Analysis of multiple effect distillation Part II. Dynamic model Original Research Article

In this study, the MED unit is divided into two sections: heat recovery section and heat rejection section. The heat recovery section consists of a series of effects, while the heat rejection section consists of one effect only (condenser). The MED system contains the evaporators, feed water preheaters and the flashing tanks (boxes). The physical model of effect number ith of MED unit is considered. The physical model can be divided into five compartments such as brine pool, vapor space, condensate tube bundle, feed water preheater and flash tank. The mass, salt and energy balance equations for each previous compartment have been solved dynamically taking into consideration the effect of each one on the other. Dynamic equations in each of the last five compartments mentioned are formulated mathematically for the whole MED system. All effects have identical dynamic equations, except the first evaporator (effect), last evaporator (condenser), and the first flashing tank are formulated mathematically stand-alone. To obtain a proper dynamic model solution, without simplification and complicated approaches, some assumptions have been considered and will be mentioned in the final manuscript. A disturbance technique for the choice parameters has been done to perform the dynamic model program and study the reaction of that disturbance on the behavior of the remaining parameters studied.