How I solve a nonlinear equation with matlab function block?

Here is my blocks and 'Generator' matlab function block contents is

function StrongSolution  = Generator(HotWater,WeakSolution, CoolingCapacity)
P = 4.82 % [kPa], Absolute Pressure
Cp = 4.2 % kJ/kgK

T_in = HotWater(1) % Celious
T_out = HotWater(2) % Celious
m_w = HotWater(3) % kg/s

T_w = WeakSolution(1) % Celious
x_w = WeakSolution(2)/100 % Nondimension
m_w = WeakSolution(3) * CoolingCapacity % kg/s
h_w = WeakSolution(4) % kJ/kg

WasteHeat = m_w*Cp*(T_in - T_out) % kJ

Tacc = 88
UA_G = 16.6*CoolingCapacity/(0.0986*exp(0.0254*Tacc))

T_lmG = WasteHeat/UA_G

fun = @(T_s) T_lmG - ((T_out-T_w)-(T_in-T_s))/log((T_out-T_w)/(T_in-T_s))
T_s = fzero(fun,[55 100])

StrongSolution = T_s

end

And I upload my problem.

I wanted to know 'T_s'. So I used 'fzero' function in a Matlab function block.

But the error was occured.

How can I solve the problem?

[MinWoo Nam]

the version is R2017a.

Answer 1

[Ameer Hamza]

The current problem should be fixed by putting a semicolon (;) at the end of line 21 of your code

fun = @(T_s) T_lmG - ((T_out-T_w)-(T_in-T_s))/log((T_out-T_w)/(T_in-T_s));

But then another error occurs, which is unrelated to the current error. It is caused by negative values inside the log() during the execution of fzero(). You may need to adjust the interval for the solution or input parameters to see how you can avoid creating negative input to log() function.