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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Computer method for identification of boiler transfer functions

An iterative computer method is described for identifying boiler transfer functions using frequency response data. An objective penalized performance measure and a nonlinear minimization technique are used to cause the locus of points generated by a transfer function to resemble the locus of points obtained from frequency response measurements. Different transfer functions can be tried until a satisfactory empirical transfer function to the system is found. To illustrate the method, some examples and some results from a study of a set of data consisting of measurements of the inlet impedance of a single tube forced flow boiler with inserts are given.

Miles, J. H.↗
NASA NTRS1972

Identification of boiler inlet transfer functions and estimation of system parameters

An iterative computer method is described for identifying boiler transfer functions using frequency response data. An objective penalized performance measure and a nonlinear minimization technique are used to cause the locus of points generated by a transfer function to resemble the locus of points obtained from frequency response measurements. Different transfer functions can be tried until a satisfactory empirical transfer function of the system is found. To illustrate the method, some examples and some results from a study of a set of data consisting of measurements of the inlet impedance of a single tube forced flow boiler with inserts are given.

Miles, J. H.↗
NASA NTRS1972

Adhesion and transfer of PTFE to metals studied by auger emission spectroscopy

The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum has been studied using Auger emission spectroscopy. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.

Pepper, S. V.↗
NASA NTRS1972

Adhesion and transfer of polytetrafluorethylene to metals studied by Auger emission spectroscopy

The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum were studied. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron-induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals, such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.

Pepper, S. V.↗
NASA NTRS1971

The measurement of capsule heat transfer gaps using neutron radiography.

The use of neutron radiographs to determine dimensional changes of heat transfer gaps in cylindrical nuclear fueled capsules is described. A method was developed which involves scanning a very fine grained neutron radiograph negative with a recording microdensitometer. The output of the densitometer is recorded on graph paper and the heat transfer gap is plotted as a well-defined optical density change. Calibration of the recording microdensitometer ratio arms permits measurements to be made of the heat transfer optical density change from the microdensitometer trace. Total heat transfer gaps, measured by this method, agree with the physical measurements within plus or minus 0.005 cm over a range of gaps from 0.061 to 0.178 cm.

Thaler, L. A.↗
NASA NTRS1972

Partially ionized gas flow and heat transfer in the separation, reattachment, and redevelopment regions downstream of an abrupt circular channel expansion.

Heat transfer and pressure measurements obtained in the separation, reattachment, and redevelopment regions along a tube and nozzle located downstream of an abrupt channel expansion are presented for a very high enthalpy flow of argon. The ionization energy fraction extended up to 0.6 at the tube inlet just downstream of the arc heater. Reattachment resulted from the growth of an instability in the vortex sheet-like shear layer between the central jet that discharged into the tube and the reverse flow along the wall at the lower Reynolds numbers, as indicated by water flow visualization studies which were found to dynamically model the high-temperature gas flow. A reasonably good prediction of the heat transfer in the reattachment region where the highest heat transfer occurred and in the redevelopment region downstream can be made by using existing laminar boundary layer theory for a partially ionized gas. In the experiments as much as 90 per cent of the inlet energy was lost by heat transfer to the tube and the nozzle wall.

Back, L. H.↗
NASA NTRS1972

Part B: Heat Transfer to Slush Hydrogen

Heat transfer to slush hydrogen was measured at one atmosphere and at triple-point pressure. The data were compared with those for heat transfer to liquid hydrogen, and to classical heat transfer correlations for nucleate boiling. The slush data fit convective heat transfer correlations quite well. In general, the data show that for a given heat flux, the temperature difference between the wall and the bulk liquid is not as highly influenced by pressure as predicted by the core correlation for nucleate boiling.

Sindt, C. F.↗
NASA NTRS1973

Friction, wear, and transfer of carbon and graphite to copper, chromium, and aluminum metal surfaces in vacuum

Sliding friction experiments were conducted with amorphous and fully graphitized carbons sliding on copper and on films of chromium and aluminum on copper. Auger emission spectroscopy analysis was used to monitor carbon transfer to the metal surfaces. Friction and wear were also measured. Metal surfaces were examined both in the clean state and with normal oxides present. Results indicate that different metals have an important effect on friction, wear, and transfer characteristics. With amorphous carbon, the least chemically active metal gave the highest wear and amount of carbon transfer. Both forms of carbon gave lower friction and wear and lower transfer rates when in contact with clean, as opposed to oxide-covered, chromium surfaces. With copper, the reverse was true; cleaning was detrimental.

