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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.

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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Maximizing the Use of Ductless Mini-Splits in Homes with Existing Central or Zonal Heating and Cooling Equipment

In the residential retrofit application, ductless mini-split heat pumps (DHP) are often reported to hold high-energy savings potential, depending on the system they are supplementing or replacing. However, of late, there have been a number of studies and analyses indicating these energy savings are not being achieved. The primary goal of this project was to determine the most cost effective (lowest cost for the most energy saved) and persistent (e.g. automated, hard to change, etc.) solution for controlling a ductless heat pump in an existing home with central forced air furnace. Various control strategies were tested at the Pacific Northwest National Laboratory Lab Homes to compare the energy savings between the different energy efficient control strategies. A maximum of 40% energy savings was realized by using the ductless mini-split as the primary heat source with the central air conditioning unit as the secondary source.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

Comparing Capacity Credit Calculations for Wind: A Case Study in Texas

The degree to which wind energy can contribute to the capacity needed to meet resource adequacy requirements, also known as capacity credit (CC), varies regionally with wind resource and correlation to net load. CC is an important metric widely used for resource planning and resource adequacy assessments. However, there are multiple methods for computing and estimating CC, depending on specific needs, access to data, and computational burden. It is unclear the extent to which the CC computation method may influence the result. To address this, we use a probabilistic resource adequacy tool and multiple approximation methods to systematically assess the CC of wind for near-term wind deployment under a case study in Texas. We find that proper consideration of transmission constraints is important; some approximation methods may overestimate the CC of wind due to a lack of consideration of transmission constraints, while other approximation methods may underestimate the CC by not capturing the ability of wind to be shipped to neighboring regions. In this case study, we find that several approximation methods do come close to the CC calculated by more robust probabilistic methods. However, the best approximation method may vary on a case-by-case basis, depending on system-specific considerations.

17 WIND ENERGY↗
DOE OSTI2022

Impact of Increased Latent Generations on Sensitivity Calculations with SCALE [Slides]

Depending on the system, energy, and/or nuclide, altering the number of latent generations can significantly impact generated sensitivity coefficients. In general, as the number of latent generations increases, the accuracy of the generated sensitivity value compared with the DP value increases and there is a significant increase in the uncertainty with generated sensitivity values. IFP generated sensitivities appear to be more stable than those with CLUTCH. Complex systems, even with IFP and increased latent generations can still produce poor results (i.e., MPC- 32). This reiterates the importance of performing DPs to confirm sensitivities. IFP-Shift and CLUTCH can take advantage of parallel computing abilities. Work continues in this area as additional parameters and calculational methods are examined to provide analysts insights to successfully generating sensitivity coefficients for confirmatory analyses and validation efforts.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Defining Detection Limits for Continuous Monitoring Systems for Methane Emissions at Oil and Gas Facilities

Networks of fixed-point continuous monitoring systems are becoming widely used in the detection and quantification of methane emissions from oil and gas facilities in the United States. Regulatory agencies and operators are developing performance metrics for these systems, such as minimum detection limits. Performance characteristics, such as minimum detection limits, would ideally be expressed in emission rate units; however, performance parameters such as detection limits for a continuous monitoring system (CMS) will depend on meteorological conditions, the characteristics of emissions at the site where the CMS is deployed, the positioning of CMS devices in relation to the emission sources, and the amount of time allowed for the CMS to detect an emission source. This means that certifying the performance of a CMS will require test protocols with well-defined emission rates and durations; initial protocols are now being used in field tests. Field testing results will vary, however, depending on meteorological conditions and the time allowed for detection. This work demonstrates methods for evaluating CMS performance characteristics using dispersion modeling and defines an approach for normalizing test results to standard meteorological conditions using dispersion modeling.

