A TRIDIAGONAL MATRIX MODEL FOR MULTISTAGE FLASH DESALINATION PLANTS

An efficient and reliable technique has been developed to solve the large system of non-linear equations which describe the behaviour of multistage flash (MSF) desalination plants. The new method depends on decomposition of the equations, after linearization, into subsets which are grouped by type rather than by stage, followed by formulation of the enthalpy balance equations into a tridiagonal matrix (TDM) form which is solved by the Thomas algorithm. The computer program developed in this work converged rapidly over a wide range of conditions, showing significant reduction in run times relative to those required by previous stage-by-stage approaches. Both recirculatory and once-through type plants have been simulated for different practical operating situations. The development of the linearized equations is discussed in detail, all physical property correlations are documented and full details of a numerical example given.