Multiple effect evaporation is a way to reduce the steam requirements for concentration of aqueous solutions. In this case, the train of evaporators is configured in the backward direction, i.e., the steam enters the first effect and the feed enters the final effect. This crossflow arrangement is more thermally efficient than the parallel flow forward configuration.
The inputs are the number of evaporators or effects, the desired final concentration of the feed, the heat transfer coefficients of each effect, the feed temperature, concentration and flow rate, the final and entering steam pressures and the dependence of the boiling point rise and other physical properties on the concentrration of the solution.
The output is a table of the conditions and flows in each evaporator along with the required heat exchange area (HX), assuming equal HX for each effect is desired. The steam economy is also computed indicating the weight of vapor produced per pound of steam consumed.
It is assumed that radiant heat losses are minimal, and all vapor produced is passed to the next effect.