Chen, Qining (ORCID:0000000316908091)↗
DOE OSTI2026

Casimir-Polder potential on an excited atom near an atomic array

We develop a microscopic description of the fluctuation-mediated Casimir-Polder (CP) shifts on a 'test' two-level atom placed near a two-dimensional atomic array of two-level atoms. We derive the resonant and off-resonant CP potentials experienced by the excited test atom using fourth-order perturbation theory, under the assumption that the test atom resonance is far detuned from those of the array atoms. The total potential on the test atom can be described as the sum of the pairwise resonant and off-resonant potentials resulting from its interaction with the individual atoms of the array. We analyze the asymptotic scaling of CP shifts as a function of the test atom-array separation, and its dependence on various system parameters: array spacing and size, and dipole orientation of the array atoms. Our results bridge the description of CP potential across two distinct regimes: (i) from a single-atom limit where we recover the well-known two-atom Van der Waals potential, (ii) to a macroscopic boundary limit, where we demonstrate new asymptotic scaling laws. We demonstrate that these scaling laws can be tuned via the microscopic parameters of the atomic array, establishing atomically-controlled arrays as a versatile platform for tailoring fluctuation-induced QED phenomena.

FOS: Physical sciences↗
NASA NTRS1971

Classical adiabatic perturbation theory

Classical Poincare-von Zeipel canonical perturbation theory extension to adiabatically perturbed systems with slow dependence on time or dynamic variables

Stern, D. P.↗
NASA NTRS1971

Development of a highly reliable composite board for printed circuitry for use in space environment

Materials, processes and fabrication techniques have been investigated for the development of a high-temperature circuit-board laminate. High quality, void-free copper-clad laminates have been made using 7628/HS-1 style fiberglas reinforcements with filled polyimide matrices. The fabricating characteristics of P13N resin appear suitable for use as a filled matrix in this circuit board development. High-fired, ball-milled alumina appears to be necessary to obtain the desired effects in the circuit board system. Nickel-clad copper foil bonding surfaces appear to be another requirement for retention of good bond strengths after art work and plating sequences. The fabrication cycle for this circuit board system is very dependent on the heating profile. Very rapid heating with quick loading is recommended. A stack approach to lamination was successfully used.

Bradbury, E. J.↗
NASA NTRS1972

Investigation of an automatic spin prevention system for fighter airplanes

An investigation was conducted to evaluate the effectiveness of an automatic spin-prevention system for current fighter airplanes as a first step in determining the feasibility of such a system. The concept makes use of the components of the conventional flight-control system with the addition of control logic to monitor angle of attack, yaw rate, and normal acceleration. Analytical techniques were used to study the system concept applied to three representative fighter configurations, and model flight tests were employed to evaluate a prototype system on a representative fighter configuration. Emphasis was placed on the development of the control logic required. A discussion of possible implementations of the system concept is presented. Results of the investigation indicated that a relatively simple system (with full control authority) was effective in preventing the developed spins of the fighter configurations considered and that the system design is dependent on the stall and spin characteristics of the particular airplane.

Gilbert, W. P.↗
NASA NTRS1972

Thermal/structural optimization of cryogenic storage systems.

An analytical method has been developed to optimize a cryogenic storage system designed for long term storage of cryogenic propellants. The type of propellant, mission duration, thermal environment, insulation thermal properties, insulation vent time, and the storage system weight penalty imposed by the design pressure were considered as the dependent parameters. The optimum system insulation thickness and vent pressure were then calculated in terms of these parameters. The method was applied to the design of the Space Shuttle Orbiter oxygen and hydrogen tanks to obtain an optimum design. It was determined that for the mission examined, the hydrogen tank optimum design was close to the initial pressure. A continuously vented hydrogen tank, therefore, was close to the optimum design. Also, it was determined that for this particular mission the oxygen tank should not be vented.

