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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1961

Effects of Surface Recombination on Heat Transfer to Bodies in a High Enthalpy Stream of Partially Dissociated Nitrogen

Heat-transfer rates to two surfaces having widely different catalytic effectiveness are compared at a Mach number of 6 in a low-density stream of partially dissociated nitrogen. The heat-transfer rate to a polished copper cylinder is twice as great as the heat-transfer rate to a silicon-monoxide-coated cylinder when the stream total energy content is 9000 Btu/lb. Various methods for determining the stream energy content, the stream velocity, and the stream Mach number have been developed and compared. It is shown that methods for estimating the stream energy content by means of purely aerodynamic concepts may neglect the sizable fraction of the stream energy contained in molecular dissociation.

Winkler, Ernest L..↗
NASA NTRS1972

Experimental and theoretical aerodynamic heating and flow field analysis of a space shuttle orbiter

The results of work on the McDonnell Douglas delta wing orbiter are summarized and compared to other data and theories where applicable. The tests were conducted in the continuous hypersonic Tunnel B at Mach 8 and in the hypervelocity hotshot Tunnel F at Mach 10.5. Photographic data are used to illustrate the regions of peak heating on the lee-side and to show the vortical nature of the flow. Windward centerline data include measurements of shock angle, surface pressure, flow field pitot pressure and total temperature, and heat transfer rate coefficient distributions. Shock angles, surface pressures, and local Mach number distributions are compared with tangent cone theory over an angle of attack range from 10 to 60 deg. The measured heat transfer rate coefficient distributions are compared to both laminar and turbulent theories and boundary layer transition data are compared to the McDonnell Douglas criteria.

Matthews, R. K.↗
DOE OSTI2024

Particle-wall heat transfer in narrow-channel bubbling fluidized beds for thermal energy storage

Robust metal oxide particles can provide low-cost and stable thermal energy storage (TES) to temperatures up to 1200 °C or higher. The transfer of heat into and out of the particles in cost-effective high-temperature particle heat exchangers remains a principal challenge to implementing particle-based TES. The present work expands on prior studies of particle-wall heat transfer in narrow-channel fluidized beds operated in the bubbling fluidization regime. Batch-mode experiments with various oxide particles over a range of temperatures and airflow rates indicate that particle-wall heat transfer increases with higher bed temperature and decreasing particle size. Measured particle-wall heat transfer coefficients in a 12 mm deep channel are fit to a Nusselt number correlation proportional to a non-monotonic function of excess fluidization velocity. Particle-wall heat transfer coefficients rise rapidly with excess fluidization velocities until reaching a maximum at intermediate air velocities due to a trade-off between enhanced transverse particle mixing and decreasing particle volume fraction with increased fluidization velocity. The heat transfer coefficient reaches a maximum of ≈ 400% of values without fluidization for oxide particles ranging in diameter d p from 159 to 408 μm. For the smallest particles tested, composed of olivine sand, particle-wall heat transfer coefficients peak above 1100 Wm –2 K –1 at 450 °C. 100-h tests at 500 °C and near-optimal heat transfer fluidization velocities indicated minimal wall wear or oxide scaling. Furthermore, high particle-wall heat transfer coefficients suggest narrow channel fluidized beds as a potential pathway for reducing the required surface area and cost of high-temperature particle heat exchangers, as needed in large-scale thermal energy storage applications.

14 SOLAR ENERGY↗
NASA NTRS2012

Investigation of Hypersonic Laminar Heating Augmentation in the Stagnation Region

Laminar stagnation region heating augmentation is investigated in the AEDC Tunnel 9 at Mach 10 by performing high frequency surface pressure and heat transfer measurements on the Orion CEV capsule at zero degree angle-of-attack for unit Reynolds numbers between 0.5 and 15 million per foot. Heating augmentation increases with Reynolds number, but is also model size dependent as it is absent on a 1.25-inch diameter model at Reynolds numbers where it reaches up to 15% on a 7-inch model. Heat transfer space-time correlations on the 7-inch model show that disturbances convect at the boundary layer edge velocity and that the streamwise integral scale increases with distance. Therefore, vorticity amplification due to stretching and piling-up in the stagnation region appears to be responsible for the stagnation point heating augmentation on the larger model. This assumption is reinforced by the f(exp -11/3) dependence of the surface pressure spectrum compared to the f(exp -1) dependence in the free stream. Vorticity amplification does not occur on the 1.25- inch model because the disturbances are too large. Improved free stream fluctuation measurements will be required to determine if significant vorticity is present upstream or mostly generated behind the bow shock.

