Volume density and porosity of thermal insulation refractory materials
The bulk density and porosity of insulation refractory materials are closely related to their thermal conductivity, heat capacity, and strength, and are important quality indicators of insulation refractory materials.
Volume density refers to the ratio of the mass of a material to its total volume. When the chemical and mineral composition of a material is constant, it represents the density of the material. Generally speaking, the thermal conductivity of thermal insulation refractory materials increases with the increase of bulk density. Therefore, in order to improve the insulation effect, insulation materials with the lowest density are generally selected. However, in fact, the organizational structure of thermal insulation refractory materials, that is, the combination of solid and gas phases, has a significant impact on the thermal conductivity of the material. Special attention should be paid when selecting thermal insulation refractory materials. In the case of the same density, the material with the lowest thermal conductivity is the refractory fiber insulation material with fiber arrangement direction perpendicular to the direction of heat transfer, followed by lightweight refractory powder filled insulation layer, solid phase continuous porous structure products, and fiber insulation products parallel to the direction of heat transfer.
Porosity refers to the ratio of the volume of pores in insulation materials to the total volume of the material, expressed as a percentage. Due to the fact that the insulation function of lightweight insulation refractory materials mainly relies on the insulation effect of air in the pores, the size of the porosity has a decisive impact on the thermal conductivity of the material. It is exactly opposite to bulk density, the higher the porosity of the insulation material, the lower its thermal conductivity. However, as mentioned earlier, the performance of materials depends on their organizational structure.
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