The TSI small-scale powder disperser was evaluated to study the effects of total flow rate, capillary flow rate, and particle shape, size, and density on dispersion efficiency and internal losses. Dry powders, including carbon fibers, talc, alumina, and polystyrene microspheres, were used to represent materials with different physical properties. Polystyrene microspheres in the size range of 3-97 mu m were used to study the effects of particle size on performance. Results indicated that, for the same operating conditions, dispersion efficiencies for carbon fibers and polystyrene spheres were higher than talc and alumina. Dispersion efficiency increased as the total flow rate increased and reached a constant value when the low rate was >8 l min(-1). Also the dispersion efficiency decreased as particle sizes increased at a given operating conditions. As for the internal losses in the disperser, particles were deposited primarily at the expansion zone of the venturi tube. Adjustment of the capillary tube location to increase the capillary Row rate did not result in any noticeable change in the efficiency, while poor alignment of the tube resulted in a significant loss as compared with a proper alignment. Along with these data, computer simulations of the flow field and theoretical predictions of the lift force as a result of high flow shear at the venturi throat were successfully used to interpret particle deposition in the TSI small-scale powder disperser.