TP
Calculation
of pressure  temperature phase diagrams for a fixed composition
Typically
this application might be used for calculating unary phase diagrams as
a function of temperature and pressure.
However the application is not limited to one component systems
although, for multicomponent systems,
some care must then be taken in interpreting the results of the
calculations.
After having loaded the appropriate data into MTDATA and selected the
phase classifications as required, this application is
initiated by entering "tp.mac". Prompts are provided to help the user
to decide what to type in next.
The
macro first provides a list of phases in the system and asks for the
number of the phase which is stable at high temperatures
(either the liquid or the gas phase). However if 0 is entered the
application will not check for consistency.
Then
the macro asks for the minimum pressure, the maximum pressure and the
number of pressure steps to be used for the
calculations. The application allow plots to be displayed either in
terms of a linear scale in terms of pressure or as a log scale. There
is a facility for searching for triple points but this is only possible
when a one component system is under examination.
The
macro also prompts for the maximum number of phase boundaries to be
found. In order to find them all a relatively high number eg 20 should
be entered.
Further
prompts invite entry of the minimum temperature, the maximum
temperature and the tolerance in termperature
to be used for the calculation
(for reasonable accuracy a value of 0.1 should be sufficient). Before
it is possible to do a calculation, it is necessary to set the
composition of the system. For a one component system
this is, of course, straightforward. It is, however, also possible to
carry out calculations on multicomponent systems eg for systems
involving
complex equilibria between a gas phase and various condensed phases.
The
main output from this application is in terms of the calculated diagram
which may be labelled interactively. However, if the
calculations have involved a scan for triple points, tabular output may
also be provided of the form:
Triple point found at
: 0.5140E+10 Pa
1979.7
K
Triple
point found at : 0.1046E+11 Pa
756.6
K
Pressure
: 5.000000E+10 Pa

