View source for Example for Vapour Pressure Data fitting

[[Category:Species]] [[Category:Properties]]
{{Navigation|[[User Guide]]|[[Species Table]]|[[Species Table - Vapour Properties|Vapour Properties]]|altname=Vapour Pressure Data Fitting}}
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==Data Fitting==
We will use Ammonia to demonstrate how to convert data into useable SysCAD formats.  Reference: Perry's Chemical Engineers Handbook, 6th Edition Page 3-46.

{|
|-
|'''Data''':  || Width=50|  ||  '''Equation Fitting'''
|-
|
{| class="wikitable"
|- 
!'''Vapour Pressure (atm)''' !! '''Temperature (C)''' !! Temperature (K)'''
|-
|	1	||	-33.6	||	239.55
|-
|	2	||	-18.7	||	254.45
|-
|	5	||	4.7	||	277.85
|-
|	10	||	25.7	||	298.85
|-
|	20	||	50.1	||	323.25
|-
|	30	||	66.1	||	339.25
|-
|	40	||	78.9	||	352.05
|-
|	50	||	89.3	||	362.45
|-
|	60	||	98.3	||	371.45
|}
|
|Valign=top|
We have to fit the data into this equation format:
*<math>\log(Vp) = a/T + b*\log(T) + cT + d</math>
:Where pressure is in Atmospheres and Temperature is in Kelvin.

Using Data fitting and SysCAD vapour pressure format VpAtm(a,b,c,d), this becomes 
*'''VpAtm(-939.0199537, 3.908218312, -0.002862661, -4.673321372)'''
|}

[[Image:NH3DataFitting.jpg]]

==Entering Vapour Pressure Equation==

*To enter the vapour pressure equation into the SysCAD species database, [[Editing_User_Species_Database#Opening_the_User_Species_Database_Dialog_Window|Edit the User Species Database]]
*Add in physical properties for Species NH3(g) and NH3(l).  For instructions on how to do this, refer to [[Editing_User_Species_Database_#Enter or Change Species data|Enter or Change Species data]].
*Type in the Fitted equation for Ammonia Vapour pressure as per image below:
:[[Image:EnterAmmonia Vapour Pressure.png]]

Related Topics
* [[Editing User Species Database]]
* [[Species Table - Vapour Properties#Vapour Pressure (Vp)|Vapour Pressure Data in Species Database]]

==Adding Species to the Configuration File==

*With the SysCAD Project closed, choose menu command Edit|Project Configuration.
*Follow instructions given in '''[[Project Configuration (cfg File)]]''' to add NH3(g) and NH3(l) to the project configuration file.
*When this is done, open the SysCAD project and create the SysCAD project as required.

==Selecting Flash Component==

*Any unit operation containing a VLEquilibrium sub model is capable of flash calculation.  Here we are using the Flash Tank as an example.
:[[Image:NH3VLE.png]]
*On the First Tab Page of the Flash Tank, select the Flash method as required.
*On the VLE Tab Page, select Component to be NH3
*When the project is solved, SysCAD will report the results under the [[Vapour Liquid Equilibrium (VLE)#Data Sections|Results Section]] on the VLE tab page.  Checking the results with what we have provided, for Flash Temperature of 4.7°C we had a pressure of 5 atmosphere absolute, which matches the data provided.