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Heat transfer analysis
There are three ways of heat transfer, conduction, radiation, and convection
.
Thermal conduction or convection is the direct contact of hot and cold objects to transfer heat, thermal radiation is different, it relies on the surface of the object to emit visible or invisible rays to transfer heat
.
Heat transfer believes that the energy radiated is in the form of heat, reflecting the online coatingol.
com
of coatings.
The heat radiated by the time and area of the surface of the object is called the radiation force
.
The thermal radiation force of a black body, an absolutely ideal surface with thermal radiation, is maximum
.
The ratio of the radiant force of all objects to the radiant force of a black body is called the radiation coefficient, also known as the blackness
.
Regardless of the temperature, all objects are radiating energy to the surroundings all the time, and at the same time, they are always absorbing the energy
radiated by the surrounding objects.
The overall result is the transfer from high temperature to low temperature
.
The principle of energy saving in black bodies
The traditional kiln insulation is better, and the use of insulation materials with extremely low thermal conductivity only reduces the rate
of heat loss to the air at all interfaces of the kiln.
The other two modes
of heat transfer cannot be changed.
Blackbody materials simply change the thermal radiation
.
For the inside of the kiln sprayed blackbody energy-saving coating, it can effectively enhance the radiation heat transfer inside the kiln, so that the heated object absorbs more heat in time, and then achieves the effect
of energy saving.
When it is less than 800 °C, the radiant heat is relatively weak, but after it is greater than 800 °C, the radiant heat will increase
sharply.
Radiative heat transfer accounts for 15 times
more convective heat transfer.
After the measurement of the radiation coefficient by experts, it is found that the radiation coefficient of most materials will decline with the increase of temperature, and when the temperature is 1200 °C, the radiation coefficient of most refractories is only about 0.
4-0.
6
.
The blackbody material can be more than
0.
9.
A kiln is a kind of equipment
that exists to heat a certain substance and reach a certain temperature.
For large continuous kilns, there is a situation where the heated object is not synchronized with the temperature in the furnace, which reflects the need
for high radiation coefficient materials.
For example, the inner wall temperature of the kiln is constant at 1200 °C, and the heated object is at room temperature of about 30 °C when entering the furnace, and when heated in the furnace, it will absorb the heat
in the kiln through convection and radiation.
After spraying the inner wall of the kiln with blackbody material, the radiation coefficient of the inner wall of the kiln is increased, the radiant heat in the furnace is enhanced, and the heated object will receive more radiant heat
from the inner wall of the kiln.
So as to achieve the effect of
energy saving.
The following is a schematic diagram
of the radiant heat inside the kiln before and after spraying the blackbody material.
Performance indicators of Oster blackbody energy-saving coatings
project | index |
Applicable temperature (°C). | 300~1550 |
Bulk density (kg/m3). | 2000 |
Average emissivity in the infrared band | ≥0. |
Coating color | black |
Theoretical coating thickness (mm). | 0. |
Volume solids | ≥75% |
Bond strength (23 times the speed of sound). | ≥5000PSI |
Hardness H | 9 |
Coefficient of linear expansion | 4. |
The coating is not easy to fall off, has a long service life, and will not fall off and contaminate the customer's product Oster energy-saving coating adopts a self-developed oxide system, which will not be oxidized in the use of traditional materials, causing a large change in the expansion coefficient of the material, resulting in easy
shedding.
In addition, the coating adopts Oster's patented product - nano high-strength bond, and the bond strength is very high
.
Moreover, the coating thickness is very thin, only 0.
15mm, and the coating weight is small
.
As a result, the paint does not peel off easily from the surface of the substrate and does not contaminate the customer's
product.
The coating will not be oxidized, not easy to fall off, the service life is also very long, generally can achieve the same life as the base material, under the premise of no problem with the base material, can guarantee more than 5 years of service life
.
The use temperature of the coating itself is very high, the strength and corrosion resistance at high temperature are also very good, and the structure of the coating is dense, and the surface is not easy to adhere, which can form a protective layer on the matrix material, thereby improving the service life
of the matrix material.