An algorithm is presented for the design and simulation of multieffect evaporators, with forward or backward feed. The mass and enthalpy balances and the heat transfer rate equations posed around each effect are linearized as suggested by Lambert et al. [1], but a new iterative scheme is proposed to ensure convergence and stability when the solution boiling-point rise is considered. Boiling-point rise can reduce the thermal driving force significantly, leading to important errors in the calculation. The algorithm is based on the elimination of an unknown, namely, the product stream flow rate, for simulation in the balances set by assuming a given product concentration and the reduction of the heat transfer rate equations set by elimination of the corresponding equation. The simulation problem is thus converted into a design that can be solved by known numerical methods rendering the required area. If that is not available, the calculation is repeated assuming a new product composition, selected by a criterion presented here, until convergence on the actual area is attained.
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