(430e) The Modified Léveque Limit for Spacer-Filled Channels

Many processes have rates controlled by mass transfer, a key example being ultrafiltration, which is attractive for water purification. In such processes, mass transfer in thin channels can often be enhanced with spacers, which accelerate mass transfer by serving as static mixers. This paper focuses on providing a better explanation of how these spacers function. Static mixing phenomena are studied for spacers in the form of ladders, herringbones, and helices. Using electrochemical mass transfer experiments and computational fluid dynamics simulations, a model has been developed which predicts spacer performance within 8%. The model utilizes the Léveque limit for flat channels to predict the mass transfer coefficient inside spacer-filled channels by breaking the spacer-filled channels into smaller flat channels. Helices provide the fastest mass transfer at the channel walls apparently because of the minimal recirculation zones inside channels filled with them.