnetically large-gap (4-5 mm) operation but reduces the cryogenic effort substantially. The bearing requires 3 l of LN2 for cooling down, and about 0.2 l LN2 h-1 under operation. This is a dramatic improvement of the efficiency and in the practical usage of HTS magnetic bearings.

Portable gas chromatograph mass spectrometer for on-site chemical analyses

DOEpatents

Haas, Jeffrey S.; Bushman, John F.; Howard, Douglas E.; Wong, James L.; Eckels, Joel D.

2002-01-01

A portable, lightweight (approximately 25 kg) gas chromatograph mass spectrometer, including the entire vacuum system, can perform qualitative and quantitative analyses of all sample types in the field. The GC/MS has a conveniently configured layout of components for ease of serviceability and maintenance. The GC/MS system can be transported under operating or near-operating conditions (i.e., under vacuum and at elevated temperature) to reduce the downtime before samples can be analyzed on-site.

A 10 Kelvin 3 Tesla Magnet for Space Flight ADR Systems

NASA Technical Reports Server (NTRS)

Tuttle, Jim; Shirron, Peter; Canavan, Edgar; DiPirro, Michael; Riall, Sara; Pourrahimi, Shahin

2003-01-01

Many future space flight missions are expected to use adiabatic demagnetization refrigerators (ADRs) to reach detector operating temperatures well below one Kelvin. The goal is to operate each ADR with a mechanical cooler as its heat sink, thus avoiding the use of liquid cryogens. Although mechanical coolers are being developed to operate at temperatures of 6 Kelvin and below, there is a large efficiency cost associated with operating them at the bottom of their temperature range. For the multi-stage ADR system being developed at Goddard Space Flight Center, the goal is to operate with a 10 Kelvin mechanical cooler heat sink. With currently available paramagnetic materials, the highest temperature ADR stage in such a system will require a magnetic field of approximately three Tesla. Thus the goal is to develop a small, lightweight three Tesla superconducting magnet for operation at 10 Kelvin. It is important that this magnet have a low current/field ratio. Because traditional NbTi magnets do not operate safely above about six Kelvin, a magnet with a higher Tc is required. The primary focus has been on Nb3Sn magnets. Since standard Nb3Sn wire must be coated with thick insulation, wound on a magnet mandrel and then reacted, standard Nb,Sn magnets are quite heavy and require high currents Superconducting Systems developed a Nb3Sn wire which can be drawn down to small diameter, reacted, coated with thin insulation and then wound on a small diameter coil form. By using this smaller wire and operating closer to the wire s critical current, it should be possible to reduce the mass and operating current of 10 Kelvin magnets. Using this "react-then-wind" technology, Superconducting Systems has produced prototype 10 Kelvin magnets. This paper describes the development and testing of these magnets and discusses the outlook for including 10 Kelvin magnets on space-flight missions.

Influence of temperature gradients on charge transport in asymmetric nanochannels.

PubMed

Benneker, Anne M; Wendt, Hans David; Lammertink, Rob G H; Wood, Jeffery A

2017-10-25

Charge selective asymmetric nanochannels are used for a variety of applications, such as nanofluidic sensing devices and energy conversion applications. In this paper, we numerically investigate the influence of an applied temperature difference over tapered nanochannels on the resulting charge transport and flow behavior. Using a temperature-dependent formulation of the coupled Poisson-Nernst-Planck and Navier-Stokes equations, various nanochannel geometries are investigated. Temperature has a large influence on the total ion transport, as the diffusivity of ions and viscosity of the solution are strongly affected by temperature. We find that the selectivity of the nanochannels is enhanced with increasing asymmetry ratios, while the total current is reduced at higher asymmetry cases. Most interestingly, we find that applying a temperature gradient along the electric field and along the asymmetry direction of the nanochannel enhances the selectivity of the tapered channels even further, while a temperature gradient countering the electric field reduces the selectivity of the nanochannel. Current rectification is enhanced in asymmetric nanochannels if a temperature gradient is applied, independent of the direction of the temperature difference. However, the degree of rectification is dependent on the direction of the temperature gradient with respect to the channel geometry and the electric field direction. The enhanced selectivity of nanochannels due to applied temperature gradients could result in more efficient operation in energy harvesting or desalination applications, motivating experimental investigations.

Anomalous Transport in High Beta Poloidal DIII-D Discharges

NASA Astrophysics Data System (ADS)

Pankin, A.; Garofalo, A.; Kritz, A.; Rafiq, T.; Weiland, J.

2016-10-01

Dominant instabilities that drive anomalous transport in high beta poloidal DIII-D discharges are investigated using the MMM7.1, and TGLF models in the predictive integrated modeling TRANSP code. The ion thermal transport is found to be strongly reduced in these discharges, but turbulence driven by the ITG modes along with the neoclassical transport still play a role in determining the ion temperature profiles. The electron thermal transport driven by the ETG modes impact the electron temperature profiles. The E × B flow shear is found to have a small effect in reducing the electron thermal transport. The Shafranov shift is found to strongly reduce the anomalous transport in the high beta poloidal DIII-D discharges. The reduction of Shafranov shift can destroy the ion internal transport barrier and can result in significantly lower core temperatures. The MMM7.1 model predicts electron and ion temperature profiles reasonably well, but it fails to accurately predict the properties of electron internal transport barrier, which indicates that the ETG model in MMM7.1 needs to be improved in the high beta poloidal operational regime. Research supported by the Office of Science, US DOE.

Implementation of a multidisciplinary guideline improves preterm infant admission temperatures.

PubMed

Harer, M W; Vergales, B; Cady, T; Early, A; Chisholm, C; Swanson, J R

2017-11-01

Hypothermia is a common problem in preterm infants immediately following delivery.Local problem:The rate of admission hypothermia in our neonatal intensive care unit (NICU) was above the rate of comparable NICUs in the Vermont Oxford Network. To reduce the rate of preterm admission hypothermia, a quality improvement (QI) project was implemented, utilizing the plan-do-study-act (PDSA) methodology. A guideline for delivery room thermoregulation management in <35-week infants at the University of Virginia was created and put into practice by a multidisciplinary team. Clinical practice changes in the guideline included: increasing operating room temperatures, obtaining a 10-min axillary temperature, using an exothermic mattress for all infants <35 weeks, and using a polyethylene wrap for infants <32 weeks. The baseline rate of hypothermia (<36.5 °CC) was 63%. Three PDSA cycles data were completed on 168 consecutive preterm births. The post-implementation rate of hypothermia (<36.5 °C) was reduced to 30% (P<0.001). The incidence of moderate hypothermia (< 36 °C) was reduced from a baseline of 29% to a rate of 9% (P<0.001). Use of a multidisciplinary guideline to increase preterm NICU admission temperatures resulted in a decrease in hypothermic infants.

Validation of Infrared Azimuthal Model as Applied to GOES Data Over the ARM SGP

NASA Technical Reports Server (NTRS)

Gambheer, Arvind V.; Doelling, David R.; Spangenberg, Douglas A.; Minnis, Patrick

2004-01-01

The goal of this research is to identify and reduce the GOES-8 IR temperature biases, induced by a fixed geostationary position, during the course of a day. In this study, the same CERES LW window channel model is applied to GOES-8 IR temperatures during clear days over the Atmospheric Radiation Measurement-Southern Great Plains Central Facility (SCF). The model-adjusted and observed IR temperatures are compared with topof- the-atmosphere (TOA) estimated temperatures derived from a radiative transfer algorithm based on the atmospheric profile and surface radiometer measurements. This algorithm can then be incorporated to derive more accurate Ts from real-time satellite operational products.

Fractography of the high temperature hydrogen attack of a medium carbon steel

NASA Technical Reports Server (NTRS)

Melson, H. G.; Moorhead, R. D.

1975-01-01

Microscopic fracture processes were studied which are associated with hydrogen attack of a medium carbon steel in a well-controlled, high-temperature, high-purity hydrogen environment. Exposure to a hydrogen pressure and temperature of 3.5 MN/m2 and 575 C was found to degrade room temperature tensile properties with increasing exposure time. After 408 hr, yield and ultimate strengths were reduced by more than 40 percent and elongation was reduced to less than 2 percent. Initial fissure formation was found to be associated with manganese rich particles, most probably manganese oxide, aligned in the microstructure during the rolling operation. Fissure growth was found to be associated with a reduction in carbide content of the microstructure and was inhibited by the depletion of carbon. The interior surfaces of sectioned fissures or bubbles exhibit both primary and secondary cracking by intergranular separation. The grain surfaces were rough and rounded, suggesting a diffusion-associated separation process. Specimens that failed at room temperature after exposure to hydrogen were found to exhibit mixed mode fracture having varying amounts of intergranular separation, dimple formation, and cleavage, depending on exposure time.

EMPRESS: A European Project to Enhance Process Control Through Improved Temperature Measurement

NASA Astrophysics Data System (ADS)

Pearce, J. V.; Edler, F.; Elliott, C. J.; Rosso, L.; Sutton, G.; Andreu, A.; Machin, G.

2017-08-01

A new European project called EMPRESS, funded by the EURAMET program `European Metrology Program for Innovation and Research,' is described. The 3 year project, which started in the summer of 2015, is intended to substantially augment the efficiency of high-value manufacturing processes by improving temperature measurement techniques at the point of use. The project consortium has 18 partners and 5 external collaborators, from the metrology sector, high-value manufacturing, sensor manufacturing, and academia. Accurate control of temperature is key to ensuring process efficiency and product consistency and is often not achieved to the level required for modern processes. Enhanced efficiency of processes may take several forms including reduced product rejection/waste; improved energy efficiency; increased intervals between sensor recalibration/maintenance; and increased sensor reliability, i.e., reduced amount of operator intervention. Traceability of temperature measurements to the International Temperature Scale of 1990 (ITS-90) is a critical factor in establishing low measurement uncertainty and reproducible, consistent process control. Introducing such traceability in situ (i.e., within the industrial process) is a theme running through this project.

The AGT 101 advanced automotive gas turbine

NASA Technical Reports Server (NTRS)

Rackley, R. A.; Kidwell, J. R.

1982-01-01

A development program is described whose goal is the accumulation of the technology base needed by the U.S. automotive industry for the production of automotive gas turbine powertrains. Such gas turbine designs must exhibit reduced fuel consumption, a multi-fuel capability, and low exhaust emissions. The AGT101 powertrain described is a 74.6 kW, regenerated single-shaft gas turbine, operating at a maximum inlet temperature of 1644 K and coupled to a split differential gearbox and automatic overdrive transmission. The engine's single stage centrifugal compressor and single stage radial inflow turbine are mounted on a common shaft, and will operate at a maximum rotor speed of 100,000 rpm. All high temperature components, including the turbine rotor, are ceramic.

Mathematical modeling of the gas and powder flow in the (HVOF) systems to optimize their coatings quality

NASA Technical Reports Server (NTRS)

Tawfik, Hazem H.

1996-01-01

Thermally sprayed coatings have been extensively used to enhance materials properties and provide surface protection against their working environments in a number of industrial applications. Thermal barrier coatings (TBC) are used to reduce the thermal conductivity of aerospace turbine blades and improve the turbine overall thermal efficiency. TBC allows higher gas operating temperatures and lower blade material temperatures due to the thermal insulation provided by these ceramic coatings. In the automotive industry, coatings are currently applied to a number of moving parts that are subjected to friction and wear inside the engine such as pistons, cylinder liners, valves and crankshafts to enhance their wear resistance and prolong their useful operation and lifetime.

40 CFR 1039.801 - What definitions apply to this part?

Code of Federal Regulations, 2012 CFR

2012-07-01

... operation in water. Auxiliary emission-control device means any element of design that senses temperature... element of design that controls or reduces the emissions of regulated pollutants from an engine. Emission... POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Definitions...

40 CFR 1039.801 - What definitions apply to this part?

Code of Federal Regulations, 2010 CFR

2010-07-01

... operation in water. Auxiliary emission-control device means any element of design that senses temperature... element of design that controls or reduces the emissions of regulated pollutants from an engine. Emission... POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Definitions...

40 CFR 1039.801 - What definitions apply to this part?

Code of Federal Regulations, 2011 CFR

2011-07-01

... operation in water. Auxiliary emission-control device means any element of design that senses temperature... element of design that controls or reduces the emissions of regulated pollutants from an engine. Emission... POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD COMPRESSION-IGNITION ENGINES Definitions...

Compact tunable and reconfigurable microwave photonic filter for satellite payloads

NASA Astrophysics Data System (ADS)

Santos, M. C.; Yoosefi, O.

2017-11-01

The trend towards the photonic processing of electrical signals at microwave frequencies for satellite payloads is increasing at a breathtaking pace, mainly spurred by prospects of wide electrical bandwidth operation, low mass and volume, reduced electrical noise levels, immunity to electromagnetic interferences and resistance to both temperature and radiation.

History of Fuel Cell R&D at Fort Belvoir, Virginia

DTIC Science & Technology

2008-04-01

PEMFC but BOP is reduced. In many respects it behaves like a PAFC. MOLTEN CARBONATE FUEL CELL (MCFC) The MCFC operates at high temperature...clean up as required by the PEMFC . It can utilize air cooling without concern electrolyte control which greatly eases BOP issues. The PAFC is highly

Evaluation of the Effect of Water Vapor On the Performance of NASA's NMRO Catalysts for Carbon Monoxide Oxidation

NASA Technical Reports Server (NTRS)

Akyurtlu, Ates; Akyurtlu, Jale F.; Ammons, Vaughnery; Battle, Taikelia; Gay, Amy; Bray, Kyle; Washington, Boe; Schryer, David (Technical Monitor); Jordan, Jeff (Technical Monitor)

2002-01-01

The Noble Metal Reducible Oxide (NMRO) catalysts for the low temperature oxidation of carbon monoxide were developed by NASA for the reoxidation of carbon monoxide which forms by the dissociation of carbon dioxide during the operation of sealed carbon dioxide lasers. The NMRO catalyst, which consists of a noble metal in conjunction with a reducible metal oxide, was evaluated under conditions that will be encountered in a CO2 laser operation, namely temperatures in the range 298 to 373 K and no significant reaction gas components other than CO, CO2 and O2. The NMRO catalysts may have significant potential for spin-off applications such as the prevention of carbon monoxide build-up in closed spaces as in space vehicle cabins or submarines, and the elimination of the cold start-up problem of automobile exhaust catalysts. The most significant difference in the conditions of these possible future applications is the high moisture content of the gases to be processed. Lack of understanding of the effects of water vapor and high temperature on catalyst activity and operation for extended periods are currently the main stumbling blocks for the transfer of this NASA technology to be used for commercial purposes. In the original proposal the following objectives were stated: To obtain experimental data on the adsorption, desorption and reaction characteristics of CO and CO2 the catalysts under high moisture conditions; to collect evidence on the presence of carbonate and hydroxyl surface species and their involvement in the CO oxidation mechanism; and to model the reaction system using a Monte-Carlo simulation to gain insight on the various steps involved. After the work has commenced the NASA technical monitor Mr. David Scheyer informed us that there was increased interest in the possible use of the NMRO catalysts as automobile exhaust catalysts and therefore NASA wanted to know whether the catalysts can operate at high temperatures as well as with high moisture gases. At that meeting it was decided that investigation of the high temperature performance of the NMRO catalysts should be given priority and replace the Monte-Carlo simulation objective. As a result, the modified objectives of the investigation were taken as the investigation of the high-temperature activity of the NMRO catalysts, and the effect of water vapor on the performance of these catalysts.

Overview of TPS Tasks

NASA Technical Reports Server (NTRS)

Johnson, Sylvia M.

