Experimental Investigation of Drying in a Model Porous Medium: Influence of Thermal Gradients

Abstract

In this study, isothermal and non-isothermal drying experiments with imposed constant temperature gradients have been conducted in a two-dimensional square pore network of borosilicate glass (SiO₂) with interconnected etched channels. In experiments with temperature decreasing from the open surface of the pore network, a travelling stabilized gas-liquid region could be established, while in isothermal experiments with uniform temperature faster breakthrough and an extended two-phase zone were observed. Both findings are in good agreement with pore network simulations. However, numerical underestimation of drying rates (especially in the second period of drying) indicates that liquid films might play a major role in the experimental pore networks, even in the presence of thermal gradients.

Keywords:

• Etched pore networks
• Stabilized drying front
• Temperature gradient

ACKNOWLEDGMENTS

The first author wants to thank the Institute of Micro and Sensor Technique, Otto von Guericke University, for the production of Si-SiO₂ pore networks of very high precision. Part of the experimental equipment was financed by the Graduate School Micro-Macro (DFG GRK1554). The second author was financed by Stiftung Industrieforschung. The cooperation between the institutes was financed by Deutsch-Französische-Hochschule (DFH-UFA).