This paper proposes a numerical analysis of entropy generation during mixed convection inside a porous Poiseuille–Benard channel flow, where the Darcy–Brinkman model is used. Irreversibilities due to heat transfer and viscous dissipation have been derived, and then calculated by numerically solving mass, momentum, and energy conservation equations, by using a control volume finite element method (CVFEM). For a fixed value of the thermal Rayleigh (Ra = 104) and the modified Brinkman (Br* = 10−3) numbers, transient entropy generation exhibits a periodic behavior for the medium porosity ε ≥ 0.2, which is described by the onset of thermoconvective cells inside the porous channel. Highest irreversibility is obtained at ε = 0.5. More details about the effects of the Darcy, the Rayleigh, and the modified Brinkman numbers on entropy generation and heat transfer are discussed and graphically presented.
The paper provides a numerical investigation of the entropy generation analysis due to mixed convection with viscous dissipation effect of a laminar viscous and incompressible fluid, flowing in an inclined channel filled with a saturated porous medium. The Darcy-Brinkman model is employed. The Navier-Stokes and energy equations are solved by classic Boussinesq incompressible approximation. A special attention is given to the study of the influence of the channel inclination angle on the transient and the steady-state entropy generation. The fluctuations of the transient total entropy generation are investigated when the inclination angle is varied from 0 • to 180 • . Moreover, the entropy generation and the Bejan number were studied as a function of the inclination angle of the channel, in the steady state of mixed convection. It was found that the total entropy generation is maximum at inclination angle close to 70 • and minimum at 0 • and 180 • .
This chapter is mainly focused on the minimization of the total entropy generation in a thermodynamic system, which concerns the heating of water when it passes through a saturated porous media. The heating process is assumed by an array of heating tubes immerged on the porous media and perpendicular to the water flow direction. This irreversibility calculation and minimization is carried out in dimensional form in order to have a real idea about the entropy production in the system. Also, the authors focus on several points regarding the rigor of entropy generation calculation, when they pass from dimensional form to dimensionless form.
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