Falling Film Evaporator

In falling film evaporators, liquid and vapors flow downwards in parallel flow. The liquid to be concentrated is preheated to boiling temperature if required. An even thin film enters the heating tubes via a distribution device in the head of the evaporator, flows downward at boiling temperature, and is partially evaporated.

The liquid to be evaporated is evenly distributed on the inner surface of a Glass tube. The liquid will flow downwards forming a thin film, from which the boiling/evaporation will take place because of the heat applied by the hot oil . . A number of tubes are built together side by side. At each end the tubes are fixed to tube plates, and finally the tube bundle is enclosed by a shell made either of steel or Glass depending upon the Hot oil pressure. The Hot oil is introduced through the shell. The space between the tubes is thus forming the heating section. The inner side of the glass tubes is called the boiling section. The concentrated liquid and the vapour leave the evaporator at the bottom part, enters the subsequent separator tangentially from where the concentrated liquid is discharged (usually by means of the pump) from the bottom and vapor leave the separator from top.