Yazar "Polat, Eyyub" seçeneğine göre listele

Listeleniyor 1 - 2 / 2
  • [ X ]
    Öğe
    Analogy experiments and Lattice-Boltzmann simulations of forced convection heat transfer of a packed bed under a constant temperature heating condition
    (Elsevier France-Editions Scientifiques Medicales Elsevier, 2026) Tiftikci, Ali; Polat, Eyyub; Moon, Je-Young; Chung, Bum-Jin
    Forced convective heat transfer from a constant temperature packed bed to fluid was investigated varying the sphere diameter and bed height. Mass transfer experiments were performed using the CuSO4-H2SO4 electroplating system on the basis of the analogy between heat and mass transfers. Lattice-Boltzmann simulations were also conducted. Sphere diameters were varied from 0.004 to 0.010 m and flow velocity from 0.01 to 0.56 m/s, which corresponds to Re-dh values of 13-5409. The measured and the computed Nu(dh)'s agreed and lay within the existing correlations, showing more agreement with recent studies. The numerical investigation showed the local temperature and turbulence characteristics within the packed bed. The flow regime transition occurred at Re-dh similar to 400. During both transitional and turbulent flows, a decrease in sphere diameter impaired the heat transfer through the packed bed given the existence of stagnant and recirculation flows through the narrow and complex flow paths. Heat transfer impairment was observed with the increased bed height only during transitional flow, which it was attributable to the preheating effect owing to the constant temperature heating condition. However, this impairment can be restored by the strong flow mixing at the turbulent flow condition. We also developed the forced convective heat transfer correlations.
  • [ X ]
    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.