Effective Application of Energy-Saving Blackbody Coating

Heat Transfer Analysis

There are three heat transfer methods, conduction, radiation, and convection.

Heat conduction or convection both transfer heat by direct contact between hot and cold objects. Unlike thermal radiation, it relies on the surface of the object to emit visible or invisible rays to transfer heat.Heat transfer believes that the energy of radiation is embodied in the form of heat. The amount of heat radiated by the surface of an object per unit time and unit area is called radiation force. The heat radiation force of a black body (an absolutely ideal heat radiating surface) is the largest.

 The ratio of the radiation force of all objects to that of a black body is called the emissivity coefficient, also known as the blackness. No matter the temperature is high or low, all objects radiate energy to the surroundings all the time, and at the same time absorb the energy radiated by the surrounding objects. The overall result is a transfer from high temperature to low temperature.

Energy-saving principle of black body

Traditionally, the kiln insulation was better, and the selection of insulation materials with extremely low thermal conductivity only reduces the rate of heat loss from all interfaces of the kiln to the air, while the other two heat transfer methods can't be changed. Black body material could change the thermal radiation. Spraying blackbody energy-saving paint inside the kiln can effectively enhance the radiation heat transfer inside the kiln, so that the heated object can absorb more heat per unit time, thereby achieving the effect of energy saving.

When the temperature is lower than 800°C, the radiant heat is relatively weak, but when it is higher than 800°C, the radiant heat will increase sharply. Radiation heat transfer can account for 15 times compared with convective heat transfer. According to the measurement of the emissivity coefficient by experts, it is found that the emissivity coefficient of most materials will show a downward trend as the temperature rises. When the temperature reaches 1200°C, the emissivity coefficient of most refractory materials is only about 0.4-0.6. while the black body material can achieve more than 0.9.

A kiln is a kind of equipment that exists to heat a certain substance to a certain temperature. For large-scale continuous kilns, there are situations where the temperature of the heated object is not synchronized with the temperature in the furnace. At this time, it reflects the necessity of high-emissivity materials. For example, the temperature of the inner wall of the kiln is constant at 1200°C. When the object to be heated at 30°C enters the furnace,  When heated in the furnace, it will absorb the heat in the kiln through convection and radiation. After spraying the black body material on the inner wall of the kiln, the radiation coefficient of the inner wall of the kiln is increased, thus the radiant heat in the furnace is enhanced, and the heated object will receive more radiant heat from the inner wall of the kiln, then achieve the effect of energy saving.

Following is a schematic diagram of the radiant heat inside the kiln before and after spraying black body materials

Aust black body energy-saving coating performance index

The coating is not easy to fall off, has a long service life, and will not fall off and pollute the customer's products.

Aust energy-saving coating adopts the self-developed oxide system, which will not cause the expansion coefficient of the material to change greatly due to the oxidation of traditional materials during use, resulting in easy peeling off. In addition, the coating adopts Oster's patented product - nanometer high-strength binder, which has very high bonding strength. Moreover, the spraying thickness of the coating is very thin, only 0.15mm, the coating itself has a very small weight. Therefore, the paint is not easy to peel off from the surface of the substrate, thus there is no possibility of contaminating the customer's product.

The coating will not be oxidized, not easy to fall off, and has a very long service life. Generally, it can reach the same life as the base material. On the premise that there is no problem with the base material, it can guarantee a service life of more than 5 years.

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, the surface is not easy to adhere, which can form a protective layer on the base material, thereby improving the service life of the base material .

The picture above shows the spraying construction site of a large roller kiln.