Longitudinal and lateral thermal dispersion in packed beds. Part II: Comparison between theory and experiment

Abstract

AbstractThe thermal response of a packed bed subject to step changes in fluid temperature was measured in the Peclet number range from 10 to 103. Fluid temperature and particle temperatures were measured independently at six different axial locations in the bed as a function of time. From the temperature breakthrough curves we were able to calculate the spatial separation between the fluid and solid temperature fronts. The measured values were higher by a factor of 2 to 3 than those predicted by traditional heat transfer models. Longitudinal effective thermal conductivities were also computed and compared to theoretical predictions. The new heat transfer model developed in a previous paper is able to account for these differences between experimental results and the predictions of the dispersionconcentric and continuous solid phase models used by previous investigators. Steady‐state experiments were used to measure lateral effective thermal conductivities. A temperature gradient was imposed at the top of the bed perpendicular to the flow direction and its spread was measured at different axial locations in the Peclet number range from 10 to 103. The predicted lateral effective thermal conductivities calculated using mass transfer data to estimate the hydrodynamic dispersion effect were significantly lower than the measured values. This is possibly due to the influence of viscosity and density gradients in the flow field in the packed bed.