Analogy experiments and Lattice-Boltzmann simulations of forced convection heat transfer of a packed bed under a constant temperature heating condition

Abstract

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 ∼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.