Compared to circulation evaporators falling film evaporators preferably find application at evaporation of heat-sensitive solutions and solutions which are not susceptible to incrustation. In falling film evaporators the solution flows downwards. In the head of the evaporator the solution is evenly distributed through a proper device over each heating tube and is led on the inner surface of each tube and flows downwards as a thin liquid film. The tubes are heated with steam and the evaporation takes place. The vapour and the solution run downwards in parallel flow. The concentrated solution and the vapour are separated in the vapour chamber in the bottom by means of separators of special design.
Falling film evaporators may be designed single-stage or multi-stage.
Vapour compression finds application as well.