The relationship between bulk density and thermal conductivity of glass fiber cloth refractory fiber
The refractory fiber can be roughly divided into several elements in the form of heat transfer, the radiation heat transfer of the air hole chamber, the air conduction heat in the air hole chamber and the heat conduction of the solid fiber. The convective heat transfer of the air is ignored here. Bulk density and temperature are interdependent, and the higher the temperature, the lower the bulk density, and the higher the rate of radiation heat transfer. For refractory fiber products, the bulk density is usually below 0.25g/cm', the porosity is above 90%, the gas phase can be regarded as continuous, and the solid phase can be regarded as discontinuous, so the solid thermal conductivity of the fiber is relatively Small.
If it is simply theoretically considered that the bulk density is small, the thermal conductivity will be large, and the bulk density will be small; this is not in line with the actual situation. The number is different, so the porosity per unit volume is also different, so the thermal conductivity will be different. However, the qualitative conclusions can be summarized as follows:
(1) The thermal conductivity of refractory fiber decreases with the increase of density, and the range of decrease gradually decreases, but when the density reaches a certain range, the thermal conductivity no longer decreases and has a tendency to gradually increase.
(2) At different temperatures, there is a minimum thermal conductivity and a corresponding minimum density value. The density corresponding to the minimum thermal conductivity increases with increasing temperature.
(3) With the same density, the thermal conductivity of the pore size is different:
1) The hole diameter is 0.1mm:
At 0C, λ =0.0244W/(m. K) at 100C =0.0314W/(m. K)
2) The hole diameter is 2mm:
At 0C, input = 0.0314W/(m, K) at 100C, λ =0. 0512W/(m . K)
When the aperture is 1mm, when the temperature rises from 0C to 500C, the thermal conductivity value increases by 5.3 times; when the aperture is 5mm, when the temperature rises from 0C to 500C, the thermal conductivity value increases by 11.7 times. Therefore, the larger the pores in the refractory fiber, the smaller the corresponding bulk density and the increase in thermal conductivity.