What is wrong with this code?

I am getting an error message "Array indices must be positive integers or logical values.

Error in take_home_exam_problem2 (line 23)

delT2=delT1*exp(-UA((1/Ch)+(1/Cc)))"

I'm not even sure what an array indices is in this problem, can anyone help me with this?

My code:

start

%user section

%assign our variables

Th1=575;% K inlet hot stream temperature

Tc1=320;% K inlet cold stream temperature

UA=25000;% kJ/(K-hr) heat transfer coefficient

Cph=2.0;% J/(kg-K) heat capacity of hot stream

Cpc=1.1;% J/(kg-K) heat capacity of cold stream

mh=2500;% kg/hr hot stream

mc=800;% kg/hr cold stream

%Main program

%do matlab calculations

delT1=Th1-Tc1

Ch=mh*Cph

Cc=mc*Cpc

delT2=delT1*exp(-UA((1/Ch)+(1/Cc)))

q=UA*((delT2-delT1)/log(delT2/delT1))

end

Answer 1

[Megumi Fukuda]

I assume this is what you meant?

delT2=delT1*exp(-UA*((1/Ch)+(1/Cc)))

See the * between -UA and (.

-UA((1/Ch)+(1/Cc)) means (1/Ch)+(1/Cc)th element of -UA.