Abstract
Seawater desalination by multistage flash accounts for more than 90% of the total world desalting capacity. Almost all large size desalination plants (> 5 mgd) are of MSF type. Modelling and simulation of MSF plants are of great importance to designers and operators. Many investigations have been carried for modelling and simulation of MSF desalination plants at steady state mode. Few studies deal with the dynamic behavior of these plants inspite the fact that they are quite sensitive to disturbance. Certain operating variables could suddenly change during the operation causing the plant performance and product quality to be changed significantly. This paper will solve the MSF material and energy balances equations to allow for the dynamic variation of the plants. The orthogonal collocation method will be used to solve these equations.