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//Variable declaration:
Ts = 200.0+460.0 //Surface temperature of pipe (°R)
Too = 70.0+460.0 //Air temperature (°R)
D = 0.5 //Diameter of pipe (ft)
R = 0.73 //Universal gas constant (ft^3.atm.R^−1.lb.mol^−1)
P = 1.0 //Atmospheric pressure (Pa)
MW = 29.0 //Molecular weight of fluid (mol)
//From Appendix:
mu = 1.28*10**-5 //Absolute viscosity (lb/ft.s)
k = 0.016/3600.0 //Thermal conductivity (Btu/s.ft.°F)
g = 32.174 //Gravitational acceleration (ft/s^2)
//Calculation:
Tav = (Ts+Too)/2 //Average temperature (°R)
v = R*Tav/P //kinematic viscosity (ft^3/lbmol)
p = MW/v //Air density (lb/ft^3)
B = 1.0/Tav //Coefficient of expansion (°R^-1)
DT = Ts-Too //Temperature difference (°R)
Gr = D**3*p**2*g*B*DT/mu**2 //Grashof number
//From equation 10.5:
Cp = 0.25 //Air heat capacity (Btu/lb.°F)
Pr = Cp*mu/k //Prandtl number
GrPr = 10**8.24 //Rayleigh number
//From Holman^(3):
Nu = 10**(1.5) //Nusselt number
h = Nu*(k/D)*3600.0 //Air heat transfer film coefficient (Btu/h.ft.°F)
//Result:
printf("The required air heat transfer film coefficient is : %.2f Btu/h.ft.°F .",h)
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