This dryer was developed when it was discovered that many aqueous based solutions and suspensions, when nebulized, produce aerosols with larger than desired particle size distributions.  This may be a result of insufficient drying or aging.  Single path diffusion dryers have been used previously in an attempt to dry these aerosols.  However, they have short residence times and in some cases do not adequately remove all of the vehicle from the aerosol stream.  We designed, developed and characterized the Quad-Track Diffusion Dryer that will produce dry, stable aerosols.  The Quad-Track diffusion dryer is designed with four aerosol paths, each one encapsulated in desiccant beads.  This effectively lengthens residence time and the efficiency of the diffusion process is enhanced by increasing the available surface area of the desiccant. 

 Stock # 05-500

9” Barrel - Quad Track Diffusion Dryer

Stock # 05-501

13” Barrel - Quad Track Diffusion Dryer

Comparison tests between the single path and the Quad-Track diffusion dryers were conducted using three types of nebulizers.  Aerosols collected after drying with a single path unit had wet, bimodal distributions.  (MMAD, GSD) of 8.1 µm, 1.2 and 1.6 µm, 1.5 for the HEART™ nebulizer: 4.9 µm, 1.3 and 1.7 µm 1.3 for the PARI LC Plus ™ nebulizer and 3.1 µm, 1.7 and 0.5 µm 1.2 for the LRRI All-Glass Nebulizer.   Aerosols collected after drying with the Quad-Track dryer had unimodal, dry distributions of 1.4 µm, 1.9: 0.7 µm, 2.3 and 1.1 µm, 2.6 for the same nebulizers, respectively, operated  under the same conditions.  Filter samples collected from upstream and downstream  locations relative to the Quad-Track dryer showed there were no particle loses as a result of sedimentation or impaction.