Buckley, D. H.↗
NASA NTRS1973

Technology transfer to a developing nation, Korea

An experimental project is reported which was undertaken. to determine if selected types of technology developed for the aerospace program during the past decade are relevant to specific industrial problems of a developing nation and to test whether a structured program could facilitate the transfer of relevant technologies. The Korea Institute of Science and Technology and the IIT Research Institute were selected as the active transfer agents to participate in the program. The pilot project was based upon the approach to the transfer of domestic technology developed by the NASA Technology Utilization Division and utilized the extensive data and technical resources available through the Space Agency and its contractors. This pilot project has helped to clarify some aspects of the international technology transfer process and to upgrade Korean technological capabilities.

Stone, C. A.↗
NASA NTRS1972

Prediction and measurement of heat transfer rates for the shock-induced unsteady laminar boundary layer on a flat plate

The unsteady laminar boundary layer induced by the flow-initiating shock wave passing over a flat plate mounted in a shock tube was theoretically and experimentally studied in terms of heat transfer rates to the plate for shock speeds ranging from 1.695 to 7.34 km/sec. The theory presented by Cook and Chapman for the shock-induced unsteady boundary layer on a plate is reviewed with emphasis on unsteady heat transfer. A method of measuring time-dependent heat-transfer rates using thin-film heat-flux gages and an associated data reduction technique are outlined in detail. Particular consideration is given to heat-flux measurement in short-duration ionized shocktube flows. Experimental unsteady plate heat transfer rates obtained in both air and nitrogen using thin-film heat-flux gages generally agree well with theoretical predictions. The experimental results indicate that the theory continues to predict the unsteady boundary layer behavior after the shock wave leaves the trailing edge of the plate even though the theory is strictly applicable only for the time interval in which the shock remains on the plate.

Cook, W. J.↗
NASA NTRS1972

General and specific factors in the intersensory transfer of form.

This study assessed the relative contributions of specific and nonspecific components to intersensory transfer between vision and touch. A paired-associate paradigm was used in which visual metric figures and their tactual analogs served as stimuli, and familiar adjectives were the responses. Positive intersensory transfer, characterized by symmetry across modalities was obtained. The contribution of nonspecific learning to this effect was negligible. Intersensory transfer was found to be less efficient than the empirically determined maximum level of intrasensory transfer possible in this task.

Clark, J. L.↗
NASA NTRS1974

Mass transfer in a 1370 C (2500 F) lithium thermal convection loop

Experimental results from a test to evaluate interstitial element mass transfer effects on T-111, ASTAR 811C, and ASTAR 1211C after 5000 hours in flowing lithium at 1370 C (2500 F) are presented. No gross corrosion effects were observed. However, hafnium and nitrogen transfer to cooler regions within the loop were noted. Oxygen was in general removed from test specimens, but there was no evidence to indicate that it was a major factor in the mass transfer process. Carbon and hydrogen transfer were not detected.

Scheuermann, C. M.↗
NASA NTRS1973

Program for transfer research and impact studies

Research activities conducted under the program for Transfer Research and impact studies are reviewed. Programs include: Tech Brief - Technical Support Package (TSP) Program; transfer documentation; and technology transfer profiles. An analysis of user behavior patterns is made by studying questionnaires filled out by users of the Tech Brief - TSP program. The process of technology transfer is discussed in terms of improving its effectiveness.

Rusnak, J.↗
NASA NTRS1952

Experimental Investigation of Average Heat-Transfer and Friction Coefficients for Air Flowing in Circular Tubes Having Square-Thread-Type Roughness

