Novel polymer film heat exchangers for seawater desalination

Multi-effect distillation (MED) plants with co-current flow show moderate process conditions with respect to temperature and pressure differences between consecutive effects. Thus, polymers seem to be best suited as a low-cost and less-corrodible alternative to metal alloys. Furthermore, polymer surfaces are less susceptible to scaling. In order to proof this concept, a falling film plate evaporator with heat transfer surfaces made of polyetheretherketone (PEEK) films was built. One of the main challenges is to assure a sufficient mechanical stability of the polymer film and simultaneously provide a low thermal resistance for heat conduction. Calculations and experiments show that a polymer film thickness of 25 μm, in combination with an appropriate spacer geometry, is sufficient for mechanical stability in MED plants. This low film thickness results in a thermal resistance for heat conduction comparable to 1.5 mm thick stainless steel. In order to demonstrate the applicability of polymer films for heat t...