2000-01-01

The objectives of the project summarized in this viewgraph presentation are the following: (1) Develop a lightweight and low cost durable Thermal Protection System (TPS) for easy application to reusable launch vehicle payload launchers; (2) Develop quickly processed composite TPS processing and repair techniques; and (3) Develop higher temperature capability tile TPS. The benefits of this technology include reduced installation and operations cost, enhanced payload capability resulting from TPS weight reduction, and enhanced flight envelope and performance resulting from higher temperature capability TPS which can result in improved safety.

Solid Surface Combustion Experiment

NASA Image and Video Library

1994-09-12

STS064-10-011 (12 Sept. 1994) --- The Solid Surface Combustion Experiment (SSCE), designed to supply information on flame spread over solid fuel surfaces in the reduced-gravity environment of space, is pictured during flight day four operations. The middeck experiment measured the rate of spreading, the solid-phase temperature, and the gas-phase temperature of flames spreading over rectangular fuel beds. STS-64 marked the seventh trip into space for the Lewis Research Center experiment. Photo credit: NASA or National Aeronautics and Space Administration

Direct oxidation of strong waste waters, simulating combined wastes in extended-mission space cabins

NASA Technical Reports Server (NTRS)

Ross, L. W.

1973-01-01

The applications of modern technology to the resolution of the problem of solid wastes in space cabin environments was studied with emphasis on the exploration of operating conditions that would permit lowering of process temperatures in wet oxidation of combined human wastes. It was found that the ultimate degree of degradation is not enhanced by use of a catalyst. However, the rate of oxidation is increased, and the temperature of oxidation is reduced to 400 F.

Effect of thermal cycling. Final report, April 1985-January 1987

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, S.F.

The objective of this effort is to evaluate the stability of low expansion Zerodur, developmental Zerodur, ULE, and Cer-Vit as possible substrate materials for high energy laser mirrors. This effort will determine whether there is instability in developmental Zerodur, ULE and Cer-Vit over operating temperatures and coating temperatures (300-475K). Zerodur has already been shown to exhibit instability. Thermal cycling will be investigated as a possible approach to eliminate or reduce hysteresis. The effect of polishing on hysteresis will also be investigated.

Effect of thermal cycling

NASA Astrophysics Data System (ADS)

Jacobs, Stephen F.

1988-05-01

The objective of this effort is to evaluate the stability of low expansion Zerodur, developmental Zerodur, ULE, and Cer-Vit as possible substrate materials for high energy laser mirrors. This effort will determine whether there is instability in developmental Zerodur, ULE and Cer-Vit over operating temperatures and coating temperatures (300 to 475 K). Zerodur has already been shown to exhibit instability. Thermal cycling will be investigated as a possible approach to eliminate or reduce hysteresis. The effect of polishing on hysteresis will also be investigated.

Cryogenic Temperature-Gradient Foam/Substrate Tensile Tester

NASA Technical Reports Server (NTRS)

Vailhe, Christophe

2003-01-01

The figure shows a fixture for measuring the tensile strength of the bond between an aluminum substrate and a thermally insulating polymeric foam. The specimen is meant to be representative of insulating foam on an aluminum tank that holds a cryogenic liquid. Prior to the development of this fixture, tensile tests of this type were performed on foam/substrate specimens immersed in cryogenic fluids. Because the specimens were cooled to cryogenic temperatures throughout their thicknesses, they tended to become brittle and to fracture at loads below true bond tensile strengths. The present fixture is equipped to provide a thermal gradient from cryogenic temperature at the foam/substrate interface to room temperature on the opposite foam surface. The fixture includes an upper aluminum block at room temperature and a lower aluminum block cooled to -423 F (approx. -253 C) by use of liquid helium. In preparation for a test, the metal outer surface (the lower surface) of a foam/substrate specimen is bonded to the lower block and the foam outer surface (the upper surface) of the specimen is bonded to the upper block. In comparison with the through-the-thickness cooling of immersion testing, the cryogenic-to-room-temperature thermal gradient that exists during testing on this fixture is a more realistic approximation of the operational thermal condition of sprayed insulating foam on a tank of cryogenic liquid. Hence, tensile tests performed on this fixture provide more accurate indications of operational bond tensile strengths. In addition, the introduction of the present fixture reduces the cost of testing by reducing the amount of cryogenic liquid consumed and the time needed to cool a specimen.

A Passive Radio-Frequency Identification (RFID) Gas Sensor With Self-Correction Against Fluctuations of Ambient Temperature

PubMed Central

Potyrailo, Radislav A.; Surman, Cheryl

2013-01-01

Uncontrolled fluctuations of ambient temperature in the field typically greatly reduce accuracy of gas sensors. In this study, we developed an approach for the self-correction against fluctuations of ambient temperature of individual gas and vapor sensors. The main innovation of our work is in the temperature correction which is accomplished without the need for a separate uncoated reference sensor or a separate temperature sensor. Our sensors are resonant inductor-capacitor-resistor (LCR) transducers coated with sensing materials and operated as multivariable passive (battery-free) radio-frequency identification (RFID) sensors. Using our developed approach, we performed quantitation of an exemplary vapor over the temperature range from 25 to 40 °C. This technical solution will be attractive in numerous applications where temperature stabilization of a gas sensor or addition of auxiliary temperature or uncoated reference sensors is prohibitive. PMID:23956496

Simulating future water temperatures in the North Santiam River, Oregon

NASA Astrophysics Data System (ADS)

Buccola, Norman L.; Risley, John C.; Rounds, Stewart A.

2016-04-01

A previously calibrated two-dimensional hydrodynamic and water-quality model (CE-QUAL-W2) of Detroit Lake in western Oregon was used in conjunction with inflows derived from Precipitation-Runoff Modeling System (PRMS) hydrologic models to examine in-lake and downstream water temperature effects under future climate conditions. Current and hypothetical operations and structures at Detroit Dam were imposed on boundary conditions derived from downscaled General Circulation Models in base (1990-1999) and future (2059-2068) periods. Compared with the base period, future air temperatures were about 2 °C warmer year-round. Higher air temperature and lower precipitation under the future period resulted in a 23% reduction in mean annual PRMS-simulated discharge and a 1 °C increase in mean annual estimated stream temperatures flowing into the lake compared to the base period. Simulations incorporating current operational rules and minimum release rates at Detroit Dam to support downstream habitat, irrigation, and water supply during key times of year resulted in lower future lake levels. That scenario results in a lake level that is above the dam's spillway crest only about half as many days in the future compared to historical frequencies. Managing temperature downstream of Detroit Dam depends on the ability to blend warmer water from the lake's surface with cooler water from deep in the lake, and the spillway is an important release point near the lake's surface. Annual average in-lake and release temperatures from Detroit Lake warmed 1.1 °C and 1.5 °C from base to future periods under present-day dam operational rules and fill schedules. Simulated dam operations such as beginning refill of the lake 30 days earlier or reducing minimum release rates (to keep more water in the lake to retain the use of the spillway) mitigated future warming to 0.4 and 0.9 °C below existing operational scenarios during the critical autumn spawning period for endangered salmonids. A hypothetical floating surface withdrawal at Detroit Dam improved temperature control in summer and autumn (0.6 °C warmer in summer, 0.6 °C cooler in autumn compared to existing structures) without altering release rates or lake level management rules.

Controlled cooling of an electronic system for reduced energy consumption

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, Milnes P.; Iyengar, Madhusudan K.; Schmidt, Roger R.

Energy efficient control of a cooling system cooling an electronic system is provided. The control includes automatically determining at least one adjusted control setting for at least one adjustable cooling component of a cooling system cooling the electronic system. The automatically determining is based, at least in part, on power being consumed by the cooling system and temperature of a heat sink to which heat extracted by the cooling system is rejected. The automatically determining operates to reduce power consumption of the cooling system and/or the electronic system while ensuring that at least one targeted temperature associated with the coolingmore » system or the electronic system is within a desired range. The automatically determining may be based, at least in part, on one or more experimentally obtained models relating the targeted temperature and power consumption of the one or more adjustable cooling components of the cooling system.« less

Improved Stirling engine performance using jet impingement

NASA Technical Reports Server (NTRS)

Johnson, D. C.; Britt, E. J.; Thieme, L. G.

1982-01-01

Of the many factors influencing the performance of a Stirling engine, that of transferring the combustion gas heat into the working fluid is crucial. By utilizing the high heat transfer rates obtainable with a jet impingement heat transfer system, it is possible to reduce the flame temperature required for engine operation. Also, the required amount of heater tube surface area may be reduced, resulting in a decrease in the engine nonswept volume and a related increase in engine efficiency. A jet impingement heat transfer system was designed by Rasor Associates, Inc., and tested in the GPU-3 Stirling engine at the NASA Lewis Research Center. For a small penalty in pumping power (less than 0.5% of engine output) the jet impingement heat transfer system provided a higher combustion-gas-side heat transfer coefficient and a smoothing of heater temperature profiles resulting in lower combustion system temperatures and a 5 to 8% increase in engine power output and efficiency.

Characterization of a new Hencken burner with a transition from a reducing-to-oxidizing environment for fundamental coal studies

NASA Astrophysics Data System (ADS)

Adeosun, Adewale; Huang, Qian; Li, Tianxiang; Gopan, Akshay; Wang, Xuebin; Li, Shuiqing; Axelbaum, Richard L.

2018-02-01

In pulverized coal burners, coal particles usually transition from a locally reducing environment to an oxidizing environment. The locally reducing environment in the near-burner region is due to a dense region of coal particles undergoing devolatilization. Following this region, the particles move into an oxidizing environment. This "reducing-to-oxidizing" transition can influence combustion processes such as ignition, particulate formation, and char burnout. To understand these processes at a fundamental level, a system is required that mimics such a transition. Hence, we have developed and characterized a two-stage Hencken burner to evaluate the effect of the reducing-to-oxidizing transition and particle-to-particle interaction (which characterizes dense region of coal particles) on ignition and ultrafine aerosol formation. The two-stage Hencken burner allows coal particles to experience a reducing environment followed by a transition to an oxidizing environment. This work presents the results of the design and characterization of the new two-stage Hencken burner and its new coal feeder. In a unique approach to the operation of the flat-flame of the Hencken burner, the flame configurations are operated as either a normal flame or inverse flame. Gas temperatures and oxygen concentrations for the Hencken burner are measured in reducing-to-oxidizing and oxidizing environments. The results show that stable flames with well-controlled conditions, relatively uniform temperatures, and species concentrations can be achieved in both flame configurations. This new Hencken burner provides an effective system for evaluating the effect of the reducing-to-oxidizing transition and particle-to-particle interaction on early-stage processes of coal combustion such as ignition and ultrafine particle formation.

Novel Long Stroke Reciprocating Compressor for Energy Efficient Jaggery Making

NASA Astrophysics Data System (ADS)

Rane, M. V.; Uphade, D. B.

2017-08-01

Novel Long Stroke Reciprocating Compressor is analysed for jaggery making while avoiding burning of bagasse for concentrating juice. Heat of evaporated water vapour along with small compressor work is recycled to enable boiling of juice. Condensate formed during heating of juice is pure water, as oil-less compressor is used. Superheat of compressor is suppressed by flow of superheated vapours through condensate. It limits heating surface temperature and avoids caramelization of sugar. Thereby improves quality of jaggery and eliminates need to use chemicals for colour improvement. Stroke to bore ratio is 0.6 to 1.2 in conventional reciprocating drives. Long stroke in reciprocating compressors enhances heat dissipation to surrounding by providing large surface area and increases isentropic efficiency by reducing compressor outlet temperature. Longer stroke increases inlet and exit valve operation timings, which reduces inertial effects substantially. Thereby allowing use of sturdier valves. This enables handling liquid along with vapour in compressors. Thereby supressing the superheat and reducing compressor power input. Longer stroke increases stroke to clearance ratios which increases volumetric efficiency and ability of compressor to compress through higher pressure ratios efficiently. Stress-strain simulation is performed in SolidWorks for gear drive. Long Stroke Reciprocating Compressor is developed at Heat Pump Laboratory, stroke/bore 292 mm/32 mm. It is operated and tested successfully at different speeds for operational stability of components. Theoretical volumetric efficiency is 93.9% at pressure ratio 2.0. Specific energy consumption is 108.3 kWhe/m3 separated water, considering free run power.

The influence of plasma-surface interaction on the performance of tungsten at the ITER divertor vertical targets

NASA Astrophysics Data System (ADS)

De Temmerman, G.; Hirai, T.; Pitts, R. A.

2018-04-01

The tungsten (W) material in the high heat flux regions of the ITER divertor will be exposed to high fluxes of low-energy particles (e.g. H, D, T, He, Ne and/or N). Combined with long-pulse operations, this implies fluences well in excess of the highest values reached in today’s tokamak experiments. Shaping of the individual monoblock top surface and tilting of the vertical targets for leading-edge protection lead to an increased surface heat flux, and thus increased surface temperature and a reduced margin to remain below the temperature at which recrystallization and grain growth begin. Significant morphology changes are known to occur on W after exposure to high fluences of low-energy particles, be it H or He. An analysis of the formation conditions of these morphology changes is made in relation to the conditions expected at the vertical targets during different phases of operations. It is concluded that both H and He-related effects can occur in ITER. In particular, the case of He-induced nanostructure (also known as ‘fuzz’) is reviewed. Fuzz formation appears possible over a limited region of the outer vertical target, the inner target being generally a net Be deposition area. A simple analysis of the fuzz growth rate including the effect of edge-localized modes (ELMs) and the reduced thermal conductivity of fuzz shows that the fuzz thickness is likely to be limited by the occurrence of annealing during ELM-induced thermal excursions. Not only the morphology, but the material mechanical and thermal properties can be modified by plasma exposure. A review of the existing literature is made, but the existing data are insufficient to conclude quantitatively on the importance and extent of these effects for ITER. As a consequence of the high surface temperatures in ITER, W recrystallization is an important effect to consider, since it leads to a decrease in material strength. An approach is proposed here to develop an operational budget for the W material, i.e. the time the divertor material can be operated at a given temperature before a significant fraction of the material is recrystallized. In general, while it is clear that significant surface damage can occur during ITER operations, the tolerable level of damage in terms of plasma operations currently remains unknown.

Improving turbine performance by cooling inlet air using a waste heat powered ejector refrigerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kowalski, G.J.

1996-12-31

Stationary turbines are used to produce electricity in many areas of the world. Their performance is adversely affected by high ambient temperatures. Several means of reducing the turbine inlet temperature (offpeak water chiller and ice storage and absorption refrigeration systems) are being proposed as a means of increasing turbine output. In the present investigation the feasibility of increasing turbine output power by using its exhaust gases to power an ejector refrigeration system is demonstrated. The advantages of the ejector refrigeration are: it operates on a non-CFC fluid, its small number of moving parts and its small size. The analysis focusesmore » on United Technologies FT4 turbine with a base load output of 21.6 MW. It is demonstrated that the proposed system can decrease the turbine inlet temperature from 296.2 K to 277.6 K which increases the turbine output by 12.8% during periods of high ambient temperature and improves yearly averaged power output by 5.5% in a temperature climate. It is shown that the energy in the turbine exhaust has the potential of producing additional cooling beyond that required to reduce the inlet temperature.« less

Demonstration, Testing and Qualification of a High Temperature, High Speed Magnetic Thrust Bearing

NASA Technical Reports Server (NTRS)

DeWitt, Kenneth

2005-01-01

The gas turbine industry has a continued interest in improving engine performance and reducing net operating and maintenance costs. These goals are being realized because of advancements in aeroelasticity, materials, and computational tools such as CFD and engine simulations. These advancements aid in increasing engine thrust-to-weight ratios, specific fuel consumption, pressure ratios, and overall reliability through higher speed, higher temperature, and more efficient engine operation. Currently, rolling element bearing and squeeze film dampers are used to support rotors in gas turbine engines. Present ball bearing configurations are limited in speed (<2 million DN) and temperature (<5OO F) and require both cooling air and an elaborate lubrication system. Also, ball bearings require extensive preventative maintenance in order to assure their safe operation. Since these bearings are at their operational limits, new technologies must be found in order to take advantage of other advances. Magnetic bearings are well suited to operate at extreme temperatures and higher rotational speeds and are a promising solution to the problems that conventional rolling element bearings present. Magnetic bearing technology is being developed worldwide and is considered an enabling technology for new engine designs. Using magnetic bearings, turbine and compressor spools can be radically redesigned to be significantly larger and stiffer with better damping and higher rotational speeds. These advances, a direct result of magnetic bearing technology, will allow significant increases in engine power and efficiency. Also, magnetic bearings allow for real-time, in-situ health monitoring of the system, lower maintenance costs and down time.

