Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “electrical resistivity”

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.

At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Anton permselective membrane

Experimental composite membranes were synthesized on a lab scale consisting of a thin layer of anion permselective resin supported by and bonded to a porous physically strong and conductive substrate film. These showed good selectivity and also substantially lower electrical resistivities than the homogenous candidate membranes optimized in the previous contract. A wide range of resin porosities were examined for three candidate membrane systems, CDIL, CP4L, and A3L to identify the formulation giving the best overall redox cell performance. Candidate anion membranes showed large increases in resistivity after a short time of immersion in concentrated FeCl/HCl solution. Largely on the basis of resistance stability the CDIL formulation was selected as prime candidate and about thirty-five membranes (one foot square) were produced for experimental static and dynamic evaluation.

Alexander, S. S.↗
NASA NTRS1980

Solar energy system performance evaluation: Seasonal report for IBM system 1A, Huntsville, Alabama

The operational and thermal performance of the solar energy system, Sims Prototype System 1A, is described. The system was designed by IBM to provide 50 to 60 percent of the space heating and domestic hot water preheating load to a 2,000 square foot floor space single family residence in the Huntsville area. The load design temperature inside the building was to be maintained at 70 degrees fahrenheit with auxiliary energy for heating supplied by an electric heat pump assisted by an electric resistance strip heater. In general the disappointing operation of this system is attributed to the manner in which it was used. The system was designed for residential application and used to satisfy the demands of an office environment. The differences were: (1) inside temperature was not maintained at 70 F as expected; and (2) hot water usage was much lower than expected. The conclusion is that the solar energy system must be designed for the type of application in which it is used. Misapplication usually will have an adverse affect on system performance.

Source record↗
NASA NTRS1980

Development of advanced thermoelectric materials, phase A

Work performed on the chemical system characterized by chrome sulfide, chrome selenide, lanthanum selenide, and lanthanum sulfide is described. Most materials within the chemical systems possess the requisites for attractive thermoelectric materials. The preparation of the alloys is discussed. Graphs show the Seebeck coefficient, electrical resistivity, and thermal conductivity of various materials within the chemical systems. The results of selected doping are included.

Source record↗
NASA NTRS1980

Thermal expansion of composites using Moire interferometry

An experimental technique for precise measurement of the thermal response of fiber-reinforced composite materials uses moire interferometry with fringe multiplication which yield a sensitivity of 833 nm (32.8 mu in.) per fringe. Results from the technique are compared with those obtained from electrical resistance strain gages, and also those predicted from classical lamination theory. Temperature dependent coefficients of thermal expansion for composite materials subjected to thermal cycling in the temperature range of 297 K (75 F) to 422 K (300 F) were determined for four laminate configurations (0, 90, 0/ + or - 45/90 sub s and 0/90/ + or - 45 sub s) of T300/5208 graphite epoxy, and ranged from -0.107 mu epsilon K/1 (-0.059 mu epsilon deg F/-) for the 0 laminate to 32.18 mu epsilon K/1 (17.88 mu epsilon F/1) for the 90 laminate. Moisture was found to greatly influence the thermal response of a quasi-isotropic laminate, resulting in hysteresis and residual compressive strain as the moisture content was reduced. Comparisons between moire and strain gage measurements were inconclusive with both techniques giving consistent but systematically different results. Differences of as much as 29% were observed.

Bowles, D. E.↗
NASA NTRS1980

Solar energy system performance evaluation report for Solaron-Duffield, Duffield, Virginia

The Solaron Duffield Solar Energy System was designed to provide 51 percent of the space heating, and 49 percent of the domestic hot water (DHW) to a two story 1940 square foot area residence using air as the transport medium. The system consists of a 429 square foot collector array, a 265 cubic foot rock thermal storage bin, heat exchangers, an 80 gallon DHW preheat tank, pumps, blowers, controls, air ducting and associated plumbing. A air-to-liquid heat pump coupled with a 1,000gallon water storage tank provides for auxiliary space heating and can also be used for space cooling. A 52 gallon electric DHW tank using the solar preheated water provides domestic hot water to the residence. The solar system, which became operational July 1979, has the following modes of operation: First Stage: (1) collector to storage and DHW; (2)collector to space heating; (3) storage to load. Second Stage: (4) heat pump auxiliary direct; (5) auxiliary heat from heat pump storage. Third Stage: (6) electrical resistance (strip) heat.

