#*-------------------------------------------------------------------
* EMSO Model Library (EML) Copyright (C) 2004 - 2007 ALSOC.
*
* This LIBRARY is free software; you can distribute it and/or modify
* it under the therms of the ALSOC FREE LICENSE as available at
* http://www.enq.ufrgs.br/alsoc.
*
* EMSO Copyright (C) 2004 - 2007 ALSOC, original code
* from http://www.rps.eng.br Copyright (C) 2002-2004.
* All rights reserved.
*
* EMSO is distributed under the therms of the ALSOC LICENSE as
* available at http://www.enq.ufrgs.br/alsoc.
*
*--------------------------------------------------------------------
* Model of valves:
*
*	- Linear
*	- Parabolic
*	- Equal
*	- Quick
*	- valve: a very simple model
*
*--------------------------------------------------------------------
*	- Assumptions
*		* Steady State
*		* Isentalpic
*		* Liquid
*
*---------------------------------------------------------------------
* Author: Estefane Horn, Núbia do Carmo Ferreira
*$Id: valve.mso 109 2007-01-11 22:03:27Z arge $									
*-------------------------------------------------------------------*#

using "streams";
using "pressure_changers/flux_machine_basic";
	

Model valve_basic as flux_machine_basic_TP
	
	PARAMETERS
ext PP   		as CalcObject 	(Brief = "External Physical Properties", File = "vrpp");
ext NComp   	as Integer		(Brief = "Number of chemical components", Lower = 1);
	rho60F 	as dens_mass;

	VARIABLES
	Pdiff 	as press_delta 		(Brief = "Pressure Increase", Unit = "kPa");
	Qv		as flow_vol			(Brief = "Volumetric Flow");
	fc 		as positive			(Brief = "Opening Function");
	cv		as positive			(Brief = "Valve Coefficient", Unit = "m^3/h/kPa^0.5");
	Gf		as positive			(Brief = "Specific Gravity");
	rho 	as dens_mass;	
	vm		as vol_mol			(Brief = "Mixture Molar Volume", Unit = "m^3/kmol");	
	
	SET
	rho60F = 999.2	* "kg/m^3";
	
	EQUATIONS
	"Calculate Outlet Stream Pressure"
	Inlet.P - Outlet.P = Pdiff;
	
	"Enthalpy Balance"
	Outlet.h = Inlet.h;
	
	"Molar Balance"
	Outlet.F = Inlet.F;
	
	"Calculate Outlet Composition"
	Outlet.z = Inlet.z;

	if Pdiff > 0 then
		"Valve Equation - Flow"
		Qv = fc*cv*sqrt(Pdiff/Gf);	
	else
		"Valve Equation - Closed"
		Qv = 0 * "m^3/h";
	end
	
	"Calculate Gf"
	Gf = rho/rho60F;
	
	"Calculate Specific Mass"
	rho = PP.LiquidDensity(Inlet.T,Inlet.P,Inlet.z);
	
	"Calculate Mass Flow"
	Qv = Inlet.F*vm;	
	
	"Calculate Liquid Molar Volume"
	vm = PP.LiquidVolume(Inlet.T,Inlet.P,Inlet.z);
	
end

Model valve_linear as valve_basic

	VARIABLES
	x 		as fraction (Brief = "Opening");

	EQUATIONS
	
	"Opening Equation"
	fc = x;

end

Model valve_parabolic as valve_basic

	PARAMETERS
	n 		as positive (Brief = "Constant", Lower = 1.4, Upper = 2.6);

	VARIABLES
	x 		as fraction (Brief = "Opening");
	
	EQUATIONS
	
	"Opening Equation"
	fc = x^n;

end

Model valve_equal as valve_basic

	PARAMETERS
	a		as Real (Brief = "Constant", Default = 100);

	VARIABLES
	x 		as fraction (Brief = "Opening");

	EQUATIONS
	
	"Opening Equation"
	fc = a^(x-1);

end

Model valve_quick as valve_basic

	PARAMETERS
	a		as positive	(Brief = "Constant", Default = 0.05);
	n		as positive (Brief = "Constant", Default = 5);

	VARIABLES
	x 		as fraction (Brief = "Opening");

	EQUATIONS
	
	"Opening Equation"
	fc = (1-(a*(1-x)-(a-1)*(1-x)^n));

end

#*-------------------------------------------------------------------
* Model of a valve (simplified)
*-------------------------------------------------------------------- 
*
*	Streams:
*		* an  inlet stream
*		* an  outlet stream
*
*	Assumptions:
*		* no flashing liquid in the valve
*		* the flow in the valve is adiabatic
*		* dynamics in the valve are neglected
*		* linear flow type
*
*	Specify:
*		* the inlet stream
*		* one of: plug position (x), outlet temperature (Outlet.T) or 
*								outlet pressure (Outlet.P) 
*	or		
*		* the inlet stream excluding its flow (Inlet.F)
*		* the outlet pressure (Outlet.P) OR outlet flow (Outlet.F)
*		* the plug position (x)
*
*
*----------------------------------------------------------------------
* Author: Paula B. Staudt
*--------------------------------------------------------------------*#
Model valve
	PARAMETERS
ext PP as CalcObject;
ext NComp as Integer;
	
	VARIABLES
in	Inlet as stream;
out	Outlet as stream_therm;
	x as fraction (Brief="Plug Position");
	rho as dens_mass (Brief="Fluid Density", Default=1e3);
	v as vol_mol (Brief="Specific volume", Default=1e3);

	PARAMETERS
	rho_ref as dens_mass (Brief="Reference Density", Default=1e4);
	k as Real (Brief="Valve Constant", Unit="gal/min/psi^0.5");

	EQUATIONS
	"Molar Balance"
	Inlet.F = Outlet.F;
	Inlet.z = Outlet.z;
	
	"Energy Balance"
	Inlet.h = Outlet.h;

	"Vapourisation Fraction"
	Outlet.v = Inlet.v;
	
	"Density"
	rho = Inlet.v*PP.VapourDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
		(1-Inlet.v)*PP.LiquidDensity((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);

	"Volume"
	v = Inlet.v*PP.VapourVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z) +
		(1-Inlet.v)*PP.LiquidVolume((Inlet.T+Outlet.T)/2, (Inlet.P+Outlet.P)/2, Outlet.z);

	if Inlet.P > Outlet.P then
		"Flow"
		Outlet.F * v = k*x*sqrt((Inlet.P - Outlet.P)*rho_ref / rho ) ;
	else
		"Closed"
		Outlet.F = 0 * "kmol/h";
	end
end