Method of increasing the phase stability and the compressive yield strength of uranium-1 to 3 wt. % zirconium alloy

DOEpatents

Anderson, Robert C.

1986-01-01

A uranium-1 to 3 wt. % zirconium alloy characterized by high strength, high ductility and stable microstructure is fabricated by an improved thermal mechanical process. A homogenous ingot of the alloy which has been reduced in thickness of at least 50% in the two-step forging operation, rolled into a plate with a 75% reduction and then heated in vacuum at a temperature of about 750.degree. to 850.degree. C. and then quenched in water is subjected to further thermal-mechanical operation steps to increase the compressive yield strength approximately 30%, stabilize the microstructure, and decrease the variations in mechanical properties throughout the plate is provided. These thermal-mechanical steps are achieved by cold rolling the quenched plate to reduce the thickness thereof about 8 to 12%, aging the cold rolled plate at a first temperature of about 325.degree. to 375.degree. C. for five to six hours and then aging the plate at a higher temperature ranging from 480.degree. to 500.degree. C. for five to six hours prior to cooling the billet to ambient conditions and sizing the billet or plate into articles provides the desired increase in mechanical properties and phase stability throughout the plate.

Lightweight Exhaust Manifold and Exhaust Pipe Ducting for Internal Combustion Engines

NASA Technical Reports Server (NTRS)

Northam, G. Burton (Inventor); Ransone, Philip O. (Inventor); Rivers, H. Kevin (Inventor)

1999-01-01

An improved exhaust system for an internal combustion gasoline-and/or diesel-fueled engine includes an engine exhaust manifold which has been fabricated from carbon- carbon composite materials in operative association with an exhaust pipe ducting which has been fabricated from carbon-carbon composite materials. When compared to conventional steel. cast iron. or ceramic-lined iron paris. the use of carbon-carbon composite exhaust-gas manifolds and exhaust pipe ducting reduces the overall weight of the engine. which allows for improved acceleration and fuel efficiency: permits operation at higher temperatures without a loss of strength: reduces the "through-the wall" heat loss, which increases engine cycle and turbocharger efficiency and ensures faster "light-off" of catalytic converters: and, with an optional thermal reactor, reduces emission of major pollutants, i.e. hydrocarbons and carbon monoxide.

Performance Evaluation of a Nanofluid-Based Direct Absorption Solar Collector with Parabolic Trough Concentrator

PubMed Central

Xu, Guoying; Chen, Wei; Deng, Shiming; Zhang, Xiaosong; Zhao, Sainan

2015-01-01

Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors’ tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid’s temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed. PMID:28347112

Performance Evaluation of a Nanofluid-Based Direct Absorption Solar Collector with Parabolic Trough Concentrator.

PubMed

Xu, Guoying; Chen, Wei; Deng, Shiming; Zhang, Xiaosong; Zhao, Sainan

2015-12-04

Application of solar collectors for hot water supply, space heating, and cooling plays a significant role in reducing building energy consumption. For conventional solar collectors, solar radiation is absorbed by spectral selective coating on the collectors' tube/plate wall. The poor durability of the coating can lead to an increased manufacturing cost and unreliability for a solar collector operated at a higher temperature. Therefore, a novel nanofluid-based direct absorption solar collector (NDASC) employing uncoated collector tubes has been proposed, and its operating characteristics for medium-temperature solar collection were theoretically and experimentally studied in this paper. CuO/oil nanofluid was prepared and used as working fluid of the NDASC. The heat-transfer mechanism of the NDASC with parabolic trough concentrator was theoretically evaluated and compared with a conventional indirect absorption solar collector (IASC). The theoretical analysis results suggested that the fluid's temperature distribution in the NDASC was much more uniform than that in the IASC, and an enhanced collection efficiency could be achieved for the NDASC operated within a preferred working temperature range. To demonstrate the feasibility of the proposed NDASC, experimental performances of an NDASC and an IASC with the same parabolic trough concentrator were furthermore evaluated and comparatively discussed.

Data mining of space heating system performance in affordable housing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ren, Xiaoxin; Yan, Da; Hong, Tianzhen

The space heating in residential buildings accounts for a considerable amount of the primary energy use. Therefore, understanding the operation and performance of space heating systems becomes crucial in improving occupant comfort while reducing energy use. This study investigated the behavior of occupants adjusting their thermostat settings and heating system operations in a 62-unit affordable housing complex in Revere, Massachusetts, USA. The data mining methods, including clustering approach and decision trees, were used to ascertain occupant behavior patterns. Data tabulating ON/OFF space heating states was assessed, to provide a better understanding of the intermittent operation of space heating systems inmore » terms of system cycling frequency and the duration of each operation. The decision tree was used to verify the link between room temperature settings, house and heating system characteristics and the heating energy use. The results suggest that the majority of apartments show fairly constant room temperature profiles with limited variations during a day or between weekday and weekend. Data clustering results revealed six typical patterns of room temperature profiles during the heating season. Space heating systems cycled more frequently than anticipated due to a tight range of room thermostat settings and potentially oversized heating capacities. In conclusion, from this study affirm data mining techniques are an effective method to analyze large datasets and extract hidden patterns to inform design and improve operations.« less

Data mining of space heating system performance in affordable housing

DOE PAGES

Ren, Xiaoxin; Yan, Da; Hong, Tianzhen

2015-02-16

The space heating in residential buildings accounts for a considerable amount of the primary energy use. Therefore, understanding the operation and performance of space heating systems becomes crucial in improving occupant comfort while reducing energy use. This study investigated the behavior of occupants adjusting their thermostat settings and heating system operations in a 62-unit affordable housing complex in Revere, Massachusetts, USA. The data mining methods, including clustering approach and decision trees, were used to ascertain occupant behavior patterns. Data tabulating ON/OFF space heating states was assessed, to provide a better understanding of the intermittent operation of space heating systems inmore » terms of system cycling frequency and the duration of each operation. The decision tree was used to verify the link between room temperature settings, house and heating system characteristics and the heating energy use. The results suggest that the majority of apartments show fairly constant room temperature profiles with limited variations during a day or between weekday and weekend. Data clustering results revealed six typical patterns of room temperature profiles during the heating season. Space heating systems cycled more frequently than anticipated due to a tight range of room thermostat settings and potentially oversized heating capacities. In conclusion, from this study affirm data mining techniques are an effective method to analyze large datasets and extract hidden patterns to inform design and improve operations.« less

Thermal energy storage with geothermal triplet for space heating and cooling

NASA Astrophysics Data System (ADS)

Bloemendal, Martin; Hartog, Niels

2017-04-01

Many governmental organizations and private companies have set high targets in avoiding CO2 emissions and reducing energy (Kamp, 2015; Ministry-of-Economic-affairs, 2016). ATES systems use groundwater wells to overcome the discrepancy in time between the availability of heat (during summer) and the demand for heat (during winter). Aquifer Thermal Energy Storage is an increasingly popular technique; currently over 2000 ATES systems are operational in the Netherlands (Graaf et al., 2016). High temperature ATES may help to improve performance of these conventional ATES systems. ATES systems use heat pumps to get the stored heat to the required temperature for heating of around 40-50°C and to produce the cold water for cooling in summer. These heat pumps need quite a lot of power to run; on average an ATES system produces 3-4 times less CO2 emission compared to conventional. Over 60% of those emission are accounted for by the heat pump (Dekker, 2016). This heat pump power consumption can be reduced by utilizing other sources of sustainable heat and cooling capacity for storage in the subsurface. At such operating temperatures the required storage temperatures do no longer match the return temperatures in the building systems. Therefore additional components and an additional well are required to increase the groundwater temperature in summer (e.g. solar collectors) and decrease it in winter (e.g. dry coolers). To prevent "pollution" of the warm and cold well return water from the building can be stored in a third well until weather conditions are suitable for producing the required storage temperature. Simulations and an economical evaluation show great potential for this type of aquifer thermal energy storage; economic performance is better than normal ATES while the emissions are reduce by a factor ten. At larger temperature differences, also the volume of groundwater required to pump around is much less, which causes an additional energy saving. Research now focusses on energy balance and energy loss in the subsurface, well design requirements, working/operational conditions of each well, as well as building system components like the influence of weather conditions on performance of system components. At EGU we like to present and discuss the results of this research. references • Dekker, L.d., 2016. Bepalende factoren voor goed functionerende WKO, kennisplatform bodemenergie. • Graaf, A.d., Heijer, R., Postma, S., 2016. Evaluatie Wijzigingsbesluit bodemenergiesystemen. Buro 38 in commision of ministry of Intrastructure and environment, Cothen. • Kamp, H., 2015. Warmtevisie, ministry of economic affairs, Den Haag. • Ministry-of-Economic-affairs, 2016. Energieagenda, Naar een CO₂-arme energievoorziening. Ministry of Economic affairs, Den Haag.

Elucidation of major contributors involved in nitrogen removal and transcription level of nitrogen-cycling genes in activated sludge from WWTPs

NASA Astrophysics Data System (ADS)

Che, You; Liang, Peixin; Gong, Ting; Cao, Xiangyu; Zhao, Ying; Yang, Chao; Song, Cunjiang

2017-03-01

We investigated nitrogen-cycle bacterial communities in activated sludge from 8 municipal wastewater treatment plants (WWTPs). Redundancy analyses (RDA) showed that temperature was the most significant driving force in shaping microbial community structure, followed by influent NH4+ and total nitrogen (TN). The diversity of ammonia oxidizing and nitrite reducing bacteria were investigated by the construction of amoA, nirS and nirK gene clone libraries. Phylogenetic analysis indicated that Thauera and Mesorhizobium were the predominant nitrite reducing bacteria, and Nitrosomonas was the only detected ammonia oxidizing bacteria in all samples. Quantification of transcription level of nirS and nirK genes indicated that nirS-type nitrite reducing bacteria played the dominant roles in nitrite reduction process. Transcription level of nirS gene positively correlated with influent NH4+ and TN significantly, whereas inversely linked with hydraulic retention time. Temperature had a strong positive correlation to transcription level of amoA gene. Overall, this study deepened our understanding of the major types of ammonia oxidizing and nitrite reducing bacteria in activated sludge of municipal WWTPs. The relationship between transcription level of nitrogen-cycle genes and operational or environmental variables of WWTPs revealed in this work could provide guidance for optimization of operating parameters and improving the performance of nitrogen removal.

Low Cost Manufacturing Approach of High Temperature PMC Components

NASA Technical Reports Server (NTRS)

Kannmacher, Kevin

1997-01-01

The overall objective is to develop a satisfactory sheet molding compound (SMC) of a high temperature polyimide, such as PMR-11-50, VCAP-75, or NB2-76, and to develop compression molding processing parameters for a random, chopped fiber, high temperature, sheet molding compound that will be more affordable than the traditional hand lay-up fabrication methods. Compression molding will reduce manufacturing costs of composites by: (1) minimizing the conventional machining required after fabrication due to the use of full 360 deg matched tooling, (2) reducing fabrication time by minimizing the intensive hand lay-up operations associated with individual ply fabrication techniques, such as ply orientation and ply count and (3) possibly reducing component mold time by advanced B-staging prior to molding. This program is an integral part of Allison's T406/AE engine family's growth plan, which will utilize technologies developed under NASA's Sub-sonic Transport (AST) programs, UHPTET initiatives, and internally through Allison's IR&D projects. Allison is aggressively pursuing this next generation of engines, with both commercial and military applications, by reducing the overall weight of the engine through the incorporation of advanced, lightweight, high temperature materials, such as polymer matrix composites. This infusion of new materials into the engine is also a major factor in reducing engine cost because it permits the use of physically smaller structural components to achieve the same thrust levels as the generation that it replaced. A lighter, more efficient propulsion system translates to a substantial cost and weight savings to an airframe's structure.

Energy saving opportunities in the refrigerated transport sector through Phase Change Materials (PCMs) application

NASA Astrophysics Data System (ADS)

Principi, P.; Fioretti, R.; Copertaro, B.

2017-11-01

Transportation of food products at controlled temperature is a critical task in the transport sector. In fact, whilst there is a need of ensuring both food quality and safety to the global population, its impact in terms of energy consumption and related CO2 emissions into the atmosphere is becoming increasingly evident. In this regard, Thermal Energy Storage (TES) using Phase Change Materials (PCMs) can be considered as a potential way of reducing the cooling load, energy consumption and related greenhouse gas emissions in refrigerated transport sector. In this paper two different PCM applications are investigated. Specifically, in the first study a PCM (35 °C melting temperature) layer was added to the external side of a refrigerated enclosure wall with the aim of managing the cooling peak (shifting and reducing) and reducing the daily energy rate. Outdoor experimental results showed that the added PCM layer helps to reduce (between 5.55% and 8.57%) and delay (between 4.30 h and 3.30 h) the peak load of incoming heat compared to the reference one. In the second study, the energy performance of a refrigerated chamber with an air heat exchanger containing PCM (5°C melting temperature) was investigated. The study purpose was to reduce the cooling energy consumption during steady state operating conditions and the rate of temperature increase throughout the course of a power failure event. Test results showed that using a PCM air heat exchanger addition, up to 16% of energy can be saved.

Long-Life, Lightweight, Multi-Roller Traction Drives for Planetary Vehicle Surface Exploration

NASA Technical Reports Server (NTRS)

Klein, Richard C.; Fusaro, Robert L.; Dimofte, Florin

2012-01-01

NASA s initiative for Lunar and Martian exploration will require long lived, robust drive systems for manned vehicles that must operate in hostile environments. The operation of these mechanical drives will pose a problem because of the existing extreme operating conditions. Some of these extreme conditions include operating at a very high or very cold temperature, operating over a wide range of temperatures, operating in very dusty environments, operating in a very high radiation environment, and operating in possibly corrosive environments. Current drive systems use gears with various configurations of teeth. These gears must be lubricated with oil (or grease) and must have some sort of a lubricant resupply system. For drive systems, oil poses problems such as evaporation, becoming too viscous and eventually freezing at cold temperatures, being too thin to lubricate at high temperatures, being degraded by the radiation environment, being contaminated by the regolith (soil), and if vaporized (and not sealed), it will contaminate the regolith. Thus, it may not be advisable or even possible to use oil because of these limitations. An oil-less, compact traction vehicle drive is a drive designed for use in hostile environments like those that will be encountered on planetary surfaces. Initially, traction roller tests in vacuum were conducted to obtain traction and endurance data needed for designing the drives. From that data, a traction drive was designed that would fit into a prototype lunar rover vehicle, and this design data was used to construct several traction drives. These drives were then tested in air to determine their performance characteristics, and if any final corrections to the designs were necessary. A limitation with current speed reducer systems such as planetary gears and harmonic drives is the high-contact stresses that occur at tooth engagement and in the harmonic drive wave generator interface. These high stresses induce high wear of solid lubricant coatings, thus necessitating the use of liquid lubricants for long life.

