Yazar "Catalbas, Salih Said" seçeneğine göre listele

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    Öğe
    CFD modeling of natural convection in pebble bed geometry with finite volume method
    (Walter De Gruyter Gmbh, 2023) Catalbas, Salih Said; Tiftikci, Ali
    In this study, we used the finite volume method to computationally model natural convective flow in packed bed geometry. Using the OpenFOAM (R) v2112 code, we performed the computational analysis. We successfully meshed the intricate packed bed flow geometry, which consists of several spheres positioned at random. The spheres have sizes of 0.006 and 0.01 m, and the associated Rayleigh numbers are 1.83 x 10(7) and 8.48 x 10(7) respectively. We used the packed bed heights of H/d = 5, 10, and 20 in the simulations. By comparing the results of the OpenFOAM (R) v2112 simulations of the natural convection flow for all self-heating sphere in a packed bed, we demonstrated that the velocity distributions and Nusselt values are in good agreement with the experimental data. Additionally, it was evident from the velocity and temperature distributions in a packed bed core that there was a major temperature rise at nearby low velocity fields and a minor velocity rise in the intermediate and upper elevations. We showed that increasing the height of the pebble-bed core and correspondingly increasing the quantity of spheres inside it makes the flow more difficult and also generates local hot spots. This study is notable for using the finite volume method to evaluate natural convection flow in all self-heating packed beds and for simulating packed bed flow using a significant number of spheres. These two factors contribute to the originality of this work.
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    Öğe
    Investigation of natural convection heat transfer of self-heating packed beds
    (Pergamon-Elsevier Science Ltd, 2023) Tiftikci, Ali; Catalbas, Salih Said; Polat, Eyyub; Ahn, Hyun-Ha; Han, Jeong-Won; Chung, Bum- Jin
    This study investigated heat transfer characteristics of natural convective flow in the packed bed geometry experimentally and numerically. The natural convection experiments for self-heating condition were performed using the copper sulfate electroplating system based on the analogy between heat and mass transfers. Also, the same conditions were simulated with Lattice-Boltzmann Method (LBM) and the results were compared. The spheres diameters were d = 4, 6 and 10 mm and the corresponding Rayleigh numbers were 5.43 x 106, 1.83 x 107 and 8.48 x 107 respectively. The packed bed height to sphere diameter ratios, H/d were 5, 10 and 20. The Nusselt numbers (Nud), velocity and shear stress distributions of both analyses were in good agreement. Both results showed the same order (10-2 m/s) of irregular velocity distributions resulting from the random arrangement of the spheres. In spite of the laminar flow condition, wake and vortex generated by the packed bed geometry increased the turbulent kinetic energies to one-or two-order higher values than those at the entrance. The temperature profiles of flow inside packed bed were approximately uniform for d = 4 mm cases but there were temperature gradients in case of d = 10 mm. This revealed that the use of smaller fuel sphere can prevent from unwanted hot spots inside the packed bed. The Nud values from LBM results and newly developed empirical correlation for natural convective flow in packed bed were consistent.