(70bt) Thermodynamic Analysis of Core-Annular Flow in a Cfb

Granular theory is the analogous theory for discrete particles as the kinetic theory of gases is for gas molecules, that is it treats particles as though they were monatomic gas particles surrounded by vacuum.. Eulerian- Eulerian simulation codes treat both gas and solids as two continuous fully miscible phases. In a circulating fluidized bed granular behavior in the solids phase (stresses, presuure, and viscosity as well as transport and thermodynamic properties) depend on the granular temperature. Tests were conducted in a cold flow model of a circulating fluidized bed gasifier to gather particle velocity data used in calculating granular temperature. Similitude analysis was applied to obtain a system operating with air nominally at atmospheric pressure and cork particles approximately 1mm in diameter. Particle velocity measurements under various operating conditions were obtained with an LDV system. This work extends granular theory to include a thermodynamic analysis of core-annular flow in a CFB with the result being the development of an expression for the Gibbs free energy. Data from LDV measurements in the riser of a CFB indicated the existence of a minimum for the Gibbs free energy. The change in the Gibbs free energy was related to cluster size through the aerodynamic drag force. The result was that clusters on the order of 0.015m in diameter and about 0.24 m in length (1/2 inch by 9 inches) were the most likely which was consistent with visual observation in the clear riser. These clusters were then related to the statistical definition of a cluster presented in earlier work (Breault 2005) and indicated that the observable clusters consist of statistically similar microclusters.