Syn-Fuel reciprocating charge pump improvement program. Quarterly technical project report, April-June 1984

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1984-01-01

Major accomplishments during the second quarter of 1984 were completion of the Diaphragm Separation Seal clear liquid testing, and initiation of Phase III Field Testing. Diaphragm operational testing was conducted on a clear water test loop. The test goals were to ensure; mechanical reliability of the Diaphragm Seal, safe operation with simulated component failure, and proper operation of the Diaphragm Buffer Volume Control System. This latter system is essential in controlling the phasing of the diaphragm with its driving plunger. These tests were completed successfully. All operational problems were solved. However, it must be emphasized that the Diaphragm Seal wouldmore » be damaged by allowing the pump to operate in a cavitating condition for an extended period of time. A change in the Field Test phase of the program was made regarding choice of field test site. There is no operating Syn-Fuel pilot plant capable of inexpensively producing the slurry stream required for the reciprocating pump testing. The Field Tests will now be conducted by first testing the prototype pump and separation seals in an ambient temperature sand water slurry. This will determine resistence to abrasive wear and determine any operation problems at pressure over a lengthy period of time. After successful conclusion of these tests the pump and seals will be operated with a high temperature oil, but without solids, to identify any problems associated with thermal gradients, thermal shock and differential growth. After successful completion of the high temperature clean oil tests the pump will be deemed ready for in-line installation at a designated Syn-Fuel pilot plant. The above approach avoids the expense and complications of a separate hot slurry test loop. It also reduces risk of operational problems while in-line at the pilot plant. 5 figs.« less

The effect of cool water ingestion on gastrointestinal pill temperature.

PubMed

Wilkinson, David M; Carter, James M; Richmond, Victoria L; Blacker, Sam D; Rayson, Mark P

2008-03-01

Telemetric gastrointestinal (GI) temperature pills are now commonly used to measure core body temperature and could minimize the risk of heat illness while maximizing operational effectiveness in workers subject to high levels of thermal strain. To quantify the effect of repeated cool water ingestion on the accuracy of GI pill temperature. Ten operational firefighters ingested a pill to measure GI temperature (T1int) before overnight sleep. Two hours following breakfast and 11.5 h after ingesting T1int, the firefighters ingested a second pill (T2int) before performing 8.5 h of intermittent activity (repetitive cycles of 30 min of seated rest followed by 30 min of general firefighter duties). During the first 2 min of each 30-min rest period, the firefighters consumed 250 mL of chilled water (5-8 degrees C). Water ingestion had a highly variable effect both within and between subjects in transiently (32 +/- 10 min) reducing the temperature of T2int in comparison with T1int. In general, this transient reduction in T2int became progressively smaller as time following ingestion increased. In some firefighters, the difference between T1int and T2int became negligible (+/- 0.1 degrees C) after 3 h, whereas in two others, large differences (peaking at 2.0 degrees C and 6.3 degrees C) were still observed when water was consumed 8 h after pill ingestion. These results show that a GI pill ingested immediately prior to physical activity cannot be used to measure core body temperature accurately in all individuals during the following 8 h when cool fluids are regularly ingested. This makes GI temperature measurement unsuitable for workers who respond to emergency deployments when regular fluid consumption is recommended operational practice.

High-Temperature Solar Cell Development

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Raffaelle, Ryne P.; Merritt, Danielle

2004-01-01

The vast majority of satellites and near-earth probes developed to date have relied upon photovoltaic power generation. If future missions to probe environments close to the sun will be able to use photovoltaic power, solar cells that can function at high temperatures, under high light intensity, and high radiation conditions must be developed. For example, the equilibrium temperature of a Mercury surface station will be about 450 C, and the temperature of solar arrays on the proposed "Solar Probe" mission will extend to temperatures as high as 2000 C (although it is likely that the craft will operate on stored power rather than solar energy during the closest approach to the sun). Advanced thermal design principles, such as replacing some of the solar array area with reflectors, off-pointing, and designing the cells to reflect rather than absorb light out of the band of peak response, can reduce these operating temperature somewhat. Nevertheless, it is desirable to develop approaches to high-temperature solar cell design that can operate under temperature extremes far greater than today's cells. Solar cells made from wide bandgap (WBG) compound semiconductors are an obvious choice for such an application. In order to aid in the experimental development of such solar cells, we have initiated a program studying the theoretical and experimental photovoltaic performance of wide bandgap materials. In particular, we have been investigating the use of GaP, SiC, and GaN materials for space solar cells. We will present theoretical results on the limitations on current cell technologies and the photovoltaic performance of these wide-bandgap solar cells in a variety of space conditions. We will also give an overview of some of NASA's cell developmental efforts in this area and discuss possible future mission applications.

Development of HIDEC adaptive engine control systems

NASA Technical Reports Server (NTRS)

Landy, R. J.; Yonke, W. A.; Stewart, J. F.

1986-01-01

The purpose of NASA's Highly Integrated Digital Electronic Control (HIDEC) flight research program is the development of integrated flight propulsion control modes, and the evaluation of their benefits aboard an F-15 test aircraft. HIDEC program phases are discussed, with attention to the Adaptive Engine Control System (ADECS I); this involves the upgrading of PW1128 engines for operation at higher engine pressure ratios and the production of greater thrust. ADECS II will involve the development of a constant thrust mode which will significantly reduce turbine operating temperatures.

Multichannel temperature controller for hot air solar house

NASA Technical Reports Server (NTRS)

Currie, J. R.

1979-01-01

This paper describes an electronic controller that is optimized to operate a hot air solar system. Thermal information is obtained from copper constantan thermocouples and a wall-type thermostat. The signals from the thermocouples are processed through a single amplifier using a multiplexing scheme. The multiplexing reduces the component count and automatically calibrates the thermocouple amplifier. The processed signals connect to some simple logic that selects one of the four operating modes. This simple, inexpensive, and reliable scheme is well suited to control hot air solar systems.

A reconfigurable cryogenic platform for the classical control of quantum processors

NASA Astrophysics Data System (ADS)

Homulle, Harald; Visser, Stefan; Patra, Bishnu; Ferrari, Giorgio; Prati, Enrico; Sebastiano, Fabio; Charbon, Edoardo

2017-04-01

The implementation of a classical control infrastructure for large-scale quantum computers is challenging due to the need for integration and processing time, which is constrained by coherence time. We propose a cryogenic reconfigurable platform as the heart of the control infrastructure implementing the digital error-correction control loop. The platform is implemented on a field-programmable gate array (FPGA) that supports the functionality required by several qubit technologies and that can operate close to the physical qubits over a temperature range from 4 K to 300 K. This work focuses on the extensive characterization of the electronic platform over this temperature range. All major FPGA building blocks (such as look-up tables (LUTs), carry chains (CARRY4), mixed-mode clock manager (MMCM), phase-locked loop (PLL), block random access memory, and IDELAY2 (programmable delay element)) operate correctly and the logic speed is very stable. The logic speed of LUTs and CARRY4 changes less then 5%, whereas the jitter of MMCM and PLL clock managers is reduced by 20%. The stability is finally demonstrated by operating an integrated 1.2 GSa/s analog-to-digital converter (ADC) with a relatively stable performance over temperature. The ADCs effective number of bits drops from 6 to 4.5 bits when operating at 15 K.

A reconfigurable cryogenic platform for the classical control of quantum processors.

PubMed

Homulle, Harald; Visser, Stefan; Patra, Bishnu; Ferrari, Giorgio; Prati, Enrico; Sebastiano, Fabio; Charbon, Edoardo

2017-04-01

The implementation of a classical control infrastructure for large-scale quantum computers is challenging due to the need for integration and processing time, which is constrained by coherence time. We propose a cryogenic reconfigurable platform as the heart of the control infrastructure implementing the digital error-correction control loop. The platform is implemented on a field-programmable gate array (FPGA) that supports the functionality required by several qubit technologies and that can operate close to the physical qubits over a temperature range from 4 K to 300 K. This work focuses on the extensive characterization of the electronic platform over this temperature range. All major FPGA building blocks (such as look-up tables (LUTs), carry chains (CARRY4), mixed-mode clock manager (MMCM), phase-locked loop (PLL), block random access memory, and IDELAY2 (programmable delay element)) operate correctly and the logic speed is very stable. The logic speed of LUTs and CARRY4 changes less then 5%, whereas the jitter of MMCM and PLL clock managers is reduced by 20%. The stability is finally demonstrated by operating an integrated 1.2 GSa/s analog-to-digital converter (ADC) with a relatively stable performance over temperature. The ADCs effective number of bits drops from 6 to 4.5 bits when operating at 15 K.

Experimental and modeling study of high performance direct carbon solid oxide fuel cell with in situ catalytic steam-carbon gasification reaction

NASA Astrophysics Data System (ADS)

Xu, Haoran; Chen, Bin; Zhang, Houcheng; Tan, Peng; Yang, Guangming; Irvine, John T. S.; Ni, Meng

2018-04-01

In this paper, 2D models for direct carbon solid oxide fuel cells (DC-SOFCs) with in situ catalytic steam-carbon gasification reaction are developed. The simulation results are found to be in good agreement with experimental data. The performance of DC-SOFCs with and without catalyst are compared at different operating potential, anode inlet gas flow rate and operating temperature. It is found that adding suitable catalyst can significantly speed up the in situ steam-carbon gasification reaction and improve the performance of DC-SOFC with H2O as gasification agent. The potential of syngas and electricity co-generation from the fuel cell is also evaluated, where the composition of H2 and CO in syngas can be adjusted by controlling the anode inlet gas flow rate. In addition, the performance DC-SOFCs and the percentage of fuel in the outlet gas are both increased with increasing operating temperature. At a reduced temperature (below 800 °C), good performance of DC-SOFC can still be obtained with in-situ catalytic carbon gasification by steam. The results of this study form a solid foundation to understand the important effect of catalyst and related operating conditions on H2O-assisted DC-SOFCs.

CALCULATED REGENERATOR PERFORMANCE AT 4 K WITH HELIUM-4 AND HELIUM-3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radebaugh, Ray; Huang Yonghua; O'Gallagher, Agnes

2008-03-16

The helium-4 working fluid in regenerative cryocoolers operating with the cold end near 4 K deviates considerably from an ideal gas. As a result, losses in the regenerator, given by the time-averaged enthalpy flux, are increased and are strong functions of the operating pressure and temperature. Helium-3, with its lower boiling point, behaves somewhat closer to an ideal gas in this low temperature range and can reduce the losses in 4 K regenerators. An analytical model is used to find the fluid properties that strongly influence the regenerator losses as well as the gross refrigeration power. The thermodynamic and transportmore » properties of helium-3 were incorporated into the latest NIST regenerator numerical model, known as REGEN3.3, which was used to model regenerator performance with either helium-4 or helium-3. With this model we show how the use of helium-3 in place of helium-4 can improve the performance of 4 K regenerative cryocoolers. The effects of operating pressure, warm-end temperature, and frequency on regenerators with helium-4 and helium-3 are investigated and compared. The results are used to find optimum operating conditions. The frequency range investigated varies from 1 Hz to 30 Hz, with particular emphasis on higher frequencies.« less

Monitoring of hot pipes at the power plant Neurath using guided waves

NASA Astrophysics Data System (ADS)

Weihnacht, Bianca; Klesse, Thomas; Neubeck, Robert; Schubert, Lars

2013-04-01

In order to reduce the CO2-emissions and to increase the energy efficiency, the operating temperatures of power plants will be increased up to 720°C. This demands for novel high-performance steels in the piping systems. Higher temperatures lead to a higher risk of damage and have a direct impact on the structure stability and the deposition structure. Adequately trusted results for the prediction of the residual service life of those high strength steels are not available so far. To overcome these problems the implementation of an online monitoring system in addition to periodic testing is needed. RWE operates the lignite power plant Neurath. All test and research activities have to be checked regarding their safety and have to be coordinated with the business operation of the plant. An extra bypass was established for this research and made the investigations independent from the power plant operating. In order to protect the actuators and sensors from the heat radiated from the pipe, waveguides were welded to the bypass. The data was evaluated regarding their dependencies on the environmental influences like temperature and correction algorithms were developed. Furthermore, damages were introduced into the pipe with diameters of 8 mm to 10 mm and successfully detected by the acoustic method.

Silicon solar cell development and radiation effects study for low temperature and low illumination intensity operation, volume 2

NASA Technical Reports Server (NTRS)

Kirkpatrick, A. R.

1972-01-01

The results are presented of a study to determine the effect of in-situ proton irradiation upon low temperature, low intensity performance of several cell types. The cell types were selected in an attempt to distinguish variations in temperature-dependent radiation resistance which could be attributed to the n-p or p-n structure, diffused or implanted junctions, crucible grown or float-zone type base material, and high or low base resistivity. The results indicate that while expected variations of performance occur at room temperature, all cell types degrade more or less similarly at lower temperatures with normalized degradation becoming increasingly rapid as temperature is reduced. Recommendations for an optimized cell for Jupiter probe use are included along with a definition of the testing required on these cells to insure good performance characteristics.

Multi-spectral temperature measurement method for gas turbine blade

NASA Astrophysics Data System (ADS)

Gao, Shan; Feng, Chi; Wang, Lixin; Li, Dong

2016-02-01

One of the basic methods to improve both the thermal efficiency and power output of a gas turbine is to increase the firing temperature. However, gas turbine blades are easily damaged in harsh high-temperature and high-pressure environments. Therefore, ensuring that the blade temperature remains within the design limits is very important. There are unsolved problems in blade temperature measurement, relating to the emissivity of the blade surface, influences of the combustion gases, and reflections of radiant energy from the surroundings. In this study, the emissivity of blade surfaces has been measured, with errors reduced by a fitting method, influences of the combustion gases have been calculated for different operational conditions, and a reflection model has been built. An iterative computing method is proposed for calculating blade temperatures, and the experimental results show that this method has high precision.

1.55 um aluminum gallium indium arsenide strained MQW laser diodes

NASA Astrophysics Data System (ADS)

Yang, Chi

At the 1.55 mum eye-safe, telecommunications operating wavelength, semiconductor diode lasers must have low threshold currents and operate at high temperatures without thermoelectric coolers. Existing diode lasers in this wavelength range based on the GaInAsP/InP materials system are very sensitive to operating temperature. To obtain high temperature, high power 1.55 mum semiconductor diode lasers, the AlGaInAs/InP materials system with strained quantum well (QW) active regions was investigated with the goal of improving temperature performance. A set of lasers with active regions consisting of different numbers of QWs (2 to 4) and different QW strains (1.2% and 1.6%) were designed taking into account the quaternary alloy bandgap of AlGaInAs, the effect of strain on the bandgap, and the quantum size effects within the QW. The active region growth temperature was optimized using photoluminescence intensity. The wafers were first processed into broad-area lasers and measured under pulsed injection. The characteristic threshold current temperature, T0, for all AlGaInAs lasers was higher (60-70 K) than for GaInAsP lasers. No strong dependence of temperature parameters on strain was observed, while properties varied significantly with the number of QWs. With more QWs, both internal efficiency and T0 increases, but internal loss increases, reducing the characteristic temperature of the differential efficiency T1. The results show that uncooled laser operation at 1.55 mum is very promising with strained AlGaInAs QWs. Ridge waveguide devices demonstrated low threshold and high output power as well as good temperature performance under continuous wave operation. Devices with different ridge heights were fabricated from one wafer and their performance was compared. It was found that current spreading was significant in these devices and a simple current density-versus-applied voltage analysis was developed to determine the spreading factor. The analysis shows that the current spreading was not effectively limited until etching went below the doped cladding layer. A recombination coefficient analysis was performed to investigate the effect of strain on Auger recombination predicted by theory. An indirect method to infer both the nonradiative recombination coefficient and the Auger recombination coefficient was initially used. The measured values of the recombination coefficients were consistent with theoretical predictions and measurements based on other material systems. The Auger recombination was lower than expected, indicating that Auger recombination is reduced in these strained QWs. To understand the carrier dynamics, impedance measurements were carried out for the first time in AlGaInAs strained QW lasers. A small-signal, sub-threshold equivalent circuit model was derived from the laser rate equations to model the measured laser impedance. Several characteristic carrier lifetimes were obtained directly from these electrical impedance measurements. From the temperature dependence of the QW escape time, it was found that hole rather than electron leakage is dominant in the AlGaInAs system due to the relatively low valence band offset. This may explain why the improvement of T0 in AlGaInAs QW 1.55 mum active regions is limited.

