Development of an efficient alternative to recovery O 2 from metabolic CO 2 via electrolysis operated at ambient temperature and driven by a highly selective catalysis
Explore the source record for details and available documents.
Jesus Dominguez↗
SEARCH · Engineering Papers
Results for “ambient temperature”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Analysis and Experimental Tests of a High-Performance Evacuated Tubular Collector
A high-performance collector based on the use of all-glass, evacuated tubular collector elements is described and analyzed, and supporting experimental data presented. The collector operated with excellent efficiency at temperatures high enough to drive existing air conditioning units, and showed good performance under diffuse light and low insolation conditions. Collector efficiency was insensitive to operating temperature, ambient temperature, and wind speed. In addition, air, as well as liquid, can be used as the heat transfer fluid, with no significant performance penalty. While the equations governing the useful energy produced can be cast in a form similar to that for flat plate collectors, several important parameters were unique in a number of respects. The loss coefficient was unusually low, while the flow factor and effective insolation were unusually high.
Beekley, D. C.↗
Electrospun Nanofiber Coating of Fiber Materials: A Composite Toughening Approach
Textile-based composites could significantly benefit from local toughening using nanofiber coatings. Nanofibers, thermoplastic or otherwise, can be applied to the surface of the fiber tow bundle, achieving toughening of the fiber tow contact surfaces, resulting in tougher and more damage-resistant/tolerant composite structures. The same technique could also be applied to other technologies such as tape laying, fiber placement, or filament winding operations. Other modifications to the composite properties such as thermal and electrical conductivity could be made through selection of appropriate nanofiber material. Control of the needle electric potential, precursor solution, ambient temperature, ambient humidity, airflow, etc., are used to vary the diameter and nanofiber coating morphology as needed. This method produces a product with a toughening agent applied to the fiber tow or other continuous composite precursor material where it is needed (at interfaces and boundaries) without interfering with other composite processing characteristics.
Kohlman, Lee W.↗
Ca++ induced hypothermia in a hibernator /Citellus beechyi/
Results of perfusion of excess Ca++ and Na+ into the hypothalamus of the hibernating ground squirrel Citellus beechyi are presented. The significant finding is that perfused excess Ca++ causes a reduction in core temperature when ambient temperature is low (12 C). Ca++ also causes a rise in rectal temperature at high ambient temperature (33 C). Thus hypothalamic Ca++ perfusion apparently causes a nonspecific depression of thermoregulatory control.
Hanegan, J. L.↗
An Experimental Study of the Operating Temperature in a Loop Heat Pipe with Two Evaporators and Two Condensers
This paper presents a comprehensive experimental study of the loop operating temperature in a loop heat pipe (LHP) which has two parallel evaporators and two parallel condensers. In a single evaporator LHP, it is well known that the loop operating temperature is a function of the heat load, the sink temperature and the ambient temperature. The objective of the present study emphasizes on the stability of the loop operating temperature and parameters that affects the loop operation. Tests results show that the loop operating temperature is a function of the total system heat load, sink temperature, ambient temperature, and beat load distribution between the two evaporators. Under most conditions, only one compensation chamber (CC) contains two-phase fluid and controls the loop operating temperature, and the other CC is completely filled with liquid. Moreover, as the test condition changes, control of the loop operating temperature often shifted from one CC to another. In spite of complex interactions between various components, the test loop has demonstrated very robust operation even during fast transients.
Ku, Jentung↗
Silicone-Rubber Microvalves Actuated by Paraffin
Microvalves containing silicone-rubber seals actuated by heating and cooling of paraffin have been proposed for development as integral components of microfluidic systems. In comparison with other microvalves actuated by various means (electrostatic, electromagnetic, piezoelectric, pneumatic, and others), the proposed valves (1) would contain simpler structures that could be fabricated at lower cost and (2) could be actuated by simpler (and thus less expensive) control systems. Each valve according to the proposal would include a flow channel bounded on one side by a flat surface and on the other side by a curved surface defined by an arched-cross-section, elastic seal made of silicone rubber [polydimethylsilane (PDMS)]. The seal would be sized and shaped so that the elasticity of the PDMS would hold the channel open except when the seal was pressed down onto the flat surface to close the channel. The principle of actuation would exploit the fact that upon melting or freezing, the volume of a typical paraffin increases or decreases, respectively, by about 15 percent. In a valve according to the proposal, the seal face opposite that of the channel would be in contact with a piston-like plug of paraffin. In the case of a valve designed to be normally open at ambient temperature, one would use a paraffin having a melting temperature above ambient. The seal would be pushed against the flat surface to close the channel by heating the paraffin above its melting temperature. In the case of a valve designed to be normally closed at ambient temperature, one would use a paraffin having a melting temperature below ambient. The seal would be allowed to spring away from the flat surface to open the channel by cooling the paraffin below its melting temperature. The availability of paraffins that have melting temperatures from 70 to +80 C should make it possible to develop a variety of normally closed and normally open valves. The figure depicts examples of prototype normally open and normally closed valves according to the proposal. In each valve, an arch cross section defining a channel having dimensions of the order of tens of micrometers would be formed in a silicone-rubber sheet about 40 m thick. The silicone rubber sheet would be hermetically sealed to a lower glass plate that would define the sealing surface and to an upper glass plate containing a well. The well would be filled with paraffin and capped with a rigid restraining layer of epoxy. In the normally open valve, the paraffin would have a melting temperature above ambient (e.g., 40 C) and the wall of the well would be coated with a layer of titanium that would serve as an electric heater. In the normally closed valve, the paraffin would have a melting temperature below ambient (e.g.-5 C). Instead of a heater in the well, the normally closed valve would include a thermoelectric cooler on top of the epoxy cap.
