Plotting the theoretical maximum possible efficiency of a heat engine

I'm trying to create a temperature vs. efficiency plot using the equation n=1-(Tl/Th) for 3 different Tl values.

clear all

close all

n=0;

Tl1=263;

Tl2=277;

Tl3=291;

for Th=299:.1:316

n=n+1;

TME(n)=1-(Tl1/Th(n));

TME2(n)=1-(Tl2/Th(n));

TME3(n)=1-(Tl3/Th(n));

end

Matlab keeps telling me "index exceeds the number of array elements" and Th only eqauls 299.1 instead of the whole range it is supposed to run through. Can anybody tell me what I'm doing wrong here?

Answer 1

[David Goodmanson]

Hi Aidan,

It's possible to fix up the for loop, but easier and much more in the spirit of Matlab to do this with vectors.

Tl1=263;
Tl2=277;
Tl3=291;
Th=299:.1:316;
TME = 1 - (Tl1./Th);
TME2 = 1 - (Tl2./Th);
TME3 = 1 - (Tl3./Th);

Here the use of ./ means that Th is divided into the numerator on an element-by-element basis, so for e.g. TME you get a vector the same length as Th.