Membrane contactor with hydrophobic metallic membranes: 2. Study of operating parameters in membrane evaporation

This paper is the second part of a work concerning a process named membrane evaporation (ME) which is approaching to a sweep gas membrane distillation and based on the concentration of an aqueous solution by its continuous evaporation through a metallic hydrophobic membrane. In the first part we described the basic principles of the process and developed a complete mass and heat transport model. In this second part we present a detailed research of the effects of operating parameters (air velocity, feed temperature, air pressure) and analyzed the interest of using metallic membranes as an electric resistance in order to bring energy directly to membrane pores by Joule effect (electric heat system, EHS). The concept of concentration by ME was validated by using pure water and the theoretical model developed in the previous work was used to understand how the temperature polarization phenomena took place in the process. The model allowed also to determine the effect of the EHS on the temperature profiles and on water evaporation flux.