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//Variable declaration:
//From example 18.21:
m = 144206 //Mass flow rate of flue gas (lb/h)
cp = 0.3 //Average heat capacities of the flue gas (Btu/lb F)
T1 = 2050 //Initial temperature of gas ( F)
T2 = 180 //Final temperature of gas ( F)
T3 = 60 //Ambient air temperature ( F)
U = 1.5 //Overall heat transfer coefficient for cooler (Btu/h.ft^2. F)
MW = 28.27 //Molecular weight of gas
R = 379 //Universal gas constant (psia.ft^3/lbmol. R)
v = 60 //Duct or pipe velcity at inlet (2050 F) (ft/s)
pi = %pi
//Calculation:
Q = m*cp*(T1-T2) //Heat duty (Btu/h)
DTlm = ((T1-T3)-(T2-T3))/log((T1-T3)/(T2-T3)) //Log-mean temperature difference ( F)
A1 = round(Q * 10**-5)/10**-5/(U*round(DTlm)) //Radiative surface area (ft^2)
q = m*R*(T1+460)/(T3+460)/MW //Volumetric flow at inlet (ft^3/h)
A2 = q/(v*3600) //Duct area (ft^2)
D = sqrt(A2*4/pi) //Duct diameter (ft)
L = A1/(pi*D) //Length of required heat exchange ducting (ft)
A1 = round(A1*10**-1)/10**-1
//Result:
printf(" The radiative surface area required is : %f ft^2 .",A1)
printf(" The length of required heat exchange ducting is : %.0f ft .",L)
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