ODE45: ODE Error using odearguments must return a column vector

Haseeb (view profile)

on 25 Apr 2019
Latest activity Edited by Stephan

Stephan (view profile)

on 25 Apr 2019
I have the following equation and I want to solve this equation for 10525 timestep (for a day) to get the "Tm" values. However, I am getting error.
This is actually a simple energy balance:
Qstore = Qinj - Qemitted
Hence;
dTm/dt = 1/C_rad * ((Qinj)- (C*(Tm-Tair).^n))
In the above equation all other parameters are constant except ''Qinj''. Qinj is actually the heat injected to the radiator and it has a step change. I am using ODE45 to solve this. The purpose is to observe the change in Tm by changing the Qinj.
So I want to solve the above equation for 10525 different timesteps to get the Tm for each data point. Since this is the continuous data so the initial value for Tm (Tm0) for the next timestep will be equal to the Tm value for the previous timestep (Becuase this is the time-series data).
%% Auusmptions &constant parameters
n = 1.3581 ; % Capacity exponent for the unit
Tsu = 75; % [C] inlet temperature of the radiator
Tair = 21; % [C] Air temperature
C=10;
%% Time series data for Qinj_t
tQinj= (0:0.0022805:24)'; %Because I have data for 24 hourse with 0.0022805 timestep
step = 10524; %
tspan =[0 0.0022805];
t0 = 0; % Start time
t1 = 24; % Final time
t = linspace(t0 , t1 , (step+1));
%% Reading data from Excel sheet
Qinj_t = num(:,4); (10525X1)
Qinj_td = interp1(tQinj, Qinj_t, t, 'linear');
%% ODE expression
Tmo = 20 ; % Initial condition
[t,Tm] = ode45(@(t,Tm) rad_h(t, Tm, tQin, C_rad, Qinj_td, C, Tair, n ),tspan,Tmo);
%% Following function is used:
function dtmdt = rad_h(t, Tm, tQin, C_rad, Qinj_td, C, Tair, n )
end

on 25 Apr 2019

Haseeb

Haseeb (view profile)

on 25 Apr 2019
Hi Stephan, thanks for your response. However, I am still getting the same Error. Error is not in the function but it's in ODE45 expression.
It says:
Error using odearguments (line 93)
must return a column vector.
Stephan

Stephan (view profile)

on 25 Apr 2019
what is it returning? what is the result of:
%% Following function is used:
function dtmdt = rad_h(t, Tm, tQin, C_rad, Qinj_td, C, Tair, n )