This information is part of the Modelica Standard Library maintained by the Modelica Association.

This function computes an isentropic state transformation:

1. A medium is in a particular state, refState.
2. The enthalpy at another state (h_is) shall be computed under the assumption that the state transformation from refState to h_is is performed with a change of specific entropy ds = 0 and the pressure of state h_is is p_downstream and the composition X upstream and downstream is assumed to be the same.