Question

for Temp = 1000:10:6000

cp_CO2 = ((2e-18)*Temp.^5) - ((4e-14)*Temp.^4) + ((3e-10)*Temp.^3) - ((8e-07)*Temp.^2) + (0.0013*Temp) + 0.5126;
cp_CO = ((5e-12)*Temp.^3) - ((7e-08)*Temp.^2) + (0.0003*Temp) + 0.9657;
cp_H2O = ((7e-12)*Temp.^3) - ((1e-07)*Temp.^2) + (0.0008*Temp) + 1.6083;
cp_N2 = ((-1e-18)*Temp.^5) + ((2e-14)*Temp.^4) - ((8e-11)*Temp.^3) + ((1e-07)*Temp.^2) + (0.0001*Temp) + 0.9985;

D_H = (y(1)*cp_CO2*44*(25-Temp)) + (y(2)*cp_CO*28*(25-Temp)) + (y(3)*cp_H2O*18*(25-Temp)) + (percent_air*x_final(2)*3.76*28*(25-Temp));

DELTA_H = round(D_H);

if DELTA_H == delta_h
    break
end        

end

The ‘for’ loop in my code is above, the variables delta_h, y and percent_air have been defined and calculated/input earlier. If I work on the loop as a cell and manually increase Temp then the values of D_H etc. all change. But for some reason when I try and execute the loop the ‘if’ statement doesn’t seem to come into effect and the final values where Temp = 6000 are displayed in the workspace instead of the value of Temp where it produces a DELTA_H equal to that of delta_h. It’s the first time I’ve used MATLAB for about 2 years (I’m a 3rd Year Mech Eng student) so please forgive me if it’s a simple error to fix.

Answer 1

If either of the variables are floating-point, doing an exact compare like that is problematic. A <= or >= comparison might work better.