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Influence of porosity, temperature and pressure on thermal conductivity of refractory brick and castable

May 30, 2022

The shape of the pores has an effect on the thermal conductivity of firebricks or castables. The thermal conductivity of refractories with more closed pores is less than that of those with more open pores. If the pores are cylindrical, the pores will increase, and if the pores exist in the firebrick or the interior of the castable is spherical, the thermal conductivity will decrease a lot. And powder and fiber materials affect the thermal conductivity of refractory materials, sintered firebrick will have less impact than castable, thermal conductivity is affected by the heat transfer of pores, if the shape of fiber material is vertical, the impact on the thermal conductivity will be small.


Temperature and gas pressure also affect the thermal conductivity of refractory materials, but the reasons are very complicated. When the gas pressure is large, the thermal conductivity will increase with the temperature. If the pressure is small, the thermal conductivity changes little as the temperature increases.


The size of pores has a certain influence on the relationship between thermal conductivity and temperature and pressure, and the influence of porosity and thermal conductivity-temperature and thermal conductivity-pressure and porosity are different. Under low pressure and low temperature, the influence of pressure on the thermal conductivity of firebricks is relatively weak. Under high temperature greater than 1200 degrees, the influence of pressure on the thermal conductivity of firebricks with high porosity is greater than that of low porosity.


In short, the thermal conductivity of firebrick and castable is closely related to its composition, structure and working conditions, and most of the firebrick or castable is thermodynamic non-equilibrium state, especially in the use of the composition and structure change, will affect the physical properties of firebrick or castable. Especially for refractory castable products, as well as prefabricated products without high temperature sintering, the influence on thermal conductivity is particularly prominent.