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[en] Sarnoff has designed an integrated array of thermophotovoltaic (TPV) cells based on the In(Al)GaAsSb/GaSb materials system. These arrays will be used in a system to generate electrical power from a radioisotope heat source that radiates at temperatures from 700 to 1000 C. Two arrays sandwich the slab heat source and will be connected in series to build voltage. Between the arrays and the heat source is a spectral control filter that transmits above-bandgap radiation and reflects below-bandgap radiation. The goal is to generate 5 mW of electrical power at 3 V from a 700 C radiant source. Sarnoff is a leader in antimonide-based TPV cell development. InGaAsSb cells with a bandgap of 0.53 eV have operated at system conversion efficiencies greater than 17%. The system included a front-surface filter, and a 905 C radiation source. The cells were grown via organo-metallic vapor-phase epitaxy. Sarnoff will bring this experience to bear on the proposed project. The authors first describe array and cell architecture. They then present calculated results showing that about 80 mW of power can be obtained from a 700 C radiator. Using a conservative array design, a 5-V output is possible
[en] The mechanism of generation of a nonstationary large-scale high-intensity cyclonic vortex, which does not require for its origination the rotation of the cavity or the presence of a local heat source at the bottom, is described on the basis of experimental results
[en] Examined is a Thermophotovoltaic (TPV) converter using an advanced quaternary III--V cell with an integral filter coupled to isotope (GPHS) and nuclear reactor heat sources. Results presented indicate the merits of TPV conversion for meeting a wide range of space power requirements. The authors find that TPV offers both a reduction in the cost of building the converter for an electric generator driven by a radioisotope or nuclear reactor, as well as appreciable fuel savings. On the basis of cost, they find that isotope powered TPV systems enjoy considerable advantage over solar arrays or interplanetary exploration missions beyond the asteroid belt. For space reactor power systems the analysis indicates that TPV conversion has a mass advantage over thermoelectrics (T/E) for systems below 50 kWe
[en] A regenerative emf cell operates in a closed cycle to convert heat to electricity. The studies being undertaken at Argonne are concerned with devising regenerative cell systems which can be coupled eventually to a reactor heat source. The principal potential advantages of these systems are the elimination of most of the moving parts that are found in conventional systems, compactness, (a relatively low weight per unit of power output), a long, maintenance-free life, and high temperature operation for those applications where heat rejection at high temperature is required. The applications of such systems might be for remote terrestrial and extraterrestrial power units, energy depots for armed services, and propulsion units for ships and large vehicles.
[en] A process for compacting a granular radioactive material into a sealed solid body for use as a heat source is described. The process is carried out in a hot-cell which is partially evacuated
[en] This letter explains briefly why so-called thermal waves are not truly waves—despite being described mathematically as such—because of their intrinsic diffusive character. This topic should be of interest to those students and teachers dealing with heat transport in the presence of non-stationary harmonic heat sources, photothermal phenomena and techniques, and other related subjects. (letters and comments)
[en] Solidification dynamics are important for determining final microstructure in additively manufactured parts. Recently, researchers have adopted semi-analytical approaches for predicting heat conduction effects at length and time scales not accessible to complex multi-physics numerical models. The present work focuses on improving a semi-analytical heat conduction model for additive manufacturing by designing an adaptive integration technique. The proposed scheme considers material properties, process conditions, and the inherent physical behavior of the transient heat conduction around both stationary and moving heat sources. Both the adaptive integration scheme and a technique for calculating only the points within the melt pools are described in detail. The full algorithm is then implemented and compared against a simple Riemann sum integration scheme for a variety of cases that highlight process and material variations relevant to additive manufacturing. Lastly, the new scheme is shown to have significant improvements in computational efficiency, solution accuracy, and usability.
[en] An electrical generator having an isotopic heat capsule including a radioactive fuel rod as a primary heat source and thermoelectric modules as converters is described. The biological shield for the capsule is suspended from spiders at each end each consisting of pretensioned rods and defining planes at right angles to each other. The modules are mounted in cups of transition members of a heat rejection fin assembly whose fins extend from both sides of the transition member for effective cooling
[en] Mankind will continue to explore the stars through the use of unmanned space craft until the technology and costs are compatible with sending travelers to the outer planets of our solar system and beyond. Unmanned probes of the present and future will be necessary to develop the necessary technologies and obtain information that will make this travel possible. Because of the significant costs incurred, the use of modern manufacturing technologies must be used to lower the investment needed even when shared by international partnerships. For over the last 30 years, radioisotopes have provided the heat from which electrical power is extracted. Electric power for future spacecraft will be provided by either Radioisotope Thermoelectric Generators (RTG), Radioisotopic Thermophotovoltaic systems (RTPV), radioisotope Stirling systems, or a combination of these. All of these systems will be thermally driven by General Purpose Heat Source (GPHS) fueled clad in some configuration. The GPHS clad contains a 238PuO2 pellet encapsulated in an iridium alloy container. Historically, the fabrication of the iridium alloy shells has been performed at EG ampersand G Mound and Oak Ridge National Laboratory (ORNL), and girth welding at Westinghouse Savannah River Corporation (WSRC) and Los Alamos National Laboratory (LANL). This paper will describe the use of laser processing for welding, drilling, cutting, and machining with other manufacturing methods to reduce the costs of producing GPHS fueled clad components and complacute eted assemblies. Incorporation of new quality technologies will compliment these manufacturing methods to reduce cost. copyright 1996 American Institute of Physics