isentropicEnthalpy

Isentropic enthalpy of downstream pressure and upstream thermodynamic state (specific entropy)

Information

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

This function calculates the specific enthalpy of R134a for an isentropic pressure change from refState.p to p_downstream (e.g., use setState_phX function for input of refState).

The function can be used for instance to calculate an isentropic efficiency of a compressor or calculate the power consumption (obtained from the isentropic enthalpy) for a given efficiency.

Example:

  Medium.AbsolutePressure p_downstream=10e5;
  Medium.SpecificEnthalpy h_downstream=4.1e5;
  Medium.AbsolutePressure p_upstream=3e5;
  Medium.SpecificEnthalpy h_upstream=4.0e5;

  // Isentropic efficiency of a compressor:
  Real eta_is;

equation

  h_is = isentropicEnthalpy(p_downstream, Medium.setState_phX(p_upstream, h_upstream));

  eta_is = (h_is-h_upstream)/(h_downstream - h_upstream);

Restrictions

The isentropic efficiency function should not be applied in liquid region.

Syntax

h_is = isentropicEnthalpy(p_downstream, refState)

Inputs (2)

p_downstream

Type: AbsolutePressure (Pa)

Description: Downstream pressure

refState

Type: ThermodynamicState

Description: Reference state for entropy

Outputs (1)

h_is

Type: SpecificEnthalpy (J/kg)

Description: Isentropic enthalpy