Dynamic flow rates of granular particles

Flow rates (W) of powder and granules are usually measured by letting the particulate solid pass through a stationary orifice. This is not a physical duplication of the event in, for instance, a rotary tablet machine, where the dies move in relation to the powder bed. An apparatus is described by which dynamic flow rates (i.e. flow into a moving orifice) can be measured. These dynamic flow rates (W₂ g/sec) differ from static flow rates. They are subject to the same dependence on particle diameter, d, as static flow rate, i.e.: W₂ ? W_m = ? k(d ? d_m)^s, where “m” refers to maximum and k and s are constants. They also exhibit the same type dependence on orifice opening (P cm) as static flow rates, i.e.W₂ = qPⁿ, where q and n are constants. The values for _n are 3 – 3.25, which is somewhat higher than for static flow where n = 2.3 – 2.6.