Experimental estimation of the settling velocity and drag coefficient of the hollow cylindrical particles settling in non‐Newtonian fluids in an annular channel

Abstract

The drag coefficient data of particles settling in an annular channel is very much essential for designing different solid–fluid handling equipment, such as the fluidized bed. Experimental settling velocity, wall factor, and drag coefficient data of the hollow‐cylinder particle are presented. Carboxymethyl cellulose solution has been used as the working fluid with a flow index of 0.64 ≤ n ≤ 0.91 and a consistency index of 0.31 ≤ K ≤ 1.81. The experimental results covered a wide diameter ratio range (0.14 ≤ d _eq /L ≤ 0.46), hollow cylinder inner to outer diameter ratio (0.2 ≤ d _i /d _o ≤0.8), and Reynolds number (0.05 ≤ Re ≤ 51 and 0.09 ≤ Re _∞ ≤ 55). d _eq , d _i , and d _o are the equivalent inner and outer diameters of the particle, L is the annular gap, and Re and Re _∞ are the Reynolds numbers in the presence and absence of the wall effect, respectively. The wall factor decreased, and the drag coefficient increased with d _eq /L and d _i /d _o ratios. The above parameters declined with the Reynolds number. The hollow cylinder experienced a lesser wall effect than the spherical particles settling in a non‐annular channel. In some cases, the wall factor of the hollow cylinder is found to be equal to the spherical particles settling in an annular channel. The developed correlations have successfully predicted the drag coefficients of the hollow cylinder.