Trial and error help is not giving me solution to that (still waiting ....

조회 수: 10 (최근 30일)
Nasir Qazi
Nasir Qazi 2012년 2월 27일
% Calculate Bubble Point and Dew Point SRK-EOS
% P = RT / V - b - alpha*a / V(V-b)
%----------------------------------------------
% liquid phase composition
y = [0.86 0.05 0.05 0.02 0.01 0.0095 0.0005]';
% vapor phase composition
x = [0.45 0.05 0.05 0.03 0.01 0.01 0.4]';
% critical pressure
Pc =[4.5947 4.8711 4.2472 3.6397 3.3688 3.1233 1.965]';
% critical temperature
Tc =[190.7389 305.5111 370.0333 425.3444 469.8889 512.7778 644.4444]';
% Accentric Factor
w = xlsread('myfile.xlsx','Sheet1','E2:E8');
%---------------------------------------------
L = 1;
R = 8.314e-3; % MPa m3 / mole.K
T = 200; % K
Tr = T./Tc; % K
P(L) = 5.0; %MPa
m = 0.480+1.574.*w -0.176.*w.^2;
al=1+ m.*(1-sqrt(Tr)).^2;
a = 0.42748.*(((R.*Tc).^2)./Pc);
b = 0.08664.*(R.*Tc./Pc);
q=0;
while q==0
% Z3 - Z2 + (A-B-B^2)Z-AB=0
% for gas phase
SA = 0;
RR = zeros(7,1);
for i = 1:7
for j = 1:7
SA = SA + y(i).*y(j).*sqrt(a(i).*a(j).*al(i).*al(j));
RR(i) = RR(i) + y(j).*sqrt(a(i).*a(j).*al(i).*al(j));
end
end
SB = sum(y.*b);
% For Liquid Phase
SAA = 0;
MM = zeros(7,1);
for i = 1:7
for j = 1:7
SAA = SAA + x(i).*x(j)*sqrt(a(i).*a(j)*al(i).*al(j));
MM(i) = MM(i) +x(j).*sqrt(a(i).*a(j).*al(i).*al(j));
end
end
SBB = sum(x.*b);
%for Gas Phase
A = SA.*P(L)./(R*T).^2;
B = SB.*P(L)./(R*T);
ZV=roots([1 -1 A-B-B^2 -A*B]);
Zv=max(ZV);
Zvc=isreal(Zv);
if Zvc == false
Zv=abs(Zv);
disp('error 1')
end
%for liquid Phase
AA = (SAA.*P(L))./(R*T).^2;
BB = (SBB.*P(L)./(R*T));
Z=roots([1 -1 AA-BB-BB^2 -AA*BB]);
Zl=min(Z);
Zvl=isreal(Zl);
if Zvl == false
Zl=abs(Zl);
disp('error 2')
end
phiv =exp((b.*(Zv-1)/SB) - log(Zv-B)-(A/B).*((2.*RR/SA)-
(b/SB)).*log(1 + B/Zv));
phil =exp((b.*(Zl-1)./SBB) - log(Zl-BB)-(AA./BB).*((2.*MM/SAA)-
(b./SBB)).*log(1 + BB./Zl));
K = phil./phiv;
RA1= sum(y./K)-1;
if abs(RA1) < 1e-5 && abs((y./K) - x) < 1e-5
break
else
if L==1
L = L+1;
P(L) = 1.01.*P(L-1);
RA1;
else
if L==1
P(L)=P(L-1)-(RA1./(RA1-RA2))*(P(L-1)-P(L-2));
RA2 = RA1;
end
%adjustment
x2 = (1-0.5)*(y./K) + 0.5*x;
x = x2;
end
end
end
disp(P(L));
% I am trying to using trial and error to get the results of P(L) , but my solution is not converging and keep going on. I need to know what can I do to resolve the issue .
Help Please

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