wtp_vp.m

WTP主要是calculate basic thermodynamic properties for water

function [outstruct] = WTP_vP(v,P)
% -----------------------------------------------------------------
% function [outstruct] = WTP_PT(v,P)
%
% written by Francois Brissette in April 2005, 
% based on original work by Philippe Daigle, May 2002
%
% calculates basic thermodynamic properties for water, 
% follows IAPWS-97 formulation, Region 3 and 5 have NOT
% been implemented. This has been programmed for use by
% engineering students and regions 1, 2 and 4 cover the
% useful range.  See www.iapws.org for the paper describing
% the formulation in details
%
% you are free to use, modify and distribute the functions as long
% as authorship is properly acknowledged
%
% INPUTS:
% v specific volume in m3/kg
% P in kPa
%
% OUPUT:
% outstruct - a structure of strings that contains the following:
% pressure in kPa, temperature in C, specific volume in m3/kg,
% internal energy in kJ/kg, enthalpy in kJ/kg, entropy in kJ/kg/K
% as well as two messages giving info such as the state or error message
% in the case of incorrect data entry
%
% NB: This function does not use the reverse equations of the formulation
% but iterated using the direct equations for P and T.  Results will
% be identical up to the tolerance defined in the function.  Default is
% 10^-7
%


Pg=0; Tg=0; vg=0; ug=0; sg=0; hg=0;
Pf=0; Tf=0; vf=0; uf=0; sf=0; hf=0;
info_msg='';
info_msg_2='';

CK=273.15;
P=P/1000;  % kPa to MPa

% first step - establish the thermodynamic state by supposing first that
% consitions are saturated
%

T=Pressure_State(P);

if P <= 16.53
    [Pg,Tg,vg,ug,sg,hg] = property_PT(P,T,2); % Region 4 for steam
    [Pf,Tf,vf,uf,sf,hf] = property_PT(P,T,1); % Region 1 for supercooled liquid
    if v < vg & v > vf
        state=3;    % saturated
    end
    
    if v < vf
        [Pf,Tf,v_test,uf,sf,hf] = property_PT(P,0.0001,1); 
        state=1;   % supercooled liquid
    end
    
    if v > vg
        state=2;   % superheated vapour
    end
end

if P > 16.53  % either it's condensed liquid if T < 350, superheated vapour if in region 2, or it is out of range (region 3)
    n3=.0010192970039326;
    n4=572.54459862746;
    n5=13.918839778870;
    Ttest=n4+sqrt((P-n5)/n3);
  
    [Pg,Tg,v_test2,ug,sg,hg] = property_PT(P,350+CK,1);  % verify the volume for condensed liquid at 350
    if v<v_test2     % we are in region 1
        state=1;
    end
    
    if Ttest>863.15     % T at which P = 100MPa along the line separating regions 2 and 3
        Ttest=863.15;
    end
    [Pg,Tg,vg,ug,sg,hg] = property_PT(P,Ttest,2); % Region 2
    
    if v > vg
        state=2;   % superheated vapour
    end
    
    if v < vg & v > v_test2
        state=4;    % out of range
    end
    
    if P > 100
        state=4;    % outside of range
    end
end

[Pg,Tg,v_test3,ug,sg,hg] = property_PT(P,800+CK,2); % Region 2

if v > v_test3
    state=4;    
end

if T < 273.15001   % basic quality control
    state=5;
end

if v < 0.00001   % basic quality control
    state=6;
end
    

if state==1 %  Liquide comprim