Falling film break-up and thermal performance of thin polymer film heat exchangers

•Falling film wettability is analyzed and film break-up is predicted.•Flat surfaces are studied as well as polymer film and spacer combinations.•Heat transfer with and without phase change is conducted.•Correlations are proposed describing the spacer induced heat transfer enhancement.

Polymers as alternate construction materials in apparatus design feature special advantages as column internals or in heat transfer operation when handling corrosive media (resistance to corrosion and fouling, costs). However, high overall heat transfer coefficients can only be realized when applying thin polymer films (25 μm) in combination with a spacer grid. The hydrodynamic characterization of such heat exchangers is necessary in respect to its specific design criteria as well as general understanding of falling film heat transfer enhancement. The falling film break-up propensity of flat polymer surfaces and polymer-spacer combination is investigated and heat transfer with and without phase change is studied and modeled as well. New correlations are proposed for the heat transfer enhancement induced by the spacer grid of the Polymer Film Heat Exchanger (PFHX).