Carbolite, a world-leading manufacturer of
furnaces and ovens, has supplied the Fraunhofer Institute for Physical
Measurement Techniques (Fraunhofer IPM) in Freiburg, Germany
with a test rig that comprises two specially customized wire wound horizontal
three-zone tube furnaces. The customized furnaces based on a system that
was developed by the Fraunhofer IPM in 1981 will provide the Institute's
state-of-the-art research teams with a versatile processing system for studying
and improving the thermo-electrical properties of advanced
thermoelectric materials and systems.
The Institute will use the two separately
controlled, rail-mounted three-zone tube furnaces to play a key role in
optimizing compound semiconductors. The systems are designed to maximize
operational flexibility by combining the two, three-zone furnaces to form a
single large multi-zone furnace or separating them to give two differently
heated regions with a gradient of 200°C between the two. Custom built by
Carbolite engineers, the three-zone tube furnaces feature a specially developed
desk and rail system that provides vibration-free movement of the furnaces and is
constructed to support a very long fixed quartz tube through both
furnaces.
Fraunhofer IPM is engaged in research on
new materials, particularly nanocomposites and the Institute's scope of
activity includes materials research, development of thermoelectric modules,
thermoelectric simulation, measuring technology and systems.
Thermoelectrical energy harvesting will increasingly provide a significant
contribution to more efficient use of energy in the future and will be featured
in a wide range of power plants, industrial processes or automobiles.
Fraunhofer IPM has comprehensive
experience in the entire range of thermoelectric technologies which include
studying and developing processes for production of nanoscale thin layer
systems using different coating and epitaxial processes; production and
processing of solid materials; assembly and packaging technologies as well as
thermoelectric measuring technology.
A double horizontal tube furnace was
supplied by Carbolite to maximize the temperature gradient capabilities of the
system. The two three-zone furnaces have different sizes. The larger has
a heated length of 600mm, the smaller 400mm each with an integral recrystalised
alumina work tube. The three zone design of the furnaces uses three
controllers to apply separate control to the central zone and each of the end
zones in each furnace. These end zone controllers with their own
thermocouples compensate for the tendency for tube ends to be cooler and ensure
that the tubes furnaces have a larger uniform zone than can be achieved with
only one control loop.
Each of the two furnaces is equipped to
accept an accessory tube with a maximum outer diameter of 65mm. The customized system
also includes smaller end insulation disks between both furnaces to enable a
more linear temperature gradient from the one end of the furnace to the
other. Power to the furnace's end zones is automatically adjusted to
compensate for heat loss.
To provide a more user-friendly, ergonomic
working environment the furnace systems feature separate controller boxes that
have been specially positioned under the worktable. The furnaces are
specified to operate at a maximum temperature of 1200°C but by using modified
control algorithms they are able to operate between 150°C and 600°C.
Before the systems were delivered to Fraunhofer IPM, Carbolite's engineers made
test measurements between 500°C and 700°C to ensure good uniformity in each
middle zone and a sharp linear gradient in the middle of both furnaces with a
small thermal wall of 15°C in both outer end zones.
For more information on the Carbolite range of ovens
contact Carbolite by visiting
www.carbolite.com or call +44(0)1433
620011 or email
info@carbolite.com for more information.
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