  This work provides linear control-oriented state space models of gas flow
through standard equipment, such as valves, compressors, manifolds and
non-trivial pipe geometries. After presenting the catalog of components, we
show how to interconnect them: we briefly recall the matrix methodology derived
elsewhere, accompanied by a Matlab example for a gas loop; secondly for the
same example we provide an alternative approach using Matlab's connect
function. All the aforementioned models are suited to model-based MIMO control
design tools as they are in state-space form and they can be physically
parametrized. Conservation of mass is the source of the algebraic constraints
in and is a property subsumed in these new models. This is characterized by
model transfer function properties at frequency zero. Each of the component
models is shown to posses this property.
