Matlab help!!! Determine the temperature that corresponds to a specific heat of 1.2 Kj/(Kg * K)

Cp=0.99403 + 1.671*10^-4T + 9.7215*10^-8T^2 - 9.5838*10^-11 T^3 + 1.9520*10^-14 T^4

Determine the temperature that corresponds to a specific heat of 1.2 Kj/(Kg * K)

how do i write the code for this? do I use BISECT METHOD? PLEASE GELP

Yes Bisection method will work, but if you want an even easier method you can simply bring Cp to the right hand side and use roots to solve for T.

Use roots


r = roots(coefficient of your polynomial)

for instance , if y = x^2+2x + 3

then your coefficient will be 1 2 3

same with yours but just remember to bring the 1.2 to the right handside.

so just use r = roots(coefficients of your polynomial)

and MATLAB will return you the roots of your polynomial.

since your function is of the 4th order you should have 4 roots (including imaginary), MATLAB will show all of them so don't worry.


Here's the script you needed:

p = [1.9520*10^(-14) , -9.5838*10^(-11) , 9.7215*10^(-8) , 1.671*10^(-4) , -0.20597] ;

r = roots(p)

display(r)




Re: billrussell42

Cp which has a definition of partial of enthaly/partial of of T (with pressure being constant) actually varies as Temperature changes. Although the differences are small with T is low, Cp changes a lot with respect to T under high T conditions - which is actually the case in this problem. If you plot the function you will see pretty much a straight line between the x-interval of 1000 ~ 6000

"Determine the temperature that corresponds to a specific heat of 1.2 kJ/kgK"

correcting your units, kilo is lower case k, kelvin is upper case K. Joule is J.

Specific heat, ideally, does not change with temperature. Any changes depend on the material. So I don't understand what you are asking.

edit:

U = c·m·∆T
U is energy in Joules to heat the material by ∆T
c is specific heat of the material in J/kg·K
m is mass in kg, ∆T is temperature change in ºC

∆T = U/cm

you have C, but none of the other needed terms to solve for ∆T