Pre-operative Screening and Manual Drilling Strategies to Reduce the Risk of Thermal Injury During Minimally Invasive Cochlear Implantation Surgery.

PubMed

Dillon, Neal P; Fichera, Loris; Kesler, Kyle; Zuniga, M Geraldine; Mitchell, Jason E; Webster, Robert J; Labadie, Robert F

2017-09-01

This article presents the development and experimental validation of a methodology to reduce the risk of thermal injury to the facial nerve during minimally invasive cochlear implantation surgery. The first step in this methodology is a pre-operative screening process, in which medical imaging is used to identify those patients that present a significant risk of developing high temperatures at the facial nerve during the drilling phase of the procedure. Such a risk is calculated based on the density of the bone along the drilling path and the thermal conductance between the drilling path and the nerve, and provides a criterion to exclude high-risk patients from receiving the minimally invasive procedure. The second component of the methodology is a drilling strategy for manually-guided drilling near the facial nerve. The strategy utilizes interval drilling and mechanical constraints to enable better control over the procedure and the resulting generation of heat. The approach is tested in fresh cadaver temporal bones using a thermal camera to monitor temperature near the facial nerve. Results indicate that pre-operative screening may successfully exclude high-risk patients and that the proposed drilling strategy enables safe drilling for low-to-moderate risk patients.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, S.; Dhar, A., E-mail: adhar@phy.iitkgp.ernet.in

Highlights: • Alternative to chemically crosslinking of PMMA to achieve low leakage in provided. • Effect of LiF in reducing gate leakage through the OFET device is studied. • Effect of gate leakage on transistor performance has been investigated. • Low voltage operable and low temperature processed n-channel OFETs were fabricated. - Abstract: We report low temperature processed, low voltage operable n-channel organic field effect transistors (OFETs) using N,N′-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C{sub 8}) organic semiconductor and poly(methylmethacrylate) (PMMA)/lithium fluoride (LiF) bilayer gate dielectric. We have studied the role of LiF buffer dielectric in effectively reducing the gate leakage through the device andmore » thus obtaining superior performance in contrast to the single layer PMMA dielectric devices. The bilayer OFET devices had a low threshold voltage (V{sub t}) of the order of 5.3 V. The typical values of saturation electron mobility (μ{sub s}), on/off ratio and inverse sub-threshold slope (S) for the range of devices made were estimated to be 2.8 × 10{sup −3} cm{sup 2}/V s, 385, and 3.8 V/decade respectively. Our work thus provides a potential substitution for much complicated process of chemically crosslinking PMMA to achieve low leakage, high capacitance, and thus low operating voltage OFETs.« less

Proposing a new iterative learning control algorithm based on a non-linear least square formulation - Minimising draw-in errors

NASA Astrophysics Data System (ADS)

Endelt, B.

2017-09-01

Forming operation are subject to external disturbances and changing operating conditions e.g. new material batch, increasing tool temperature due to plastic work, material properties and lubrication is sensitive to tool temperature. It is generally accepted that forming operations are not stable over time and it is not uncommon to adjust the process parameters during the first half hour production, indicating that process instability is gradually developing over time. Thus, in-process feedback control scheme might not-be necessary to stabilize the process and an alternative approach is to apply an iterative learning algorithm, which can learn from previously produced parts i.e. a self learning system which gradually reduces error based on historical process information. What is proposed in the paper is a simple algorithm which can be applied to a wide range of sheet-metal forming processes. The input to the algorithm is the final flange edge geometry and the basic idea is to reduce the least-square error between the current flange geometry and a reference geometry using a non-linear least square algorithm. The ILC scheme is applied to a square deep-drawing and the Numisheet’08 S-rail benchmark problem, the numerical tests shows that the proposed control scheme is able control and stabilise both processes.

Advanced High Temperature Structural Seals

NASA Technical Reports Server (NTRS)

Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Shorey, Mark W.; Steinetz, Bruce (Technical Monitor)

2000-01-01

This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 lb payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs. During the first phase of this program the existing launch vehicle control surface sealing concepts were reviewed, the aerothermal environment for a high temperature seal design was analyzed and a mock up of an arc-jet test fixture for evaluating seal concepts was fabricated.

Temperature dependence of critical current and transport current losses of 4 mm YBCO coated conductors manufactured using nonmagnetic substrate

NASA Astrophysics Data System (ADS)

Kvitkovic, J.; Hatwar, R.; Pamidi, S. V.; Fleshler, S.; Thieme, C.

2015-12-01

The temperature dependence of the critical current and AC losses were measured on American Superconductor Corporation's (AMSC) second generation high temperature superconducting (2G HTS) wire produced by Rolling Assisted Biaxially Textured Substrate (RABiTS) and Metal Organic Deposition (MOD) process. Wires manufactured with two types of substrates were characterized. The magnetic substrate with composition Ni5a%W exhibits a magnetic signature and has non-negligible AC losses in AC power applications. A new nonmagnetic substrate with an alloy composition Ni9a%W has been developed by AMSC to address the AC losses in 2G HTS. The data presented show that the performance of the new conductor is identical to the conductor with magnetic substrate in terms of critical current density. The data on AC losses demonstrate the absence of ferromagnetic loss component in the new conductor and significantly reduced AC losses at low to moderate values of I/Ic. The reduced losses will translate into reduced capital costs and lower operating costs of superconducting electrical devices for AC applications.

Technology Solutions Case Study: Improving Comfort in Hot-Humid Climates with a Whole-House Dehumidifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2013-11-01

In order to quantify the performance of a combined whole-house dehumidifier (WHD) AC system, researchers from the Consortium of Advanced Residential Buildings (CARB) team monitored the operation of two Lennox AC systems coupled with a Honeywell DH150 TrueDRY whole-house dehumidifier for a six-month period. By using a WHD to control moisture levels (latent cooling) and optimizing a central AC to control temperature (sensible cooling), improvements in comfort can be achieved while reducing utility costs. Indoor comfort for this study was defined as maintaining indoor conditions at below 60% RH and a humidity ratio of 0.012 lbm/lbm while at common drymore » bulb set point temperatures of 74°-80°F. In addition to enhanced comfort, controlling moisture to these levels can reduce the risk of other potential issues such as mold growth, pests, and building component degradation. Because a standard AC must also reduce dry bulb air temperature in order to remove moisture, a WHD is typically needed to support these latent loads when sensible heat removal is not desired.« less

Automation, Operation, and Data Analysis in the Cryogenic, High Accuracy, Refraction Measuring System (CHARMS)

NASA Technical Reports Server (NTRS)

Frey, Bradley J.; Leviton, Douglas B.

2005-01-01

The Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA's Goddard Space Flight Center has been enhanced in a number of ways in the last year to allow the system to accurately collect refracted beam deviation readings automatically over a range of temperatures from 15 K to well beyond room temperature with high sampling density in both wavelength and temperature. The engineering details which make this possible are presented. The methods by which the most accurate angular measurements are made and the corresponding data reduction methods used to reduce thousands of observed angles to a handful of refractive index values are also discussed.

Automation, Operation, and Data Analysis in the Cryogenic, High Accuracy, Refraction Measuring System (CHARMS)

NASA Technical Reports Server (NTRS)

Frey, Bradley; Leviton, Duoglas

2005-01-01

The Cryogenic High Accuracy Refraction Measuring System (CHARMS) at NASA s Goddard Space Flight Center has been enhanced in a number of ways in the last year to allow the system to accurately collect refracted beam deviation readings automatically over a range of temperatures from 15 K to well beyond room temperature with high sampling density in both wavelength and temperature. The engineering details which make this possible are presented. The methods by which the most accurate angular measurements are made and the corresponding data reduction methods used to reduce thousands of observed angles to a handful of refractive index values are also discussed.

Transient performance and temperature field of a natural convection air dehumidifier loop

NASA Astrophysics Data System (ADS)

Fazilati, Mohammad Ali; Sedaghat, Ahmad; Alemrajabi, Ali-Akbar

2017-07-01

In this paper, transient performance of the previously introduced natural convection heat and mass transfer loop is investigated for an air dehumidifier system. The performance of the loop is studied in different conditions of heat source/heat sink temperature and different startup desiccant concentrations. Unlike conventional loops, it is observed that natural convection of the fluid originates from the heat sink towards the heat source. The proper operation of the cycle is highly dependent on the heat sink/heat source temperatures. To reduce the time constant of the system, a proper desiccant concentration should be adopted for charge of the loop.

Study of flue-gas temperature difference in supercritical once-through boiler

NASA Astrophysics Data System (ADS)

Kang, Yanchang; Li, Bing; Song, Ang

2018-02-01

The 600 MW coal-fired once-through Boilers with opposed firing at a power plant are found to experience marked temperature variation and even overtemperature on the wall of the heating surface as a result of flue-gas temperature (FGT) variation in the boiler. In this study, operational adjustments were made to the pulverizing, combustion, and secondary air box systems in these boilers, in order to solve problems in internal combustion. The adjustments were found to reduce FGT difference and optimize the boiler’ combustion conditions. The results of this study can provide a reference for optimization of coal-fired boiler of the same type in similar conditions.

Development of high temperature liquid lubricants for low-heat rejection heavy duty diesel engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiczynski, T.A.; Marolewski, T.A.

1993-03-01

Objective was to develop a liquid lubricant that will allow advanced diesel engines to operate at top ring reversal temperatures approaching 500 C and lubricant sump temperatures approaching 250 C. Base stock screening showed that aromatic esters and diesters has the lowest deposit level, compared to polyol esters, poly-alpha-olefins, or refined mineral oil of comparable viscosity. Classical aryl and alkyl ZDP antiwear additives are ineffective in reducing wear with aromatic esters; the phosphate ester was a much better antiwear additive, and polyol esters are more amenable to ZDP treatment. Zeolites and clays were evaluated for filtration.

Optimized molten salt receivers for ultimate trough solar fields

NASA Astrophysics Data System (ADS)

Riffelmann, Klaus-J.; Richert, Timo; Kuckelkorn, Thomas

2016-05-01

Today parabolic trough collectors are the most successful concentrating solar power (CSP) technology. For the next development step new systems with increased operation temperature and new heat transfer fluids (HTF) are currently developed. Although the first power tower projects have successfully been realized, up to now there is no evidence of an all-dominant economic or technical advantage of power tower or parabolic trough. The development of parabolic trough technology towards higher performance and significant cost reduction have led to significant improvements in competitiveness. The use of molten salt instead of synthetic oil as heat transfer fluid will bring down the levelized costs of electricity (LCOE) even further while providing dispatchable energy with high capacity factors. FLABEG has developed the Ultimate TroughTM (UT) collector, jointly with sbp Sonne GmbH and supported by public funds. Due to its validated high optical accuracy, the collector is very suitable to operate efficiently at elevated temperatures up to 550 °C. SCHOTT will drive the key-innovations by introducing the 4th generation solar receiver that addresses the most significant performance and cost improvement measures. The new receivers have been completely redesigned to provide a product platform that is ready for high temperature operation up to 550 °C. Moreover distinct product features have been introduced to reduce costs and risks in solar field assembly and installation. The increased material and design challenges incurred with the high temperature operation have been reflected in sophisticated qualification and validation procedures.

A balanced Kalman filter ocean data assimilation system with application to the South Australian Sea

NASA Astrophysics Data System (ADS)

Li, Yi; Toumi, Ralf

2017-08-01

In this paper, an Ensemble Kalman Filter (EnKF) based regional ocean data assimilation system has been developed and applied to the South Australian Sea. This system consists of the data assimilation algorithm provided by the NCAR Data Assimilation Research Testbed (DART) and the Regional Ocean Modelling System (ROMS). We describe the first implementation of the physical balance operator (temperature-salinity, hydrostatic and geostrophic balance) to DART, to reduce the spurious waves which may be introduced during the data assimilation process. The effect of the balance operator is validated in both an idealised shallow water model and the ROMS model real case study. In the shallow water model, the geostrophic balance operator eliminates spurious ageostrophic waves and produces a better sea surface height (SSH) and velocity analysis and forecast. Its impact increases as the sea surface height and wind stress increase. In the real case, satellite-observed sea surface temperature (SST) and SSH are assimilated in the South Australian Sea with 50 ensembles using the Ensemble Adjustment Kalman Filter (EAKF). Assimilating SSH and SST enhances the estimation of SSH and SST in the entire domain, respectively. Assimilation with the balance operator produces a more realistic simulation of surface currents and subsurface temperature profile. The best improvement is obtained when only SSH is assimilated with the balance operator. A case study with a storm suggests that the benefit of the balance operator is of particular importance under high wind stress conditions. Implementing the balance operator could be a general benefit to ocean data assimilation systems.

Large format 15μm pitch XBn detector

NASA Astrophysics Data System (ADS)

Karni, Yoram; Avnon, Eran; Ben Ezra, Michael; Berkowitz, Eyal; Cohen, Omer; Cohen, Yossef; Dobromislin, Roman; Hirsh, Itay; Klin, Olga; Klipstein, Philip; Lukomsky, Inna; Nitzani, Michal; Pivnik, Igor; Rozenberg, Omer; Shtrichman, Itay; Singer, Michael; Sulimani, Shay; Tuito, Avi; Weiss, Eliezer

2014-06-01

Over the past few years, a new type of High Operating Temperature (HOT) photon detector has been developed at SCD, which operates in the blue part of the MWIR atmospheric window (3.4 - 4.2 μm). This window is generally more transparent than the red part of the MWIR window (4.4 - 4.9 μm), and thus is especially useful for mid and long range applications. The detector has an InAsSb active layer and is based on the new "XBn" device concept, which eliminates Generation-Recombination dark current and enables operation at temperatures of 150K or higher, while maintaining excellent image quality. Such high operating temperatures reduce the cooling requirements of Focal Plane Array (FPA) detectors dramatically, and allow the use of a smaller closed-cycle Stirling cooler. As a result, the complete Integrated Detector Cooler Assembly (IDCA) has about 60% lower power consumption and a much longer lifetime compared with IDCAs based on standard InSb detectors and coolers operating at 77K. In this work we present a new large format IDCA designed for 150K operation. The 15 μm pitch 1280×1024 FPA is based on SCD's XBn technology and digital Hercules ROIC. The FPA is housed in a robust Dewar and is integrated with Ricor's K508N Stirling cryo-cooler. The IDCA has a weight of ~750 gram and its power consumption is ~ 5.5 W at a frame rate of 100Hz. The Mean Time to Failure (MTTF) of the IDCA is more than 20,000 hours, greatly facilitating 24/7 operation.

