Axial pressure distribution in the entrance region of packed beds of spheres

The axial pressure distribution near the inlet of a randomly packed bed of spheres at Reynolds numbers between 1036-2749 was measured for inlet geometries of 0, 30, 60, and 90 degrees. For the two smaller inlet geometry angles (0 and 30 degrees), an essentially constant pressure gradient was established within approximately one and one half sphere diameters. Hence it is concluded that the entrance length is of this same order for these cases. This compares well with the only other known previous investigation, under three sphere diameters, for a non-random packed bed in the Forchheimer flow regime. For the larger expansion angles, non-constant pressure gradients were observed.