Matlab mathematival modeling problem chemical eng

function [f] = acidpretreat(t,x,)

%Components

xyl= x(1);

arab= x(2);

acet= x(3);

cel= x(4);

Xylo= x(5);

Arabi= x(6);

Acetic= x(7);

Furf= x(8);

%---------------------------------------------------------------------

%Data

R=8.314;

HA=0.8;

T=400; % kelvin

k10=2.37; k20=2.17; k1ac=2.37; k30=2.37; %min^-1%

n1=1.51; n2=0.29;n1ac=0.604;n3=1.359;

E1=83.3*1e3;E2=143.5*1e3;E1ac=83.3*1e3;E3=94.962*1e3; %J/mol

Bmax=120;

Xc=0.40680*1e-2; Xh1=0.22136*1e-2; Xh2=0.03786*1e-2;Xh3=0.03330*1e-2; %wt

xylmax=Xh1*Bmax; arabmax=Xh2*Bmax;acetmax=Xh3*Bmax;celmax=Xc*Bmax; %g/L

%---------------------------------------------------------------------

% initial concentrations

xyl_zero=Xh1*x;

arab_zero=Xh2*x;

acet_zero=Xh3*x;

cel_zero=Xc*x;

Xylo_zero=0;

Arabi_zero=0;

Acetic_zero=0;

Furf_zero=0;

% Effective coefficients

ef1=1/(1+(xyl/xylmax)^20);

ef2=1/(1+(arab/arabmax)^20);

ef3=1/(1+(acet/acetmax)^20);

ef4=1/(1+(cel/celmax)^20);

% Effective concentrations

xylef=0.95*ef1*xyl+((1-ef1)*xylmax);

arabef=0.95*ef2*arab+((1-ef2)*arabmax);

acetef=0.95*ef3*acet+((1-ef3)*acetmax);

celef=0.95*ef4*cel+((1-ef4)*celmax);

% K min^(-1)

K1=(k10*1e10)*(HA^n1)*exp(-E1/(R*T));

K2=(k20*1e15)*(HA^n2)*exp(-E2/R*T);

K3=(k30*1e10)*(HA^n3)*exp(-E3/R*T) ;

K1ac=k1ac*(10^10)*(HA^n1ac)*((xyl*((xyl_zero)^-1)))^2*exp(-E1ac/R*T);

% Rates

rxyl=-K1*xylef;

rarab=-K1*arabef;

racet=-K1ac*acetef;

rcel=-K3*celef;

rXylo=K1*xylef-K2*Xylo;

rArabi=K1*arabef-K2*Arabi;

rAcetic=K1ac*acetef;

rglu=K3*celef;

% Mass balance

dxyldt=rxyl;

darabdt=rarab;

4*((dacetdt)^2)+10*dacetdt = racet;

dceldt=rcel;

dXylodt=rXylo;

dArabidt=rArabi;

4*((dAceticdt)^2)+10*dAceticdt = rAcetic;

dgludt=rglu;

dfurfdt=K2*(Xylo+Arabi);

%-----------------------------------

f =[ dxyldt; darabdt; dacetdt; dceldt; dXylodt; dArabidt; dAceticdt;dgludt;dfurfdt];

end

comand window

[t, x] = ode23s(@acidpretreat, [0 240], [20])

Error using feval

Error: File: acidpretreat.m Line: 59 Column: 28

The expression to the left of the equals sign is not a valid target for an assignment.

Error in odearguments (line 87)

f0 = feval(ode,t0,y0,args{:}); % ODE15I sets args{1} to yp0.

Error in ode23s (line 119)

[neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

Answer 1

[Bjorn Gustavsson]

You have at least a couple of syntax errors in your code, namely the lines:

4*((dacetdt)^2)+10*dacetdt = racet;
4*((dAceticdt)^2)+10*dAceticdt = rAcetic;

If you want to assign values to racet and rAcetic you have to put those variables on the LHS of the assignment-=.

In addition I strongly suggest you make use of the code-markup capacility of the answers editor - use the buttons over the "CODE" tab-label.

HTH