Mesospheric temperatures estimated from the meteor decay times over King Sejong Station(62.2°S, 58.8°W), Antarctica

NASA Astrophysics Data System (ADS)

Kim, J.; Kim, Y.; Jee, G.

2010-12-01

A VHF meteor radar has ben operated at King Sejong Station (62.2°S, 58.8°W), Antarctica since March 2007 for the observations of the neutral winds in the mesosphere and lower thermosphere region. In addition, the radar observation allows usto estimate the neutral temperature from the measured meteor decay times of the meteor echoes by utilizing Hocking's method (Hocking, 1999). For this temperature estimation, the meteor echoes observed from March 2007 to July 2009 were divded, for the first time, into weak and strong echoes depending on the strength of estimated relative electron line densities. The estimated temperatures are then compared the temperature measurements from the spectral airglow temperature imager (SATI) which has also been operated at the same location since 2002. The estimated temperatures from strong echoes were significantly lower than the temperatures estimated from weak echoes by on average about 31 K. As was done in most previous studies, we also derived the temperature by using all echoes without dividing into weak and strong, which produces about 10 K lower than the weak echoes. Among these hree estimated temperatures, the one from weak echoes was most similar to the SATI temperature. This result indicates that the strong echoes tend to reduce the estimated temperature and therefore need to be removed in the estimation procedure. We will also present the comparison of the estimated temperature with other measurements, for example, from the TIMED/SABER instrument and the NRLMSISE-00 empirical model results as a further validation.

Development of Advanced ISS-WPA Catalysts for Organic Oxidation at Reduced Pressure/Temperature

NASA Technical Reports Server (NTRS)

Yu, Ping; Nalette, Tim; Kayatin, Matthew

2016-01-01

The Water Processor Assembly (WPA) at International Space Station (ISS) processes a waste stream via multi-filtration beds, where inorganic and non-volatile organic contaminants are removed, and a catalytic reactor, where low molecular weight organics not removed by the adsorption process are oxidized at elevated pressure in the presence of oxygen and elevated temperature above the normal water boiling point. Operation at an elevated pressure requires a more complex system design compared to a reactor that could operate at ambient pressure. However, catalysts currently available have insufficient activity to achieve complete oxidation of the organic load at a temperature less than the water boiling point and ambient pressure. Therefore, it is highly desirable to develop a more active and efficient catalyst at ambient pressure and a moderate temperature that is less than water boiling temperature. This paper describes our efforts in developing high efficiency water processing catalysts. Different catalyst support structures and coating metals were investigated in subscale reactors and results were compared against the flight WPA catalyst. Detailed improvements achieved on alternate metal catalysts at ambient pressure and 200 F will also be presented in the paper.

Experimental performance of an internal resistance heater for Langley 6-inch expansion tube driver

NASA Technical Reports Server (NTRS)

Creel, T. R., Jr.

1972-01-01

An experimental investigation of the heating characteristics of an internal resistance heating element was conducted in the driver of the Langley 6-inch expansion tube to obtain actual operating conditions, to compare these results to theory, and to determine whether any modification need be made to the heater element. The heater was operated in pressurized helium from 138. MN/sq m to 62.1 MN/sq m. This investigation revealed large temperature variations within the heater element caused primarily by area reductions at insulator locations. These large temperature variations were reduced by welding small tabs over all grooves. Previous predictions of heater element and driver gas temperature were unacceptable so new equations were derived. These equations predict element and gas temperature within 10 percent of the test data when either the constant power cycle or the interrupted power cycle is used. Visual observation of the heater element, when exposed to the atmosphere with power on, resulted in a decision to limit the heater element to 815 K. Experimental shock Mach numbers are in good agreement with theory.

Electron-Tunneling Magnetometer

NASA Technical Reports Server (NTRS)

Kaiser, William J.; Kenny, Thomas W.; Waltman, Steven B.

1993-01-01

Electron-tunneling magnetometer is conceptual solid-state device operating at room temperature, yet offers sensitivity comparable to state-of-art magnetometers such as flux gates, search coils, and optically pumped magnetometers, with greatly reduced volume, power consumption, electronics requirements, and manufacturing cost. Micromachined from silicon wafer, and uses tunneling displacement transducer to detect magnetic forces on cantilever-supported current loop.

Microhole Test Data

DOE Data Explorer

Su, Jiann

2016-05-23

Drilling results from the microhole project at the Sandia High Operating Temperature test facility. The project is seeking to help reduce the cost of exploration and monitoring of geothermal wells and formations by drilling smaller holes. The tests were part of a control algorithm development to optimize the weight-on-bit (WOB) used during drilling with a percussive hammer.

Nox Emission Reduction in Commercial Jets Through Water Injection

NASA Technical Reports Server (NTRS)

Balepin, Vladimir; Ossello, Chris; Snyder, Chris

2002-01-01

This paper discusses a method of the nitrogen oxides (NOx) emission reduction through the injection of water in commercial turbofan engines during the takeoff and climbout cycles. In addition to emission reduction, this method can significantly reduce turbine temperature during the most demanding operational modes (takeoff and climbout) and increase engine reliability and life.

Simple gas chromatographic system for analysis of microbial respiratory gases

NASA Technical Reports Server (NTRS)

Carle, G. C.

1972-01-01

Dual column ambient temperature system, consisting of pair of capillary columns, microbead thermistor detector and micro gas-sampling valve, is used in remote life-detection equipment for space experiments. Performance outweighs advantage gained by utilizing single-column systems to reduce weight, conserve carrier gas and operate at lower power levels.

Entropy Generation Minimization in Dimethyl Ether Synthesis: A Case Study

NASA Astrophysics Data System (ADS)

Kingston, Diego; Razzitte, Adrián César

2018-04-01

Entropy generation minimization is a method that helps improve the efficiency of real processes and devices. In this article, we study the entropy production (due to chemical reactions, heat exchange and friction) in a conventional reactor that synthesizes dimethyl ether and minimize it by modifying different operating variables of the reactor, such as composition, temperature and pressure, while aiming at a fixed production of dimethyl ether. Our results indicate that it is possible to reduce the entropy production rate by nearly 70 % and that, by changing only the inlet composition, it is possible to cut it by nearly 40 %, though this comes at the expense of greater dissipation due to heat transfer. We also study the alternative of coupling the reactor with another, where dehydrogenation of methylcyclohexane takes place. In that case, entropy generation can be reduced by 54 %, when pressure, temperature and inlet molar flows are varied. These examples show that entropy generation analysis can be a valuable tool in engineering design and applications aiming at process intensification and efficient operation of plant equipment.

Burn Control in Fusion Reactors via Isotopic Fuel Tailoring

NASA Astrophysics Data System (ADS)

Boyer, Mark D.; Schuster, Eugenio

2011-10-01

The control of plasma density and temperature are among the most fundamental problems in fusion reactors and will be critical to the success of burning plasma experiments like ITER. Economic and technological constraints may require future commercial reactors to operate with low temperature, high-density plasma, for which the burn condition may be unstable. An active control system will be essential for stabilizing such operating points. In this work, a volume-averaged transport model for the energy and the densities of deuterium and tritium fuel ions, as well as the alpha particles, is used to synthesize a nonlinear feedback controller for stabilizing the burn condition. The controller makes use of ITER's planned isotopic fueling capability and controls the densities of these ions separately. The ability to modulate the DT fuel mix is exploited in order to reduce the fusion power during thermal excursions without the need for impurity injection. By moving the isotopic mix in the plasma away from the optimal 50:50 mix, the reaction rate is slowed and the alpha-particle heating is reduced to desired levels. Supported by the NSF CAREER award program (ECCS-0645086).

Further developments of 8μm pitch MCT pixels at Finmeccanica (formerly Selex ES)

NASA Astrophysics Data System (ADS)

Jeckells, David; McEwen, R. Kennedy; Bains, Sudesh; Herbert, Martin

2016-05-01

Finmeccanica (formerly Selex ES) introduced high performance mercury cadmium telluride (MCT) infrared detectors on an 8μm pitch in 2015 with their SuperHawk device which builds on standard production processes already used for the manufacture of 24μm, 20μm, 16μm and 12μm pitch devices. The flexibility of the proprietary Finmeccanica designed diode structure, used in conjunction with the mature production Metal Organic Vapour Phase Epitaxy (MOVPE) MCT growth process at Finmeccanica, enables fine control of diode electrical and optical structure including free choice of cut-off wavelength. The mesa pixel design inherently provides major system performance benefits by reducing blurring mechanisms, including optical scattering, inter-pixel cross-talk and carrier diffusion, to negligible levels. The SuperHawk detector has demonstrated unrivalled MTF and NETD performance, even when operating at temperatures in excess of 120K. The SuperHawk Integrated Detector Cooler Assembly (IDCA) benefits from recent dewar developments at Finmeccanica, which have improved thermal efficiencies while maintaining mechanical integrity over a wide range of applications, enabling use of smaller cryo-coolers to reduce system SWAP-C. Performance and qualification results are presented together with example imagery. SuperHawk provides an easy high resolution upgrade for systems currently based on standard definition 16μm and 15μm infrared detector formats. The paper also addresses further work to increase the operating temperature of the established 8μm process, exploiting High Operating Temperature (HOT) MCT at Finmeccanica, as well as options for LWIR variants of the SuperHawk device.

Materials Advance Chemical Propulsion Technology

NASA Technical Reports Server (NTRS)

2012-01-01

In the future, the Planetary Science Division of NASA's Science Mission Directorate hopes to use better-performing and lower-cost propulsion systems to send rovers, probes, and observers to places like Mars, Jupiter, and Saturn. For such purposes, a new propulsion technology called the Advanced Materials Bipropellant Rocket (AMBR) was developed under NASA's In-Space Propulsion Technology (ISPT) project, located at Glenn Research Center. As an advanced chemical propulsion system, AMBR uses nitrogen tetroxide oxidizer and hydrazine fuel to propel a spacecraft. Based on current research and development efforts, the technology shows great promise for increasing engine operation and engine lifespan, as well as lowering manufacturing costs. In developing AMBR, ISPT has several goals: to decrease the time it takes for a spacecraft to travel to its destination, reduce the cost of making the propulsion system, and lessen the weight of the propulsion system. If goals like these are met, it could result in greater capabilities for in-space science investigations. For example, if the amount (and weight) of propellant required on a spacecraft is reduced, more scientific instruments (and weight) could be added to the spacecraft. To achieve AMBR s maximum potential performance, the engine needed to be capable of operating at extremely high temperatures and pressure. To this end, ISPT required engine chambers made of iridium-coated rhenium (strong, high-temperature metallic elements) that allowed operation at temperatures close to 4,000 F. In addition, ISPT needed an advanced manufacturing technique for better coating methods to increase the strength of the engine chamber without increasing the costs of fabricating the chamber.

Influence of System Operation Method on CO2 Emissions of PV/Solar Heat/Cogeneration System

NASA Astrophysics Data System (ADS)

Oke, Shinichiro; Kemmoku, Yoshishige; Takikawa, Hirofumi; Sakakibara, Tateki

A PV/solar heat/cogeneration system is assumed to be installed in a hotel. The system is operated with various operation methods: CO2 minimum operation, fees minimum operation, seasonal operation, daytime operation and heat demand following operation. Of these five operations, the former two are virtual operations that are operated with the dynamic programming method, and the latter three are actual operations. Computer simulation is implemented using hourly data of solar radiation intensity, atmospheric temperature, electric, cooling, heating and hot water supply demands for one year, and the life-cycle CO2 emission and the total cost are calculated for every operations. The calculation results show that the virtual two and the actual three operations reduce the life-cycle CO2 emission by 21% and 13% compared with the conventional system, respectively. In regard to both the CO2 emission and the cost, there is no significant difference between the virtual two operation methods or among actual three operation methods.

High-velocity DC-VPS for diffusion and protecting barrier layers in solid oxide fuel cells (SOFCs)

NASA Astrophysics Data System (ADS)

Henne, R. H.; Franco, T.; Ruckdäschel, R.

2006-12-01

High-temperature fuel cells of the solid oxide fuel cell (SOFC) type as direct converter of chemical into electrical energy show a high potential for reducing considerably the specific energy consumption in different application fields. Of particular interest are advanced lightweight planar cells for electricity supply units in cars and other mobile systems. Such cells, in one new design, consist mainly of metallic parts, for example, of ferrite steels. These cells shall operate in the temperature range of 700 to 800 °C where oxidation and diffusion processes can be of detrimental effect on cell performance for long-term operation. Problems arise in particular by diffusion of chromium species from the interconnect or the cell containment into the electrolyte/cathode interface forming insulating phases and by the mutual diffusion of substrate and anode material, for example, iron and chromium from the ferrite into the anode and nickel from the anode into the ferrite, which in both cases reduces performance and system lifetime. Additional intermediate layers of perovskite-type material, (e.g., doped LaCrO3) applied with high-velocity direct-current vacuum plasma spraying (DC-VPS) can reduce such effects considerably if they are stable and of high electronic conductivity.

[Application of self-developed moxibustion thermometer in experiment teaching].

PubMed

Zhang, Jing; Sun, Yan; Zhang, Yongchen; Lu, Yan

2017-04-12

In order to improve the teaching quality of moxibustion experiment, a moxibustion thermometer was self-developed to monitor the real-time and continuous data of moxibustion temperature at different time points during the experiment. After teacher's explanation and demonstration of experiment process, the students used the moxibustion thermometer to monitor the change of temperature data and extended the experiment design. In the process of experiment class, the students found the temperature of the object tested increased rapidly, arrived at the highest temperature and slowly reduced. In addition, with learned knowledge, the students were able to design the feasible experiment scheme. The self-developed moxibustion thermometer operates smoothly in actual teaching, with stable experiment data and less experiment error, which obtained satisfactory teaching effect.

A review of thermal methods and technologies for diabetic foot assessment.

PubMed

Sousa, Paula; Felizardo, Virginie; Oliveira, Daniel; Couto, Rafael; Garcia, Nuno M

2015-07-01

Temperature analysis has been considered as a complementary method in medical evaluation and diagnosis. Several studies demonstrated that monitoring the temperature variations of the feet of diabetic patients can be helpful in the early identification of diabetic foot manifestations, and also in changing behaviors, which may contribute to reducing its incidence. In this review, several and most used techniques for assessing the temperature of the feet are presented, along with original published work on specific applications in diabetic foot complications. A review of solutions and equipment that operate according to the temperature assessment techniques is also presented. Finally, a comparison between the various technologies is presented, and the authors share their perspective on what will be the state of affairs in 5 years.

Effects of temperature and aerial exposure on the BOD of waste zebra mussels removed from navigational locks.

PubMed

Aldridge, D W; Payne, B S

2001-08-01

This laboratory study evaluated the effects of temperature and aerial exposure on BOD5 (5-day BOD) of waste zebra mussels of the type generated by maintenance operations on dams and navigational locks. The term waste zebra mussels includes the mussels and their associated debris with the latter including sediment, feces, pseudofeces and other small aquatic organisms. The BOD5 of waste zebra mussel was evaluated after aerial exposure of 3 and 10 days at temperatures of 5, 10, and 20 degrees C. The mean BOD5 values for waste zebra mussels in this study ranged from 18,500 to 30,600 mg O2/l. Factorial ANOVA analysis revealed that both temperature and aerial exposure had a negative effect on waste zebra mussel BOD5 (P<0.05) but there was no significant interaction effect (P = 0.119). Multiple regression analysis predicted that for the range of treatment conditions used in this study each 1 degrees C increase in temperature reduced the waste zebra mussel BOD5 by 284mg O2/l or 0.93% of the maximum mean BOD5. Each I day increase in aerial exposure reduced waste zebra mussel BOD5 by 987 mg O2/l or 3.22% of the maximum mean BOD5. Aerial exposure of waste zebra mussels substantially reduces waste BOD5.

