Thermos-Physical Properties of Insulating Refractory Materials

1
Thermos-Physical Properties of Insulating
Refractory Materials
You can witness the use of refractory materials
in multiple fields like iron and steel,
ceramics, petrochemical, electric power, etc.
Refractory bricks are also a kind of refractory
material.
These are necessary as basic materials to ensure
the functioning of several industries.
Refractory materials are inorganic, nonmetallic
materials that have a high refractory degree.
They include products made by specific processes
for specific purposes and natural ores. These
materials come with various thermal insulating
properties. The bulk density of refractory
materials is an important physical property
expressed using the units - kilograms per cubic
meter or pounds per cubic foot.
2
Thermos-Physical Properties of Insulating
Refractory Materials The efficiency of
insulating refractory materials is dependent on
the thermal insulating properties of these
materials. Some of the thermostatically
properties of refractory materials are as
follows 1) Thermal Shock Resistance A
refractory material suffers from frequent
temperature changes. These changes lead to
thermal stresses in the refractory materials,
which, in turn, cause the expansion and
contraction of the material. Two commonly used
tests that measure thermal shock resistance
include the prism spalling test and the test that
checks loss of strength. The prism spalling test
is about cycling samples of refractory materials
from 2200 degrees Fahrenheit for around 10
minutes, then put to water for around 2 minutes,
followed by air for 7 to 8 minutes. This cycle
continues till the specimens break, or there
have been 40 cycles. The more the number of these
cycles, the higher the thermal shock resistance
of the refractory insulation materials will
be. In the test that checks the loss of strength,
a sample of the insulating refractory material
is brought from room temperature to 2200 degrees
Fahrenheit five times. After that, the Modulus
Of Rupture ( MOR) is done on cycled, and uncycled
samples, and then the strength loss is
calculated in percentage using the MOR values of
the cycled and uncycled specimens. It is done 5
times with different samples of the refractory
material, and the corresponding loss of strength
3

• percentage is calculated. The thermal shock
  resistance is good if the strength loss is
  minimal.
• Reversible Thermal Expansion
• A refractory material usually expands when it is
  heated and suffers from contraction when cooled.
  Data sheets show a thermal expansion curve graph,
  which represents the expansion rates of the
  refractory material at different temperatures.
  The expansion rates are different for various
  refractory materials. Some refractory materials
  may also become larger than their usual size when
  they are cooled. The reheat tests will
  demonstrate the linear and volume change.
• Thermal Conductivity
• Thermal conductivity measures the amount of heat
  flowing from the hotter side to the colder face
  of any refractory lining. This flow of heat
  depends on the wall thickness and the refractory
  material's conductivity value. The thicker the
  wall, the less the heat flow will be. The
  thermal conductivity is also directly related to
  the drop in temperature from the hot side to the
  cold side, the time and the wall's area.
• There may be various ways to measure thermal
  conductivity you must compare the results of
  the same tests to check for the thermal
  insulating properties.
• Final words
• The thermal insulating properties play a key role
  with respect to the refractory materials. In
  this article, we have discussed three such
  properties.
• Source Link https//www.problogs.in/thermos-physi
  cal-properties-of-insulating/