The density of clay refractory bricks has a significant influence on its thermal insulation effect. The lower the density, the better the insulation effect is usually. The following is the relationship between density and thermal insulation effect and its principle:

I. Relationship between density and thermal insulation effect

Low density: Low density clay refractory bricks usually have high porosity, and the pores are filled with air or other gases, and the thermal conductivity of gas is much lower than that of solid materials. Therefore, low-density clay bricks can effectively reduce the heat transfer and have better heat insulation effect.

High density: High-density refractory bricks usually have lower porosity, closer contact between solid particles, and easier heat transfer through solid particles, so the heat insulation effect is relatively poor.

II. The role of porosity

Porosity and thermal insulation effect: Porosity is the key factor affecting thermal insulation effect. Clay refractory bricks with high porosity (such as lightweight clay insulation bricks) are filled with a large number of tiny pores, and the gas in these pores can effectively hinder the heat conduction. The thermal conductivity of gas is usually 0.02-0.03 W/(m k), which is much lower than that of solid materials (such as 0.25-0.65 W/(m k) of clay bricks).

Pore structure: the size and distribution of pores will also affect the heat insulation effect. Fine and evenly distributed pores can effectively hinder heat transfer, while large pores or unevenly distributed pores may lead to rapid heat transfer through pores.

III. Specific data on density and thermal insulation effect

Lightweight clay thermal insulation brick: the density is usually 0.6-1.2 g/cm, the porosity is higher (> 45%), the thermal conductivity is lower (0.23-0.65 w/(m k)), and the thermal insulation effect is remarkable.

Ordinary clay refractory brick: the density is 2.0-2.2 g/cm, the porosity is low (about 20%-30%), the thermal conductivity is high (0.4-0.65 w/(m k)), and the thermal insulation effect is relatively poor.

IV. Impact in practical application

Thermal insulation layer: Low-density lightweight clay thermal insulation brick is the first choice in the parts that need thermal insulation effect (such as furnace top, furnace door lining brick, small flue, etc.). They can effectively reduce heat loss and energy consumption.

Structural strength: Although the heat insulation effect of low-density brick is good, its mechanical strength is relatively low. Therefore, it may be necessary to use ordinary clay refractory bricks with slightly higher density in the parts that need to bear large mechanical loads (such as furnace walls).

V. Summary

The density of clay refractory brick has a direct influence on its thermal insulation effect. Low-density brick is suitable for parts with high thermal insulation requirements because of its high porosity and better thermal insulation effect. While the high-density brick has poor thermal insulation effect, but its mechanical strength is higher, so it is suitable for the parts that need to bear large loads. In practical application, it is necessary to choose suitable brick types according to specific working conditions to balance the requirements of thermal insulation effect and mechanical strength.