A Warning message in AFT xStream

Full Message text is:

Maximum system pressure exceeded enthalpy table's maximum pressure of X. Enthalpy is extrapolated for pressures exceeding this value.

 

This warning indicates that the AFT Standard fluid database is being used with the Table Enthalpy model, and that the maximum system pressure exceeded the maximum pressure for the enthalpy data. The Table enthalpy model uses interpolation based on the current pressure to calculate the enthalpy at a given temperature. If the pressure at a point in the system exceeds the maximum pressure data available for the fluid in the AFT Standard fluid database, then the enthalpy must be extrapolated, leading to inaccuracy in the results. Extrapolation far above the maximum temperature will lead to increased inaccuracy, and may cause convergence issues. Consider using an alternate fluid database such as NIST Refprop or Chempak with a higher maximum pressure.