High-Speed, High-Temperature Finger Seal Test Results

NASA Technical Reports Server (NTRS)

Proctor, Margaret P.; Kumar, Arun; Delgado, Irebert R.

2002-01-01

Finger seals have significantly lower leakage rates than conventional labyrinth seals used in gas turbine engines and are expected to decrease specific fuel consumption by over 1 percent and to decrease direct operating cost by over 0.5 percent. Their compliant design accommodates shaft growth and motion due to thermal and dynamic loads with minimal wear. The cost to fabricate these finger seals is estimated to be about half the cost to fabricate brush seals. A finger seal has been tested in NASA's High Temperature, High Speed Turbine Seal Test Rig at operating conditions up to 1200 F, 1200 ft/s, and 75 psid. Static, performance and endurance test results are presented. While seal leakage and wear performance are acceptable, further design improvements are needed to reduce the seal power loss.

Reduced graphene oxide-ZnO composites based gas sensors: A review

NASA Astrophysics Data System (ADS)

Thakare, N. B.; Raghuwanshi, F. C.; Kalyamwar, V. S.; Tamgadge, Y. S.

2018-05-01

The need to monitor and control life threatening gases has led to research and development of a wide variety of sensors using different materials and technologies. Recently rGO (reduced graphene oxide)-MOS (Metal Oxide Semiconductor) architectures have been studied for efficient and cost effective gas sensors that will operate at low temperature. In this review paper, we review latest findings and progress in rGO-ZnO composites as sensors to detect volatile and toxic gases.

Methods of Contemporary Gauge Theory

NASA Astrophysics Data System (ADS)

Makeenko, Yuri

2002-08-01

Preface; Part I. Path Integrals: 1. Operator calculus; 2. Second quantization; 3. Quantum anomalies from path integral; 4. Instantons in quantum mechanics; Part II. Lattice Gauge Theories: 5. Observables in gauge theories; 6. Gauge fields on a lattice; 7. Lattice methods; 8. Fermions on a lattice; 9. Finite temperatures; Part III. 1/N Expansion: 10. O(N) vector models; 11. Multicolor QCD; 12. QCD in loop space; 13. Matrix models; Part IV. Reduced Models: 14. Eguchi-Kawai model; 15. Twisted reduced models; 16. Non-commutative gauge theories.

Methods of Contemporary Gauge Theory

NASA Astrophysics Data System (ADS)

Makeenko, Yuri

2005-11-01

Preface; Part I. Path Integrals: 1. Operator calculus; 2. Second quantization; 3. Quantum anomalies from path integral; 4. Instantons in quantum mechanics; Part II. Lattice Gauge Theories: 5. Observables in gauge theories; 6. Gauge fields on a lattice; 7. Lattice methods; 8. Fermions on a lattice; 9. Finite temperatures; Part III. 1/N Expansion: 10. O(N) vector models; 11. Multicolor QCD; 12. QCD in loop space; 13. Matrix models; Part IV. Reduced Models: 14. Eguchi-Kawai model; 15. Twisted reduced models; 16. Non-commutative gauge theories.

Pyrolytic graphite collector development program

NASA Technical Reports Server (NTRS)

Wilkins, W. J.

1982-01-01

Pyrolytic graphite promises to have significant advantages as a material for multistage depressed collector electrodes. Among these advantages are lighter weight, improved mechanical stiffness under shock and vibration, reduced secondary electron back-streaming for higher efficiency, and reduced outgassing at higher operating temperatures. The essential properties of pyrolytic graphite and the necessary design criteria are discussed. This includes the study of suitable electrode geometries and methods of attachment to other metal and ceramic collector components consistent with typical electrical, thermal, and mechanical requirements.

Advanced AN/TPQ-37 transmitter tube

NASA Astrophysics Data System (ADS)

Giebeler, R. H.

1980-08-01

The purpose of this program is to improve the performance and reliability of the AN/TPQ-37 transmitter tube. The task is to build and test two high power, PPM focused, grid pulsed Traveling Wave Tubes (TWT) that meet the requirements of Technical Guidelines MW-119B. The TWT will employ a M-type cathode for reduced temperature operation and extended life. Gain variations will be minimized by use of in band loss techniques and weight will be reduced by using samarium cobalt magnets.

Characteristics of ring-cusp discharge chambers

NASA Technical Reports Server (NTRS)

Matossian, J. N.; Beattie, J. R.

1991-01-01

Measurements have been obtained for the operating characteristics of a 30 cm diameter ring-cusp ion thruster (RCIT), quantitatively comparing its performance parameters to those of a divergent-field J-series cluster of the same size. The high level of performance established for the RCIT is due to its maintenance of both a higher primary-electron population and Maxwellian-electron temperature, as the beam-ion production cost is reduced to its baseline value. Ion losses to the discharge-chamber walls can be reduced by an applied electrostatic field.

Kinetic Monte Carlo Simulations of Oxygen Diffusion in Environmental Barrier Coating Materials

NASA Technical Reports Server (NTRS)

Good, Brian S.

2017-01-01

Ceramic Matrix Composite (CMC) materials are of interest for use in next-generation turbine engine components, offering a number of significant advantages, including reduced weight and high operating temperatures. However, in the hot environment in which such components operate, the presence of water vapor can lead to corrosion and recession, limiting the useful life of the components. Such degradation can be reduced through the use of Environmental Barrier Coatings (EBCs) that limit the amount of oxygen and water vapor reaching the component. Candidate EBC materials include Yttrium and Ytterbium silicates. In this work we present results of kinetic Monte Carlo (kMC) simulations of oxygen diffusion, via the vacancy mechanism, in Yttrium and Ytterbium disilicates, along with a brief discussion of interstitial diffusion.

High-Temperature (1000 F) Magnetic Thrust Bearing Test Rig Completed and Operational

NASA Technical Reports Server (NTRS)

Montague, Gerald T.

2005-01-01

Large axial loads are induced on the rolling element bearings of a gas turbine. To extend bearing life, designers use pneumatic balance pistons to reduce the axial load on the bearings. A magnetic thrust bearing could replace the balance pistons to further reduce the axial load. To investigate this option, the U.S. Army Research Laboratory, the NASA Glenn Research Center, and Texas A&M University designed and fabricated a 7-in.- diameter magnetic thrust bearing to operate at 1000 F and 30,000 rpm, with a 1000-lb load capacity. This research was funded through a NASA Space Technology Transfer Act with Allison Advance Development Company under the Ultra-Efficient Engine Technology (UEET) Intelligent Propulsion Systems Foundation Technology project.

Safety and environmental aspects of organic coolants for fusion facilities

NASA Astrophysics Data System (ADS)

Natalizio, A.; Hollies, R. E.; Gierszewski, P.

1993-06-01

Organic coolants, such as OS-84, offer unique advantages for fusion reactor applications. These advantages are with respect to both reactor operation and safety. The key operational advantage is a coolant that can provide high temperature (350-400°C) at modest pressure (2-4 MPa). These temperatures are needed for conditioning the plasma-facing components and, in reactors, for achieving high thermodynamic conversion efficiencies (>40%). The key safety advantage of organic coolants is the low vapor pressure, which significantly reduces the containment pressurization transient (relative to water) following a loss of coolant event. Also, from an occupational dose viewpoint, organic coolants significantly reduce corrosion and erosion inside the cooling system and consequently reduce the quantity of activation products deposited in cooling system equipment. On the negative side, organic coolants undergo both pyrolytic and radiolytic decomposition, and are flammable. While the decomposition rate can be minimized by coolant system design (by reducing coolant inventories exposed to neutron flux and to high temperatures), decomposition products are formed and these degrade the coolant properties. Both heavy compounds and light gases are produced from the decomposition process, and both must be removed to maintain adequate coolant properties. As these hydrocarbons may become tritiated by permeation, or activated through impurities, their disposal could create an environmental concern. Because of this potential waste disposal problem, consideration has been given to the recycling of both the light and heavy products, thereby reducing the quantity of waste to be disposed. Preliminary assessments made for various fusion reactor designs, including ITER, suggest that it is feasible to use organic coolants for several applications. These applications range from first wall and blanket coolant (the most demanding with respect to decomposition), to shield and vacuum vessel cooling, to an intermediate cooling loop removing heat from a liquid metal loop and transferring it to a steam generator or heat exchanger.

Photosynthetic capacity and leaf nitrogen decline along a controlled climate gradient in provenances of two widely distributed Eucalyptus species.

PubMed

Crous, Kristine Y; Drake, John E; Aspinwall, Michael J; Sharwood, Robert E; Tjoelker, Mark G; Ghannoum, Oula

2018-05-27

Climate is an important factor limiting tree distributions and adaptation to different thermal environments may influence how tree populations respond to climate warming. Given the current rate of warming, it has been hypothesized that tree populations in warmer, more thermally stable climates may have limited capacity to respond physiologically to warming compared to populations from cooler, more seasonal climates. We determined in a controlled environment how several provenances of widely distributed Eucalyptus tereticornis and E. grandis adjusted their photosynthetic capacity to +3.5°C warming along their native distribution range (~16-38°S) and whether climate of seed origin of the provenances influenced their response to different growth temperatures. We also tested how temperature optima (T opt ) of photosynthesis and J max responded to higher growth temperatures. Our results showed increased photosynthesis rates at a standardized temperature with warming in temperate provenances, while rates in tropical provenances were reduced by about 40% compared to their temperate counterparts. Temperature optima of photosynthesis increased as provenances were exposed to warmer growth temperatures. Both species had ~30% reduced photosynthetic capacity in tropical and subtropical provenances related to reduced leaf nitrogen and leaf Rubisco content compared to temperate provenances. Tropical provenances operated closer to their thermal optimum and came within 3% of the T opt of J max during the daily temperature maxima. Hence, further warming may negatively affect C uptake and tree growth in warmer climates, whereas eucalypts in cooler climates may benefit from moderate warming. © 2018 John Wiley & Sons Ltd.

Energetics of Intermediate Temperature Solid Oxide Fuel Cell Electrolytes: Singly and Doubly doped Ceria Systems

NASA Astrophysics Data System (ADS)

Buyukkilic, Salih

Solid oxide fuel cells (SOFCs) have potential to convert chemical energy directly to electrical energy with high efficiency, with only water vapor as a by-product. However, the requirement of extremely high operating temperatures (~1000 °C) limits the use of SOFCs to only in large scale stationary applications. In order to make SOFCs a viable energy solution, enormous effort has been focused on lowering the operating temperatures below 700 °C. A low temperature operation would reduce manufacturing costs by slowing component degradation, lessening thermal mismatch problems, and sharply reducing costs of operation. In order to optimize SOFC applications, it is critical to understand the thermodynamic stabilities of electrolytes since they directly influence device stability, sustainability and performance. Rare-earth doped ceria electrolytes have emerged as promising materials for SOFC applications due to their high ionic conductivity at the intermediate temperatures (500--700 °C). However there is a fundamental lack of understanding regarding their structure, thermodynamic stability and properties. Therefore, the enthalpies of formation from constituent oxides and ionic conductivities were determined to investigate a relationship between the stability, composition, structural defects and ionic conductivity in rare earth doped ceria systems. For singly doped ceria electrolytes, we investigated the solid solution phase of bulk Ce1-xLnxO2-0.5x where Ln = Sm and Nd (0 ≤ x ≤ 0.30) and analyzed their enthalpies of formation, mixing and association, and bulk ionic conductivities while considering cation size mismatch and defect associations. It was shown that for ambient temperatures in the dilute dopant region, the positive heat of formation reaches a maximum as the system becomes increasingly less stable due to size mismatch. In concentrated region, stabilization to a certain solubility limit was observed probably due to the defect association of trivalent cations with charge-balancing oxygen vacancies. At higher temperatures near 700 °C, maximum enthalpy of formation shifts toward higher dopant concentrations, as a result of defect disordering. This concentration coincides with that of maximum ionic conductivity, extending the correlation seen previously near room temperature. It is also possible to co-dope these systems with Sm and Nd to further enhance ionic conductivity. For doubly doped ceria electrolytes, the solid solution phase of Ce1-xSm0.5xNd0.5xO2-0.5x (0 ≤ x ≤ 0.30) was investigated. It has been shown that for doubly doped ceria, the maximum enthalpy of formation occurs towards higher dopant concentration than that of singly doped counterparts, with less exothermic association enthalpies. These studies provide insight into the structure-composition-property-stability relations and aid in the rational design of the future SOFCs electrolytes.

Accelerating Acceptance of Fuel Cell Backup Power Systems - Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petrecky, James; Ashley, Christopher

2014-07-21

Since 2001, Plug Power has installed more than 800 stationary fuel cell systems worldwide. Plug Power’s prime power systems have produced approximately 6.5 million kilowatt hours of electricity and have accumulated more than 2.5 million operating hours. Intermittent, or backup, power products have been deployed with telecommunications carriers and government and utility customers in North and South America, Europe, the United Kingdom, Japan and South Africa. Some of the largest material handling operations in North America are currently using the company’s motive power units in fuel cell-powered forklifts for their warehouses, distribution centers and manufacturing facilities. The low-temperature GenSys fuelmore » cell system provides remote, off-grid and primary power where grid power is unreliable or nonexistent. Built reliable and designed rugged, low- temperature GenSys delivers continuous or backup power through even the most extreme conditions. Coupled with high-efficiency ratings, low-temperature GenSys reduces operating costs making it an economical solution for prime power requirements. Currently, field trials at telecommunication and industrial sites across the globe are proving the advantages of fuel cells—lower maintenance, fuel costs and emissions, as well as longer life—compared with traditional internal combustion engines.« less

33 CFR 159.119 - Operability test; temperature range.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Operability test; temperature... Operability test; temperature range. The device must operate in an ambient temperature of 5 °C with inlet operating fluid temperature varying from 2 °C to 32 °C and in an ambient temperature of 50 °C with inlet...

33 CFR 159.119 - Operability test; temperature range.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Operability test; temperature... Operability test; temperature range. The device must operate in an ambient temperature of 5 °C with inlet operating fluid temperature varying from 2 °C to 32 °C and in an ambient temperature of 50 °C with inlet...

33 CFR 159.119 - Operability test; temperature range.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Operability test; temperature... Operability test; temperature range. The device must operate in an ambient temperature of 5 °C with inlet operating fluid temperature varying from 2 °C to 32 °C and in an ambient temperature of 50 °C with inlet...

33 CFR 159.119 - Operability test; temperature range.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Operability test; temperature... Operability test; temperature range. The device must operate in an ambient temperature of 5 °C with inlet operating fluid temperature varying from 2 °C to 32 °C and in an ambient temperature of 50 °C with inlet...

Improvements on the stability and operation of a magnetron H - ion source

DOE PAGES

Sosa, A.; Bollinger, D. S.; Karns, P. R.; ...

2017-05-31

The magnetron H - ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. Amore » current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N 2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This study summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.« less

Improvements on the stability and operation of a magnetron H- ion source

NASA Astrophysics Data System (ADS)

Sosa, A.; Bollinger, D. S.; Karns, P. R.; Tan, C. Y.

2017-05-01

The magnetron H- ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated off-line test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine-tune its temperature. A current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This paper summarizes the studies and modifications done in the source over the past three years with the aim of improving its stability, reliability and overall performance.

Improvements on the stability and operation of a magnetron H - ion source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sosa, A.; Bollinger, D. S.; Karns, P. R.

The magnetron H - ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. Amore » current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N 2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This study summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.« less

Start-up of a sequential dry anaerobic digestion of paunch under psychrophilic and mesophilic temperatures.