Source record↗
NASA NTRS1980

Visualization of the laminar-turbulent transition in the flow over an airfoil using the smoke-wire technique

A flow visualization technique, referred to as the smoke-wire, was used for visualization of the transition of the free shear layer associated with the laminar separation bubble of a NACA 66 sub 3-018 airfoil section at low Reynolds number (50,000-130,000). The smoke-wire technique allows the introduction of fine smoke streaklines into the flow field through the electrical resistive heating of a very fine wire which has been coated with oil and which is located upstream from the leading edge of the airfoil section. Streakline data were collected using both high speed still and motion picture photography.

Batill, S. M.↗
NASA NTRS1980

Refractory thermoelectric materials

The Seebeck coefficient and electrical resistivity of boron-carbon (B-C) and boron-carbon-silicon (B-C-Si)) P-type alloys are reported for temperatures up to 500 C. Using available literature values for the thermal conductivity of B-C alloys, thermoelectric figure-of-merit values of 1.37 x 10 to the -5th and 1.20 x 10 to the -4th/deg C are calculated for 100 and 500 C, respectively. Sulfur-deficient rare earth sesquisulfide N-type alloys exhibit Seebeck coefficients which are relatively insensitive to alloy composition over the composition range investigated but are very sensitive to fabrication parameters.

Elsner, N. B.↗
NASA NTRS1980

Solar heating system at Security State Bank, Starkville, Mississippi

The 312 square feet of Solaron flat plate air collectors provide for 788 square feet of space heating, an estimated 55 percent of the heating load. Solar heated air is distributed to the 96 cubic foot steel cylinder, which contains two inch diameter rocks. An air handler unit moves the air over the collector and into the steel cylinder. Four motorized dampers and two gravity dampers are also part of the system. A Solaron controller which has sensors located at the collectors, rock storage, and at the return air, automatically controls the system. Auxiliary heating energy is provided by electric resistance duct heaters.

Source record↗
NASA NTRS1980

Solar hot water system installed at Day's Lodge, Atlanta, Georgia

The solar energy hot water system installed in the Days Inns of America, Inc., Atlanta, Georgia is described. This system provides for 81 percent of the total hot water demand. There are two separate systems, each serving one building of the lodge (total of 65 suites). The entire system contains only potable city water. The 1024 square feet of Grumman Sunstream Model 332 liquid flat plate collectors and the outside piping drain whenever the collector plates approach freezing or when power is interrupted. Solar heated water from the two above ground cement lined steel tanks (1000 gallon tank) is drawn into the electric Domestic Hot Water (DHW) tanks as hot water is drawn. Electric resistance units in the DHW tanks top off the solar heated water, if needed, to reach thermostat setting.

Source record↗
NASA NTRS1979

Technology development for phosphoric acid fuel cell powerplant (phase 2)

The status of technology for the manufacturing and testing of 1200 sq. cm cell materials, components, and stacks for on-site integrated energy systems is assessed. Topics covered include: (1) preparation of thin layers of silicon carbide; (2) definition and control schemes for volume changes in phosphoric acid fuel cells; (3) preparation of low resin content graphite phenolic resin composites; (4) chemical corrosion of graphite-phenolic resin composites in hot phosphoric acid; (5) analysis of electrical resistance of composite materials for fuel cells; and (6) fuel cell performance and testing.

Christner, L.↗
NASA NTRS1981

Solar space heating installed at Kansas City, Kansas

The solar energy system was constructed with the 48,800 square feet warehouse to heat the warehouse area of about 39,000 square feet while an auxiliary energy system heats the office area of about 9,800 square feet. The building is divided into 20 equal units, and each has its own solar system. The modular design permits the flexibility of combining multiple units to form offices or warehouses of various size floor areas as required by a tenant. Each unit has 20 collectors which are mounted in a single row. The collectors are double glazed flat plate collectors with a gross area of 7,800 sq ft. Air is heated either through the collectors or by the electric resistance duct coils. Extracts from the site files, specifications, drawings, installation, operation and maintenance instructions are presented.

