Effective Thermal Conductivity in a Radial-Flow Packed-Bed Reactor

In this work a theoretical and experimental study of the heat transfer process in a radial flow reactor was carried out under steady- and non-steady-state conditions in order to determine the effective thermal conductivity (ke). One of the mathematical models proposed was a pseudohomogeneous model in which the effective thermal conductivity varies with radial position. The second model studied was a two-phase model with different thermal conductivities for gas and solid. For the pseudohomogeneous model, an analytical solution was obtained using the method of separation of variables and series approximation. In the two-phase model, the gas and solid temperature profiles were obtained by two numerical methods: orthogonal collocation and Runge-Kutta. Several experiments were performed by changing particle diameter, gas flow and temperature input, and reactor size and time-operation condition: steady and nonsteady. Theoretical results were compared with experimental data in order to calculate the effective thermal conductivity. The values of ke agree in general with the literature data. At low Reynolds numbers there is no appreciable difference between a pseudohomogeneous model and a two-phase equation model. Constant thermal properties can be used at Re < 5 with enough accuracy to predict the thermal behavior of a radial-flow reactor.