2. Analysis of factors affecting heat insulation performance of lightweight refractories
Because of the complex structure and harsh working environment of lightweight refractories, there are many factors that affect their thermal insulation performance. Moreover, various factors influence and relate to each other, making it difficult to conduct analysis and research accurately. However, among the many influencing factors, the composition and structure of the material, the porosity and the characteristics of the pores, bulk density, and temperature are the main factors.
(1) Composition and structure of materials
The chemical mineral composition and crystalline structure of the material are the primary factors affecting the thermal conductivity of lightweight refractories. Generally speaking, the more complex the crystal structure of a lightweight refractory material, the smaller its thermal conductivity. The solid phase of the material can be simply divided into a crystalline phase and a glass phase. When atoms (ions) transfer kinetic energy from atoms (ions) with higher kinetic energy to other atoms (ions) with lower kinetic energy through vibration and mutual collision, as the atoms (ions) in the glass phase are arranged in disorder, the resistance encountered in glass phase is higher than the orderly arrangement of crystalline phases. Therefore, the glass phase has a lower thermal conductivity than the crystalline phase. However, when the temperature rises to a certain level, the viscosity of the glass phase decreases, the movement resistance of atoms (ions) decreases, and the thermal conductivity of the glass phase increases. The crystalline phase is the opposite. When the temperature rises, the kinetic energy of the atoms (ions) increases, and the vibration increases, resulting in a shortening of the free path and a decrease in the thermal conductivity. In the internal structure of lightweight refractory materials, the solid phase is separated by many pores of different sizes, which cannot form a continuous solid phase transfer of heat. Gas phase heat transfer replaces most of the solid phase heat transfer, so the thermal conductivity is very low.
Next issue we will continue to introduce factors affecting heat insulation of lightweight refractories.
