Cotton dust sampling efficiency of the vertical elutriator.

A theoretical model of the vertical elutriator air sampler based upon the phenomenon of flow separation at the inlet was developed at SRRC. The model's equations were simulated by a computer program (VELUT). The model was calibrated by comparison of available experimental results to isokinetic sampling efficiencies calculated by the model. The calibrated model was used to predict integral efficiencies for a systematic assortment of size distributions of cotton dust. Rather than cutting off cleanly at 15 micrometers, the computer model exhibited a 50% differential efficiency at approximately 20 micrometers. Furthermore, the model predicted substantial non-zero collection efficiencies in the aerodynamic size range of individual cotton fibers. Program VELUT represents an objective method whereby the isokinetic sampling efficiency of the vertical elutriator can be explicitly calculated for any known or postulated ambient dust distribution presented to the sampler at its inlet plane.