Fabrication of polymer film heat transfer elements for energy efficient multi-effect distillation

We make brief remarks about the design, construction and testing of a simple falling saline film vapour compression desalinator - with vertically oriented air mattress-like multi-tube polyolefin film heat transfer elements. Designed for operation with a small ΔT1. From the frictional pressure drop Δpf of the condensing vapour for laminar flow inside a film tube, we relate the film tube diameter, length, U value, temperature and the ratio RT = ΔT1/ΔTf of temperature difference ΔT1 to frictional temperature drop ΔTf.