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//Variable declaration:
//From example 22.9:
t1 = 23.5 //Initial temperature of oil ( C)
t2 = 27 //Final temperature of oil ( C)
T1 = 93 //Water heating temperature of water ( C)
T2 = 88.16 //Minimum temperature of heating water ( C)
U = 34.6 //Overall heat transfer coefficient (W/m^2. C)
Q = 7227.2 //Duty of exchanger (W)
D = 6*0.0254 //Inside diameter of %pipe (m)
l = 6.68 //Previous heat transfer length (m)
//Calculation:
DT1 = T1-t1 //Inlet temperature difference ( C)
DT2 = T2-t2 //Outlet temperature difference ( C)
DTlm = (DT1-DT2)/log(DT1/DT2) //Log mean temperature difference ( C)
A = Q/(U*DTlm) //Required heat transfer area (m^2)
L = A/(%pi*D) //Required heat transfer length (m)
//Result:
printf("The length of the parallel %%pipe heat exchanger is : %.2f ",L)
if L>l then
printf("The tube length would increase slightly.")
elseif L<l then
printf("The tube length would decrease slightly.")
end
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