Drag factor for a fixed bed as a function of the Re number with common exponent

• Pressure drop across a granular bed was studied for a variety of shapes.
• The trends in the drag factor show a common pattern.
• The pattern can be described by a power law with a common exponent.
• Beds of granules of similar shapes have close drag factor values.
• Drag factor values possibly relate to the number of channels in a granule.

In this paper, we consider a way to obtain expressions to calculate the pressure drop across fixed beds of granules with a wide variety of shapes, including some shapes developed recently. It is shown that (a) the trends in drag factor versus Reynolds number are similar, and (b) the granule shape types studied form groups with similar shapes and close values of the drag factor. Fitting of experimental data sets for the pressure drop using exponential expressions with a common exponent for the drag factor allows us to obtain general equations for groups of similar granule shapes. In particular, the results indicate the effect of the number of channels in a granule on the drag factor.