Navickas, J.↗
NASA NTRS1975

Application of blast wave theory to explosive propulsion

An analysis was carried out by using blast wave theory to delineate the important aspects of detonating explosives in nozzles, such as flow and wave phenomena, characteristic length and time scales, and the parameters on which the specific impulse is dependent. The propulsive system utilizes the momentum of the ambient gas set into motion in the nozzle by the explosion. A somewhat simplified model was considered for the situation where the mass of ambient gas in the nozzle is much greater than the mass of gas produced in the explosion, a condition of interest for dense atmospheres, e.g., near the surface of Venus. Instantaneous detonation and energy release was presumed to occur at the apex of a conical nozzle, and the shock wave generated by the explosion was taken to propagate as a spherical wave, thereby setting the ambient gas in the nozzle into one-dimensional radially outward motion.

Back, L. H.↗
NASA NTRS1977

Molding cork sheets to complex shapes

Partially cured cork sheet is easily formed to complex shapes and then final-cured. Temperature and pressure levels required for process depend upon resin system used and final density and strength desired. Sheet can be bonded to surface during final cure, or can be first-formed in mold and bonded to surface in separate step.

Sharpe, M. H.↗
NASA NTRS1977

User access to the National Space Transportation System

Economical and efficient use of the Space Transportation System (STS) will depend to a large extent on the ability to utilize standard procedures and operations; and for early users transitioning from expendable launch vehicles, the ability to use previous procedures and documentation. Users of the STS will need to know how and where to obtain the information needed to know the STS capabilities, how to obtain a flight assignment, costs involved, and processing of their payloads in preparation for launch.

Mccoy, H. E.↗
NASA NTRS1978

A comparison of the Method of Lines to finite difference techniques in solving time-dependent partial differential equations

Steady state solutions to two time dependent partial differential systems have been obtained by the Method of Lines (MOL) and compared to those obtained by efficient standard finite difference methods: (1) Burger's equation over a finite space domain by a forward time central space explicit method, and (2) the stream function - vorticity form of viscous incompressible fluid flow in a square cavity by an alternating direction implicit (ADI) method. The standard techniques were far more computationally efficient when applicable. In the second example, converged solutions at very high Reynolds numbers were obtained by MOL, whereas solution by ADI was either unattainable or impractical. With regard to 'set up' time, solution by MOL is an attractive alternative to techniques with complicated algorithms, as much of the programming difficulty is eliminated.

Kurtz, L. A.↗
NASA NTRS1978

Interface reaction and characterization in B/Al composites

Interfacial reactions, strength degradation, and fracture morphology have been characterized in B/Al(1100) and B/Al(6061) composite systems at a volume fraction of 0.55. Reaction was promoted by isothermal exposure at 350 C or 500 C for times up to 860,000 s. Tetragonal AlB12 was identified as the reaction product in the 6061 matrix and hexagonal AlB2 in the 1100 matrix. Interface development is analyzed based on a moving boundary model modified by the addition of ternary elements. While strength decreases in both systems, the time dependence of elevated-temperature exposure is different in the two matrix materials. In the 45 deg fiber orientation, failure occurs primarily by matrix shear, whereas in the 90 deg fiber orientation, fracture morphology is characterized by a mixture of fiber splitting, ductile matrix fracture, and failure at fiber-matrix interfaces.

Kim, W. H.↗
NASA NTRS1979

Turbine sizing of a solar thermal power plant

Since the insolation is intermittent, thermal energy storage is necessary to extend the time of power generation with solar heat past sunset. There are two approaches to specifying the size of turbine-generator units depending on the system operation. In the first approach, the turbine operates at its full capacity when operating on direct solar heat, and at reduced capacity when operating on collected heat out of energy storage. In the second approach, the turbine will always operate at a uniform level either on derated energy from the receiver or from energy storage. Both of these approaches have certain advantages and disadvantages. In this paper, a simple analysis is outlined and exercised to compare the performance and economics of these two approaches.

Manvi, R.↗
NASA NTRS1979

Evolution of the International Atomic Time TAI computation

The computation of the International Atomic Time (TAI), a worldwide time reference, is briefly examined. The types of atomic clocks, computation procedures, and time intercomparison between clocks utilizing navigation satellites are addressed. Changes in the system would essentially depend on the improvement of the atomic clocks.

Granveaud, M.↗