ode45 returns a vector of length 0

Hello everyone,

I am trying to solve a DE with ode45 however, ode45 returns a vector of length 0. Thanks in advance.

%% Clean the Workspace

clc

clear all

%% Variables

Vceo = 102.687; % m3

Cv = 1.48; % kj/kg.C

deltaHcond = 2220; % kj/kg

mCond = 50; % kg/sec

mS = 77.413098; % kg/sec

R = 0.082057338; % atm.l/mol.K

MW = 18; % kg/kmol

cpS = 1.87; % kj/kg.C

t0 = 115; % Initial temp

t_interval = [0 50]; % Time interval

IC = [t0]; % Initial Conditions

alfa = (cpS*mS-deltaHcond*mCond)/(Cv*(mS-mCond));

%% Solve the DE

[t,Tsol] = ode45(@(t,T) cfunc(t,T) , t_interval , IC);

%% Plotting

plot(t,Tsol)

function dTdt = cfunc(t,T)

global alfa

dTdt = (T*alfa-T)/t ;

end

Answer 1

[Askic V]

I see few problems. First have a look at this suggestion:

Coefficient alfa is huge, so change in tempearture is very fast, therefore I use damping coeff 0.0001. I have changed the interval also.

Vceo = 102.687;                 % m3
Cv = 1.48;                      % kj/kg.C
deltaHcond = 2220;              % kj/kg
mCond = 50;                     % kg/sec
mS = 77.413098;                 % kg/sec
R = 0.082057338;                % atm.l/mol.K
MW = 18;                        % kg/kmol
cpS = 1.87;                     % kj/kg.C
t0 = 115;                       % Initial temp
t_interval = [0.1 2];           % Time interval--change
IC = t0;                      % Initial Conditions
alfa = 0.0001* (cpS*mS-deltaHcond*mCond)/(Cv*(mS-mCond));% alfa is too big
% Solve the DE
[t,Tsol] = ode45(@(t,T) cfunc(t,T, alfa) , t_interval , IC);
% Plotting
plot(t,Tsol, '-o')

function dTdt = cfunc(t,T, alfa)
    dTdt =  (T*alfa-T)/t ;
end

[Talha]

Yes, you are right. Alfa being too big escaped my attention. Thank you very much.