SET_DIAGRAM_AXIS

Specify an axis variable for a plot or a listing. To be able to plot a diagram, at least two axis variables (X and Y) must be specified. In Console Mode, three axes (X, Y, and Z)  can be specified for a diagram.

The axis variables in the plot can be different from the number of axis used for the mapping.

If you want to plot a phase diagram with tie-lines in the plane after a MAP calculation, then the composition axis must be mole-fraction or weight-fraction, or mole-percent or weight-percent of one specific component. You must not use the stable variable x(comp) or w(comp) even if that is what you used when calculating the diagram, because that only gives one side of the two-phase region. It may be sufficient to indicate that mole-fraction is the same as the stable variable x(*,comp), and weight-fraction is the same as the stable variable w(*,comp).

If you plot a phase diagram where the tie-lines are not in the plane after a MAP calculation, then mole-fraction and x(comp) are identical.

When you plot a property diagram after a STEP calculation and want a composition axis variable, you should normally use x(comp) and not mole-fraction.

The axis must have exactly the same number of columns, or one axis must have one column. In the first case the columns are plotted matching them one by one; in the latter all columns on one axis is plotted against the single column. For example, you can have the temperature on one axis and the amount of each phase on the other. The amount of each phase is the state variable NP(*) in mole fraction or BPW(*) for mass fractions of phases.

Automatic diagram axis:  The POST module can set automatic diagram axis identical to those used in the MAP command.

If the state variable x(comp) is used in a MAP calculation, then mole-fraction of the component is used as diagram axis; if a potential or some other state variables are used, then that is used as a diagram axis.

After a STEP calculation, automatic diagram axis is not set as there is only one axis used in the calculation.

Syntax

set_diagram_axis

 

Axis (X, Y or Z): <Axis name>

Specify which axis (X or Y or Z) to set with a variable.

Prompts

Variable type: <Variable name>

Specify a variable for the chosen axis here.

The valid variables are:

  • TEMPERATURE-CELSIUS as temperature in °C
  • TEMPERATURE as temperature in K
  • PRESSURE as pressure in Pa
  • ACTIVITY for a component
  • LNACTIVITY for a component  [ln(ACR(component)]
  • MOLE-FRACTION  for a component
  • MOLE-PERCENT for a component
  • WEIGHT-FRACTION for a component
  • WEIGHT-PERCENT for a component
  • ENTHALPY as enthalpy in J/mol
  • ENTROPY as entropy in J/mol/K
  • NONE  to clear the axis
  • Any valid state variable including those with wildcards, e.g. NP(*) or x(*,component). Due to the use of wildcard * in such a state variable, the program asks for a column number.
  • Any entered function or variable.
  • Any entered table.
 

If you specify an entered table as the variable, then you are given these prompts:

For component: <Component name>

When an activity, mole or weight fraction or percent of a component shall be plotted, the component name must be supplied here.
 

Column number: <Column number(s)>

Specify the column number(s) in the chosen table that are to be plotted onto the earlier specified axis.  For example:

  • 1 for column 1
  • 2,3 for columns 2 and 3
  • 2,3 >5 for column 2,3 and all columns above column 5
  • * for all columns