Marineau, Eric C.↗
NASA NTRS2004

The Far Infrared Lines of OH as Molecular Cloud Diagnostics

Future IR missions should give some priority to high resolution spectroscopic observations of the set of far-IR transitions of OH. There are 15 far-IR lines arising between the lowest eight rotational levels of OH, and ISO detected nine of them. Furthermore, ISO found the OH lines, sometimes in emission and sometimes in absorption, in a wide variety of galactic and extragalactic objects ranging from AGB stars to molecular clouds to active galactic nuclei and ultra-luminous IR galaxies. The ISO/LWS Fabry-Perot resolved the 119 m doublet line in a few of the strong sources. This set of OH lines provides a uniquely important diagnostic for many reasons: the lines span a wide wavelength range (28.9 m to 163.2 m); the transitions have fast radiative rates; the abundance of the species is relatively high; the IR continuum plays an important role as a pump; the contribution from shocks is relatively minor; and, not least, the powerful centimeter-wave radiation from OH allows comparison with radio and VLBI datasets. The problem is that the large number of sensitive free parameters, and the large optical depths of the strongest lines, make modeling the full set a difficult job. The SWAS montecarlo radiative transfer code has been used to analyze the ISO/LWS spectra of a number of objects with good success, including in both the lines and the FIR continuum; the DUSTY radiative transfer code was used to insure a self-consistent continuum. Other far IR lines including those from H2O, CO, and [OI] are also in the code. The OH lines all show features which future FIR spectrometers should be able to resolve, and which will enable further refinements in the details of each cloud's structure. Some examples are given, including the case of S140, for which independent SWAS data found evidence for bulk flows.

Smith, Howard A.↗
NASA NTRS1996

Predicted Turbine Heat Transfer for a Range of Test Conditions

Comparisons are shown between predictions and experimental data for blade and endwall heat transfer. The comparisons of computational domain parisons are given for both vane and rotor geometries over an extensive range of Reynolds and Mach numbers. Comparisons are made with experimental data from a variety of sources. A number of turbulence models are available for predicting blade surface heat transfer, as well as aerodynamic performance. The results of an investigation to determine the turbulence model which gives the best agreement with experimental data over a wide range of test conditions are presented.

Boyle, R. J.↗
NASA NTRS1949

Heat Transfer from High-Temperature Surfaces to Fluids. III - Correlation of Heat-Transfer Data for Air Flowing in Silicon Carbide Tube with Rounded Entrance, Inside Diameter of 3/4 Inch, and Effective Length of 12 Inches: Correlation of Heat-Transfer Data for Air Flowing in Silicon Carbide Tube with Rounded Entrance, Inside Diameter of 3/4 Inch, and Effective Length of 12 Inches - Part 3

A heat-transfer investigation was conducted with air flowing through an electrically heated silicon carbide tube with a rounded entrance, an inside diameter of 3/4 inch, and an effective heat-transfer length of 12 inches over a range of Reynolds numbers up to 300,000 and a range of average inside-tube-wall temperature up to 2500 R. The highest corresponding local outside-tube-wall temperature was 3010 R. Correlation of the heat-transfer data using the conventional Nueselt relation wherein physical properties of the fluid were evaluated at average bulk temperature resulted in a separation of data with tube-wall-temperature level. A satisfactory correlation of the heat-transfer data was obtained, however, by the use of modified correlation parameters wherein the mass velocity G (or product of average air density and velocity evaluated at bulk temperature P(sub b)V(sub b)) in the Reynolds number was replaced by the product of average air velocity evaluated at the bulk temperature and density evaluated at either the average inside-tube-wall temperature or the average film temperature; in addition, all the physical properties of air were correspondingly evaluated at either the average inside-tube-wall temperature or the average film temperature.

