scholarly journals Discussion: “Analysis of Solar-Furnace Performance in Mechanical Testing at Extremely High Temperatures” (Leon, G. S., and Shank, M. E., 1960, ASME J. Eng. Power, 82, pp. 325–332)

1960 ◽  
Vol 82 (4) ◽  
pp. 332-332
Author(s):  
Eugene S. Cotton
Keyword(s):  
Mechanical Testing ◽  
High Temperatures ◽  
Solar Furnace ◽  
Furnace Performance

Analysis of Solar-Furnace Performance in Mechanical Testing at Extremely High Temperatures

1960 ◽  
Vol 82 (4) ◽  
pp. 325-332 ◽  
Author(s):  
G. S. Leon ◽  
M. E. Shank
Keyword(s):  
Flat Plate ◽  
Mechanical Testing ◽  
High Temperatures ◽  
Flux Distribution ◽  
Focal Spot ◽  
Mechanical Tests ◽  
Solar Furnace ◽  
Furnace Performance ◽  
Properties Of Materials ◽  
Large Furnace

The use of the solar furnace for investigating properties of materials has received increased attention. However, such work has been limited to determining physical properties of refractory materials. Analyses of performance, related to such work, have been confined to investigations of flux distribution and temperature on flat-plate, hemispherical, and cavity receivers at the focal spot. Heat conduction away from the focal spot usually has not been considered. The present investigation is concerned with the analysis of fluxes and temperatures that can be attained in tensile specimens undergoing mechanical tests. Account is taken of heat loss by conduction and reradiation. It is shown that, (a) attainable temperatures are considerably lower than those reached in flat-plate receivers, (b) with normal low-aperture furnaces (i. e., 60 deg) a large furnace is necessary to reach high temperatures with adequately large specimens, and (c) furnaces best-adapted to mechanical testing would have larger apertures (120 deg) than are now commonly conceived.

High-Temperature Liquid-Fluoride-Salt Closed-Brayton-Cycle Solar Power Towers

2006 ◽  
Vol 129 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Charles W. Forsberg ◽  
Per F. Peterson ◽  
Haihua Zhao
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Solar Power ◽  
Heat Storage ◽  
Solar Furnace ◽  
Working Fluid ◽  
Fluoride Salt ◽  
Power Cycle ◽  
Solar Power Tower ◽  
The Cost

Liquid-fluoride-salt heat transfer fluids are proposed to raise the heat-to-electricity efficiencies of solar power towers to about 50%. The liquid salt would deliver heat from the solar furnace at temperatures between 700°C and 850°C to a closed multireheat Brayton power cycle using nitrogen or helium as the working fluid. During the daytime, hot salt may also be used to heat graphite, which would then be used as a heat storage medium to make night-time operations possible. Graphite is a low-cost high-heat-capacity solid that is chemically compatible with liquid fluoride salts at high temperatures. About half the cost of a solar power tower is associated with the mirrors that focus light on the receiver, and less than one-third is associated with the power cycle and heat storage. Consequently, increasing the efficiency by 20–30% has the potential for major reductions in the cost of electricity. Peak temperatures and efficiencies of current designs of power towers are restricted by (1) the use of liquid nitrate salts that decompose at high temperatures and (2) steam cycles in which corrosion limits peak temperature. The liquid-fluoride-salt technology and closed Brayton power cycles are being developed for high-temperature nuclear reactors. These developments may provide the technology and industrial basis for an advanced solar power tower.

The Influence of the High Temperatures Thermal Shocks on the Microstructure and Harness of Zircaloy-4 alloy

2018 ◽  
Vol 69 (7) ◽  
pp. 1655-1660
Author(s):  
Iustin Alexandru Popa ◽  
Andreea Elena Rosu ◽  
Gabriel Neacsu ◽  
Daniel Constantin Anghel ◽  
Vasile Rizea ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Temperatures ◽  
Oxygen Diffusion ◽  
Rapid Heating ◽  
Thickness Measurement ◽  
Solar Furnace ◽  
Shock Duration ◽  
Hardness Profile ◽  
Thermal Shocks ◽  
Scanning Electron

This study aims at determining the influence of thermal shocks at high temperatures, over the allotropic temperature, on the microstructure, composition and hardness of the Zy-4 sheath. The thermal shocks have been applied at the temperatures between 900 and 1600�C, in the air, lasting 30 and 60 s, through rapid heating in the solar furnace. The treated samples were microstructurally analyzed on the surface and in section by scanning electron microscopy and EDS, thickness measurement of the formed layers, the oxygen and hardness profile determination in section relative to the treated surface. At the microstructural level, the researches have revealed the evolution of the morphology of the oxide layers formed under high temperature thermal shock conditions and the evolution of the microstructure of the metallic mass as the temperature and shock duration increase, correlating this evolution with the oxygen diffusion process and with the evolution of the microhardness. Researches have provided information on the Zy-4 alloy behaviour under accidental conditions.

Quantitative Observations in Dislocation Mechanisms in Gamma TiAl

1994 ◽  
Vol 364 ◽  
Author(s):  
B. Viguier ◽  
M. Cieslar ◽  
K. J. Hemker ◽  
J. L. Martin
Keyword(s):  
Mechanical Testing ◽  
High Temperatures ◽  
Low Temperatures ◽  
Flow Strength ◽  
Statistical Variation ◽  
Different Temperatures ◽  
Defect Densities ◽  
Lattice Friction ◽  
Good Agreement

AbstractQuantitative TEM observations have been made on a series of gamma Ti47Al51Mn2 polycrystals that were deformed at different temperatures. Special attention has been given to determining the statistical variation of defect densities that occur at the different temperatures. The results, which are in good agreement with mechanical testing [J], indicate that three different mechanisms control deformation in this alloy: lattice friction and the formation of faulted dipoles at low temperatures, the pinning of ordinary dislocations at intermediate temperatures, and the bowing and looping of dislocations at high temperatures. The anomalous flow strength of this alloy has been found to be related to the intrinsic pinning of ordinary dislocations. Details of this pinning and subsequent unzipping process, which are the basis for the new local-pinning-unzipping (LPU) models[2-4], are outlined within.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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