A multiscale interphase heat transfer model for fluidized beds based on the steady-state EMMS approach

Fluidized beds are characterized by heterogeneous structures, which significantly influence the interphase drag and heat transfer. To account for the effects of sub-grid structures on heat transfer in coarse-grid simulations, this study proposes a multiscale heat transfer model based on the steady-state energy-minimization multi-scale (EMMS) approach. This model introduces four structure-dependent internal energy balance equations into the steady-state EMMS model. The heat source and sink terms are included in the internal energy balance equation to maintain a steady-state condition for heat transfer. Solving the model yields the functions of both multiscale drag and heat transfer coefficients. These functions are integrated into coarse-grid simulations under the two-fluid model framework. The simulation results are fairly consistent with the experimental data in terms of both flow and temperature fields, with flow regimes covering bubbling fluidization, fast fluidization and dilute transport.