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//Variable declaration:
D = 0.0833 //Diameter of tube (ft)
L = 2.0 //Length of tube (ft)
h = 2.8 //Heat transfer coefficient (Btu/h.ft^2.°F)
Ta1 = 1500.0+460.0 //Temperature of hot air in furnace (°R)
Ta2 = 1350.0+460.0 //Temperature of hot air in the furnace brick walls (°R)
Tt = 600.0+460.0 //Surface temperature of tube (°R)
E = 0.6 //Surface emissivity of tube
s = 0.1713*10**-8 //Stefan-Boltzmann constant
pi = %pi
//Calculation:
//Case 1:
A = pi*D*L //Area of tube (ft^2)
Qc = round(h*A*(Ta1-Tt)*10**-1)/10**-1 //Convection heat transfer from air to tube (Btu/h)
Qr = round(E*s*A*(Ta2**4-Tt**4)*10**-2)/10**-2 //Radiation feat transfer from wall to tube (Btu/h)
Q = Qr+Qc //Total heat transfer (Btu/h)
//Case 2:
Qp = Qr/Q*100 //Radiation percent
//Case 3:
hr = Qr/(A*(Ta2-Tt)) //Radiation heat transfer coefficient (Btu/h.ft^2.°F)
//Case 4:
T = Ta2-Tt //Temperature difference (°F)
//Result:
printf("1. The convective heat transferred to the metal tube is : %f Btu/h.",Qc)
printf(" The radiative heat transferred to the metal tube is : %f Btu/h.",Qr)
printf(" The total heat transferred to the metal tube is : %f Btu/h .",Q)
printf("2. The percent of total heat transferred by radiation is : %.1f %%.",Qp)
printf("3. The radiation heat transfer coefficient is : %.1f Btu/h.ft^2.°F.",hr)
if (T > 200) then
printf("4. The use of the approximation Equation (11.30), hr = 4EsTav^3, is not appropriate.")
elseif (T < 200) then
printf("4. The use of the approximation Equation (11.30), hr = 4EsTav^3, is appropriate.")
end
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