An evaluation of selected friction factor correlations and results for the pressure drop through random and structured packed beds of uniform spheres

The focus in the paper is on an evaluation of the friction factors as a function of the modified Reynolds number for the pressure drop through randomly and structured packed beds consisting only of uniform sized spheres. In the evaluation of the friction factor for large aspect ratio randomly packed beds it is confirmed that the use of the Ergun correlation should be avoided and that the KTA correlation should be employed to predict the friction factor. The effect of the wall for small aspect ratio randomly packed beds as predicted by the Eisfeld and Schnitzlein correlation is also evaluated and it is suggested that the use of the correlation be restricted to aspects ratios of D/dp > 2. The combination between the Eisfeld and Schnitzlein and KTA correlations should also be investigated. An evaluation is also provided for the friction factor results for selected structured packed beds. A correlation is proposed to predict the friction factor for offset simple cubic, hexagonal close packed, simple cubic and body-centred cubic packed beds. It is recommended that the friction factors for structured packed beds should be studied in more detail to develop a sound understanding of the effect of the packing structure on the pressure drop through a packed bed.