Besides the description of the MESH equations for each theoretical stage, a mDWC can be described by a thermodynamic consistent flowsheet. Therefore sections of the mDWC are represented by fully thermally coupled simple columns without reboiler and condenser. Each of these columns has an ingoing vapor and outgoing liquid stream at the bottom of the column and an outgoing vapor and ingoing liquid stream at the top of the column. The feed stage corresponds to a split stage above or beneath a dividing wall. The columns representing sections of the mDWC are interconnected by vapor and liquid streams. The product streams are located at the top, or bottom of the representing columns. Such a flowsheet is also called Petlyuk sequence (see for example . An example for the separation of four components is shown in Figure for the mDWC introduced in Figure . The column sections are shown by dashed lines in Figure . The corresponding columns in the thermodynamic consistent flowsheet are shown in Figure . The column sections C i,j are numbered from right to left and from top to bottom. We skip the second index j if there is only one.