A falling film evaporator is an industrial device to concentrate solutions, especially with heat sensitive components. The eveporator is a special type of heat exchanger.

 

In general evaporation takes place inside vertical tubes, but there are also applications where the process fluid evaporates on the outside of horizontal or vertical tubes. In all cases, the process fluid to be evaporated flows downwards by gravity as a continuous film. The fluid will create a film along the tube walls, progressing downwards (falling) - hence the name. The fluid distributor has to be designed carefully in order to maintain an even liquid distribution for all tubes along which the solution falls.

 

In the majority of applications the heating medium is placed on the outside of the tubes. High heat transfer coefficients are required in order to achieve equally balanced heat transfer resistances. Therefore, condensing steam is commonly used as a heating medium.

 

 

These are Tubular Evaporators having heating media on the shell side and the process liquid in the tubes.

In case of Rising film evaporator, the liquid feed enters the evaporator through bottom header and moves upward through tubes. It receives heat from the heating media on shell side. The vapour is generated in the tubes which starts rising up pulling the liquid in the film form. The vapour and liquid enters the vapour-liquid separator where they are separated. Vapour moves upward to vapour nozzle while the concentrate moves down to concentrate nozzle.

In case of Falling film evaporator the liquid feed enters at top, gets distributed uniformly in tube bundle by a distributor. The feed flows downwards along the tube walls as a film. It receives the heat from the heating media on the shell side. Vapour is formed and the concentrate flows downward along with the vapour. The entrained liquid in the vapour is separated in the separator and flows upward to vapour nozzle.