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Thermal.

Instrument Offers Simultaneous Thermal Analysis

The STA 449-Jupiter is the only thermal analyzer that correlates simultaneously TGA and DSC/DTA techniques. Developed by Martin Schmidt, Netzsch-Geraetebau GmbH, Selb, Bavaria, with the participation of Netzsch Instruments Inc., Paoli, Pa., the Jupiter eliminates errors from sample size changes, inhomogeneity, varying atmospheric conditions, and heating non-uniformity. It can handle temperatures from -120 [degrees] C to 1650 [degrees] C; the latter is 150 [degrees] C hotter than competing instruments.

The Jupiter is vacuum-tight to [10.sup.-4] mbar, which means that it can perform high-temperature TGADSC in high-purity static, dynamic, corrosive, high-vacuum, and reactive-gas atmospheres. This is important for studying catalysis, absorption, desorption, and oxidative behavior. With correct calibration, it can also be used to calculate calorimetric effects, such as transition enthalpies and temperatures or specific heat from heat-flow measurements.

The instrument features an electromagnetically compensated microbalance with true microgram resolution that can handle up to 5-g samples. It also has high stability, including sub-micrometer drift behavior of only one microgram per hour at high temperatures over a 16-hr period.

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Cryogenic Cutter Leaves No Waste

The Cryogenic ZAWCAD, developed by scientists at the DOE's Idaho National Engineering and Environmental Laboratory, Idaho Falls, and ZawTech International Inc., Roswell, Ga., combines cutting and cleaning technologies into one system and adds one enormous advantage--zero-added waste processing.

Originally designed for cutting and decontaminating hazardous materials, the tool uses liquefied atmospheric gas shot out at up to 60,000 psi. Water-jet or chemical treatments leave contaminated by-products to clean up, but the Cryogenic ZAWCAD gases evaporate, flow through a particle filter, and return harmlessly to the atmosphere. It is the only industrial cleaning/cutting system that does not pollute.

Temperature, speed, and aggressiveness are controllable with this technology. During cleaning, it will not pit or scar surfaces the way blasting will. Cryogenic ZAWCAD can also partially remove paint while leaving primer, so that the material is ready for another topcoat without intermediate polishing. It cuts precisely through materials from food or fine meshes to metal.

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Probe Analyzes Thermal Conductivity Nondestructively

For the first time, manufacturers can perform thermal conductivity tests for material quality on a production line. The TC Probe---developed by Nancy Mathis, Mathis Instruments Ltd., Fredericton, Canada--uses a modified hot-wire method to nondestructively measure thermal conductivity of materials having low conductivity values including foams, insulation, pastes, adhesives, polymers, ceramics, glass, silicone, and natural fibers.

The wire heating element has a rectangular backing to provide one-dimensional neat flow without melting solids. The probe calculates thermal conductivity from the rate of temperature rise at the sensor interface. Measurements take from 1 to 120 sec.

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Heating Elements Conserve Energy

A new manufacturing process for molybdenum disilicide has produced dramatic performance and energy-savings in heating elements.

HR Heating Elements, developed by researchers at the Univ. of Cincinnati and Micropyretics Heaters International Inc., Cincinnati, are made with a patented process called micropyretic synthesis. Instead of high-temperature alloy melting, an exothermic chemical reaction melts low-cost powders. Manufacturers use 90% less energy with this method, saving millions of dollars in electricity costs. Micropyretic synthesis also allows HR Heating Elements a higher maximum temperature than conventionally-produced molybdenum disilicide elements.

The molybdenum disilicide produced in this reaction is three times more energy efficient in heating elements.

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Insulation Meets Safety Standards

With Directive 97/69/EC, the European Community established strict regulations for insulation materials that forced manufacturers to seek alternatives to refractory ceramic fibers (RCF). Isofrax Thermal Insulation, developed by a team at Unifrax Corp., Niagra Falls, N.Y., is the only viable European alternative to RCF.

The patented chemistry in Isofrax is 72-77% silica and 19-26% magnesia with a few trace elements, whereas RCF has 50% alumina and 50% silica. RCF is restricted because of its high solubility in lung fluid, which can cause cancer through inhalation. Isofrax's solubility is 20 times lower, making it safe under the European directive.

Though other materials have similar solubility, only Isofrax has a continuous-use temperature limit of 1260 [degrees] C. This is more than 100 [degrees] C better than RCF's limit, and over 200 [degrees] C better than other safe materials' limits.

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Heater Shrinks Combustion Process

A heater the size of a deck of cards weighing less than 0.2 kg is the first application of microscale heat and energy mass transfer to a combustion process.

The MicroHeater, developed by researchers at the DOE's Pacific Northwest National Laboratory, Richland, Wash., is 10 times smaller and lighter than conventional combustors. It is built from 100-to 200-[micro]m-thick sheets of metal chemically etched with microchannels. The sheets are stacked and bonded into a monolithic block. An external energy source provides gaseous fuel that passes through a sintered metal plate acting as a flame holder. Combustion occurs above the plate and products move through microchannels, then mass energy transfer heats water in another array of microchannels.

The technology enables portable heating and heat-pump cooling units in military and civilian markets.

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Heat Engine Produces Acoustic Power

With no moving parts and employing only pipes and conventional heat exchangers, the Acoustic Stirling Heat Engine, from Scott Backhaus, Greg Swift, and Chris Espinoza at the DOE's Los Alamos (N.M.) National Laboratory, converts heat into acoustic power at 30% efficiency.

Gas supporting an acoustic traveling wave propagating through a regenerative heat exchanger undergoes a thermodynamic cycle similar to the ideal Stirling cycle. The net work performed in the cycle appears as an increase in acoustic power as it passes through a regenerative heat exchanger. The acoustic Stirling heat engine is filled with 30 atm of helium that goes through an oval torus, where it is forced to execute the Stirling cycle. A resonator maintains the helium oscillations as an 80-Hz resonance frequency that appears when heat is added. As heat increases so does power.

This engine could provide maintenance-free cryogenic refrigeration for liquefying natural or industrial gases when connected to a pulse-tube refrigerator.

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Condensers Make Power Plants More Efficient

Advanced Direct-Contact Condensers (ADCCs), from a team of researchers at Alstom Energy Systems Inc., Easton, Pa., and the DOE's National Renewable Energy Laboratory, Golden, Colo., improve efficiency in both geothermal and fossil-fuel power plants.

Traditional direct-contact condensing systems cool steam by mixing it with water on perforated plates. ADCCs use geometric surfaces specially designed from computer models for each power plant, to maximize steam/water contact and channel away noncondensable gases.

Geothermal plants generally use traditional direct-contact condensing systems. ADCC tests at The Geysers, the world's largest geothermal complex, increased power production efficiency 5%, increased generation capacity 17%, and cut the chemical cost of emissions abatement in half. ADCCs channel away hydrogen sulfide by design, which saves the energy geothermal plants spend controlling emissions.

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Publication:R & D
Geographic Code:1USA
Date:Sep 1, 1999
Words:1133
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