Svelha, Danielle↗
Hydrostatic temperature calculations
Comparisons are made between hydrostatically computed temperatures and ambient temperatures associated with nine different data sources, including analyses, forecasts and conventional observations. Five-day averages and the day-to-day variations in the root-mean-square temperature differences are presented. Several different numerical and interpolation procedures are examined. Error correction and a constrained optimum procedure that minimizes ambient minus calculated hydrostatic temperature differences are introduced. Systematic differences between ambient and hydrostatic temperatures are found to be associated with the sinoptic situation. When compared with ambient temperatures, hydrostatic temperatures at 500 mb tend to be too warm at or in front of a trough and too cold behind the trough. In the vertical direction, for the eight-level configuration tested, the average hydrostatic temperatures are too cold at low levels (850, 700 mb) and too warm at upper levels, (300, 250 mb).
Raymond, William H.↗
Below Ambient and Cryogenic Thermal Testing
Methods and apparatus for the testing of below-ambient temperature thermal insulation systems have been developed based on boiloff calorimetry. Boiloff calorimetry provides a direct measure of heat flow for below-ambient temperature conditions. The effective thermal conductivity (ke) and heat flux (q) of a test specimen are calculated for a fixed environmental condition (warm boundary temperature; cold boundary temperature; ambient or vacuum pressure). Through its heat of vaporization, liquid nitrogen (LN2) serves as the energy meter. Different apparatus have been built for flat-plate, cylindrical, and pipeline test specimens. Boundary temperatures can range from 353 K down to 77 K (80 C to -196 C). By interposing different insulation layers on the cold boundary, the cryogenic boiloff method is suitable for a wide range of below-ambient temperature applications. A cylindrical apparatus, Cryostat-100, as well as the pipeline test apparatus, Cryostat-P100, are thermally guarded and directly measure absolute thermal performance in watts. Pipe insulation systems can be mechanical, double-walled, or vacuum-jacketed including materials such as foams, cellular glass, aerogel blankets, clam-shell panels, and multilayer insulation. Two test pipelines, 12-meter-long, are mounted between two cold box assemblies. The test pipeline diameter is from 25-mm to 76-mm while the maximum outside diameter including insulation is up to 204-mm. The cold pipe tester design and test methods are discussed, as well as results for select thermal insulation materials. Progress toward a comparative type, bench-top cold pipe tester (Cryostat-P200) is also discussed.
Fesmire, James E.↗
NASA mechanical impact testing in high-pressure oxygen
Three independently developed high-pressure gaseous oxygen mechanical impact testers have been used to evaluate materials for the Space Shuttle Program. A test program evaluating the performance of these test systems is described. The gaseous and liquid oxygen test procedures and equipment are considered along with the material selection procedures. The results of the NASA mechanical impact tester variability study are presented, including penetration function curves and curve parameters and equivalent energies and comparisons of high-pressure testers at ambient pressure and temperature, ambient temperature and 34 MPa, and cryogenic temperature and 34 MPa. Finally, a summary of NASA mechanical impact test data is presented.
