A receding interface model for the drying of slurry droplets

A receding interface model of the drying of single drops of slurries of sodium sulfate decahydrate has been developed to describe the drying characteristics of this material and to estimate the drying rates of particulate slurries. The simultaneous heat and mass transfer rate equations have been solved numerically, and the results obtained have been compared with those obtained experimentally by drying single drops suspended on the tip of a glass filament. Single drops of slurries, 1.0 to 1.5 × 10−3 m dia., were suspended on the tip of a flexible glass cantilever inserted in a vertical wind tunnel. A 50μm dia. nickel wire passed through the center of the glass beam and the outer surface was coated with a thin film of copper, thereby forming a thermocouple that measured the temperature of the core of the drop; the deflection of the beam gave the loss in weight during drying. In this way the instantaneous drying rate and drop temperature were determined and compared with those predicted by the receding interface model. In all cases the agreement between the predictions of the model and experimental results was good.