Falling film evaporator

The fluid distributor has to be designed carefully in order to maintain an even liquid distribution for all tubes along which the solution falls.

The heat transfer coefficient on the evaporating side of the tube is mostly determined by the hydrodynamic flow conditions of the film.

[1][2] A further advantage of the falling film evaporator is the very short residence time of the liquid and the absence of superheating of the same.

Not considering the vapour separator, the residence time inside the tubes is measured in seconds, making it ideal for heat-sensitive products such as milk, fruit juice, pharmaceuticals, and many others.

Due to the intimate contact of the liquid with the heating surface, these evaporators are sensitive to fouling from precipitating solids.

In industries such as heating and air-conditioning this can save significant money due to the high costs of a refrigerant charge.

[3] Horizontal falling film evaporators have a number of potential advantages over their vertical counterparts in the petrochemical industry, such as the ability to use tubes with external enhancements; while internally-enhanced tubes are available for vertical falling film evaporators, external enhancements are typically superior for boiling applications.