Conclusions
The thermal conductivity of granular or slag type deposits can be determined by correlations using two phase medium equations. At room temperature, the effective thermal conductivity appears to be independent of pore size or particle size. The influence of particle size or pore size is significant at higher temperatures when radiative transfer becomes important. Most of the equations for determining the radiative contribution indicate this transfer to be directly proportional to particle size and to the cube of the temperature of the deposit.
The estimates of the thermal conductivity for a partially sintered deposit require the knowledge of extra structural information describing pore size distribution and the connectedness of the particles. This information can be reduced to structural parameters, such as proportions of purely particulate and slag phases and their respective porosity. These parameters can then be used in the hybrid models described for complex structures.
The structural parameters, would also help in providing the anisotropic nature of thermal conductivity of deposits (Ramer, 1996). There is little information available in literature on structural parameters of coal ash deposits and particularly on anisotropic nature of ash deposits. Hence it is proposed to develop the physical structural parameters as function of chemical character of ash and sintering history.
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Gupta, R.P., Wall, T.F., Baxter, L. (2002). The Thermal Conductivity of Ash Deposits. In: Gupta, R.P., Wall, T.F., Baxter, L. (eds) Impact of Mineral Impurities in Solid Fuel Combustion. Springer, Boston, MA. https://doi.org/10.1007/0-306-46920-0_5
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