Falling film evaporators

Falling film evaporator is the simplest & most commonly used type of film evaporator which is applicable in handing low viscous type of liquid. It is a heat transfer mechanism controlled by conduction and convection across the tubes. In falling film evaporator liquid evenly distributed over top tube sheet using uniquely designed distributor and tube inserts.
Liquid flows under gravitational force as a thin film on the inside of vertical tubes which is heated by steam from outside and resulting vapor normally flows co-currently with the liquid in the center of the tubes. Concentrated liquid & vapor then passes through separator to separator vapors from residual liquid which is then pass on to the condenser.

Forced circulation evaporators

Forced circulation evaporator is used for the concentration of high viscous material and products with higher solids. It consists of a circulating pump, a separating space, an evaporator body with a vapor outlet at the top, a deflector plate, an outlet for discharge of thick liquor & an external heating surface. Liquid is circulated through tube by centrifugal pump where it is superheated & flashes into a mixture of vapor & liquid and two phase mixture impinges on a deflector plate in the separating space &vapors are removed from top and liquid is returned to centrifugal pump.