An investigation of forced-convection heat transfer and associated pressure drops was conducted with air flowing through electrically heated Inconel tubes having various degrees of square-thread-type roughness, an inside diameter of 1/2 inch, and a length of 24 inches. were obtained for tubes having conventional roughness ratios (height of thread/radius of tube) of 0 (smooth tube), 0.016, 0.025, and 0.037 over ranges of bulk Reynolds numbers up to 350,000, average inside-tube-wall temperatures up to 1950deg R, and heat-flux densities up to 115,000 Btu per hour per square foot. Data The experimental data showed that both heat transfer and friction increased with increase in surface roughness, becoming more pronounced with increase in Reynolds number; for a given roughness, both heat transfer and friction were also influenced by the tube wall-to-bulk temperature ratio. Good correlation of the heat-transfer data for all the tubes investigated was obtained by use of a modification of the conventional Nusselt correlation parameters wherein the mass velocity in the Reynolds number was replaced by the product of air density evaluated at the average film temperature and the so-called friction velocity; in addition, the physical properties of air were evaluated at the average film temperature. The isothermal friction data for the rough tubes, when plotted in the conventional manner, resulted in curves similar to those obtained by other investigators; that is, the curve for a given roughness breaks away from the Blasius line (representing turbulent flow in smooth tubes) at some value of Reynolds number, which decreases with increase in surface roughness, and then becomes a horizontal line (friction coefficient independent of Reynolds number). A comparison of the friction data for the rough tubes used herein indicated that the conventional roughness ratio is not an adequate measure of relative roughness for tubes having a square-thread-type element. The present data, as well as those of other investigators, were used to isolate the influence of ratios of thread height to width, thread spacing to width, and the conventional roughness ratio on the friction coefficient. A fair correlation of the friction data was obtained for each tube with heat addition when the friction coefficient and Reynolds number were defined on the basis of film properties; however, the data for each tube retained the curve characteristic of that particular roughness. The friction data for all the rough tubes could be represented by a single line for the complete turbulence region by incorporating a roughness parameter in the film correlation. No correlation was obtained for the region of incomplete turbulence.

Sams, E. W.↗
NASA NTRS1975

Design of experiments for measuring heat-transfer coefficients with a lumped-parameter calorimeter

A theoretical investigation was conducted to determine optimum experimental conditions for using a lumped-parameter calorimeter to measure heat-transfer coefficients and heating rates. A mathematical model of the transient temperature response of the calorimeter was used with the measured temperature response to predict the heat-transfer coefficient and the rate of heating. A sensitivity analysis was used to determine the optimum transient experiment for simultaneously measuring the heat addition during heating and the convective heat-transfer coefficient during heating and cooling of a lumped-parameter calorimeter. Optimum experiments were also designed for measuring the convective heat-transfer coefficient during both heating and cooling and cooling only.

Vanfossen, G. J., Jr.↗
NASA NTRS1975

Surface heat transfer coefficients of pin-finned cylinders

An experimental investigation was conducted to measure heat-transfer coefficients for a 15.24-centimeter-diameter cylinder with pin fins on its surface. Pin diameters of 0.3175 and 0.6350 centimeter with staggered pin spacings of 3 and 4 pin diameters and pin lengths of 5, 7, and 9 pin diameters were tested. Flow was normal to the axis of the cylinder, and local heat-transfer coefficients were measured as a function of angle around the circumference of the cylinder. The average heat-transfer coefficient was also computed. Reynolds number based on pin diameter ranged from 3600 to 27,750. The smallest diameter, closest spacing, and largest pin-length-to-diameter ratio gave the highest average effective heat-transfer coefficients.

Vanfossen, G. J., Jr.↗
NASA NTRS1976

Shock interference heat transfer to tank configurations mated to a straight-wing space shuttle orbiter at Mach number 10.3

Heat transfer was measured on a space shuttle-tank configuration with no mated orbiter in place and with the orbiter in 10 different mated positions. The orbiter-tank combination was tested at angles of attack of 0 deg and 5 deg, at a Mach number of 10.3, and at a free-stream Reynolds number of one million based on the length of the tank. Comparison of interference heat transfer with no-interference heat transfer shows that shock interference can increase the heat transfer to the tank by two orders of magnitude along the ray adjacent to the orbiter and can cause high temperature gradients along the tank skin. The relative axial location of the two mated vehicles determined the location of the sharp peaks of extreme heating as well as their magnitude. The other control variables (the angle of attack, the gap, and the cross-section shape) had significant effects that were not as consistent or as extreme.

Crawford, D. H.↗
NASA NTRS1975

Aminoacyl transfer from an adenylate anhydride to polyribonucleotides

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate to hydroxyl groups of homopolyribonucleotides is studied as a possible chemical model of biochemical aminoacylation of transfer RNA (tRNA). The effect of pH on imidazole-catalyzed transfer of phenylalanyl residues to poly(U) and poly(A) double helix strands, the number of peptide linkages and their lability to base and neutral hydroxylamine, and the nature of adenylate condensation products are investigated. The chemical model entertained exhibits a constraint by not acylating the hydroxyl groups of polyribonucleotides in a double helix. The constraint is consistent with selective biochemical aminoacylation at the tRNA terminus. Interest in imidazole as a model of histidine residue in protoenzymes participating in prebiotic aminoacyl transfer to polyribonucleotides, and in rendering the tRNA a more efficient adaptor, is indicated.

Weber, A. L.↗