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Refractory fiber in the form of heat transfer can be roughly divided into several elements, the radiation heat transfer of the porous silo, the air inside the porous silo heat conduction and thermal conductivity of the solid fiber, where the convective heat transfer of the air is ignored. Bulk density and temperature have interdependent relationship, the higher the temperature, the lower the bulk density of the case, the ratio of radiation heat transfer increases. For refractory fiber products, bulk density is usually below 0.25g/cm’, the porosity is above 90%, the gas phase can be seen as continuous, the solid phase can be seen as discontinuous, so the solid thermal conductivity of the fiber is relatively small.
If simply from the theory that the bulk density is small, the thermal conductivity is large, the bulk density is large thermal conductivity is small; this is also not in line with the actual situation, such as slag ball content is different, even if the bulk density is the same, the number of fibers per unit volume is different, so that the porosity per unit volume is not the same, so there will be a difference in thermal conductivity. However, the qualitative conclusions can be summarized as follows.
1. The thermal conductivity of refractory fibers decreases with the increase of density, and the decrease decreases gradually, but when the density reaches a certain range, the thermal conductivity no longer decreases and has a tendency to increase gradually.
2. At different temperatures, there exists a minimum thermal conductivity and a corresponding minimum density. The density corresponding to the minimum thermal conductivity increases with increasing temperature.
3. For the same density, the thermal conductivity varies with the size of the pores.
(1) Pore size 0.1mm.
0C into = 0.0244W/(m . K) 100C when λ = 0.0314W / (m. K)
(2) Aperture 2mm.
In at 0C = 0.0314W/(m, K) λ = 0. 0512W/(m . K) at 100C. K)
Pore diameter of 1mm, the temperature rises from 0C to 500C, its thermal conductivity value increases 5.3 times; pore diameter of 5mm, the temperature rises from 0C to 500C, its thermal conductivity value increases 11.7 times. Therefore, the larger the pores in the refractory fiber, the smaller the corresponding bulk density, and the thermal conductivity increases.