The Liquid to be concentrated is preheated to boiling temperatures; even thin films enters the heating tube via distributors in the head of the evaporator, flow downward at boiling temperature and is partially evaporated. Spreading of liquid to each tube and forming the thin film across area of the tube is the principle of falling film evaporator. It can be used for processing liquors, which are sensitive, have a high rate of specific heat transfer, for low fouling, low viscous fluid & for non crystalline solutions. Falling Film Evaporation is a process controlled by two different heat transfer processes, i.e. Conduction and/or Convection across the film.