Enhancement of drying rate of moist porous media with dielectrophoresis mechanism

Abstract

Drying of moist porous media, such as food or pulp and paper, is an energy-intensive process. Traditional drying technologies have disadvantages, including high energy consumption, thermal degradation of the samples, as well as high capital cost. In this work, a new technology, making use of the Dielectrophoresis (DEP) mechanism, is introduced, to enhance the drying process of a moist porous medium. DEP is a translational motion of neutral matter caused by polarization effects in a non-uniform electric field. In a typical drying process, due to the existence of an electric permittivity gradient between liquid and vapor interfaces, the DEP force can act as an external force to effectively extract the vapor phase away from the product. This in turn enhances the evaporation rate. This article experimentally investigates the influence of the DEP force on the drying of moist hand-sheet paper samples. Specifically, the temperature profile and sample weight are monitored under various applied electric potentials. The non-uniform electric field is generated from a unique electrode design. The experimental results show a significant impact of the DEP force on the temperature profile and drying rate. In addition, the results also show extremely low energy consumption and high energy efficiency associated with the application of the DEP force for drying. With the application of the electric field, up to 10 °C drop in surface temperature and a 33.6% reduction in drying time have been achieved. The experimental work provides a basic understanding of this novel technology that could enhance the drying process in various industry sectors such as forest products, foods, pharmaceuticals, and chemicals.

Keywords:

• Drying
• dielectrophoresis
• diverging electric field
• evaporation
• moist porous media

Additional information

Funding

This study was financially supported by the Center for Advanced Research in Drying (CARD), a US National Science Foundation Industry University Cooperative Research Center. CARD is located at Worcester Polytechnic Institute and the University of Illinois at Urbana-Champaign (co-site).