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Criteria for Local Thermal Equilibrium in Forced Convection in Channel Filled by Porous Medium

Gohardehi, Siavash | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40412 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Nori Brojerdi, Ali
  7. Abstract:
  8. Forced convection in a parallel plate channel filled by porous medium, with walls held at constant heat flux is investigated. A criterion for employing a local Thermal Equilibrium assumption between solid matrix and fluid in a porous channel is developed. Darcy-Brinkman-Forchheimer momentum equation is solved by Homotopy perturbation method. The energy equation for solid and fluid phases employing Local Thermal Non Equilibrium (LTNE) assumption is solved for fully developed and thermally developing forced convection. The analysis leads to an expression for fluid and solid temperatures and also the local Nusselt number. The effect of pertinent parameters such as the Darcy number, the Inertia parameter, the Peclet number, the Biot number and the fluid -to-solid thermal conductivity ratio on fluid velocity and temperatures, solid temperature and the local Nusselt number is investigated. Using fluid and solid temperature difference, criteria for invoking Local Thermal Equilibrium (LTE) in a porous channel as function of Reynolds number, prantel number, solid and fluid thermal conductivity and channel physical properties is developed. It is shown that the Biot number and the fluid/solid thermal conductivity ratio have more influence than Darcy number and Inertia parameter in establishing the validity of Local Thermal Equilibrium assumption. Increasing Biot number and fluid/solid thermal conductivity ratio, causes fluid and solid temperatures to become closer to each other. Increasing particle Reynolds number and reducing particle diameter, magnify LTE condition in porous channel. If a suggested criterion is satisfying, one energy equation for both phases can be used instead of two energy equation for solid and fluid phases
  9. Keywords:
  10. Forced Convection ; Porous Media ; Local Thermal Non-Equilibrium ; Analytical Method ; Thermal Equilibrium Criteria

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