In MFM functions are defined in relation to the processing of flows of mass and energy. MFM is based on a set of six generic flow functions representing different primitive operations performed on either mass or energy flow.
These six functions are shown in the figure below and include: source, transport, storage, sink, balance and barrier. To enable a better representation of chemical process systems, conversion, seperation and distrubution have been included as alternative representations of the barrier for specific instances.
Flow functions in MFM are not isolated. They have to be included in a function structure. In MFM, a function structure represents a set of functions connected by causal relations. A function structure can contain mass and energy flow functions and control functions. There is distinguised between three subtypes: mass flow structures, energy flow structures and control flow structures.
The rules and function states of each flow function can be seen in the table below.
In the figure below, all possible combinations of flow functions are shown. These combinations depend on both the flow function type and influence relation.