#*-------------------------------------------------------------------
* Model of a dynamic flash
*-------------------------------------------------------------------- 
* 	- Streams
*		* a liquid outlet stream
*		* a vapour outlet stream
*		* a feed stream
*
*	- Assumptions
*		* both phases are perfectly mixed
*
*	- Specify:
*		* the feed stream;
*		* the outlet flows: OutletV.F and OutletL.F
*
*	- Initial:
*		* the flash initial temperature (OutletL.T)
*		* the flash initial liquid level (Ll)
*		* (NoComps - 1) OutletL (OR OutletV) compositions
*----------------------------------------------------------------------
* Author: Paula B. Staudt
* $Id: flash.mso 55 2006-11-12 20:27:35Z arge $
*--------------------------------------------------------------------*#

using "streams";

Model flash
	PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
	V as volume(Brief="Total Volume of the flash");
	Mw(NComp) as molweight;
	Across as area  (Brief="Flash Cross section area");
	
	SET
	Mw=PP.MolecularWeight();
	
	VARIABLES
in	Inlet as stream; #(Brief="Feed Stream");
out	OutletL as stream_therm; #(Brief="Liquid outlet stream");
out	OutletV as stream_therm; #(Brief="Vapour outlet stream");
in	Q as heat_rate (Brief="Rate of heat supply"); 

	M(NComp) as mol (Brief="Molar Holdup in the tray");
	ML as mol (Brief="Molar liquid holdup");
	MV as mol (Brief="Molar vapour holdup");
	E as energy (Brief="Total Energy Holdup on tray");
	vL as volume_mol (Brief="Liquid Molar Volume");
	vV as volume_mol (Brief="Vapour Molar volume");
	Level as length (Brief="liquid height");
	
	EQUATIONS
	"Component Molar Balance"
	diff(M)=Inlet.F*Inlet.z - OutletL.F*OutletL.z - OutletV.F*OutletV.z;
	
	"Energy Balance"
	diff(E) = Inlet.F*Inlet.h - OutletL.F*OutletL.h - OutletV.F*OutletV.h + Q;
	
	"Molar Holdup"
	M = ML*OutletL.z + MV*OutletV.z; 
	
	"Energy Holdup"
	E = ML*OutletL.h + MV*OutletV.h - OutletL.P*V;
	
	"Mol fraction normalisation"
	sum(OutletL.z)=1.0;
	"Mol fraction normalisation"
	sum(OutletL.z)=sum(OutletV.z);
	
	"Liquid Volume"
	vL = PP.LiquidVolume(OutletL.T, OutletL.P, OutletL.z);
	"Vapour Volume"
	vV = PP.VapourVolume(OutletV.T, OutletV.P, OutletV.z);
	
	"Chemical Equilibrium"
	PP.LiquidFugacityCoefficient(OutletL.T, OutletL.P, OutletL.z)*OutletL.z = 
		PP.VapourFugacityCoefficient(OutletV.T, OutletV.P, OutletV.z)*OutletV.z;
	
	"Thermal Equilibrium"
	OutletV.T = OutletL.T;
	
	"Mechanical Equilibrium"
	OutletV.P = OutletL.P;
	
	"Geometry Constraint"
	V = ML* vL + MV*vV;
	"Liquid Level"
	ML* vL = Across * Level;
	
	"vaporization fraction "
	OutletV.v = 1.0;
	"vaporization fraction "
	OutletL.v = 0.0;

end

#*----------------------------------------------------------------------
* Model of a  Steady State flash
*---------------------------------------------------------------------*# 
Model flash_Steady
	PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
	
	VARIABLES
in	Inlet as stream; #(Brief="Feed Stream");
out	OutletL as stream_therm; #(Brief="Liquid outlet stream");
out	OutletV as stream_therm; #(Brief="Vapour outlet stream");
in	Q as heat_rate (Brief="Rate of heat supply"); 
	vfrac as fraction;

	EQUATIONS
	"The flash calculation"
	[vfrac, OutletL.z, OutletV.z] = PP.Flash(OutletV.T, OutletV.P, Inlet.z);
	
	"Global Molar Balance"
	Inlet.F = OutletV.F + OutletL.F;
	OutletV.F = Inlet.F * vfrac;
		
	"Energy Balance"
	Inlet.F*Inlet.h  + Q = OutletL.F*OutletL.h + OutletV.F*OutletV.h;
	
	"Thermal Equilibrium"
	OutletV.T = OutletL.T;
	
	"Mechanical Equilibrium"
	OutletV.P = OutletL.P;
	
	"vaporization fraction "
	OutletV.v = 1.0;
	"vaporization fraction "
	OutletL.v = 0.0;
end