Variations of forced convection heat transfer of packed beds according to the heated sphere position and bed height

We investigated the forced convection heat transfer of packed beds of heated spheres. Experiments were performed both for a single heated sphere in unheated packed beds varying its radial and axial positions and for packed beds with all heated spheres varying the height of packed beds from 0.02 m to 0.26 m for Re-d of 31-989. Based on the analogy between heat and mass transfer, mass transfer experiments were performed using the copper electroplating system. For single heated sphere cases, the results agreed well with the existing correlations when the heated sphere was located at the center of packed beds. However, when the position of the sphere was close to the side wall or the bottom of packed bed, the heat transfer increased. For all heated sphere cases, Nu(d) decreased as the ratio of bed height to sphere diameter increased due to the axial dispersion. Based on the results, the heat transfer rate of a single heated sphere in packed bed and those of the all heated packed bed were discussed and heat transfer correlation for the all heated sphere was developed.