257378 Filtered Model for Energy Transport in Gas-Solid Flows
We employ a kinetic-theory1 based two-fluid model to develop a filtered two-fluid model2 for energy transport in gas-solid flows. The filtering procedure gives rise to terms describing the filtered interphase heat transfer and filtered thermal diffusion, which need to be constituted in order to close the filtered transport equations. In this work, the closure for these terms is accomplished by performing fine-grid simulations of the two-fluid model in a two-dimensional periodic domain.3 Filtered thermal diffusion is investigated by imposing a lateral mean gradient in the temperature of each phase. Interphase energy transport is investigated by prescribing a heat source(sink) in the solids(gas) phase, such that the energy content of the mixture is preserved and a local temperature difference is established between the two phases. We find the filtered interphase heat transfer coefficient to be as much as two orders of magnitude smaller than the microscopic interphase heat transfer coefficient. The variation of the filtered transport coefficients with respect to filtered particle volume fraction, and scaling with respect to filter size, is discussed.
1 Gidaspow, D. Multiphase Flow and Fluidization; Academic Press: San Diego, CA 1994.
2Agrawal, K., Loezos, P.N., Syamlal, M., Sundaresan, S. The role of meso-scale structures in rapid gas-solid flows. J. Fluid Mech. 2001, 445, 151-185.
3 Igci, Y., Andrews, A.T. IV, Sundaresan, S., Pannala, S., O'Brien, T. Filtered Two-Fluid Models for Fluidized Gas-Particle Suspensions. AIChE J. 2008, 54, 1431-1448.
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