Sams, Eldon W.↗
NASA NTRS1991

A new two-way time transfer modem

The use of commercial communication satellites for precise time transfer has been performed with a variety of techniques for a number of years. Military communications systems can also provide this function in a few deployed systems. A new design is demonstrated of a time transfer modem that can be produced at a reasonable cost and enable users to make direct comparisons with the Naval Observatory with nanosecond precision. A flexible all-digital design is being implemented that will enable a variety of different codes to be employed. The design and operating modes of this equipment are demonstrated.

G. P. Landis↗
NASA NTRS2020

Applying Orbital Multi-Angle Photopolarimetric Observations to Study Properties of Aerosols in the Earth's Atmosphere: Implications of Measurements in the 1.378 µm Spectral Channel to Retrieve Microphysical Characteristics and Composition of Stratospheric Aerosols

We analyze the possibilities of orbital photopolarimetric measurements to study properties of aerosols in the Earth's atmosphere. As an example, we consider the case when such measurements are performed within a narrow spectral channel centered at 1.378 µm that allows to retrieve microphysical characteristics of stratospheric aerosols separately from those of tropospheric aerosols. We consider the case of stratospheric aerosols caused by volcanic eruption, and adopt the model of the stratosphere in the form of a homogeneous plane-parallel layer composed of polydisperse spherical particles. We use numerically exact solutions of the vector radiative transfer equation to theoretically simulate measurements carried out at various numbers of scattering angles, including: (i) radiance measurements alone; (ii) polarization measurements alone; and (iii) radiance and polarization measurements together. The results of computations show that the simultaneous use of radiance and polarization measurements at a sufficiently large number of scattering angles enables one to retrieve the optical thickness, effective radius, and refractive index of aerosols with adequate accuracy. We demonstrate how the accuracy of the derived values of the optical parameters of aerosols depends on the accuracy of measurements of the intensity and polarization of the reflected light, optical thickness of aerosol layer itself, effective radius of aerosols, width of the particle size distribution, and number of viewing angles.

Aerosols↗
NASA NTRS1971

Space shuttle: Heat transfer rate measurements on Convair booster (B-15B-2) and North American Rockwell orbiter (161B) at nominal Mach number of 8

Plotted and tabulated data from the thin-skin thermocouple phase of an experimental test program are presented. These data are representative of three events of simulated flight and are described as booster-orbiter ascent heating data, booster reentry heating data, and orbiter reentry heating data. The test was conducted in a 50-inch hypersonic tunnel b at a nominal Mach number of 8 and free-stream Reynolds number range of 700,000 to 3,700,000 per foot. The model employed was a 0.009 scale replica of the Convair B-15B-2 booster and North American Rockwell 161B orbiter.

Warmbrod, J. D.↗
NASA NTRS1951

Analysis of turbulent free-convection boundary layer on flat plate

With the use of Karman's integrated momentum equation for the boundary layer and data on the wall-shearing stress and heat transfer in forced-convection flow, a calculation was carried out for the flow and heat transfer in the turbulent free-convection boundary layer on a vertical flat plate. The calculation is for a fluid with a Prandtl number that is close to 1. A formula was derived for the heat-transfer coefficient that was in good agreement with experimental data in the range of Grashof numbers from 10sup10 to 10sup12. Because of the good agreement between the theoretical formula and the experimental data, the formula may be used to obtain data for high Grashof numbers. The calculation also yielded formulas for the maximum velocity in the boundary layer and for boundary-layer thickness.

Eckert, E R G↗
NASA NTRS1992

Heat transfer from cylinders in subsonic slip flows

The heat transfer in heated wires was measured using a constant temperature anemometer over a Mach number range from 0.05 to 0.4 and pressures from 0.5 to 8.0 atmospheres. The total temperature ranged from 80 to 120 F and the wire diameters were 0.00015, 0.00032, and 0.00050 inch. The heat transfer data is presented in the form of a corrected Nusselt number. Based on suggested criteria, much of the data was obtained in the slip flow regime. Therefore, the data is compared with data having comparable flow conditions. The possible application of the heat transfer data to hot wire anemometry is discussed. To this end, the sensitivity of the wires to velocity, density, and total temperature is computed and compared using two different types of correlations.

