摘要:

Innovative, compact, simple piping supports have been developed for ultra‐high‐temperature nuclear and nonnuclear piping systems that require a large degree of structural reliability. These supports, originally designed for the SP‐100 Ground Engineering System (GES) Nuclear Assembly Test (NAT) power system, can be used in both thin and thick wall piping systems. This paper discusses the design of these piping supports and the supporting thermal and structural analyses.

ISSN:0094-243X    

DOI:10.1063/1.40021

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the thermoelectric properties of several heavily dopedp‐type Si80Ge20alloys prepared by mechanical alloying, a high energy ball milling process. The alloys were formed from elemental silicon, germanium, and boron in the form SiB4and subsequently hot pressed. Measurements of the electrical resistivity, Seebeck coeficient, and thermal diffusivity to 1300 K indicate that these alloys have thermoelectric properties comparable to state‐of‐the‐art SixGe1−xp‐type materials.

ISSN:0094-243X    

DOI:10.1063/1.40022

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This paper presents the results of meausrements of electrical resistivity (&rgr;), Seebeck coefficient (S), thermal conductivity (&Lgr;); as well as Hall carrier concentration (n), and mobility (&mgr;), for hot pressed SiGe 80 a/o Si‐20 a/o Ge (SiGe) thermoelectric materials containing 0.24–3.0 a/o boron.The carrier concentration was varied by annealing and quenching at different high temperatures. Figure‐of‐merit, Z, was found to be 0.60±0.03×10−3K−1over a carrier concentration range from 1.8–3.5×10−20cm−3. This result is very encouraging from a production standpoint, since the dopant concentration is not critical.

ISSN:0094-243X    

DOI:10.1063/1.40024

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Several research groups have tried to reduce the thermal conductivity of thermoelectric materials in order to improve the thermoelectric’s figure‐of‐merit and conversion efficiency (Pisharody and Garvey 1978). Some of these efforts have successfully reduced thermal conductivity, but also have decreased the electrical properties of the thermoelectric. Hence there has been not net gain in figure‐of‐merit. During the past, year of novel material fabrication technique has been applied to the production of silicon germanium thermoelectric decreased the electrical properties of the thermoelectric. Hence there has been material. Ultra‐fine particulates (50 A˚ to 100 A˚) have been hot pressed into boron doped,p‐type, 80/20 silicon germanium. The initial results have been promising. When compared to standard silicon germanium, a reduction in thermal conductivities of up to 40% and an increase in figure‐of‐merit of 10% to 15% has been achieved.

ISSN:0094-243X    

DOI:10.1063/1.40025

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Experimental and theoretical work has been conducted at the Jet Propulsion Laboratory in order to improve the thermoelectric properties ofn‐type SiGe materials. Particular emphasis has been placed upon the understanding of the differences in dopant solid solubilities when multidoping with both Ga and P instead of P alone as in standard SiGe alloys. A set of various experimental techniques for obtaining heavily‐doped hot‐pressed samples coupled with thermodynamic theoretical considerations was used to relate microstructure and composition to electrical and thermal transport properties. A straightforward application of this work resulted in substantial improvements of the thermoelectric figure of merit on several SiGe/GaP, with average Z values close to 1×10−3K−1over the 600–1000°C temperature range. New experiments show that values 10% higher are even possible as the thermal conductivity can be decreased while conserving a high power factor.

ISSN:0094-243X    

DOI:10.1063/1.40138

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Experimental and theoretical efforts directed toward increasing thermoelectric figure of merit values (ZT=&sgr;S2T/&lgr;, where &sgr;=electrical condcutivity, S=Seeback coefficient and &lgr;=thermal conductivity) by a factor of two or three have been encouraging in several respects. An accurate and detailed theoretical model developed for n‐type silicon‐germanium (SiGe) indicates that ZT values several times higher than currently available are expected under certain conditions. These new, high ZT materials are expected to be significantly different from SiGe, but not unreasonably so. Several promising candidate materials have been identified which may meet the conditions required by theory. One such candidate, ruthenium silicide, currently under development at the Jet Propulsion Laboratory, has been estimated to have the potential to exhibit figure of merit values four times higher than conventional SiGe materials. Recent results are summarized.

ISSN:0094-243X    

DOI:10.1063/1.40139

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Electrodes, current collectors, ceramic to metal braze seals, and metallic components exposed to the high ‘‘hot side’’ temperatures and sodium liquid and vapor environment have been tested and evaluated in laboratory cells running for hundreds of hours at 1100–1200 K. Rhodium/tungsten electrodes have been selected as the optimum electrodes based on performance parameters and durability. Current collectors have been evaluated under simulated and actual operating conditions. The microscopic effects of metal migration between electrode and current collector alloys as well as their thermal and electrical properties determined the suitability of current collector and lead materials. Braze seals suitable for long term application to AMTEC devices are being developed.

ISSN:0094-243X    

DOI:10.1063/1.40140

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The AMTEC is a device for the direct conversion of heat to electrical power with no moving parts. Most proposed AMTEC systems have focused on minimizing converter mass for space applications. This paper presents two AMTEC devices that focus on high conversion efficiencies (≳30% at 1100 K) and high volumetric power densities. These high current, low voltage modules could find use in small applications such as EM pumps or large systems requiring many modules to reach the desired power levels. A near term system called the tube bundle system produces a peak power of 426 W/1 and a peak efficiency (at lower power) of 34% at 1100 K hot zone temperature. A more advanced system called a flat plate system produces 2.4 W/1 and 30% efficiency at 1100 K. Further improvements are projected for these devices through the development of optimized porous electrodes or a potassium ion conducting sold electrolyte.

ISSN:0094-243X    

DOI:10.1063/1.40141

出版商:AIP    

年代:1991

数据来源: AIP