Bryan, C. J.↗
Centaur engine gimbal friction characteristics under simulated thrust load
An investigation was performed to determine the friction characteristics of the engine gimbal system of the Centaur upper stage rocket. Because the Centaur requires low-gain autopilots in order to meet all stability requirements for some configurations, control performance (response to transients and limit-cycle amplitudes) depends highly on these friction characteristics. Forces required to rotate the Centaur engine gimbal system were measured under a simulated thrust load of 66,723 N (15,000 lb) and in an altitude/thermal environment. A series of tests was performed at three test conditions; ambient temperature and pressure, ambient temperature and vacuum, and cryogenic temperature and vacuum. Gimbal rotation was controlled, and tests were performed in which rotation amplitude and frequency were varied by using triangular and sinusoidal waveforms. Test data revealed an elastic characteristic of the gimbal, independent of the input signal, which was evident prior to true gimbal sliding. The torque required to initiate gimbal sliding was found to decrease when both pressure and temperature decreased. Results from the low amplitude and low frequency data are currently being used in mathematically modeling the gimbal friction characteristics for Centaur autopilot performance studies.
Askew, J. W.↗
Steps toward 8m honeycomb mirrors. VIII - Design and demonstration of a system of thermal control
Directed jets of ambient temperature air are proposed for the maintenance of low internal temperature gradients and conformity with ambient temperatures in honeycomb-structure borosilicate glass telescope mirrors. The use of greater airflow on thicker sections, to match cooling rates, and the cooling or heating of the internal, back, and edge surfaces of the mirror at the same rate established by convection on the front surface, have been tested on a full scale glass thermal model of a single honeycomb cell from an 8-m diameter mirror. The internal thermal gradient (less than 0.1 C) and ambient-temperature-change lag (less than 0.24 C) ensure minimum image degradation.
Cheng, A. Y. S.↗
Damage Assessment of Stress-Thermal Cycled high temperature
We report on the characterization of bismaleimide and polyimide carbon fiber composite, microcrack development under stress thermal cycling loading. Such cycles range from cryogenic temperatures associated with cryogenic fuel (LN, LOX) containment to high temperatures of 300 degrees Celsius associated with future hypervelocity aeropropulsion systems. Microcrack development thresholds as a function of temperature range of the thermal cycle; the number of cycles; the applied stress level imposed on the composite are reported. We have conducted stress-thermal cycles on thin bismaleimide-woven carbon fiber foils for three temperature range cycles: 1. Ambient temperature - -196 degrees celsius. 2. Ambient temperature - 150 degrees Celsius; 200 degrees Celsius; 250 degrees Celsius. 3. -196 degrees Celsius - 250 degrees Celsius. The Principle findings are that the full cycles from -196 degrees Celsius to to 250 degrees Celsius cause the most significant microcrack of development. These observations indicate that the high temperature portion of the cycle under load causes fiber-matrix interface failure and subsequent exposure to higher stresses at the cryogenic, low temperature region results in composite matrix microcracking as a result of the additional stresses associate with the fiber-matrix thermal expansion mismatch. Our initial studies for 12 ply PMR-II-50 polyimide/M60JB carbon fabric [0f,90f,90f,0f,0f,90f]ls composites will be presented. The stress-thermal cycle test procedure for these will be described. Moisture absorption characteristics between cycles will be used to monitor interconnected microcrack development. The applied stress level will be 75% of the composite cryogenic (-196 degrees Celsius) ultimate strength.
Ju, Jae-Hyung↗
Modeling of growth and evaporation effects on the extinction of 1.0-micron solar radiation traversing stratospheric sulfuric acid aerosols
The effects of growth and evaporation of stratospheric sulfuric acid aerosols on the extinction of solar radiation traversing such an aerosol medium are reported for the case of 1.0-micron solar radiation. Modeling results show that aerosol extinction is not very sensitive to the change of ambient water vapor concentration, but is sensitive to ambient temperature changes, especially at low ambient temperatures and high ambient water vapor concentration. A clarification is given of the effects of initial aerosol size distribution and composition on the change of aerosol extinction due to growth and evaporation processes. It is shown that experiments designed to observe solar radiation extinction of aerosols may also be applied to the determination of observed changes in aerosol optical properties, environmental parameters, or the physical and optical characteristics of sulfate aerosols.
Yue, G. K.↗
Ice crystal growth in a dynamic thermal diffusion chamber
Ice crystals were grown in a supersaturated environment produced by a dynamic thermal diffusion chamber, which employed two horizontal plates separated by a distance of 2.5 cm. Air was circulated between and along the 1.2 m length of the plates past ice crystals which nucleated and grew from a fiber suspended vertically between the two plates. A zoom stereo microscope with a magnification which ranged from 3X to 80X and both 35 mm still photographs and 16 mm time lapse cine films taken through the microscope were used to study the variation of the shape and linear growth rate of ice crystals as a function of the ambient temperature, the ambient supersaturation, and the forced ventilation velocity. The ambient growth conditions were varied over the range of temperature 0 to -40 C, over the range of supersaturation 4% to 50% with respect to ice, and over the range of forced ventilation velocities 0 cm/s to 20 cm/s.
