F. Dierich, P.A. Nikrityuk, S. Ananiev
Chemical Engineering Science, Volume 66, Issue 22, November 2011
The main aim of this work is to study the behavior of particulate flows taking into account the interfacial heat transfer on the particle surface including the phase change phenomena. Two flow configurations of increasing complexity are studied with the aim of unraveling fundamental properties of heat transfer in two-phase flows. The first configuration corresponds to the fluid flow past a single cylindrical ice particle melted in the water. The focus is on the influence of the Reynolds number on the melting time of a single particle and comparison of numerical data against Nu-based models. The second configuration refers to ice particles moving up in the water due to the gravity force in a two-dimensional channel. Here, the focus is on the study of particle dynamics in the presence of neighboring particles, including the influence of the viscous torque on the particle trajectories and finally on the melting time compared to the case of a single particle. An implicit fictitious boundary method (FBM) over a fixed Cartesian grid is extended to model the heat transfer and the phase change in particulate flows in two dimensions. The hydrodynamic forces acting on the particles are calculated directly through the surface integrals without the use of any semi-empirical correlations. The particle collisions are modeled directly using the hard sphere approach, taking into account the inelastic collisions. The interface velocity of the melting (solid–liquid) was calculated by means of the Stefan condition for each particle. To illustrate the impact of particle rotation caused by the viscous torques on the particle trajectory, a set of simulations was performed with and without viscous torque effect. A comparative analysis of the results showed that when the viscous moment is taken into account, the particle melting time is reduced significantly. Additionally, based on an analysis of the time history of the volume-averaged velocity in the entire domain, three regimes were found. In particular, the first regime is characterized by the acceleration of particles due to the gravity force, the second is the transitional regime and the last is the passive regime, where the melted particles follow the flow induced by particles in the past. During the last regime the particles do not have any influence on the fluid flow. The influence of the initial configuration of particles on the flow pattern and regimes is discussed.
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