Nagabushana, K. A.↗
NASA NTRS1982

Flight crew performance when pilot-flying and pilot-not-flying duties are exchanged

This study compares reports from the ASRS database depicting operational anomalies related to flight crew performance when pilot-flying and pilot-not-flying duties were exchanged. A greater number of near midair collisions, takeoff anomalies, and crossing altitude deviations were reported when the Captain was flying. More altitude deviations, near midair collisions during approach, and landing incidents occurred when the First Officer was flying. There were differences in monitoring effectiveness and in the type and distribution of information transfer problems associated with the anomalies. In addition, a number of crew performance factors were noted that were not affected by the exchange of duties. Several of these were deemed important enough to be included as matter of general interest.

Orlady, H. W.↗
NASA NTRS1993

Guidance law development for aeroassisted transfer vehicles using matched asymptotic expansions

This report addresses and clarifies a number of issues related to the Matched Asymptotic Expansion (MAE) analysis of skip trajectories, or any class of problems that give rise to inner layers that are not associated directly with satisfying boundary conditions. The procedure for matching inner and outer solutions, and using the composite solution to satisfy boundary conditions is developed and rigorously followed to obtain a set of algebraic equations for the problem of inclination change with minimum energy loss. A detailed evaluation of the zeroth order guidance algorithm for aeroassisted orbit transfer is performed. It is shown that by exploiting the structure of the MAE solution procedure, the original problem, which requires the solution of a set of 20 implicit algebraic equations, can be reduced to a problem of 6 implicit equations in 6 unknowns. A solution that is near optimal, requires a minimum of computation, and thus can be implemented in real time and on-board the vehicle, has been obtained. Guidance law implementation entails treating the current state as a new initial state and repetitively solving the zeroth order MAE problem to obtain the feedback controls. Finally, a general procedure is developed for constructing a MAE solution up to first order, of the Hamilton-Jacobi-Bellman equation based on the method of characteristics. The development is valid for a class of perturbation problems whose solution exhibits two-time-scale behavior. A regular expansion for problems of this type is shown to be inappropriate since it is not valid over a narrow range of the independent variable. That is, it is not uniformly valid. Of particular interest here is the manner in which matching and boundary conditions are enforced when the expansion is carried out to first order. Two cases are distinguished-one where the left boundary condition coincides with, or lies to the right of, the singular region, and another one where the left boundary condition lies to the left of the singular region. A simple example is used to illustrate the procedure where the obtained solution is uniformly valid to O(Epsilon(exp 2)). The potential application of this procedure to aeroassisted plane change is also described and partially evaluated.

Calise, Anthony J.↗
NASA NTRS1993

Turbulent flow in a channel with transverse rib heat transfer augmentation

Turbulent flow in a 2D channel with repeated rectangular rib roughness was numerically simulated using a low Reynolds number form of the k-epsilon turbulence model. Friction factors and average Stanton numbers were calculated for various pitch to rib height ratios and bulk Reynolds numbers. Comparisons with experiment were generally adequate, with the predictions of friction superior to those for heat transfer. The effect of variable properties for channel flow was investigated, and the results showed a greater effect for friction than for heat transfer. Comparison with experiment yielded no clear conclusions. The turbulence model was also validated for a related problem, that of flow downstream of an abrupt pipe expansion.

Chang, B. H.↗
NASA NTRS1991

Optimal guidance of aero-assisted transfer vehicles based on matched asymptotic expansions

This paper addresses a number of issues related to the matched asymptotic expansions analysis of skip trajectories, or any class of problems that give rise to inner layers that are not associated directly with satisfying boundary conditions. The procedure for matching inner and outer solutions, and using the composite solution to satisfy boundary conditions is rigorously followed in developing a complete algebraic solution to the problem of inclination change with minimum energy loss. Repeated solution of these algebraic equations along the trajectory, treating each current state as an initial state, constitute a feedback guidance algorithm.

Calise, A. J.↗