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Seek Matlab Help in this problem..by qazinasir
Tags: matlab loop 
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#1
Feb1112, 07:02 PM

P: 5

% Calculate the vapor Pressure of nheptane using SRKEOS
% P = RT / V  b  alpha*a / V(Vb) R = 8.134e3; % MPa m3 / mole.K n = 0; n = n+1; for i=1:5 Pn = 1.6714; %(Assume Pressure)> this needs updating Tr = 0.9; Tc = 540.13; % K Pc = 2.74; % Mpa; T = Tr*Tc; w = 0.350; m = 0.480+1.574*w 0.176*w^2; al=(1+m*(1Tr^0.5))^2; a = 0.42748*(((R*Tc)^2) /Pc); b = 0.08664*(R*Tc / Pc); % Z3  Z2 + (ABB^2)ZAB=0 A = (a*Pn*al)/(R*T)^2; B = (b*Pn)/(R*T); Zv=max(roots([1 1 ABB^2 A*B])); Zl=min(roots([1 1 ABB^2 A*B])); disp(Zv) disp(Zl) phiv(i)=exp((Zv 1)log(Zv B)(A/B) *(log(Zv+B/Zv ))); phil(i)=exp((Zl 1)log(Zl B)(A/B) *(log(Zl+B/Zl ))); Fv=Pn*phiv; Fl=Pn*phil; disp(phiv) disp(phil); disp(Fv); disp(Fl); Error=FlFv; if (Error < 10^4); Pnew=Pn; else P(n+1) =Pn * (phil/phiv); Pn = P(n+1); end end Basically in this code I am trying to assume a pressure 'Pn' to calculate the results which satisfy this relation (Error<10^4) if this satisfy's then our assume pressure is right else if not then we use the relation P(n+1) = Pn*(Phil/Phiv) to caluclate another pressure and update the above pressure (previously assume) with this one. I have error with this and need advice please help 


#2
Feb1112, 08:50 PM

PF Gold
P: 4,287

it's a very small chance people will read that much code and do that much thinking for you. Try to narrow down your specific theoretical or technical problem. Try debugging your code a little bit to chase the source down; you might even solve the problem if you spend some time trying to understand it before you ask.



#3
Feb1112, 08:59 PM

P: 5

Basically in this code I am trying to assume a pressure 'Pn' to calculate the results which satisfy this relation (Error<10^4) if this satisfy's then our assume pressure is right else if not then we use the relation P(n+1) = Pn*(Phil/Phiv) to caluclate another pressure and update the above pressure (previously assume) with this one. but this cycle of Assuming and error checking is perform in a loop (if i am not wrong ) . How to update the previously Assume pressure with new one. thats the main question



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