Mass Diffusion in a Hydrophobic Membrane Humidification/Dehumidification Process: the Effects of Membrane Characteristics

Abstract

Humidification and dehumidification are common processes in air conditioning industry. In this study, a new technique‐the hydrophobic membrane based air humidification and dehumidification are investigated. The effects of membrane characteristics on moisture exchange effectiveness of the system are studied. A two‐dimensional transient model which takes into account the combined mechanisms of Knudsen flow and ordinary diffusion in membrane pores is proposed and validated. Four membranes, 2 hydrophobic treated Nylon and 2 PVDF, are used in the test to validate the model. Then the effects of variations of membrane properties on the system performance and membrane to total resistance ratio, are evaluated. A dimensionless Number of Transfer Units (NTU) can be summarized to govern the moisture exchange performance. Following, a correlation has been obtained to reflect the relations between the moisture exchange effectiveness and the Number of Transfer Units.

Keywords:

• Air dehumidification/humidification
• hydrophobic membranes
• mass transfer

Acknowledgements

This Project 50306005 is supported by National Natural Science Foundation of China. The project is also supported by Natural Science Foundation of Guangdong Province under Grant No. 05006557.