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Computational Simulation of Cooling of Porously Covered Surfaces, Using a Navier-stokes and Lattice Boltzmann Solver

Salimi, Mohammad Reza | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47917 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Tayyebi Rahni, Mohammad; Jam, Freydoon
  7. Abstract:
  8. Considering the wide range of applications of porous media for heat transfer enhancement in various components of industrial machineries, including solar collectors, air dryers, compact heat exchangers, electronic microchips, investigation of heat transfer characteristics in porous media has been a major concern for many researchers. On the other hand, precise understanding of the physics of porous media-flow interaction has been an open research topic for a long time. The present research however, has aimed at developing a computational method to simulate the interaction between fluid flow and porous media to investigate heat transfer from prously covered surfaces. Pore scale modeling of porous media accompanies a wide range of time and length scales, inside and outside of the porous media and thus, the present problem can be viewed as a multi-scale one. Due to their accuracy and efficiency, hybrid methods are commonly used for such problems. Hence, in this work, lattice Boltzmann (LB) and Navier-Stokes based CFD approaches were combined as a hybrid method. The flow and thermal fields inside the porous media were analyzed using LBM, whereas the outside was simulated by finite volume method (FVM), solving the Navier-Stokes equations. The major novelty of the present research is developing new lifting relations to compute particle distribution functions in LBM from macroscopic flow variables. In our new hybrid method, a compressible version of SIMPLE algorithm was used in solution of the Navier-Stokes equations, while multiple relaxation time (MRT) version of collision operator was used in LBM. The present technique has improved the stability of the existing hybrid methods in such way to also handle turbulent flow problems. The validity of this method was assured in both laminar and turbulent flows in two- and three-dimensions. Then, the flow and heat transfer inside and outside the porous layers were analyzed in detail. Moreover, to have a better understanding of the heat transfer characteristics inside the porous media, thermodynamics second law analysis was performed, using viscous and thermal entropy generation numbers. The related results were used to indicate local thermal non-equilibrium and hydrodynamic losses, which can be used for optimization purposes in future works. Additionally, the results indicate the accuracy of the new hybrid technique for analyzing meso-macro scale problems such as porous media-flow interaction
  9. Keywords:
  10. Heat Transfer ; Porous Media ; Pore Scale Simulation of Fluid Flow ; Pore-Scale Model ; Finite Volume Method-Lattice Boltzmann Method ; Multiple Relaxation Time (MRT)

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