Uniform representation of the simple flow forms in the case of ideal gases

The lines corresponding to Fanno and Rayleigh flow in an enthalpy-entropy diagram are only uniquely determined if a definite point of state is selected as a reference point. It is pointed out that a generalization providing a better view of the existing conditions could be obtained by making use of a dimensionless representation based on a reference to the critical point of the flow. The basis for an investigation of the feasibility of the considered approach is provided by energy relations which can be employed to study the considered flow forms of ideal gases by means of a uniform procedure. Attention is given to the energy equation with regard to the critical state, the equation system and the significant values, the isentropic flow, the Fanno flow, and the Rayleigh flow.