Clusters intermittent simulations using dynamic cluster structure-dependent drag model in gas-particles risers. (10th August 2020)

• Record Type: Journal Article
• Authors: Jiang, Xiaoxue; Li, Dan; Wang, Shuyan; Cai, Wenjian; M., Hassan; Lu, Huilin
• Is Part Of: Chemical engineering science. Volume 221(2020)
• Publication Date: 2020-08-10
• Subjects: Gas-solid riser -- Intermittent -- Heterogeneous structures -- Drag coefficient model -- Two-fluid model -- Dominant mechanism; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2020.115643
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: The clusters flow intermittently in the riser. The formation and breaking of heterogeneous structures relate with energy dissipation components of drag and energy dissipation components of collision in the computational cells. Highlights: A computational cell-based dynamic cluster structure-dependent drag model is proposed. The intermittency factor is proposed to reveal the time fraction of cluster existence in the computational cell. A criterion of clusters occurrence is proposed using the minimum energy dissipation rates of drags and collisions. Three different dominant mechanisms of clusters existence are found in the computational cell. Abstract: We present a computational cell-based dynamic cluster structure-dependent (DCSD) drag model which consists of eight balance equations and one extreme value equation for energy dissipation rate with the bivariate extreme value (BEV) method. The criterion of cluster existence is proposed to identify the heterogeneous flow and homogenous flow of gas-particles suspension. The occurrence of clusters is intermittent, and the mean intermittency factor of clusters is from 0.233 to 0.266. The life of the clusters is predicted. The occurrence of heterogeneous structures contribute to the hydrodynamic-dominant mechanism (HD), collision-dominant mechanism (CD) and compromise in competition of collision-hydrodynamic dominant mechanism (CHD). The CHD for particle clustering is a central mechanism, and CD is next to HD. The clusters diameter, volume fraction and velocity are compared with calculations using empirical correlations. The calculated large diameter clusters using empirical correlations are characteristic of flow of collective clusters which are identified using velocity correlation coefficient.