PubMed

Nkemka, Valentine Nkongndem; Hao, Xiying

2018-04-01

The present laboratory study evaluated the sequential leach bed dry anaerobic digestion (DAD) of paunch under psychrophilic (22°C) and mesophilic (40°C) temperatures. Three leach bed reactors were operated under the mesophilic temperature in sequence at a solid retention time (SRT) of 40d with a new batch started 27d into the run of the previous one. A total of six batches were operated for 135d. The results showed that the mesophilic DAD of paunch was efficient, reaching methane yields of 126.9-212.1mLg -1 volatile solid (VS) and a VS reduction of 32.9-55.5%. The average daily methane production rate increased from 334.3mLd -1 to 571.4mLd -1 and 825.7mLd -1 when one, two and three leach bed reactors were in operation, respectively. The psychrophilic DAD of paunch was operated under a SRT of 100d and a total of three batches were performed in sequence for 300d with each batch starting after completion of the previous one. Improvements in the methane yield from 93.9 to 107.3 and 148.3mLg -1 VS and VS reductions of 24.8, 30.2 and 38.6% were obtained in the consecutive runs, indicating the adaptation of anaerobic microbes from mesophilic to psychrophilic temperatures. In addition, it took three runs for anaerobic microbes to reduce the volatile fatty acid accumulation observed in the first and second trials. This study demonstrates the potential of renewable energy recovery from paunch under psychrophilic and mesophilic temperatures. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

NASA Astrophysics Data System (ADS)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

Influences of superheated steam roasting on changes in sugar, amino acid and flavour active components of cocoa bean (Theobroma cacao).

PubMed

Zzaman, Wahidu; Bhat, Rajeev; Yang, Tajul Aris; Easa, Azhar Mat

2017-10-01

Roasting is one of the important unit operations in the cocoa-based industries in order to develop unique flavour in products. Cocoa beans were subjected to roasting at different temperatures and times using superheated steam. The influence of roasting temperature (150-250°C) and time (10-50 min) on sugars, free amino acids and volatile flavouring compounds were investigated. The concentration of total reducing sugars was reduced by up to 64.61, 77.22 and 82.52% with increased roasting temperature at 150, 200 and 250°C for 50 min, respectively. The hydrophobic amino acids were reduced up to 29.21, 36.41 and 48.87% with increased roasting temperature at 150, 200 and 250°C for 50 min, respectively. A number of pyrazines, esters, aldehydes, alcohols, ketones, carboxyl acids and hydrocarbons were detected in all the samples at different concentration range. Formation of the most flavour active compounds, pyrazines, were the highest concentration (2.96 mg kg -1 ) at 200°C for 10 min. The superheated steam roasting method achieves the optimum roasting condition within a short duration Therefore, the quality of cocoa beans can be improved using superheated steam during the roasting process. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Nonuniformity correction based on focal plane array temperature in uncooled long-wave infrared cameras without a shutter.

PubMed

Liang, Kun; Yang, Cailan; Peng, Li; Zhou, Bo

2017-02-01

In uncooled long-wave IR camera systems, the temperature of a focal plane array (FPA) is variable along with the environmental temperature as well as the operating time. The spatial nonuniformity of the FPA, which is partly affected by the FPA temperature, obviously changes as well, resulting in reduced image quality. This study presents a real-time nonuniformity correction algorithm based on FPA temperature to compensate for nonuniformity caused by FPA temperature fluctuation. First, gain coefficients are calculated using a two-point correction technique. Then offset parameters at different FPA temperatures are obtained and stored in tables. When the camera operates, the offset tables are called to update the current offset parameters via a temperature-dependent interpolation. Finally, the gain coefficients and offset parameters are used to correct the output of the IR camera in real time. The proposed algorithm is evaluated and compared with two representative shutterless algorithms [minimizing the sum of the squares of errors algorithm (MSSE), template-based solution algorithm (TBS)] using IR images captured by a 384×288 pixel uncooled IR camera with a 17 μm pitch. Experimental results show that this method can quickly trace the response drift of the detector units when the FPA temperature changes. The quality of the proposed algorithm is as good as MSSE, while the processing time is as short as TBS, which means the proposed algorithm is good for real-time control and at the same time has a high correction effect.

Plastic catalytic pyrolysis to fuels as tertiary polymer recycling method: effect of process conditions.

PubMed

Gulab, Hussain; Jan, Muhammad Rasul; Shah, Jasmin; Manos, George

2010-01-01

This paper presents results regarding the effect of various process conditions on the performance of a zeolite catalyst in pyrolysis of high density polyethylene. The results show that polymer catalytic degradation can be operated at relatively low catalyst content reducing the cost of a potential industrial process. As the polymer to catalyst mass ratio increases, the system becomes less active, but high temperatures compensate for this activity loss resulting in high conversion values at usual batch times and even higher yields of liquid products due to less overcracking. The results also show that high flow rate of carrier gas causes evaporation of liquid products falsifying results, as it was obvious from liquid yield results at different reaction times as well as the corresponding boiling point distributions. Furthermore, results are presented regarding temperature effects on liquid selectivity. Similar values resulted from different final reactor temperatures, which are attributed to the batch operation of the experimental equipment. Since polymer and catalyst both undergo the same temperature profile, which is the same up to a specific time independent of the final temperature. Obviously, this common temperature step determines the selectivity to specific products. However, selectivity to specific products is affected by the temperature, as shown in the corresponding boiling point distributions, with higher temperatures showing an increased selectivity to middle boiling point components (C(8)-C(9)) and lower temperatures increased selectivity to heavy components (C(14)-C(18)).

Heat Pipe Materials Compatibility

NASA Technical Reports Server (NTRS)

Eninger, J. E.; Fleischman, G. L.; Luedke, E. E.

1976-01-01

An experimental program to evaluate noncondensable gas generation in ammonia heat pipes was completed. A total of 37 heat pipes made of aluminum, stainless steel and combinations of these materials were processed by various techniques, operated at different temperatures and tested at low temperature to quantitatively determine gas generation rates. In order of increasing stability are aluminum/stainless combination, all aluminum and all stainless heat pipes. One interesting result is the identification of intentionally introduced water in the ammonia during a reflux step as a means of surface passivation to reduce gas generation in stainless-steel/aluminum heat pipes.

Comparison of different modelling approaches of drive train temperature for the purposes of wind turbine failure detection

NASA Astrophysics Data System (ADS)

Tautz-Weinert, J.; Watson, S. J.

2016-09-01

Effective condition monitoring techniques for wind turbines are needed to improve maintenance processes and reduce operational costs. Normal behaviour modelling of temperatures with information from other sensors can help to detect wear processes in drive trains. In a case study, modelling of bearing and generator temperatures is investigated with operational data from the SCADA systems of more than 100 turbines. The focus is here on automated training and testing on a farm level to enable an on-line system, which will detect failures without human interpretation. Modelling based on linear combinations, artificial neural networks, adaptive neuro-fuzzy inference systems, support vector machines and Gaussian process regression is compared. The selection of suitable modelling inputs is discussed with cross-correlation analyses and a sensitivity study, which reveals that the investigated modelling techniques react in different ways to an increased number of inputs. The case study highlights advantages of modelling with linear combinations and artificial neural networks in a feedforward configuration.

A Rapid Process for Fabricating Gas Sensors

PubMed Central

Hsiao, Chun-Ching; Luo, Li-Siang

2014-01-01

Zinc oxide (ZnO) is a low-toxicity and environmentally-friendly material applied on devices, sensors or actuators for “green” usage. A porous ZnO film deposited by a rapid process of aerosol deposition (AD) was employed as the gas-sensitive material in a CO gas sensor to reduce both manufacturing cost and time, and to further extend the AD application for a large-scale production. The relative resistance change (ΔR/R) of the ZnO gas sensor was used for gas measurement. The fabricated ZnO gas sensors were measured with operating temperatures ranging from 110 °C to 180 °C, and CO concentrations ranging from 100 ppm to 1000 ppm. The sensitivity and the response time presented good performance at increasing operating temperatures and CO concentrations. AD was successfully for applied for making ZnO gas sensors with great potential for achieving high deposition rates at low deposition temperatures, large-scale production and low cost. PMID:25010696

Microfiltration of skim milk and modified skim milk using a 0.1-µm ceramic uniform transmembrane pressure system at temperatures of 50, 55, 60, and 65°C.

PubMed

Hurt, E E; Adams, M C; Barbano, D M

2015-02-01

Increasing the temperature of microfiltration (MF) to >50°C may allow for operation at higher fluxes and reduce the bacterial growth during MF. However, there is a concern that operating at higher temperatures could cause calcium phosphate precipitation that would lead to membrane fouling. Our objective was to determine the effect of operating a 0.1-µm ceramic uniform transmembrane pressure MF unit at temperatures of 50, 55, 60, and 65°C on membrane fouling and serum protein (SP) removal from skim milk with and without removal of low-molecular-weight soluble milk components by ultrafiltration (UF) before MF at a flux of 54kg/m(2) per hour. For each replicate, 1,000kg of pasteurized skim milk was split into 2 batches. One batch was ultrafiltered (with diafiltration) to remove an average of 89±2% of the lactose and a percentage of the soluble calcium and phosphorus. The retentate from UF was diluted back to the protein concentration of skim milk, creating the diluted UF retentate (DUR). On subsequent days, both the DUR and skim milk were run on the MF unit with the flux maintained at 54kg/m(2) per hour and a concentration factor of 3× and the system run in recycle mode. The temperature of MF was increased in 5°C steps from 50 to 65°C, with a 1-h stabilization period after each increase. During the run, transmembrane pressure was monitored and permeate and retentate samples were taken and analyzed to determine if any changes in SP, calcium, or phosphorus passage through the membrane occurred. Increasing temperature of MF from 50 to 65°C at a flux of 54kg/m(2) per hour did not produce a large increase in membrane fouling when using either skim milk or a DUR as the MF feed type as measured by changes in transmembrane pressure. Increasing the temperature to 65°C only caused a slight reduction in calcium concentration in the permeate (11±3%) that was similar between the 2MF feed types. Increasing processing temperature reduced the percentage of SP removal by the process, but the increased temperature also caused a decrease in casein contamination in the permeate with no evidence of membrane fouling. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Suppression of vapor cell temperature error for spin-exchange-relaxation-free magnetometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Jixi, E-mail: lujixi@buaa.edu.cn; Qian, Zheng; Fang, Jiancheng

2015-08-15

This paper presents a method to reduce the vapor cell temperature error of the spin-exchange-relaxation-free (SERF) magnetometer. The fluctuation of cell temperature can induce variations of the optical rotation angle, resulting in a scale factor error of the SERF magnetometer. In order to suppress this error, we employ the variation of the probe beam absorption to offset the variation of the optical rotation angle. The theoretical discussion of our method indicates that the scale factor error introduced by the fluctuation of the cell temperature could be suppressed by setting the optical depth close to one. In our experiment, we adjustmore » the probe frequency to obtain various optical depths and then measure the variation of scale factor with respect to the corresponding cell temperature changes. Our experimental results show a good agreement with our theoretical analysis. Under our experimental condition, the error has been reduced significantly compared with those when the probe wavelength is adjusted to maximize the probe signal. The cost of this method is the reduction of the scale factor of the magnetometer. However, according to our analysis, it only has minor effect on the sensitivity under proper operating parameters.« less

Study the effect of elevated dies temperature on aluminium and steel round deep drawing

NASA Astrophysics Data System (ADS)

Lean, Yeong Wei; Azuddin, M.

2016-02-01

Round deep drawing operation can only be realized by expensive multi-step production processes. To reduce the cost of processes while expecting an acceptable result, round deep drawing can be done at elevated temperature. There are 3 common problems which are fracture, wrinkling and earing of deep drawing a round cup. The main objective is to investigate the effect of dies temperature on aluminium and steel round deep drawing; with a sub-objective of eliminate fracture and reducing wrinkling effect. Experimental method is conducted with 3 different techniques on heating the die. The techniques are heating both upper and lower dies, heating only the upper dies, and heating only the lower dies. 4 different temperatures has been chosen throughout the experiment. The experimental result then will be compared with finite element analysis software. There is a positive result from steel material on heating both upper and lower dies, where the simulation result shows comparable as experimental result. Heating both upper and lower dies will be the best among 3 types of heating techniques.

Transient thermal characteristics of high-temperature SiC power module enhanced with Al-bump technology

NASA Astrophysics Data System (ADS)

Tanisawa, Hidekazu; Kato, Fumiki; Koui, Kenichi; Sato, Shinji; Watanabe, Kinuyo; Takahashi, Hiroki; Murakami, Yoshinori; Sato, Hiroshi

2018-04-01

In this paper, we demonstrate a mounting technology that improves the tolerance to transient power loss by adding a heat capacity near the device. Silicon carbide (SiC) power devices can operate at high temperatures, up to 250 °C, at which silicon (Si) power devices cannot. Therefore, it is possible to allow a large temperature difference between the device and ambient air. Thus, the size of a power converter equipped with an SiC power module is reduced by simplifying the cooling system. The temperature of the power module is important not only in the steady state, but in transient loads as well. Therefore, we developed the Al-bump flip-chip mounting technology to increase heat capacity near the device. With this proposed structure, the heat capacity per device increased by 1.7% compared with the total heat capacity of the conventional structure using wire bonding. The reduction in transient thermal impedance is observed from 0.003 to 3 s, and we confirmed that the transient thermal impedance is reduced very efficiently by 15% at the maximum, compared with the conventional structure.

Recommendations for rationalizing cleaning-in-place in the dairy industry: case study of an ultra-high temperature heat exchanger.

PubMed

Alvarez, N; Daufin, G; Gésan-Guiziou, G

2010-02-01

The objective of this work was to propose a new strategy, based on objective and rational arguments and calculations, that can be implemented by plant designers and operators in the dairy industry to reduce operating time and the volume and load of effluents. The strategy is based on the on-line and off-line use of sensors and tracers, the accuracy, relevance, and robustness of which were evaluated for each phase of the sequence used for cleaning an industrial sterilizer. The efficient duration of each phase of the cleaning sequence (management of the end of operation) and the sorting of the fluids (management of mixtures and destination of fluids) were determined in real time. As a result, significant reduction in total overall duration of the cleaning sequence, wastewater volume (waste volume was reduced by half), and detergent volume (caustic soda and acid was reduced by up to a few tens of kilograms per cleaning) was achievable. Copyright 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

40 CFR 63.1185 - How do I establish the average operating temperature of an incinerator?

Code of Federal Regulations, 2014 CFR

2014-07-01

... operating temperature of an incinerator? 63.1185 Section 63.1185 Protection of Environment ENVIRONMENTAL... operating temperature of an incinerator? (a) During the performance test, you must establish the average operating temperature of an incinerator as follows: (1) Continuously measure the operating temperature of...

40 CFR 63.1185 - How do I establish the average operating temperature of an incinerator?

Code of Federal Regulations, 2011 CFR

2011-07-01

... operating temperature of an incinerator? 63.1185 Section 63.1185 Protection of Environment ENVIRONMENTAL... operating temperature of an incinerator? (a) During the performance test, you must establish the average operating temperature of an incinerator as follows: (1) Continuously measure the operating temperature of...

40 CFR 63.1185 - How do I establish the average operating temperature of an incinerator?

Code of Federal Regulations, 2013 CFR

2013-07-01

... operating temperature of an incinerator? 63.1185 Section 63.1185 Protection of Environment ENVIRONMENTAL... operating temperature of an incinerator? (a) During the performance test, you must establish the average operating temperature of an incinerator as follows: (1) Continuously measure the operating temperature of...