Effective Thermal Conductivity of Monolithic and Porous Catalyst Supports by the Moment Technique

Abstract

The axial and radial effective thermal conductivities of a monolithic ceramic catalyst support and of porous alumina pellets were measured using the moment technique. At 180 °C, radial and axial thermal diffusivities were determined as 9.3 x 10 -3 and 11.1 x 10 -3 cm 2 .s -1 , respectively. Having pores being filled with hydrogen, the corresponding thermal conductivity values are 0.43 and 0.52 W.m -1 .K -1 , respectively. Experimental results obtained between 110 and 180 °C indicated a negligibly small dependence of effective thermal conductivities on temperature. A proposed model which included the geometrical parameters of the monolith and the thermal conductivity ratio of the ceramic catalyst support to gas was shown to give excellent agreement with experimental results. Thermal conductivities of alumina pellets having bidisperse pore structures were also measured using this dynamic procedure. Experimental effective thermal conductivity values ranged between 0.043 and 0.120 W.m -1 .K -1 for pellets having porosities between 0.79 and 0.57, respectively.