Source record↗
NASA NTRS1981

Cross-linked polyvinyl alcohol and method of making same

A film-forming polyvinyl alcohol polymer is mixed with a polyaldehyde-polysaccharide cross-linking agent having at least two monosaccharide units and a plurality of aldehyde groups per molecule, perferably an average of at least one aldehyde group per monosaccharide units. The cross-linking agent, such as a polydialdehyde starch, is used in an amount of about 2.5 to 20% of the theoretical amount required to cross-link all of the available hydroxyl groups of the polyvinyl alcohol polymer. Reaction between the polymer and cross-linking agent is effected in aqueous acidic solution to produce the cross-linked polymer. The polymer product has low electrical resistivity and other properties rendering it suitable for making separators for alkaline batteries.

Hsu, L. C.↗
NASA NTRS1981

Design and assembly considerations for Redox cells and stacks

Individual redox flow cells are arranged electrically in series and hydraulically in parallel to form a single assembly called a stack. The hardware currently being tested in the laboratory has an active electrode area of either 310 sq cm or 929 sq cm. Four 310 sq cm stacks, each consisting of 39 active cells, were incorporated into a 1.0 kW preprototype system. The physical design of the stack is very critical to the performance and efficiency of the redox storage sytem. This report will discuss the mechanical aspects of the cell and stack design for the current Redox hardware, with regard to sealing the stack internally as well as externally, minimizing shunt currents and minimizing the electrical resistance of the stack.

Stalnaker, D. K.↗
NASA NTRS1981

Hydrogenated amorphous silicon deposited by ion-beam sputtering

Hydrogenated amorphous silicon films 1/2 to 1 micron thick were deposited on metal and glass substrates using ion-beam sputtering techniques. The 800 eV, 2 mA/sq cm beam was a mixture of argon and hydrogen ions. The argon sputtered silicon from a pure (7.6 cm) single crystal wafer, while the hydrogen combined with the sputtered material during the deposition. Hydrogen to argon pressure ratios and substrate temperatures were varied to minimize the defect state density in the amorphous silicon. Characterization was done by electrical resistivity, index of refraction and optical absorption of the films.

Lowe, V. E.↗
NASA NTRS1982

Annular Electrode Improves Solar-Cell Welds

Improved method of electrical-resistance welding of solar-cell inter-connections developed by using an annular welding-electrode shape. Improved weld electrode consists of two coaxial cylinders, outer one with annular cross section and inner one with circular cross section. Possible annular weld-electrode configurations result in better quality welds for interconnecting solar-array elements.

Baraona, C. R.↗
NASA NTRS1981

Study of certain features of the electronic structure of the ternary alloys Ni2(Mn, Fe) and Ni3(Mn, Co)

The changes in electronic structure related to transport processes occurring during the alloying of he alloy Ni3Mn with iron and cobalt, and the ordering of the ternary alloys thus formed are presented. The Hall effect, the absolute thermal emf, the internal saturation induction, the Nernst-Ettingshausen constant, and the electrical resistivity were measured. Results show a decrease in the contribution of hole sections of the Fermi surface to the transport process occurs together with a considerable increase in the contribution of electron sections. In this case, the mobility of 3 dimensional holes decreases and the mobility of 4s electrons increases considerably.

Zhukova, V. M.↗
NASA NTRS1981

Certain physical properties of cobalt and nickel borides

The temperature dependence of the electrical resistivity, the thermal conductivity, and the thermal emf of cobalt and nickel borides were studied. In the case of the nickel borides the magnetic susceptibility and the Hall coefficient were determined at room temperature. The results are discussed with allowance for the current carrier concentration, the effect of various mechanisms of current-carrier scattering and the location of the Fermi level in relation to the 3d band.

Kostetskiy, I. I.↗
NASA NTRS1981

Effects of alloying on aging and hardening processes of steel with 20% nickel

Measurements of hardness, thermal emf, and electrical resistance were used to study the effects of Co, Mo, Ti and Al contents on aging and hardening processes in Fe 20%Ni steel. It is shown that the effects of these alloying elements differ substantially. Anomalies which arise in the temperature dependence of physical properties due to the presence of cobalt and molybdenum are reduced by the inclusion of titanium and aluminum (and vice versa).

Bogachev, I. N.↗