## Figure 4.14 (page 130):

### Reaching steady state in a CSTR.

## Code for Figure 4.14

Text of the GNU GPL.

### main.m

%% Copyright (C) 2001, James B. Rawlings and John G. Ekerdt
%%
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License as
%% published by the Free Software Foundation; either version 2, or (at
%% your option) any later version.
%%
%% This program is distributed in the hope that it will be useful, but
%% WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
%% General Public License for more details.
%%
%% You should have received a copy of the GNU General Public License
%% along with this program; see the file COPYING. If not, write to
%% the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
%% MA 02111-1307, USA.
% This script file solves the multimedia example STR_CSTR
% that illustrates how a STR approaches the steady state and
% becomes a CSTR at sufficiently long time.
% It was developed February 1999, last edited February 8, 1999.
%
% This program is modified here for an example to be inserted into the text
% Last edited by Ekerdt on June 15, 2001
global k theta caf
caf = 2; %gmoles/liter
%cao = input('Enter the initial concentration of A in gmole/liter. ');
%k = input('Enter the rate constant in min^{-1}. ');
%theta = input('Enter the reactor residence time in min. ');
%tf = input('Enter the integration time in min. ');
%set the default values at cao = 0, k = 0.1, theta = 100, tf = 120
%disp('The steady state reactor concentration of A in gmole/liter is ')
cao = 0;
k = 0.1;
theta = 100;
tf=120;
c_ss = caf/(1 + k*theta);
t = [0:.1:tf]';
c_o = [cao];
tff = (10*tf)+1;
opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution] = ode15s (@mat_bal, t, c_o, opts);
answer=[t solution c_ss*ones(tff,1)];
cao = 2.0;
c_o = [cao];
opts = odeset ('AbsTol', sqrt (eps), 'RelTol', sqrt (eps));
[tsolver, solution1] = ode15s (@mat_bal, t, c_o, opts);
answer1=[t solution1 c_ss*ones(tff,1)];
answer = [answer solution1];
plot (answer(:,1), answer(:,[2,4,3]));
title ('Figure 4.14')

### mat_bal.m

function dcdt=mat_bal(t,x)
global k theta caf;
ca=x(1);
dcdt(1)=(1/theta)*(caf-ca)-k*ca;