ICapeThermoPropertyRoutineCalcAndGetLnPhi Method

[DispIdAttribute(1)]
void CalcAndGetLnPhi(
	string phaseLabel,
	double temperature,
	double pressure,
	Object moleNumbers,
	int fFlags,
	out Object lnPhi,
	out Object lnPhiDT,
	out Object lnPhiDP,
	out Object lnPhiDn
)

<DispIdAttribute(1)>
Sub CalcAndGetLnPhi ( 
	phaseLabel As String,
	temperature As Double,
	pressure As Double,
	moleNumbers As Object,
	fFlags As Integer,
	<OutAttribute> ByRef lnPhi As Object,
	<OutAttribute> ByRef lnPhiDT As Object,
	<OutAttribute> ByRef lnPhiDP As Object,
	<OutAttribute> ByRef lnPhiDn As Object
)

Parameters

phaseLabel  String

Phase label of the Phase for which the properties are to be calculated. The Phase label must be one of the strings returned by the GetPhaseList method on the ICapeThermoPhases interface.

temperature  Double

The temperature (K) for the calculation.

pressure  Double

The pressure (Pa) for the calculation.

moleNumbers  Object

Number of moles of each Compound in the mixture.

fFlags  Int32

Code indicating whether natural logarithm of the fugacity coefficients and/or derivatives should be calculated (see notes).

lnPhi  Object

Natural logarithm of the fugacity coefficients (if requested).

lnPhiDT  Object

Derivatives of natural logarithm of the fugacity coefficients w.r.t. temperature (if requested).

lnPhiDP  Object

Derivatives of natural logarithm of the fugacity coefficients w.r.t. pressure (if requested).

lnPhiDn  Object

Derivatives of natural logarithm of the fugacity coefficients w.r.t. mole numbers (if requested).

This method is provided to allow the natural logarithm of the fugacity coefficient, which is the most commonly used thermodynamic property, to be calculated and returned in a highly efficient manner.

The temperature, pressure and composition (mole numbers) for the calculation are specified by the arguments and are not obtained from the Material Object by a separate request. Likewise, any quantities calculated are returned through the arguments and are not stored in the Material Object. The state of the Material Object is not affected by calling this method. It should be noted however, that prior to calling CalcAndGetLnPhi a valid Material Object must have been defined by calling the SetMaterial method on the ICapeThermoMaterialContext interface of the component that implements the ICapeThermoPropertyRoutine interface. The compounds in the Material Object must have been identified and the number of values supplied in the moleNumbers argument must be equal to the number of Compounds in the Material Object.

The fugacity coefficient information is returned as the natural logarithm of the fugacity coefficient. This is because thermodynamic models naturally provide the natural logarithm of this quantity and also a wider range of values may be safely returned.

The quantities actually calculated and returned by this method are controlled by an integer code fFlags. The code is formed by summing contributions for the property and each derivative required using the enumerated constants eCapeCalculationCode (defined in the Thermo version 1.1 IDL) shown in the following table. For example, to calculate log fugacity coefficients and their T-derivatives the fFlags argument would be set to CAPE_LOG_FUGACITY_COEFFICIENTS + CAPE_T_DERIVATIVE.

If CalcAndGetLnPhi is called with fFlags set to CAPE_NO_CALCULATION no property values are returned.

A typical sequence of operations for this method when implemented by a Property Package component would be:

- Check that the phaseLabel specified is valid.

- Check that the moleNumbers array contains the number of values expected (should be consistent with the last call to the SetMaterial method).

- Calculate the requested properties/derivatives at the T/P/composition specified in the argument list.

- Store values for the properties/derivatives in the corresponding arguments.

Note that this calculation can be carried out irrespective of whether the Phase actually exists in the Material Object.

Reference