A heuristic algorithm for drawing of a flow diagram

A flow diagram is a graphical presentation of an energy or chemical system with its components and their interconnections through mass and energy streams. An automatic drawing algorithm of flow diagrams has been developed and presented in this article. It heuristically imitates all the procedures carried out by a designer, starting with his conceptual understanding of the system's topological structure and finishing with graphically representing the system on the paper or screen. The topological structure of the system is given as input in the form of digraph. As a first step, it is transformed to a planar digraph by introducing new vertices representing crossings between the various streams. The near-optimum (smallest) number of crossings is determined heuristically. Then the flow diagram is drawn on the screen using special mechanical engineering symbols for the components of the system. Horizontal and vertical lines represent streams of mass or energy, identified by different colors. Unnecessary expansion of the drawing area is avoided by the application of linear and integer-linear programming algorithms.