The thermal conductivity decreases as the bulk density increases, but the magnitude of the decrease gradually decreases, so that when the density exceeds a certain range, the thermal conductivity no longer decreases, but instead increases.
At a different temperature, there is a minimum thermal conductivity and a corresponding minimum bulk density, and the bulk density corresponding to the minimum thermal conductivity increases with increasing temperature.
Correct understanding and application of the above rules is of great significance for the application of ceramic fiber. The thermal insulation performance of ceramic fiber is mainly the use of the adiabatic effect of the closed air in the pores of the product. When the specific gravity of the solid fiber is constant, the larger the porosity, the smaller the bulk density.
When the content of slag ball is constant, the effect of bulk density on thermal conductivity is essentially the porosity, pore size and porosity of the thermal conductivity coefficient when the volume density is <96Kg/m3, due to the oscillating convection and radiation heat transfer of the gas in the mixed structure. Reinforcement, the thermal conductivity decreases with the bulk density and increases exponentially.
When the bulk density is >96Kg/m3, as the bulk density increases, the pores distributed in the fiber are closed, the proportion of micropores increases, the air flow in the pores is restricted, and the amount of heat transfer in the fiber decreases (the thermal resistance increases), which in turn leads to The amount of radiant heat transfer between the walls of the holes is also correspondingly reduced, thereby reducing the thermal conductivity.
The bulk density is increased to a certain range of 240-320Kg/m3. The contact point of the solid fiber is increased, so that the fiber itself forms a bridge, the heat transfer amount is increased by the bridge, and secondly, the contact point of the solid fiber is increased, and the damping effect of the pore on the heat transfer is further enhanced. Attenuated, resulting in no further decrease in thermal conductivity and an increasing trend.