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Temperature uniformity
is listed in degrees. This is a measurement of the distribution of heat
within the oven work space. This data is the result of actual tests run
in a stabilized empty oven with a minimum of nine thermocouples—eight
thermocouples located at the corners of the work space and one in the
center of the work space. The corner thermocouples are placed 2" to 12"
from the work space edges (based on the size of the equipment) to be representative
of the usable work space. Temperature uniformity will normally improve
as the operating temperature is lowered. Other factors may affect temperature
uniformity adversely.
Blocking the air
flow within the work space will adversely affect the distribution of heated
air and, therefore, the temperature uniformity. Care must be taken to
pick equipment with a recirculated air flow pattern suited to the product
loading.
Temperature uniformity tests have been run with minimal exhaust from the
equipment. Heat input that is required to offset a large exhaust rate
can be compensated for by increasing heat input. However, a large exhaust
rate can have a detrimental effect on temperature uniformity. Hot air
exhausted must be replaced with cooler fresh air. The fresh air is heated
by being recirculated through the heat source. The larger the exhaust
rate, the less the fresh air is mixed before being exhausted. This will
result in non-uniform temperatures in the recirculated air flow.
If tight temperature uniformity is required with a large exhaust rate,
it may be necessary to increase the size of the recirculating blower in
the equipment. Those applications which will require large exhaust rates
should be discussed with our sales engineers. In furnaces, where the heat
transfer is by radiant heat, high temperature fans can be added to the
equipment or the heating elements zoned within the work space to improve
temperature uniformity. These applications should be discussed with a
factory sales engineer.
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