Keller, V. W.↗
Thermoregulatory responses of rats to varying environmental temperatures
The peripheral (tail) circulatory responses of six male albino rats were measured at ambient temperatures between 5 and 40 C, using impedance plethysmography. Each animal was anesthetized, instrumented, and placed in a thermal environmental chamber to reach equilibrium. Tail blood flow, respiration rate, heart rate, core temperature, and tail skin temperature were then monitored at each ambient temperature. The mean tail blood flow was significantly higher (p less than 0.05) at 5 C than at 10 C. The mean blood flow increased significantly (p less than 0.01) at each of the temperatures above 10 C. Tail skin temperature and internal body (core) temperature increased significantly with increasing ambient temperature.
Berry, J. J.↗
High-Temperature Electronics: A Role for Wide Bandgap Semiconductors?
It is increasingly recognized that semiconductor based electronics that can function at ambient temperatures higher than 150 C without external cooling could greatly benefit a variety of important applications, especially-in the automotive, aerospace, and energy production industries. The fact that wide bandgap semiconductors are capable of electronic functionality at much higher temperatures than silicon has partially fueled their development, particularly in the case of SiC. It appears unlikely that wide bandgap semiconductor devices will find much use in low-power transistor applications until the ambient temperature exceeds approximately 300 C, as commercially available silicon and silicon-on-insulator technologies are already satisfying requirements for digital and analog very large scale integrated circuits in this temperature range. However, practical operation of silicon power devices at ambient temperatures above 200 C appears problematic, as self-heating at higher power levels results in high internal junction temperatures and leakages. Thus, most electronic subsystems that simultaneously require high-temperature and high-power operation will necessarily be realized using wide bandgap devices, once the technology for realizing these devices become sufficiently developed that they become widely available. Technological challenges impeding the realization of beneficial wide bandgap high ambient temperature electronics, including material growth, contacts, and packaging, are briefly discussed.
Neudeck, Philip G.↗
Two SMA-Actuated Miniature Mechanisms
The figures depict two miniature mechanisms actuated by strips made of shape-memory alloy (SMA). A typical SMA is a nickel-titanium alloy known by the trade name "Flexinol" or "Nitinol." In preparation for a typical application, a suitably sized and shaped piece of an SMA is deformed by a predetermined amount at the lower of two operating temperatures, then mounted in a mechanism. When stroking of the mechanism in one direction is desired, the piece of SMA is heated above a transition temperature to make it return to the "remembered" undeformed state. When stroking of the mechanism in the opposite direction is desired, the SMA is cooled below the transition temperature to make it return to the deformed state. Also, the SMA alloy chosen for a specific application is one that has a transition temperature somewhat above the ambient temperature, so that stroking in one direction or the opposite direction can be achieved by heating the SMA, or refraining from heating the SMA, respectively, above the transition temperature. In the present mechanisms as in typical other SMA mechanisms, the heating is effected by electric currents applied via electrical contacts at the ends of the SMA strips. The purpose served by the mechanism of Figure 1 is to lock or release a flexible latch attachment. In preparation for use in this mechanism, two initially straight SMA strips are deformed into curved springs that, when mounted in the mechanism at ambient temperature, clamp the knob at the lower end of the flexible latch attachment. When heated above their transition temperature by an electric current, the SMA strips return to their original straight configuration, thereby releasing the knob. This mechanism is redundant in the sense that as long as at least one of the two SMA strips straightens when commanded to do so, the knob is released. The mechanism of Figure 2 is suited to any of a variety of applications in which there are requirements for a small mechanism that affords lowtorque rotary actuation through a finite angular range. As shown here, the mechanism is used to rotate a coverlatch pin to a release position. In this case, a straight and flat SMA strip is torsionally deformed to a twist angle of about 90deg by use of a torsion bias spring. When the SMA strip is heated, it rotates to its original straight and flat condition.
Willey, Cliff E.↗
Qualification of the T2 wind tunnel in cryogenic operation. B: Flow fluctuations, particle detection and qualification
This report presents part of the tests for verification of the T2 transonic induction wind tunnel in cryogenic operation. The first part of the results presented concerns fluctuations in pressure and temperature at ambient temperature and in cryogenic regulation. The second part presents the condensation phenomena which could be observed in the cryogenic flow by means of an optical particle detection system in the test section.
Dor, J. B.↗