# MATLAB: Unable to find symbolic solution

MATLAB

%heat conduction with an electrical heat source in copper wireclc; clear;close all;%parametersR = 0.2; % radius in mL = 10; % length of wire in mke = 60000000; % electrical conductivity of copper in S/mk = 401; % thermal conductivity of copper in W/m.KI = 10; % electrical current in AmpSe = (I*I)/ke; % rate of heat production per unit volumeT0 = 20 % Temp in Celcius%Energy Balance in cylindrical shell of thickness del(r) and length L% Doing the energy balance and taking del(r) common and limiting it to 0, a% linear differential equation is formed.% SOLVING DIFFERENTIAL EQUATIONsyms q(r) %q is the heat fluxode45 = diff(r*q,r) == Se*rcond = q(0)~=Inf;%B.C at r = 0,q~=inf is invalid so we took it's value 0 to get similar answerqSol(r)=dsolve(ode45,cond)%Temperature Profilesyms T(r)ode45 = diff(T,r) ==(-Se*r/(2*T))cond = q(R)==T0;TSol(r)=dsolve(ode45,cond)

1.
The condition for the second ode is invalid - i assume you meant:
cond = T(R)==T0;
cond = q(R)==T0;
cond = q(0)~=Inf; %B.C at r = 0,q~=inf is invalid so we took it's value 0 to get similar answer
cond = q(0)==0; %B.C at r = 0,q~=inf is invalid so we took it's value 0 to get similar answer
%heat conduction with an electrical heat source in copper wireclc; clear;close all;%parametersR = 0.2; % radius in mL = 10; % length of wire in mke = 60000000; % electrical conductivity of copper in S/mk = 401; % thermal conductivity of copper in W/m.KI = 10; % electrical current in AmpSe = (I*I)/ke; % rate of heat production per unit volumeT0 = 20 % Temp in Celcius%Energy Balance in cylindrical shell of thickness del(r) and length L% Doing the energy balance and taking del(r) common and limiting it to 0, a% linear differential equation is formed.% SOLVING DIFFERENTIAL EQUATIONsyms q(r) %q is the heat fluxode = diff(r*q,r) == Se*rcond = q(0)==0;%B.C at r = 0,q~=inf is invalid so we took it's value 0 to get similar answerqSol(r)=dsolve(ode,cond)%Temperature Profilesyms T(r)ode = diff(T,r) ==(-Se*r/(2*T))cond = T(R)==T0;TSol(r)=dsolve(ode,cond)