Getting Error: Warning: Unable to find explicit solution.

Trying to solve for ignition temperature of different materials using equation attached. This is my code:

%G=30,000 W/m^2

%T0=298K

%E=.9

%h= 15 W/m^2/K

%%PMMA

%K*rho*c=10,000,000

%tp=653K

syms t_ign;

eqn = 298+((.9*30000)/15)*(1-exp(225*t_ign/10000000))*erfc(((225*t_ign)/10000000)^(1/2))==653 ;

sol1 = solve(eqn,t_ign);

Anyone know what is wrong??

Answer 1

[madhan ravi]

There is nothing wrong in your code but Matlab is not able to solve the above equation , tried it in Wolfram wasn't able to solve either

[Ella Meredith]

Is there any way to solve an equation like that in matlab?

[madhan ravi]

I think it’s pretty hard to get through because there’s erfi constant in the equation

[Walter Roberson]

As a general rule: if you are using solve() with an expression that includes floating point numbers then you are making a mistake. solve() is for finding exact closed form solutions if possible, but any time you have a floating point constant, that is an indication that your inputs are not exact and therefore it is meaningless to get an exact solution.

If you are looking for approximate solutions then vpasolve.

[madhan ravi]

Thank you sir Walter for briefing the issue much appreciated